Fig. 9. Model for epibranchial induction and neurogenesis. Diagram indicating the sequence of placodal specification and neurogenesis within a ganglion, and its induction by an endodermal pouch. Maturation occurs in an anterior to posterior sequence as surface ectoderm becomes specified as placodal tissue that then undergoes neurogenesis. Newly born neurod+ cells (blue) form distally in response to BMPs from a pouch as it contacts the surface. These are then displaced proximally to become neuroblasts (green) that also express phox2b and Hu. They then differentiate, stop expressing neurod (orange) and extend axons toward the hindbrain. gAD, dorsal anterior lateral line; gAV, ventral anterior lateral line; gP, posterior lateral line; gV, trigeminal; gVII, facial (geniculate); gVIII, auditory; gIX, glossopharyngeal (petrosal); gX, vagal (nodose); ot, otic placode; tg, trigeminal.