Over 50 new hearing genes found

Researchers have discovered 52 new genes essential for hearing in mice.

The discovery may help scientists understand the genetic component of hearing loss in humans, as well as providing new avenues of research for understanding the mammalian hearing system.

Importantly, the large number of hearing loss genes identified in this study demonstrates that there are many more genes involved in deafness in mouse and human genomes than we had previously realised,' said Professor Steve Brown, director of the Medical Research Council (MRC) in Harwell and senior investigator for this study.

The MRC Harwell forms part of the International Mouse Phenotyping Consortium (IMPC). The IMPC aims to identify the function of each gene in the mouse genome by generating 'knockout' mice, in which a single gene is inactivated and the impact on the mouse's health is assessed.

Over 3000 strains of knockout mice were screened and, of the 67 strains found to have impaired hearing, 52 arose from the inactivation of genes not previously associated with hearing.

'These increase our knowledge of the many genes and molecular mechanisms required for hearing and also provide a shortlist of new genes to investigate to discover the genetic basis of many human hearing loss syndromes,' said Professor Brown.

To assess hearing in mice, the scientists used the auditory brainstem response (ABR) test. This test uses electrodes positioned on the head to measure neural activity in response to sound, and can also be used to assess hearing in humans. Five different sound frequencies were tested, with the volume at which a neural signal is detected defining the hearing threshold at a particular frequency. The test enabled the scientists to identify mild or severe hearing impairments, as well as conditions which affected reduced hearing at only high or low frequencies.

The IMPC intends to produce a knockout mouse strain for each of the roughly 20,000 genes in the mouse genome. Following this latest study, it is expected that at least 450 genes will play a role in hearing.

Professor Brown also highlighted some of the more immediate clinical implications of the work. 'Testing these genes in people with hearing loss may help to improve diagnosis and counselling of patients,' he said.

The study was published in Nature Communications.