ORIGINEURO · Tracking the deep evolutionary origins of neurons

The evolutionary origin of first neurons was key for animals as it allowed them to rapidly detect environmental cues and to coordinate responses to threats or opportunities. The evolutionary origin of neurons however remains a highly debated and largely enigmatic subject since there is no broad agreement on the relationships at the base of the animal tree and not all non-bilaterian animals have neurons. Strikingly, early branching animals, as well as their closest unicellular relatives already contain many components of the molecular toolkits for neuronal functions. ORIGINEURO addresses fundamental questions regarding the evolutionary origin of synapses and neurons from molecular to cellular scales. My recent studies on choanoflagellates, the closest living relatives of all animals, and ctenophores (comb jellies), strong candidates for one of the first animal lineages, are providing exciting, new and surprising clues into the ancestry of synaptic proteins including the discovery of a neurosecretory apparatus in choanoflagellates and a unique nervous system in ctenophores. The proposed 5-year programme brings together correlative volume electron microscopy, super-resolution imaging, quantitative live cell imaging, state-of-the-art molecular biology and single cell RNA sequencing focusing on a ctenophore as model organism. Objective 1 will provide a detailed understanding of the ultrastructure and connectivity of ctenophore neurons forming the subepithelial nerve net. Objective 2 will shed light on the so far elusive ctenophore neuron development. By functionally characterizing ctenophore neurons (Objective 3) I will understand how they work and what they do. ORIGINEURO fills a research gap and will provide insights into how many ways to build a neural network. Thus, ORIGINEURO aims at challenging the paradigm of network activity emerging through cellular diversification and synaptic connections.