Fig. 3. Normal levels of apoptosis in frontal bone rudiments of Msx2 mutant embryos. We performed TUNEL stains on cross-sections through the presumptive frontal bone of Msx2^–/– and wild-type littermate embryos at E11.5 (A,B) and E12.5 (C-F). The broken lines indicate the approximate area occupied by the frontal bone skeletogenic mesenchyme. The squares in C,D demarcate areas shown at higher magnification in E and F. Note that at E11.5, no TUNEL-positive cells (green) were evident in the presumptive frontal bones of either mutant or wild-type embryos. A few positive cells were evident elsewhere in the section (e.g. arrowhead). At E12.5, there were near-equal numbers of apoptotic cells in frontal bone mesenchyme (stained green, arrowheads) of mutant and wild-type embryos. ep, epithelium; ch, cerebral hemisphere. Scale bars: 200 µm in B,D; 50 µm in F.

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