Figure 7. Mathematical modelling of the Noggin4 influence on the anterior-posterior Wnt8 signalling gradient.

During neurulation, Wnt8 diffusing from the posterior regions within the anterior neural plate and interacting there with Frizzled8 forms a gradient of Wnt8 signalling, which is schematically presented by a solid black line within the rectangle standing along the neural plate midline on the schema shown above. Coloured curves within an enlarged version of this rectangle (below) demonstrate the theoretically calculated spatial distribution of the Wnt8/Frizzled8 complex (i.e., Frizzled8 receptor activated by Wnt8 binding) at three concentrations of Noggin4 (wild-type, decreased by Noggin4 MO injections and incresased by Noggin4 mRNA injections) indicated in the inserted table. Three inserted photos illustrate the assumed effects of the corresponding spatial shifts of the Wnt8/Frizzled8 complex arbitrary threshold concentration on the forebrain marker FoxG1 expression. See main text, Supplementary Materials and Methods 4.2 and Fig. 1 for details.