Module 8: Figure dorsoventral specification
A model for dorsoventral specification in the early Xenopus embryo.
Dorsoventral specification of the Xenopus embryo is determined by the Wnt signalling pathways. Ventral specification is regulated through Wnt5A/11, which acts through a Ca2+ signalling pathway to activate the ventral specification genes. The Wnt8 pathway, which acts through the canonical Wnt pathway, is switched off via a mechanism that may depend upon diacylglycerol (DAG) acting through protein kinase C (PKC). In the dorsal regions, the activity of these two pathways is reversed. The pathway driven by Wnt5A/11 is inactivated, whereas the pathway activated by Wnt8 increases the level of the transcription factor β-catenin, which then switches on the dorsal specification genes.