Essential function of Wnt-4 in mammary gland development downstream of progesterone signaling

Abstract

Female reproductive hormones control mammary gland morphogenesis. In the absence of the progesterone receptor (PR) from the mammary epithelium, ductal side-branching fails to occur. We can overcome this defect by ectopic expression of the protooncogene Wnt-1. Transplantation of mammary epithelia fromWnt-4 ⁻/⁻ mice shows that Wnt-4 has an essential role in side-branching early in pregnancy. PR andWnt-4 mRNAs colocalize to the luminal compartment of the ductal epithelium. Progesterone induces Wnt-4 in mammary epithelial cells and is required for increased Wnt-4 expression during pregnancy. Thus, Wnt signaling is essential in mediating progesterone function during mammary gland morphogenesis.

Keywords

• Mammary gland
• morphogenesis
• Wnt-4 signaling
• side-branching, progesterone function