MYO15A and hearing loss disorder: Genetic studies have identified more than one hundred genes with variants associated with hearing loss including four genes encoding unconventional myosins, MYO3A, MYO6, MYO7A and MYO15A, and two genes encoding conventional myosins, MYH9 and MYH14. The four unconventional myosins and some class-I myosins are expressed in hair cells and are essential for developing and maintaining functional stereocilia.