Scientists Link Genetic Pathway To Development Of Hearing

Located in the spiraled cochlea, the hearing portion of the innerear, the hair cells transform the mechanical vibrations that enter theear in the form of sound waves into chemical signals, which they thendirect to the brain. Ping Chen, PhD, assistant professor of cellbiology at Emory University School of Medicine, and her colleaguesfound that the development of cochlea and hair cells is dependent on agenetic pathway called the PCP (planar cell polarity) pathway.

Although some species, including birds, are capable ofre-growing hair cells, mammals lack the ability to naturally regeneratehair cells. Thus individuals born with improperly developed hair cells,or those who lose them through trauma, disease, environmental factorsor aging, cannot regain their hearing. Reports from the NationalInstitutes of Health (NIH) indicate that severe hearing impairmentaffects 28 million Americans. That number includes the approximately4,000 Americans each year who suffer from sudden deafness, and theroughly 12,000 children born each year with difficulty hearing.

Scientists have been optimistic that by discovering the genesinvolved in development of the ear they could learn the molecular andgenetic basis for some forms of deafness and offer promises for futureefforts in hearing restoration. For the past two decades they haveunderstood that the unique asymmetrical shape of hair cells was anessential part of their proper function. However, it was not clearwhich genes were involved in the development of this polarized shapewithin the cochlea. By using mouse models, Dr. Chen and her researchteam discovered that the PCP pathway is involved in shaping the cochleaand the sensory hair cells. Mutations within this genetic pathwayimpact the shape of the cochlea and the polarity of the sensory haircells that are essential for hearing.

"This basic molecular pathway is involved in regulating manyother aspects of embryonic development in addition to the formation ofthe polarized structure of the auditory sensory organ," says Dr. Chen."Finding out which processes are involved in the formation of thesepolarized cells is an essential, fundamental issue for bothdevelopmental and cell biologists."

Other authors of the study included Jianbo Wang and AnthonyWynshaw-Boris from the University of California San Diego School ofMedicine, Sharayne Mark, Xiaohui Zhang, Dong Qian, Seung-Jong Yoo,Kristen Radde-Gallwitz, Yanping Zhang, Xi Lin from Emory UniversitySchool of Medicine, and Andres Collazo from House Ear Institute.

The research was funded by the NIH and the Woodruff Foundation.