Fig. 4. Brain distortion in SM22-Cre;R26R;Bmpr1a^flox/flox mouse embryos. (A) Whole-mount lacZ staining of an E10.5 WT embryo brain showing blue staining in the forebrain. (B) Collapse of telencephalic vesicles (b arrows) and compressed brains (d) of SM22-Cre;R26R;Bmpr1a^flox/flox versus WT (a,c) embryos at E10.5. H&E-stained cross-sections of WT (e,g,i,k) and mutant (f,h,j,l) head at the levels of the dashed lines in c and d, respectively. Sections 1, 2 and 3 are at levels of the frontonasal processes and section 4 is at the nasal-mandibular level. Panels depicting WT and mutants are of the same magnification. (C) Whole-mount PECAM staining shows unilateral clearing of telancephalic vessels in the WT (a,c) but not the flox/flox (b,d) head at E10.5. The clearing is evident at nasal-mandibular areas of the WT head (e) as opposed to resistance to clearing (arrows) in the mutant (f). TUNEL staining (arrows) on brain sections show less apoptosis in the mutants (h) than WT (g). By TUNEL assay (red) combined with NG2 immunofluorescence (green), no apoptosis was seen in NG2-positive areas in the WT brain sections (i); however, more immunoreactivity was seen in the mutants (j). Panels depicting WT are of the same magnification as their corresponding mutants. Percentage TUNEL-positive (k) and PCNA-positive (l) over total number of cells in nasal-mandibular areas (examined using a 20x objective) of E10.5 WT and SM22-Cre;R26R; Bmpr1a^flox/flox (f/f) mutants. Bars indicate mean±s.e.m. (n=3 in k and n=3-4 in l). ^*P<0.05. Scale bars: 100 µm in Cf,h,j; 200 µm in Bl.