摘要:
Objective To explore molecular etiology and clinical characteristics of two pedigrees affected with hereditary factor Ⅶ (FⅦ) deficiency.Methods The nine exons and flanking sequences of the F7 gene of the probands were amplified by PCR.The amplicons were analyzed by direct sequencing.Suspected mutations were subjected to SWISS-MODEL modeling and analysis of protein structure change by Pymol software and conservation of amino acids across various species.Results For proband of pedigree 1,the prothrombin time (PT),FⅦ activity (FⅦ ∶ C) and FⅦ antigen (FⅦ ∶ Ag) were 36.3 s,3%,53.56%,respectively.Sequencing revealed a compound heterozygous variants of c.80_ 81delCT and c.1371G>T (p.Arg439Ser).His son carried a heterozygous c.1371G>T (p.Arg439Ser) variant.For proband of pedigree 2,the PT,FⅦ ∶ C and FⅦ ∶ Ag were 22.3 s,4%,1.58%,respectively.Sequencing has revealed a compound heterozygous c.278G>T (p.Arg75Met) missense variant in exon 3 and c.1278T>G (p.His408Gln) in exon 9 of the F7 gene.His mother and son both carried a heterozygous c.278G> T (p.Arg75Met) variant.Three-dimensional simulation and homology analysis revealed that the p.Arg439Ser and p.Arg75Met can respectively alter part of hydrogen bonds and two highly conserved amino acids.Conclusion Two novel heterozygous missense variants of the F7 gene [c.1371G>T (p.Arg439Ser) and c.278G>T (p.Arg75Met)] probably account for the decrease of factor Ⅶ in the two pedigrees.%目的 对2例遗传性凝血因子Ⅶ(factorⅦ,FⅦ)缺陷症患者家系进行临床表型和基因变异分析,并探讨其分子发病机制.方法 对先证者F7基因第1~9外显子及其侧翼序列进行PCR扩增、纯化和测序,寻找变异位点,对于新发现的错义变异位点排除多态性后,采用SWISS-MODEL建模,用Pymol软件分析蛋白结构的改变,同时分析该位点氨基酸在物种间的保守性.结果 家系1先证者凝血酶原时间(prothrombin time,PT)、凝血因子Ⅶ活性(FⅦactivity,FⅧ∶C)和凝血因子Ⅶ抗原(FⅦantigen,FⅦ∶Ag)分别为36.3 s、3%和53.56%;测序结果显示先证者F7基因第1外显子c.80 81delCT和第9外显子c.1371G>T(p.Arg439Ser)的复合杂合变异,其儿子携带c.1371G>T(p.Arg439Ser)杂合变异.家系2先证者的PT 22.3 s、FⅦ∶C4%和FⅦ∶Ag 1.58%;携带F7基因第3外显子c.278G>T (p.Arg75Met)和第9外显子c.1278T>G(p.His408Gln)的复合杂合错义变异,先证者母亲和儿子携带c.278G>T(p.Arg75Met)杂合变异.三维模拟软件分析提示p.Arg439Ser和p.Arg75Met会引起局部基团氢键的改变,物种间蛋白质同源性分析也表明这两个氨基酸高度保守.结论 F7基因c.1371G>T(p.Arg439Ser)和c.278G>T(p.Arg75Met)变异均为未报道过的新变异,推测这两种变异可能会影响Ⅶ因子的功能,可能是两先证者的致病原因.