Fig. 2

The roof plate (RP) loses responsiveness to BMP signaling. a, c In situ hybridization for Bmp4 at the neural crest (NC) and RP stages. b, d Antibody staining for pSMAD1,5,8. Note positive signaling in the dorsal neural tube (NT) at the NC stage (delimited by dotted yellow lines, see “Methods” for definition). In contrast, the definitive RP (dorsal to the dotted yellow lines, see “Methods” for definition) lacks a pSMAD signal yet the domain ventral to the yellow lines containing dorsal interneurons is positive. e, f Dorsal views of whole mounted embryo fragments following dorsally directed electroporations (EP) of BMP-responsive element (BRE)-GFP along with control RFP to monitor electroporation efficiency. Note positive and negative BMP reporter signaling at NC and RP stages, respectively. Embryos were electroporated at either E2 (e–e”) or E3 (f–f”) and analyzed 16 h later. White dashed lines delineate the NT in b and d. C caudal, DI dorsal interneurons, R rostral. Bar in a = 40 μM; b, d = 80 μM; c = 50 μM