(A) Barhl1 is expressed in the dorsal-most neuroblast population of the caudal rhombic lip. Barhl1 expression is detected in only a few cells in the dorsal hindbrain of Bmpr double knockout mutants (B). At 16.5 dpc, Barhl1-positive cells were detected in the external cuneate (ECu; Panel C), lateral reticular (LRt; Panel C), reticulotegmental (RtTg; Panel E) and pontine gray nuclei (Pn; Panel G). These cells were largely missing or drastically reduced in the Bmpr mutant (D, F, H). All panels in the figure show in situ hybridization, although there is some variability in the precipitate generated by the color reaction chemistry. Scale bar: A (for A, B), 50 μm; C (for C-H), 200 μm.