Genetic analysis of a Chinese pedigree affected with Congenital coagulation factor XII deficiency due to a c.1A>G start codon variant of F12 gene / 中华医学遗传学杂志

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.

Analysis of F12 gene variants and molecular mechanisms in patients with coagulation factor Ⅻ deficiency / 中华医学遗传学杂志

OBJECTIVE@#To analyze the sequence of the F12 gene and molecular mechanism for 20 patients with coagulation factor Ⅻ (FⅫ) deficiency.@*METHODS@#The patients were selected from the outpatient department of the Second Hospital of Shanxi Medical University from July 2020 to January 2022. The activity of coagulation factor Ⅷ (FⅧ:C), factor Ⅸ (FⅨ:C), factor Ⅺ (FⅪ:C) and factor Ⅻ (FⅫ:C) were determined by using a one-stage clotting assay. All exons and 5' and 3' UTR of the F12 gene were analyzed by Sanger sequencing to detect the potential variants. Bioinformatic software was used to predict the pathogenicity of the variants, conservation of amino acids, and protein models.@*RESULTS@#The FⅫ:C of the 20 patients has ranged from 0.07% to 20.10%, which was far below the reference values, whilst the other coagulation indexes were all normal. Sanger sequencing has identified genetic variants in 10 patients, including 4 with missense variants [c.820C>T (p.Arg274Cys), c.1561G>A (p.Glu521Lys), c.181T>C (p.Cys61Arg) and c.566.G>C (p.Cys189Ser)], 4 deletional variants c.303_304delCA(p.His101GlnfsX36), 1 insertional variant c.1093_1094insC (p.Lys365GlnfsX69) and 1 nonsense variant c.1763C>A (p.Ser588*). The remaining 10 patients only harbored the 46C/T variant. The heterozygous c.820C>T(p.Arg274Cys) missense variant in patient 1 and the homozygous c.1763C>A (p.Ser588*) nonsense variant in patient 2 were not included in the ClinVar and the Human Gene Mutation Database. Bioinformatic analysis predicted that both variants were pathogenic, and the corresponding amino acids are highly conserved. The protein prediction models suggested that the c.820C>T (p.Arg274Cys) variant may affect the stability of the secondary structure of FⅫ protein by disrupting the original hydrogen bonding force and truncating the side chain, leading to changes in the vital domain. c.1763C>A (p.Ser588*) may produce a truncated C-terminus which may alter the spatial conformation of the protein domain and affect the serine protease cleavage site, resulting in extremely reduced FⅫ:C.@*CONCLUSION@#Among individuals with low low FⅫ:C detected by one-stage clotting assay, 50% have harbored variants of the F12 gene, among which the c.820C>T and c.1763C>A were novel variants underlying the reduced coagulating factor FⅫ.

Analysis of A Pedigree with Hereditary Coagulation Factor Ⅻ Deficiency Caused by Compound Heterozygous Mutations / 中国实验血液学杂志

OBJECTIVE@#To analysis clinical phenotype and potential genetic cause of a family affected with hereditary coagulation factor Ⅻ deficiency.@*METHODS@#The prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FIB), D-Dimer (D-D), coagulation factor Ⅻ activity (FⅫ:C) and coagulation factor Ⅻ antigen (FⅫ:Ag) were determined for phenotype diagnosis of the proband and his family members(3 generations and 5 people). Targeted capture and whole exome sequencing were performed in peripheral blood sample of the proband. Possible disease-causing mutations of F12 gene were obtained and further confirmed by Sanger sequencing. The corresponding mutation sites of the family members were analyzed afterwards. The online bioinformatics software AutoPVS1 and Mutation Taster was used to predict the effects of mutation sites on protein function.@*RESULTS@#The APTT of the proband was significantly prolonged, reaching 180.9s. FⅫ:C and FⅫ:Ag of the proband was significantly reduced to 0.8% and 4.17%, respectively. The results of whole exome sequencing displayed that there were compound heterozygous mutations in F12 gene of the proband, including the c.1261G＞T heterozygous nonsense mutation in exon 11 (causing p.Glu421*) and the c.251dupG heterozygous frameshift mutation in exon 4 (causing p.Trp85Metfs*53). Both mutations are loss of function mutations with very strong pathogenicity, leading to premature termination of the protein. AutoPVS1 and Mutation Taster software predicted both mutations as pathogenic mutations. The results of Sanger sequencing revealed that c.1261G＞T heterozygous mutation of the proband was inherited from his mother, for which his brother and his daughter were c.1261G＞T heterozygous carriers. Genotype-phenotype cosegregation was observed in this family.@*CONCLUSION@#The c.1261G＞T heterozygous nonsense mutation in exon 11 and the c.251dupG heterozygous frameshift mutation in exon 4 of the F12 gene probably account for coagulation factor Ⅻ deficiency in this family. This study reports two novel pathogenic F12 mutations for the first time worldwide.

Short-term prophylaxis for delivery in pregnant women with hereditary angioedema with normal C1-inhibitor / Profilaxia de curto prazo para o parto em grávidas com angioedema hereditário com inibidor de C1 normal

Abstract Objective To verify the efficacy of short-term prophylaxis for vaginal or cesarean section childbirth with plasma-derived C1-inhibitor concentrate in pregnant women. They should have hereditary angioedema (HAE) and normal plasma C1-inhibitor. Methods Case report of pregnant women diagnosed with HAE with normal C1- inhibitor who had been treated with intravenous C1-inhibitor concentrate for prophylaxis of angioedema attacks when hospitalized for delivery. The exon 9 of the Factor 12 (F12) genotyping gene was performed by automatic sequencing in all patients. Results Three cases of pregnant women with HAE with normal serum level of C1- inhibitor are reported. The genetic test detected the presence of a pathogenic mutation in the F12 gene. Deliveries occurred uneventfully and patients had no HAE symptoms in the following 72 hours. Conclusion C1-inhibitor concentrate could be useful to prevent angioedema attacks during and after delivery.

Resumo Objetivo Verificar a eficácia da profilaxia de curto prazo para o parto vaginal ou cesáreo com inibidor de C1 derivado de plasma concentrado em mulheres grávidas. Eles devem ter angioedema hereditário e inibidor normal de C1 no plasma. Métodos Relato de caso de gestantes diagnosticadas com angioedema hereditário com inibidor de C1 normal que foram tratadas com inibidor intravenoso de concentrado de C1 para profilaxia de ataques de angioedema quando hospitalizadas para o parto. O exon 9 do gene de genotipagem do fator 12 (F12) foi realizado por sequenciamento automático em todos os pacientes. Resultados Três casos de gestantes com angioedema hereditário com nível sérico normal de inibidor de C1 são relatados. O teste genético detectou a presença de uma mutação patogênica no gene F12. Os partos ocorreram sem intercorrências e as pacientes não apresentaram sintomas hereditários de angioedema nas 72 horas seguintes. Conclusão O concentrado de inibidor de C1 pode ser útil para prevenir ataques de angioedema durante e após o parto.