两个遗传性蛋白C缺陷症家系临床表型和基因型变化的研究

目的对两个遗传性蛋白C（PC）缺陷症家系进行临床表型和基因突变检测。方法血浆蛋白C活性（PC：A）和抗原（PC：Ag）分别用发色底物法和ELISA法测定，蛋白S活性（PS：A）和抗凝血酶活性（AT：A）用发色底物法测定。用PCR法对先证者PC基因的9个外显子及其侧翼、内含子序列进行扩增，PCR产物纯化后直接测序，检测其基因突变。仅对先证者家系成员基因突变部位的外显子及其侧翼序列进行PCR扩增和测序。突变位点经限制性内切酶酶切分析或直接测序证实。结果先证者1（Ⅱ7）的PC：A和PC：Ag分别为1．2％和0。基因测序显示，先证者1在PC基因外显子5存在C3135G杂合错义突变，致C（TGC）64W（TGG），同时在外显子7存在T6128G杂合错义突变，致F（TTC）139V（GTC）。家系成员中，先证者的父亲（Ⅰ4）和女儿（Ⅲ3）存在T6128G杂合突变，先证者的舅舅（Ⅱ）存在C3135G杂合突变，先证者丈夫（Ⅱ8）存在外显子76161-6163或6164～6166AAG（K150或K151）杂合缺失，而其女儿（Ⅲ3）亦有此突变。先证者2（Ⅲ1）的PC：A和PC：Ag分别为50．3％、1．9mg／L，基因测序显示其存在K150或K151杂合缺失，该突变遗传自其父亲。2个家系中所有成员在PC基因启动子区中存在-1654C／T、-1641A／G、-1476A／T多态性，先证者2为CC／GG／TT纯合型。限制性内切酶PSp5Ⅱ酶切分析显示T6168G不是多态性。所有成员的PS：A和AT：A均在正常范围。结论复合杂合性PC基因突变（C64W和F139V）是导致先证者1遗传性Ⅰ型PC缺陷症的原因，杂合性Lys150或151缺失突变和PC基因启动子区CC／GG／TI纯合多态性是致先证者2遗传性Ⅰ型PC缺陷症的原因。C64W为国际首次报道，F139V、K150或151缺失突变为国内首次报道。

Analysis of phenotype and genotype in two Chinese pedigrees with hereditary protein C deficiency

OBJECTIVE: To identify the phenotype and gene mutation in two Chinese pedigrees with hereditary protein C deficiency. METHODS: The plasma level of protein C activity (PC: A) , protein C antigen (PC: Ag), protein S activity (PS: A), and antithrombin activity (AT: A) of the probands and their family members were detected using chromogenic assay and ELISA, respectively. All of the nine exons and intron-exon boundaries of protein C gene were amplified by PCR and analyzed by direct sequencing of the probands. Restriction enzyme site analysis was used to confirm the mutation. RESULTS: The plasma PC: A and PC: Ag for proband 1 was 1.2% and 0, respectively. Compound heterozygous mutations, C(TGC)64W (TGG) and F(TTC) 139V(GTC) , were identified in her, the former being inherited from the maternal side and the later the paternal side. Further genetic analysis showed that her husband ( II 8) had the heterozygous deletion mutation (K150 or 151 Del) in exon 7, her daughter had the same heterozygous deletion mutation and a F139V. The plasma PC: A and PC: Ag for proband 2 was 50. 3% and 1.9 mg/L, respectively. He had the heterozygous Lys150 or Lys151 deletion mutation, which was inherited from his father. Polymorphisms of C/T at position - 1654, A/G at - 1641 , and A/T at - 1476A/T in the promoter region of protein C were confirmed in all members of the two pedigrees, of which, proband 2 had homozygous CC/GG/TT. The F139V mutation was confirmed by restriction enzyme site analysis and polymorphism for this mutation was excluded. PS: A and AT: A were in normal range for all members. CONCLUSION: Compound heterozygous mutation C64W and F139V of protein C gene lead to type I hereditary protein C deficiency for proband 1. K150 or 151 deletion mutation and polymorphyism of CC/GG/TT might lead to type I hereditary protein C deficiency for proband 2. C64W is a novel mutation for protein C gene. F139V and K150 or 151 deletion mutation are reported for the first time in China.