Intermediate filament genes as differentiation markers in the leech Helobdella

Unveiling salivary gland-specific gene expression of Piezo1 and Neuroendocrine in the leech, Helobdella austinensis

Mechanotransduction is a critical biological phenomenon in living organisms, with Piezo1 being one of the key mechanotransduction ion channel genes. Piezo1 is widely expressed across various tissues and organs, playing critical roles in numerous biological processes, including innate and adaptive immune activation. While most studies on Neuroendocrine and Piezo functions have focused on vertebrates and higher invertebrates (e.g., Drosophila), however research in lophotrochozoan animal models remains scarce. To address this gap, we utilized Helobdella austinensis (phylum: Annelida) to investigate the putative function of Piezo1 and uncovered evidence related to the neuroendocrine system through spatiotemporal characterization. Our findings represent the developmental contribution of Piezo1 from early to late embryonic stages by demonstrating its expression in a lophotrochozoan. Intriguingly, the expression of Hau-Piezo1 was specifically detected in salivary gland-related precursors and tissues during development. Additionally, Neuroendocrine expression was observed in a lophotrochozoan, suggesting the correlation between neuronal stimulation and immune cells along the salivary glands of leeches. Furthermore, the downregulation of Hau-Piezo1 following bacterial challenge suggests that Piezo1 plays a role in regulating inflammatory responses. Taken together, we characterized the spatiotemporal expression pattern of Hau-Piezo1 in leeches and demonstrated its conserved and diversified functions based on its phylogenetic relationship with other homologs. These results suggest that Piezo1 may serve as a salivary gland marker in leeches and provide evidence for the presence of immune cells along the salivary glands in lophotrochozoans.

Immunomodulatory effects of medicinal leech saliva extract on in vitro activated macrophages

Leech therapy has been utilized in modern and traditional medicine. Leech saliva contains versatile peptides and molecules that can exert anti-microbial, anti-inflammatory, anti-coagulant, and analgesic activities on the patients. The active components and molecular mechanism of action of these components should be deciphered properly in order to generate biotechnological drug candidates by recombinant production of the leech saliva peptides. In our study, we conducted LC-MS/MS and proteomics analysis on the lyophilized leech saliva extract to determine the components of it. Moreover, this extract was tested on the in vitro-activated macrophages. The extract decreased the production of the pro-inflammatory cytokines by the activated mammalian macrophages compared to the positive control groups. These results suggest that the lyophilized leech saliva can be utilized as an anti-inflammatory biotechnological drug candidate against inflammatory and autoimmune disorders. In vitro studies will be conducted to further decipher the most active ingredients in the leech saliva. These active components will be tested on the animal models of the inflammatory and autoimmune disorders to show their drug potential.

Transgenesis enables mapping of segmental ganglia in the leech Helobdella austinensis

The analysis of how neural circuits function in individuals and change during evolution is simplified by the existence of neurons identified as homologous within and across species. Invertebrates, including leeches, have been used for these purposes in part because their nervous systems comprise a high proportion of identified neurons, but technical limitations make it challenging to assess the full extent to which assumptions of stereotypy hold true. Here, we introduce Minos plasmid-mediated transgenesis as a tool for introducing transgenes into the embryos of the leech Helobdella austinensis (Spiralia; Lophotrochozoa; Annelida; Clitellata; Hirudinida; Glossiphoniidae). We identified an enhancer driving pan-neuronal expression of markers, including histone2B:mCherry, which allowed us to enumerate neurons in segmental ganglia. Unexpectedly, we found that the segmental ganglia of adult transgenic H. austinensis contain fewer and more variable numbers of neurons than in previously examined leech species.

Biocontrol of snail-borne parasites with the glossiphoniid leech, Helobdella austinensis

Parasites in which freshwater snails are intermediate hosts pose a serious threat to human health worldwide. We show here that freshwater snails can potentially be controlled by leech predation; in principle, this approach could significantly reduce snail-borne parasitic diseases (SBPDs). Specifically, glossiphoniid leeches, Helobdella austinensis and congener species, consume freshwater snails indiscriminately, while other common leeches do not. A single adult H. austenensis, for example, can consume up to its weight in snails, e.g. Physella acuta, per day. Our predator-prey models suggest that snail populations could be eliminated in relatively short time periods (approximately six months) using a leech biocontrol approach. This could have considerable impact on global SBPDs by breaking the intermediate host life cycle.

