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Bloodsucking leeches
There are over 650 different types of leeches. And most want to suck your blood! These real-life vampires are nocturnal, like dark places, and only come out when they get thirsty! But can these bloodsuckers actually help humans? The ancient Egyptians may have been on to something! Readers learn about the habitats, history, and medical uses of the bloodsucking leech.
Book
Draft genome sequences of Hirudo medicinalis and salivary transcriptome of three closely related medicinal leeches
Background
Salivary cell secretion (SCS) plays a critical role in blood feeding by medicinal leeches, making them of use for certain medical purposes even today.
Results
We annotated the
Hirudo medicinalis
genome and performed RNA-seq on salivary cells isolated from three closely related leech species,
H. medicinalis, Hirudo orientalis
, and
Hirudo verbana
. Differential expression analysis verified by proteomics identified salivary cell-specific gene expression, many of which encode previously unknown salivary components. However, the genes encoding known anticoagulants have been found to be expressed not only in salivary cells. The function-related analysis of the unique salivary cell genes enabled an update of the concept of interactions between salivary proteins and components of haemostasis.
Conclusions
Here we report a genome draft of
Hirudo medicinalis
and describe identification of novel salivary proteins and new homologs of genes encoding known anticoagulants in transcriptomes of three medicinal leech species. Our data provide new insights in genetics of blood-feeding lifestyle in leeches.
Journal Article
Leech
A horror and a healer, the leech has reared its head in many unexpected places and practices, revealing this creature to be among humanity's most enduring and peculiar companions. The Leech is one of nature's most tenacious yet mysterious animals. This book explores how this creature repeatedly surfaces throughout human history.
Book
The great diversity: monomeric and oligomeric hirudins, hirudin-like factors and decorsins in the Asian medicinal leeches Hirudo nipponia and Hirudo tianjinensis
Medicinal leeches express a broad variety of anticoagulants and other bioactive factors that are involved in the blood feeding process. For most of the anticoagulants, several genes exist that may encode isoforms of the respective proteins, including hirudins and decorsins. Decorsins negatively affect platelet aggregation, whereas hirudins are potent thrombin inhibitors. Both factors belong to the hirudin superfamily that also includes the group of hirudin-like factors, and all hematophagous leeches analyzed so far contain several gene copies that encode representatives of at least two of the three groups of these factors. Members of the hirudin superfamily may contain only one central globular domain, but others may contain two or more copies. Here we describe the molecular identification and partial functional characterization of a broad variety of putative mono-, bi and multimeric hirudins, decorsins and hirudin-like factors in two Asian medicinal leech species, namely
Hirudo nipponia
and
H. tianjinensis
. Some of the monomeric hirudins and decorsins have already been described before, but they represent only a small part of the overall diversity. For the first time, putative monomeric and one oligomeric decorsins of
H. tianjinensis
were expressed as recombinant proteins, functionally characterized and successfully verified as platelet aggregation inhibitors. In addition we have conducted phylogenetic analyses based on genomic and mitochondrial markers and found convincing evidence that
H. nipponia
and
H. tianjinensis
together with members of the genus
Whitmania
form a monophyletic clade that is clearly distinct from clades that are formed either by European members of the genus
Hirudo
or by members of the genus
Hirudinaria
.
Journal Article
Research on ACEI of Low-Molecular-Weight Peptides from IHirudo nipponia/I Whitman
The renin-angiotensin system (RAS) is the primary pathway for regulating blood pressure in the body, and angiotensin-converting enzymes (ACEs) play a crucial role in it. Hirudo nipponia is an invertebrate that contains a variety of active peptides; however, there are no studies on the ACE inhibitory activity of hirudo. In the present study, our aim was to identify the active peptides in hirudo based on active peptide database analysis, unexpectedly filling the gap in hirudo ACE inhibitory activity research. Prep-HPLC was used to separate the part below 3 kD from hirudo. The peptide composition of the isolates was obtained based on Orbitrap LC-MS. The activity of each group of peptides was predicted by the database and the activity was determined by bioassay. Peptides with validation activity were screened through the database. In total, 337 peptides and 18 peptides matching the NCBI leech protein database were identified. All four fractions showed ACE inhibitory activity, and the IC50 was 0.8266, 0.2708, 0.4432, and 0.1764 mg/mL, respectively. Six screened peptides showed good affinity for ACE. This work reveals for the first time that low-molecular-weight peptides from H. nipponia have ACE inhibitory activity, which can provide a new explanation for leech treatment of hypertension.
