Emmanuel Haillot

Abstract Reaggregated early gastrula cells (“gastruloids”) of the sea anemone Nematostella vectensis are able to regenerate into whole polyps within a few days. However, the cellular and molecular mechanisms underlying restoration of body axis and germ layers remains largely unknown. Here, we show that mesodermal cells sort to the periphery of the gastruloid, where they form cell clusters with hitchhiking endodermal cells.

Abstract The Bone Morphogenetic Protein (BMP) pathway is the ancestral signalling system patterning the dorsoventral axis in bilaterally symmetrical animals. However, in Spiralia, a large bilaterian clade including molluscs and annelids, BMP’s axial function varies across species, obscuring the ancestral developmental role of this pathway. Here, we study four annelid species to demonstrate that BMP is ancestrally downstream of ERK1/2 and promotes dorsoventral development in Annelida.

Abstract Cnidaria are typically considered diploblastic (i.e. consisting of two germ layers) in contrast to their triploblastic sister clade, the Bilateria. However, a recent study suggested that sea anemones and other cnidarians have three segregated germ layer identities, corresponding to the bilaterian germ layers (1). Here, we investigated, how the three germ layer identities are specified during early development of the sea anemone Nematostella vectensis.