Prophylactic or therapeutic agent for dementia

Abstract

The present invention provides: a prophylactic or therapeutic agent for dementia; an agent for enhancing memory and / or cognitive function; an agent for inhibiting the synaptic loss action of amyloid beta protein; an agent for inhibiting amyloid beta protein production; and an agent for promoting amyloid beta protein clearance, each of which contains, as an active ingredient, a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or the C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or the C-terminal region fragment thereof.

Description

Agent for preventing or treating dementia The present invention relates to an agent for preventing or treating dementia and an agent for enhancing memory and / or cognitive function using the Crtac1B protein or a C-terminal region fragment thereof. In healthy individuals, it is known that with aging, slow inflammatory effects and brain atrophy occur, gradually weakening the neural plasticity responsible for memory and learning, and as a result, symptoms such as senile amnesia may appear. On the other hand, in dementia represented by Alzheimer's disease, it is known that various higher brain functions including memory and learning are impaired by nerve cell death induced by the accumulation of amyloid-β (Aβ) protein and phosphorylated tau. Since the former is not a pathological condition, there is no therapeutic drug for it, and various health methods and functional foods have been devised, but their effects have not been academically recognized. In the latter case, drugs that increase the amount of neurotransmitter (acetylcholine) in synapses, represented by Aricept, by inhibiting its decomposition, and drugs that defend against cell death caused by excessive excitation of nerve cells by NMDA receptor antagonists such as memantine have been applied as limited symptomatic therapies, but their usefulness has not been widely recognized. Furthermore, many inhibitors against two enzymes responsible for Aβ production (BACE1, γ-secretase; which cleave amyloid precursor protein (APP) to produce Aβ) have been developed, but they cannot inhibit the accumulation of Aβ, and research targeting these enzymes has declined. Recently, lecanemab and donanemab have been developed and approved as antibody drugs aiming at fundamental improvement of Aβ pathology. Although the usefulness of antibodies against Aβ was proposed as early as four and a half centuries ago (Non-Patent Document 1), the development of Aβ vaccine therapy was aborted due to deaths (deaths due to severe encephalitis) in Aβ vaccine therapy. However, as a result of long-term research and development with the progress of the development of anti-Aβ antibody drugs, lecanemab has emerged. However, although these antibody drugs have been confirmed to suppress the decline of cognitive function in dementia patients, their effects are not sufficient, and the effects are limited in that it is difficult to improve the already declined cognitive function if the treatment intervention time is late. The efficacy and effect of lecanemab approved in Japan is limited to mild cases of "suppressing the progression of mild cognitive impairment and mild dementia due to Alzheimer's disease" (Non-Patent Document 2). Also in the United States, the clinical trial of lecanemab is being conducted for patients with early Alzheimer's disease (Non-Patent Documents 3 and 4), and administration is to be started from mild patients. In addition, antibody drugs such as lecanemab require continuous administration over a long period of time, and there are concerns about serious side effects such as cerebral edema at present, and there are numerous unsolved problems. In addition, as a countermeasure against tau pathology, intrathecal administration of antisense oligos as a nucleic acid drug that reduces tau has been attempted (Non-Patent Document 5), and antibody drugs that prevent tau existing intracellularly from being secreted extracellularly and spreading in the brain are also being studied. Although these drugs are the world's most advanced technologies for dementia, many years are still required for clinical application. Thus, although pharmaceutical development targeting Aβ and tau is progressing, as described above, the mainstream of development is an approach using antibodies against those target toxic substances or an approach aiming at reducing expression by nucleic acid drugs. The control method by endogenous substances is undeveloped. The group of the inventors of the present application has previously discovered an endogenous protein that forms a neural circuit responsible for olfactory information and named it LOTUS (Lateral Olfactory Tract Usher Substance) (Non-Patent Document 3). LOTUS is Crtac1B, which is a splicing variant of Crtac1 known as a marker for chondrocyte progenitor cells, and is mainly expressed in the nervous system. LOTUS / Crtac1B binds to Nogo receptor type 1 (NgR1) and PirB, which are receptors that function in the nerve regeneration inhibitory pathway, blocks ligand binding, and promotes nerve regeneration by inhibiting signal transduction by these receptors (Non-Patent Documents 6 and 7). Regarding the association between LOTUS / Crtac1B and neurodegenerative diseases of the brain, it has been reported that the synaptic density decreases in cultured hippocampal neurons lacking LOTUS / Crtac1B, and that social recognition memory and spatial-dependent memory in mice are impaired due to the deficiency of LOTUS / Crtac1B (Non-Patent Document 8), but the effects of replenishing LOTUS / Crtac1B on the cognitive and memory functions of the living body have not been reported. The effects of LOTUS / Crtac1B on the phagocytosis of accumulated Aβ and Aβ production are also completely unknown. Schenk D. et al., Nature 400: 173-177, 1999. Package Insert for the Lecanemab Preparation "Lecanbi" for Intravenous Drip Infusion of 200 mg (Approval Number 30500AMX00272000) and Intravenous Drip Infusion of 500 mg (Approval Number 30500AMX00273000), created in September 2023 (Version 1) ClinicalTrials.gov Identifier: NCT03887455, "A Study to Confirm Safety and Efficacy of Lecanemab in Participants With Early Alzheimer's Disease (Clarity AD)." [https: / / www.clinicaltrials.gov / study / NCT03887455] C.H. van Dyck et al. N Engl J Med 2023; 388:9-21. Mummery C. et al., Nat. Med. 29:1437-1447, 2023. Sato Y et al., Science 2011; 333: 769-773. Kurihara Y, et al., J Neurochem. 2020;155(3):285-99. Nishida et al., Sci Rep. 2021;11(1):5085. An object of the present invention is to provide a novel means effective for preventing dementia such as Alzheimer's disease and memory and cognitive function decline due to aging, and improving memory and cognitive function. As a result of intensive research, the inventors of the present application have found that LOTUS / Crtac1B binds to the enzyme BACE1 responsible for Aβ production, suppresses the activity of BACE1, inhibits APP cleavage by BACE1 (inhibition of Aβ production), improves the survival rate of microglia, and promotes the phagocytosis of Aβ by microglia (promotion of Aβ clearance). It was also found that LOTUS supplementation by overexpressing LOTUS inhibits the binding of Aβ and PirB and suppresses the decrease in spine density caused by Aβ (suppression of synapse loss caused by Aβ). Furthermore, LOTUS supplementation by overexpressing LOTUS increases the spine density and synapse density of mouse hippocampal neurons, enhances social cognitive memory and spatial learning memory in young and old brains (enhancement of cognitive and memory functions in non-Alzheimer's brains), and improves memory impairment in Alzheimer's disease model mice (enhancement of cognitive and memory functions in Alzheimer's disease), thus completing the present invention. That is, the present invention is an invention for treating dementia, preventing or improving the decline of cognitive and memory functions due to aging, etc., by supplementing a patient with the LOTUS / Crtac1B protein or a C-terminal region fragment of LOTUS / Crtac1B, which is a functional domain exhibiting an antagonistic effect against NgR1, and includes the following aspects. [1] A prophylactic or therapeutic agent for dementia, comprising as an active ingredient the Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof. [2] The therapeutic agent according to [1], wherein the dementia is Alzheimer's type dementia. [3] An enhancer of memory and / or cognitive function, comprising as an active ingredient the Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof. [4] An agent for inhibiting the synapse loss effect of amyloid beta protein, which contains as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof. [5] An amyloid beta protein production inhibitor, which contains as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof. [6] An amyloid beta protein clearance promoter, which contains as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof. [7] The Crtac1B protein is a polypeptide having an amino acid sequence with 95% or more identity to the amino acid sequence shown in SEQ ID NO: 2, and the C-terminal region fragment is (i) A Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 7, (ii) A Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 9, (iii) A Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 11, or (iv) A polypeptide having 90% or more sequence identity with the protein fragments of (i) to (iii) The agent according to any one of [1] to [6]. [8] The agent according to any one of [1] to [7], wherein the cell expressing Crtac1B protein or a C-terminal region fragment thereof is a neural stem / progenitor cell, an excitatory neuron or an oligodendrocyte progenitor cell. [9] A method for treating dementia, comprising administering to a dementia patient a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

[0010] The method according to [9], wherein the dementia is Alzheimer's dementia.

[0011] A method for enhancing memory and / or cognitive function, comprising administering to a patient in need of enhanced memory and / or cognitive function a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

[0012] The method according to [6], wherein the patient is an elderly person whose memory and / or cognitive function has declined due to aging, a patient having amnesia or forgetfulness, a patient with mild cognitive impairment, or a dementia patient.

[0013] A method for inhibiting the synapse-eliminating action of amyloid-beta protein in a patient, comprising administering to the patient a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

[0014] The method according to

[12] , wherein the patient is a dementia patient or a patient having accumulation of Aβ protein in the brain.

[0015] The method according to

[15] , wherein the patient is an Alzheimer's dementia patient.

[0016] A method for inhibiting the production of amyloid-beta protein in a patient, comprising administering to the patient a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

[0017] The method according to

[0016] , wherein the patient is a patient with dementia or a patient having an accumulation of Aβ protein in the brain.

[0018] The method according to

[0017] , wherein the patient with dementia is a patient with Alzheimer's disease.

[0019] A method for promoting clearance of amyloid beta protein in a patient, comprising administering to the patient a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

[0020] The method according to

[0019] , wherein the patient is a patient with dementia or a patient having an accumulation of Aβ protein in the brain.

[0021] The method according to

[0020] , wherein the patient with dementia is a patient with Alzheimer's disease.

[0022] The Crtac1B protein is a polypeptide having an amino acid sequence with 95% or more identity to the amino acid sequence shown in SEQ ID NO: 2, and the C-terminal region fragment is (i) A Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 7, (ii) A Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 9, (iii) A Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 11, or (iv) A polypeptide having 90% or more sequence identity with the protein fragments of (i) to (iii) The method according to any one of [9] to

[0021] .

