新的双重杂合性FⅤ基因突变导致的重型遗传性FⅤ缺陷症

Severe hereditary coagulation factor Ⅴ deficiency caused by two novel heterozygous mutations

目的对一个遗传性凝血因子V(FV)缺陷症家系进行FV基因突变的检测。方法用活化部分凝血活酶时间(Am)，凝血酶原时间(PT)及FV促凝活性(FV：C)和FV抗原(FV：Ag)测定进行表型诊断；用PCR法对先证者FV基因25个外显子及其侧翼序列进行扩增，PCR产物纯化后直接测序，检测其基因突变。突变位点经限制性内切酶分析证实：结果先证者APTT 249．2s．PT46．6s。TT17．9s，Fg3．42g/L，FV：C0．1％，FV：Ag 1．5％，FⅡ：C99％，FⅦ：C110％、FⅧ：C95％、FⅨ：C88％、FX：C120％、vWF121％；FV外显子区共发现4个与基因文库Z99572序列不同的位点，其中位于exon13区的杂合性2238～2239de1AG导致移码突变和终止密码子的提前m现(Asp689stop)，位于exon23区的杂合性G6410T错义突变导致Gly2079 Val.家系分析表明前者遗传于母亲，后者遗传于父亲。结论2238～2239delAG导致的移码突变和G6410T导致的错义突变．是导致先证者FV缺陷的原因。这是2个导致遗传性FV缺陷症的新的FV基冈突变位点。

Objective To identify gene mutations of a pedigree with inherited factor Ⅴ(FⅤ) deficiency. Methods The activated partial thromboplastin time (APTT), prothrombin time (PT), FⅤ activity (FⅤ∶C) and FⅤ antigen (FⅤ∶Ag) tests were performed for phenotypic diagnosis. The genomic DNA was extracted from the peripheral blood of the proband and all the 25 exons and their flanks of FⅤ gene were amplified by polymerase chain reaction(PCR). The PCR products were screened by direct sequencing and the mutations were further confirmed by restriction enzyme digestion. Results APTT, PT, TT, FⅤ∶C, FⅤ∶Ag of the proband were 249.2 s, 46.6 s, 17.9 s, 0.1% and 1.5%, respectively. FⅡ, FⅦ, FⅧ, FⅨ, FⅩ activities, vWF and Fg were within normal ranges. Taking the GenBank Z99572 sequence as the reference, four mutations were identified in FⅤ gene of the profand. They were a heterozygous two bases deletion in exon 13 (2238~2239delAG ) introducing a frameshift and a premature stop at codon 689, and a heterozygous missense mutation in exon 23 (G6410T) resulting in the substitution of Gly for Val at codon 2079, respectively. The proband’s father and mother were heterozygous for G6410T and for 2238~2239delAG, respectively. Conclusion The severe FⅤ deficiency of the profand is caused by a frameshift mutation of 2238~2239delAG and a missense mutation of G6410T, which haven’t been identified before.