It is well known that mRNAs with PTCs are quickly destroyed by the nonsense-mediated mRNA decay (NMD) pathway, which prevents the expression

of truncated proteins [7]. We identified a heterozygous mutation (Asp409del) located in the catalytic domain of FX in the proband. Both coagulation assay and in vitro expression analysis indicated that the mutation was associated with the CRM+ phenotype. The phenotypic features of CRM+ FX deficiency can be heterogeneous. Although in the majority of patients there are defects in both the intrinsic and extrinsic systems, defects only or predominantly in the intrinsic and LDK378 extrinsic pathway have been reported in several studies [8, 9]. The Asp409del mutation described here has defects in both the intrinsic and extrinsic systems. In addition, the amidolytic activity level based on RVV assays was decreased significantly, indicating that enzymatic activity of the mutant was lost. Previous investigations

have revealed that metal ion-binding sites in FXa are not only energetically but also allosterically XL765 mouse linked [10, 11]. Na+ can allosterically modulate the activity and specificity of FXa by binding to four key residues (Arg222, Lys224, Try185, and Asp185a) in loops 221–225 and 185–189. The crystal structure of FXa suggests that the Na+-binding loop, the catalytic pocket of the enzyme, and the FVa-binding helix (residues 163–170) are quite near one another in space and interact with each other to bind or cleave the substrate. In this study, structural molecular modelling showed that the Asp409del mutant could markedly alter the conformation of the 185–189 loop and impair binding of the loop to Na+, leading to a loss of FXa enzymatic activity. In summary, we report here two novel causative mutations (IVS5+1G>A and Asp409del) in the F10 gene, which result in severe FX deficiency. The splice-site IVS5+1G>A variant causes an absence of the abnormal transcript allele due to the NMD pathway. The Asp409del mutation leads to a loss of FXa function rather than the impairment of

mutant FX expression. This report may therefore provide insight into the underlying pathogenesis of inherited FX deficiency. We deeply appreciate Dr. Cheng Luo and Dr. Keqin Kathy Li for their help in the modelling analysis of mutant FXa. The selleck inhibitor authors stated that they had no interests which might be perceived as posing a conflict or bias. “
“Summary.  With the introduction of safe and effective factor VIII/IX-bypassing agents – recombinant activated factor VII (rFVIIa) and plasma-derived activated prothrombin complex concentrates (pd-APCC) – elective orthopaedic surgery (EOS) is a viable option for haemophilia patients with inhibitors. We report a series of patients with haemophilia and inhibitors undergoing EOS between 1997 and 2008 using bypassing agents to provide haemostatic cover.