Yang Lihong, Jin Saiyan, Ji Weidan, Cheng Xiaoli, Li Xiaolong, Jin Yanhui, Wang Mingshan
Center of Laboratory Medicine,the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325015, China. Email:
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2018 Feb 10;35(1):69-73. doi: 10.3760/cma.j.issn.1003-9406.2018.01.015.
OBJECTIVE To analyze the laboratory phenotype and FXII gene mutation in a consanguineous Chinese pedigree affected with factor XII (FXII) deficiency. METHODS Activated partial thromboplastin time (APTT), FXII activity (FXII:C) and FXII antigen (FXII:Ag) of the proband and her family members (10 individuals from 3 generations) were determined. Sanger sequencing was used to detect potential mutation within the 14 exons, their flanking regions and 5',3'-untranslated regions of the FXII gene. Suspected mutations were verified by backward sequencing. Conservation of the amino acids were analyzed with ClustalX-2.1-win. Four online bioinformatics software (PolyPhen-2, PROVEAN, SIFT and MutationTaster) were used to assess the impact of the mutations on the protein function. RESULTS The APTT of the proband and her elder brother have prolonged to 61.6 s and 68.6 s,and their FXII:C and FXII:Ag have decreased to 12%, 10% and 11%, 10%, respectively. The APTT of the paternal grandmother, maternal grandmother, father, mother, elder paternal aunt and elder maternal aunt were all normal, but their FXII:C and FXII:Ag have reduced to half of the normal value. Gene sequencing found that the proband and her elder brother have both carried a homozygous missense c.1078G>A (p.Gly341Arg) mutation in exon 10 of the FXII gene, for which the paternal grandmother, maternal grandmother, father, mother, elder paternal aunt and elder maternal aunt were heterozygous. Bioinformatic analysis suggested that the Gly341 is highly conserved, while p.Gly341Arg is a harmful mutation which may cause disease by affecting the function of FXII protein. CONCLUSION Homozygous p.Gly341Arg mutation, caused by consanguineous marriage, probably underlies the congenital FXII deficiency in this pedigree.
目的 分析一个患凝血因子Ⅻ（FXII）缺乏症的中国近亲家系的实验室表型及FXII基因突变情况。方法 检测先证者及其家系成员（3代10人）的活化部分凝血活酶时间（APTT）、FXII活性（FXII:C）和FXII抗原（FXII:Ag）。采用桑格测序法检测FXII基因14个外显子及其侧翼区域和5'、3'-非翻译区的潜在突变。通过反向测序验证可疑突变。用ClustalX-2.1-win分析氨基酸的保守性。使用4种在线生物信息学软件（PolyPhen-2、PROVEAN、SIFT和MutationTaster）评估突变对蛋白质功能的影响。结果 先证者及其哥哥的APTT分别延长至61.6 s和68.6 s，FXII:C和FXII:Ag分别降至12%、10%和11%、10%。先证者的祖母、外祖母、父亲、母亲、大姑和大姨的APTT均正常，但FXII:C和FXII:Ag均降至正常值的一半。基因测序发现，先证者及其哥哥在FXII基因第10外显子均携带纯合错义c.1078G>A（p.Gly341Arg）突变，其祖母、外祖母、父亲、母亲、大姑和大姨为杂合子。生物信息学分析提示，Gly341高度保守，而p.Gly341Arg是有害突变，可能通过影响FXII蛋白功能致病。结论 该家系先天性FXII缺乏症可能由近亲结婚导致的纯合p.Gly341Arg突变引起。
