ABSTRACT
Formation of the body axes and the apical termini are fundamental steps during animal development. Here, nuclear β-catenin and canonical Wnt3 have been identified as major players in Hydra, which belongs to the early diverging phylum of cnidaria. However, both molecules have previously been assumed to be part of the same pattern formation system. In this study, we revised this view by combining mathematical modeling with previous and new experimental data demonstrating that they contribute to two largely independent de novo pattern formation systems in Hydra. Notably, β-catenin (possibly in interplay with other Wnts) appeared to act at the whole-body scale contributing to axis formation, whereas Wnt3 was involved in a downstream pathway driving small-scale patterning of the head. These results also suggest that these mechanisms may be more complex in other animals, in which axis and head formation have previously been attributed to a single pattern formation mechanism.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Compared to the previous version of the manuscript, new experiments and simulations of the model have been linked much more intensively, among other things (but not exclusively). This includes, for example, predictive modelling of experiments that were in turn confirmed experimentally.
