Augmentation of BMP signaling leads to increased levels of cell death and p53 protein in developing nasal cartilage of E12.5 mice and newborns. (A) tdTomato distribution in E12.5 P0-Cre transgenic mice crossed with ROSA-tdTomato Cre reporter mice. The right panel is the tdTomato image merged with DAPI staining, which is shown in blue. (B-D) Frontal sections of E12.5 control, mutant and ca-Bmpr1a:P0-Cre:Bmpr1a+/− (rescue) mice were stained using H&E. Control and rescue mice had comparable nasal septum morphology; however, mutants had shorter nasal septa. lv, lateral ventricle; ns, nasal septum. (E-G) TUNEL assay was performed to detect apoptosis. E12.5 mutants exhibited increased numbers of apoptotic cells shown in green (F). Blue indicates DAPI staining. (H-J) Immunohistochemistry using p53 antibody revealed increased p53 levels in mutant nasal septa (I). (K-P) Frontal sections of newborn controls, type 1 and type 2 mutants were stained using H&E. Boxed areas in K-P are shown at high magnification in Q-V, respectively. (Q-S) TUNEL assay was performed to detect apoptosis. Both type 1 and type 2 newborn mutants exhibited more apoptotic cells, which are shown in green (R,S). (T-V) Immunohistochemistry using p53 antibody revealed increased p53 levels in both mutant nasal septa (U,V). (W) Quantification of TUNEL assay results in newborns. All data are represented as mean±s.d. (n=3); *P<0.01 (Student's t-test). Scale bars: 500 µm in A,B,K,N; 100 µm in E,H,Q,T.