Biology subjects

Delroisse, J.

Publications and source records attributed to Delroisse, J..

12 recordsLinked to original sources

bioRxiv2026

Single-cell transcriptomics reveals transcriptional diversity of sea cucumber perivisceral fluid coelomocytes

Echinoderms possess a complex immune system, primarily relying on coelomocytes - immune cells circulating in coelomic fluids. Over the last few decades, various coelomocytes have been described based on morphological features, with holothuroids exhibiting the highest diversity of cell morphotypes among the different echinoderm classes. However, while the overall immune function of these cells is broadly accepted, their respective functions remain unclear, and molecular data specific to the different cell types are still limited in the literature. In this study, we address this gap in functional information and molecular data by using single-cell RNA sequencing (scRNA-seq) on coelomocytes from the perivisceral fluid of Holothuria forskali. We identified 10 distinct clusters, each assumed to correspond to a distinct transcriptional coelomocyte population. Among these, cluster 0 occupies a central position relative to the others, suggesting it may represent "progenitor cells", whereas cluster 6 is markedly divergent from all other clusters. Functional enrichment analyses revealed that some clusters ensure key immune functions, including pathogen recognition, phagocytosis, complement activation and redox balance regulation. In addition, examination of the processed samples under a microscope confirms the presence of a small proportion of recently discovered carotenocytes (7.0%) in the perivisceral fluid, a cell type rich in carotenoids. By using transcriptomics data previously obtained for this cell type by bulk RNA sequencing (bRNA-seq), it was possible to confidently identify cluster 6 as carotenocytes and provide further insights into their gene expression. While further analyses are needed to link other clusters to the different morphotypes previously described in the literature, this pioneer study presents preliminary data on the functional diversity of holothuroid coelomocytes, which could be of broad interest for a better understanding of holothuroid immunity as well as for the study of immune cell lineage evolution across deuterostomes.

evolutionary biology↗

bioRxiv2025

Carotenoid-based immune response in sea cucumbers relies on newly identified coelomocytes -- the carotenocytes

Sea cucumbers (Holothuroidea, Echinodermata) are marine deuterostomes possessing a complex innate immune system composed of a wide diversity of immune cells--coelomocytes, making them compelling models for exploring the evolution of immunity. This study investigates the functional specialisation of coelomocytes within the two main echinoderm body fluids, namely the perivisceral fluid (PF) from the perivisceral cavity and the hydrovascular fluid (HF) from the hydrovascular-- ambulacral system. Given their specific distribution restricted to the HF, hemocyte-like cells (HELs) are particularly investigated. In echinoderms, hemocytes have been described as reddish cells containing haemoglobin and thus presenting a function in oxygen transport. Using an integrative approach combining cell morphological analyses, pigment profiling and multi-omics technologies, we demonstrate, in the sea cucumber Holothuria forskali, that HELs harbour exceptionally high concentrations of carotenoids, primarily canthaxanthin and astaxanthin--potent antioxidant molecules responsible for their pigmentation. Transcriptomics and proteomics analyses reveal that HELs express candidate genes involved in the carotenoid metabolism pathway as well as catalase, an antioxidant enzyme. Additionally, spectral flow cytometry assays reveal that HELs do not produce reactive oxygen species in contrast to most coelomocyte types, reinforcing the hypothesis of their antioxidant function. HELs also contribute to the formation of large red bodies (i.e., coelomocyte aggregates) and increase in concentration following lipopolysaccharide injections, indicating an active role in immune defence. Given these results, we hypothesise that these cells act after the culmination of the immune response, forming an antioxidant shell around the cellular aggregates to mitigate oxidative stress from reactive oxygen species (ROS) produced within the aggregate while encapsulating pathogens, thus protecting the host tissues. The discovery of carotenoid-carrying coelomocytes constitutes the first report of pigmented coelomocytes in sea cucumbers (except respiratory pigments), challenging the long-standing assumption that these cells contain haemoglobin. Therefore, we propose renaming hemocytes into carotenocytes, at least in this species. However, we think that this newly described coelomocyte type has been wrongly identified as haemoglobin-containing cells in many previous studies and could be present in many other holothuroid species. Our findings thus establish a new paradigm in the study of coelomocytes in echinoderms as well as the function of the hydrovascular system, unique to this phylum.

