Fig. 7. Inactivation of one copy of the Bmp4 gene in a Grem1-deficient mouse embryo results in formation of two normal kidneys. (A-C) Whole-mount in situ hybridisation to detect Pax2 expression at E14.5. (A) Wild-type Pax2 distribution. (B) The absence of Pax2 expression in a Grem1-deficient embryo is due to the complete renal aplasia at this stage. (C) The Pax2 distribution in kidneys of a Grem1^/; Bmp4^/+ embryo is indistinguishable from a wild-type littermate (A). (D) Gross morphology of the wild-type urogenital system at birth (postnatal day P0). (E) Haematoxylin and Eosin staining of a histological section of a wild-type kidney 30 days after birth (P30). (F) PAS staining reveals the morphology of the medulla (collecting ducts) and cortex regions of a wild-type kidney at about 8 months of age (P250). (G) Gross morphology of the urogenital system of a Grem1^/; Bmp4^/+ mouse at birth (P0). Note that both kidneys are of normal size and shape (compare with D). (H) Haematoxylin and Eosin staining of a kidney section from a Grem1^/; Bmp4^/+ mouse at P30. (I) PAS staining of a kidney from a Grem1^/; Bmp4^/+ mouse at P250. Medulla, cortex and glomeruli appear normal. Bl, bladder; cd, collecting duct; cx, cortex; gl, glomerulus; go, gonad; ki, kidney; md, medulla, tu, tubules.