Journal Article
Analysis of codon usage patterns in Hirudinaria manillensis reveals a preference for GC-ending codons caused by dominant selection constraints
Background
Hirudinaria manillensis
is an ephemeral, blood-sucking ectoparasite, possessing anticoagulant capacities with potential medical applications. Analysis of codon usage patterns would contribute to our understanding of the evolutionary mechanisms and genetic architecture of
H. manillensis
, which in turn would provide insight into the characteristics of other leeches. We analysed codon usage and related indices using 18,000 coding sequences (CDSs) retrieved from
H. manillensis
RNA-Seq data.
Results
We identified four highly preferred codons in
H. manillensis
that have G/C-endings. Points generated in an effective number of codons (ENC) plot distributed below the standard curve and the slope of a neutrality plot was less than 1. Highly expressed CDSs had lower ENC content and higher GC content than weakly expressed CDSs. Principal component analysis conducted on relative synonymous codon usage (RSCU) values divided CDSs according to GC content and divided codons according to ending bases. Moreover, by determining codon usage, we found that the majority of blood-diet related genes have undergone less adaptive evolution in
H. manillensis
, except for those with homologous sequences in the host species.
Conclusions
Codon usage in
H. manillensis
had an overall preference toward C-endings and indicated that codon usage patterns are mediated by differential expression, GC content, and biological function. Although mutation pressure effects were also notable, the majority of genetic evolution in
H. manillensis
was driven by natural selection.
Journal Article
Comparative genomics suggests extensive antithrombotic gene expansion in Haemadipsa yanyuanensis
Haemadipsa yanyuanensis
Liu & Song, 1977, is a terrestrial blood-feeding leech whose antithrombotic repertoire remains insufficiently characterized. We present its first chromosome-level genome assembly (165.32 Mb across nine chromosomes; BUSCO: 97.6%) using Nanopore long reads, Hi-C scaffolding, and RNA-seq data. We identified 193 putative antithrombotic genes in 15 putative families, representing a 2.2- to 2.7-fold increase in gene number but reduced family diversity compared with aquatic medicinal leeches, including
Hirudo nipponia
Whitman, 1886,
Hirudinaria manillensis
Lesson, 1842, and
Hirudo medicinalis
Linnaeus, 1758. Notably, the putative bdellin, LDTI, and LCI gene families exhibited marked lineage-specific expansions, ranging from 8.7- to 25-fold relative to those of aquatic leeches. In addition, the putative progranulin gene displayed a distinctive structural organization characterized by 122 cysteine residues and nine tandem repeats. Transcriptomic profiling revealed elevated expression of four expanded putative families, suggesting potential roles in terrestrial blood-feeding adaptation. This chromosome-scale genome provides a valuable resource for investigating anticoagulation mechanisms and may inform the development of next-generation antithrombotic therapeutics.
Journal Article
Hirudins and fenestrins of the African medicinal leech Asiaticobdella fenestrata
African hematophagous leeches are largely underinvestigated both in terms of their biodiversity and the characterization of the repertoire of bioactive components of their salivary gland secretions.
Asiaticobdella
(formerly
Aliolimnatis
)
fenestrata
Moore, 1939, also referred to as the African medicinal leech, is hence a promising candidate for the identification and functional characterization of putative anticoagulants that may serve as inspirations for the development of new or the enhancement of existing drugs for medical purposes.
