Fig. 1

Variant in the FGG gene of the hypofibrinogenemia family and its effects on the protein structure and fiber. A Filled symbols represent affected individuals, while empty symbols represent unaffected individuals. The proband (III:1) is indicated by an arrow. B Sanger sequencing of affected and unaffected individuals. All patients carried the heterozygous mutation (c.668G > C, p.Arg223Thr) in the FGG gene. C Amino acid sequence alignment of FGG protein revealed that the p.Arg223 is highly conserved across different species. D Predicted protein domains of wild-type FGG. The fibrinogen coiled coil domain is depicted in wheat, while the fibrinogen C-terminal domain is depicted in sky blue. The p.Arg223 residue locates in the fibrinogen C-terminal domain. E The predicted protein structure of wild-type FGG, with the coiled-coil domain shown in wheat and the C-terminal domain shown in sky blue. F Hydrogen bonds are represented by yellow dotted lines. The p.Arg223 residue is displayed in blue, with residues forming hydrogen bonds shown in orange. The p.Thr223 residue is displayed in red, with residue forming hydrogen bonds shown in magenta