Figure 2.

E-cadherin is required at multiple stages of mammary epithelial development. (A) Mammary pubertal branching morphogenesis initiates at approximately 3 weeks postnatal. A stratified terminal end bud (TEB) leads the elongation front, and a full ductal network forms over 7 weeks. During pregnancy, lactogenic hormones induce the ductal epithelium to form specialized structures called alveoli that mature to secrete milk during lactation. Different genetic approaches have been used to test the consequences of E-cadherin loss during distinct stages of development. (B) E-cadherin is required for branching morphogenesis (Shamir et al., 2014). E-cadherin⁻ cells (green) within transplanted genetic mosaic epithelium are excluded from a ductal network elaborated exclusively by E-cadherin⁺ cells. (C) E-cadherin is required for maintenance of epithelial architecture (Shamir et al., 2014). E-cadherin⁻ cells (green) are extruded apically and basally from mature E-cadherin⁺ epithelial ducts. (D) E-cadherin is required for terminal differentiation and cell survival of alveoli in the lactating gland (Boussadia et al., 2002). E-cadherin loss induces lobuloalveolar collapse and massive apoptosis.