Fig. 2. Conditional null mutation of Tgfbr2 in the CNC-derived ectomesenchyme does not adversely affect the neural crest migration during early craniofacial development. (A,B) At E11.5, the CNC-derived mesenchyme has populated the region of the developing frontal primordium (arrow). There is no apparent difference in the number of cells between the wild-type and the Tgfbr2^fl/fl;R26R;Wnt1-Cre mutants, suggesting that there is no CNC migration defect prior to frontal bone primordium development. (C,D) Apparent developmental defect of the frontal primordium is observed within the Tgfbr2^fl/fl;R26R;Wnt1-Cre mutant sample when compared with the wild-type control at E13.5. There is a diminished number of CNC-derived cells in the frontal primordium (arrow) of the Tgfbr2^fl/fl;R26R;Wnt1-Cre mutant. Scale bars: 200 µm.