OBJECTIVE: To explore the clinical characteristics and genetic etiology of a consanguineous Chinese pedigree affected with Congenital coagulation factor XII (XII) deficiency. METHODS: Members of the pedigree who had visited Ruian People's Hospital on July 12, 2021 were selected as the study subjects. Clinical data of the pedigree were reviewed. Peripheral venous blood samples were taken from the subjects. Blood coagulation index and genetic testing were carried out. Candidate variant was verified by Sanger sequencing and bioinformatic analysis. RESULTS: This pedigree has comprised 6 individuals from 3 generations, including the proband, his father, mother, wife, sister and son. The proband was a 51-year-old male with kidney stones. Blood coagulation test showed that his activated partial thromboplastin time (APTT) was significantly prolonged, whilst the FXII activity (FXII:C) and FXII antigen (FXII:Ag) were extremely reduced. The FXII:C and FXII:Ag of proband's father, mother, sister and son have all reduced to about half of the lower limit of reference range. Genetic testing revealed that the proband has harbored homozygous missense variant of c.1A>G (p.Arg2Tyr) of the start codon in exon 1 of the F12 gene. Sanger sequencing confirmed that his father, mother, sister and son were all heterozygous for the variant, whilst his wife was of the wild type. By bioinformatic analysis, the variant has not been included in the HGMD database. Prediction with SIFT online software suggested the variant is harmful. Simulation with Swiss-Pbd Viewer v4.0.1 software suggested that the variant has a great impact on the structure of FXII protein. Based on the Standards and Guidelines for the Interpretation of Sequence Variants: A Joint Consensus Recommendation of the American College of Medical Genetics and Genomics (ACMG), the variant was rated as likely pathogenic. CONCLUSION The c.1A>G (p.Arg2Tyr) variant of the F12 gene probably underlay the Congenital FXII deficiency in this pedigree. Above finding has further expanded the spectrum of F12 gene variants and provided a reference for clinical diagnosis and genetic counseling for this pedigree.
Male ; Female ; Humans ; Middle Aged ; Factor XII/genetics* ; Pedigree ; Codon, Initiator ; East Asian People ; Mothers ; Factor XII Deficiency/genetics* ; Mutation

Objective To analyze the phenotype and genotype of inherited dysfibrinogenemia pedigree associated with a novel heterozygous and deletion mutation in the FGG gene,and to investigate its molecular mechanism.Methods The clinical data were collected from the proband found at our hospital and her family members in April 2016.The activity plasma fibrinogen(Fg:C), activated partial thromboplastin time(APTT),prothrombin time(PT), thrombin time(TT)were detected by coagulation method and the antigen plasma fibrinogen(Fg:Ag), D-Dimer(D-D), fibrinogen degradation products (FDPs)were analyzed by immunoturbidimetry method.All of the exons and exon-intron boundaries of the genes of FGA, FGB and FGG with the fibrinogen(Fg)were amplified by PCR and followed by direct sequencing.And further verification were performed by cloning sequence and non-denatured polyacrylamide gel electrophoresis and silver staining.The conservatism of mutated gene locus were analyzed by ClustalX-2.1-win.The change of the protein spatial structure and the intermolecular forces with mutation were analyzed by Pymol.Results The Fg:C of the proband was significantly reduced(0.30 g/L)and the Fg:Ag of the proband was normal(2.00 g/L).Their Fg:C were both significantly reduced and the Fg:Ag were both normal(0.42 g/L,2.09 g/L & 0.47 g/L,2.42 g/L, respectively), these were found in her mother and grandma.Genetic analysis revealed a novel heterozygous and deletion mutation with c.944 _c.952 delCCTTTGATG in exon 8 of FGG gene in the proband,predicting a heterozygous 289_291delAla,Phe,Asp mutation.The same mutations were carried by her mother and grandma, but her father and grandpa were normal.Homology analysis indicated that the Ala 289,Phe290 and Asp291 were maintained highly conservative in homogenous species.Protein model analysis found that the original hydrogen bonds were disappeared when the deletion mutation happened with the Ala 289,Phe290 and Asp291.Conclusion The heterozygous and deletion mutation with 289_291delAla,Phe,Asp in the γchain of fibrinogen were identified that could cause the rearrangement of the Fg molecular space structure and the reduction of the structure stability,so the mutation probably underly the dysfibrinogenemia in this pedigree.(Chin J Lab Med,2018, 41:305-311)

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.