Hope for deaf people after scientists disable mutant mouse gene which affects hearing
Scientists have genetically changed mice so that they do not become deaf – potentially paving the way for a similar procedure on humans.
By injecting a gene “editor” directly into the ear cells of newborn rodents with deafness-causing DNA, scientists “disabled” the mutant gene that would have robbed them of hearing over time. At the age of four weeks, untreated mice were unable to hear sound at 80 decibels – about the level of city traffic.
Treated mice, however, reacted to sound at a much lower 65 decibels – the level of normal human conversation – a team of scientists in the United States and China wrote in the science journal Nature.
Some of the lab rodents, dubbed “Beethoven” mice after the German composer who became deaf mid-career, had one ear treated and the other not. In the injected ears, the researchers noticed much healthier “hair cells”. These are the cells responsible for sensing sound in humans and mice, but are killed off by a mutated version of the TMC1 gene.
“We were really excited when we observed hearing preservation in the injected ears but not the uninjected ears, of individual mice," study co-author David Liu of Harvard University said. By eight weeks, untreated mice did not respond at all to sudden, loud sounds, while treated ones were startled.
Almost half of cases of hearing loss in humans have an underlying genetic cause, according to the team. Humans with the TMC1 mutation generally start losing their hearing between the ages of five and 30, and most are deaf by the age of 50-60, said Liu.
Simon Waddington, a gene transfer expert at University College London, commented: “Hitherto incurable and often even untreatable diseases are now within the scope of gene therapy.”
