Figure 10. Expression and modulation of Gli1-LacZ in the adult nipple during the pregnancy cycle.

Gli1-LacZ expression is visible at the neck of the mammary sprout (red arrow) in skin whole-mounts of E18.5 Gli1^lzki/+ embryos at low (A) and higher power (A’). Histological section through the sprout shows expression of Gli1-LacZ within the stroma (red arrow) surrounding the sprout (black arrow) underneath the nipple sheath (black arrowheads) at low (B) and higher power (B’). Gli1-lacZ is expressed within the dermal component but not the epithelium in virgin (C), mid pregnant (D), lactating (E) and involuting (F) nipples. Immunohistochemistry for desmin (G, J), SMA (H, K) and vimentin (I, L) on serial sections of a 15.5 day pregnant nipple demonstrated that Gli1-lacZ was expressed in both smooth muscle cells and fibroblasts but not myofibroblasts. Gli1-lacZ was also found near and surrounding peripherin positive nerve tracts (M) and both Von Willebrand positive vessels (N).