Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.
Institute of Molecular Biology &Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
Sci Rep. 2017 Mar 7;7:44185. doi: 10.1038/srep44185.
Nonsyndromic oculocutaneous Albinism (nsOCA) is clinically characterized by the loss of pigmentation in the skin, hair, and iris. OCA is amongst the most common causes of vision impairment in children. To date, pathogenic variants in six genes have been identified in individuals with nsOCA. Here, we determined the identities, frequencies, and clinical consequences of OCA alleles in 94 previously unreported Pakistani families. Combination of Sanger and Exome sequencing revealed 38 alleles, including 22 novel variants, segregating with nsOCA phenotype in 80 families. Variants of TYR and OCA2 genes were the most common cause of nsOCA, occurring in 43 and 30 families, respectively. Twenty-two novel variants include nine missense, four splice site, two non-sense, one insertion and six gross deletions. In vitro studies revealed retention of OCA proteins harboring novel missense alleles in the endoplasmic reticulum (ER) of transfected cells. Exon-trapping assays with constructs containing splice site alleles revealed errors in splicing. As eight alleles account for approximately 56% (95% CI: 46.52-65.24%) of nsOCA cases, primarily enrolled from Punjab province of Pakistan, hierarchical strategies for variant detection would be feasible and cost-efficient genetic tests for OCA in families with similar origin. Thus, we developed Tetra-primer ARMS assays for rapid, reliable, reproducible and economical screening of most of these common alleles.
非综合征性眼皮肤白化病(nsOCA)的临床特征是皮肤、头发和虹膜的色素丧失。OCA 是儿童视力损害最常见的原因之一。迄今为止,已经在患有 nsOCA 的个体中鉴定出六个基因的致病变异。在这里,我们确定了 94 个先前未报道的巴基斯坦家族中 OCA 等位基因的身份、频率和临床后果。Sanger 和外显子组测序的组合揭示了 38 个等位基因,包括 22 个新变体,在 80 个家族中与 nsOCA 表型分离。TYR 和 OCA2 基因的变异是 nsOCA 最常见的原因,分别发生在 43 个和 30 个家族中。22 个新变体包括 9 个错义、4 个剪接位点、2 个无义、1 个插入和 6 个大片段缺失。体外研究表明,携带新错义等位基因的 OCA 蛋白在转染细胞的内质网(ER)中保留。包含剪接位点等位基因的外显子捕获测定显示剪接错误。由于八个等位基因占 nsOCA 病例的约 56%(95%CI:46.52-65.24%),主要来自巴基斯坦旁遮普省,因此对于具有相似起源的家族,变体检测的分层策略将是可行且具有成本效益的 OCA 遗传检测。因此,我们开发了 Tetra-primer ARMS 测定法,用于快速、可靠、可重复和经济地筛选大多数常见等位基因。