A wt and two mutant (Pax3Cre;Gmnnflox/flox) E10.5 littermate embryos (mut1,2) are shown to present the range of phenotypes observed at this time. mut2 lacks dorsal and ventral progenitor marker expression, consistent with the degenerated neural tube structure. In comparisons of wt and mut1, (A–D) transverse sections of E10.5 spinal neural tube show no difference in proliferative markers Ki67 and pH3. (E–H) Mutant embryos have diminished expression of the dorsal progenitor marker Atoh1, but not the ventral progenitor marker Nkx2.2. (I–N) Differentiation markers Hb9, Isl1, and, Ncam are decreased in mutant embryos. Arrowheads indicate the notochord for mut2 images. Embryos analyzed for immunohistochemistry (n=5). Scale bar=100 μm.