Figure 6
Latent TGFβ binding protein (Ltbp)1L-LacZ appears at the onset of lumen formation. (A) The 5-bromo-4-chloro-3-indolyl-β-D-galactoside (X-Gal)-stained whole mounts (A, C) and sections counterstained by nuclear fast red (B, D, E) at embryonic day (E) 17.5 (A, B), postnatal day 1 P1 (C, D) and E18.5 (E). Note Ltbp1L-LacZ appears as microlumen form within the mammary sprout (B, D, E arrows). Ltbp1L-LacZ is absent from the bulbous multilayered tips (E, arrowhead). Ltbp1L-LacZ is sustained in the mammary mesenchyme (A, B) and developing smooth muscle cells of the nipple areola (C, D). Scale bars represent distance in microns.