Expérimental
The evolutionary emergence of the primitive gut (called endomesoderm (EM)) in first Metazoa, one of the decisive events that have conditioned the major evolutionary transition leading to the origin of animals, is thought to have been intimately associated to the invagination of primitive multi-cellular tissues (i.e gastrulation) and its differentiation. However, the biochemical cues at the origin of such primitive gut formation remain uncertain. We recently found that hydrodynamic mechanical strains, reminiscent of soft marine flow, trigger tissue gastrulation and inversion via a Myosin-dependent mechanotransductive process, in the metazoan Nematostella vectensis (Cnidaria) and the multi-cellular choanoflagellate Choanoeca flexa (see Figure) considered as the closest living relative to metazoans. These observations suggest that primitive gut emergence in Metazoa may have been initiated by marine mechanical strains in multicellular pre-Metazoa more than 700 million years ago, thanks to Myosin mechanosensitive properties crucial for this evolutionary transition (Farge, Biol. Theory 2013, Bouclet, Brunet et al, Nat Com 2013, Nguyen et al, Front Cell Dev Biol 2022). The project consists in searching for the underlying molecular mechanism of the translation of the mechanical strains into the biochemical signals leading to the Myosin activation involved and conserved in these distinct species from earliest metazoa, beginning in Nematostella embryos.