AXIN2 and infection: To quantify infection levels, Wnt3a overexpression, and to examine whether infection and expression was restricted to the FNP, we quantified the level of expression of WNT3A, GAG, and AXIN2 indicators of Wnt signaling in neural crest cells (Yu et al., 2007) in the mesenchyme and ectoderm together derived from the FNP from four WT and four RCAS-Wnt3a samples (Supplementary Figure 1D).