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目的对1例临床确诊为纯合型家族性高胆固醇血症(FH)先证者及其3代家系成员进行基因检测和系谱分析,探讨该FH患儿发病的分子病理基础。方法收集FH先证者家系3代共29例血标本及临床资料。对先证者进行心电图和超声检查。对其家系成员进行血脂测定,改良苯酚-氯仿法提取患儿及家系成员基因组DNA并鉴定,应用多聚酶链反应-单链构象多态性(PCR-SSCP)分析结合DNA直接测序方法,检测其低密度脂蛋白受体(LDLR)基因全部18个外显子和启动子及载脂蛋白B100(ApoB100)R3500Q位点,核苷酸序列分析结果与GenBank比对寻找突变。结果1.血管超声示先证者右锁骨下动脉起始,双侧颈总动脉分叉处中段内-中膜轻度增厚,右侧颈总动脉中段后壁多发小钙化斑,主动脉瓣轻度关闭不全;2.该家系排除ApoB100基因R3500Q突变;3.核苷酸序列分析证实先证者及其父亲、祖父和叔叔等6人LDLR基因第10外显子发生W462X杂合突变,为色氨酸改变为终止密码子,使终止密码子在第462位提前出现;先证者及母亲和外祖母LDLR基因第13外显子发生A606T杂合突变,为第1879位G→A碱基置换,导致丙氨酸改变为苏氨酸。结论该FH先证者LDLR基因存在W462X/A606T复合杂合突变,分别来源于父系及母系遗传。这种复合杂合突变患者具有与FH纯合子相同的临床特征。
OBJECTIVE: To investigate the molecular and pathological basis of the pathogenesis of FH in a case of homozygous familial hypercholesterolemia (FH) proband and its third generation pedigree. Methods A total of 29 blood samples and clinical data of 3 generations of FH probands were collected. Proximity ECG and ultrasound examination. The blood lipids of their pedigree were determined. The genomic DNA of children and their pedigree was extracted by phenol-chloroform method and identified by PCR-SSCP and DNA direct sequencing. All 18 exons and promoters of the density lipoprotein receptor (LDLR) gene and the R3500Q locus of the apolipoprotein B100 (ApoB100) were obtained. The results of nucleotide sequence analysis were compared with the GenBank to find the mutation. Vascular ultrasound showed prolapse of the right subclavian artery, middle carotid bifurcation of the middle medial - medial membrane mild thickening of the right common carotid artery in the posterior wall of multiple calcified plaque, aortic valve Mild partial closure; 2. The family of ApoB100 gene R3500Q excluded from the mutation; 3. Nucleotide sequence analysis confirmed that the proband and his father, grandfather and uncle 6 LDLR gene exon 10 occurred W462X heterozygous mutation was Tryptophan changed to the stop codon, so that the stop codon appeared in advance at the position 462; proband and mothers and grandmothers LDLR gene exon 13 A606T heterozygous mutation, for the first 1879 G → A base replacement , Resulting in alanine to threonine. Conclusion There are W462X / A606T complex heterozygous mutations in the LDH gene of FH probands, which originated from paternal and maternal inheritance respectively. This compound heterozygous mutant has the same clinical features as FH homozygotes.