Figure 8

Dorsal expression of Hoxb4 is preceded by dorsalization of the neural tube by BMP signals. (A-D) Flat-mounted neural tubes from embryos electroporated with BMP4, incubated for 6–8 hours and assayed for Hoxb4 (A) and Msx1 (C). Electroporation of BMP4 results in a ventral expansion of Hoxb4 (A, n = 25/30) and Msx1 (C, n = 14/15) within 6–8 hours. Scale bar; 100 μm. (E-H) Electroporation of Smad6 followed by 24 hours of incubation does not cause any obvious changes in Hoxb4 expression pattern (E, n = 23/25. 2/25 showed down-regulation). Msx1 expression is down-regulated at the electroporated side (G, n = 19/20). Scale bar; 200 μm. (I-L) Electroporation of Smad6 followed by 48 hours of incubation causes down-regulation of both Hoxb4 (I, n = 19/21) and Msx1 (K, n = 18/20). Arrows indicate changes in the expression compared to the contralateral side. (B, D, F, H, J, L) shows electroporated, GFP-positive cells in (A, C, E, G, I, K), respectively. Arrowheads in (A, E, I) show the rhombomere 6/7 boundary (r6/7). Scale bar; 200 μm.