复合杂合突变导致遗传性蛋白C缺陷症一家系调查

A pedigree with hereditary protein C deficiency caused by compound heterozygous mutations

目的调查复合杂合突变导致遗传性蛋白C缺陷症家系的临床特征与基因突变情况,并分析其基因型与临床表型的关系。方法采集先证者及其家系成员(3代5人)外周静脉血,检测蛋白C活性、蛋白S活性和抗凝血酶活性等指标以明确表型诊断。采用PCR对先证者PROC基因所有外显子及侧翼序列进行扩增,PCR产物纯化后进行直接测序。运用ClustalX-2.1-win软件分析突变的保守性;使用在线生物信息学软件预测突变的致病性。结果家系中有4人存在遗传性蛋白C缺陷症,先证者临床表现为肺栓塞和下肢深静脉血栓栓塞,其他家系成员无明显的血栓形成事件表现。基因测序发现先证者PROC基因第7号外显子存在c.541T>G杂合错义突变(p.Phe181Val)和c.577-579delAAG杂合缺失突变(p.Lys192deletion),其父亲为c.541T>G突变杂合子,母亲和妹妹为c.577-579delAAG突变杂合子。保守性分析显示Phe181和Lys192在同源物种间均高度保守,生物信息学软件预测该2个突变位点均为有害突变。结论该遗传性蛋白C缺陷症家系存在c.541T>G杂合错义突变和c.577-579delAAG杂合缺失突变,该复合杂合突变可能引起先证者蛋白C活性明显降低,从而导致反复深静脉血栓栓塞和肺栓塞。

Objective To investigate the clinical characteristics and gene mutations in a pedigree with inherited protein C deficiency caused by compound heterozygous mutations and analyze the relationship between genotype and clinical phenotype.Methods The peripheral venous blood samples were collected from the proband and other members of this pedigree,including 3 generations and 5 individuals.The activities of protein C,protein S and antithrombin were detected to confirm the diagnosis for phenotype.The exons and flanking sequences of PROC gene were amplified by PCR.The PCR products were purified and directly sequenced.ClustalX-2.1-Win software was used to analyze the conservatism of mutations.The online bioinformatics software was used to predict the pathogenicity of the mutations.Results Hereditary protein C deficiency was found in four members of this family The clinical manifestations of the proband werepulmonary embolism and venous thromboembolism of lower extremities,while the other members of this family had no obvious thrombosis events.The gene sequencing revealed the presence of c.541T>G(p.Phe181Val)missense mutation and c.577-579delAAG(p.Lys192deletion)deletion mutation in exon 7 of PROC gene of the proband.His father was heterozygote of c.541T>G mutant,and both of his mother and sister were heterozygotes of c.577-579delAAG mutant.Conservative analysis showed that Phe181 and Lys192 sites were highly conserved among homologous species.Bioinformatics software predicted that both of the mutations belong to deleterious mutation.Conclusion A heterozygous missense mutation of c.541T>G and a heterozygous deletion mutation of c.577-579delAAG were identified in a Chinese pedigree with hereditary protein C deficiency.This compound heterozygous mutations may significantly reduce protein C activity in proband,leading to recurrent venous thromboembolism and pulmonary embolism.