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Congenital Hearing loss Cause is a Mutated Gene
August 7, 2008, The American Journal of Human Genetics (2008), doi:10.1016/j.ajhg.2008.07.008
Congenital Hearing Loss Cause is From a Gene Mutation
In 2001 in Chicago, Illinois, chromosome 12 was identified as the one containing a gene for one family's history of hearing loss. Further research ensued in Iowa, France and Germany and the results were published online on July 31, 2008 in the American Journal of Hearing Genetics. The research was headed up by research scientist Marci Lesperance, MD, now a hearing researcher at the University of Michigan Health System.
The specific anomaly was identified as a mutation in a gene, SLC17A8, that accounts for a form of hearing loss that diminishes one’s ability to hear high-frequency sounds, very similar to presbycusis that is associated with age-related hearing loss. The severity of the mutation’s effects varies among individuals and the effects may occur early or later in life. The researchers have named this form of deafness DFNA25.
The researchers showed that the mutation accounts for hearing loss in one family in the Chicago area: the Phalin family and another unrelated extended family in Iowa. Since the exact mutation occurred in two families that appear completely unrelated, the researchers posited that the mutation must be an ancient one and not particularly rare. Contacting physicians in France and Germany near where the two families emigrated from, they found similar intergenerational hearing loss in a number of families in those countries and areas.
The key to identifying which gene was responsible for the families’ hearing loss occurred in French scientist Jean-Luc Puel’s laboratory. Puel and his research team, also authors of the study, discovered that a mouse lacking the SLC17A8 gene was deaf.
Through extensive studies, the French research team and colleagues in Germany also were able to discover precisely how the SLC17A8 gene and the protein it encodes, VGLUT3, are needed in the inner ear to process the hearing signal. There, VGLUT3 normally promotes the presence of glutamate, a neurotransmitter important in allowing the ear’s inner hair cells to convey signals to the auditory nerve, which carries them to the brain. The mutation in the families most likely interferes with that process.