An adult stem-like cell population generates germline and neurons in the sea anemone Nematostella vectensis
Most genetic research animals (e.g., vertebrates, insects, nematodes) segregate germline and soma during early embryogenesis. In contrast, some highly regenerative bilaterian (e.g., planarians) and non-bilaterian animals (e.g., hydrozoan cnidarians) retain adult stem cells with both germinal and somatic potentials. As these cells have been studied in only few phyla, their biology and evolution remain mostly enigmatic. Here, we aimed to identify and characterize adult stem cells and their cell lineages in the sea anemone Nematostella vectensis by combining gene expression analysis, immunostainings, and meganuclease-mediated and CRISPR/Cas9-mediated knock-in reporter lines of conserved germline and multipotency genes (e.g., vasa2, piwi1). We found a small population of vasa2+/piwi1+ cells in the gastrodermal folds of juvenile and adult sea anemones that generates germline and a diversity of somatic, mostly proliferative cells. Using a combination of soxB(2) neural progenitor and piwi1 reporter lines, we found that the somatic progeny from vasa2+/piwi1+ cells includes soxB(2)+ neural progenitors. Our results strongly support the existence of an adult Vasa2+/Piwi1+ multipotent stem-like cell population that derives both germline and somatic lineages in Nematostella. The similarities of lineages and gene expression profiles between Nematostella Vasa2+/Piwi1+ stem-like cells and hydrozoan interstitial stem cells support their evolutionary conservation among cnidarians.