Among the stereocilia-related genes, there are many that are clinically important and frequently associated with hearing loss. Inner hair cells (IHCs) and outer hair cells (OHCs) express a diverse set of deafness-related genes in terms of gene expression. This is indicative of the unique, critical roles played by IHCs and OHCs in sound transduction, with IHCs being necessary for the conversion of mechanical movements into electric signals, whereas the OHCs have a crucial role in cochlear amplification. The stereocilia components are formed by a variety of genes, including actin gamma 1 (encoded by ACTG1), cadherin 23 (encoded by CDH23), calcium- and integrin-binding family member2 (encoded by CIB2), espin (encoded by ESPN), myosin IIIa (MYO3A), unconventional myosin VIIa (MYO7A), unconventional myosin XVa (MYO15A), protocadherin 15 (PCDH15), PDZ domain-containing 7 (PDZD7), radixin (RDX), stereocilin (STRC), transmembrane channel-like protein 1 (TMC1), taperin (TPRN), TRIO and F-actin-binding protein (TRIOBP), harmonin (USH1C), usherin (USH2A), and whirlin (WHRN). Among them, several genes related to stereocilia are also expressed in the retina. This could lead to Usher syndrome (USH), which is characterized by both visual impairment and hearing loss.