Abstract
Neuropeptides are evolutionarily ancient mediators of neuronal signalling in nervous systems. With recent advances in genomics/transcriptomics, an increasingly wide range of species has become accessible for molecular analysis. The deuterostomian invertebrates are of particular interest in this regard because they occupy an ‘intermediate' position in animal phylogeny, bridging the gap between the well-studied model protostomian invertebrates (e.g. Drosophila melanogaster, Caenorhabditis elegans) and the vertebrates. Here we have identified 40 neuropeptide precursors in the starfish Asterias rubens, a deuterostomian invertebrate from the phylum Echinodermata. Importantly, these include kisspeptin-type and melanin-concentrating hormone-type precursors, which are the first to be discovered in a non-chordate species. Starfish tachykinin-type, somatostatin-type, pigment-dispersing factor-type and corticotropin-releasing hormone-type precursors are the first to be discovered in the echinoderm/ambulacrarian clade of the animal kingdom. Other precursors identified include vasopressin/oxytocin-type, gonadotropin-releasing hormone-type, thyrotropin-releasing hormone-type, calcitonin-type, cholecystokinin/gastrin-type, orexin-type, luqin-type, pedal peptide/orcokinin-type, glycoprotein hormone-type, bursicon-type, relaxin-type and insulin-like growth factor-type precursors. This is the most comprehensive identification of neuropeptide precursor proteins in an echinoderm to date, yielding new insights into the evolution of neuropeptide signalling systems. Furthermore, these data provide a basis for experimental analysis of neuropeptide function in the unique context of the decentralized, pentaradial echinoderm bauplan.
Highlights
Neuropeptides are intercellular signalling molecules that are secreted by neurons to act as neurotransmitters, modulators of synaptic transmission or hormones
By analysing A. rubens nerve cord transcriptome sequence data, we have identified 40 candidate neuropeptide precursors, which for the purposes of discussion we have divided into four groups
Previous studies have identified corticotropin-releasing hormone (CRH)-type precursors in other deuterostomian invertebrates, including the hemichordate S. kowalevskii [5,6] and the cephalochordate B. floridae [5], and in figure 8 we show an alignment of the A. rubens CRH-type peptide (ArCRH) with homologues from these two species, human CRH/urocortin-type peptides and CRH-type peptides in lophotrochozoan protostomes
Summary
Neuropeptides are intercellular signalling molecules that are secreted by neurons to act as neurotransmitters, modulators of synaptic transmission or hormones. They range in size from just three amino acids, such as thyrotropin-releasing hormone (TRH), to much longer polypeptides (e.g. neuropeptide Y, which comprises 36 residues). The evolutionary origins of neuropeptides as regulators of physiology and behaviour are ancient; for example, neuropeptide signalling pathways are key components of the nervous systems of basal animal phyla such as the cnidarians [3], and the origins of some peptide signalling pathways may pre-date the emergence of animals with nervous systems [4].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
