Notch ligands and the segregation of germ layers in vertebrates: lateral induction or lateral inhibition?

GARAVAGLIA, MATÍAS J.; SABAJ, DANIELA; FAVAROLO, MARÍA BELÉN; LÓPEZ, SILVIA L.

Buenos Aires

Congreso; Xth Latin American Society for Developmental Biology (LASDB) Meeting.; 2019

Latin American Society for Developmental Biology (LASDB)

The Notch pathway is activated by the interaction of transmembrane receptors (Notch) and ligands (Delta and Jagged families) between neighboring cells. The Delta/Notch pathway has a central role in the induction and specification of mesoderm or endoderm in invertebrates, while in vertebrates, Notch is rather involved in the refinement of boundaries between germ layers, but it is not clear if different Notch ligands participate. Moreover, it is unknown if Notch operates through mechanisms of lateral inhibition or lateral induction in the delimitation of germ layers in vertebrates (Favarolo and López, 2018).We now propose that, at the beginning of gastrulation, notch1 promotes the expression of dll1 in the presumptive mesoderm by lateral induction. In this way, dll1 ensures its uniform expression in the prospective mesoderm. As gastrulation progresses, the expression of dll1 in the presumptive mesoderm activates notch1 in the neighboring cells of the presumptive neuroectoderm, where notch1, on the other hand, represses the expression of dll1. Thus, dll1 self-limits its expression to the presumptive mesoderm by lateral inhibition on the neighboring germ layer.We show that jag1 and dll1 are complementarily expressed during gastrulation in Xenopus, suggesting that both ligands operate in the refinement of boundaries between germ layers.