evolutionary biology↗

bioRxiv2024

Functional characterization of luciferase in a brittle star indicates parallel evolution influenced by genomic availability of haloalkane dehalogenase

Determining why convergent traits use distinct versus shared genetic components is crucial for understanding how evolutionary processes generate and sustain biodiversity. However, the factors dictating the genetic underpinnings of convergent traits remain incompletely understood. Here, we use heterologous protein expression, biochemical assays, and phylogenetic analyses to confirm the origin of a luciferase gene from haloalkane dehalogenases in the brittle star Amphiura filiformis. Through database searches and gene tree analyses, we also show a complex pattern of presence and absence of haloalkane dehalogenases across organismal genomes. These results first confirm parallel evolution across a vast phylogenetic distance, because octocorals like Renilla also use luciferase derived from haloalkane dehalogenases. This parallel evolution is surprising, even though previously hypothesized, because many organisms that also use coelenterazine as the bioluminescence substrate evolved completely distinct luciferases. The inability to detect haloalkane dehalogenases in the genomes of several bioluminescent groups suggests that the distribution of this gene family influences its recruitment as a luciferase. Together, our findings highlight how biochemical function and genomic availability help determine whether distinct or shared genetic components are used during the convergent evolution of traits like bioluminescence.

evolutionary biology↗

bioRxiv2024

Opsin-based photoreception in Crinoids

Opsins are essential photoreceptor proteins that enable both visual and nonvisual light perception in metazoans. Although extensively studied in eyed invertebrates, their role in eyeless organisms such as echinoderms remains underexplored. Within the echinoderm phylum, studies have primarily focused on sea stars, sea urchins, and brittle stars, leaving crinoids, the most basal echinoderm lineage, entirely unexplored. Currently, only a limited number of behavioural observations have suggested that crinoids may possess light sensitivity. This study investigated the behavioural, morphofunctional, and molecular foundations of opsin-based photoreception in Antedon bifida, a European crinoid species from the comatulid order. In this context, the behavioural response to different light wavelengths, characterisation of opsin genes in the recent chromosome-scale genome of this species, opsin immunolocalisation within the crinoid tissues, and in vitro functional characterisation of opsins have been investigated. In vivo tests indicated significant negative phototactic behaviour induced by a wide range of light wavelengths (463-630 nm) with maximum sensitivity to blue light ({lambda}max = 463 nm). In silico genome analyses revealed the presence of only three rhabdomeric opsin genes, located on chromosomes 4 (Abif-opsin 4.1) and 6 (Abif-opsin 4.2 and 4.3). All crinoid opsins were phylogenetically clustered as a sister group to all other echinoderm rhabdomeric opsins, supporting their evolution via duplication of an ancestral gene in the crinoid lineage. The low opsin diversity contrasts with that of other echinoderms, which are generally characterised by up to eight bilaterian opsin types. Interestingly, A. bifida opsin sequences present typical amino acid residues of rhabdomeric opsins of other bilaterians, including two conserved cysteines (C110 and C187), the probable ancestral E181 counterion, the typical G-protein signalling NPxxY(x)6F pattern, a highly conserved lysine potentially covalently bound to a chromophore, and the (D)RY motif, all of which support a photoreceptive function. Heterologous in vitro expression in HEK293T cell cultures subsequently confirmed the photoreceptive function of all three A. bifida opsins. Indeed, these three crinoid opsins formed active complexes with 11, cis-retinal association, and once purified, showed different absorbance peaks in the short wavelengths of the visible light spectrum ranging from 425 to 520 nm. Finally, immunoreactivity to newly generated antibodies against sea star opsins highlighted two potential crinoid opsins in several tissues associated with the ambulacral grooves of the calyx and pinnules. Within these tissues, one Abif-opsin is potentially expressed both in the ectoneural basiepithelial nerve plexus and in the hyponeural nerve plexus. However, a different opsin is also expressed in the sensory papillae of tube feet. Localisation of at least two opsins in different sensory structures suggests the presence of a complex extraocular photoreception system based exclusively on rhabdomeric opsins in this crinoid species.

