新突变致复合杂合子家族性高胆固醇血症家系的基因检测

A compound heterozygote family of familial hypercholesterolemia due to new mutations

目的对临床诊断为遗传性高胆固醇血症纯合子患者所在家系成员的相关基因进行突变检测和分析,探讨该病的分子诊断方法和发病的可能分子机制。方法以该家系中3代共6人的基因组 DNA 为模板,用 PCR 对低密度脂蛋白受体(LDLR)基因的全部18个外显子和启动子以及载脂蛋白 B-100(Apo B-100)基因3500-3531区域进行扩增,琼脂糖凝胶电泳鉴定后对 PCR 产物直接测序。测序结果与 GeneBank 中该基因的正常序列对比找出突变,结合该家系成员临床表型证实突变。结果在 ApoB-100的3500-3531区域未发现突变,而在先证者 LDLR 基因的第4外显子发现新的点突变685delA 杂合性腺嘌呤缺失和386A>G 杂合错义突变,其父存在685delA 杂合性腺嘌呤缺失,其母存在386A>G 杂合错义突变。结论证实家系先证者是存在 LDLR 突变的复合杂合子,发现的新的 LDLR 基因突变位点386A>G 和685delA 分别来源于父系和母系的遗传,可能是该家系发病的分子基础。

Objective To investigate the molecular diagnosis method and possible molecular mechanism of the etiology of a hereditary genetic hypercholesterolemia family by scanning and analyzing the related genes of hereditary hypercholesterolemia in a clinically diagnosed proband and his family members. Methods Molecular diagnosis was performed with PCR and then DNA sequencing of the promoter and 18 exons of low-density lipoprotein receptor （LDLR） gene and 3500-3531 fragment of apolipoprotein B-100 gene was carried out. The sequencing results were compared with the normal nucleotide sequence queried from the GeneBank database to discover the mutations. Results Familial defective apolipoprotein B-100 was excluded, as no mutation was detected in the apolipoprotein B 3500-3531 fragment. Two new point mutations were detected in the exon 4 of the proband＇s LDLR gene, they were heterozygous 685delA （ Del A at 685） and 386A 〉 G. The sequencing in his parents and other family members showed that the two mutations were paternal origin （685delA） and maternal origin （386A 〉 G ） respectively and should be located in different alleles of the proband. Conclusion Molecular diagnosis in the family shows that the proband is a compound heterozygote and the newly detected LDLR gene mutations of 685delA and 386A 〉 G are the possible molecular etiological basis of the disease in this family.