A. fenestrata
inhabits flooded plains of southern African regions and mainly feeds on mammals like black lechwe (
Kobus leche
Gray, 1850). Whereas several anticoagulants, including two putative hirudins of
A. fenestrata
, have already been identified in previous investigations, functional characterizations of these components are yet missing. We conducted an in-depth re-analysis of the salivary gland transcriptomic data set of
A. fenestrata
and identified two additional hirudin-like factors that exhibit a remarkable structural feature—the presence of an RGD motif at or near the N-terminal end of the molecules. The presence of such an RGD motif is a key feature of leech-derived platelet aggregation inhibitors such as ornatins and decorsins. However, both in ornatins and in decorsins, the respective RGD motif is located within the molecule between the 5th and the 6th cysteine residues, but not at or near the N-terminus. We named the two putative platelet aggregation inhibitors “fenestrins.” Both the two putative hirudins and the two fenestrins of
A. fenestrata
were expressed as recombinant proteins, purified, and functionally characterized in either coagulation or platelet aggregation assays.
Journal Article
Diversity of hirudin and hirudin-like factor genes in the North-African medicinal leech, Hirudo troctina
Medicinal leeches of the genus
Hirudo
inhabit large areas of the Palaearctic realm. The distribution range of
Hirudo troctina
includes the southern Iberian peninsula and the northwestern regions of Africa.
H. troctina
is used for medical purposes, but only very little is known about the components of its salivary gland secretion. Hirudins, bivalent inhibitors of thrombin, are probably the best known leech-derived bioactive factors. Hirudin-like factors (HLFs) represent another class of salivary gland components that share characteristic genetic and structural markers with hirudins. Hirudin is not a single entity but exists in at least four different variants. However, there are differences among the European members of the genus
Hirudo
with respect to the actual number of hirudin and HLF genes that are present within their genomes. Here, we describe the identification and molecular cloning of 11 genes that encode for putative hirudin and HLF variants in
H. troctina
. Three of the genes consist of exons and introns that originate from different “archetype” genes and are likely the result of recombination events. The diversity of hirudin and HLF genes in
H. troctina
surpasses that of all other European members of the genus
Hirudo
. The putative hirudin variants and representatives of the HLFs of
H. troctina
were expressed as recombinant proteins, purified and functionally characterized for their thrombin-inhibiting potencies. Phylogenetic analyses based on hirudin and HLF gene sequences of the leech genera
Hirudo
,
Hirudinaria
, and
Whitmania
supported the hypothesis that hirudins and HLFs diverged early in leech evolution.
Journal Article
Unoculubranchiobdella sp. (Hirudinea: Ozobranchidae) as a vector for Haemogregarina spp. in freshwater turtles from Brazil
Species of
Haemogregarina
are blood parasites known to parasitise vertebrate hosts, including fishes (
Haemogregarina
sensu lato) and freshwater turtles (
Haemogregarina
sensu stricto). Their vectors, include gnathiid isopods and leeches, respectively. In turtles,
Haemogregarina balli
has the best-characterized life cycle in the genus. However, no studies in Brazil have suggested a possible vector for any species of
Haemogregarina
from freshwater turtles. Therefore, in the present study, we provide insights into a leech vector based on specimens found feeding on two species of freshwater turtles,
Podocnemis unifilis
and
Podocnemis expansa
, using morphological and molecular data
.
In 2017 and 2019, freshwater turtles were collected in Goiás State, Brazil. Hosts were inspected for ectoparasites and leeches were collected from two specimens of
P. expansa
and nine specimens of
P. unifilis
. Leeches were subsequently identified as members of the genus
Unoculubranchiobdella.
Leech histological slides revealed haemogregarine-like structures, similar to post-sporogonic merogony, found near the gills and within the posterior sucker. Molecular analysis of the haemeogregarines resulted in the identification of three species of
Haemogregarina
:
Haemogregarina embaubali, Haemogregarina goianensis,
and
Haemogregarina brasiliana
. Therefore, our findings, based on morphology and DNA data suggest leeches of the genus
Unoculubranchiondella
as vectors for at least three species of
Haemogregarina
from Brazilian turtles.
Journal Article