Draft genome of the European medicinal leech Hirudo medicinalis (Annelida, Clitellata, Hirudiniformes) with emphasis on anticoagulants

Abstract

The European medicinal leech has been used for medicinal purposes for millennia, and continues to be used today in modern hospital settings. Its utility is granted by the extremely potent anticoagulation factors that the leech secretes into the incision wound during feeding and, although a handful of studies have targeted certain anticoagulants, the full range of anticoagulation factors expressed by this species remains unknown. Here, we present the first draft genome of the European medicinal leech, Hirudo medicinalis, and estimate that we have sequenced between 79-94% of the full genome. Leveraging these data, we searched for anticoagulation factors across the genome of H. medicinalis. Following orthology determination through a series of BLAST searches, as well as phylogenetic analyses, we estimate that fully 15 different known anticoagulation factors are utilized by the species, and that 17 other proteins that have been linked to antihemostasis are also present in the genome. We underscore the utility of the draft genome for comparative studies of leeches and discuss our results in an evolutionary context.

Figure 1

MAFFT-based amino acid alignments of putative anticoagulant orthologues derived from the genome of Hirudo medicinalis and the respective top BLASTp hits. (A) Putative destabilase I from H. medicinalis aligned with the known sequence of the salivary bioactive protein (GenBank accession number AAA96144); (B) putative Leech Derived Tryptase Inhibitor (LDTI) from H. medicinalis aligned with the known sequence of the salivary bioactive protein (GenBank accession number AAB33769); (C) putative hirudin (HV1) from H. medicinalis aligned with the known sequence of the salivary bioactive protein (GenBank accession number APA20833); (D) putative bdellin from H. medicinalis aligned with the known sequence of the salivary bioactive protein (GenBank accession number P09865). Red boxes denote conserved cysteine residues and blue shadings represent conservation of residues between the sequences.

Figure 2

Phylogenetic hypotheses resulting from maximum likelihood analyses of a set of putative orthologues for each anticoagulant or anticoagulant family. (A) Destabilase I (ln L = −3340.015305); (B) LDTI (ln L = −640.341632). Green shades indicate the smallest clan that includes both the newly derived sequence and the archetypal variant of the anticoagulant.

Figure 3

Phylogenetic hypotheses resulting from maximum likelihood analyses of a set of putative orthologues for each anticoagulant or anticoagulant family. (A) Hirudin (ln L = −4750.252905); (B) bdellin (ln L = −1771.698797). Green shades indicate the smallest clan that includes both the newly derived sequence and the archetypal variant of the anticoagulant.