Fig. 8. DM apoptosis in normal embryos and after early Gdf7-mediated ablation. Fluorescent TUNEL assays (TUNEL, green; nuclei, blue; red blood cells, yellow-orange) on E9.5-11.5 ACTBCre;Gdf7DTA 10µm coronal cryosections. Semi-serial sections are 20-90 µm (A-F) or 120-250 µm (G-R) apart. (A-F) E9.5 studies. TUNEL labeling localizes to the midline region (neuroepithelium and overlying tissues) in mutants and controls. The increased labeling in mutants is consistent with enhanced apoptosis caused by DTA delivery. (G-L) E10.5 studies. Apoptosis in mutants is no longer elevated, but remains localized to the anterior midline, as seen in controls (G,J). In mutants, significant apoptosis is absent caudally where the posterior tCPe anlagen should reside (H,I). The normal posterior tCPe anlagen also displays negligible apoptosis (K,L). (M-R) E11.5 studies. Similar to the E10.5 findings, apoptosis is present at low levels in anterior midline of mutant embryos (M), while posterior levels show little to no apoptosis (N,O). In normal E11.5 embryos, the anterior tCPe demonstrates significant apoptosis (P), while the posterior tCPe does not (Q,R). Similar findings were seen in at least two embryos from each group/stage combination. Arrowheads designate TUNEL-positive regions; arrows designate the definitive tCPe or its anlagen. Scale bars: in F, 0.1 mm for A-F; in R, 0.1 mm for G-R.