Table_4_Mutational Spectrum of LDLR and PCSK9 Genes Identified in Iranian Patients With Premature Coronary Artery Disease and Familial Hypercholesterolemia.DOCX

Familial hypercholesterolemia (FH) is a common, yet underdiagnosed, genetic disorder characterized by lifelong elevated low-density lipoprotein cholesterol levels, which can increase the risk of early-onset coronary artery disease (CAD). In the present study, we screened the nucleotide variations of the LDLR and PCSK9 genes, as well as a part of the APOB gene, in Iranian patients with FH and premature CAD to find the genetic cause of the disorder. Fifteen unrelated individuals with a clinical diagnosis of FH and premature CAD were recruited. Direct DNA sequencing was applied to screen the whole coding exons and exon–intron boundaries of the LDLR and PCSK9 genes and the main parts of their introns, together with exon 26 of the APOB gene. The pathogenicity of the identified mutations was investigated via either segregation analyses in the family or in silico predictive software. Six different point mutations (p.Cys148Tyr, p.Cys216Tyr, p.Cys302Trp, p.Cys338Trp, p.Leu479Gln, and p.G593Afs∗72) in LDLR and a double mutation (p.Asp172His and p.Ala53Val) in both LDLR and PCSK9 genes were identified in seven families with clinically diagnosed FH (43%), whereas no pathogenic mutations were found in eight families with clinically diagnosed FH. This study is the first to identify 1 pathogenic mutation in the LDLR gene (c.1014C > G [p.Cys338Trp]) and to cosegregate it from the affected individual in the family. No mutations were found in the APOB gene, whereas several silent mutations/polymorphisms were identified in the LDLR and PCSK9 genes. Genetic testing and reports on nucleotide alterations in the Iranian population are still limited. Our findings not only further confirm the significant role of FH in the incidence of premature CAD but also enlarge the spectrum of LDLR and PCSK9 variations and exhibit the heterogeneity of FH in Iranians. In patients with no mutation in the examined genes, the disease could be begotten either by a polygenic cause or by gene defects occurring in other related genes and regions not targeted in this study.

家族性高胆固醇血症（FH）是一种常见却未被充分诊断的遗传性疾病，以终身伴随的低密度脂蛋白胆固醇水平升高为特征，可增加早发性冠状动脉粥样硬化性心脏病（CAD）的发病风险。本研究针对伊朗家族性高胆固醇血症及早发性冠状动脉粥样硬化性心脏病患者，对低密度脂蛋白受体基因（LDLR）、前蛋白转化酶枯草溶菌素9（PCSK9）基因以及部分载脂蛋白B（APOB）基因的核苷酸变异进行筛查，以明确该疾病的遗传病因。本研究共纳入15名经临床确诊为家族性高胆固醇血症且合并早发性冠状动脉粥样硬化性心脏病的无亲缘关系个体。本研究采用直接DNA测序技术，对LDLR和PCSK9基因的全部编码外显子、外显子-内含子交界区域及内含子主要区段，以及APOB基因的第26号外显子进行变异筛查。通过家系共分离分析或计算机模拟（in silico）预测软件，对所鉴定突变的致病性进行评估。在7个经临床确诊的家族性高胆固醇血症家系（占比43%）中，共鉴定出LDLR基因上的6种不同点突变（p.Cys148Tyr、p.Cys216Tyr、p.Cys302Trp、p.Cys338Trp、p.Leu479Gln及p.G593Afs∗72），以及同时存在于LDLR和PCSK9基因的双重突变（p.Asp172His与p.Ala53Val）；而剩余8个临床确诊的家族性高胆固醇血症家系未检出致病性突变。本研究首次在LDLR基因中鉴定出c.1014C>G（p.Cys338Trp）这一致病性突变，并验证了其在受累家系中的共分离特性。APOB基因未检出任何突变，但在LDLR和PCSK9基因中发现了若干沉默突变/多态性位点。伊朗人群的遗传检测及核苷酸变异相关研究报告仍较为匮乏。本研究结果不仅进一步证实了家族性高胆固醇血症在早发性冠状动脉粥样硬化性心脏病发病中的重要作用，同时拓展了LDLR与PCSK9基因的变异谱，并揭示了伊朗人群家族性高胆固醇血症的遗传异质性。对于本次检测基因未检出突变的患者，其疾病可能由多基因因素导致，或是由本研究未覆盖的其他相关基因及区域的基因缺陷所引发。