Fig 2

a) schematic illustration of the experimental procedure: 150ng mRNA injection of β-catenin effector Gsk3β into one cell at the eight blastomere stage. At sphere stage (prior induction of Wnt ligand expression), embryos were subjected to an image-based approach to analyse the distribution of cell clones in the animal tissue. b) expression of Gsk3β-GFP (Wnt-OFF) leads to a dispersed clone at the sphere stage. c) However, expression of dominant-negative Gsk3β-GFP (Gsk3β-DN-GFP; Wnt-ON) leads to clustering of the clonal cells. d) Gsk3β-DN expressing cells (Wnt-ON) show large clusters: demonstrated by an increased cluster surface and a reduced number of total clusters/cells compare to cells expressing WT Gsk3β (Wnt-OFF). The expression levels of Gsk3β and Gsk3β-DN are kept at a similar level shown by comparable total GFP-fluorescence in the clones. e)-g), embryos were injected with the indicated constructs and subjected to in situ hybridization against pax6a at 26hpf. The yellow dotted line illustrates the position of the neural plate boundaries. Insets show expression of the GFP tagged constructs prior fixation. h)-j), schematics illustrate the posterior shift of the borders after the reduction of β-catenin activity in the neural plate and the disruption of the boundaries after clonal decrease of β-catenin activity.