LI Shaoxi,LI Xiaolong,JIN Yanhui, et al. Genetic analysis of the pedigree with inherited coagulation factorXII deficiency caused by compound heterozygous mutations[J]. JOURNAL OF WEZHOU MEDICAL UNIVERSITY, 2020, 50(2): 130-134.
Abstract：Objective: To detect the laboratory phenotype and genotype of a hereditary factorXII (FXII) deficient pedigree caused by compound heterozygous mutations, which will help us to investigate the causative gene and its molecular pathogenesis. Methods: Prothrombin time (PT), activated partial thromboplastin time (APTT), coagulation factor VIII activity (FVIII:C), coagulation factor IX activity (FIX:C), coagulation factor XI activity (FXI:C), FXII activity (FXII:C), and FXII antigen (FXII:Ag) were assayed in proband and his family members (five persons in three generations) to confirm the diagnosis. All exons and flanking sequences of the F12 gene of the proband were analyzed by direct PCR sequencing. The mutation sites were confirmed by reverse sequencing and the corresponding mutation site regions of the family members were detected. The conservation of amino acid mutation sites were analyzed using ClustalX-2.1-win software, the effect of mutations on protein functions were analyzed using four online bioinformatic tools (Mutation Taster, Poly-Phen-2, PROVEAN and SIFT); the mutation sites were analyzed by Swiss-Pdb Viewer 4.0.1 for molecular structure and protein interaction. Results: The APTT of the proband is 59.1 s, prolonged obviously, and the FXII:C decreased to 4%, the FXII:Ag decreased to 5%; the FXII:C and the FXII:Ag of his father, mother and daughter decreased to 32%-37%. Genetic analysis revealed that there were two compound heterozygous mutations in exon 13 of the F12 gene in the proband: one was the c.1561G>A point heterozygous missense mutation (p.Glu502Lys); another was the c.1637T>C point heterozygous missene mutation (p.Met527Thr). His father was carried the p.Met527Thr mutation, his mother and daughter were carried the p.Glu502Lys mutation. Conservative analysis showed that Glu502 and Met527 were highly conserved among homologous species. The four online bioinformatics sofwares predicted results for these mutations were consistent: all predicted that these mutations were likely to be deleterious mutations that could cause related diseases. Mutant protein model analysis showed that wild-type Glu502 forms a hydrogen bond with His365, the mutant Lys502 resulted in the disappearance of the hydrogen bond between Lys502-His365. Replacement of Met527 with Thr527 resulted in the addition of two hydrogen bonds between Thr527-Leu527. Conclusion: There were two compound heterozygous mutations p.Glu502Lys and p.Met527Thr in exon 13 of the F12 gene in the proband, which were speculated that the heterozygous mutations were inherited from his parents with the heterozygotes of p.Glu502Lys and p.Met527Thr respectively and were associated with the reduced blood FXII levels in the family.
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