• AP-2;
  • TFAP2C;
  • mammary;
  • branching morphogenesis;
  • transgenic mice


Extensive development of the mammary gland occurs during puberty, when rising levels of ovarian hormones induce the formation of highly proliferative terminal end buds (TEBs) at the tips of mammary ducts. TEBs consist of an outer layer of cap cells and of inner body cells. TEBs invade the adipose stroma and bifurcate while extending the ducts to generate an arborized ductal network. We show that in murine mammary glands transcription factor AP-2γ is strongly expressed in the cap cell layer and in a subset of body cells of TEBs. To decipher AP-2γ functions during mammary development we generated AP-2γ-deficient mice. Their mammary glands displayed impaired ductal branching and elongation. Cellular proliferation within TEBs was reduced. Although estrogen receptor was expressed, exogenously administered ovarian hormones could not restore normal development. Therefore, AP-2γ is functionally involved in branching morphogenesis of the mammary epithelium, possibly by controlling genetic processes downstream of ovarian hormones. Developmental Dynamics 239:1027–1033, 2010. © 2010 Wiley-Liss, Inc.