Did the Neuron evolve twice?

Neurons are essential for sensing and processing stimuli in animals, yet it remains unresolved whether they evolved once or multiple times. Recent phylogenetic and molecular evidence suggests that comb jellies (ctenophores) may have developed neurons independently. Single-cell RNA-sequencing offers a powerful approach to test this hypothesis by comparing the gene expression profiles of neuron-like cells across species. If ctenophore neurons evolved independently, they should rely on distinct regulatory genes; a shared developmental toolkit would instead support a common origin. This proposal aims to combine single-cell RNA-seq with phylogenomic methods to determine whether neurons evolved once or multiple times in metazoans.