Identification of WDR36 as a Novel Gene for Adult–Onset Primary Open Angle Glaucoma (POAG) at the GLC1G Locus on 5q22.1

Abstract

Abstract: : Purpose:Previously, we mapped an Adult–Onset POAG locus (GLC1G) to 5q (ARVO–2003 Abst. #1128). In this study, we aimed to reduce this region and to identify the GLC1G disease–causing gene. Methods: Linkage of new POAG families to the 5q22.1 region was evaluated by DNA genotyping and computer–assisted data analysis. Mutation screening was carried out by direct DNA sequencing of coding exons and their flanking intron–exon boundaries. Results: The new POAG locus was initially mapped between D5S1466 and D5S1480 (∼35–Mb). Follow up studies provided linkage in 7 families (Z_max of 5.41 with D5S2501). Subsequently, 7 genes mapping between D5S1466 and D5S2051 (∼2–Mb) were selected for mutation screening (MAN2A1, AK125070, BC017169, TSLP, WDR36, CAMK4 and STARD4). Sequence analysis revealed only one significant alteration (i.e., D658G) in WD40–Repeat 36 (WDR36). This mutation segregated in all 7 affected members of our first GLC1G–linked family and was absent in 470 normal control chromosomes. Further screening identified 24 DNA variations in 130 unrelated POAG subjects. Overall, 4 evolutionary conserved disease–causing mutations (N355S, A449T, R529Q and D658G) were identified in 17 subjects (5.02%) of whom, 65% had high–pressure and 35% low–pressure glaucoma. By Northern blotting 2 distinct WDR36 mRNA transcripts of 2.5– and 5.9–kb were observed in human heart, placenta, liver, skeletal muscle, kidney and pancreas. In mouse, two transcripts of 3.5– and 2.9–kb showed analogous expression patterns to human. WDR36 gene expression in lens, iris, sclera, ciliary muscles, ciliary body, trabecular meshwork, retina, and optic nerve were established by RT–PCR. In mouse, mRNA expressions were detected in 7–, 11–, 15– and 17–days old developing embryos. Conclusions: WDR36 is a novel causative gene for Adult–Onset POAG at the GLC1G locus. Mutations in this new gene are involved in etiology of both high– and low–pressure POAG. Supported by EY–09947 and M01RR–06192.

Keywords: candidate gene analysis • gene mapping • gene/expression