Expression of prestin in OHCs is reduced in Spag6 gene knockout mice.

Sperm-associated antigen 6 (Spag6) gene, which encodes an axonemal protein (SPAG6), ubiquitously expresses in tissue and organs containing ciliated cells. The present work was to investigate whether SPAG6 expressed in cochlear hair cells and, if so, to explore the presumable correlations between prestin and SPAG6. The distribution of SPAG6 in organ of Corti and the morphological features of hair cells in basilar membrane were investigated by immunofluorescent staining. The amount of prestin in Spag6 mutant mice was measured by Western blotting and real-time PCR, respectively. Additionally, co-immunoprecipitation tests were performed to confirm the presumed interaction between prestin and SPAG6. We observed that SPAG6 expressed in the cuticular plate in outer hair cells (OHCs) and prestin in the lateral wall of OHCs that located along with SPAG6 at this site. In comparison to Spag6 +/+ mice, Spag6 -/- mice showed apparent morphological abnormity of OHCs and lower intensity of prestin fluorescence. The expression of prestin in Spag6 -/- mice reduced significantly at both protein and mRNA levels. Moreover, co-immunoprecipitation tests demonstrated the interaction between prestin and SPAG6. Taken together, these data indicate that SPAG6 is indispensible for the stability of OHCs by maintaining the normal expression of prestin, which implies that Spag6 gene is essential for mechanosensory function of OHCs.