A Gene for X–Linked Retinitis Pigmentosa Maps to Xq28 in a Large Ohio Family

Abstract

Abstract: : Purpose: To map the gene for an X–linked form of retinitis pigmentosa. Methods: we examined 22 members of a family in which retinitis pigmentosa appeared to be transmitted in an X–linked fashion. Complete ocular examinations were performed and fundus photographs and electroretinograms were obtained. Mutation analysis of the RPGR and RP2 genes were done using published standard methods. Affected and non–affected family members were genotyped for 18 polymorphic markers (ABI Biosystems Inc., Foster City, CA) on the X–chromosome spaced at 10cM intervals. PCR was performed using the ABI PCR 9700 system. Samples were run on the ABI 3100 genetic analyzer. The results were analyzed with the GeneMapper 1.1 software. Results: Visual acuity in the five affected individuals ranged from 20/40 to 20/75. All five described noticing the onset of night blindness and color vision defects symptoms in the second decade of life, with the earliest at age 13. All affected individuals failed the Ishihara color plate test. All had evidence of constricted peripheral vision by Goldman visual field testing. Indirect ophthalmoscopy revealed peripheral bone spicules, waxy pallor of the optic nerve, and attenuated retinal blood vessels. Haplotype analysis revealed segregation of the disease phenotype with markers at Xq28. A LOD score of 2.17 was obtained with marker DXS1073. Conclusions: We present evidence for a possible sixth XLRP locus at Xq28. The clinical phenotype is not significantly different from other types of X–linked RP.

Keywords: genetics • retinal degenerations: hereditary • linkage analysis