zoology↗

bioRxiv2024

Abundance, diversity and evolution of tyrosinase enzymes involved in the adhesive systems of mussels and tubeworms

The blue mussel (Mytilus edulis) and the honeycomb tubeworm (Sabellaria alveolata) have evolved similar adhesive systems to cope with the hydrodynamic conditions of the intertidal environment where they live. Both organisms can establish a permanent adhesion through the secretion of adhesive proteins rich in DOPA (3,4-dihydroxyphenylalanine), a post-translationally modified amino acid playing essential roles in interfacial adhesion and bulk cohesion. DOPA is produced by the hydroxylation of tyrosine residues by tyrosinase enzymes, which can also in some cases oxidise it further into dopaquinone Compared to the detailed knowledge available on mussel and tubeworm adhesive proteins, little information exists about the tyrosinases involved in their adhesive systems. By combining different molecular analyses, a catalogue of tyrosinase candidates potentially involved in the adhesive systems of M. edulis and S. alveolata was identified. Some of these candidates were shown to be expressed in the adhesive glands by in situ hybridization, with a high gland-specificity in mussels but not in tubeworms. The diversity of tyrosinases highlighted in the two species suggests the coexistence of different functions (monophenol monooxygenase or catechol oxidase activity) or different substrate specificities. However, the exact role of the different enzymes needs to be further investigated. Phylogenetic analyses support the hypothesis of independent expansions and parallel evolution of tyrosinases involved in adhesive protein maturation in both lineages, supporting the convergent evolution of their DOPA-based adhesion.

evolutionary biology↗

bioRxiv2024

Waves of light at the bottom of the ocean: insights into the luminous systems of three Pennatuloidea (Anthozoa)

Bioluminescence is the production of visible light by living organisms. It occurs through the oxidation of a luciferin substrate catalysed by luciferase enzymes. Auxiliary proteins, such as fluorescent proteins and luciferin-binding proteins, can modify the light emitted wavelength or stabilize reactive luciferin molecules, respectively. Additionally, calcium ions are crucial for the luminescence across various species. Despite the large phylogenetic distribution of bioluminescent organisms, only a few systems have been comprehensively studied. Notably, cnidarian species of the Renilla genus utilize a coelenterazine-dependent luciferase, a calcium-dependent coelenterazine-binding protein and a green fluorescent protein. We investigated the bioluminescence of three sea pen species: Pennatula phosphorea, Anthoptilum murrayi and Funiculina quadrangularis (Pennatuloidea, Anthozoa). Their light-emission spectra reveal peaks at 510, 513 and 485 nm, respectively. A coelenterazine-based reaction was demonstrated in all three species. Using transcriptome analyses, we identified predicted transcripts coding for luciferases, green fluorescent proteins and coelenterazine-binding proteins for P. phosphorea and A. murrayi. Immunodetection confirmed the expression of luciferase in P. phosphorea and F. quadrangularis. We also expressed recombinant luciferase of A. murrayi, confirming its activity. We highlighted the role of calcium ions in bioluminescence, possibly associated with the mechanism of substrate release at the level of coelenterazine-binding proteins. The study proposes a model for anthozoan bioluminescence, offering new avenues for future ecological and functional research on these luminous organisms.

zoology↗

bioRxiv2023

The brittle star genome illuminates the genetic basis of animal appendage regeneration

Species within nearly all extant animal lineages are capable of regenerating body parts. However, it remains unclear whether the gene expression programme controlling regeneration is evolutionarily conserved. Brittle stars are a species-rich class of echinoderms with outstanding regenerative abilities, but investigations into the genetic bases of regeneration in this group have been hindered by the limited genomic resources. Here, we report a chromosome-scale genome assembly for the brittle star Amphiura filiformis. We show that the brittle star genome is the most rearranged amongst echinoderms sequenced to date, featuring a reorganised Hox cluster reminiscent of the rearrangements observed in sea urchins. In addition, we performed an extensive profiling of gene expression during brittle star adult arm regeneration and identified sequential waves of gene expression governing wound healing, proliferation and differentiation. We conducted comparative transcriptomic analyses with other invertebrate and vertebrate models for appendage regeneration and uncovered hundreds of genes with conserved expression dynamics, particularly during the proliferative phase of regeneration. Our findings emphasise the crucial importance of echinoderms to detect long-range expression conservation between vertebrates and classical invertebrate regeneration model systems.

