Delineating Novel and Known Pathogenic Variants in TYR, OCA2 and HPS-1 Genes in Eight Oculocutaneous Albinism (OCA) Pakistani Families

Abstract

Oculocutaneous albinism (OCA) is associated with a wide range of clinical presentations and has been categorized with syndromic and non-syndromic features. The most common causative genes in non-syndromic OCA are TYR and OCA2 and HSP1 is in the syndromic albinism. The objective of this study was to identify pathogenic variants in congenital OCA families from Pakistan. Eight consanguineous families were recruited, and clinical and ophthalmological examination was carried out to diagnose the disease. Whole blood was collected from the participating individuals, and genomic DNA was extracted for sequencing analysis. TruSight one-panel sequencing was carried out on one affected individual of each family, and termination Sanger sequencing was carried out to establish the co-segregation of the causative gene or genes. In silico analysis was conducted to predict the causative pathogenic variants. Two families were found to have novel genetic pathogenic variants, and six families harbored previously reported variants. One novel compound heterozygous pathogenic variant in the TYR gene, c.1002delA; p.Ala335LeufsTer20, a novel frameshift deletion pathogenic variant and c.832C>T; and p.Arg278Ter (a known pathogenic variant) were found in one family, whereas HPS1; c.437G>A; and p.Trp146Ter were detected in another family. The identification of new and previous pathogenic variants in TYR, OCA2, and HPS1 genes are causative of congenital OCA, and these findings are expanding the heterogeneity of OCA.