Fig. 3. Fgfr2, Fgf7 and Fgf10 expression in the mammary buds between E10.5 and E15.5. Section and whole-mount in situ hybridization using ³⁵S-labeled and dig-labeled antisense riboprobes for Fgfr2, Fgf7 and Fgf10. (A) Fgfr2 expression at E11.5 showing a high expression in the epidermis and in the epithelium of the mammary bud (arrowhead). (B) Fgfr2 expression at E15.5 showing a high expression in the basal layer of the epidermis and in the epithelium of the mammary bud. (C) Fgf10 expression at E10.5. Note the expression of Fgf10 between the fore- and hindlimb (between the two black arrows) corresponding to the area were the mammary line is forming. Fgf10 is also detected in the progress zone of the limbs. (D) High magnification of C showing Fgf10 expression as a dotted line (between the 2 arrows). Double headed arrow indicates the position of section in E. (E) Vibratome cross section (40 µm) between the fore- and hindlimb of the embryo shown in (C). Fgf10 is detected in the most ventral part of the somites. (F) High magnification of the boxed area in E showing Fgf10 expression in the epithelial part of the dermamyotome. (G) No expression of Fgf10 is detected in the mammary bud at E11.5. (H) Fgf10 expression at E15.5. Note the expression in the mammary fat pad precursor surrounding the mammary bud and in the mesenchyme of the hair follicles. (I) Fgf7 expression at E12.5. Note the high expression in the mesenchyme surrounding the epithelial bud. (J) Fgf7 expression at E15.5. Note the expression in the fat pad precursor. dm, dermamyotome; e, epithelium; fl, forelimb; fp, fat pad precursor; hf, hair follicles; hl, hindlimb; int, intestine; m, mesenchyme; my, myotome; nt, neural tube; mm, mammary mesenchyme; so, somites. Scale bar, A,B, 8 µm; C, 430 µm; D, 210 µm; E, 130 µm; F, 32 µm; G-J, 10 µm.