Fig. 1. Expression patterns of Slit2 and Slit3 during mammary gland development. (A) Schematic of an EB with subtending duct. (B,C) SLIT2 immunostaining on (B) +/+ and (C) Slit2^-/- EBs. (D,E) GFP immunostaining on (D) Slit2^-/- and (E) +/+ EBs. (F,G) GFP immunostaining on (F) Slit2^-/- and (G) +/+ ducts. (H,I) Slit3^-/- outgrowth stained for ß-galactosidase activity. (H) Slit3 expression in mature virgin duct. (I) Slit3 expression in aveoli during pregnancy. Arrowheads indicate examples of positively stained cells in the cap cell layer of the EB (B,D) and in the MEC layer of the duct (F,H). Arrows indicates examples of positively stained cells in the LEC compartment of the EB (D) and duct (F,H). L, lumen. Scale bar: 20 µm.