Hearing loss associated with a lack of cell-cell junctions

Sound waves are filtered through the outer ear to the cochlea, where hair cells convert the sound into the electric impulses that travel through the auditory nerve to the brain. Cochlear hair cells are extremely sensitive to stress and loss of these cells is a common cause of deafness. The formation of tight junctions between cells allows epithelia to form barriers to prevent fluid and other molecules from moving freely throughout the body. In this issue of the Journal of Clinical Investigation, Saima Riazuddin and colleagues at the Cincinnati Children's Hospital, identify a role for the tricellular tight junction protein, TRIC, in cochlear hair cell preservation. A mutation in the TRIC gene had been previously linked to hearing loss in humans; however, the mechanism of hearing loss was unknown. Riazuddin and colleagues introduced the same mutation in mice and found that these mice lost cochlear hair cells. Their data suggests that mutated TRIC creates a toxic environment in the cochlea due to fewer tight cell junctions. In the accompanying commentary, Karen Avraham and colleagues from Tel Aviv University point out that this new mouse model will provide insights into human TRIC-associated deafness and provide insights into how tight junction function can be restored.