Fig. 3.

Expansion of Blimp1⁺ luminal cells in response to hormone treatment. (A) Wild-type and Prdm1^{Cre.IRES.nLacZ} 10-week-old virgin mice were ovariectomized, allowed to recover for 10 days (d) and injected over 6 days with a cocktail of 17β-oestradiol and progesterone (E2+Pg) or mineral oil as a control. Mammary glands were recovered for analysis 7 days later. (B) Whole-mount Carmine staining and Blimp1 immunostaining reveal mammary gland expansion and enhanced Blimp1 expression in response to E2+Pg treatment. Arrowheads indicate the formation of alveolar buds (images representative from two independent experiments; n=5 mice per treatment). (C) X-gal-stained whole-mount and tissue sections of control (oil) or E2+Pg-treated Prdm1^{Cre.IRES.nLacZ} mammary glands. Sections were counterstained with Nuclear Fast Red. Arrows indicate increased numbers of Blimp1-lacZ⁺ cells in the alveolar buds (images representative from two independent experiments; n=5 mice per treatment). Insets in B,C show high-magnification images of the boxed areas. (D) RANKL treatment results in significantly increased numbers of Blimp1-lacZ⁺ cells. Day 6 3D MECs from Prdm1^{Cre.IRES.nLacZ} P15.5-P16.5 females were treated with RANKL (24 h or 48 h) prior to staining. (E) Percentage of Blimp1-lacZ⁺ acini in control versus RANKL-treated cultures (control: n=30 acini; RANKL 24 h: n=30 acini; RANKL 48 h: n=30). Error bars represent s.e.m. ***P<0.001. Scale bars: 50 μm.