2023/09/19 by Sebastián R. Najle, Xavier Grau‐Bové, Anamaria Elek +11 · 1 voice · 1 citation
Earth and Planetary Sciences · Biochemistry, Genetics and Molecular Biology · #Marine Invertebrate Physiology and Ecology #Planarian Biology and Electrostimulation #Zebrafish Biomedical Research Applications
paper · pdf · doi:10.1016/j.cell.2023.08.027
openalex publication_date 2023/09/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
The assembly of the neuronal and other major cell type programs occurred early in animal evolution. We can reconstruct this process by studying non-bilaterians like placozoans. These small disc-shaped animals not only have nine morphologically described cell types and no neurons but also show coordinated behaviors triggered by peptide-secreting cells. We investigated possible neuronal affinities of these peptidergic cells using phylogenetics, chromatin profiling, and comparative single-cell genomics in four placozoans. We found conserved cell type expression programs across placozoans, including populations of transdifferentiating and cycling cells, suggestive of active cell type homeostasis. We also uncovered fourteen peptidergic cell types expressing neuronal-associated components like the pre-synaptic scaffold that derive from progenitor cells with neurogenesis signatures. In contrast, earlier-branching animals like sponges and ctenophores lacked this conserved expression. Our findings indicate that key neuronal developmental and effector gene modules evolved before the advent of cnidarian/bilaterian neurons in the context of paracrine cell signaling.