Figure 4

Retinoic acid and hoxb1b act independently to activate hoxb1a transcription. 19hpf wild type (A, C, E) or hoxb1b^−/−(B, D, F) embryos were treated with DMSO (control; A, B), 10uM DEAB (C, D) or 100 nM RA (E, F) and assayed by in situ hybridization for expression of hoxb1a in r4 (blue stain in A-F) and krox20 in r3/r5 (red stain in A-F). All embryos are flat mounted in dorsal view with anterior to the top.