[0023] The method according to any one of [9] to

[0022] , wherein the cell expressing the Crtac1B protein or a C-terminal region fragment thereof is a neural stem / progenitor cell, an excitatory neuron, or an oligodendrocyte progenitor cell. Since LOTUS / Crtac1B has the effects of reducing the accumulation of Aβ in the brain, inhibiting the production of Aβ, and suppressing the synaptic reduction effect of Aβ itself, the LOTUS / Crtac1B replacement therapy of the present invention is an epoch-making treatment method that can comprehensively control the effects of Aβ. In addition to the effect of blocking the environment that inhibits nerve regeneration by blocking the receptor on which the nerve regeneration inhibitor acts, LOTUS / Crtac1B also has the effect of promoting neurite outgrowth and synapse formation. Therefore, it is expected to act on the remaining neurons not only for mild cognitive impairment or dementia but also for moderate or more severe cognitive impairment or dementia to improve the symptoms. Not only Alzheimer's type dementia caused by the accumulation of Aβ, but also the decline of memory and cognitive function due to aging can be improved by LOTUS / Crtac1B replacement. Furthermore, it has been confirmed that the memory function is improved by LOTUS / Crtac1B replacement even in healthy young mice. Therefore, it can be effective for various dementias and cognitive impairments including Alzheimer's type dementia, as well as amnesia and amnestic disorders. Since LOTUS / Crtac1B is an endogenous substance, unlike existing antibody drugs for Alzheimer's disease, the risk of side effects is very low. In fact, LOTUS / Crtac1B is abundantly expressed in the brains of healthy people, and no harmful events have been observed even in animal experiments with overexpression of LOTUS. Membrane-bound LOTUS (SBP-FLAG-LOTUS) and human BACE1 were co-expressed in cells, and a pull-down assay was performed using Streptavidin agarose resin. Soluble LOTUS (SBP-hFc-LOTUS) or SBP-hFc (Tag) was added to cells overexpressing human BACE1 at a final concentration of 1 μM, and a pull-down assay was performed using Streptavidin agarose resin. Soluble LOTUS (SBP-hFc-LOTUS) or SBP-hFc (Tag) was added to the cell lysate of cells overexpressing human BACE1 at a final concentration of 1 μM, and a pull-down assay was performed using Streptavidin agarose resin. BACE1 in the lysate of COS-7 cells co-expressing human LOTUS, human BACE1, and human APP plasmid was detected by Western blot. Quantitative results of BACE1 expression levels in Figure 2A. The BACE1 expression level was corrected with β-Actin and normalized with the quantitative value of the control (mock) (n = 5, by unpaired t-test). β-CTF in the lysate of COS-7 cells co-expressing human LOTUS, human BACE1, and human APP plasmid was detected by Western blot. Quantitative results of β-CTF expression levels in Figure 2C. The β-CTF expression level was corrected with the APP-full length expression level and normalized with the quantitative value of the control (mock) (n = 5, *p < 0.05, by unpaired t-test). sAPPβ in the culture supernatant of COS-7 cells co-expressing human LOTUS, human BACE1, and human APP plasmid was detected by Western blot. Quantitative results of sAPPβ in Figure 2E (n = 5, *p < 0.05, by unpaired t-test). Inhibition of BACE1 activity by LOTUS. 2.5 μM SBP-hFc-LOTUS or 2.5 μM SBP-hFc (Tag), 2 mM biotin / PBS (Vehicle), and 5 μM BACE1 inhibitor (inhibitor) were each reacted with BACE1 recombinant protein.Subsequently, an APP (FRET peptide) with the Swedish mutation was added, and the fluorescence intensity at 520 nm after 30 minutes of reaction was measured. The ratio of each group to the Vehicle control was determined. (n = 3, **p < 0.01, by One-Way ANOVA Dunnett) The viability of primary microglial cells 24 hours after adding sLOTUS. Represented as the mean ± SEM of 5 trials. P* < 0.05, P** < 0.01, n = 5, statistics by one-way ANOVA Tukey. The ratio of each treatment group to the Tag was determined. The viability of primary microglial cells 24 hours after adding sLOTUS and Aβ simultaneously. Represented as the mean ± SEM of 5 trials. P* < 0.05, P** < 0.01, n = 5, statistics by one-way ANOVA Tukey. The ratio of each treatment group to Aβ + Tag was determined. The amount of LDH production from primary microglial cultures 24 hours after adding sLOTUS. Represented as the mean ± SEM of 5 trials. P* < 0.05, P** < 0.01, n = 5, statistics by one-way ANOVA Tukey. The ratio of each treatment group to the Tag was determined. Represented as the mean ± SEM of 5 trials. P* < 0.05, P** < 0.01, n = 5, statistics by one-way ANOVA Tukey. The ratio of each treatment group to Aβ + Tag was determined. Primary microglial cells to which sLOTUS and Aβ-pHrodo were added simultaneously were fixed after 4 hours and imaged with a fluorescence microscope, and quantification was performed using ImageJ. The number of phagocytosed Aβ-pHrodo and DAPI was counted, and Aβ-pHrodo was divided by DAPI to yield the result. The phagocytosis ratio of each treatment group to the phagocytosis level of Tag in BV-2 cells was determined. Represented as the mean ± SEM of 5 trials. P* < 0.05, P** < 0.01, n = 5, statistics by one-way ANOVA Tukey LOTUS inhibits the binding of Aβ and PirB. a. Staining image of the Aβ and PirB binding experiment. Cells to which Aβ is bound are colored dark blue (left panel). Scale bar is 100 μm.b. Expression levels of PirB in each group (n.s.: not significant, n = 4, One-way ANOVA, Tukey post hoc test). c. Graph quantifying Aβ binding in each group (*: p < 0.05, **: p < 0.01, n = 7, One-way ANOVA, Tukey post hoc test, Tukey Kramer). For all groups, the bars from left to right are Mock, LOTUS, PirB, LOTUS + PirB. LOTUS suppresses the decrease in Aβ spine density. a. Dendritic spines in each treatment group in primary cultured cells of WT and LOTUS-tg mice were observed by confocal microscopy. b. Spine density in the range of 50 μm from the primary branch of the primary dendrite was measured. Spine density was calculated by dividing the number of spines by the length of the dendrite (*p < 0.05, **p < 0.01, n.s.: not significant, n = 5, Two-way ANOVA, post hoc Tukey test). LOTUS suppresses the binding of Aβ and PirB. a. Staining image of the binding experiment between Aβ and LilrB2 (human PirB). Cells bound with Aβ are stained dark blue (left panel). Scale bar is 100 μm. b. Graph quantifying the expression levels of LilrB2 in each group (n.s.: not significant, n = 4, One-way ANOVA, Tukey post hoc test). For all groups, the bars from left to right are Mock, hLOTUS, LilrB2, hLOTUS + LilrB2. Soluble LOTUS antagonizes the action of Nogo and increases the density of PSD-95 positive puncta in cultured hippocampal neurons. Quantification of synaptic density of PSD-95 positive puncta along the dendrites of each neuron. Data were normalized by the synaptic density of the solvent control group. Data are shown as mean ± SEM from 3 - 4 independent experiments. Total number of neurons (n) analyzed from 9 cells per condition. **P < 0.01, one-way ANOVA using post-hoc Dunnett's test. Overexpression of LOTUS increases the density of PSD-95 / bassoon positive puncta in cultured hippocampal neurons.(a, b) Cultured hippocampal neurons (DIV 14) from WT mice (a) and LOTUS-overexpressing transgenic (LOTUS-Tg) mice (b) were immunostained with antibodies against bassoon (red in the color image), PSD-95 (green in the color image), and MAP2 (blue in the color image). Scale bar is 10 μm. (c, d) Magnified images of (a) and (b). The segments were photographed at 3-fold magnification. Scale bar is 10 μm. (e) Quantification of the synaptic density of bassoon / PSD-95 positive puncta along the dendrites of each neuron. Data were normalized by the synaptic density of WT neurons. Data are shown as mean ± SEM from five independent experiments. The total number of neurons analyzed (n) ranged from 20 to 22 per condition. ***P < 0.001, Student's unpaired t-test. Overexpression of LOTUS increases spine density in the hippocampal CA1 region. (a) LOTUS controls dendritic spines at the tip of dendrites. Scale bar is 1 μm. (b) Quantification of spine density at the tip of dendrites of hippocampal neurons in the CA1 region; 40 to 43 dendrites were analyzed per mouse (WT: n = 3; LOTUS-Tg: n = 3). Data are shown as mean ± SEM. *P < 0.05, **P < 0.01, Student's unpaired t-test. (c) LOTUS controls dendritic spines at the base of dendrites. Scale bar is 1 μm. (d) Quantification of spine density at the base of dendrites of hippocampal neurons in the CA1 region; 40 to 44 dendrites were analyzed per mouse (WT: n = 3; LOTUS-Tg: n = 3). Data are shown as mean ± SEM. *P < 0.05, **P < 0.01, Student's unpaired t-test. Overexpression of LOTUS enhances social recognition memory. (a) Comparison of the social investigation (meeting) time for 1.5 minutes. Data are shown as mean ± SEM for WT mice (n = 13) and LOTUS-Tg mice (n = 13). ***P < 0.001 between day 1 and day 2, Student's paired t-test. (b) Recognition index. Data are shown as mean ± SEM for WT mice (n = 13) and LOTUS-Tg mice (n = 13).*P < 0.05, Student's unpaired t-test. Overexpression of LOTUS improves spatial learning. (a) Test after 3 days of training in WT mice and LOTUS-Tg mice. Data are shown as mean ± SEM for WT mice (n = 13) and LOTUS-Tg mice (n = 11). **P < 0.01, post-hoc Steel-Dwass test and χ. 2One-way ANOVA using the test. Opposite (OP), adjacent right (AR), target quadrant (TQ), adjacent left (AL). (b) Ratio of the time spent staying in the TQ during the test. Data are shown as mean ± SEM of WT mice (n = 13) and LOTUS-Tg mice (n = 11). **P < 0.01, Student's unpaired t-test. Overexpression of LOTUS prevents age-associated senile amnesia. (a) Immunoblot of endogenous LOTUS in the hippocampus of 2-month-old (young) and 18-month-old (aged) WT mice, and overexpressed LOTUS (HA-LOTUS) in the hippocampus of 2-month-old (young) and 18-month-old (aged) LOTUS-Tg mice. (b, c) Data were quantified by immunoblot intensity of the protein and normalized to the observed intensity of 2-month-old WT mice. Data are shown as mean ± SEM of 2-month-old (young; n = 6) and 18-month-old (aged; n = 6) WT mice, and 2-month-old (young; n = 6) and 18-month-old (aged; n = 6) LOTUS-Tg mice. **P < 0.01, Student's unpaired t-test. Overexpression of LOTUS prevents age-associated senile amnesia. (d) LOTUS-Tg mice have a high spine density at the tip of dendrites. Scale bar is 1 μm. (e) Quantification of the spine density at the tip of dendrites of hippocampal neurons in the CA1 region of 18-month-old (aged) WT mice and LOTUS-Tg mice; 40 dendrites were analyzed per mouse (WT: n = 3; LOTUS-Tg: n = 3). Data are shown as mean ± SEM. *P < 0.05, **P < 0.01, Student's unpaired t-test. (f) LOTUS-Tg mice have a high spine density at the base of dendrites. Scale bar is 1 μm. (g) Quantification of the spine density at the base of dendrites of hippocampal neurons in the CA1 region of 18-month-old WT mice and LOTUS-Tg mice; 40 dendrites were analyzed per mouse (WT: n = 3; LOTUS-Tg: n = 3). Data are shown as mean ± SEM. *P < 0.05, **P < 0.01, Student's unpaired t-test.Overexpression of LOTUS prevents age-associated senile amnesia. (h) Comparison of the social investigation (interview) time for 3 minutes. Data are shown as mean ± SEM for WT mice (n = 10) and LOTUS-Tg mice (n = 11). **P < 0.01, ***P < 0.001 between Day 1 and Day 2, Student's paired t-test. (i) Recognition index. Data are shown as mean ± SEM for WT mice (n = 10) and LOTUS-Tg mice (n = 11). ***P < 0.001, Student's unpaired t-test. Expression of Nogo and NgR1 in aged WT and LOTUS-Tg mice. Immunoblot of endogenous NgR1 and Nogo in the hippocampus of 2-month-old and 18-month-old WT and LOTUS-Tg mice. Data were quantified by the intensity of the protein immunoblot and normalized by the observed intensity of 2-month-old WT mice. Data are shown as mean ± SEM for 2-month-old WT mice (n = 6), 18-month-old WT mice (n = 6), 2-month-old LOTUS-Tg mice (n = 6), and 18-month-old LOTUS-Tg mice (n = 6). Student's unpaired t-test. Schematic diagram of the novel object recognition test performed in the examples. Mice exhibit exploratory behaviors such as sniffing the odor of the object out of curiosity. If the object is remembered on Day 1, the exploration time for the same object will be shorter on Day 2, and the exploration time for the novel object will be longer. Results of the novel object recognition test. Ratio of the exploration time for each object to the total exploration time on Day 2. The exploration time for the novel object is longer in WT and APP / LOTUS-Tg, and there is no difference in the exploration time for each object in APP-KI (Alzheimer's disease model mice). WT n = 6, APP n = 17, APP / LOTUS-Tg n = 7. ***: p < 0.005 Student t-test unpaired. In the present invention, the term "dementia" includes various dementias such as Alzheimer's disease (also referred to as Alzheimer's dementia), vascular dementia (also referred to as cerebrovascular dementia), frontotemporal dementia, dementia due to trauma, Lewy body dementia, dementia due to Parkinson's disease, etc. Senile dementia is also a form of dementia and includes Alzheimer's disease and vascular dementia. Further, the term "Alzheimer's disease" includes early-onset Alzheimer's disease and senile Alzheimer's disease. Early-onset Alzheimer's disease is generally Alzheimer's disease that develops before the age of 65, and senile Alzheimer's disease is Alzheimer's disease that develops at the age of 65 or older. Various cognitive function scales are used to determine the severity (mild, moderate, severe) of dementia. Generally, the evaluation of the degree of cognitive function is mainly performed using the Clinical Dementia Rating (CDR). In the United States, the MMSE, CDR, and Wechsler Memory Scale-IV Logical Memory II are often used. In the CDR, each of the six items of memory, orientation, judgment / problem-solving, social adaptation, home situation / interest / concern, and caregiving situation is evaluated on a scale of 0 to 3 points based on an evaluation form, and the severity is evaluated based on the total score of the six items. Although the definitions may vary from paper to paper, as an example, each item is evaluated as 0: no impairment, 0.5: suspected impairment, 1: mild impairment, 2: moderate impairment, 3: severe impairment, and the total score of the six items is 0.5 points for mild cognitive impairment (MCI), 1 - 6 points for mild dementia, 7 - 12 points for moderate dementia, and 13 - 18 points for severe dementia. In the present invention, the severity of dementia may be evaluated by this method. The dementia targeted in the present invention includes mild dementia, moderate dementia, and severe dementia. The treatment of dementia includes preventing the progression of the symptoms of dementia and improving the symptoms of dementia. The prevention of dementia includes the treatment of MCI. In one aspect, the agent for preventing or treating dementia is an agent for treating MCI or dementia. Generally, when the cognitive function is slightly reduced but not at a level that interferes with daily life, it is diagnosed as MCI, and when it is at a level that interferes with daily life, it is diagnosed as dementia. By administering the dementia treatment agent of the present invention at the stage of MCI, the progression to dementia can be prevented, and improvement of MCI can also be expected. In