Fig. 5. Expression of pMad in stage 5 embryos. Embryos were stained with the PS1 antibody. (A) Mid stage 5 embryo viewed from the top of the germ disc. (B) Close-up of the same embryo as in A, flat-mounted. Nuclei of germ disc epithelial cells, but not CM cells, at and around the cumulus are stained. Note that the levels of signal are graded in a concentric manner. (C,D) Mid stage 5 embryo double-labeled for pMad (brown) and At.dpp transcripts (purple). C focuses on the surface epithelial cell layer and D on the CM cells. Note that the highest levels of pMad are observed just above the CM cells, expressing At.dpp transcripts.