[Molecular Pathogenic Mechanism Study of Two Cases of Inherited Dysfibrinogenemia]

To analyze two families with inherited dysfibrinogenemia, and explore the molecular pathogenic mechanisms.

The coagulation indexes of the probands and their family members were detected. The FGA, FGB, and FGG exons and their flanking sequences were amplified by PCR, and the mutation sites were identified by sequencing. SIFT, PolyPhen2, LRT, ReVe, MutationTaster, phyloP, and phastCons bioinformatics software were used to predict the functional impact of the mutation sites. Protein structure and amino acid conservation analysis of the variant were conducted using PyMOL and Clustal X software.

The thrombin time (TT) of the proband in family 1 was prolonged to 37.00 s, and Fg∶C decreased to 0.52 g/L. The TT of the proband in family 2 was 20.30 s, and Fg∶C was 1.00 g/L, which was lower than the normal range. Genetic analysis revealed that the proband in family 1 had a heterozygous mutation c.80T>C in FGA, resulting in the substitution of phenylalanine 27 with serine (Phe27Ser). The proband in family 2 had a heterozygous mutation c.1007T>A in FGG, resulting in the substitution of methionine 336 with lysine (Met336Lys). Bioinformatics software prediction analysis indicated that both mutations were deleterious variants. PyMOL mutation models revealed that the Aα chain mutation (Phe27Ser) in family 1 and γ chain mutation (Met336Lys) in family 2 resulted in alterations in spatial structure and reduced protein stability. Clustal X results showed that both Aα Phe27 and γMet336 were highly conserved across homologous species.

Heterozygous mutations of FGA gene c.80T>C and FGG gene c.1007T>A are both pathogenic variants, causing inherited dysfibrinogenemia.