the present invention, amnesia includes various amnesias such as senile amnesia, anterograde amnesia, retrograde amnesia, transient amnesia, dissociative amnesia, etc. Further, forgetfulness is a memory disorder that does not interfere with daily life and is not diagnosed as amnesia, and includes a memory disorder at a level diagnosed as suspected amnesia. The patients targeted by the present invention include dementia patients including the above specific examples, patients with amnesia or forgetfulness including the above specific examples, elderly people (elderly people with amnesia or forgetfulness) whose memory and / or cognitive function has declined due to aging, and patients having accumulation of Aβ protein in the brain. The patient is typically a human. The elderly person is a human of 65 years old or older, and may be, for example, 70 years old or older, 75 years old or older, or 80 years old or older. Patients having accumulation of Aβ protein in the brain include not only patients showing decline in memory and / or cognitive function but also patients whose memory and / or cognitive function has not declined. The main example of the disease or condition in which Aβ accumulates in the brain is Alzheimer's disease, but the patients having Aβ accumulation in the brain targeted by the present invention are not limited to Alzheimer's disease, and widely include patients in whom Aβ accumulation in the brain has been confirmed by amyloid PET, cerebrospinal fluid (CSF) examination, or equivalent diagnostic methods. For patients or subjects in need of enhancing memory and / or cognitive function, the elderly whose memory and / or cognitive function has declined due to aging, patients with amnesia or forgetfulness (an example of patients or subjects in need of enhancing memory function), and patients with dementia are included. In one aspect, the patients or subjects in need of enhancing memory and / or cognitive function include elderly patients with senile amnesia, who are the elderly whose memory and / or cognitive function has declined due to aging. In one aspect, the patients or subjects in need of enhancing memory and / or cognitive function are patients with dementia. In one aspect, the patients or subjects in need of enhancing memory and / or cognitive function are patients with senile dementia. Senile dementia includes Alzheimer's disease and vascular dementia. Also, in one aspect, the patients in need of enhancing memory and / or cognitive function are patients with Alzheimer's disease, including patients with cognitive impairment due to early-onset Alzheimer's disease and patients with cognitive impairment due to late-onset Alzheimer's disease. Early-onset Alzheimer's disease is generally Alzheimer's disease that develops before the age of 65. Agents that inhibit the synapse-eliminating action of Aβ protein, Aβ protein production inhibitors, and Aβ protein clearance promoters can be preferably administered to patients in whom accumulation of Aβ protein in the brain has been confirmed. Accumulation of Aβ in the brain can be examined, for example, by amyloid PET, cerebrospinal fluid (CSF) examination, or equivalent diagnostic methods. When findings suggesting Aβ pathology are confirmed by these diagnostic methods, by administering an agent that inhibits the synapse-eliminating action of Aβ protein, an Aβ protein production inhibitor, and an Aβ protein clearance promoter, it is possible to improve the decline in memory and cognitive function and the symptoms based thereon, or suppress its progression. A preventive or therapeutic agent for dementia and an agent for enhancing memory and / or cognitive function may also be administered to patients in whom accumulation of Aβ protein in the brain has been confirmed. The substance used as an active ingredient in the agent of the present invention is any of the following. Two or more of (1) to (3) may be used in combination. For example, an agent of the present invention having (1) as an active ingredient and an agent of the present invention having (2) as an active ingredient may be administered to a patient in combination. (1) Crtac1B protein or a C-terminal region fragment thereof. (2) A vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof. (3) A cell expressing Crtac1B protein or a C-terminal region fragment thereof. The Crtac1B protein itself is known, and the mRNA sequence of the Crtac1B gene and the amino acid sequence of the Crtac1B protein encoded thereby are registered in NCBI's GenBank under NM_001206528.3. These sequences are shown as SEQ ID NO: 1 and SEQ ID NO: 2 in the Sequence Listing. SEQ ID NO: 3 shows the sequence of the coding region in the nucleotide sequence shown in SEQ ID NO: 1. As the Crtac1B protein, a polypeptide having the amino acid sequence shown in SEQ ID NO: 2 can preferably be used. Also, when there are mutations such as substitutions in some amino acids, if they are conservative substitutions, mutations in sites that are not important for activity, or when the sequence identity is sufficiently high, it is well-known that the properties and activities of the original protein are not impaired. Therefore, a polypeptide having an amino acid sequence that is partially different from the amino acid sequence of SEQ ID NO: 2 and has an identity of 95% or more, or 98% or more with SEQ ID NO: 2 is also likely to maintain the antagonistic action against NgR1 and PirB possessed by the Crtac1B protein having the amino acid sequence shown in SEQ ID NO: 2, and further maintain the binding ability to BACE1. Thus, it can be used as the Crtac1B protein which is the active ingredient of the agent of the present invention. Conservative substitutions, i.e., substitutions to amino acids with similar chemical properties, are likely to not impair the properties and activities of proteins. Amino acids with similar side chains have similar chemical properties. When classifying amino acids based on side chain similarity, for example, groups of amino acids with aliphatic side chains (glycine, alanine, valine, leucine, isoleucine), groups of amino acids with aliphatic hydroxyl side chains (serine, threonine), groups of amino acids with amide-containing side chains (asparagine, glutamine), groups of amino acids with aromatic side chains (phenylalanine, tyrosine, tryptophan), groups of amino acids with basic side chains (arginine, lysine, histidine), groups of amino acids with acidic side chains (aspartic acid, glutamic acid), groups of amino acids with sulfur-containing side chains (cysteine, methionine), etc. can be formed. Substitutions to another amino acid belonging to the same group are conservative substitutions. The identity of amino acid sequences is the percentage obtained by aligning two amino acid sequences to be compared so that as many amino acid residues as possible match, and dividing the number of matching amino acid residues by the total number of amino acid residues. When performing the above alignment, gaps are appropriately inserted into one or both of the two sequences to be compared as necessary. Such alignment of sequences can be performed using well-known programs such as BLAST, FASTA, CLUSTAL W, etc. When gaps are inserted, the above total number of amino acid residues is the number of residues counted with one gap counted as one amino acid residue. When the total number of amino acid residues counted in this way is different between the two sequences to be compared, the identity (%) is calculated by dividing the number of matching amino acid residues by the total number of amino acid residues of the longer sequence. In one aspect, the active ingredient of the agent of the present invention is a Crtac1B protein, a vector capable of expressing the Crtac1B protein, or a cell expressing the Crtac1B protein. The antagonistic effect of Crtac1B against NgR1 is known to exist in the region of residues 446 to 646 in the Crtac1B protein sequence of SEQ ID NO: 2 (Kurihara, Y., et al., Biochem. Biophys. Res. Commun. 2012, 418, 390-395.). This region is a region containing the UnbV_ASPIC (UA) domain (residues 460 to 518) and the EGF_CA (EC) domain (residues 559 to 605), and it is also known that fragments of only the UA domain or only the EC domain can bind to NgR1 (Kurihara, Y., et al. 2012 cited above). The nucleotide sequence encoding the region of residues 446 to 646 (also referred to as the UA / EC domain) and its amino acid sequence are shown in SEQ ID NOs: 6 and 7, the nucleotide sequence encoding the UA domain and the amino acid sequence of the UA domain are shown in SEQ ID NOs: 8 and 9, and the nucleotide sequence encoding the EC domain and the amino acid sequence of the EC domain are shown in SEQ ID NOs: 10 and 11, respectively. Therefore, a C-terminal region fragment of Crtac1B, specifically, (i) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 7, (ii) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 9, (iii) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 11, or (iv) a polypeptide having 90% or more, for example 95% or more, 97% or more, or 98% or more sequence identity with the protein fragments of (i) to (iii) also maintains the binding ability to NgR1 and PirB, and is considered to be able to exert the same preventive and therapeutic effects on dementia, enhancing cognitive and / or memory functions, suppressing synapse loss caused by Aβ, inhibiting Aβ production, and promoting Aβ clearance as the full-length Crtac1B protein, and thus can be used as an active ingredient of the agent of the present invention. In one embodiment, the C-terminal region fragment of Crtac1B is (i) a Crtac1B protein fragment comprising the amino acid sequence shown in SEQ ID NO: 7, (ii) a Crtac1B protein fragment comprising the amino acid sequence shown in SEQ ID NO: 9, or (iii) a Crtac1B protein fragment comprising the amino acid sequence shown in SEQ ID NO: 11. In another embodiment, the C-terminal region fragment of Crtac1B is a polypeptide of the amino acid sequence shown in SEQ ID NO: 7, 9, or 11, or a polypeptide having 90% or more, such as 95% or more, 97% or more, or 98% or more sequence identity with the polypeptide. In another embodiment, the C-terminal region fragment of Crtac1B is a polypeptide of the amino acid sequence shown in SEQ ID NO: 7, 9, or 11. In another embodiment, the C-terminal region fragment of Crtac1B is a Crtac1B protein fragment comprising the amino acid sequence shown in SEQ ID NO: 7, or a polypeptide having 90% or more, such as 95% or more, 97% or more, or 98% or more sequence identity with the fragment. In another embodiment, the C-terminal region fragment of Crtac1B is a polypeptide of the amino acid sequence shown in SEQ ID NO: 7, or a polypeptide having 90% or more, such as 95% or more, 97% or more, or 98% or more sequence identity with the polypeptide. The agent containing the Crtac1B protein of (1) or a C-terminal region fragment thereof as an active ingredient is a protein preparation. The Crtac1B protein or its C-terminal region fragment can be prepared by known genetic engineering techniques. For example, the DNA encoding the Crtac1B protein uses a human cDNA library or cDNA prepared from mRNA extracted from human cultured nerve cells as a template, and PCR is performed using a pair of primers designed to amplify the nucleotide sequence encoding the full-length Crtac1B protein shown in SEQ ID NO: 1. It can be prepared. For the C-terminal region fragment of the Crtac1B protein, PCR may be performed using a pair of primers designed to amplify the region encoding the C-terminal region fragment among the nucleotide sequences of SEQ ID NO: 1. The cDNA encoding the Crtac1B protein or its C-terminal region fragment containing mutations such as amino acid substitutions can be prepared by introducing mutations into the PCR-amplified cDNA fragment by a conventional method. By incorporating the prepared cDNA into an appropriate expression vector and introducing it into a host cell, and expressing the polypeptide in the host cell, the target Crtac1B protein or its C-terminal region fragment can be obtained. Various expression vectors and host cells are known and many commercial products are available, so they are easily obtainable. Isolation and purification of the target polypeptide from the host cell can be carried out by combining known separation operations. For example, treatment with a denaturing agent such as urea or a surfactant, sonication, enzymatic digestion, salting out or solvent fractionation precipitation method, dialysis, centrifugation, ultrafiltration, gel filtration, SDS-PAGE, isoelectric focusing electrophoresis, ion exchange chromatography, hydrophobic chromatography, affinity chromatography, reverse phase chromatography, etc. can be mentioned, but it is not limited thereto. The Crtac1B protein of (1) or a C-terminal region fragment thereof may be one to which techniques such as sugar chain addition, PEG addition, or using at least a part of the amino acids constituting the polypeptide as D-amino acids, which are techniques for improving in vivo stability and the like in peptide pharmaceuticals, are applied. Such techniques are well-known as described, for example, in J Am Chem Soc. 2004 Nov 3;126(43):14013-22 and Angew Chem Int Ed Engl. 2004 Mar 12;43(12):1516-20 (sugar chain addition), Clin Nephrol. 