一个纤维蛋白原γ链g．7590G〉T杂合突变导致遗传性低纤维蛋白原血症家系的分析  

Analysis of a pedigree affected with congenital hypofibrinogenemia due to heterozygous Ser313Ile mutation of fibrinogen γ chain gene

作　　者：朱丽青[1] 赵秘胜 程小丽 虞丹丹[1] 李小龙[1] 徐斐[1] 王金果[1] 王明山[1] Zhu Liqing , Zhao Misheng , Cheng Xiaoli , Yu Dandan , Li Xiaolong , Xu Fei , Wang Jinguo, Wang Mingshan(Clinical Laboratory, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, China （Zhu LQ, Cheng XL, Yu DD, Li XL, Xu F, Wang JG, Wang MS）~ Clinical Laboratory, Wenzhou People＇s Hospital, Wenzhou , Zhejiang 325000, China （Zhao MS)

机构地区：[1]温州医科大学附属第一医院检验科,浙江325000 [2]浙江省温州市人民医院检验科,325000

出　　处：《中华医学遗传学杂志》2018年第2期179-183,共5页Chinese Journal of Medical Genetics

基　　金：国家自然科学基金（81501810）;浙江省自然科学基金（LQ15H200001）

摘　　要：目的对一个遗传性低纤维蛋白原血症家系进行基因突变分析，并探讨其发病的分子机制。方法采集先证者及其家系成员（3代共9人）的外周血样，用自动化血凝仪分析凝血酶原时间（prothrombin time，PT）、活化部分凝血活酶时间（activated partial thromboplastin time，APTT）和凝血酶时间（thrombin time，TT）；用凝血酶凝固法（Clauss法）与免疫比浊法分别测定血浆纤维蛋白原的活性（fibrinogen activity，Fg∶C）和抗原水平（fibrinogen antigen，Fg∶Ag）；用PCR扩增纤维蛋白原FGA、FGB和FGG基因的所有外显子及其侧翼序列，对PCR产物进行纯化后直接测序；用Swiss软件对突变蛋白进行预测。结果先证者APTT、PT和TT均延长，Fg∶C（0.69 g/L）和Fg∶Ag（0.72 g/L）明显降低；其母亲、外祖母Fg∶C分别为0.99 g/L和0.83g/L，Fg∶Ag为1.02 g/L和0.87 g/L，均有不同程度的降低。其他家系成员的凝血指标均在正常范围。先证者FGG基因第8外显子存在7590位置的G〉T杂合突变，导致纤维蛋白原D结构域的313位丝氨酸突变为异亮氨酸（Ser313Ile）；其母亲和外祖母亦为Ser313Ile杂合子，其他家系成员则为野生型。模型分析显示Ser313突变为Ile后，同Asn319、Asp320之间的氢键消失，可能影响钙离子的正常结合。此外，该突变导致中性非极性的Ser变成了非极性、疏水性的Ile，使侧链变长，可能影响纤维蛋白原的折叠、构象及稳定性，导致血浆纤维蛋白原水平降低。结论纤维蛋白原γ链Ser313Ile的杂合突变是引起该家系遗传性低纤维蛋白原血症的原因。ObjectiveTo explore the genetic basis for a Chinese pedigree affected with congenital hypofibrinogenamia.MethodsPeripheral blood samples were collected from 9 members from the pedigree. Routine coagulation tests including activated partial thromboplastin time （APTT）, thrombin time （TT）, the prothrombin time （PT） were carried out. The activity of fibrinogen （Fg∶C） was measured using Clauss method, and fibrinogen antigen （Fg∶Ag） was measured with immunoturbidimetry. All exons and exon-intron boundaries of the fibrinogen Aα, Bβ and γ chain genes were amplified using PCR, which was followed by direct sequencing. Suspected mutation was confirmed by reverse sequencing. The mutant fibrinogen was analyzed with Swiss-PdbViewer. ResultsThe proband showed prolonged APTT, PT and TT. Her functional fibrinogen （Fg∶C） and antigen fibrinogen （Fg∶Ag） levels were reduced to 0.69 g/L and 0.72 g/L, respectively. Her mother and grandmother also had a low levels of fibrinogen, which were 0.99 g/L and 0.83 g/L for Fg∶C, 1.02 g/L and 0.87 g/L for Fg∶Ag, respectively. The results of other members from the pedigree were all within the normal range. Genetic analysis reveled a heterozygous G〉T mutation at nucleotide 7590 in exon 8 of γ gene in the proband, which was predicted to be a novel Ser313Ile mutation. The mutation was also found in her mother and grandmother. Model analysis showed that the Ser313Ile mutation disturbed the hydrogen bonds between Ser313, Asn319 and Asp320. Moreover, the mutation also altered the mutual electrostatic force and affected the folding and instability of the mutant fibrinogen.Conclusion The heterozygous Ser313Ile mutation probably underlies the hypofibrinogenemia in this pedigree.

关 键 词：遗传性低纤维蛋白原血症 家系 基因突变 模型分析 

分 类 号：R554.5[医药卫生—血液循环系统疾病]