Molecular Genetics of Usher Syndrome

Abstract

Usher syndrome affects hearing, vision and balance. The syndrome is genetically heterogeneous and nine causative genes have been identified so far. Proteins encoded by these genes function in a protein network at different subcellular locations in photoreceptor cells of the retina and hair cells of the inner ear. In hair cells, Usher proteins mainly contribute to the formation of fibrous links that connect stereocilia and also the stereocilia and the kinocilium. In addition, Usher proteins are found in the synaptic region where hair cells contact nerve fibres. In photoreceptor cells the Usher proteins are mainly seen in the region of the connecting cilium including the periciliary region of the cell body, the connecting cilium itself and the basal body and accessory centriole. In addition, Usher proteins are present in the synaptic region of photoreceptor cells. The Usher proteins are thought to have diverse functions including structural support, transport and signalling. Key Concepts Genetic Heterogeneity of Disorders Genes involved in genetically heterogeneous disorders encode proteins that are functionally related. In the case of Usher syndrome, the genes involved encode proteins that function in a protein complex. Defects in different members of the complex lead to the same phenotype. See also Oti and Brunner (2007).