2006 Mar;65(3):180-90. and Proc Natl Acad Sci USA. 2005 Sep 6;102(36):12962-7. (PEG addition), J Pharmacol Exp Ther. 2004 Jun;309(3):1190-7 and J Pharmacol Exp Ther. 2004 Jun;309(3):1183-9. (use of D-amino acids), etc., and have already been used in the field of peptide pharmaceuticals. Alternatively, when a recombinant polypeptide is produced by genetic engineering techniques, it can undergo various post-translational modifications (removal of N-terminal methionine, N-terminal acetylation, sugar chain addition, limited degradation by intracellular proteases, myristoylation, isoprenylation, phosphorylation, etc.) in host cells. However, as long as such post-translationally modified forms of the polypeptide also have an antagonistic effect against NgR1 and PirB and can exhibit an action for preventing and treating dementia, an action for enhancing cognitive and / or memory functions, an action for suppressing synapse loss by Aβ, an action for inhibiting Aβ production, and an action for promoting Aβ clearance, they can be used as an active ingredient of the agent of the present invention and are included in the scope of the present invention. In addition, for the convenience of polypeptide production and other reasons, polypeptides with any amino acid sequence added, such as polypeptides with a Flag tag, His tag, GST added, or polypeptides in a form fused with other proteins or fragments thereof, are also those that utilize the present invention because the region that exhibits the various actions described above as the agent of the present invention is the region of the Crtac1B protein or a fragment of its C-terminal region. Therefore, such fusion proteins are also included in the scope of the present invention. In the case of an amino acid sequence fused with other proteins or the like, the amino acid sequence identity shall be calculated by extracting only the region corresponding to the Crtac1B protein or a fragment of its C-terminal region. For example, in the case of a polypeptide with a His tag added, the identity is calculated between the regions excluding the His tag. The protein preparation according to the present invention may consist only of a polypeptide, but usually, additives such as pharmacologically acceptable carriers, diluents, excipients, etc., suitable for each dosage form are appropriately mixed and formulated. Formulation methods and usable additives are well-known in the field of pharmaceutical preparations, and any method and additive can be used. Specific examples of additives include physiological buffer solutions, diluents such as tromethamine; stabilizers such as polyoxyethylene polyoxypropylene glycol; excipients such as sugar, lactose, corn starch, calcium phosphate, sorbitol, glycine, etc.; binders such as syrup, gelatin, gum arabic, sorbitol, polyvinyl chloride, tragacanth, etc.; lubricants such as magnesium stearate, polyethylene glycol, talc, silica, etc., but are not limited thereto. As the administration route of the protein preparation according to the present invention, intrathecal administration, intraventricular administration, or intracerebral administration is preferred, but it can also be used for other parenteral administrations such as intravenous administration, intramuscular administration, subcutaneous administration, intra-arterial administration, or oral administration. The dosage of the protein preparation according to the present invention may be any amount that can achieve the desired effect and is appropriately selected according to the patient's symptoms, severity, age, weight, etc. Usually, the amount of the active ingredient per day for the patient is 0.001 mg to 1000 mg, for example, 0.01 mg to 100 mg per kg of body weight, and it can be administered once or divided into several times. The administration may be daily or once every one to several days. An agent containing, as an active ingredient, a vector capable of expressing the Crtac1B protein of (2) or a C-terminal region fragment thereof is a gene therapy agent. The vector is not particularly limited as long as it can be expressed in the cells of the patient to be administered (typically in human cells, particularly in human nerve cells), and may be a plasmid vector or a viral vector, and any vector known in the field of gene therapy agents may be used. Preferred examples of viral vectors include retroviral vectors, adenoviral vectors, adeno-associated viral vectors, vaccinia viral vectors, etc., and among them, an adeno-associated viral vector with high central migration ability (such as AAV9 type) can be preferably used. The polynucleotide (DNA or RNA) encoding the Crtac1B protein or a C-terminal region fragment thereof can be prepared as described above. "Crtac1B protein" and "C-terminal region fragment of Crtac1B" are as defined above. The polynucleotide encoding the Crtac1B protein can be, for example, a polynucleotide having a nucleotide sequence with 90% or more, such as 95% or more, or 98% or more identity with the nucleotide sequence shown in SEQ ID NO: 3. When the C-terminal region fragment of Crtac1B is a polypeptide (UA / EC domain fragment) with the amino acid sequence shown in SEQ ID NO: 7, the polynucleotide encoding it can be a polynucleotide having a nucleotide sequence with 90% or more, such as 95% or more, or 98% or more identity with the nucleotide sequence shown in SEQ ID NO: 6. When the C-terminal region fragment of Crtac1B is a polypeptide (UA domain fragment) with the amino acid sequence shown in SEQ ID NO: 9, the polynucleotide encoding it can be a polynucleotide having a nucleotide sequence with 90% or more, such as 95% or more, or 98% or more identity with the nucleotide sequence shown in SEQ ID NO: 8. When the C-terminal region fragment of Crtac1B is a polypeptide (EC domain fragment) with the amino acid sequence shown in SEQ ID NO: 11, the polynucleotide encoding it can be a polynucleotide having a nucleotide sequence with 90% or more, such as 95% or more, or 98% or more identity with the nucleotide sequence shown in SEQ ID NO: 10. The incorporation of the polynucleotide encoding the Crtac1B protein or a C-terminal region fragment thereof into a vector can be carried out by methods well known to those skilled in the art. The gene therapy agent according to the present invention may consist only of the vector of (2), but usually, additives such as pharmacologically acceptable carriers, diluents, excipients, etc., suitable for each dosage form are appropriately mixed and formulated. Specific examples of the additives are as described above. The administration route is preferably intrathecal administration, intraventricular administration or intracerebral administration, but it can also be used for other parenteral administrations such as intravenous administration, intramuscular administration, subcutaneous administration, and intraarterial administration. The dosage of the gene therapy agent according to the present invention may be any amount that can achieve the desired effect, and is appropriately selected according to the patient's symptoms, severity, age, weight, etc. Usually, the amount of the active ingredient per day for the patient is about 0.1 μg to 100 mg, for example, about 1 μg to 10 mg per kg of body weight. The gene therapy agent is generally used for single administration, but is not limited to single administration. An agent containing cells expressing the Crtac1B protein of (3) or a C-terminal region fragment thereof as an active ingredient can also be referred to as an ex vivo gene therapy agent. As the cells, neural stem / progenitor cells, excitatory neurons (neurons using glutamate as a neurotransmitter) or oligodendrocyte progenitor cells can be preferably used. These cells can be prepared by inducing differentiation from pluripotent stem cells such as induced pluripotent stem (iPS) cells and mesenchymal stem cells. When the patient is a human, human-derived cells are used as the cells expressing the Crtac1B protein or a C-terminal region fragment thereof. The method for producing iPS cells is well known. Mesenchymal stem cells can be collected from umbilical cord blood. Neural stem / progenitor cells are a cell population that includes neural stem cells and neural progenitor cells, and can be prepared from iPS cells by the method described in, for example, Itakura G et al., 2015, PLoS One 10, e0116413. Specifically, iPS cells are cultured in a standard ES cell medium together with irradiated mouse embryonic fibroblasts using a gelatin-coated (0.1%) culture dish to form embryoid bodies (EBs). 30 days after EB formation, the EBs are enzymatically treated and separated into single cells, and the cells are cultured in suspension for 12 days in a serum-free medium containing EGF and bFGF to form neurospheres (spherical cell masses). By subculturing this primary iPS cell-derived neurosphere 2 to 3 times, iPS cell-derived neural stem / progenitor cells can be obtained. Excitatory neurons can be prepared by culturing neural stem / progenitor cells in an appropriate serum-free medium in the presence of a differentiation inducer for neurons such as retinoic acid and a neural cell growth factor such as b-FGF to induce differentiation. The specific procedure for preparing excitatory neurons from pluripotent stem cells is as described in Preparation Example 1 of the following Examples. Introduction of a polynucleotide encoding the Crtac1B protein or a C-terminal region fragment thereof may be performed on iPS cells, or on single cells obtained by enzymatic treatment and separation of primary, or second or third passage neurospheres, or on neural stem / progenitor cells after differentiation induction. When using excitatory neurons, in addition to the above, it may also be performed on excitatory neurons after induction of differentiation into neurons. When introducing a polynucleotide into neurosphere cells, the cells after introduction can be cultured in suspension to form neurospheres again and subcultured. Introduction of a polynucleotide into cells can be performed, for example, by infecting cells with a recombinant virus in which a polynucleotide encoding the Crtac1B protein or a C-terminal region fragment thereof is incorporated into an adeno-associated virus or a lentiviral vector. Note that iPS cell-derived neural stem / progenitor cells expressing LOTUS / Crtac1B themselves are known and described in Ito et al., Stem Cell Reports 2021, 16:1-15. Oligodendrocyte progenitor cells can be prepared from pluripotent stem cells by, for example, the method described in Douvaras and Fossati, Generation and isolation of oligodendrocyte progenitor cells from human pluripotent stem cells. Nat Protoc 10, 1143-1154 (2015). The specific procedure is as described in Preparation Example 2 of the following Examples. The ex vivo gene therapy agent according to the present invention is preferably used by intrathecal administration, intraventricular administration, or intracerebral parenchymal administration, similar to protein preparations and gene therapy agents. However, parenteral administrations such as intravenous administration and intraperitoneal administration are also possible. The cells of (3) can be formulated as an intravenous drip injection, drip agent, or injection containing the cells of (3) in a medium suitable for these administration routes. As the medium, for example, an aqueous medium (e.g., high-purity sterilized water) containing about 2.5 to 5% human serum albumin, about 0.2 to 0.5% sodium chloride, and about 3 to 8% dimethyl sulfoxide as a cryoprotectant can be used. The number of cells of (3) in the preparation for one administration (e.g., one bag of intravenous drip injection) can be appropriately set according to the age, weight, symptoms, etc. of the patient. For example, the viable cell count can be about 1 x 10 5 ~1 x 10 9 cells. The ex vivo gene therapy agent is generally used by single administration, but is not limited to single administration. Hereinafter, the present invention will be described more specifically based on Examples. However, the present invention is not limited to the following Examples. Example 1: BACE1 Experiment [Materials and Methods] Construction of Expression Plasmid The human BACE1 (NM_012104.4, SEQ ID NO: 12) or human APP695 (NM_201414.3, SEQ ID NO: 14) coding sequences were incorporated into the vector pcDNA3.1(+) vectors (Invitrogen) to generate the human BACE1 / pcDNA3.1+ plasmid and the human APP / pcDNA3.1+ plasmid. Using the human cDNA library brain (TAKARA) as a template, PCR was performed under the conditions described in Table 2 using the enzyme KOD plus (TOYOBO) and the primers shown in Table 1 to amplify the coding sequences of human BACE1 and human APP695. The PCR products and the vector were treated with restriction enzymes, and the PCR products were incorporated into the vector using the Ligation-Convenience Kit (NIPPON GENE CO, LTD.). The prepared plasmids were subjected to sequence analysis (Fasmac). Preparation of soluble LOTUS HEK293T cells were seeded at 9.0×10 in a 15 cm culture dish 6Cells / dish were seeded with a total volume of 30 ml of medium. After culturing for 2 days (37 °C, 5% CO2), the plasmid was introduced with 0.1% PEI (Polyethyleneimine), and then cultured for 4 days. As the plasmid, the one in which LOTUS (SEQ ID NO: 4) without a membrane-binding region was incorporated into a vector having the sequence of SBP-hFc (Human IgG1 Fc) tag was used. The target protein (SBP-hFc-human LOTUS) was secreted into the culture supernatant. After culturing, the supernatant was collected and completely separated from the supernatant using an ultracentrifuge (40000 rpm, 4 °C, 1 hour). The centrifuged supernatant was passed through High Capacity Streptavidin Agarose Resin (Thermo Scientific) that specifically binds to SBP (4 °C, 10 sec / drop, Overnight). Then, the target protein was competitively eluted with a Biotin solution (2 mM Biotin / PBS) that binds stronger than Streptavidin and collected into a 0.6 ml siliconized tube. The recovered protein (SBP-hFc-human LOTUS) was subjected to CBB staining after SDS-PAGE, and the concentration was calculated based on a BSA sample with a known concentration diluted for the calibration curve. Pull-down assay COS-7 cells were seeded at 5.0×10 on a 6 cm cell culture plate (Greiner bio-one). 5Cells were seeded at a density of cells / well and a total volume of 2 ml of medium. After incubation for 4 hours (37 °C, 5% CO2), SBP-FLAG-human LOTUS (a 141 bp nucleotide sequence encoding SBP-FLAG (SEQ ID NO: 27) (SEQ ID NO: 26) ligated to a 1938 bp nucleotide sequence encoding human LOTUS (SEQ ID NO: 2) (SEQ ID NO: 3); SEQ ID NOs: 28, 29) and a plasmid encoding human BACE1 or human APP were introduced using Lipofectamine 3000. After incubation for 2 days (37 °C, 5% CO2), the cells were transferred to ice and washed twice with cold PBS. Proteins were recovered using lysis buffer (20 mM Tris pH 7.4, 150 mM NaCl, 1% Nonidet P-40, 10 mM NaF, 1 mM sodium orthovanadate (Sigma-Aldrich), 10 μg / ml leupeptin (Nacalai Tesque), 0.1 U / ml aprotinin (Sigma-Aldrich), 50 μM p-amidinophenyl-methylsulfonyl fluoride (Nacalai Tesque)). The recovered cell lysate was stirred (4 °C, 10 min, mild rotation) and then centrifuged (15,000 rpm, 4 °C, 10 min). The supernatant was recovered and 15 μl / sample of SBP-specific beads (Streptavidin agarose: GE Healthcare) was added and mixed (4 °C, 3.5 h, mild rotation). Thereafter, the beads were washed with 1% Tryton-X / MilliQ and centrifuged (6,400 g, 4 °C, 10 min) 4 times. Reduction treatment was performed at 100 °C for 7 min with 2.5% mercaptoethanol / 1× sample buffer, and analysis was performed by Western blot. The pull-down assay for soluble LOTUS was performed by the following two methods. (i) The purified SBP-hFc-human LOTUS or SBP-hFc (Tag) was diluted to a final concentration of 1 μM in the maintenance medium and added to COS-7 cells that overexpressed BACE1 or APP. Incubate for 30 minutes (37 °C, 5% CO2), and the proteins were recovered using lysis buffer. (ii) The purified SBP-hFc-human LOTUS or SBP-hFc (Tag) was added to the cell lysate of COS-7 cells overexpressing BACE1 at a final concentration of 1 μM and mixed (4 °C, overnight, mild rotation). The cell lysates obtained in (i) and (ii) were mixed with 15 μl / sample of Streptavidin agarose resin (4 °C, 4 h, mild rotation). Subsequently, the beads were washed with 1% Tryton-X / MilliQ and centrifuged (6,400 g, 4 °C, 10 min), and this operation was repeated 4 times. Reduction treatment was performed at 100 °C for 7 min with 2.5% mercaptoethanol / 1×sample buffer, and analysis was performed by Western blot. Western blot analysis The extracted protein was reductively treated at 100 °C for 7 min with 2.5% mercaptoethanol / 1× sample buffer. It was electrophoresed on an 8-12% polyacrylamide gel (10 mA / gel, 10 min → 20 mA / gel, 90 min) and transferred to a PVDF membrane (Millipore) (100 mA, 60 min). Blocking was performed with 5% skim milk / TBST for BACE1, SBP, and BACE1, and 5% BSA / TBST for β-Actin, sAPPβ, and β-CTF (room temperature, 60 min, shaking). Next, a primary antibody reaction (4 °C, overnight, shaking) was carried out using a BACE1 antibody (MAB5308, Merck Millipore, 1 / 5000, 5% skim milk / TBST), an SBP antibody (sc-101595, Santa Cruz Biotechnology, 1 / 10000, 5% BSA / TBST), a β-CTF antibody (A8717, R&D SYSTEMS, 1 / 5000, 5% BSA / TBST), an sAPPβ antibody (IL-902, IBL, 1 / 500, 5% BSA / TBST), and a β-Actin antibody (AC04, Wako, 1 / 10000, 5% BSA / TBST). The secondary antibody