Specialised apical structures in the sensory receptors in the eye and the ear detect light and mechanical stimuli, respectively. Sensory receptors seem to have evolved from a common ancestor, and mutations in some of the genes that are required for both sight and hearing cause Usher syndrome, a human syndrome of visual and acoustic-vestibular defects. Seiler and co-workers now report that protocadherin15 (PCDH15), a gene mutated in Usher syndrome, is duplicated in zebrafish (see ). They show that the zebrafish auditory/vestibular mutant orbiter has a mutation in pcdh15a, an orthologue of PCDH15, and that morpholino-based depletion of a second orthologue, pcdh15b, causes a visual defect. The researchers conclude that during evolution, duplicated pcdh15genes acquired functions that maintain the structural integrity of the specialised apical surfaces of different sensory receptors. Zebrafish, they add, provide a new model for Usher syndrome.
