纤维蛋白原FGB基因插入突变所致遗传性无纤维蛋白原血症的发病机制  

Congenital afibrinogenemia caused by a novel insertion mutation in the FGB gene

作　　者：张剑[1] 赵小娟[1] 王兆钺[1] 余自强[1] 曹丽娟[1] 马珍妮[1] 张杰[1] 张威[1] 白霞[1] 阮长耿[1] 

机构地区：[1]苏州大学附属第一医院、江苏省血液研究所,卫生部血栓与止血重点实验室,215006

出　　处：《中华血液学杂志》2013年第9期751-756,共6页Chinese Journal of Hematology

基　　金：基金项目：国家自然科学基金（81070395）;江苏高校优势学科建设丁程项目;江苏省临床医学中心（ZX201102）;江苏省科技厅生命健康科技专项基金（BL2012005）

摘　　要：目的探讨一个遗传性无纤维蛋白原血症家系的分子发病机制。方法应用Clauss法测定血浆纤维蛋白原活性，应用免疫比浊法测定纤维蛋白原抗原。提取先证者及其家系成员外周血DNA，PCR扩增纤维蛋白原FGA、FGB和FGG基因所有外显子和侧翼序列，构建纤维蛋白原野生型和突变型表达载体。在先证者血浆中加入凝血酶进行纤维蛋白聚集曲线测定；应用Westernblot分析血浆纤维蛋白原，用野生型或FGB突变型质粒转染COS-7细胞，用Westernblot和ELISA法检测转染后的细胞裂解液及细胞培养上清中纤维蛋白原的表达。结果先证者APTT、PT、凝血酶时间明显延长；血浆纤维蛋白原活性及纤维蛋白原抗原检测结果均为0；先证者FGB基因2号外显子核苷酸2833～2834之间插入GTTT（纯合突变），先证者父亲、母亲、胞弟和儿子为杂合突变；凝血酶诱导的血浆纤维蛋白聚集曲线显示患者血浆无纤维蛋白聚集；Westernblot分析显示，非还原条件下先证者血浆缺乏完整的纤维蛋白原分子和纤维蛋白原半分子，在还原条件下未检出截短的BB链。在转染突变型质粒的COS-7细胞裂解液中检出异常纤维蛋白原分子（相对分子质量〉340000），细胞培养上清中未检出异常纤维蛋白原。野生型和突变型质粒转染的COS．7细胞裂解液中纤维蛋白原含量差异无统计学意义[（2．47±0．30）μg／ml对（2．65±0．60）μg／ml，P=0．0889]；转染突变型质粒的COS-7细胞培养上清中纤维蛋白原含量低于转染野生型质粒的COS-7细胞，差异有统计学意义[（0．01±0．01）μg／ml对（3．80±0．80）μg／ml，P=-0．0001]。结论纤维蛋白原FGB基因插入突变是该家系遗传性无纤维蛋白原血症的分子发病机制；该突变导致纤维蛋白原分子合成异常、组装及分泌障碍。Objective To investigate the genetic defect and its mechanism in a patient with congenital afibrinogenemia. Methods The plasma fibrinogen activity and antigen of the patient was determined using the Clauss method and immuno-nephelometric assay, respectively. Genomic DNA was isolated from peripheral blood of the proband and his related family members. All exons and exon-intron boundaries of the three fibrinogen genes （FGA, FGB, FGG） were amplified by PCR followed by direct sequencing. Thrombin fibrin aggregation curve were detected in the plasma of the patient. Wild-type and mutation type fibrinogen vectors were constructed, and then transfected into COS-7 cells. The wild-type and mutant proteins from the culture media and cell lysates were tested by Western blot and ELISA. Results APTT, PT, TT were significantly longer in the proband. Plasma fibrinogen activity and antigen of the patient could not be detected using the Clauss method and immuno-nephelometry, respectively. Gene analysis revealed that a novel homozygous GTTT insertion between nucleotides 2833 and 2834 in FGB exon 2 in the proband. The proband＇ s father, mother, brother and son were heterozygous. The polymerization curves of the patient did not show a lag phase or final turbidity, compared with the normal controls. Western blot analysis showed the lack of complete half-molecules of the fibrinogen molecule and fibrinogen in patient＇ s plasma under non-reducing conditions. It also could not detect the truncated Bβ chain under reducing conditions. Abnormal fibrinogen molecule （molecule weight 〉340 000） were found in transfected COS-7 cells by Western blot, which indicated that the mutation caused the abnormal intracellular fibrinogen molecule assembly. The fibrinogen band was absent in culture media transfected by the mutation. Fibrinogen levels of mutant fibrinogen were no significant different from those of wild-type fibrinogen in cell lysates by EL1SA analysis L （2.47±0.30） μg/ml for （2.65±0.60）μg/ml, P =0.0889] ; However,

关 键 词：纤维蛋白原缺乏血症 遗传性疾病 先天性 突变 

分 类 号：R596.1[医药卫生—内科学]