Upon regeneration these molecules behave as expected from our theory: the activity reappears in the region were the regenerating head is expected, a process that requires about 1-2 hours (inserts in the left figure above ). Moreover, ectopic expression of Hy-beta-catenin RNA in Xenopus can induce a secondary embryonic axis, indicating that the crucial pathways for organizer formation are well preserved in evolution.
Although all these genes are expressed in the head region, there are differences in the expression pattern: Hy-beta-catenin and Hy-Tcf (above left) have a somewhat wider distribution. During bud formation, these are distributed over the entire bud in a graded fashion. Later, the high levels become more restricted to the head region. In contrast, Hy-wnt is from the beginning more confined to the surrounding of the opening of the gastric column. Thus, both systems have different wavelength. These different expression patterns suggest that these molecules are not just part of a simple auto regulatory loop.
After dissociation into single cells and re-aggregation, Hydra cells can form complete animals . During this process Hy-beta-cat/Tcf on the one hand and Hy-Wnt on the other behaves differently. Taking cells from the gastric column that don’t express these genes, Hy-beta-cat / Tcf become first active in a homogeneous way. Later, isolated local concentrations emerge that eventually give rise to head formation. In contrast, Hy-Wnt activity emerges directly in very sharp spots that form later the oral opening :