Origin of cranial sensory systems

Cranial placodes are transient ectodermal structures that give rise to key sensory organs and neurons in the vertebrate head. This dissertation investigates the molecular and cellular mechanisms governing the specification and segregation of otic and epibranchial (EB) placodes in zebrafish. Using lineage tracing, live imaging, and functional assays, we show that Pax2a expression levels bias cell fate toward otic or EB identities, with Wnt signaling enforcing otic specification. Continuous Fgf signaling, particularly from Fgf3 and Fgf10a, is required for EB placode maturation, with distinct tissue sources identified for these ligands. These findings provide new insights into sensory organ development and early neural progenitor specification outside the CNS.