Levels of BMP-Smad signaling, cell death and proliferation were examined by immunohistochemistry. (A) Frontal sections (eye levels) of E18.5 calvaria from five genotypes of mice that include the presumptive anterior frontal sutures were used for immunodetection of pSmad1/5/9 (green), cell death (TUNEL assay, red)) and Ki67 (green), respectively. White brackets indicate a space between pSmad1/5/9 positive domains. (B, C) Quantification of TUNEL positive and Ki67 positive cells, respectively (n=3). *, p<0.05, **, p<0.001. Scale bars: 100 µm.