Figure 2

Latent TGFβ binding protein (Ltbp)1L-LacZ appears early in embryonic mammary development. The 5-bromo-4-chloro-3-indolyl-β-D-galactoside (X-Gal)-stained embryonic day (E) 10.5 embryo (A) and vibratome section (B) show a broad stripe of Ltbp1L-LacZ (blue stain) that localizes to viscera (black arrow). Faint staining (red arrow) is seen at the dorsal border of the mammary line (asterisk) overlying the somitic tips (S). (C) X-Gal-stained E12.0 to E12.5 embryos show reporter expression in a streak along the forelimb axilla (white arrow) and surrounding placodes 1 to 3 (red arrows). (D) Nuclear fast red-counterstained section of the same region shows a gradient of Ltbp1L-LacZ in the mesenchyme (white arrow) oriented towards mammary gland 1 (MG1). F = forelimb. Scale bars represent distance in microns.