Usherin is required for maintenance of retinal photoreceptors and normal development of cochlear hair cells

• Published in: Proceedings of the National Academy of Sciences - PNAS 2007-03, Vol.104 (11), p.4413-4418
• Main Authors: Liu, Xiaoqing, Bulgakov, Oleg V, Darrow, Keith N, Pawlyk, Basil, Adamian, Michael, Liberman, M. Charles, Li, Tiansen
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Biological Sciences; Cell membranes; Cells; Cilia; Cochlea - growth & development; Extracellular Matrix Proteins - physiology; Eye diseases; Gene Expression Regulation, Developmental; Genetic disorders; Hair cells; Hair Cells, Auditory - growth & development; Hearing loss; Humans; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Microscopy, Confocal; Molecular Sequence Data; Photoreceptors; Proteins; Retina; Retina - growth & development; Retinitis Pigmentosa - metabolism; Retinitis Pigmentosa - pathology; Usher syndromes
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0610950104

Usher syndrome type IIA (USH2A), characterized by progressive photoreceptor degeneration and congenital moderate hearing loss, is the most common subtype of Usher syndrome. In this article, we show that the USH2A protein, also known as usherin, is an exceptionally large ([almost equal to]600-kDa) matrix protein expressed specifically in retinal photoreceptors and developing cochlear hair cells. In mammalian photoreceptors, usherin is localized to a spatially restricted membrane microdomain at the apical inner segment recess that wraps around the connecting cilia, corresponding to the periciliary ridge complex described for amphibian photoreceptors. In sensory hair cells of the cochlea, it is associated transiently with the hair bundles during postnatal development. Targeted disruption of the Ush2a gene in mice leads to progressive photoreceptor degeneration and a moderate but nonprogressive hearing impairment, mimicking the visual and hearing deficits in USH2A patients. These data suggest that usherin is required for the long-term maintenance of retinal photoreceptors and for the development of cochlear hair cells. We propose a model in which usherin in photoreceptors is tethered via its C terminus to the plasma membrane and its large extracellular domain projecting into the periciliary matrix, where they may interact with the connecting cilium to fulfill important structural or signaling roles.