蛋白C基因G12918A突变所致Ⅰ型遗传性蛋白C缺陷症

Type Ⅰ hereditary protein C deficiency caused by G12918A mutation of Protein C gene

目的研究一个遗传性蛋白 C(PC)缺陷症家系的遗传表型和基因特征。方法 PC 抗原(PC:Ag)和 PS 抗原(PS:Ag)检测采用酶联免疫吸附试验,AT 抗原(AT:Ag)测定采用免疫比浊法测定;PC 活性(PC:A)、PS 活性(PS:A)和 AT 活性(AT:A)采用发色底物法在 Sysmex1500全自动血凝仪上进行测定。用聚合酶链反应扩增3代家系10个成员 PC 基因各个外显子及侧翼序列,用直接测序法检测其基因突变点。结果该家系3代10名成员中,有8名 PC 抗原水平在1.06～1.92 mg/L(参考值3.00～6.00 mg/L)之间,PC 活性在41%～67%(参考值70%～140%)之间,明显低于正常参考范围;而 PS:Ag 和 PS:A、AT:Ag 和 AT:A 均在正常参考值范围内。PC 基因测序分析:8名成员存在Ⅸ号外显子第12 918位核苷酸 G→T突变,密码子 TGG→TGA,使第372位 Trp→Stop;并在基因启动子区存在2 405C/T、2 418A/G、2 583A/T 的多态性。结论该家系为Ⅰ型遗传性 PC 缺陷症,PC 基因Ⅸ号外显子存在第12 918位核苷酸 G→T突变,该突变是目前尚未报道的一个新的基因突变点;并在基因启动子区存在2 405C/T、2 418A/G、2 583A/T 的多态性。

Objective To investigate the phenotypes and genotypes of a hereditary protein C （PC） deficiency pedigree. Methods Immunoassay （ELISA）was used for PC antigen and PS antigen; Immunoturbidimetry assay was used for measuring AT antigen; Chromogenic substrate assay was used for measuring the activity of PC ,PS and AT in Sysmex 1500 automatic Blood Coagulation Analyzer. Polymerase chain reaction （PCR） for amplification of the fragment of each exon and side sequences of PC gene in 10 members of the 3 generations; Direct DNA sequencing was used to examine the mutation site. Results Among 10 members of the 3 generation pedigree, 8 of them had a PC： Ag level of 1.06-1.92 mg/L （normal references 3. 00-6. 00 mg/L）, the activity of PC was between 41% and 67% （ normal references 70% - 140% ） ,which was significantly lower than the normal references while the levels of PS： Ag,PS： A,AT： Ag and AT： A were all within normal range. DNA sequencing analysis showed that there was a G to T mutation in exon IX of the PC geue at 12 918 position in 8 members. This mutation resulted in the substitution of terminator TGA for TC, G which encoding tryptophan at 372 amino acid. There was a polymorphism in 2 405C/ T,2 418A/G,2 583A/T in the promoter area. Conclusions This pedigree is a type I hereditary protein C deficiency. There is a G12 918T mutation in exon IX of PC gene. This mutation is reported for the first time and there is a polymorphism in 2 405C/T,2 418A/G,2 583A/T in the promoter area.