The identification of genes that affect the structure and function of the inner ear and thus the ability to hear has enjoyed a ‘golden age’; many have been discovered in the last four years. While in the process tracking down another, Edward Wilcox and colleagues (of the National Institute on Deafness, National Institutes of Health) have stumbled across a genetic variant that is best described as an ‘anti-deafness’ gene (Nature Genetics, Vol. 26, Issue 4, 01 Dec 2000).
They began their study in a large Pakistani family in which several members have severe hearing loss. To localize the relevant gene, they carried out a genome scan, which involves looking for a correlation between genetic markers and the incidence of disease. They homed in on a specific set of DNA markers on chromosome 4—but then discovered that family members carrying two sets of these markers (one on each copy chromosome 4) could hear perfectly well. So they reckoned that either they’d made a mistake, or that another gene variant, elsewhere in the genome, overrides the effect of the deafness-causing gene on chromosome 4, thereby allowing what would otherwise be ‘deaf’ individuals to retain their ability to hear. Although an unlikely hypothesis, the authors investigated it nonetheless. They carried out yet another genome scan on the hearing individuals but this time, looked for a correlation between hearing and markers across the genome. Surprisingly, they found that markers in a region on chromosome 1 correlate with hearing in these individuals. It seems that a genetic variant in this region ‘counteracts’ the chromosome-4 defect. Although the identities of the relevant gene or genes in the chromosome-4 and -1 regions have yet to be determined, the existence of such an extreme modifier of a monogenic disorder in humans—one that ‘ensures’ hearing in an otherwise deaf individual—is a unique discovery.
Dr. Edward R. Wilcox
Laboratory of Molecular Genetics
Telephone: +1 301 402 4162
Fax: +1 301 480 8019
(C) Nature Genetics press release.
Message posted by: Trevor M. D'Souza
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