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Figure 1 | Breast Cancer Research

Figure 1

From: Identification of signaling pathways in early mammary gland development by mouse genetics

Figure 1

Genetic analysis of prenatal mammary gland development. (a) Between embryonic days (E) 11.5 and 13.5 the mammary anlagen develops from a small placode contiguous with the ectoderm into a bud that invaginates the dermal mesenchyme (light gray). Rapid cell proliferation at the base of the bud leads to the formation of an elongated duct that grows toward the fat pad (intermediate gray shading) on embryonic day 16.5. The mammary mesenchyme (dark shading), which is induced by parathyroid hormone-related protein (PTHrP) signals emanating from the mammary epithelium, abuts the placode and bud and contributes to the formation of the nipple. (b) The stages of arrest in mammary gland development caused by the different gene deletion mutants are indicated by bars. b, bud; ec, ectoderm; ep, epidermis; n, nipple; p, placode; ps, primary sprout; FGF, fobroblast growth factor.

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