Spatiotemporal Expression of Anticoagulation Factor Antistasin in Freshwater Leeches

Antistasin, which was originally discovered in the salivary glands of the Mexican leech Haementeria officinalis, was newly isolated from Helobdella austinensis. To confirm the temporal expression of antistasin during embryogenesis, we carried out semi-quantitative RT-PCR. Hau-antistasin1 was uniquely expressed at stage 4 of the cleavage and was strongly expressed in the late stages of organogenesis, as were other antistasin members. In order to confirm the spatial expression of antistasin, we performed fluorescence in situ hybridization in the late stages of organogenesis. The expression of each antistasin in the proboscis showed a similar pattern and varied in expression in the body. In addition, the spatial expression of antistasin orthologs in different leeches showed the possibility of different function across leech species. Hau-antistasin1 was expressed in the same region as hedgehog, which is a known mediator of signal transduction pathway. Hau-antistasin1 is probably a downstream target of Hedgehog signaling, involved in segment polarity signal pathway.

On the origin of leeches by evolution of development

Leeches are a unique group of annelids arising from an ancestor that would be characterized as a freshwater oligochaete worm. Comparative biology of the oligochaetes and the leeches reveals that body plan changes in the oligochaete-to-leech transition probably occurred by addition or modification of the terminal steps in embryonic development and that they were likely driven by a change in the feeding behavior in the ancestor of leeches. In this review article, developmental changes that are associated with the evolution of several leech-specific traits are discussed. These include (1) the evolution of suckers, (2) the loss of chaetae, (3) the loss of septa, and (4) a fixed number of segments. An altered developmental fate of the teloblast is further proposed to be a key factor contributing to the fixation of the segment number, and the evolutionary change in teloblast development may also account for the loss of the ability to regenerate the lost body segments in the leech.

Spatiotemporal expression of a twist homolog in the leech Helobdella austinensis

Genes of the twist family encode bHLH transcription factors known to be involved in the regulation and differentiation of early mesoderm. Here, we report our characterization of Hau-twist, a twist homolog from the leech Helobdella austinensis, a tractable lophotrochozoan representative. Hau-twist was expressed in segmental founder cells of the mesodermal lineage, in subsets of cells within the mesodermal lineage of the germinal plate, in circumferential muscle fibers of a provisional integument during segmentation and organogenesis stages and on the ventral side of the developing proboscis. Thus, consistent with other systems, our results suggest that twist gene of the leech Helobdella might function in mesoderm differentiation.

Hedgehog signaling regulates gene expression in planarian glia

Hedgehog signaling is critical for vertebrate central nervous system (CNS) development, but its role in CNS biology in other organisms is poorly characterized. In the planarian Schmidtea mediterranea, hedgehog (hh) is expressed in medial cephalic ganglia neurons, suggesting a possible role in CNS maintenance or regeneration. We performed RNA sequencing of planarian brain tissue following RNAi of hh and patched (ptc), which encodes the Hh receptor. Two misregulated genes, intermediate filament-1 (if-1) and calamari (cali), were expressed in a previously unidentified non-neural CNS cell type. These cells expressed orthologs of astrocyte-associated genes involved in neurotransmitter uptake and metabolism, and extended processes enveloping regions of high synapse concentration. We propose that these cells are planarian glia. Planarian glia were distributed broadly, but only expressed if-1 and cali in the neuropil near hh+ neurons. Planarian glia and their regulation by Hedgehog signaling present a novel tractable system for dissection of glia biology.

Did the notochord evolve from an ancient axial muscle? The axochord hypothesis

The origin of the notochord is one of the key remaining mysteries of our evolutionary ancestry. Here, we present a multi‐level comparison of the chordate notochord to the axochord, a paired axial muscle spanning the ventral midline of annelid worms and other invertebrates. At the cellular level, comparative molecular profiling in the marine annelids P. dumerilii and C. teleta reveals expression of similar, specific gene sets in presumptive axochordal and notochordal cells. These cells also occupy corresponding positions in a conserved anatomical topology and undergo similar morphogenetic movements. At the organ level, a detailed comparison of bilaterian musculatures reveals that most phyla form axochord‐like muscles, suggesting that such a muscle was already present in urbilaterian ancestors. Integrating comparative evidence at the cell and organ level, we propose that the notochord evolved by modification of a ventromedian muscle followed by the assembly of an axial complex supporting swimming in vertebrate ancestors.