USH2A and retinal degeneration: Furthermore, the absence of the truncated protein at the ciliary ridge in our c.2290delG model mimics observations made in the Ush2a−/− model (i.e., it also has no usherin at the ciliary ridge), but the presence of the c.2290delG mutant usherin in the cytosol is likely what accelerates the onset of retinal degeneration in our model, and suggests that the truncated protein may play a critical role in the time-course and mechanism of disease in patients.