Mouse mammary glands at different stages of development show that mSpry1 and 2 are localized in the epithelium of the mammary ducts. Mouse mammary glands at different stages of development show that mSpry1 and 2 are localized in the epithelium of the mammary ducts. A, H&E and in situ staining of mammary glands of 2 weeks, 6 weeks, and 16 weeks female mice. The mSpry2 is highly expressed in developing mammary ducts in 2- and 6-week-old females and seems to be confined specifically to the epithelial lining of the mammary ducts and is absent in the stroma and adipose tissues. The level of expression starts decreasing as the mice reach sexual maturity, as can be evidenced by the lower levels apparent at 16 weeks. B, H&E and in situ staining of mammary glands of mice undergoing pregnancy, lactation, and involution. In pregnant mice, the level of mSpry2 becomes elevated again when it is highly expressed in the actively developing alveoli. The mSpry2 expression then diminishes in the lactating female and seems to be totally absent during the involution phase. C, the hSpry2 sense control probe for mSpry hybridized to a section of the mammary gland from a pregnant mouse, demonstrating a lack of nonspecific staining. D, in situ staining for mSpry2 (left) and mSpry1 (right), respectively, showing colocalization of the two Spry isoforms, specifically in the luminal epithelial cells of the mammary ducts of a pregnant mouse. Ting Ling Lo et al. Cancer Res 2004;64:6127-6136 ©2004 by American Association for Cancer Research