Fig. 4. Mammary buds 1, 2, 3 and 5 are not detected in the Fgfr2b–/– embryos. Whole-mount in situ hybridization on Fgfr2b–/– and wild-type embryos at E12.5 and E13 with dig-labeled antisense riboprobe for Lef1 (A-H) and cell death analysis (I,J). B, D, F, H are high magnification views of the boxed areas in A, C, E and G, respectively. (A) Lef1 expression at E12.5 in wild-type embryo showing expression in the epithelium of the mammary bud. Note that only three mammary buds, located between the forelimb and hindlimbs, are visible. Mammary buds 1 and 5 are located behind the limbs. (B) Mammary bud 4. (C) Lef1 expression at E12.5 in Fgfr2b–/– embryo showing that only one mammary bud is detected. (E) Lef1 expression at E13 in wild-type embryo showing expression in the epithelium of the mammary bud. (F) Mammary bud 4. (G) Lef1 expression in the Fgfr2b–/– embryo is no longer detected in the area corresponding to the mammary bud 4 (dotted box). (I) Section of normal mammary bud at E12.5 showing a complete absence of cells stained by the TUNEL method. (J) Fgfr2b–/– mammary bud at E12.5 showing a high number of individual apoptotic cells labeled in the epithelium. Scale bar, A, 875 µm; B, 160 µm; C, 875 µm; D, 160 µm; E, 1220 µm; F, 235 µm; G, 1220 µm; H, 235 µm; I, J, 10 µm.
