一个遗传性凝血因子Ⅴ缺陷症家系表型与基因突变分析

Hereditary factor V deficiency from heterozygous mutations with a novel variant p.Pro798Leufs*13 in the F5 gene

目的 对一个由F5基因复合杂合突变导致的遗传性凝血因子Ⅴ(FⅤ)缺陷症家系进行表型和基因型分析,探讨其分子致病机制。方法 检测先证者及其家系成员(共3代7名成员)凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)、纤维蛋白原(FⅠB)、凝血酶时间(TT)、血浆FⅤ活性(FⅤ:C)、FⅤ抗原(FⅤ:Ag)及其他相关凝血指标以明确诊断。通过自动校正凝血酶曲线法检测凝血酶生成量;用DNA直接测序法分析先证者F5基因的全部外显子、侧翼、5’和3’非翻译区及家系成员相应的突变位点区域;并用相应的生物信息学软件分析突变对蛋白功能的影响。结果先证者PT和APTT较正常对照明显延长,分别为17.9s/13.2s和46.9s/36s;FⅤ:C和FⅤ:Ag显著下降,分别为24%和28%;其父亲(Ⅰ1)、母亲(Ⅰ2)、妹妹(Ⅱ3)和儿子(Ⅲ1)FⅤ:C和FⅤ:Ag水平均有不同程度下降。基因分析显示,先证者第13号外显子存在c.2390_2390delC杂合缺失突变(p.Pro798Leufs*13)以及第25号外显子存在c.6665A>G杂合错义突变(p.Asp2222Gly);其父亲和妹妹为c.2390_2390delC杂合子,母亲和儿子为c.6665A>G杂合子。先证者凝血酶生成延迟和达峰时间比值明显增高;在线生物信息学软件提示这些突变会引起相应的疾病。结论p.Pro798Leufs*13杂合缺失突变和p.Asp2222Gly杂合错义突变可能与该家系血浆FⅤ水平降低有关。

Objective Phenotypic and genotypic analysis of a family with inherited coagulation factor V(FV)deficiency caused by complex heterozygous mutation of F5 gene was conducted to explore the molecular pathogenic mechanism Methods Prothrombin time(PT),activated partial thromboplastin time(APTT),fibrinogen(FIB),thrombin time(TT),FⅤprocoagulant activity(FⅤ:C),FⅤantigen(FⅤ:Ag)and other related coagulation parameters were detected for the proband and his family members(7 members in 3 generations).The thrombin production was measured by automatic correction of thrombin curve.All exons,flanks,5'and 3'untranslated regions of F5 gene of progenitor and corresponding mutation sites of family members were analyzed by direct DNA sequencing.The effect of mutation on protein function was analyzed with the corresponding bioinformatics software.Results The PT and APTT of the proband were significantly longer than those of the normal controls,which were 17.9 s to 13.2 s and 46.9 s to 36 s,respectively.FⅤ:C and FⅤ:Ag were extremely decreased,at 24%and 28%,respectively,The levels of father(I1),mother(I2),sister(II3)and son(III1)FⅤ:C and FⅤ:Ag all decreased to varying degrees.Gene analysis showed that prover exon 13 had c.2390_2390delC heterozygote deletion mutation(p.Pro798Leufs*13)and exon 25 had c.6665A>G heterozygote missense mutation(p.Asp2222Gly).The father and sister were c.2390_2390delC heterozygotes,and the mother and son were c.6665A>G heterozygotes.The ratio of thrombin generation delay and peak reaching time was significantly higher in the proband.Meanwhile,the online bioinformatics software indicated that the frameshift variant was disease-causing.Conclusion Heterozygous deletion mutation in p.Pro798Leufs*13 and the p.Asp2222Gly heterozygous missense mutation may be associated with reduced plasma FⅤlevels in this family.