Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

Evolution of Synapses and Neurotransmitter Systems: The Divide-and-Conquer Model for Early Neural Cell-Type Evolution

Version 1 : Received: 30 September 2021 / Approved: 1 October 2021 / Online: 1 October 2021 (12:44:15 CEST)

A peer-reviewed article of this Preprint also exists.

Journal reference: Current Opinion in Neurobiology 2021, 71, 127-138
DOI: 10.1016/j.conb.2021.11.002

Abstract

Nervous systems evolved around 560 million years ago to coordinate and empower animal bodies. Ctenophores – one of the earliest-branching lineages – are thought to share few neuronal genes with bilaterians and may have evolved neurons convergently. Here we review our current understanding of the evolution of neuronal molecules in non-bilaterians. We also reanalyse single-cell sequencing data in light of new cell-cluster identities from a ctenophore and uncover evidence supporting the homology of one ctenophore neuron-type with neurons in Bilateria. The specific coexpression of the presynaptic proteins Unc13 and RIM with voltage-gated channels, neuropeptides and homeobox genes pinpoint a spiking sensory-peptidergic cell in the ctenophore mouth. Similar Unc13-RIM neurons may have been present in the first eumetazoans to rise to dominance only in stem Bilateria. We hypothesize that the Unc13-RIM lineage ancestrally innervated the mouth and conquered other parts of the body with the rise of macrophagy and predation during the Cambrian explosion.

Keywords

choanoflagellates; sponges; ctenophores; placozoans; cnidarians; synapse; neuron evolution; neuropeptides

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