Deep Sequencing and Annotation of the Trichoplax adhaerens mRNA Transcriptome Identifies Novel Genes and a Rich Repertoire of Neural Signaling Machinery, Providing Insight into Nervous System Evolution

Trichoplax adhaerens is an early-diverging animal capable of motile behavior such as feeding, chemotaxis, and phototaxis, despite lacking synaptically-connected neurons and muscles. Our lab has produced a high-quality T. adhaerens transcriptome in which ~85% of the assembled genes are complete protein-coding sequences, with 2,483 newly-identified genes missed in the genome sequencing effort. One objective of this research was to identify genes involved in neural signaling. Using in silico prediction algorithms we identified an array of neuropeptide genes, GPCRs, ion channels, and synaptic scaffolding and signaling proteins. We also discovered a previously unknown group of presynaptic Rab3-Interacting Molecule (RIM) homologues in the animal phylogeny, absent in humans but present in many invertebrates. Our work sets the stage for future studies aimed at understanding the concurrent evolution of metazoan cell types, and their ability to communicate with each other through various forms of cell signaling including electrochemical signaling in the nervous system.M.Sc