Fig. 1

Fig. 1 Neural Patterning in bromi Mutants
(A) Spinal neural tubes of E10.5 wild-type (WT) and bromi mutants immunostained for markers of neural identity (in red, DAPI in blue). bromi mutant neural tubes lacked the floor plate, marked by Shh and FoxA2, although the notochord (arrowheads) expressed Shh normally. Nkx2.2⁺ p3 cells were inappropriately positioned in the mutant ventral midline and reduced in number. The Pax6⁺ and HB9⁺ (motor neuron) domains, which are supported by intermediate, but not high, levels of Shh, ectopically expanded into the most ventral regions in the mutants. The ventral limit of the Pax7⁺ domain, set by low levels of Shh signaling, was not affected in bromi mutants.
(B) X-gal staining of E10.5 neural tubes from WT and bromi embryos heterozygous for the Ptch1-LacZ insertion. Ptch1-LacZ is expressed in a ventral-to-dorsal gradient in response to Shh. Expression in the ventral one-third of the bromi mutant neural tubes (n = 3) was consistently weaker compared with that of WT.