Abstract
Purpose: :
Mutations in CIP98 (DFNB31) cause Usher syndrome type 2D. USH2D patients exhibit congenital hearing loss and progressive retinitis pigmentosa. In this study, we used zebrafish as a model to analyze the role of cip98 in vision and hearing.
Methods: :
In situ
Results: :
Zebrafish have two orthologues of CIP98: cip98a and cip98b. Both are expressed in photoreceptor cells and in subsets of cells in the inner retina. In the retina, the Cip98 proteins partially colocalize at the photoreceptor connecting cilium and synapse, and show a dynamic expression pattern in Müller glia during the first month of life. They also show distinctive localization patterns in the ear and neuromasts of the lateral line. Knockdown of cip98a by morpholino results in a reduced optokinetic response in young fish. In photoreceptors, the connecting cilium is disrupted, and opsin trafficking is impaired. Larvae injected with cip98a morpholino also exhibit a swimming defect suggesting mechanosensory hair cell dysfunction.
Conclusions: :
Zebrafish cip98 genes exhibit a complementary and dynamic expression pattern in the retina and in hair cells. Cip98a is required for normal ciliary development and function in zebrafish photoreceptors, and has a role in mechanosensory hair cell function.
Keywords: retinal degenerations: cell biology • retinal degenerations: hereditary • photoreceptors