Biology subjects

Blanchoud, S.

Publications and source records attributed to Blanchoud, S..

7 recordsLinked to original sources

bioRxiv2025

The livebearers platyfish and swordtails partially regenerate their hearts with persistent scarring

Heart regeneration varies among vertebrates, with zebrafish serving as a reference species for efficient cardiac restoration. How this capacity diversified across teleosts is an emerging question, particularly following the recent identification of non-regenerative cardiac repair in medaka and cavefish. Here, we investigate heart restorative capacity following cryoinjury in two livebearers, platyfish and swordtails (Xiphophorus species), belonging to the Poeciliidae family. We demonstrate that their hearts lack the vascularized compact myocardium, a ventricular layer implicated in the restorative response in zebrafish. Following cryoinjury, both poeciliids failed to rapidly deposit fibrotic tissue that normally reinforces the damaged ventricle. This deficiency correlates with pronounced wound protrusion. Although the remaining myocardium displayed an initial proliferative response, subsequently deposited collagenous scar tissue permanently sealed the ventricular wall, precluding complete regeneration. Transcriptomic analysis identified several divergently regulated pathways between cryoinjured hearts of zebrafish and platyfish, most notably in immune response regulation. These differences were validated by delayed leukocyte infiltration and sustained inflammation in platyfish, contrasting with the rapid and self-resolving inflammatory response in zebrafish. Our findings demonstrate that Xiphophorus species have evolved hearts with compromised regenerative capacity, characterized by initial wound protrusion and permanent scarring. These results establish that lineage-specific evolutionary traits can profoundly shape regenerative competence across teleosts, with broad implications for understanding the mechanistic basis of cardiac repair. Highlights{middle dot} Viviparous poeciliids lack vascularized compact myocardium. {middle dot} Inflammation and fibrosis are delayed in the cryoinjured platyfish ventricle. {middle dot} Ventricular cryoinjury in Xiphophorus leads to transient bulging-type deformation. {middle dot} Failure to form a myocardial bridge results in permanent scarring.

developmental biology↗

bioRxiv2024

First chromosome-level genome assembly of the colonial tunicate Botryllus schlosseri

Botryllus schlosseri (Tunicata) is a colonial chordate that has long been studied for its multiple developmental pathways and regenerative abilities and its genetically determined allorecognition system based on a polymorphic locus that controls chimerism and cell parasitism. We present the first chromosome-level genome assembly from an isogenic colony of B. schlosseri clade A1 using a mix of long and short reads scaf-folded using Hi-C. This haploid assembly spans 533 Mb, of which 96% are found in 16 chromosome-scale scaffolds. With a BUSCO completeness of 91.2%, this complete and contiguous B. schlosseri genome assembly provides a valuable genomic resource for the scientific community and lays the foundation for future investigations into the molecular mechanisms underlying coloniality, regeneration, histocompatibility, and the immune system in tunicates.

genomics↗

bioRxiv2022

Phylogeographic and morphological analysis of Botrylloides niger Herdman, 1886 from the northeastern Mediterranean Sea

Botrylloides niger is an invasive marine filter-feeding invertebrate that is believed to originate from the West Atlantic region. This species of colonial tunicate has been observed on several locations along the coasts of Israel and around the Suez Canal but it has not yet been reported on the coasts of the northeastern Mediterranean Sea (NEMS), suggesting an ongoing Lessepsian migration. However, the extent of this invasion might be concealed by reports of other potentially misidentified species of Botrylloides, given that the strong morphological similarities within this genus renders taxonomical identification particularly challenging. In this study, we performed a phylogeographic and morphological analysis of B. niger in the NEMS. We collected 241 samples from 8 sampling stations covering 824 km of coastlines of NEMS. We reported 14 different morphotypes, of which the orange-brown, orange and brown-striped morphs were the most abundant. Using the mitochondrial cytochrome C oxidase I (COI), one of the four most commonly used DNA barcoding marker, we identified 4 haplotypes with the Konack (H4) and the Mezitli (H3) ones being the most diverged. The COI haplotypes clustered with the reference B. niger sequences from GenBank and separated from sister Botrylloides species with high confidence. We confirmed our identification using the three additional barcoding markers (Histone 3, 18S rRNA and 28S rRNA), which all matched with over 99% similarity to the reference sequences. In addition, we monitored the Kzkalesi station for a year and applied temporal analysis to the colonies collected. The colonies regressed during winter while resettled and expanded during summer. We performed gene flow analysis on our spatial data that identified a possible population subdivision at the sampling site of Side, which might be caused by a local freshwater input. Overall, we here present the first report on the presence of Botrylloides niger in the NEMS, we show that this species is commonly present throughout this region and with a particularly high morphological as well as genomic diversity.

