A rare, autosomal recessive syndrome of congenital deafness and progressive blindness. Type IB/1A is caused by mutation in the myosin-7A gene that encodes an unconventional myosin that is expressed in hair cells, type 1C by mutations in harmonin, type 1D by mutations in otocadherin, type 1F by mutations in protocadherin 15, type 1G by mutation in the SANS gene. Other type 1 variants have been mapped but specific genes have not been identified. Usher's syndrome type 2 is similar but the hearing loss is less profound and vestibular function is normal. Type 2A is caused by mutation in the usherin gene, type 2B is linked to chromosome 3p, type 2C involves mutation in the GPR98 gene (a G-protein-coupled receptor), and type 2D by mutation in the whirlin gene. Usher's syndrome type 3, in which there is progressive hearing loss, is caused by mutation in the clarin 1 gene.
Subjects: Medicine and Health — Chemistry.