Comparative genomics of two Asian medicinal leeches Hirudo nipponia and Hirudo tianjinensis: With emphasis on antithrombotic genes and their corresponding proteins.

Leeches secrete various biologically active substances which have important medical and pharmaceutical values in antithrombotic treatments. Here, we provide a high quality genome of two Asian medicinal leeches Hirudo nipponia and Hirudo tianjinensis, based on which, we identified 22 antithrombotic gene families, including fourteen coagulation inhibitors, four platelet aggregation inhibitors, three fibrinolysis enhancers, and one tissue penetration enhancer. The total numbers of antithrombotic genes were similar between H. nipponia (N = 86) and H. tianjinensis (N = 83). Molecular evolution analysis showed that no significant differences were detected between the two species in any of the three selection indices (dN, dS, and dN/dS), nor in the number of sites under positive/purifying selection. RNA-Seq based gene expression analysis showed that the overall expression patterns of the antithrombotic gene families were not significantly deviated between the two species. Our results indicated that there were rather close similarities between the two leeches on genomic characteristics, especially for the molecular evolution and expression of antithrombotic genes. Our study provides the most comprehensive collection of antithrombotic biomacromolecules from the two Asian medicinal leeches to date. These results will greatly facilitate the research and application of leech derivatives for medical and pharmaceutical purposes of thrombosis.