Single cell transcriptomics identifies conserved regulators of neurosecretory lineages

Communication in bilaterian nervous systems is mediated by electrical and secreted signals, however, the evolutionary origin and relation of neurons to other secretory cell types has not been elucidated. Here we use developmental single cell RNA-sequencing in the cnidarian Nematostella vectensis, representing an early evolutionary lineage with a simple nervous system. Validated by transgenics, we demonstrate that neurons, stinging cells, and gland cells arise from a common multipotent progenitor population. We identify the conserved transcription factor gene SoxC as a key upstream regulator of all neurosecretory lineages and demonstrate that SoxC knockdown eliminates both neuronal and secretory cell types. While in vertebrates and many other bilaterians neurogenesis is largely restricted to early developmental stages, we show that in the sea anemone differentiation of neurosecretory cells is maintained throughout all life stages, and follows the same molecular trajectories from embryo to adulthood, ensuring lifelong homeostasis of neurosecretory cell lineages.