Figure 7. Model for cloacal septation.

(A) E11.5 Bmp7^lacZ/+ embryo stained with X-gal. Position of the cloacal section depicted in (B) is indicated with dashed line. (B) Signaling by Bmp7 from the URM (blue) activates JNK in the cloacal endoderm. Bmp7/JNK activity promotes cell survival, proliferation and apical-basal polarity of cell divisions in the endoderm (red arrows) which facilitates topological separation of the rectum and urethra. Apical-basal polarity of cell divisions is required for epithelial differentiation and expression of K14.