Mutation detection of Pakistani families with autosomal recessive retinal dystrophies

Abstract

PurposeHereditary retinal dystrophies (RD) are a group of heterogeneous disorders caused by mutations in over 200 genes. RDs can be subdivided into different groups based on the primary degeneration of rod or cone photoreceptor cells. This study was conducted to investigate the underlying RD genes and mutation in consanguineous families from Pakistan.MethodsFamilies were recruited after informed consent. Peripheral blood was collected and genomic DNA was extracted according to standard procedures. Homozygosity mapping was performed using Affymetrix Gene Chip Human Mapping 250 K‐NspI arrays. The data were analyzed using Homozygosity Mapper software. Primers for amplifying all exons and intron boundaries of all genes were designed with Primer3plus software followed by PCR and Sanger sequencing. Minigene splicing assay and DNA walking were performed on respective samples.ResultsHomozygosity mapping identified a novel locus in family A, one novel gene (C8ORF37) in family B and a large novel genomic deletion of the (LCA5) gene in family C.ConclusionsOur study indicates the heterogeneous nature of retinal dystrophies in Pakistan. Although earlier studies have explored a number of RD families, but underlying genes are still unknown for significant proportion of Pakistani families. Theoretically the traditional screening methods (homozygosity mapping based candidate gene sequencing) were successful, however SNP based genome wide scan were further implemented to improve the detection of underlying variations responsible for Retinal Dystrophies. Therefore the amalgamation of traditional and modern molecular techniques is required for accurate identification of mutations. It is anticipated that these findings will contribute to future genetic testing in Pakistani families to minimize the risk of recessive disorders.