摘要
目的 对一个遗传性低纤维蛋白原血症家系进行突变分析,探讨其分子发病机制.方法 用STA-R全自动血凝分析仪检测先证者及其家系成员（共3代8人）的凝血酶原时间（prothrombin time,PT）、活化部分凝血活酶时间（activated partial thromboplastin time,APTT）、凝血酶时间（thrombin time,TT）、纤溶酶原活性（plasminogen activity,PLG：A）、D-二聚体（D-Dimer,D-D）和纤维蛋白降解产物（fibrin degradation products,FDP）;用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（fibrinogen antigen,Fg∶Ag）水平;用PCR法扩增纤维蛋白原的FGA、FGB和FGG基因的所有外显子和侧翼序列.对PCR产物纯化后测序,发现突变后进行反向测序进行验证.采用Swiss 软件对突变进行模型分析.结果 先证者PT正常,APTT、TT轻度延长,Fg∶C和Fg∶Ag明显降低.先证者的父亲、姐姐、儿子、外甥女的Fg∶C均有不同程度降低.其母亲各项指标均在正常参考范围.基因分析发现先证者FGG基因第7外显子5864位A＞C杂合突变,导致纤维蛋白原D结构域的232位赖氨酸突变为苏氨酸（Lys232Thr）;其父亲、姐姐、儿子、外甥女均为Lys232Thr杂合子,母亲为野生型.蛋白质模型分析显示Lys232Thr突变并未破坏氨基酸之间天然的氢键联系,但改变了相互静电作用力,并使该位点氨基酸侧链变短,从而增加了蛋白质的不稳定性.结论 该遗传性低纤维蛋白原血症患者FGG基因Lys232Thr错义突变与其血浆纤维蛋白原活性和抗原水平降低有关.
Objective To identify the genetic mutation underlying congenital hypofibrinogenamia in a Chinese pedigree.Methods Standard coagulation tests including the prothrombin time （PT）,activated partial thromboplastin time （APTT）,thrombin time （TT）,plasminogen activity （PLG ∶ A）,D-Dimer （DD） and fibrin degradation products （FDP） were tested with fresh plasma using a STA-R analyzer.The activity of fibrinogen （Fg ∶ C） and fibrinogen antigen （Fg ∶ Ag） were measured respectively with the Clauss method and immunoturbidimetry.All exons and exon-intron boundaries of the fibrinogen Aα-,Bβ-,and γ-chain genes （FGA,FGB and FGG） were amplified by PCR followed by direct sequencing.Suspected mutation was confirmed by reverse sequencing and analyzed with a Swiss-PdbViewer.Results The PT level in the proband was normal,while the APTT and TT were slightly prolonged.The functional and antigen fibrinogen levels were both significantly reduced （0.91 g/L and 0.95 g/L,respectively）.Similar abnormalities were also found in her father,elder sister,son and niece.The coagulant parameters of her mother were all within the normal range.Genetic analysis has reveled a heterozygous A〉 C change at nucleotide 5864 in exon 7 of γ gene in the proband,predicting a novel Lys232Thr mutation.The proband＇s father,elder sister,son and niece were all carriers of the same mutation.Protein model analysis indicated that the Lys232Thr mutation did not disrupt the native network of hydrogen bonds,but has changed the mutual electrostatic forces,resulting in increased instability of the protein.Conclusion The heterozygous Lys232Thr mutation identified in the FGG gene probably underlies the hypofibrinogenemia in this pedigree.
出处
《中华医学遗传学杂志》
CAS
CSCD
北大核心
2015年第3期331-334,共4页
Chinese Journal of Medical Genetics
基金
温州市科技计划项目（Y20100284）
