Genetic Mutations and Age-Related Hearing Loss

Although there is a large body of research devoted to genetic mutations and deafness, there's very little focused on age-related hearing loss. That may come as a surprise to some, considering that it affects more than 60 % of people over the age of 70. There will of course be some environmental causes of hearing loss, such as exposure to excessive noise levels, (had any conversations with ageing rockers lately?) and infection, but genetic mutations will also play a role.

Scientists from the Wellcome Trust Sanger Centre in the UK found a genetic mutation called Oblivion. The result was that mice had a hearing impairment that mimicked progressive hearing loss in humans. If there was a mutation on only one of the genes the mice showed a progressive hearing loss in the first three months after birth. If the genetic mutations were present on both genes, the mouse was deaf.

In the press release that accompanied the publication of the research in PLos Genetics, Prof Karen Steel, a senior author of the study said, "When we mapped the mutation to the mouse genome, we quickly found a probable cause for hearing loss."

The change in the gene that led to hearing loss was tiny, just one letter in their genetic code. In the gene Atp2b2, scientists found that when C (cytosine) was changed to a T (thymine) it stopped the production of a molecular pump that keeps the hair cells in the ear working efficiently. If only one of the genes was mutated the pump worked for a short while and then degenerated. In mice with the genetic mutation on both genes the pump never worked, even from birth.

Normal functioning hair cells inside the inner are integral for good hearing because they are the sensory receptors, and signal the reception of sound to the brain.

Any new cellular, genetic and molecular discovery reveals more about the biology of hearing. Knowing the basic fundamentals will not only improve the chances of earlier diagnosis when the biology goes wrong, but it should also suggest avenues for future therapeutic research.

Wellcome Trust Sanger Institute

http://www.sanger.ac.uk/Info/Press/2008/081031.shtml