Discovery of a deafness-causing gene defect in mice has helped identify a new protein that protects sensory cells in the ear, according to a study led by University of Iowa researchers. The findings, which also involved Kansas State University, appear in the August 21 issue of the open-access journal PLoS Genetics, says a statement released by the University of Iowa.


In humans, hereditary deafness is one of the most common birth defects, yet most genes involved in hearing are unidentified, says the statement. Mice are used as research models because mouse and human auditory genetics are very similar.


Using a deaf mouse model generated at the Jackson Laboratory, the team identified the deafness-causing defect in the claudin-9 gene, according to the statement. The mutated gene fails to produce normal claudin-9 protein, which, the UI team showed, is needed to maintain the proper distribution of potassium in the inner ear, says the statement.


The paper’s senior author Botond Banfi, MD, PhD, assistant professor of anatomy and cell biology in the UI Roy J. and Lucille A. Carver College of Medicine, said in the statement that 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, he added. 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, he said.


When claudin-9 is mutated, potassium floods the wrong part of the sensory cells, killing most and leaving the remaining ones functionally defective, says the statement.


In follow-up efforts, Banfi and colleagues, including the study’s first author Yoko Nakano, PhD, UI assistant research scientist in anatomy and cell biology, are screening people with hearing impairment to see if some of them have a mutation in claudin-9.


The study was funded in part by a grant from the National Institutes of Health and support from the UI Carver College of Medicine and the UI Gene Therapy Center.


Click here to view the PLoS journal article.


[Source: University of Iowa]