Figure 4.
Coexpression of PR and Wnt-4 mRNAs in the luminal mammary epithelium. Mammary glands were harvested from a virgin adult female mouse and from mice at days 4 and 8 of pregnancy. The glands were processed for in situ hybridization; adjacent sections were hybridized with 35S-labeled antisense cRNA probes for PR or Wnt-4 and exposed for 7 days. Hematoxylin- and eosin-stained sections are shown next to the corresponding dark-field exposures. (Top) Coordinated induction of PR and Wnt-4 mRNAs during pregnancy. Low magnification (bar, 150 μm) of mammary gland showing increased signal intensity for both PR and Wnt-4 mRNAs in the ductal epithelium at 4 days of pregnancy vs. virgin. (Bottom) Colocalization of PR and Wnt-4 mRNA expression in the mammary luminal epithelium. High magnification (bar, 75 μm) of selections from mammary glands at days 4 and 8 of pregnancy showing that both PR and Wnt-4 mRNA expression localizes to the luminal epithelium (LE) and is absent from the myoepithelium (ME). Light green areas represent the dense fibrous stroma surrounding the mammary ducts.