Whole mammary gland transplantations. Whole mammary glands were transplanted into the intrascapular region of recipient mice, and sections were analyzed at L1. In control experiments, whole wild-type mammary gland transplants (B) developed to the same extent as wild-type endogenous glands (A). Although control recipient Dgat1−/− glands failed to develop (C), wild-type whole mammary glands transplanted into the same Dgat1−/− recipients developed normally (D). In the converse experiment, control endogenous Dgat1+/+ glands developed normally (E), whereas Dgat1−/− mammary glands transplanted into the Dgat1+/+ recipients failed to develop (F).