The circling (cir/cir ) mouse is a murine model for human non‐syndromic deafness DFNB6. The causative gene is transmembrane inner ear (tmie), in which the mutation is a 40‐kilobase genomic deletion including tmie. The function of Tmie is unknown. To better understand the function of Tmie, we observed the spatiotemporal expression of tmie in the mouse cochlea using a Tmie‐specific antibody during postnatal inner ear development. Tmie was expressed in the cochlear hair cells of the mouse inner ear from embryonic days to adult. It is postulated that Tmie protein is involved in the hair cell structural formation and maturation before hearing onset (around P14), and maintenance of organ of Corti tissues after that. The cochlear hair cells of the circling mouse showed a basal‐to‐apical gradient of outer hair cell degeneration. The hair cell stereocilia bundles revealed the abnormal structure and it expanded to the apical region. In order to find the exact localization of Tmie protein inside the cell, we transfected the plasmids expressing GFP‐Tmie fusion protein into the HEI‐OC1 auditory hair cells. Tmie protein was colocalized with Calnexin (Canx), ER marker protein, but not with beta‐COP, Golgi marker protein. We next produced the Myo7a promoterdirected tmie expression transgenic mice to induce the phenotypic rescue of circling mice in a gene therapeutic way. Some circling mice with tmie transgene showed the normal behavior and hearing ability. These results indicate that tmie has a critical role in the inner ear development and hearing ability in the mice.

• Jae-Woong Ryoo(School of life sciences & Biotechnology Kyungpook National University)