Fig. 7. Phox2b expression in the dmnX and nucleus ambiguus (NA) of adult wild-type (A,B,F,G) and homozygous Nkx2.9 mutant (C,D,H,I) mice. Nissl-stained transverse sections through hindbrains (A,C,F,H) reveal normal morphology of the dmnX (A,C) and Nucleus ambiguus (F,H). (B,D,G,I) Parallel sections immunostained with Phox2b-specific antibody. Note the drastically reduced number of Phox2b-positive cells in the NA (G,I) but not in the dmnX (B,D). Graphs illustrate the ratio of Nissl-positive cell counts (total) and the ratio of Phox2b-positive cells (Phox2b+) from mutants versus wild-type animals in dmnX (E) and NA (J). Each column represents the mean of five slides counted from three individual animals for each genotype.