zoology↗

bioRxiv2021

In-land long-term culture of colonial ascidians

Tunicates are highly diverse marine invertebrate filter-feeders that are vertebrates closest relatives. These organisms, despite a drastically different body plan during their adulthood, have a tissue complexity related to that of vertebrates. Ascidians, which compose most of the Tunicata, are benthic sessile hermaphrodites that reproduce sexually through a motile tadpole larval stage. Over half of the known ascidians species are able to reproduce asexually by budding, typically leading to the formation of colonies where animals, called zooids, are interconnected through an external vascular system. In addition, colonial ascidians are established models for important biological processes including allorecognition, immunobiology, aging, angiogenesis and whole-body regeneration. However, the current paucity in breeding infrastructures limits the study of these animals to coastal regions. To promote a wider scientific spreading and popularity of colonial ascidians, we have developed a flexible recirculating husbandry setup for their long-term in-lab culture. Our system is inspired both by the flow-through aquariums used by coastal ascidian labs, as well as by the recirculating in-lab systems used for zebrafish research. Our hybrid system thus combines colony breeding, water filtering and food culturing in a semi-automated system where specimens develop on hanging microscopy glass slides. Temperature, light/dark cycles, flow speed and feeding rates can be controlled independently in four different breeding environments to provide room for species-specific optimization as well as for running experiments. This setup is complemented with a quarantine for the acclimatization of wild isolates. Herein we present our success in breeding Botrylloides diegensis, a species of colonial ascidians, for more than 3 years in recirculating artificial seawater over 600 km away from their natural habitat. We show that colonies adapt well to in-lab culturing provided that a suitable marine microbiome is present, and that a specific strain can be isolated, propagated and efficiently used for research over prolonged periods of time. The flexible and modular structure of our system can be scaled and adapted to the needs of specific species, such as Botryllus schlosseri, as well as of particular laboratory spaces. Overall, we show that Botrylloides diegensis can be proficiently bred in-land and suggest that our results can be extended to other species of colonial ascidians to promote research on these fascinating animals. HighlightsO_LIFirst artificial seawater based recirculating aquaculture for colonial ascidians C_LIO_LIOver 3 years of continuous breeding C_LIO_LISemi-automated setup with minimized maintenance C_LIO_LIGood biomass production for strain propagation C_LIO_LI4 different culture conditions for optimized breeding for species of interest C_LI

zoology↗

bioRxiv2021

Hydrodynamic stress and phenotypic plasticity of the zebrafish regenerating fin

Understanding how extrinsic factors modulate genetically encoded information to produce a specific phenotype is of prime scientific interest. In particular, the feedback mechanism between abiotic forces and locomotory organs during morphogenesis to achieve efficient movement is a highly relevant example of such modulation. The study of this developmental process can provide unique insights on the transduction of cues at the interface between physics and biology. Here, we take advantage of the natural ability of adult zebrafish to regenerate their amputated fins to assess its morphogenic plasticity upon external modulations. Using a variety of surgical and chemical treatments, we are able to induce phenotypic responses to the structure of the fin. In particular, fin cleft depth and the bifurcation of the bony rays are modulated by the surface area of the stump. To dissect the role of mechanotransduction in this process, we investigate the patterns of hydrodynamic forces acting on the surface of a zebrafish fin during regeneration by using particle tracking velocimetry on a range of biomimetic hydrofoils. This experimental approach enables us to quantitatively compare hydrodynamic stress distributions over flapping fins of varying sizes and shapes. As a result, viscous shear stress acting on the tip of the fin and the resulting internal tension are proposed as suitable signals for guiding the regulation of ray growth dynamics and branching pattern. Our findings suggest that mechanical forces are involved in the fine-tuning of the locomotory organ during fin morphogenesis.

biophysics↗

bioRxiv2017

De novo draft assembly of the Botrylloides leachii genome provides further insight into tunicate evolution.

Tunicates are marine invertebrates that compose the closest phylogenetic group to the vertebrates. This chordate subphylum contains a particularly diverse range of reproductive methods, regenerative abilities and life-history strategies. Consequently, tunicates provide an extraordinary perspective into the emergence and diversity of chordate traits. To gain further insights into the evolution of the tunicate phylum, we have sequenced the genome of the colonial Stolidobranchian Botrylloides leachii.\n\nWe have produced a high-quality (90 % BUSCO genes) 159 Mb assembly, containing 82 % of the predicted total 194 Mb genomic content. The B. leachii genome is much smaller than that of Botryllus schlosseri (725 Mb), but comparable to those of Ciona robusta and Molgula oculata (both 160 Mb). We performed an orthologous clustering between five tunicate genomes that highlights sets of genes specific to some species, including a large group unique to colonial ascidians with gene ontology terms including cell communication and immune response.\n\nBy analysing the structure and composition of the conserved gene clusters, we identified many examples of multiple cluster breaks and gene dispersion, suggesting that several lineage-specific genome rearrangements occurred during tunicate evolution. In addition, we investigate lineage-specific gene gain and loss within the Wnt, Notch and retinoic acid pathways. Such examples of genetic change within these highly evolutionary conserved pathways commonly associated with regeneration and development may underlie some of the diverse regenerative abilities observed in the tunicate subphylum. These results supports the widely held view that tunicate genomes are evolving particularly rapidly.

genomics↗

bioRxiv2017

Histological and haematological analysis of the ascidian Botrylloides leachii (Savigny, 1816) during whole-body regeneration

Abstract (250 words)Whole-body regeneration, the formation of an entire adult from only a small fragment of its own tissue, is extremely rare among chordates. Exceptionally, in the colonial ascidian Botrylloides leachii, a fully functional adult is formed from their common vascular system, upon ablation of all adults from the colony, in just 10 days thanks to their high blastogenetic potential. While previous studies have identified key genetic markers and morphological changes, no study has yet focused on the haematological aspects of regeneration despite the major involvement of the remaining vascular system and the contained haemocytes in this process. To dissect this process, we analysed colony blood flow patterns using time-lapse microscopy to obtain a quantitative description of the velocity, reversal pattern, and average distance travelled by haemocytes. We also observed that flows present during regeneration are powered by temporally and spatially synchronized contractions of the terminal ampullae. In addition, we revised previous studies on B. leachii haematology as well as asexual development using histological sectioning, and compared the role of haemocytes during whole-body regeneration. We found that regeneration starts with a rapid healing response characterized by blood clotting and infiltration of immunocytes, followed by increased activity of haemoblasts, recruitment of macrophage-like cells for clearing the tissues of debris, and their subsequent disappearance from the circulation concomitant with the maturation of a single regenerated adult. Overall, we provide a uniquely detailed account of the haematological properties of regenerating B. leachii colonies, providing novel lines of inquiry towards the decipherment of regeneration in chordates.

cell biology↗