Evaluation of Pedigrees With Autosomal Recessive Retinal Dysfunction Using a Whole Genome Scan Approach (WGS)

Abstract

Purpose: : To determine the causative gene, or associated chromosomal loci in 28 families with autosomal recessive retinal disorders presenting to the clinics at Moorfields Eye Hospital.

Methods: : Patients and families were recruited from Moorfields Eye Hospital London, and Moorfields Dubai, and diagnoses included Leber Congenital Amaurosis (LCA), retinitis pigmentosa (RP) and Usher syndrome. DNA samples from individuals in each pedigree were genotyped using either Affymetrix Genechip® Human Mapping 100K set or 500K Array set. Autozygosity mapping and linkage was performed on 20 consanguineous families, and conventional linkage analysis was carried out for the remainder. Software written in Visual Basic was used to query the data for regions of autozygosity and linkage within MS Excel. Mutations were determined by Sanger sequencing of candidate genes.

Results: : Of 28 families analysed, the number of affected individuals in each family ranged from 1 - 5 (mean 2.5). The causative gene was identified in 18 families (15 consanguineous and 3 non-consanguineous families). Interestingly, two probands previously diagnosed with RPE65 disease (homozygous for p.A132T and p.N321K), in whom clinical signs were not typical, were found by WGS to link to distinct genetic loci (RDH12 and RP25). Moreover, WGS excluded RPE65 as a segregating locus in each of these families. For those families in which causative genes were not identified, candidate chromosomal regions were determined, which are likely to illuminate novel genes after further investigation.

Keywords: retina • genetics • gene microarray