Experimental mouse genetics-- answering fundamental questions about mammary gland biology.

Contemporary gene-targeting techniques now make it possible to alter specific genes in the genome. As a result, a plethora of mouse models have been generated that allow researchers to dissect cell-signaling pathways involved in mammary gland development and in breast cancer. But what have we learned so far? What do these models teach us? This review presents a global picture of how the analyses and comparison of individual knockout mouse models provide important insights into basic mammary gland biology. Particular emphasis is placed upon what is currently known about the signaling pathways involved in the establishment of the mammary ductal tree, and its subsequent proliferation at pregnancy and lactation. In addition to these well-established pathways, we address recent data that describe the role of lesser-known genes in the development of the mammary epithelium.