Discovering missing links in neuropeptide evolution and function

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For humans and other animals to survive and reproduce, growth and physiological/behavioural processes such as feeding and mating need to be controlled and coordinated by nervous and endocrine systems. This is achieved by cells secreting "messenger molecules" that are act on other cells/tissues/organs (e.g. muscles) to stimulate or inhibit their activity over short (seconds) to long (hours-days) timescales. The largest and most diverse class of neuronal messenger molecules are "neuropeptides", which exert their effects by binding to specific receptor proteins on target cells.Many important insights into how neuropeptides control physiology and behaviour have been obtained from experimental studies on invertebrate animals such as the fruit fly Drosophila and the nematode worm C. elegans. However, there are still many gaps in our knowledge of neuropeptide signalling systems. For example, evolutionary relationships between some neuropeptides in humans and invertebrates have not been determined and there are many so-called 'orphan receptors' for which neuropeptide partners have yet to be discovered. Importantly, exciting new opportunities to address these issues have been provided by sequencing of the genomes of an ever-growing variety of animals.In the proposed project we will use echinoderms (starfish, sea urchin) as experimental systems to discover missing links in our knowledge of neuropeptide evolution and function. The main rationales for our selection of echinoderms as experimental systems for this project are:Firstly, as deuterostome invertebrates, echinoderms occupy an evolutionary position in the animal kingdom that provides an important link between research on well-studied protostome invertebrates such as Drosophila and C. elegans and research on humans and other vertebrates.Secondly, in collaboration with the Sanger Institute's Darwin Tree of Life Project we have recently obtained a chromosomal-level assembly of the genome sequence of the common starfish Asterias rubens, providing an valuable new resource for researchers in the UK and overseas.Thirdly, sea urchins are already well-established experimental systems that have been used extensively for determination of the genetic mechanisms that control embryonic development in animals.There are two main aims of this project:Firstly, we will analyse the A. rubens genome sequence to identify genes encoding neuropeptides as candidate partners for 'orphan receptors' in this species and then we will perform biochemical experiments to test predicted neuropeptide-receptor partnerships. Discovering neuropeptides that are partners for 'orphan receptors' in starfish will provide missing links in our knowledge of the evolution of neuropeptide signalling in the animal kingdom. This will have broad impact by influencing interpretation of findings from research on neuropeptide signalling in other animals, including humans.Secondly, we will use state-of-the-art gene-knockout methods (CRISPR-cas9) to investigate the functions of neuropeptides in sea urchin and starfish larvae, which have nervous systems comprising much smaller populations of neurons than adult animals, but with comparable molecular complexity. By discovering the physiological/behavioural roles of multiple neuropeptide types for the first time during the larval stage of echinoderms, we will obtain important new insights into the evolution of neuropeptide function in the animal kingdom. This will facilitate advancement of the broader aim of reconstructing the evolutionary history of neuropeptide signalling systems to gain an understanding of how and when neuropeptides were recruited to regulate diverse physiological and behavioural processes in different branches of tree of animal life and in contrasting environmental contexts. The findings of this study will also provide insights that may facilitate development of novel therapeutic agents that target neuropeptide receptors in humans.