Evolution of neurohormone function revealed by actions of kisspeptin-type peptides in an echinoderm

This study has revealed that kisspeptin-type neuropeptides are evolutionarily ancient and pleiotropic regulators of processes that extend beyond reproductive physiology. Furthermore, the excitatory actions of ArKP2.2 in A. rubens are consistent with stimulatory effects of kisspeptins in vertebrates; accordingly, ArKP2.2 acts as a ligand for a receptor (ArKPR3) that is closely related to vertebrate kisspeptin receptors. On the other hand, phylogenetic analysis of receptors for ArKP1.1 and ArKP1.2 indicates that inhibitory kisspeptin signalling either evolved uniquely in Ambulacraria (echinoderms, hemichordates) or originated in Urbilateria but was lost in chordates.