凝血因子Ⅺ基因内含子区受位剪切位点突变导致的遗传性凝血因子Ⅺ缺陷症

The inherited coagulation factorⅪ deficiency caused by intronic mutation IVS J-4delgttg

目的 探讨一个遗传性凝血因子Ⅺ (FⅪ )缺陷症患者及其家系成员中FⅪ基因突变。方法 用自动凝血仪检测患者及其家系成员凝血酶原时间 (PT)、活化部分凝血酶原时间 (APTT),一期法检测血浆FⅪ、FⅤ、FⅦ、FⅧ、FⅨ、FⅫ活性;采用ELISA法检测血浆FⅪ∶Ag。以外周血中抽提的基因组DNA为模板,PCR扩增FⅪ基因的所有外显子及其侧翼序列,用直接测序的方法查找突变。以RT PCR检测患者FⅪmRNA的水平,分析突变对FⅪmRNA剪切造成的影响。结果 患者及部分家系成员APTT延长,先证者及其兄血浆FⅪ∶C、FⅪ∶Ag均低于正常人的 10%,其父母血浆FⅪ∶C、FⅪ∶Ag均低于正常人的 50%。基因测序结果表明FⅪ基因内含子 10 3′端 4个碱基缺失 (IVSJ 4delgttg),先证者及其兄为纯合突变,其父母及侄女、外甥均为杂合型。在患者外周血中未能检测到FⅪmRNA。结论 该突变导致FⅪmRNA不能正常剪切,引起FⅪ转录本质和量的改变,不能合成正常的FⅪ,是导致该遗传性FⅪ缺陷症家系成员发病的分子遗传学基础。

Objective To identify gene defect in a Chinese pedigree of hereditary coagulation factor Ⅺ(FⅪ) deficiency. Methods The peripheral blood samples were collected from the proband and her family members. The plasma PT、APTT、 FⅪ∶C and FⅪ∶Ag were assayed. The FⅪ gene exons and exon intron boundaries of the proband were amplified by PCR and then sequenced directly. The mRNA of FⅪ in the peripheral blood was analyzed with RT PCR. Results The proband and some of her family members had prolonged APTT. The plasma FⅪ∶C and FⅪ∶Ag of the proband, her borther and her parents were lower than 10% and 50% of the normal values, respectively. Nucleotide sequence analysis revealed that the proband and her brother had a homozygous mutation of IVS J 4delgttg in FⅪ gene. The mutation was inherited from her parents who were heterozygotes. The mutation was not found in 60 normal subjects. No FⅪ mRNA was detected in peripheral blood sample of the proband. Conclusion The IVS J 4delgttg is a novel mutation causing FⅪ deficiency, which may interfere with mRNA splicing.