Genetic Hearing Loss Potentially Reversible

As I've mentioned before, my research and my lab focuses on the delivery of genes to the inner ear to repair or reverse deafness. One potential method for getting these genes into surviving cells is to insert them into a modified virus which infects the healthy inner ear cells. Following infection, the cells produce the protein of interest instead of more virus. However, this method's strength is in proof of concept rather than a direct therapy.

However, a group at Emory has devised yet another way to treat genetic deafness: compensating for a missing protein. A common cause of genetic deafness in people is the lack of the protein connexin26, caused by a mutation.

"There are millions of deaf people affected by mutations in this one gene, connexin26," Dr Lin says. "Congenital hearing loss is one of the most common human genetic birth defects, and that is why in almost all the states universal newborn hearing screening is mandated by law [including Georgia]."

In people without congenital hearing loss, connexin26 and connexin30 work together to form the cochlea's hybrid junction gaps, which facilitate intercellular communication. But when one of the proteins is missing, the hybrid junction gaps fail to work, and the cochlea's hair cells die off, leaving the body incapable of translating sounds into nerve impulses.

The group added extra connexin26 to mice that were deficient in connexin30, and found that this protein can compensate for the other.

With the additional connexin26, hearing sensitivity was restored and the expected hair cell death never occurred. Those positive findings led Dr. Lin to conclude, "The problem is simply caused by not having enough protein remaining in the ear of these mutant mice to assemble gap junctions."

Now they are running experiments to test whether connexin-related deafness can be reversed in a mouse model, or if increasing connexin30 may help when connexin26 is deficient.

Hap tip Bob Abu and Andy for the story.