Inter-rhombomeric interactions reveal roles for fibroblast growth factors signaling in segmental regulation of EphA4 expression.

We show that r2 and r4 function as temporally dynamic signaling centers in the early patterning of adjacent hindbrain segments and this activity is dependent upon the FGF pathway. These results reveal that inter-rhombomeric signaling is a conserved feature of the regulatory networks that control the specification of individual rhombomere identities in vertebrate hindbrain segmentation. However, the timing of when restricted domains of FGF signaling are coupled to formation of r4 may vary between the species.