Compound heterozygous mutations (p.L68R∗37 and p.T241N) lead to abnormal protein levels and structures in hereditary FVII deficiency

Abstract

Background: Congenital factor VII (FVII) deficiency is a genetic disorder characterized by decreased FVII activity, which sometimes leads to fatal bleeding. Numerous variants have been found in FVII deficiency, but mutations vary among patients. Each mutation deserves further exploration for each patient at risk of bleeding. We previously reported a Chinese patient with p.L68R∗37 and p.T241N compound heterozygous mutations. In this study, we further investigated the impact of these two mutations on the FVII expression through in vitro expression experiments.

Methods: Mutations were introduced into the FVII coding region using site-directed mutagenesis, and recombinant FVII was combined with two different plasmids, and then quantitative PCR and western blot analyses were performed subsequently.

Results: The p.L68R∗37 mutation had no effect on mRNA levels but caused a significant decrease in protein levels. In the p.T241N mutant vector, mRNA levels did not show a noticeable decrease, but protein levels exhibited a slight decrease. Structural analysis revealed that the p.T241N mutation resulted in an altered secondary structure and protein instability, indicating impaired functional properties.

Conclusion: Our study demonstrated that the p.L68R∗37 and p.T241N mutations impacted the protein levels and function of FVII, ultimately leading to a severe reduction in FVII activity. This study may contribute to further understanding of the molecular pathogenesis of FVII deficiency and offer insights for genetic counseling.

Fig. 1

Sequencing of recombinant FVII vectors. p.L68R∗37 and p.T241N mutations were successfully constructed in vectors.

Fig. 2

Relative mRNA levels of recombinant FVII. Wild-type FVII and mutant FVIIs were constructed, and relative mRNA levels from the p3×Flag-CMV-7.1 plasmid (a) and the pcDNA3.1-Flag-EFla-copGFP plasmid (b) were analyzed. P > 0.05.

Fig. 3

Western blot analysis of recombinant FVII proteins. Wild-type FVII and mutant FVIIs were constructed, and proteins from the p3×Flag-CMV-7.1 plasmid (a) and the pcDNA3.1-Flag-EFla-copGFP plasmid (b) were analyzed. Lane 1: wild-type FVII; lane 2: p.L68R∗37 FVII; lane 3: p.T241N.

Fig. 4

Structure analysis of recombinant FVII proteins. (a) The structure of the p.T241N protein. (b) The hydrogen bind distance between T241 and V249 for the wild type (left) and the p.T241N protein (right). The hydrogen bond distance did not change after the mutation.