The usherin mutation c.2299delG leads to its mislocalization and disrupts interactions with whirlin and VLGR1
Lars Tebbe, Maggie L. Mwoyosvi, Ryan Crane, Mustafa S. Makia, Mashal Kakakhel, Dominic Cosgrove, Muayyad R. Al-Ubaidi, Muna I. Naash
Abstract
Abstract Usher syndrome (USH) is the leading cause of combined deafness-blindness with type 2 A (USH2A) being the most common form. Knockout models of USH proteins, like the Ush2a -/- model that develops a late-onset retinal phenotype, failed to mimic the retinal phenotype observed in patients. Since patient’s mutations result in the expression of a mutant protein and to determine the mechanism of USH2A, we generated and evaluated an usherin (USH2A) knock-in mouse expressing the common human disease-mutation, c.2299delG. This mouse exhibits retinal degeneration and expresses a truncated, glycosylated protein which is mislocalized to the photoreceptor inner segment. The degeneration is associated with a decline in retinal function, structural abnormalities in connecting cilium and outer segment and mislocaliztion of the usherin interactors very long G-protein receptor 1 and whirlin. The onset of symptoms is significantly earlier compared to Ush2a -/- , proving expression of mutated protein is required to recapitulate the patients’ retinal phenotype.