[Analysis of hereditary coagulation factor Ⅺ deficiency in a Chinese pedigree with compound heterozygous mutations]

To explore the molecular mechanisms of a Chinese pedigree with hereditary factor Ⅺ (FⅪ) deficiency.

All of the 15 exons, flanking sequences of the FⅪ gene and the corresponding mutation sites of family members were analyzed by the Sanger sequencing, followed by the extraction of the peripheral blood genomic DNA. And all the results were verified by the reverse sequencing. The conservation of the mutated sites was analyzed by the ClustalX-2.1-win. Three online bioinformatics software tools, including Mutation Taster, PolyPhen2 and the PROVEAN, were used to assess the possible impact of the mutations. Swiss-pdbviewer software was used to analyze the effects of mutant amino acids on protein structure.

Genetic analysis revealed that the proband had compound heterozygous mutations including a nonsense mutation of c.1107C>A (Tyr369stop) in exon 10 and missense mutation of c.1562A>G (Tyr521Cys) in exon 13. The same c.1107C>A (Tyr369stop) was present in her father, the same c.1562A>G (Tyr521Cys) was present in both her mother and daughter. Conservation analysis indicated that Tyr521 was a highly conserved site during evolution. The prediction of pathogenicity showed that both c.1107C>A and c.1562A>G were pathogenic mutations. Protein structure prediction showed that in the wild type FⅪ protein structure, Tyr521 formed a hydrogen bond with the Lys572 and Ile388, respectively. When Tyr521 was replaced by Cys521, the original benzene ring structure disappeared, and side chains of Lys572 added a hydrogen bond with the Cys521, which may change protein catalytic domain structure. When Tyr369 was mutated to a stop codon, resulting in the truncated protein.

The compound heterozygous mutations including the c.1107C>A heterozygous missense variant in exon 10 and the c.1562A>G heterozygous nonsense mutation in exon 13 may be responsible for the hereditary factor Ⅺ deficiency in this Chinese pedigree.