evolutionary biology↗

bioRxiv2021

Integument transcriptome profile of the European sea cucumber Holothuria forskali (Holothuroidea, Echinodermata)

In non-model organisms, Next Generation Sequencing (NGS) technology improve our ability to analyze gene expression and identify new genes or transcripts of interest. In this research, paired-end Illumina HiSeq sequencing has been used to describe a composite transcriptome based on two libraries generated from dorsal and ventral integuments of the European sea cucumber Holothuria forskali (Holothuroidea, Echinodermata). A total of 43,044,977 million HQ reads were initially generated. After de novo assembly, a total of 111,194 unigenes were predicted. On all predicted unigenes, 32,569 show significant matches with genes/proteins present in the reference databases. Around 50% of annotated unigenes were significantly similar to sequences from the purple sea urchin Strongylocentrotus purpuratus genome. Annotation analyses were performed on predicted unigenes using public reference databases. These RNA-seq data provide an interesting resource for researchers with a broad interest in sea cucumber biology.

zoology↗

bioRxiv2020

Evolutionarily ancient role of cholecystokinin-type neuropeptide signalling as an inhibitory regulator of feeding-related processes revealed in an echinoderm

Cholecystokinin (CCK) / sulfakinin (SK)-type neuropeptides regulate feeding and digestion in chordates and protostomes (e.g. insects). Here we characterised CCK/SK-type signalling for the first time in a non-chordate deuterostome - the starfish Asterias rubens (phylum Echinodermata). In this species, two neuropeptides (ArCCK1, ArCCK2) derived from the precursor protein ArCCKP act as ligands for a CCK/SK-type receptor (ArCCKR) and are expressed in the nervous system, digestive system, tube feet and body wall. Furthermore, ArCCK1 and ArCCK2 cause dose-dependent contraction of cardiac stomach, tube foot and body wall apical muscle preparations in vitro and injection of these neuropeptides in vivo triggers cardiac stomach retraction and inhibition of the onset of feeding in A. rubens. Thus, an evolutionarily ancient role of CCK/SK-type neuropeptides as inhibitory regulators of feeding-related processes in the Bilateria has been conserved in the unusual and unique context of the extra-oral feeding behaviour and pentaradial body plan of an echinoderm.

physiology↗

bioRxiv2018

De novo Transcriptome Analyses Provide Insights into Opsin-based Photoreception in the Lantern shark Etmopterus spinax

The velvet belly lantern shark (Etmopterus spinax) is a small deep-sea shark commonly found in the Easter Atlantic and the Mediterranean Sea. In this study, paired-end illumina HiSeqTM technology has been employed to analyse transcriptome data from eye and ventral skin tissues of the lantershark species. About 64 and 49 million Illumina reads were generated from skin and eyetissues respectively. The assembly allowed us to predict 119,749 total unigenes including 94,569 for the skin transcriptome and 94,365 for the eye transcriptome while 74,753 were commonly found in both transcriptomes. Among unigenes, 60,322 sequences were annotated using classical public databases. The assembled and annotated transcriptomes provide a valuable resource for further understanding of the shark biology. We identified potential \"light-interacting toolkit\" genes including multiple genes related to ocular and extraocular light perception processes such as opsins. In particular, a single rhodopsin gene mRNA and its potentially associated peropsin were only detected in the eye transcriptome confirming a monochromatic vision of the lantern-shark. Conversely, an encephalopsin mRNA was mainly detected in the skin transcriptome. The encephalopsin was immunolocalized in various shark tissues confirming its wide expression in the shark skin and pinpointing a possible functional relation with the photophore, i.e. epidermal light organs. We hypothesize that extraocular photoreception might be involved in the bioluminescence control possibly acting on the shutter opening and/or the photocyte activity itself.

