Fig. 6.

Wnt/β-catenin inhibition delays but does not inhibit T/Bra::GFP expression. (A,B) T/Bra::GFP gastruloids stimulated with a pulse of Chi (48-72 h AA) following pre-treatment with vehicle IWP2, XAV939, DKK or Wnt3a (n=14 per condition). Fluorescence traces (A) and heatmaps of the data (B) are shown. Blocking secretion of Wnt proteins with IWP2 effectively abolishes T/Bra::GFP expression until 96 h AA, whereby highly heterogeneous expression is observed. Interestingly, the pulse of Chi can partially rescue T/Bra::GFP expression at 72 h following XAV939 pre-treatment, indicating the requirement for Wnt protein secretion in maintenance of expression. Wnt3a pre-treatment reduces the heterogeneity of the response, better defines the pole of expression and maintains high T/Bra expression for longer than controls (see Figs S7 and S8 for further details and statistical analysis).