Connexin Hear Loss gene therapy

Hope for Connexin 26 Hearing Loss Gene Therapy?

How come that babies can be born deaf to hearing parents?  

Congenital hearing loss and Connexin 26

The expression “congenital” means that hearing loss or deafness is present at birth. The reasons of why this happens are often murky. Did something happen during pregnancy? Was the baby exposed to toxic chemicals, drugs or viral infections? Excess noise? Or might genetics be involved? 

A common reason for congenital deafness is due to mutations that affect an important protein involved in hearing called Connexin 26.  Such mutations lead to inner-ear cochlear damage and deafness. The gene responsible for the coding errors is known as GJB2. 

This is an autosomal recessive condition. Both parents can be carriers. Genetic testing and counseling are available. 

The Connexins

The Connexins are a family of special proteins located throughout the body that help cells communicate with each other in so many ways. They are known as “gap-junction” proteins. They form channels between neighboring cells, which allow for the transport and flow of ions, specialized molecules and chemicals. 

In the cochlea – the inner ear hearing organ – such vital activities are carried out by the Connexin 26 proteins. Genetic mutations of these proteins interfere with proper Connexin 26 function, which results in ion exchange issues – more specifically in disruptions of potassium recycling. As a result, potassium accumulates and eventually “poisons” cochlear structures, which in turn leads to deafness. 

Ongoing Research: Hope but Caution! 

Research looking for genetic ties to hearing loss in different populations and ethnicities  is an active and very complicated field. Lately, some Connexin 26 research news has been greeted with cautious optimism because we are still talking about experiments with mice, not humans

The biopharmaceutical company Otonomy released a report of some pre-clinical results of their experimental gene therapy drug OTO-825 in two mouse models. 

Among others, they say that “A single intracochlear administration of OTO-825 rescues expression of Connexin26 in both models. OTO-825 induces significant improvement in hearing across multiple frequencies and normalizes cochlear morphology in both models.” 

And so, when it comes to hearing loss, we are used to the mantra of managing our expectations. However, this is an example that proves that research is indeed ongoing and that there is a good chance for clinical trials relevant to human Connexin 26 deafness. Yes, there are many obstacles ahead and we have a long way to go but at least there is hope. Fingers crossed. 


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