一个遗传性纤溶酶原缺陷症家系的表型与基因突变分析

目的：对一个遗传性纤溶酶原（PLG）缺陷症家系进行表型和基因变异分析，探讨其发病的分子机制。方法：检测先证者及其家系成员（共3代4人）的凝血酶原时间（PT）、活化部分凝血活酶时间（APTT）、凝血酶时间（TT）、纤维蛋白原（FIB）、D-二聚体（D-D）、纤维蛋白（原）降解产物（FDP）、纤溶酶原活性（PLG:A）、纤溶酶原抗原（PLG:Ag）、抗凝血酶活性（AT:A）、蛋白C活性（PC:A）及蛋白S活性（PS:A）等指标以明确诊断。用DNA直接测序法分析先证者PLG基因的所有外显子及侧翼序列、5’和3’非翻译区及家系成员相应的突变位点区域，用反向测序予以证实。应用ClustalX-2.1-win软件将突变氨基酸进行同源物种序列保守性分析；利用PolyPhen-2、PROVEAN、SIFT和MutationTaster 4个在线生物信息学软件分析突变氨基酸对蛋白质功能的影响；用Swiss-PdbViewer软件对突变位点进行蛋白质模型和氨基酸相互作用分析。结果：先证者和其祖父、父亲PLG:A均降低为正常值的50%左右，PLG:Ag含量正常，结果分别为45%、95%，64%、94%和64%、104%；基因分析发现先证者PLG基因第15号外显子存在c.1858G＞A杂合错义突变导致p.Ala601Thr；其祖父和父亲具有同样的基因突变。Ala601在其11个同源物种间高度保守；4个在线生物信息学软件预测结果一致，均为有害突变，可引起相应疾病。结论：该先证者的PLG基因第15号外显子存在c.1858G＞A（p.Ala601Thr）杂合错义突变；祖孙三代均为Ala601Thr杂合子，突变符合孟德尔遗传规律，且与该家系PLG活性降低有关。

The phenotypic and gene mutation analysis of a family with hereditary plasminogen deficiency

Objective: To detect the phenotype and gene mutation of a family with hereditary plasminogen (PLG) deficiency and to investigate the molecular mechanism of its pathogenesis. Methods: Prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (FIB), D-dimer (DD), fibrinogen degradation product (FDP), plasminogen activity (PLG:A), plasminogen antigen (PLG:Ag), antithrombin activity (AT:A), protein C activity (PC:A) and protein S activity (PS:A) were tested in the diagnosis of the proband and his family members (3 generations and 4 persons). Direct DNA sequencing was used to analyze all exons and exon-intron boundaries of the PLG gene, as well as the 5’ and 3’ non-translation regions and the corresponding mutation site regions of family members, confirmed by reverse sequencing. ClustalX-2.1-win software was used to analyze the conserved amino acid sequence of homologous species. PolyPhen-2, PROVEAN, SIFT and Mutation Taster were used to forecast the possible impact of mutant amino acids on protein function. Finally, the protein model and amino acid interaction analysis was performed on the mutation sites using Swiss-Pdb Viewer software. Results: The PLG:A of the proband and his grandfather and father were reduced to the half, while the PLG:Ag was normal, the results being 45%, 95%; 64%, 94% and 64%, 104% respectively. Gene sequencing revealed that the PLG gene of the proband had c.1858G>A heterozygous missense in exon 15, resulting in p.Ala601Thr. Its grandfather and father had the same genetic mutation. Ala601 was highly conserved among its 11 homologous species. The four online bioinformatics software have consistent predictions, all of whichwere harmful mutations that affect the PLG function, leading to the corresponding diseases. Conclusion: The proband’s PLG gene exon 15 has heterozygous missense mutation of c.1858G>A(p.Ala601Thr) . And the three generations of the grandparents are Ala601Thr heterozygotes, with the mutation in accordance with Mendelian inheritance law and with the family plasminogen activity reduced.