Someday, it may be possible to cure children of deafness caused by a gene defect.
Researchers at Boston’s Children’s Hospital in Massachusetts are developing a cure for inherited deafness by introducing a working copy of a hearing gene.
The defective gene is located in the inner ear. Researchers engineered a harmless cold virus to deliver the corrected gene deep inside the ear canal.
“Our strategy was to take a viral vector, remove the viral genes so that it doesn’t make anyone sick, and to replace those with the correct DNA sequence for TMC1,” said Jeffrey Holt, lead researcher on the project
The gene, TMC1, is essential for hearing. It encodes proteins that convert sound into electrical signals the brain can recognize and process.
“We found that we can restore function in both cases for recessive and dominant forms of TMC1 mutations,” he said.
Recessive or dominant forms of deafness depend upon whether the defective hearing gene is inherited from one or both parents.
To see whether their genetic repair worked, researchers used two types of deaf mice — each a model of dominant and recessive hearing loss.
They used the cold virus, known as adeno-associated virus, to carry a functioning TMC1 gene into the inner ears of the mice.
Researchers found they could repair the mutated hearing gene; but, to tell whether the treated mice could actually hear, they had to put the rodents in a specially designed chamber with sensors that played really loud noise.
“We can’t really ask a mouse if they are able to hear but we can play a loud, sudden sound and a normal mouse will jump in response to that," said Holt. "A deaf mouse does not move at all, but after our gene therapy treatment, the deaf mice began to jump.”
One in 1,000 people goes deaf in adolescence, according to Holt. He said inherited deafness can be caused by any one of 70 genes.
Researchers say they hope the genetic technique that helped the deaf mice to hear can cure all inherited forms of deafness in children.