Fig. 10. Model depicting proposed cell autonomous and non-autonomous roles for AP2 proteins in NCC development. Illustrations of transverse sections depicting early migratory stages of NCCs (A) and later interactions within the pharyngeal primordia (B). (A) Initially, tfap2a acts autonomously within NCCs to regulate hoxa2, dlx2 and kit expression. (B) Later, tfap2a and tfap2b act together in the surface ectoderm (blue) to regulate Fgf8 and possibly other Fgfs that activate sef expression and control cartilage development, together with Fgf3 signaling from the pharyngeal endoderm (yellow).