Confined loss of Ext function only in the Sonic Hedgehog (Shh)-transporting cells suffices to enhance the Shh response in Ext1/2 competent cells. (A): Schematic representations of the experiments. Neuralized embryoid bodies (nEBs) consisting of 1:1 of Shh−/−;Ptch1+/LacZ cells, Shh−/−;Ptch1+/LacZ;Ext1−/− cells, or Shh−/−;Ptch1+/LacZ;Ext2−/− cells were generated to assess Shh distribution and signaling response. (B): Quantification of Shh positive area per mosaic nEB composed of the indicated genotypes. One-way analysis of variance (ANOVA) with post hoc Dunnett’s test; ****, p < .0001. (C, D): The Shh-mediated induction of Olig2 (C) and Isl1/2 (D) per nEB was quantified. One-way ANOVA with post hoc Dunnett’s test; *, p < .05; **, p < .01; ***, p < .001; ****, p < .0001. Abbreviation: ns, not significant.