Hidden Hearing gene
A gene has been identified, mutations in which can lead to complete hearing loss
Scientists have discovered that the GAS2 gene plays a key role in amplifying sound signals in the human inner ear, which is why mutations in it often lead to complete hearing loss. This was announced on Friday by the press service of the University of Pennsylvania with reference to an article in the journal Developmental Cell (Chen et al., Cochlear supporting cells require GAS2 for cytoskeletal architecture and hearing).
"Doctors began painstakingly studying the unique structure of inner ear cells more than 150 years ago, but only now, after studying the properties of the GAS2 gene, we understand what an important role they play in the normal functioning of human hearing organs," said Douglas Epstein, professor at the University of Pennsylvania in Philadelphia (USA), whose words are quoted by the press-university service.
According to current WHO estimates, over 460 million people on Earth suffer from deafness and other forms of serious hearing impairment. A significant part of the cases of loss of the ability to hear the outside world is associated with infectious diseases and injuries, however, many patients lose their hearing or do not have it from birth due to the presence of certain mutations in the TMC1, NOX3 genes and about a hundred other DNA sites.
In recent years, molecular biologists have learned to combat similar forms of deafness by correcting mutations in similar regions of the genome using various forms of gene therapy. For example, a year ago, Harvard researchers protected mice from developing the form of deafness that Ludwig van Beethoven suffered from, and five years ago they managed to create a gene therapy that corrects mutations in the TMC1 gene.
Professor Epstein and his colleagues have discovered another possible "target" for such forms of gene therapy. They made this discovery by studying the work of genes and proteins associated with the development of the inner ear of humans and other mammals.
To reveal the functions of these genes, biologists damaged one of them in the embryos of mice and observed how the shape and work of the cochlea and other components of the inner ear would change as a result.
The attention of scientists was attracted by the GAS2 gene, damage to which did not lead to visible changes in the structure or vital activity of ear cells, but at the same time caused almost complete deafness in mice with a similar mutation. As a rule, rodents stopped hearing all high-frequency sounds as a result of the fact that the sensitivity of their ears to such fluctuations decreased by 99.999%.
In the past, as Professor Epstein and his colleagues note, mutations in the GAS2 gene were not associated with the development of deafness, since it is responsible for the production of protein molecules that play an important role in the process of cell self-destruction. It turned out that he had another, no less important function in the body – he is responsible for maintaining the shape of the cells of the inner ear and ensuring high rigidity of their walls.
Accordingly, the appearance of mutations in it leads to the fact that these cells lose the ability to conduct sound vibrations through themselves and at the same time amplify them, which does not allow the neurons of the inner ear to recognize acoustic waves and turn them into electrical impulses understandable to the brain. Having revealed the important role of the GAS2 gene in hearing, scientists became interested in whether mutations in it occur among deaf people.
To do this, the scientists contacted colleagues working with similar patients and asked them to forward their DNA samples. This allowed Professor Epstein and his colleagues to uncover many cases of hearing loss as a result of the appearance of mutations in GAS2 that affected several people from Somalia. Subsequent analysis of the genomes of deaf and deaf-mute people from other countries, the researchers hope, will help them understand how often this mutation occurs among the population of the whole Earth.
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