Fig. 7. GT hyperplasia of Bmpr1a conditional mutant mice. (A) Brn4-Cre-mediated expression of lacZ was detected in the outermost epithelial layer adjacent to the DUE and the GT surface ectoderm but not in the DUE at 12.5 dpc. (B) lacZ expression was already detected at 10.5 dpc before GT outgrowth in the cloacal regions (within the white arrows). (C) Reduction (80%) of pSMAD1 signals in the mutant was detected at 10.5 dpc before GT formation and more prominently GT at E12.5 dpc (cell number of wild type is shown as 100%). (D,E) Bmpr1a mutant mice displayed augmented GT outgrowth proximodistally. Note that the DUE region of Bmpr1a mutant mice was enlarged compared with that of wild type, as clearly observed by SEM analysis. The arrow indicates the DUE covered with epithelia (D,E, inset). (F,G) Augmented Fgf8 expression in the Bmpr1a mutant mice GT compared with wild type. F also shows non-specific background signals in addition to the distal DUE expression. (H,I) A marked decrease of apoptosis was found in the distal GT region of Bmpr1a mutants. (J,K) GT hyperplasia was prominently observed in Bmpr1a mutant newborns. (A,H,I) Coronal sections; (B,D-G) ventral views; (J,K) lateral views. N.D., not detected. Scale bar: 200 µm in A; 300 µm in B; 600 µm in D,E; 750 µm in F,G; 100 µm in H,I; 950 µm in J,K.