Defective Myosin Genes in Mutant Mice and Human Diseases

Myosins are highly divergent actin‐based molecular motors. In five of eight classes expressed in mammals, defects in genes have been identified in mutant mice and/or human diseases. A mutated myosin II‐7 gene is one of the causes of human familial hypertrophic cardiomyopathy (FHC). The defective myosin Va gene is responsible for Griscelli disease, which is characterized by partial albinism and immunodeficiency, while in its mouse homologue coat color dilution is seen with or without neurological defects. There are three classes of myosins, VI, VII and XV, that are essential in the inner ear function. In humans, mutations in the VIIa gene are associated with three deafness‐related diseases, Usher 1B/DFNB2/DFNA11, providing the first example of exhibition of recessive‐ and dominant‐inherited disorders by different mutations in a single myosin gene.