Retinal Degeneration in the Rd16 Mouse Is Associated With a Deletion in a Novel Centrosomal Protein CEP290/NPHP6 That Interacts With Retinitis Pigmentosa GTPase Regulator (RPGR)

Abstract

Purpose: : Animal models of retinal degeneration permit investigations into mechanisms of disease pathogenesis and design of effective therapies. The goal of this study is to characterize the defect in the rd16 mouse, which exhibits early–onset retinal degeneration.

Methods: : The phenotype was documented using fundus photography, electroretinography, and histology and the genetic characterization was performed using positional candidate gene mapping approach. Protein expression, characterization, and immunolocalization were performed. Co–immunoprecipitation from mouse and bovine retina was performed to identify interacting proteins

Results: : The inheritance pattern of rd16 mutant allele is autosomal recessive and the gene was mapped to mouse chromosome 10 flanked by microsatellite markers D10Mit244 (99.4M) and D10Nds2 (105M), which is syntenic to human chromosome 12q21.1. Sequence analysis of one of the genes in the critical region revealed an in–frame deletion in the putative myosin–tail homology domain of a novel centrosomal protein, CEP290/NPHP6. We demonstrate that in mouse and bovine retina CEP290/NPHP6 associates with retinitis pigmentosa GTPase regulator (RPGR), a ciliary/centrosomal protein probably involved in regulating intracellular transport, as well as with molecular motors and selected microtubule nucleating/anchoring proteins. Despite reduced amounts, we detect significantly higher co–immunoprecipitation of the truncated CEP290/NPHP6 protein with specific RPGR isoform(s) in the rd16 retina. Immunogold labeling studies reveal redistribution of RPGR and rhodopsin in the rd16 retina.

Conclusions: : Mutations in this protein have recently been identified in Joubert syndrome; however, no other gross pathology is observed in the rd16 mouse. We propose that CEP290/NPHP6 modulates microtubule assembly during diverse intracellular transport processes by organizing distinct multi–protein complexes.

Keywords: gene mapping • photoreceptors • retina