Abstract
This study aims to preliminarily investigate the clinical characterization and molecular pathogenic basis of hereditary protein C (PC) deficiency in two independent Chinese families. The PC activity (PC:A) was tested using the chromogenic substrate, and PC antigen (PC:Ag) was detected via enzyme-linked immunosorbent assay (ELISA). To identify the mutation sites, nine exons of the PROCgene were amplified by PCR, and the products were directly sequenced. The conservation and pathogenicity of the mutations, as well as changes in the spatial structure of PC proteins before and after mutations, were analyzed using ClustalX-2.1-win, online bioinformatics software, and PyMOL., The function of the mutant proteins was detected using the calibrated automated thrombogram (CAT). Proband A and B, aged 39 and 63 respectively, are both diagnosed with deep vein thrombosis (DVT) in both lower limbs and pulmonary embolism (PE). Two missense mutations, p.Arg440Cys and p.Trp444Arg, were identified in the probands. Bioinformatics and protein modeling analyses revealed that the two mutations probably affected the normal function of PC. The thrombin generation assay revealed impaired thrombin generation capacity in both probands, with proband B showing more severe impairment. These two mutations may be the causes of reduced PC in two independent Chinese families. Notably, this is the first reported instance of the p.Trp444Arg mutation.