Fig. 6.

Sonic hedgehog is required for aPPR induction. CMFDA-labelled (green fluorescence) pME was grafted together with cyclopamine-coated beads into the extraembryonic region of chick hosts. After 16 h, Six1 is induced (A-A″; n=7/9 induced; no significant difference to controls, goodness of fit test). By contrast, Six3 (B-B″; 4/13 induced compared with 8/11 in controls; P=0.00166, goodness of fit test; see Fig. 4E′) and Otx2 (C-C″; 0/4 induced compared with 3/3 in controls; P=0.024, two-tailed goodness of fit test; see Fig. S11) induction is lost. Arrowheads indicate grafts; asterisks indicate beads. ISH, in situ hybridisation.