Cloning and Comparison of Factor X from Rhesus Monkey (Macaca mulatta)

The reliability of the rhesus monkey as an important experimental animal depends on its genetic concordance with human. During our assessment of the rhesus monkey as a preclinical model for coagulation-related research, we cloned the full-length cDNA of rhesus monkey factor X (FX) and compared its genetic characteristics and coagulation activity with those of human FX. The full-length cDNA of rhesus monkey FX was 1683 bp in length, corresponding to 487 coding amino acids and sharing 94.71% nucleotide identity and 93.65% amino acid identity with human FX. When FX sequences from different animals were compared with that of human FX, rhesus monkey and baboon FX showed similar degrees of homology to human FX, which were less than that between human and chimpanzee FX sequences but remarkably higher than those of another 2 monkey species, bovine, pig, and rodents. Comparison of functional sites between human and rhesus monkey FX revealed high similarities between their amino acids sequences and 3-dimensional structures. The average coagulation activity of FX from 24 rhesus monkeys was in the normal range of that of healthy humans. The rhesus monkey therefore may be a suitable animal model for research addressing coagulation factor X.Abbreviations: 3D, 3-dimensional; FX, factor X; SMART, simple modular architecture research tool; TFPI, tissue factor pathway inhibitorRhesus monkeys (Macaca mulatta) continue to be widely used research animals in many biologic fields.¹⁵ Because of their close genetic relationship to humans, there is increasing interest in the use of rhesus monkeys for gene therapy, stem cell, infectious disease researches, and reproductive biology.¹² The effective application of rhesus monkey as an important experimental animal is dependent on the genomic and proteomic concordance between rhesus and human.¹⁷ The coagulation system plays an essential role in many physiologic and pathologic processes, including hematologic, cardiovascular, and liver diseases and transplantation. Clearly, the establishment of genetic information and reference activity values of rhesus monkey coagulation factors is requisite to interpretation of the data from preclinical coagulation-related research using rhesus monkeys. Factor X (FX) is a vitamin-K–dependent protein that is 1 of the most critical factors in the coagulation scheme; its activation is the convergence of the extrinsic and intrinsic activation pathways and leads to the final stages of hemostasis.⁶ Human FX has been investigated extensively during the past century, but there have been few reports regarding the characterization of monkey FX.¹⁴The ineffective binding of porcine tissue factor pathway inhibitor (TFPI) to human FX was proposed to be an important contributor to coagulopathy in pig-to-human xenotransplantation.¹¹ Many in vitro studies¹¹ have investigated the interaction between porcine endothelial cells and human coagulation factors, whereas in vivo studies⁸ have addressed the interaction between porcine endothelial cells and monkey coagulation factors. The concordance of the results from these in vitro and in vivo studies therefore reflects high homology, if not identity, between human FX and monkey FX. During our assessment of whether rhesus monkey is a reliable model for studying coagulation disorders in xenotransplantation, we cloned the full-length cDNA of rhesus monkey FX and compared its nucleotide and amino-acid sequences and coagulation activities with those of human FX.