Expression analysis of the TMC gene family in the auditory system during zebrafish embryonic development

The transmembrane channel-like (TMC) gene family encodes membrane proteins required for hair cell mechanotransduction. While TMC1 and TMC2 are indispensable for mammalian hearing, the functions of other paralogs remain poorly defined. Using zebrafish, we examined nine TMC genes (tmc1, tmc2a, tmc2b, tmc3, tmc4, tmc5, tmc6a, tmc6b, and tmc8) through phylogenetic, transcriptomic, and spatiotemporal expression analyses. tmc1, tmc2a, and tmc2b were robustly expressed in hair cells of the otic vesicle and neuromasts, supporting their early roles in hair cell differentiation. tmc3 and tmc6a showed clear expression by in situ hybridization but were underrepresented in transcriptomic datasets. tmc4 and tmc5 were more broadly expressed, including vestibular hair cells and neuromasts from 72 to 96 h post-fertilization (hpf). Several TMC genes were also detected in non-sensory tissues, suggesting potential roles in other developmental processes. Together, this study provides the first comprehensive atlas of TMC gene expression during zebrafish embryogenesis and reveals divergent expression patterns among paralogs.