Fig. 4. Loss of Tgfbr2 within the CNC-derived mesenchyme does not affect cell survival during frontal bone development. (A) At E13.5, there is no detectable apoptotic activity within the frontal bone primordium in the wild-type sample. (B) In the Tgfbr2^fl/fl;Wnt1-Cre mutant sample, there is no increase in cell death compared with wild type within the frontal primordium. (C) Sporadic apoptotic signals are present adjacent to the frontal primordium in the control (arrows). (D) Similarly, a few apoptotic signals (arrows) are seen in the frontal primordium in the Tgfbr2^fl/fl;Wnt1-Cre mutant, as seen in C, suggesting that loss of TGFß signaling does not cause a change in apoptotic activity within the CNC-derived frontal mesenchyme. Scale bar: 100 µm.