Genetic manipulation of the mammary gland by transplantation

Mammary epithelium can be reconstituted in vivo by transplanting fragments of mammary epithelium, or suspensions of mammary epithelial cells, into the 'cleared' mammary fat pad of a syngeneic recipient mouse. A 'cleared' mammary fat pad is one from which the natural epithelium has been removed at 3 weeks of age. Genes can be introduced into the epithelium before transplantation using retrovirus vectors, or the epithelium can be taken from a knockout mouse [1]. The applications of transplantation, and its advantages and disadvantages compared with transgenesis will be surveyed, including the ability to use hormone-insensitive promoters; to introduce genes into clones of cells rather than whole tissues; the ease of studying early preneoplastic change; and the use of transplantation with transgenic knockouts, to rescue embryonic lethals and to distinguish systemic from local effects [2].