reaction was carried out using Peroxidase-conjugated AffiniPure Donkey anti-mouse IgG (715-035-020: Jackson ImmunoReseach LABORATORIES, INC) and Peroxidase-conjugated AffiniPure Goat anti-rabbit IgG (111-035-003: Jackson ImmunoReseach LABORATORIES, INC) (room temperature, 1 h, shaking). Protein detection was performed using a chemiluminescence reagent (GE healthcare, Millipore, TAKARA) as a substrate and photographed with a LAS-4000 (Fuji Film) image analyzer. Quantification of APP Fragment Proteins COS-7 cells were seeded at 5.0×10 5 cells / well in a 6 cm cell culture plate (Greiner bio-one) with a total medium volume of 2 ml. After incubation for 4 hours (37 °C, 5% CO2), plasmids encoding human BACE1, human APP, and human LOTUS were introduced using Lipofectamine 3000 and incubated for 2 days (37 °C, 5% CO2). The cells were transferred onto ice, and the collected culture supernatant was centrifuged (800 g, 10 min, 4 °C) and subjected to reduction treatment at 100 °C for 7 min with 2.5% mercaptoethanol / 1× sample buffer. The cell lysate was obtained by washing the cells twice with PBS (4 °C) and then collecting them using lysis buffer (20 mM Tris pH 7.4, 150 mM NaCl, 1% Nonidet P-40, 10 mM NaF, 1 mM sodium orthovanadate (Sigma-Aldrich), 0.1 U / ml aprotinin (Sigma-Aldrich), 50 μM p-amidinophenyl-methylsulfonyl fluoride (Nacalai Tesque)). After centrifuging the cell lysate (15,000 rpm, 10 min, 4 °C), the supernatant was collected. It was subjected to reduction treatment at 100 °C for 7 min with 2.5% mercaptoethanol / 1× sample buffer and analyzed by Western blot. The results were statistically processed using the unpaired t-test method with a significance level (risk rate) of 5%. BACE1 Assay The activity of BACE1 was measured using the Sensolyte 520 β-secretase assay kit (Anaspec). Fluorescent dye molecules of donor and acceptor are included at both ends of the APP peptide (substrate) containing the Swedish mutation, and fluorescence that can be measured is emitted upon BACE1 cleavage. Fluorescence was measured according to the protocol of the kit. To 40 μl of BACE1 recombinant protein diluted 50-fold with 1x Assay buffer (pH 4.5), 10 μl each of 2.5 μM SBP-hFc-LOTUS or 2.5 μM SBP-hFc (Tag) and 5 μM LY2886721 (BACE1 inhibitor) were added and reacted (10 min, 37 °C). Then, 50 μl of Substrate diluted 100-fold with 1x Assay buffer (pH 4.5) was added and reacted (30 min, 37 °C). The fluorescence wavelength at an excitation wavelength / fluorescence wavelength of 490 nm / 520 nm was measured using Varioskan (Thermo). The results were statistically analyzed by the One-Way ANOVA Dunnett method, and the significance level (risk rate) was set at 5%. [Results] LOTUS binds to BACE1 BACE1 undergoes post-translational modification of palmitoylation and localizes to membrane microdomains "rafts" approximately 10 nm to 200 nm in size formed from cholesterol and sphingolipids (Kulandaivelu S., Gopal T., Biochim Biophys Acta, 2010; 1801(8): 860-867). Since LOTUS is a GPI-anchored protein, it was considered possible that LOTUS and BACE1 localize and bind in a proximal environment within the raft. In addition, there are a membrane-bound type (SEQ ID NO: 2) and a soluble type (SEQ ID NO: 5) in which the C-terminus is cleaved and secreted for LOTUS. Since the mechanisms of action of membrane-bound LOTUS and soluble LOTUS on NgR1 are different, it was considered possible that the binding modes to BACE1 are different between the membrane-bound and soluble types. Therefore, the binding of both membrane-bound and soluble LOTUS to BACE1 was examined. First, to examine membrane-bound LOTUS, COS-7 cells were co-expressed with human BACE1 and SBP-FLAG-LOTUS and subjected to a pull-down assay. As a result, BACE1 was detected by an anti-BACE1 antibody in the lysate pulled down by SBP (Figure 1A). Next, to examine soluble LOTUS, purified SBP-hFc-LOTUS or SBP-hFc (Tag) was added at 1 μM to COS-7 cells overexpressing human BACE1. As a result of the pull-down assay, BACE1 was not detected in the lysate pulled down by SBP (Figure 1B). On the other hand, when SBP-hFc-LOTUS or SBP-hFc (Tag) was added at 1 μM to the cell lysate of COS-7 cells overexpressing human BACE1, BACE1 was detected in the lysate pulled down by SBP (Figure 1C). From the above, it was found that both membrane-bound and soluble LOTUS bind to BACE1. Membrane-bound LOTUS suppresses APP cleavage by BACE1 To examine whether LOTUS is involved in the Aβ production process, human LOTUS, human BACE1, and human APP were co-expressed in COS-7 cells, and the expression levels of β-CTF and sAPPβ produced by BACE1 cleavage of APP were quantified. It was confirmed that there was no difference in the BACE1 expression level between the cells expressing LOTUS and the control (mock) (Figures 2A and 2B). β-CTF is a membrane-bound C-terminal fragment produced by APP upon BACE1 cleavage. In the cells expressing LOTUS, the expression level of β-CTF was significantly decreased compared to the control (mock) (Figures 2C and 2D). On the other hand, sAPPβ is the extracellular region secreted by APP upon BACE1 cleavage. Therefore, sAPPβ in the culture supernatant was quantified. In the cells expressing LOTUS, the expression level of sAPPβ was significantly decreased compared to the control (mock) (Figures 2E and 2F). Soluble LOTUS suppresses BACE1 activity To examine whether LOTUS directly controls the activity of BACE1, BACE1 activity was measured using a β-secretase assay kit (Anaspec). LY2886721 (BACE inhibitor), which has been shown to inhibit the activity of BACE1, was used as a control. Purified 2.5 μM SBP-hFc-LOTUS or 2.5 μM SBP-hFc (Tag), 5 μM inhibitor, and 2 mM biotin / PBS (vehicle control) were each reacted with BACE1 recombinant protein for 10 minutes. Subsequently, the substrate attached to the kit (FRET peptide of APP with Swedish mutation) was added and the reaction was carried out at 37 °C under a pH 4.5 environment for 30 minutes. BACE1 activity can be quantified by measuring the fluorescence wavelength at an excitation wavelength / fluorescence wavelength of 490 nm / 520 nm. Soluble LOTUS significantly decreased BACE1 activity compared to the control (Tag) (Figure 3). Example 2: Microglia Experiment [Materials and Methods] Primary microglia cells The cortex of C57B6J mice at postnatal days 0 to 3 was excised, dispersed with 0.125% trypsin (37 °C, 5 minutes), and then suspended in DMEM (10% heat-inactivated FBS + 0.5% Penicillin streptomycin) + 0.01 mg / ml DNaseI medium. Subsequently, the cells were filtered through a 70 μm filter and seeded into a T75 flask coated with 10 μg / ml PLL (Polyethylenimin) with approximately 4.5×10 6 cells, and the glial mixed cells were cultured for 14 days (37 °C, 5% CO2). After 14 days, only microglia were detached from the glial mixed cells, dispersed again with DMEM (high glucose), and seeded. Preparation of Aβ After dissolving Biotin-LC-Aβ(1-42) in 1% aqueous ammonia, it was diluted with PBS to a final concentration of 100 μM. Then, it was polymerized by incubating at 37 °C for 48 hours (oligomer Aβ: hereinafter abbreviated as Aβ). In the phagocytosis assay, after mixing with avidin-pHrodo in equimolar amounts and allowing to stand on ice for 30 minutes, an oligomer Aβ-pHrodo complex (Aβ-pHrodo) was prepared. ELISA, WST assay Primary microglial cells were treated with purified proteins [SBP-FLAG (Tag), SBP-FLAG-soluble LOTUS (sLOTUS)] (final concentrations of 200, 500 nM) and Aβ (final concentration of 1 μM) for 24 hours, and the cytokines contained in the supernatant were measured according to an ELISA Kit (Invitrogen). On the other hand, a WST kit (Dojin) was added to the cell bodies so that DMEM (high glucose):WST = 100:10, and the absorbance at 450 nm was measured after 4 hours. Phagocytosis assay Microglial cultured cells were treated with purified proteins [SBP-FLAG (Tag), SBP-FLAG-soluble LOTUS (sLOTUS)] (final concentration of 500 nM) and Aβ-pHrodo (500 ng) for 4 hours, and then fixed with 4% PFA / PBS (room temperature, 30 minutes, light-shielded). After permeabilization with 0.3% TritonX-100 / PBS (room temperature, 10 minutes), it was reacted with DAPI / PBS (1 / 2000) for 10 minutes and then observed with a Nikon fluorescence microscope. The number of cells (Aβ-pHrodo / DAPI) was counted using ImageJ. [Results] The survival rate of microglia is improved by sLOTUS Microglia are stably maintained by repeating proliferation and apoptosis from birth to old age (Katharina Borst et al., Immunity, 2021 Oct 12;54(10):2194-2208.). In chronic neuropathy and aging, it has been reported that microglial dysfunction contributes to the progression of the disease state (Yanling Hu et al., Cell Rep. 2021 Jun 8;35(10):109228. and T Kreisel et al., Mol Psychiatry. 2014 Jun;19(6):699-709.). Therefore, the relationship between LOTUS and the viability of microglia was examined. sLOTUS was added to primary microglial cells, and the number of live cells was measured using the WST assay. Since the WST assay is a color reaction using the reduction reaction by mitochondrial dehydrogenase in live cells, it can be seen that the higher the absorbance, the more live cells there are. As a result, it was revealed that when treated with sLOTUS for 24 hours, the number of live microglia increased by about 40% compared to the control with the purified Tag of sLOTUS (Figure 4A). Furthermore, even when sLOTUS and Aβ were added simultaneously, it was revealed that the number of live microglia increased by about 20% due to sLOTUS (Figure 4B). On the other hand, when treated with sLOTUS or Aβ for 4 hours in the same manner as the Phagocytosis Assay, it was confirmed that there was no change in the number of live cells compared to the control with the purified Tag of sLOTUS. Also, the number of dead cells was measured by the LDH assay. Since LDH is released extracellularly when the cell membrane is damaged, it can be seen that the higher the absorbance, the more dead cells with a disintegrated cell membrane there are. As a result, it was revealed that the number of dead cells decreased by about 20% due to sLOTUS compared to the control with the purified Tag (Figure 4C). Furthermore, even when sLOTUS and Aβ were added simultaneously, it became clear that there was a tendency for the number of dead microglia to decrease due to sLOTUS (Figure 4D). From the above results, it became clear that sLOTUS improves the survival rate of microglia. sLOTUS promotes the phagocytosis of Aβ by microglia Microglia have been reported to suppress the progression of the disease by removing Aβ in the brain through the Aβ clearance function (Ana Griciuc et al., Neuron. 2013 May 22;78(4):631-43. and Shweta Mandrekar et al., J Neurosci. 2009 Apr 1;29(13):4252-62.). Therefore, the relationship between LOTUS and phagocytic ability in microglia was examined. sLOTUS and Aβ-pHrodo were simultaneously added to primary microglial cells, and 4 hours later, the phagocytic ability of microglia for Aβ was analyzed by the Phagocytosis Assay method. The Aβ-pHrodo used was taken up by microglia and emitted fluorescence in response to the pH change in lysosomes. Therefore, the number of Aβ phagocytosed was evaluated by quantifying the fluorescence. In fluorescence microscope images, the number of fluorescences was observed to be higher with sLOTUS compared to the control with the purified Tag of sLOTUS (image data is omitted). Therefore, as a result of quantifying the number of fluorescences, it was revealed that Aβ phagocytosis by microglia increased by approximately 20% with the addition of sLOTUS (Figure 5). Furthermore, the same tendency was confirmed even when phagocytosis was evaluated with Aβ-pHrodo after treating with sLOTUS in the same manner as ELISA for 24 hours. Example 3: Aβ antagonistic action of LOTUS via PirB [Materials and Methods] Culture of COS-7 cells In African green monkey kidney-derived COS-7 cells, DMEM (4.5 g / l Glucose with L-glutamine and sodium pyruvate: Nacalai Tesqu) supplemented with 10% heat-inactivated FBS (Biological Industries) and 0.5% Penicillin / streptomycin (Nacalai Tesque) was used as the maintenance medium, and cultured in a 10 cm culture dish at 37°C under 5% CO2 conditions. Subculture was performed once every 3 days. Gene transfer into COS-7 cells by Lipofection method COS-7 cells were seeded at 5.0×10 4 cells / well in a 4-well culture plate (Thermo Scientific) with a total medium volume of 400 μl and incubated until the cells adhered (37 °C, 5% CO2, 4 hours). After confirming cell adhesion, plasmids were introduced using FuGENE6 Transfection Reagent (Roche) to overexpress mouse PirB (NM_001357394.1, SEQ ID NOs: 16, 17), mouse LOTUS (NM_145123.5, SEQ ID NOs: 18, 19), human LilrB2 (NM_001080978.4, SEQ ID NOs: 20, 21), and human LOTUS (NM_001206528.3, SEQ ID NOs: 1, 2). The expression of each protein was confirmed by immunostaining. Immunostaining Immunostaining was performed to confirm the expression of each protein. After 44 hours from plasmid addition, a primary antibody reaction (37 °C, 5% CO2, 1 hour) was performed using anti-LOTUS (R&D) and anti-PirB IgG (R&D), anti-LilrB2 (R&D) diluted 200-fold in maintenance medium. After the reaction, the samples were fixed with 4% PFA / PBS (room temperature, 1 hour, protected from light), and a secondary antibody reaction (room temperature, protected from light) was performed using Alexa Fluor 488 anti-Goat IgG (Jackson ImmunoResearch) and Alexa Fluor 596 anti-goat IgG (Jackson ImmunoResearch). The stained samples were observed and imaged for fluorescence using a BZ-8100 microscope (Keyence). Experiment on inhibition of Aβ-PirB binding by LOTUS COS-7 cells were co-expressed with mouse PirB and mouse LOTUS, or human LilrB2 and human LOTUS by the above Lipofection method. After 44 hours of plasmid addition, Aβ subjected to polymerization treatment was diluted with maintenance medium to each concentration (100 nM, 200 nM, 500 nM) and added, and incubated (37 °C, 5% CO2, 1 hour). After fixation with 4% PFA / PBS (room temperature, 1 hour, light-shielded), activation treatment (67 °C, 1 hour) was performed. Furthermore, AP (Alkaline Phosphatase) was added to Aβ by the ABC method (Avidin-Biotinylated enzyme Complex method). A substrate mixture of NBT / BCIP (4-Nitoro blue tetrazolium chrolide / 5-Bromo-4-chloro-3-indolyl-phosphatase: Roche) for the added AP was added to perform a color reaction. Cells to which Aβ is bound are colored dark blue. The stained samples were observed and imaged under bright field with a BZ-8100 microscope (Keyence). Furthermore, for quantification of binding, a pNPP solution (1 mg / ml p-Nitrophenyl phosphate) was added as a substrate for the AP added to Aβ by the above method, and the absorbance at 405 nm was measured using a microplate reader X MarkTM (BioRad) after 4 hours. The expression of each protein was confirmed by immunostaining. Animal C57BL / 6J wild-type mice (WT) were purchased from Japan SLC. Lotus gene overexpressing transgenic mice (LOTUS-tg) were prepared by inserting, by microinjection method, a Synapsin-1, which is specifically expressed in axons of nerve cells, as a promoter, an Igk chain secretion signal, an HA tag gene, a mouse lotus gene (region encoding aa29-646 of mouse LOTUS, positions 240-2096 of SEQ ID NO: 18), and a Rabbit β-globin (Ex2-Ex3) intron / polyA sequence into pronuclear stage fertilized eggs of C57BL / 6J mice. All were given a standard mouse breeding environment and autoclaved feed