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家族性高胆固醇血症(familial hypercholesterolemia,FH)是一种常染色体显性单基因遗传性疾病。世界范围内FH杂合患者的发病率为1/500,纯合子患者症状严重,发病率为1/1 000 000。我们最近诊断一位32岁女性FH伴早发冠状动脉粥样硬化性心脏病患者,血清总胆固醇含量12.99 mmol/L,其父母血脂水平正常。随后,我们应用高通量测序对患者及其母亲进行外显子组分析,测序数据首先与GRCh37数据库进行比对,将比对后检测到的同义突变、位于非编码区的突变以及数据库中已有的SNP筛除。根据其可能的遗传方式,按照常染色体隐性模式进一步筛选,发现148个插入/缺失突变,26个单碱基突变(包括1个无义突变和25个错义突变);对基因突变位点功能筛查和验证分析后,最终发现了一个新的隐性纯合基因突变。该突变为LDLR基因第15个外显子的无义突变位点,该外显子编码O-糖链接结构域。研究中分别构建LDLR基因野生型及突变型表达质粒,Western blot结果显示,突变后的LDLR蛋白仍然可以正常表达,推测发生在O-糖链接结构域的突变可能影响LDLR蛋白在细胞膜上的正确定位,从而无法正常清除血浆中的LDL,最终导致FH的发生。本次研究发现了一个新的位于LDLR基因中的隐性纯合突变,进一步丰富了LDLR基因的突变研究数据,也为FH的基因诊断提供更多的依据。
Familial hypercholesterolemia (FH) is an autosomal dominant single-gene inherited disease. The worldwide incidence of FH heterozygous patients is 1/500, with severe homozygous patients with a prevalence of 1/1 000 000. We recently diagnosed a 32-year-old FH with early-onset coronary atherosclerotic heart disease with a serum total cholesterol level of 12.99 mmol / L and normal parental lipid levels. Subsequently, we performed exome analysis of patients and their mothers using high-throughput sequencing. Sequencing data were first aligned with the GRCh37 database. Synonymous mutations detected after alignment, mutations in non-coding regions, and databases Existing SNP screening. According to its possible inheritance, further screening according to the autosomal recessive pattern revealed 148 insertional / deletion mutations, 26 single-base mutations (including 1 nonsense mutation and 25 missense mutations); mutation sites After functional screening and validation analysis, a new recessive homozygous mutation was finally found. This mutation is a nonsense mutation site of exon 15 of the LDLR gene, which encodes an O-glycosylation domain. The wild type and mutant expression plasmids of LDLR gene were constructed respectively in the study. The results of Western blot showed that the mutated LDLR protein can still be expressed normally. It is speculated that the mutation in the O-glycosylation domain may affect the correct localization of LDLR protein on the cell membrane , Which can not properly clear the plasma LDL, eventually leading to the occurrence of FH. This study found a new recessive homozygous mutation located in the LDLR gene, further enriched the data of mutation research of LDLR gene, and provided more basis for gene diagnosis of FH.