Biology subjects

Barreau, C.

Publications and source records attributed to Barreau, C..

3 recordsLinked to original sources

bioRxiv2018

The genome of the jellyfish Clytia hemisphaerica and the evolution of the cnidarian life-cycle

Jellyfish (medusae) are a distinctive life-cycle stage of medusozoan cnidarians. They are major marine predators, with integrated neurosensory, muscular and organ systems. The genetic foundations of this complex form are largely unknown. We report the draft genome of the hydrozoan jellyfish Clytia hemisphaerica and use multiple transcriptomes to determine gene use across life-cycle stages. Medusa, planula larva and polyp are each characterised by distinct transcriptome signatures reflecting abrupt life cycle transitions, and all deploy a mixture of phylogenetically old and new genes. Medusa specific transcription factors, including many with bilaterian orthologs, associate with diverse neurosensory structures. Compared to Clytia, the polyp-only hydrozoan Hydra has lost many of the medusa-expressed transcription factors, despite similar overall rates of gene content and sequence evolution. Absence of expression and gene loss among Clytia orthologs of genes patterning the anthozoan aboral pole, secondary axis and endomesoderm support simplification of planulae and polyps in Hydrozoa, including loss of bilateral symmetry. Consequently, although the polyp and planula are generally considered the ancestral cnidarian forms, in Clytia the medusa maximally deploys ancestral cnidarian-bilaterian transcription factor gene complexity.

evolutionary biology↗

bioRxiv2017

Inhibition of granulocyte ROS production by opioids prevents regeneration

Inhibition of regeneration and induction of healing are classic outcomes of tissue repair in adult mammals. Here, by using gain and loss of function experiments, we demonstrate that both endogenous and exogenous opioids prevent tissue regeneration in adults, by inhibiting the early reactive oxygen species (ROS) production occurring after lesion and required for regeneration. These effects can be overcome and regeneration induced by the use of an opioid antagonist. These results, obtained in both gold-standard adult zebrafish and a newly-developed model of regeneration in adult mammals, demonstrate that this mechanism can be considered as a general paradigm in vertebrates. In addition, we show that opioids act via signaling through peripheral mu-receptors expressed on granulocytes. This work clearly demonstrates the deleterious role of opioids on tissue regeneration through the control of ROS production in vertebrates and thus questions about opioid-based analgesia in perioperative care.

physiology↗

bioRxiv2017

Jellyfish Oocyte Maturation Inducing Hormone And Neuroendocrine Regulation Of Reproduction

Oocyte meiotic maturation is a critical process for sexually reproducing animals, and its core cytoplasmic regulators are highly conserved between species. In contrast, the few known Maturation Inducing Hormones (MIHs) that act on oocytes to initiate this process have highly variable molecular natures. Using the hydrozoan jellyfish species Clytia and Cladonema, which undergo oocyte maturation in response to dark-light and light-dark transitions respectively, we deduced from gonad transcriptome data amidated tetrapeptide sequences and found that synthetic peptides could induce maturation of isolated oocytes at nanomolar concentrations. Antibody preabsorption experiments conclusively demonstrated that these W/RPRPamide-related neuropeptides account for endogenous MIH activity produced by isolated gonads. We further showed that the MIH peptides are synthesised by neural-type cells in the gonad, are released following dark-light / light-dark transitions, and probably act on the oocyte surface. They are produced by male as well as female jellyfish and can trigger both sperm and egg release, suggesting a role in spawning coordination. We propose an evolutionary link between hydrozoan MIH and the neuropeptide hormones that regulate reproduction upstream of MIH in bilaterian species.

developmental biology↗