and water. Primary culture method of hippocampal neurons The hippocampus was dissected from mouse embryos (E17.5) and dispersed at 37°C for 12 minutes using 0.25% Trypsine and 100 μg / ml DNase. The dispersed cells were seeded at 5×10 4 cells / well in a 24-well plate with a glass coverslip (φ12 mm: Matsunami) placed on the bottom. The glass coverslip was surface-treated with a 100 μg / ml Poly-L-Lysin solution before seeding. Neurobasal medium (gibco) and 10% FBS (biowest) were used as the plating medium, and 1xB-27 (gibco), 1xGlutamax (gibco), and Neurobasal medium (gibco) were used as the maintenance medium. Gene transfection into primary cultured hippocampal neurons by Lipofection method To clearly observe the cell morphology, an experiment was conducted to forcibly express EGFP by transfection in primary cultured cells. Gene transfection was performed on primary cultured cells on the 11th day in vitro (DIV11). In a 1.5 ml tube, 1.5 μl of Viafect Transfection reagent (Promega) and 0.5 μg of plasmid DNA were mixed with 50 μl of Neurobasal medium and allowed to stand (room temperature, 15 minutes). Then, it was added to the 24-well plate seeded with cells and incubated (37°C, 5% CO2, 3 hours). After incubation, the medium was removed and the remaining reagents were washed with pre-warmed HBSS at 37°C, and 400 μl / well of maintenance medium was added and incubated until each treatment (37°C, 5% CO2). Quantification of spine density Primary cultured cells 1 day after gene introduction (DIV12) were treated with Aβ at each concentration (0 nM, 200 nM, 500 nM) (37 °C, 5% CO2, 2 days). The treated cells were fixed and encapsulated in the same manner as described above. Imaging was also performed in the same manner as described above. Spines within a range of 50 μm from the branch of the dendrite closest to the cell body were measured. Spines that protruded from the dendrite by 0.5 μm or more and had a width of the protruding part of 0.5 μm or more were counted as spines. The number of spines per 10 μm of the analyzed dendrite was defined as the spine density. [Results] LOTUS inhibits the binding of Aβ and PirB To examine the effect of LOTUS on the binding of Aβ and PirB, experiments were conducted using COS-7 cells co-expressing PirB and LOTUS. First, the binding of Aβ and PirB was confirmed as reported previously (Kim T, et al. Science. 2013;341(6152):1399-404.). When cells overexpressing PirB were treated with Aβ at each concentration (100 nM, 200 nM, 500 nM), the binding (color development) intensity of Aβ increased in a concentration-dependent manner (Figure 6a). In cells co-expressing LOTUS and PirB, the binding of Aβ was decreased compared to that in cells expressing PirB alone. Also, to confirm whether LOTUS affects the expression level of PirB, the expression of PirB in each group was confirmed by the pNPP method. As a result of the experiment, no difference in the expression level of PirB was observed between the single expression of PirB and the co-expression of LOTUS + PirB (Figure 6b). From this, it was found that in this experiment, LOTUS inhibits the Aβ-PirB binding without affecting the expression level of PirB. Next, experiments were conducted using pNPP for quantitative analysis. pNPP reacts with AP to develop a yellow color. Since the AP activity can be quantified by measuring the absorbance at 405 nm of the colored solution, the binding of Aβ can be quantified. In the pNPP method, the binding of Aβ was suppressed by approximately 20% in the co-expression of LOTUS and PirB compared to the single expression of PirB (Figure 6c). From these results, it was found that LOTUS inhibits the binding of Aβ and PirB. LOTUS inhibits the decrease in spine density caused by Aβ The spine is a structure on the postsynaptic side of the synapse, which is the junction between nerve cells. In Alzheimer's disease (AD), it is thought that the decrease in spine density of neurons in the brain leads to a decline in neural plasticity and cognitive function (Querfurth HW, LaFerla FM. N Engl J Med. 2010, 362:329-44.; and Mucke L, Masliah E, Yu GQ. J Neurosci. 2000, 20:4050-8.). In primary cultured hippocampal neurons of WT mice, the addition of Aβ decreased the spine density in a concentration-dependent manner (Figures 7a, b). In contrast, in primary cultured neurons of LOTUS-tg mice, the decrease in spine density caused by Aβ was suppressed (Figures 7a, b). From these results, it was found that LOTUS suppresses the decrease in spine density caused by Aβ. Human LOTUS inhibits the binding of Aβ to LilrB2 (human PirB) For the purpose of analyzing the function of LOTUS in humans, a binding experiment of Aβ was conducted in the same manner as in FIG. 6 to verify whether human LOTUS has an antagonistic effect on LilrB2 (NM_001080978.4, SEQ ID NO: 20, 21), which is the human homolog of PirB. LilrB2 was expressed in COS-7 cells, and Aβ was treated at each concentration (100 nM, 200 nM, 500 nM). As a result, the binding (color development) intensity of Aβ increased in a concentration-dependent manner (FIG. 8a). In cells co-expressing human LOTUS and LilrB2, the binding of Aβ was significantly decreased compared to that in cells expressing LilrB2 alone. In addition, in order to confirm whether human LOTUS affects the expression level of LilrB2, the expression level of LilrB2 in each group was examined, and no difference in the expression level was found between the single expression of LilrB2 and the co-expression of human LOTUS and LilrB2 (FIG. 8b). From this, it was found that in this experiment, human LOTUS inhibits the binding of Aβ-LilrB2 without affecting the expression level of LilrB2. Next, an experiment was conducted using pNPP for quantitative analysis. According to the pNPP method, the binding of Aβ was inhibited by approximately 40% in the co-expression of LOTUS and LilrB2 compared to the single expression of LilrB2 (FIG. 8c). From these results, it was found that human LOTUS inhibits the binding of Aβ and LilrB2. Example 4: Promoting effect on synapse formation in LOTUS-overexpressing (LOTUS-Tg) mice [Materials and methods] Primary culture method of hippocampus The primary culture method of hippocampal neurons was performed with some modifications referring to existing reports (Banker G.A. and Cowan W.M. Brain Res. 126(3), 397-425, 1977.). Mice of each genotype of WT and LOTUS-TG were deeply anesthetized with isoflurane (Pfizer), and the fetuses (E17.5) were removed. The hippocampi were removed and dispersed at 37 °C for 12 minutes using 0.25% trypsin and 100 μg / ml DNase. The dispersed cells were 0.5×10 5They were seeded in a 24-well dish at cells / well. Neurobasal medium (Gibco) containing 10% FBS (Biowest) was used as the cell culture introduction medium, and 1×B-27 (Gibco), 1×Glutamax (Gibco), and Neurobasal medium (Gibco) were used as the maintenance medium, respectively. Fluorescent immunocytochemistry On the 14th day of culture, the primary hippocampal cultured cells were fixed with methanol at -20°C for 8 minutes and blocked with 1% BSA / PBS for 20 minutes. Then, Mouse anti-PSD-95 antibody (1 / 1000), Rabbit anti-Bassoon antibody (1 / 1000), and Chicken anti-MAP2 antibody (1 / 1000) diluted with 1% Bovine Serum Albumin (BSA: Nacalai Tesque) / PBS were used as primary antibodies. After reacting the primary antibodies at room temperature for 1 hour, they were washed with PBS, and Alexa Fluor488 Goat anti-Mouse IgG (1 / 2000), Alexa Fluor 594 Goat anti-Rabbit IgG (1 / 2000), and Alexa Fluor 647Goat anti-Chicken IgY (1 / 2000) diluted with 1% BSA / PBS were used as secondary antibodies, and the secondary antibody reaction was carried out at room temperature for 1 hour. Then, the cells were washed with PBS and mounted using Fluoromount (Cosmo Bio). Analysis of synapse density in primary hippocampal cultured cells All fluorescent immunostaining images were acquired using a confocal microscope (TCS SP8: Leica) and Las X software (Leica). The particles with the co-localization of PSD-95 and Bassoon within 40 μm from the branch point closest to the cell body of the MAP2-positive dendrites were counted, and the synapse density per 10 μm of dendrites in each cell was measured. Analysis of dendritic spine density using mouse brain sections Male mice (2 months old) were deeply anesthetized with isoflurane and perfused with 4% PFA / PBS. Then, the brains were removed and immersed in 4% PFA / PBS overnight. Subsequently, the brains were immersed in 30% sucrose. Then, 30-μm-thick coronal sections were prepared using a cryostat. Fluorescent images were acquired using a confocal microscope (TCS SP8) with LAS X software. Spine density was semi-automatically measured using Neuron Studio software (Rodriguez, A., et al., PLOS ONE 3 e1997, (2008)). Spine density was measured with thin type for those with a head-to-neck diameter ratio of 1.1 or more and a maximum head diameter of 0.35 μm or less, mushroom type for those with a head-to-neck diameter ratio of 1.1 or more and a maximum head diameter of 0.35 μm or more, and stubby type for those with a head-to-neck diameter ratio of 1.1 or less. The spine density at the first branching site of the apical dendrite or basal dendrite from hippocampal CA1 pyramidal neurons was quantified. Behavioral analysis ・Social recognition memory task The social recognition memory task is a behavioral analysis that evaluates social recognition memory, which is hippocampus-dependent memory (Kogan, J. H., et al., Hippocampus 10, 47-56, (2000).; Ishikawa, R., et al., Hippocampus 24, 784-793, (2014)). First, as training, a young mouse (male, 2-3 weeks old), which was a new individual that the adult mouse (male, 2 months old) had never met before, was allowed to meet the adult mouse in its cage for 3 minutes, and the time (I.T.: Investigation time) that the adult mouse touched the nose of the young mouse and sniffed was measured as the time required for individual recognition. After 24 hours, as a test, the I.T. was measured again using the same combination of adult and young mice. If the I.T. at the test was significantly decreased compared to that at the training, it was judged that the adult mouse remembered the young mouse. ・Morris water maze task The Morris water maze task was conducted to evaluate spatial-dependent memory, which is hippocampus-dependent memory (Morris, R. G. Learn. Motiv. 12, 239-260, (1981).). Male mice (2 months old) were trained twice a day for 1 minute for a total of 6 days to learn spatial memory. Tests were conducted 24 hours after the training on the 3rd and 6th days. During the test, the platform was removed and the mice were allowed to swim freely for 1 minute. The residence time in each section during the test was measured to evaluate the memory formation ability. Statistical analysis Verification of statistically significant differences was performed using J-STAT software. Two-way repeated ANOVA was used for the escape latency in the Morris water maze task. Also, the residence time in the TQ section of the Morris water maze task was analyzed using a χ 2 test and one-way ANOVA with post-hoc Steel-Dwass. [Results] LOTUS antagonizes Nogo and increases the spine density of cultured hippocampal neurons Previous reports have shown that Nogo reduces synaptic density in primary cultured hippocampal neurons (An et al., Journal of Cell Science, 2016, 129(6), 1198 - 1209). LOTUS is expressed in the synaptic region including both the presynaptic and postsynaptic parts, and it has been reported that synaptic density decreases when LOTUS is deficient (Nishida et al., Scientific reports, 2021, 11(1), 1 - 9). Therefore, by immunostaining the postsynaptic protein marker PSD - 95, we investigated whether exogenously introduced LOTUS antagonizes Nogo and affects spine density. Although there is also a membrane - bound form of LOTUS, in this experiment, the soluble form of LOTUS (s - LOTUS) was used for exogenous introduction. Cultured hippocampal neurons from WT mice were treated with Nogo - 66 and s - LOTUS at DIV12, and after 48 hours, double - immunostained with PSD - 95 - positive sites on dendrites and MAP2, a dendrite marker, and measured as synaptic sites (microscopic image data are omitted). Administration of Nogo - 66 decreased the spine density of PSD - 95 compared to the control (Figure 9). Co - administration of Nogo - 66 and s - LOTUS restored the decrease in PSD - 95 - positive spine density to the same level as the control. Interestingly, the PSD - 95 - positive spine density also increased with s - LOTUS alone. These results indicate that s - LOTUS antagonizes Nogo and thereby increases the spine density of cultured hippocampal neurons. Overexpression of LOTUS increases the synaptic density of cultured hippocampal neurons LOTUS binds to NgR1 and suppresses Nogo signaling (Sato et al., 2011, Science, 333(6043), 769-773.). A decrease in Nogo signaling is known to increase synaptic density (Wills et al., Neuron, 2012, 73(3), 466-481.; Zagrebelsky et al., Neurobiology of learning and memory, 2017, 138, 154-163.). Therefore, the effect of overexpression of LOTUS on synaptic density was examined. Primary cultured hippocampal neurons from WT mice and LOTUS-Tg mice were immunostained with PSD-95 as a postsynaptic marker, bassoon as a presynaptic marker, and MAP2 as a dendritic marker at DIV14, and synapses on dendrites were identified to measure synaptic density (Figures 10a-d). As a result, the synaptic density was significantly increased in the neurons of LOTUS-Tg mice compared with that of WT mice (Figure 10e). These results indicate that overexpression of LOTUS promotes synaptogenesis and increases synaptic density. The spine density is increased in the hippocampal CA1 region of LOTUS-Tg mice Since the deficiency of LOTUS reduces the spine density in the hippocampal CA1 region (Nishida et al., supra 2021), overexpression of LOTUS may also affect spine density. Therefore, we investigated the effect of LOTUS overexpression on dendritic spine density and its morphology in the hippocampal CA1 region of adult mice at 2 months of age. WT mice and LOTUS-Tg mice were crossed with Thy1-EGFP mice, and dendritic spines of WT mice and LOTUS-Tg mice were examined by observing EGFP-positive dendrites. The total number of spines in the dendrites at the apical side of hippocampal CA1 pyramidal neurons was higher in LOTUS-Tg mice than in WT mice (Figs. 11a, b). Furthermore, in LOTUS-Tg mice, the number of thin-type and mushroom-type spines was also higher than in WT mice, but there was no difference in the number of stubby-type spines (Figs. 11a, b). The total number of spines was also increased in LOTUS-Tg mice. Similar measurements were also performed on neurons at the basal side of dendrites, and the results were the same (Figs. 11c, d). These results showed that overexpression of LOTUS increases spine density in the hippocampal CA1 region of young adult mice. Overexpression of LOTUS enhances memory To investigate whether overexpression of LOTUS affects learning and memory functions, we first performed a social cognition test. This behavioral analysis evaluates hippocampus-dependent social cognitive memory formation in mice. In this experiment, mature test mice (2 months old) were allowed to interact with unfamiliar young mice for 1.5 minutes, and 24 hours later, it was determined whether the test mice remembered the young mice. As a result, the investigation time on the second day was significantly reduced