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OBJECTIVE@#To retrospectively analyze the clinical phenotypes and genetic variants in two Chinese pedigrees affected with Hereditary hypofibrinemia (IFD) and explore their molecular pathogenesis.@*METHODS@#Two probands and their pedigree members were admitted to the First Affiliated Hospital of Wenzhou Medical University on March 30, 2021 and May 27, 2021, respectively. Clinical phenotypes of the probands were collected, and blood clotting indexes of the probands and their pedigree members were determined. Variants of the FGA, FGB and FGG genes were analyzed by Sanger sequencing, and candidate variants were verified by sequence comparison. Bioinformatic software was used to analyze the conservation of the amino acids and pathogenicity of the proteins. Alteration in protein structure and intermolecular force before and after the variant was analyzed by simulating the protein model.@*RESULTS@#Proband 1, a 18-year-old male, had significantly low plasma fibrinogen activity (Fg:C) and plasma fibrinogen antigen (Fg:Ag), respectively at 0.80 g/L and 1.00 g/L. Proband 2, a 43-year-old male, had slightly low Fg:C and Fg:Ag at 1.35 g/L and 1.30 g/L, respectively. The Fg:C and Fg:Ag of proband 1's father, proband 2's father and son were also below the normal level. Genetic testing showed that proband 1 had harbored a heterozygous missense variant of c.688T>G (p.Phe230Val) in exon 7 of the FGG gene, which was inherited from his father. Proband 2, his father and son all had harbored a heterozygous variant of c.2516A>C (p.Asn839Thr) in exon 6 of the FGA gene. Homology analysis showed that the Phe230 and Asn839 residues were highly conserved among homologous species. Bioinformatic analysis predicted that both p.Phe230Val and p.Asn839Thr were pathogenic variants.@*CONCLUSION@#Analysis of protein simulation model showed that the p.Asn839Thr variant has changed the hydrogen bo`nd between the amino acids, thus affecting the stability of the protein structure. The heterozygous missense variants of p.Phe230Val and p.Asn839Thr probably underlay the IFD in the two pedigrees.
Subject(s)
Humans , Male , Amino Acids , East Asian People , Exons , Pedigree , Retrospective Studies , Afibrinogenemia/genetics , Mutation, Missense , Fibrinogen/geneticsABSTRACT
Objective:To analyze 12 antithrombins (AT) gene mutations that cause AT deficiency and discuss the relationship between the SERPINC1 gene. mutations and venous thrombotic events.Methods:This study belongs to case series of observational studies. Collected the clinical data of 12 AT deficiency cases in the First Affiliated Hospital of Wenzhou Medical University from April 2014 to April 2021 and collected the blood samples before treatment. The AT activity (AT: A) and AT antigen (AT: Ag) was detected by chromogenic substrate and immunoturbidimetry, respectively. The 7 exons and flanking sequences of the SERPINC1 gene were sequenced directly by PCR, the suspected mutations were validated by reverse sequencing. Analyzed the correlation between the SERPINC1 gene. mutations and venous thrombotic events and figured out the proportion.Results:The AT: A of the 12 patients all decreased significantly, ranging from 30% to 66%, and the AT: Ag of the 7 patients decreased accordingly, showing type Ⅰ AT deficiency, and the AT: Ag of the other 5 patients were normal, presented type Ⅱ AT deficiency. 12 mutations were found including 6 heterozygous mutations which were discovered for the first time: c.456_458delCTT(p.phe121del), c.318_319insT(p.Asn75stop), c.922G>T(p.Gly276Cys), c.938T>C (p.Met281Thr), c.1346T>A(p.Leu417Gln)and c.851T>C(p.Met252Thr). All 12 patients had venous thrombosis, and 3 cases including 2 compound heterozygotes and 1 single heterozygote all suffered from deep venous thrombosis (DVT) when they were younger without obvious triggers. The other 9 patients all combined with the other thrombotic factors including old age, hypertensive, smoking, pregnancy, and prolonged immobilization.Conclusion:Patients with AT deficiency caused by SERPINC1 gene defects are prone to venous thrombosis, especially combined with other thrombotic factors.
