COSM14: Genetics Research on Hearing Loss Provides New Insights

LAS VEGAS—Experts on sensorineural hearing loss (SNHL) gathered for a panel presentation entitled “Fluctuating and Progressive Sensorineural Hearing Loss in Children,” which convened during the Annual Meeting of the Triological Society, held here May 15-16 as a part of the Combined Otolaryngology Spring Meetings.

Panel speakers gave reason for hope that new insights into the genetics of the disorder might help guide future treatment and that the field of otolaryngology is getting a better grasp on SNHL caused by cytomegalovirus (CMV).

Panel moderator Marci Lesperance, MD, professor of otolaryngology-head and neck surgery at the University of Michigan Health System in Ann Arbor, said the information presented was timely and on the cutting edge. “There’s some exciting research going on to help us really understand the causes of progressive hearing loss in children,” she said. “And by understanding the cause, we have the potential for having good interventions to offer in the future.”

“This is really a very frustrating clinical problem when you sometimes don’t have very much to offer the parents,” she added.

Genetic Mutations

Andrew J. Griffith, MD, PhD, chief of the molecular biology and genetics section of the otolaryngology branch of the National Institute on Deafness and Other Communication Disorders in Bethesda, Md., part of the National Institutes of Health, discussed how his laboratory has developed a mouse model with SLC26A4 gene mutations that mimic the human phenotype of hearing loss fluctuation. The mutations can cause hearing loss related to enlarged vestibular aqueducts.

SLC26A4 knockout mice are totally deaf and are not a good model for studying the typical human phenotype. But Dr. Griffith’s lab has developed a model in which the expression of SLC26A4 is controlled by putting the antibiotic doxycycline in the mice’s drinking water during the formation of the embryo (Neurobiol Dis. 2014;66:53-65).

Hearing tests show that the hearing thresholds of those mice fluctuate before getting progressively worse, similar to people with enlarged vestibular aqueducts. “We think this is a useful tool now to explore the cellular and molecular basis of hearing fluctuation,” he said.

Dr. Griffith and his colleagues have a few thoughts on what is happening in this situation. “We expect the blood-labyrinth barrier, which is the ear’s equivalent of the blood-brain barrier, is involved with this process and that could explain the drops in hearing we see with trauma,” he said. Another suspicion is that activation of the innate immune system plays a role, he said, as well as oxidative stress.