in LOTUS-Tg mice compared to the first day, whereas no significant decrease was observed in WT mice (Fig. 12a). Furthermore, the recognition index, which is the ratio of the social investigation time on the second day to the social investigation time on the first day, was lower in LOTUS-Tg mice than in WT mice, suggesting that LOTUS-Tg mice had enhanced memory formation compared to WT mice (Fig. 12b). These results suggested that overexpression of LOTUS enhances social cognition-related memory in mice. Next, the Morris water maze test was used to evaluate hippocampus-dependent spatial learning and memory. In LOTUS-Tg mice, after 3 days of training, with the platform removed, the residence time in the TQ area was significantly longer than that in other areas (chi-square test; Figure 13a). On the other hand, no difference was observed in WT mice. Furthermore, the proportion of time spent in TQ was significantly higher in LOTUS-Tg mice than in WT mice (Figure 13b). There was no difference in the body weight and swimming speed between LOTUS-Tg mice and WT mice. These results suggest that spatial learning and memory are enhanced in LOTUS-Tg mice. From the above results, it was suggested that overexpression of LOTUS may enhance hippocampus-dependent memory formation abilities such as social cognitive memory and spatial learning. Overexpression of LOTUS prevents memory dysfunction associated with aging It has been reported that the expression level of LOTUS decreases with aging, and memory impairment develops accordingly (VanGuilder et al., 2013). Furthermore, we have clarified that LOTUS-Tg mice enhance memory (Figures 12 and 13). Therefore, we investigated whether LOTUS-Tg mice have less memory impairment associated with aging. The expression of LOTUS in the hippocampus of aged mice was examined by Western blotting. As a result, it was found that the expression level of LOTUS in WT mice was significantly lower in 18-month-old (aged) mice than in 2-month-old (young) mice (Figures 14-1a, b). However, no significant difference was observed in the expression level of LOTUS in LOTUS-Tg mice (Figures 14-1a, c). The LOTUS expression level in aged LOTUS-Tg mice was approximately 1.5 times that of young WT mice (Figure 14-1c). On the other hand, when the expression level of NgR1 in the hippocampus was quantified, in both WT mice and LOTUS-Tg mice, the expression level of NgR1 tended to decrease with aging. Furthermore, in both WT mice and LOTUS-Tg mice, no change in the expression level of Nogo due to aging was observed (Supplementary Figure S1 in Figure 15). To evaluate the relationship between the decrease in LOTUS expression level and the change in spine density in the hippocampal CA1 region with aging, the spine densities of WT mice and LOTUS-Tg mice were compared. As a result, it was shown that in old-aged LOTUS-Tg mice, the spine density was higher in both apical dendrites and basal dendrites compared to old-aged WT mice (Figure 14-2d-g). Next, the hippocampus-dependent social memory of old-aged mice was evaluated by a social recognition test. In this experiment, young WT mice at 2 months of age can acquire memory in a 3-minute experiment (Nishida et al., 2021). As a result, there was no difference in the investigation time between the first day and the second day in old-aged WT mice at 1.5 years old, suggesting cognitive memory impairment in old-aged WT mice (Figure 14-3h). However, in LOTUS-Tg mice, a significant decrease in the investigation time was observed. Since this was observed not only in young mice but also in old-aged mice, it was suggested that old-aged LOTUS-Tg mice do not have hippocampus-dependent cognitive memory impairment (Figure 14-3i). From these results, it was suggested that old-aged LOTUS-Tg mice retain the ability of hippocampus-dependent memory formation because the expression of LOTUS and the spine density in the hippocampal CA1 region are maintained. Thus, it is inferred that the overexpression of LOTUS helps maintain the LOTUS level in the aging brain, thereby preventing the decrease in spine density in the hippocampus and age-related senile memory impairment (senile amnesia). Example 5: Novel Object Recognition Test (NORT) [Materials and Methods] APP NL-G-F mice Knock-in mice with gene mutations inserted into the amyloid-β region of the mouse App gene. In addition to humanizing the mouse amyloid-β sequence, single Swedish mutations, double mutations with Iberian mutations, and triple mutations with Arctic mutations of familial Alzheimer's disease mutations were introduced. Homozygous mice are viable and fertile. It increases the production ratio of toxic amyloid-β species (Aβ42) and forms amyloid plaques from an early age. APP NL-G-F homozygous mice form amyloid plaques in the brain from 2 months of age. Along with the formation of amyloid plaques, neuroinflammation and synaptic loss are observed. Furthermore, APP NL-G-F knock-in mice show behavioral abnormalities in the Y-maze from 6 months of age. An important model mouse in Alzheimer's disease (AD) research. Novel object recognition test (schematic diagram shown in Fig. 16) Day1 Separate the mice individually in cages and leave them standing for 1 hour. Place the same object in the field (460 mm × 460 mm) and let the mice freely explore it for 10 minutes, then return them to the breeding cage. After each individual analysis, clean the field and the object with 70% ethanol. Day2 Separate the mice individually in cages and leave them standing for 1 hour. Place the same object as on Day1 in one corner of the field and a new object in the other corner, and let the mice freely explore them for 10 minutes, then return them to the breeding cage. After each individual analysis, clean the field and the object with 70% ethanol. Measure the exploration time for the objects and evaluate the memory function. [Results] In wild-type (WT), since the exploration time for the novel object was significantly longer than that for the familiar object (the same object as on Day1) on Day2, it was confirmed that the object was remembered. In AD mice (APP-KI mice), since there was no difference in the exploration time for the two objects, it was found that the object was not remembered. On the other hand, in mice obtained by crossing AD mice and LOTUS-overexpressing mice (APP / LOTUS-Tg), it was found that the object was remembered in the same way as WT. From these results, it was found that increasing the expression level of LOTUS improved the decline in memory function confirmed in APP-KI mice. That is, it was found that LOTUS improves the AD-like pathological conditions (memory impairment) observed in AD mice. Production Example 1: Production of Excitatory Neurons Derived from Human Pluripotent Stem Cells <Cells> As the human pluripotent stem cells (hPSCs), commercially available products or those prepared by oneself are used. <Kit to be Used> Quick-Neuron (trade name) Excitatory - SeV Kit (Small) (ELIXIRGEN SCIENTIFIC) Components of the kit: QN-SeV, Component N, Component P, Component G1, Component G2, and Coating Agent A <Required Reagents> Prepare the reagents described in Table 3. The cell dissociation reagent Solution D1 is purchased from ELIXIRGEN SCIENTIFIC. <Medium to be Prepared in Advance> Medium N (composition as shown in Table 4) <Method> I. Coating of Plates (Performed 3 Days before Cultivation) 1. Mix the following components in a 15 ml conical tube to prepare diluted Coating Agent A. (6.0 μl of Coating Agent A, 1.8 ml of PBS at 4°C) 2. Add 400 μl / well of the diluted Coating Agent A to each well. 3. Incubate the plate at 4°C (4°C, 3 Days). II. Day0 1. Mix the following components in a 15-ml conical tube to prepare Medium iN (2.5 ml of Medium N and 2.5 μl of ROCK inhibitor). Store the remaining Medium N at 4°C for later use. 2. Thaw QN-SeV-P on ice. 3. Discard the old medium from the hPSC culture and add 2 ml of PBS to each well to be harvested. 4. Rock the plate three times, aspirate the PBS from the culture, and add 300 μl of cell dissociation reagent Solution D1 to each well. Store the remaining Solution D1 at 4°C for use on day 3. 5. Incubate the culture plate at 37°C and 5% CO2 for 5 minutes. 6. Remove Solution D1 and add 1 ml of Medium iN to the well. 7. Pipette the medium on the well bottom 8 - 15 times to disperse and detach the cells. 8. Using the same pipette tip, collect the cell suspension into a 1.5-ml tube. 9. Count the cells and measure the viability. 10. Take out the required amount (a total of 2.2x10 5 cells) of the cell suspension for 4 wells and add 10% extra. Transfer this cell suspension to a 15-ml conical tube. 11. Adjust the volume of the cell suspension to 110 μl with Medium iN. 12. Add 55 μl of QN-SeV-P to the hPSCs and tap 2 - 3 times with your finger to mix. 13. Incubate the cell suspension at 33°C and 5% CO2 for 10 minutes. Tap with your finger every minute. 14. Adjust the cell suspension to 1.1 ml with Medium iN. 15. Aspirate the diluted coating agent A one well at a time and add 250 μl of the cell suspension. 16. Quickly move the plate back and forth and from side to side 5 times each to evenly disperse the treated cells. Evenly disperse the treated cells in the culture medium. 17. Incubate the culture plate overnight at 33 °C and 5% CO2. III. Day1 1. Prepare Medium N (G1) by mixing the following components in a 15 ml conical tube. (4.4 ml of Medium N, 8.8 μl of Component G1 of the kit) 2. Add puromycin to Medium N (G1) at an appropriate concentration. 3. Pipette out most of the medium from each well and add 500 μl of Medium N (G1) with puromycin added. 4. Incubate the culture plate overnight at 33 °C and 5% CO2. IV. Day2 1. Warm Medium N (G1) with puromycin added at room temperature for 20 - 30 minutes. 2. Remove most of the medium from each well and add 500 μl of Medium N (G1) with puromycin added. 3. Incubate the culture plate overnight at 37 °C and 5% CO2. V. Day3 1. Immerse the tips of a 12 mm glass coverslip and forceps in 100% ethanol for 3 minutes. 2. Air-dry each coverslip for 1 minute or until completely dry, one by one, and place them into the wells of a 24-well plate using sterilized ethanol. 3. Vortex ornithine briefly and centrifuge at maximum speed for 1 minute. 4. Add 300 μl of ornithine to the surface of each glass coverslip or well. 5. Incubate the plate at 37 °C and 5% CO2 for at least 2 hours. 6. Thaw laminin and add 15 μl of laminin to cold PBS. Mix well. Note: All PBS washes are performed by dropping room temperature PBS. Cold PBS is only used for coating. 8. Aspirate the supernatant from each coverslip / well and add 500 μl of PBS. 9. Repeat step 8. 10. Aspirate PBS from each coverslip / well and add 300 μl of diluted laminin. 11. Incubate the plate at 37 °C and 5% CO2 for at least 2 hours. 12. While the laminin is incubating, prepare Medium N (G2P) (5.5 ml of Medium N, 5.5 μl of Component G2 from the kit, and 2.8 μl of Component P). Place it in a 15 ml conical tube. 13. After incubation of the laminin, remove from each coverslip or well 14. Wash twice with 500 μl of PBS 15. Add 300 μl of Medium N (G2P) to each well or coverslip. 16. Incubate the plate at 37 °C and 5% CO2 until the cells are ready to be plated. 17. Remove the old medium from the well by pipetting and add 500 μl of PBS. 18. Withdraw PBS from the well and add 80 μl of Solution D1. 19. Rock the plate three times to spread D1 evenly. 20. Incubate the culture plate at 37 °C and 5% CO2 for 3 minutes. 21. Carefully withdraw Solution D1 from the well with a P200 pipettor and add 200 μl of Medium N (G2P). 22. Pipette up and down 6 - 8 times with a P200 pipettor to detach the cells and quickly disperse the medium on the bottom of the well. 23. Using a P200 pipettor, slowly pipette the cell suspension up and down in the well up to 5 times to break up cell aggregates. 24. Recover 200 μl of the cell suspension from the well with a P200 pipettor set to 100 μl and transfer 100 μl each to glass coverslips coated with ornithine and laminin. 25. Incubate the culture plate overnight at 37°C in 5% CO2. VI. Day4 1. Withdraw the Medium from each well and add 800 μl of Medium N (G2P). 2. Incubate at 37°C in 5% CO2 for 3 days. VII. Day7 1. Withdraw 400 μl of the old medium from each well and add 400 μl of Medium N (G2P) to each well. 2. Incubate at 37°C in 5% CO2 for 3 days. VIII. Day10 It can be used as mature excitatory neurons. After day 10, the differentiated neurons can be maintained in a maintenance medium (recommended: Quick-Neuron (trade name) Excitatory - Maintenance Medium from ELIXIRGEN SCIENTIFIC, catalog number EX-MM). Differentiation into excitatory neurons can be confirmed using anti-TUBB3 antibody and anti-vGLUT1 antibody. Production Example 2: Production of oligodendrocyte progenitor cells derived from human pluripotent stem cells Oligodendrocyte progenitor cells (OPCs) derived from human pluripotent stem cells (hPSC) can be produced by the method described in Douvaras and Fossati, Generation and isolation of oligodendrocyte progenitor cells from human pluripotent stem cells. Nat Protoc 10, 1143-1154 (2015). The specific production method is described below. <Medium Preparation> mTeSR1 medium Add penicillin-streptomycin and mTeSR1 supplement (StemCell Technologies, cat. no. 05850) to the mTeSR basal medium to make the final concentration of all components 1x. mTeSR custom medium Add mTeSR custom supplement (StemCell Technologies, customized) and penicillin-streptomycin to the mTeSR basal medium to make the final concentration of all components 1x. Neural induction medium Add 10 μM SB431542, 250 nM LDN193189, and 100 nM RA to the mTeSR custom medium on the day of use. The mTeSR custom medium can be replaced with a basal medium containing 25 μg / ml insulin. Basal medium Add NEAA (MEM non-essential amino acids solution, 100×; Life Technologies, cat. no. 11140-050), GlutaMAX (100×; Life Technologies, cat. no. 35050079), 2-mercaptoethanol, and penicillin-streptomycin to DMEM / F12 (Life Technologies, cat. no. 11320082) to make the final concentration of each component 1x. N2B27 medium Add N2 supplement (Life Technologies, cat. no. 17502-048) and B27 supplement (Life Technologies, cat. no. 12587-010) to the basal medium to make the final concentration of each component 1x. Add 25 μg / ml insulin. Add 100 nM RA and 1 μM SAG on the day of use. Glial medium Prepare with the following composition. <Differentiation induction method> Procedure 1: Preparation of hPSCs (4 - 5 days) [1] Partially thaw a cryovial (1 mL volume) containing hPSCs in a 37°C water bath over 1 - 2 minutes. [2] Slowly add 1 mL of mTeSR1 medium into the cryovial, and transfer the total 2 mL of cell suspension into a 15 mL tube. [3] Add mTeSR1 medium into the above 15 mL tube and make up to 10 mL. ↓ Centrifuge at 200 g for 4 minutes at 20 - 23 °C (room temperature) [4] Remove the supernatant and resuspend the cell pellet in 2 mL of mTeSR1 + 10 μM Y27632 (ROCK inhibitor) medium. [5] Seed the suspended cells onto a 6 - well plate coated with Matrigel (BD Biosciences, cat. no. 354277). ↓ Incubate in a 37 °C 5% CO2 incubator for 24 hours [6] Remove the medium and add 2 mL of mTeSR1 medium. [7] Incubate in the same way and change the medium once a day. [8] When 70 - 90% confluent, remove the medium and add 1 mL of pre - warmed Accutase (Life Technologies, cat. no. A11105 - 01). ↓ Incubate at 37 °C 5% CO2 for 5 minutes [9] Add 2 mL of DMEM / F12 medium (Life Technologies, cat. no. 11320082).

