A protein that protects sensory cells in the ear has been discovered by scientists.
University of Iowa researchers, who carried out this work with collaborators from Kansas State University, attribute the new finding to the discovery of a deafness-causing gene defect in mice.
In humans, hereditary deafness is one of the most common birth defects, yet most genes involved in hearing are unidentified.
Mice are used as research models because their auditory genetics are very similar to humans'.
The researchers behind the present study have revealed that they used a deaf mouse model, generated at The Jackson Laboratory, to identify the deafness-causing defect in the claudin-9 gene.
They showed that the mutated gene fails to produce normal claudin-9 protein, which is needed to maintain the proper distribution of potassium in the inner ear.
"Genes in the claudin family number at least 24 and produce proteins that prevent ions, including potassium, from moving between cells. Sensory cells in the hearing organ are bathed in a high potassium solution on one side and in a low potassium solution on the other side. We found that claudin-9 is very important in keeping the amount of potassium on the two sides separate. This separation protects sensory cells from potassium intoxication," said the paper's senior author Dr. Botond Banfi, assistant professor of anatomy and cell biology in the University of Iowa Carver College of Medicine.
The researchers have found that when claudin-9 is mutated, potassium floods the wrong part of the sensory cells, killing most and leaving the remaining ones functionally defective.
In follow-up efforts, the researchers are screening people with hearing impairment to see whether some of them have a mutation in claudin-9.
Their latest study has been published in the open-access journal PLoS Genetics.