evolutionary biology↗

bioRxiv2018

Thioredoxins induce oocyte maturation in holothuroids (Echinodermata)

Chromatographic fractions of a rough extract of echinoid spawn (REES) has been demonstrated to efficiently induce oocyte maturation in aspidochirote holothuroids. The method is so efficient that it is now used in holothuriculture to get fertilised eggs even outside the reproductive period of the aquacultured species. We here isolate and identify from echinoid spawns the molecule responsible for the induction of the oocyte maturation in the Mediterranean holothuroid Holothuria tubulosa and the Indo-Pacific Holothuria scabra. The use of proteinase K and dialysing membranes indicates that the active molecule is a protein with a molecular weight superior to 12,000 kDa. The active molecule has been isolated on G-100 Sephadex chromatography column. Active chromatographic fractions include seven proteins identified with nanoLC-MS/MS technique. One of them, identify as a thioredoxin-2 and to which the name Trx-REES has been given, leads up to levels of maturation similar to those obtained with the REES and with a commercial thioredoxin extracted from Escherichia coli. Occurrence of thioredoxin in REES was confirmed by immunoblot analysis, and the maturation-inducing properties of thioredoxin were positively checked in using anti-thioredoxin antibodies. A peptide of 6 AAs corresponding to the active site of Trx-REES, composed of WCNPCK, was synthesised and its efficiency in holothuroid oocyte maturation tested. At some concentrations, the peptide was 1.2 times more active than the REES.

zoology↗

bioRxiv2017

Ophiuroid Phylotranscriptomics Enables Discovery Of Novel Echinoderm Representatives Of Bilaterian Neuropeptide Families And Reconstruction Of Neuropeptide Precursor Evolution Over ~270 Million Years

BackgroundNeuropeptides are a diverse class of intercellular signaling molecules that mediate neuronal regulation of many physiological and behavioural processes, including feeding, reproduction and locomotion. Recent advances in genome/transcriptome sequencing are enabling identification of neuropeptide precursor proteins in species from a growing variety of animal taxa, providing new insights into the evolution of neuropeptide signaling. Here we report a phylo-transcriptomic analysis of neuropeptide precursors in over fifty species of brittle stars (Class Ophiuroidea; Phylum Echinodermata).\n\nResultsDetailed analysis of transcriptome sequence data from three brittle star species, Ophionotus victoriae, Amphiura filiformis and Ophiopsila aranea, enabled the first comprehensive identification of neuropeptide precursors in ophiuroids. Representatives of over thirty bilaterian neuropeptide precursor families were identified, some of which occur as paralogs (e.g. thyrotropin-releasing hormone, corticotropin-releasing hormone, cholecystokinin, somatostatin and pedal peptide). Furthermore, homologs of endothelin/CCHamide, eclosion hormone, neuropeptide-F/Y and nucleobinin/nesfatin were discovered here in a deuterostome/echinoderm for the first time. The majority of ophiuroid neuropeptide precursors contain a single copy of a neuropeptide, but several precursors comprise multiple copies of identical or non-identical, but structurally-related, neuropeptides. Here we performed an unprecedented investigation of the evolution of neuropeptide copy-number over a period of ~270 million years by analysing sequence data from over fifty ophiuroid species, with reference to a robust phylogeny. Interestingly, the number of neuropeptide copies in the majority of precursors was constant across all the species examined, but examples of clade-specific losses/gains of neuropeptides were also observed.\n\nConclusionsWe report here the most comprehensive analysis to date of neuropeptide precursors in the phylum Echinodermata, with novel representatives of several bilaterian neuropeptide families discovered for the first time in echinoderms. Furthermore, analysis of precursor proteins comprising multiple copies of identical or related neuropeptides across ~270 million years of ophiuroid evolution indicates that the composition of neuropeptide \"cocktails\" is functionally important, but with plasticity over long evolutionary time scales.

neuroscience↗