[0010] Use a p1000 pipetteman to gently pipette 2 - 5 times to fully dissociate hPSC colonies into single cells.

[0011] Add the cell suspension into a 15 mL tube and further add 5 mL of DMEM / F12. ↓ Centrifuge at 200 g for 4 minutes at 20 - 23 °C (room temperature)

[0012] Remove the supernatant and resuspend the cell pellet in 1 mL of mTeSR1 + 10 μM Y27632 medium. ↓ Count the number of cells Prepare a Matrigel-coated 6-well plate and add 1.5 mL of mTeSR1 + 10 μM Y27632 medium.

[0014] At 8×10 4 ~1×10 5 seed cells per well. ↓ Incubate for 24 hours in a 37°C, 5% CO2 incubator

[0015] Remove the medium and add 2 mL of mTeSR1 medium.

[0016] Culture the cells until the diameter of the hPSC colonies reaches 100 - 250 μm (1 - 2 days). Procedure 2: OLIG2 + Inducing differentiation into progenitor cells (for 12 days)

[0017] When the hPSC colonies reach a diameter of 100 - 250 μm, remove the medium and add 2 mL of Neural induction medium to each well. (This is day 0 at this point) * By adding RA at a low concentration (100 nM) from day 0 of differentiation induction, the yield of OLIG2 + progenitor cells is significantly improved. ↓ Incubate for 8 days in a 37°C, 5% CO2 incubator * Change the medium once a day. At this time, use fresh RA, SB431542, and LDN193189 each time.

[0018] Exchange the medium with N2 medium. Change the medium once a day. * By day 8, the cells will become confluent, and by day 12, the cells will form a 3D structure. The 3D structure can be clearly confirmed and becomes an important checkpoint for subsequent differentiation operations. * When changing the medium, use fresh RA and SAG each time. * Due to the rapid expansion of the cells and the increase in cell number, the medium will become yellowish. (Medium change is necessary every day to appropriately supply the nutrients required by the cells!) Procedure 3: Cell Separation and Formation of OLIG2-Enriched Aggregates - OLIG2 after Enzymatic Digestion into Single Cells + Cell Aggregation (for 18 days) → Only OLIG2+ cells aggregate into spheres

[0019] Remove the medium and add 1 mL of pre-warmed Accutase. ↓ Incubate at 37°C, 5% CO2 for 5 minutes

[0020] Add 2 mL of DMEM / F12 medium.

[0021] Gently pipette 2 - 5 times with a p1000 pipetteman to make single cells sufficiently.

[0022] Add the cell suspension to a 15 mL tube and further add 5 mL of DMEM / F12. ↓ Centrifuge at 200g for 4 minutes at 20 - 23°C (room temperature)

[0023] Remove the supernatant and add 1 mL of N2B27 medium to resuspend the cell pellet.

[0024] Distribute the cell suspension into 2 wells of an ultra-low attachment 6-well plate.

[0025] Add 3 mL of N2B27 medium. ↓ Culture in a 37°C, 5% CO2 incubator for 2 days

[0026] Add the entire volume of the medium containing cell aggregates into a 15 mL tube. ↓ Centrifuge at 100g for 2 minutes at 20 - 23°C (room temperature)

[0027] Remove 2 / 3 of the medium volume and add 2 mL of N2B27 medium.

[0028] Return the aggregates to the same ultra-low attachment plate and redistribute the number of aggregates using a pipette so that each well has approximately the same number.

[0029] Perform operations

[0026] -

[0028] every other day until DIV-20 when differentiation is reached.

[0030] On the 20th day, add the cell aggregates to a 15 mL tube and wait for about 3 minutes (until the aggregates sink to the bottom of the tube).

[0031] Remove 2 / 3 of the medium and add PDGF medium.

[0032] Gently pipette 5 times with a P1000 pipetteman.

[0033] Return the aggregates to the same ultra-low attachment plate and redistribute the number of aggregates using a p1000 pipette so that each well has approximately the same number.

[0034] Perform operations

[0030] -

[0033] every other day until the 30th day. Procedure 4: Selection and plating of aggregates (1-4 hours)

[0035] On the 30th day, under sterile conditions, use a microscope and a p200 pipetteman to collect round aggregates with a diameter of 300-800 μm that appear black in the center and gold or brown in color. Procedure 5: Differentiation into OPCs by adherent culture (15-60 days)

[0036] Plate at 20 spheres / well in a 6-well plate coated with Poly-L-ornithine and Laminin. → 2 spheres are plated per 1 cm 2 (No passage is required, and it will become confluent across the well around the 60th day).

[0037] Add 3 mL of glial medium and rotate the plate to disperse the aggregates. ↓ Incubate in a 37°C 5% CO2 incubator

[0038] Every other day, carefully replenish 2 / 3 of the medium with fresh glial medium until the 55th day. → On the 55th day, O4 ＋ Cells can be visualized by live O4 staining or isolated by FACS. → Culturing is kept in glial medium until the 75th day, which can enhance the efficiency of O4+ cells. → Medium replacement is carried out as gently as possible. The cell aggregates should always be covered with liquid, and do not tilt the plate to aspirate the old medium. When aspirating the old medium, place the P1000 pipetteman near the wall of the well and aspirate gently to avoid detaching the cells. Especially after the 40th day, to avoid cell separation, do not vibrate or move the plate as much as possible.

Claims

1. A preventive or therapeutic agent for dementia, comprising as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof.

2. The therapeutic agent according to claim 1, wherein the dementia is Alzheimer's disease.

3. An enhancer of memory and / or cognitive function, comprising as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof.

4. An agent for inhibiting the synapse-eliminating action of amyloid-beta protein, comprising as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof.

5. An inhibitor of amyloid-beta protein production, comprising as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof.

6. An accelerator of amyloid-beta protein clearance, comprising as an active ingredient Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing Crtac1B protein or a C-terminal region fragment thereof.

7. The agent according to any one of claims 1 to 6, wherein the Crtac1B protein is a polypeptide having an amino acid sequence with 95% or more identity to the amino acid sequence shown in SEQ ID NO: 2, and the C-terminal region fragment is (i) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 7, (ii) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 9, (iii) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 11, or (iv) a polypeptide having 90% or more sequence identity to the protein fragments of (i) to (iii).

8. The agent according to any one of claims 1 to 7, wherein the cell expressing the Crtac1B protein or its C-terminal region fragment is a neural stem / progenitor cell, an excitatory neuron, or an oligodendrocyte progenitor cell.

9. A method for treating dementia, comprising administering to a dementia patient a Crtac1B protein or its C-terminal region fragment, a vector capable of expressing the Crtac1B protein or its C-terminal region fragment, or a cell expressing the Crtac1B protein or its C-terminal region fragment.

10. The method according to claim 9, wherein the dementia is Alzheimer's disease.

11. A method for enhancing memory and / or cognitive function, comprising administering to a patient in need of enhancing memory and / or cognitive function a Crtac1B protein or its C-terminal region fragment, a vector capable of expressing the Crtac1B protein or its C-terminal region fragment, or a cell expressing the Crtac1B protein or its C-terminal region fragment.

12. The method according to claim 11, wherein the patient is an elderly person whose memory and / or cognitive function has declined due to aging, a patient having amnesia or forgetfulness, a patient with mild cognitive impairment, or a dementia patient.

13. A method for inhibiting the synapse-eliminating action of amyloid-beta protein in a patient, comprising administering to the patient a Crtac1B protein or its C-terminal region fragment, a vector capable of expressing the Crtac1B protein or its C-terminal region fragment, or a cell expressing the Crtac1B protein or its C-terminal region fragment.

14. The method according to claim 13, wherein the patient is a patient with dementia or a patient having an accumulation of Aβ protein in the brain.

15. The method according to claim 14, wherein the patient is a patient with Alzheimer's dementia.

16. A method for inhibiting the production of amyloid beta protein in a patient, comprising administering to the patient a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

17. The method according to claim 16, wherein the patient is a patient with dementia or a patient having an accumulation of Aβ protein in the brain.

18. The method according to claim 17, wherein the patient with dementia is a patient with Alzheimer's dementia.

19. A method for promoting the clearance of amyloid beta protein in a patient, comprising administering to the patient a Crtac1B protein or a C-terminal region fragment thereof, a vector capable of expressing the Crtac1B protein or a C-terminal region fragment thereof, or a cell expressing the Crtac1B protein or a C-terminal region fragment thereof.

20. The method according to claim 19, wherein the patient is a patient with dementia or a patient having an accumulation of Aβ protein in the brain.

21. The method according to claim 20, wherein the patient with dementia is a patient with Alzheimer's dementia.

22. The method according to any one of claims 9 to 21, wherein the Crtac1B protein is a polypeptide having an amino acid sequence with 95% or more identity to the amino acid sequence shown in SEQ ID NO: 2, and the C-terminal region fragment is (i) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 7, (ii) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 9, (iii) a Crtac1B protein fragment containing the amino acid sequence shown in SEQ ID NO: 11, or (iv) a polypeptide having 90% or more sequence identity to the protein fragments of (i) to (iii).

23. The method according to any one of claims 9 to 22, wherein the cells expressing the Crtac1B protein or a C-terminal region fragment thereof are neural stem / progenitor cells, excitatory neurons, or oligodendrocyte progenitor cells.

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