Fig. 8. Working model of Nematostella stem cell differentiation.

The presence of a putative multipotent stem cell able to differentiate into germline cells and all cell types of the neuroglandular lineage is implicated by the lineage tracing experiments using stable reporter proteins. The relationship of this cell population with differentiated epithelial cells and retractor/parietal muscle cells is currently uncertain (indicated by dashed arrows and question marks). The expression of nanos2* leading to the germ cell lineage indicates that the gene is expressed in spermatogonia but not expressed in the oogonia; however, nanos2 is indispensable for primordial germ cell formation and remains expressed in gonad-adjacent somatic cell types such as the trophocytes. Gene expression is depicted according to this work and Steger et al. (14).