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Human Deafness and the Ear Hair of Mice

About six out of 10 people who are older than 70 struggle with progressive hearing loss.

Environmental factors — such as working for a lifetime in a loud factory — can contribute to the problem, but genetics also plays a crucial role. While scientists have defined many of the genes involved in childhood deafness, these genes rarely contribute to hearing loss later in life.

But now a mutation in the mouse genome that imitates progressive hearing loss in humans has been discovered by a team of researchers from the Wellcome Trust Sanger Institute in Cambridge, U.K. Working with colleagues in Munich and Padua, the researchers found that mice carrying a mutation called Oblivion showed reduced function of hair cells in the inner ear -- even before clear physical setbacks can be observed.

The study was published in the open-access journal PLoS Genetics.

The Cambridge team found that the Oblivion mutation shared much in common with forms of human deafness. The hair cells of mice with one mutant copy of the Oblivion gene functioned at first but later degenerated; mice with two mutant copies were actually born with damaged hair cells.

"When we mapped the mutation to the mouse genome, we quickly found a probable cause for hearing loss," senior author Karen Steel said in a press release. "We showed that the mutant mice carried a change in one letter of their genetic code in a gene called Atp2b2. Changing a specific C to a T in this gene stops it from producing a normal molecular pump that is needed to keep hair cells in the ear working efficiently by pumping excess calcium out of the cell."

Oblivion is unique in because it involves mutations to Atp2b2, a gene which has previously been associated with hearing loss in humans.

"One aim of identifying and characterizing mice with impaired hearing is to help us to understand the biology of this remarkable sense," says Steel. "Improving our understanding of the molecular and cellular action of genetic variants will help us to develop improved diagnostics and improved treatments for humans."