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It may be possible to correct genetic defects that cause deafness at birth in another ten years. That is the prognosis from the scientists behind a recent breakthrough in using gene therapy to correct congenital deafness in a strain of lab mice.
These animals are a realistic animal model of the mutations that cause inherited deafness in 4-8% of children.
According to The Independent, of the 70 different genes known to cause deafness when mutated, the scientists chose the one responsible for the most frequently occurring types of deafness. Called TMC1, this gene plays a key part in the conversion of sound waves into electrical signals that are then transported by auditory nerves.
Healthy copies of the TMC1 gene were inserted into the cells of the inner ear in mice that had an inherited condition where both copies of the gene were deleted. This is similar to the condition faced by children who are born deaf, where they inherit two defective copies of the TMC1 gene. One defective gene has been passed on to them from each parent.
When the mice were tested afterward, results showed that the sensory “hair cells” in their inner ear could convert sound into electrical signals which could be sent to the brain. The mice seemed to hear loud noises just as well as normal, healthy mice did. Mice with the gene defect that were not treated, however, showed no reaction to the loud noise.
“Mice with TMC1 mutations will just sit there, but with gene therapy, they jump as high as a normal mouse,” said Jeffrey Holt of Boston Children’s Hospital and Harvard Medical School, who led the study published in the journal Science Translational Medicine.
“Our gene therapy protocol is not yet ready for clinical trials. We need to tweak it a bit more, but in the not-too-distant future, we think it could be developed for therapeutic use in humans,” Holt said. “I can envision patients with deafness having their genome sequenced and a tailored, precision medicine treatment injected into their ears to restore hearing.”
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