Expression of hindbrain boundary markers is regulated by FGF3

Compartment boundaries act as organizing centers that segregate adjacent areas into domains of gene expression and regulation, and control their distinct fates via the secretion of signalling factors. During hindbrain development, a specialized cell‐population forms boundaries between rhombomeres. These boundary cells demonstrate unique morphological properties and express multiple genes that differs them from intra‐rhombomeric cells. Yet, little is known regarding the mechanisms that controls the expression or function of these boundary markers. Multiple components of the FGF signaling system, including ligands, receptors, downstream effectors as well as proteoglycans are shown to localize to boundary cells in the chick hindbrain. These patterns raise the possibility that FGF signaling plays a role in regulating boundary properties. We provide evidence to the role of FGF signaling, particularly the boundary‐derived FGF3, in regulating the expression of multiple markers at hindbrain boundaries. These findings enable further characterization of the unique boundary‐cell population, and expose a new function for FGFs as regulators of boundary‐gene expression in the chick hindbrain.