Fig. 4. Loss of precursors of noradrenergic visceral sensory interneurons is associated with the expansion of neighboring interneurons in r5 and r4. Transverse sections through r5 and r4 of E11.5 control (A,C), Hoxa3^-/-b3^-/- (B) and Hoxb1^-/- (D) embryos. The co-expression (yellow) of Phox2b (green) and Lmx1b (red) among noradrenergic precursors is eliminated in the dorsal hindbrain of Hoxa3^-/-b3^-/- and Hoxb1^-/- embryos. The intermediate column of Phox2b and the more ventral population of Lmx1b-expressing cells appear unaffected in the Hox mutant embryos. The domain of Lim1/2 (blue, bracket) expression has expanded in both Hox mutant embryos compared with controls. Comparison of transverse sections at comparable DV axial levels through r3 of an E11.5 control embryo (E-G) with r5 and r4 Hoxa3^-/-b3^-/- and Hoxb1^-/- mutant embryos (B,D) show similar expression patterns of Phox2b, Lmx1b and Lim1/2.