GJB2 Gene Regulatory Elements for Inner Ear Cell Targeting
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Solution Overview
Problem
Current gene replacement therapies for GJB2-related hearing loss fail to rescue hearing, as they lead to promiscuous expression of the GJB2 gene in the inner ear, causing toxicity and damage, and are unable to specifically target cells that normally express the GJB2 gene.
Innovation Solution
An isolated nucleic acid comprising an expression cassette with GJB2 gene regulatory elements, a promoter, and a nucleotide sequence encoding the GJB2 protein, flanked by adeno-associated virus (AAV) inverted terminal repeats, which allows targeted expression of the GJB2 protein in cells that normally express it, such as connective tissue cells of the cochlea and supporting cells of the organ of Corti, while avoiding expression in hair cells and spiral ganglion neurons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GJB2 gene replacement therapy is administered, then cell survival and gap junction network are rescued, but hearing is not rescued due to promiscuous expression causing toxicity
Solution Approach 1:
The patent applies local quality by using cell-type specific promoters (e.g., Col2a1 promoter for connective tissue cells, Otx2 promoter for supporting cells) to restrict GJB2 expression to specific cell populations. This ensures that the therapeutic benefit is localized to cells that need GJB2 expression while avoiding toxic effects in other cell types, thereby resolving the contradiction between achieving cell survival and avoiding toxicity.
Solution Approach 2:
The patent changes the regulatory parameter of the GJB2 gene by replacing the original constitutive promoter with tissue-specific promoters. This parameter change transforms the expression pattern from promiscuous (all cell types) to specific (only target cell types), thereby maintaining the therapeutic effect while eliminating the harmful toxicity associated with broad expression.
2Quantity of substance
If GJB2 gene replacement therapy is administered, then gene addition is achieved, but hearing is not rescued due to inability to specifically target cells
Solution Approach 1:
The patent implements local quality by selecting and using promoters that are naturally active in specific cell types (e.g., Col2a1 for connective tissue, Otx2 for supporting cells). This ensures that the GJB2 gene is added and expressed precisely in the intended target cells, achieving both gene addition and cell-specific targeting simultaneously.
Solution Approach 2:
The patent employs self-service by utilizing the endogenous promoter activity of target cells to drive GJB2 expression. The promoters (Col2a1, Otx2, etc.) are already active in the desired cell types, so they automatically direct the therapeutic gene to the correct cells without requiring external targeting mechanisms, thereby achieving precise cell-specific targeting.
3Productivity
If promiscuous GJB2 expression is achieved, then gene expression is restored, but hearing is damaged due to toxicity in non-target cells
Solution Approach 1:
The patent applies local quality by restricting GJB2 expression to specific cell types through cell-type specific promoters. This localized expression approach ensures that the gene is expressed only where it is beneficial (in connective tissue cells and supporting cells) while preventing the harmful effects of promiscuous expression in non-target cells, thereby preserving hearing.
Solution Approach 2:
The patent converts the potential harm of promiscuous expression into a benefit by using the natural promoter activity patterns of target cells as a guide. The promoters (Col2a1, Otx2) that are naturally active in specific cell types are harnessed to achieve precise targeting, transforming what would be a harmful broad expression pattern into a beneficial specific expression pattern that protects hearing.
Data Source
AI summary
The present disclosure, at least in part, relates to compositions (e.g., isolated nucleic acid and rAAVs) and methods for treating Non-syndromic hearing loss and deafness (DFNB1) by delivering gap junction beta 2 (GJB2) protein to inner ear cells that normally express GJB2 (e.g., fibrocytes and supporting cells of the organ of Corti and nearby regions). The isolated nucleic acid of the present disclosure comprises an expression cassette, wherein the expression cassette comprises a gap junction beta 2 (GJB2) gene regulatory element (GRE) (e.g., GJB2 enhancers, GJB2 promoters, GJB2 5′ UTR, and/or GJB2 3′ UTR), and a nucleotide sequence encoding a GJB2 protein.