Gradients and Regulatory Networks of Wnt Signalling in Hydra Pattern Formation

Abstract

The Wnt/β-catenin pathway plays an important role in axis formation and axial patterning during metazoan development. Wnt genes are expressed around the blastopore of prebilaterian and bilaterian embryos and create a gradient of ligands governing the primary oral-aboral body axis. Although this polarised Wnt signalling along a primary body axis is a conserved property of metazoan development, the mechanisms governing localised Wnt expression and secretion are poorly understood. We study these questions in the freshwater polyp Hydra, a classical model system for the analysis of morphogenetic gradients and modelling of de novo pattern formation processes. New data emphasise the importance of gene regulatory networks for the formation of Wnt secreting signalling centres. It is proposed that a twist of transcriptional control and gradient formation was essential for the formation of Wnt signalling centres in metazoan axis formation.