Fig. 6. Post-transcriptional regulation of Hoxb4. (A-D) In situ hybridisation for Hoxb4. Transcripts were present in so7-13 (black arrowheads) but not in more posterior somites. By contrast, Hoxb4 was expressed throughout the neural tube posterior to the r6/7 boundary (white arrowhead). (D) Strong staining was seen in the tailbud (white arrow). (E-H) Whole-mount immunostaining for Hoxb4. Protein was detected in so7-13 and in the posterior hindbrain (E,F), but was absent from posterior neural tube and somites (G). (H) Protein was not expressed in the tailbud (black arrow). (I-J) Transverse section of embryos subjected to in situ hybridisation for Hoxb4 (I,J) or immunostaining for Hoxb4 (K,L). (I) Transcripts were widely distributed at forelimb level with relatively high levels in the dorsal neural tube (white arrowhead) and dermomyotome (white arrows). (J) At posterior levels transcripts were expressed throughout the neural tube but not in the adjacent somites. (K) At forelimb level, Hoxb4 protein was not detected in the neural tube but was expressed in adjacent tissue with a high level in the dermomyotome (white arrows). (L) In the posterior embryo, protein was detectable in neither somites nor neural tube, but was seen in the notochord (black arrow) and the mesonephric ducts (black arrowheads). (M-O) In situ hybridisation of a lacZ probe to a transgenic embryo carrying construct CBb4Z. The pattern was identical to that seen with X-gal staining (Fig. 3I,J), with strong expression in all somites posterior to so7 (black arrowhead) and in the tailbud (white arrow). (P) X-gal staining of a 10.5 dpc transgenic embryo carrying construct b4ZCBpA. Strong staining was seen only in so7-13 (black arrowheads). (Q) Structure of construct b4ZCBpA [construct 6 (Whiting et al., 1991)]. This schematic follows the format used in Fig. 1.