OBJECTIVE: To investigate the molecular mechanism for a family with Hereditary coagulation factor Ⅻ (FⅫ) deficiency. METHODS: The proband, a 63-year-old female, was admitted to the First Affiliated Hospital of Wenzhou Medical University in August 2024 for lumbar disc herniation. Coagulation tests, including prothrombin time (PT), activated partial thromboplastin time (APTT), and FⅫ activity (FⅫ:C), were carried out for the proband and her family members (9 individuals from three generations) using a one-stage clotting assay. The level of FⅫ antigen (FⅫ:Ag) was determined with an Enzyme-linked immunosorbent assay (ELISA). Sanger sequencing was conducted to identify potential variants in the F12 gene. Multiple in silico tools were used to predict the conservation, hydrophobicity, and structural impact of the identified variants. Recombinant expression plasmids were constructed and transiently transfected into HEK293T cells. The recombinant FⅫ protein was analyzed using Western blotting (WB) and ELISA. This study was approved by the Ethics Committee of the First Affiliated Hospital of Wenzhou Medical University (Ethics No.: KY2022-R193). RESULTS: The proband showed a markedly prolonged APTT (160.3 s) and significantly decreased FⅫ:C (2%) and FⅫ:Ag (5%) levels. Analysis of the F12 gene sequence revealed a 46C/T genotype in the promoter region, a heterozygous c.1457G>A (p.Cys467Tyr) missense variant in exon 12, and a heterozygous c.1561G>A (p.Glu502Lys) missense variant in exon 13. Bioinformatic analysis showed that the p.Cys467 is highly conserved across various species, and the p.Cys467Tyr variant may affect local structural stability of the FⅫ protein. The p.Cys467Tyr variant had no effect on the transcription of the F12 gene. However, the variant has significantly decreased the FⅫ:Ag levels and FⅫ protein expression in the cell culture supernatant compared to the wild-type expression vector, while in the cell lysate, it is higher than the wild-type expression vector. In other words, the p.Cys467Tyr variant has probably caused a secretion defect of FⅫ protein. CONCLUSION The 46C/T genotype, the heterozygous p.Cys467Tyr missense variant, and the heterozygous p.Glu502Lys missense variant are associated with reduced plasma FⅫ levels in this pedigree. The p.Cys467Tyr variant, which was unreported previously, did not affect the synthesis of FⅫ but may have resulted in a secretion defect.
Humans ; Female ; Middle Aged ; Mutation, Missense ; Pedigree ; HEK293 Cells ; Male ; Factor XII/genetics* ; Adult ; Factor XII Deficiency/genetics*

Objective:Molecular mechanisms underlying compound heterozygous mutations in a patient with inherited antithrombin (AT) deficiency.Methods:The proband was admitted to the First Affiliated Hospital of Wenzhou Medical University in November 2018 with a one-day history of sudden syncope and limb twitching. Peripheral venous blood was collected from the proband and members of his lineages, totaling nine persons across three generations, and a family lineage survey was conducted. AT activity (AT:A) was measured using a chromogenic substrate assay, while AT antigen (AT:Ag) was detected through an immunoturbidimetric assay. Mutation sites were identified by means of Sanger sequencing of the SERPINC1 gene, and silico tools were applied to predict the mutational conservation and hydrophobicity changes. Recombinant plasmid expression vectors were constructed and transfected into HEK293T cells for in vitro overexpression studies. The recombinant AT protein was characterized using Western Blotting, ELISA, and cellular immunofluorescence assays.Results:The proband was a 21-year-old man with type Ⅰ AT deficiency. His AT:A was 33%, along with a corresponding reduction in AT:Ag. The genetic analysis revealed there was a heterozygous insertion mutation at c.318_319insT (p.Asn107*) and a heterozygous missense mutation at c.922G>T (p.Gly308Cys) in exons 2 and 5, respectively. These mutation sites were entirely conserved among the homologous species. Additionally, hydrophobicity studies showed that the p.Gly308Cys mutation will decrease the hydrophilicity of amino acid residues 307-313. The in vitro expression studies indicated a reduction of approximately 46.98%±2.94% and 41.35%±1.48% in the amount of recombinant protein AT-G308C in transfected cell lysates and culture supernatants, respectively. Treatment with the proteasome inhibitor (MG132) restored the cytoplasmic levels of AT-G308C protein to a level similar to that of wild-type protein. However, neither cell lysate nor culture supernatant demonstrated the presence of the recombinant protein AT-N107*. Conclusions:The heterozygous insertion mutation of p.Asn107* and the heterozygous missense mutation of p.Gly308Cys have been associated with reduced AT levels in proband. The p.Asn107* heterozygous insertion mutation may initiate the degradation of mRNA via nonsense mutation-mediated mechanisms, which would remove the defective transcripts, as well as the p.The Gly308Cys heterozygous missense mutation may cause the AT protein to undergo proteasome-dependent degradation by modifying the hydrophobicity of nearby residues in the cytoplasm.

A 34 year old female patient was scheduled to undergo surgical resection due to a "breast nodule". Preoperative examination revealed an activated partial thromboplastin time (APTT) of 66.2 seconds, coagulation factor Ⅺ activity (FⅪ: C) of 2%, and FⅪ antigen (FⅪ: Ag) of 40.3%. The patient and family members showed no abnormal bleeding symptoms. Diagnosed as hereditary coagulation factor Ⅺ deficiency. Genetic testing revealed that the F11 gene had a heterozygous nonsense mutation in exon 10, c.1107C>A (p.Tyr351stop), and a heterozygous missense mutation in exon 13, c.1562A>G (p.Tyr503Cys). The father and son were p Heterozygous carriers of Tyr351stop mutation, while the mother and daughter are p Heterozygous carriers of Tyr503Cys mutations. The in vitro expression results showed that p The Tyr351stop mutation resulted in a significant decrease in the transcription level of F11 gene, while p The Tyr503Cys mutation has no effect on the transcription level and protein expression level of F11 gene, but it leads to a significant decrease in the level of FⅪ:C in the cell culture supernatant.