Abstract
Formation of the body axes and the subsequent formation of the apical termini are two fundamental steps during animal development. In Hydra, nuclear β-Catenin and canonical HyWnt3 were identified as major players active in both processes. Based on molecular knowledge of canonical Wnt signaling directly linking nuclear β-Catenin and HyWnt3 activity, it was frequently assumed that de novo axis formation and the head formation were part of the same pattern formation system. In this work, combining new model simulations with available experimental results, we demonstrate that nuclear β-Catenin and HyWnt3 most likely contribute to two separate de novo pattern formation systems in Hydra, organizing development and differentiation on two different spatial scales. In particular, our results suggest that the nuclear β-Catenin acts on the scale of the whole body, controlling axis formation, whereas canonical HyWnt3 signaling is involved in a downstream pathway responsible for small-scale patterning of the head. Consequently, also in other animals where axis formation was ascribed to canonical Wnt signaling, the underlying mechanisms may be more complex than previously assumed.
Competing Interest Statement
The authors have declared no competing interest.
