Nephrocystin-5, a ciliary IQ domain protein, is mutated in Senior-Loken syndrome and interacts with RPGR and calmodulin

Abstract

Nephronophthisis (NPHP) is the most frequent genetic cause of chronic renal failure in children. Identification of four genes mutated in NPHP subtypes 1-4 (refs. 4-9) has linked the pathogenesis of NPHP to ciliary functions. Ten percent of affected individuals have retinitis pigmentosa, constituting the renal-retinal Senior-Loken syndrome (SLSN). Here we identify, by positional cloning, mutations in an evolutionarily conserved gene, IQCB1 (also called NPHP5), as the most frequent cause of SLSN. IQCB1 encodes an IQ-domain protein, nephrocystin-5. All individuals with IQCB1 mutations have retinitis pigmentosa. Hence, we examined the interaction of nephrocystin-5 with RPGR (retinitis pigmentosa GTPase regulator), which is expressed in photoreceptor cilia and associated with 10-20% of retinitis pigmentosa. We show that nephrocystin-5, RPGR and calmodulin can be coimmunoprecipitated from retinal extracts, and that these proteins localize to connecting cilia of photoreceptors and to primary cilia of renal epithelial cells. Our studies emphasize the central role of ciliary dysfunction in the pathogenesis of SLSN.

Distinguishing the four genetic causes of jouberts syndrome–related disorders

“…The full-blown JBTS5 phenotype overlaps with Senior-Loken syndrome (SLS), characterized by retinitis pigmentosa plus juvenile nephronophthisis and occasionally associated with neurological involvement and the MTS 4,5 . Mutations in most nephronophthisis-related genes, encoding ciliary proteins, have been shown to cause SLS, but neurological and neuroradiological features typical of JS were never reported in these patients [19][20][21][22] .We tested the temporal and regional expression of Cep290 using both RT-PCR and in situ hybridization in mouse brain. A full-length murine Cep290 was assembled from three partially-overlapping cDNA contigs from the human genome browser.…”

Massively parallel sequencing for early molecular diagnosis in Leber congenital amaurosis

“…The first part of this study was mainly aimed at validation of the enrichment protocol (proof of concept, patients 1-10), whereas the second part of this study consisted of a blind screening of 12 prescreened mutation-negative patients with LCA (patients [11][12][13][14][15][16][17][18][19][20][21][22]. enrichment of LcA disease genes qPCR was used to target all exons from 16 LCA disease genes.…”

“…For the second lane, libraries were prepared from a 200-300-bp size-selected fraction, and library quantification was performed using qPCR following manufacturer's protocols (lane 2, patients [11][12][13][14][15][16][17][18][19][20][21][22]. In total, 120 µl of a pool of the 12 normalized libraries (concentration of 10 pmolar) was subjected to paired-end sequencing of 2 × 45 cycles.…”

“…This study included 17 patients in which previous Sanger sequencing of six genes and/or LCA chip analysis did not identify causal mutations (lane 1: patients 1-3, 7, and 8; lane 2: patients [11][12][13][14][15][16][17][18][19][20][21][22]. Given the exclusion of 3 of 107 known variants by the in 12.7% of the Yoruba population (1000Genomes Project, pilot_1_YRI_low_coverage_panel) points to a polymorphism rather than a mutation (rs61748445).…”

“…9 Moreover, some of these genes are also involved in syndromic diseases. 10,11 Consequently, an early molecular diagnosis offers the prospect of specific and adequate medical follow-up.…”