A maternal dorsoventral prepattern revealed by an asymmetric distribution of ventralizing molecules before fertilization in .

The establishment of the embryonic dorsoventral axis in occurs when the radial symmetry around the egg's animal-vegetal axis is broken to give rise to the typical symmetry of Bilaterians. We have previously shown that the Notch1 protein is ventrally enriched during early embryogenesis in and zebrafish and exerts ventralizing activity through β-Catenin destabilization and the positive regulation of ventral center genes in . These findings led us to further investigate when these asymmetries arise.

Segregation of brain and organizer precursors is differentially regulated by Nodal signaling at blastula stage.

The blastula Chordin- and Noggin-expressing (BCNE) center comprises animal-dorsal and marginal-dorsal cells of the amphibian blastula and contains the precursors of the brain and the gastrula organizer. Previous findings suggested that the BCNE behaves as a homogeneous cell population that only depends on nuclear β-catenin activity but does not require Nodal and later segregates into its descendants during gastrulation. In contrast to previous findings, in this work, we show that the BCNE does not behave as a homogeneous cell population in response to Nodal antagonists.

Notch1 is asymmetrically distributed from the beginning of embryogenesis and controls the ventral center.

Based on functional evidence, we have previously demonstrated that early ventral Notch1 activity restricts dorsoanterior development in We found that Notch1 has ventralizing properties and abolishes the dorsalizing activity of β-catenin by reducing its steady state levels, in a process that does not require β-catenin phosphorylation by glycogen synthase kinase 3β. In the present work, we demonstrate that Notch1 mRNA and protein are enriched in the ventral region from the beginning of embryogenesis in This is the earliest sign of ventral development, preceding the localized expression of , and Ventx genes in the ventral center and the dorsal accumulation of nuclear β-catenin. Knockdown experiments indicate that Notch1 is necessary for the normal expression of genes essential for ventral-posterior development These results indicate that during early embryogenesis ventrally located Notch1 promotes the development of the ventral center.

FoxA4 favours notochord formation by inhibiting contiguous mesodermal fates and restricts anterior neural development in Xenopus embryos.

In vertebrates, the embryonic dorsal midline is a crucial signalling centre that patterns the surrounding tissues during development. Members of the FoxA subfamily of transcription factors are expressed in the structures that compose this centre. Foxa2 is essential for dorsal midline development in mammals, since knock-out mouse embryos lack a definitive node, notochord and floor plate.