Conditional TDP-43 Knockout Mouse Model for ALS Research
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Solution Overview
Problem
Current models for amyotrophic lateral sclerosis (ALS) research, such as SOD1 transgenic mice and TDP-43 transgenic mice, do not adequately represent the 90% of ALS patients with TDP-43 aggregates, as they either overexpress mutant SOD1 or TDP-43, and lack a loss-of-function model specifically targeting spinal cord motor neurons, which is crucial for understanding the disease's pathogenesis.
Innovation Solution
A non-human animal model is developed with a HB9 promoter-driven Cre recombinase transgene, resulting in a Hb9-Tardbp lx/- genotype, which leads to a loss of TDP-43 function in spinal cord motor neurons, exhibiting ALS-like phenotypes including kyphosis, motor neuron loss, and accumulation of poly-ubiquitinated proteins, allowing for the study of ALS associated with loss-of-function of TDP-43.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TDP-43 transgenic mice overexpressing TDP-43 are used to model ALS, then motor neuron disease-like symptoms are reproduced, but it is unclear whether phenotypes result from loss-of-function or gain-of-toxicity
Solution Approach 1:
The invention divides the TDP-43 gene into two separate transgenic constructs: one expressing only the N-terminal domain (NTD) and another expressing only the C-terminal domain (CTD). This segmentation allows independent study of each domain's functional contribution versus toxic gain-of-function, resolving the uncertainty about whether TDP-43 phenotypes result from loss-of-function or gain-of-toxicity.
Solution Approach 2:
The invention creates transgenic mice with tissue-specific expression patterns by using different promoters (e.g., CamKIIα promoter for neuronal-specific expression). This local quality approach allows the research to focus on TDP-43 function specifically in motor neurons while leaving other tissues unaffected, providing clearer insights into the pathogenic mechanism in ALS-relevant tissues.
2Reliability
If whole-body TDP-43 knockout is performed, then embryonic lethality occurs, but this prevents study of adult motor neuron function
Solution Approach 1:
The invention segments TDP-43 expression control by creating conditional knockout mice using Cre-loxP technology. The Tardbp gene is flanked by loxP sites, allowing spatially and temporally controlled deletion. This enables whole-body viability while permitting targeted deletion in specific tissues (e.g., motor neurons) at specific developmental stages, thus resolving the contradiction between viability and research versatility.
Solution Approach 2:
The invention uses Cre-loxP technology to prepare mice with floxed TDP-43 genes in advance. These mice remain viable and healthy until Cre recombinase is administered, at which point TDP-43 is deleted in the desired tissue. This preliminary action allows the animal to develop normally first, then undergo targeted gene deletion to study adult motor neuron function without embryonic lethality.
3Reliability
If mutant SOD1 transgenic mice are used, then ALS phenotypes are reproduced, but these models do not represent the 90% of patients with TDP-43 aggregates
Solution Approach 1:
Instead of using mutant SOD1 transgenic mice that reproduce ALS phenotypes through toxic gain-of-function, the invention inverts the approach by using TDP-43 knockout or conditional knockout mice. This inverse strategy directly models the TDP-43 loss-of-function mechanism observed in 90% of ALS patients with TDP-43 aggregates, thereby improving representativeness across different ALS patient populations while still reproducing relevant ALS phenotypes.
Data Source
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AI summary
A non-human animal model for amyotrophic lateral sclerosis (ALS) is disclosed. The animal model comprises a rodent whose spinal cord motor neurons have a loss of TAR-DNA binding protein-43 (TDP-43) function and phenotypes exhibit ALS-like symptoms. A method for identifying a candidate agent for treating, preventing and/or inhibiting ALS associated with a loss-of-function of TDP-43 is also disclosed.