Mammary ductal and alveolar development: lesson learned from genetically manipulated mice

The mammary gland has been an area of great interest to developmental biologists for many years because its formation involves many fundamental processes that are central to the development of other organs. Although mammary development has been well described structurally, the molecules and signaling mechanisms that are involved are still largely undefined. For the last several years, intensive effort has been made to understand the molecular mechanisms involved in mammary development. With the recent advances in transgenic and knockout technologies, the ability to delete and/or alter the expression of certain genes in the mouse genome has allowed us to begin to elucidate the mechanisms underlying mammary gland development. In this review, we discuss several mouse models that have provided insight into the molecules and signaling mechanisms that govern ductal development and lobuoloalveolar differentiation in the mammary gland.