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Objective:To analyze the phenotype and genotype of two propositi with inherited hypodysfibrinogenaemia caused by compound heterozygous mutations, and investigate the molecular mechanism.Metheds:Two propositi and their family members(7 person in 3 generations and 10 person in 3 generations,respectively) were investigated. The activity of plasma fibrinogen (Fg:C) and thrombin time (TT) were analyzed by coagulation method, the antigen of plasma fibrinogen (Fg:Ag) was detected by immunoturbidimetry. All of the exons and flanking sequences of FGA,FGB,FGG of two propositi were amplified by PCR, followed by direct sequencing. The ClustalX-2, 1-win software was used to analyze the conservatism of mutated gene locus. PROVEAN and Mutation Taster were applied to analyze the pathogenicity of mutated amino acid. The changes of the protein spatial structure and intermolecular interaction were analyzed by Pymol.Results:Fg:C and Fg:Ag of proposita A and B were both significantly decreased (0.74 and 0.78 g/L, 0.96 and 0.94 g/L, respectively). Gene analysis revealed that proposita A and B both carried a heterozygous mutation c.2185G>A(p.AαGlu710Lys) in exon 6 of FGA. Furthermore, proposita A also carried a heterozygous mutation c.701G>T(p.γTrp208Leu) in exon 7 of FGG, and proposita B carried a heterozygous mutation c.1015A>C(p.γSer313Arg) in exon 8 of FGG. Phylogenetic analysis suggested that p.AαGlu710,p.γTrp208 and p.γSer313 were highly conserved among homologous species. All variants were predicted to be deleterious by two online bioinformatic softwares. The protein model analysis indicated that protein spatial structure and intermolecular hydrogen bonds were changed by these variants, which destroyed the stability of Fg.Conclusion:The compound heterozygous mutations of p.AαGlu710Lys and p.γTrp208Leu,p.AαGlu710Lys and p.γSer313Arg might account for the hypodysfibrinogenemia in two propositi.
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Objective:To investigate the molecular pathogenesis of a newly discovered gene mutation in a family with hereditary coagulation factor Ⅺ(FⅪ) deficiency.Methods:The proband was admitted to the First Affiliated Hospital of Wenzhou Medical University in September 2021 due to "calculus of intrahepatic duct". The patient had no symptoms of spontaneous bleeding.The clinical data and blood samples of the proband and her family members (10 persons in 3 generations) were collected.The activated partial thromboplastin time (APTT) and FⅪ activity (FⅪ:C) were performed by the one-stage clotting assay. FⅪ antigen (FⅪ:Ag) were detected by enzyme linked immunosorbent assay (ELISA). Genomic DNA extracted from peripheral blood cells of subjects was used as template to analyze F11 gene mutation by DNA direct sequencing. Bioinformatics software was used to analyze the effects of mutations on protein structure and function. Wild-type and mutant FⅪ protein expression vectors were constructed and transient transfected into HEK293T cells. The total RNA was extracted from positive transfected cells and then reversely transcribed into cDNA. The mRNA expression level of F11 gene in transfected cells was detected by real-time fluorescence quantitative PCR (qRT-PCR). The content of FⅪ:Ag and the expression of FⅪ protein in transfected cell lysates and culture supernatant were detected by ELISA and western blot.Results:The APTT of the proband was significantly prolonged to 107.9s (reference range 29.0-43.0s), while FⅪ:C and FⅪ:Ag were significantly decreased to 2% (reference range 84%-122%) and 5% (reference range 76%-127%), respectively. Gene sequencing analysis indicated that the proband had c.536C>T (p.Thr161Met) heterozygous missense mutation and c.1556G>A (p.Trp501Ter) heterozygous nonsense mutation in exon 6 and 13 of the F11 gene, respectively. Bioinformatics analysis showed that the amino acids at site 161 of FⅪ protein were threonine (Thr) in the matrix composed of five different species, indicating that Thr161 site was highly conserved among homologous genes in different species. p.Thr161Met heterozygous mutation affected the stability of local intermolecular structure of FⅪ protein. In vitro expression experiments of p.Thr161Met mutation showed that FⅪ protein had a normal synthesis in the cells but secretion dysfunction.Conclusions:c.536C>T (p.Thr161Met) heterozygous missense mutation and c.1556G>A (p.Trp501Ter) heterozygous nonsense mutation were mainly responsible for the decrease of FⅪ in this family. p.Thr161Met mutation was first reported in the world and did not affect the normal synthesis of FⅪ protein, but caused secretion dysfunction.