Gene Variants in Two Families with Inherited Coagulation Factor XI Deficiency and Identification of Mutations

Mutations in the F11 gene can cause factor XI (FXI) deficiency, leading to abnormal coagulation activity and injury-related bleeding tendency. Therefore, identifying F11 gene mutations and studying the molecular basis will help us understand the pathogenesis of FXI deficiency.Coagulation tests and gene sequencing analysis of all members were performed. FXI wild-type and mutant expression plasmids were constructed and transfected into HEK293FT cells. The FXI protein expression level was evaluated by ELISA and Western blot.The FXI activity (FXI:C) and FXI antigen (FXI:Ag) of proband-1 were decreased to 2% and 5%, respectively. FXI:C and FXI:Ag of proband-2 were reduced to 15% and 32%, respectively. Four mutations were found in the two unrelated families, including c.536C>T (p.T179M), c.1556G>A (p.W519*), c.434A>G (p.H145R), and c.1325_1325delT (p.L442Cfs*8). In vitro studies in transiently transfected HEK293FT cells demonstrated that p.T179M, p.W519*, and p.L442Cfs*8 mutations significantly lowered the FXI levels in the culture media. The FXI levels in the culture media and cell lysates of p.H145R mutation were similar to the wild type.Our results confirm that the four mutations in the F11 gene are causative in the 2 FXI deficiency families. Moreover, the p.H145R mutation is a cross-reactive material (CRM)-positive phenotype. The other three mutations are CRM-negative phenotypes and lead to FXI protein secretion disorder.