Figure 1. Lineage tracing of adipocytes in the mammary gland during reproduction.

(A) Experimental design: 10-week old AdipoChaser-LacZ female mice were put on a doxycycline chow diet for 7 days to ensure that LacZ expression is turned on in all mature adipocytes. After doxycycline treatment, mice were switched back to regular chow diet for a week to ensure washout of doxycycline. Thereafter, mice were kept as virgins or bred with male mice to undergo pregnancy and lactation. LacZ staining is performed at the indicated time points. (B-E) Representative β-gal staining of the mammary gland from female AdipoChaser-LacZ mice. (B) Virgin female: 7 weeks after doxycycline diet treatment. (C) During pregnancy: female mice were pregnant for 18 days. (D) During lactation: female mice were lactating pups at day 1, day 3 and day 10. (E) Involution: pups were taken away from lactating female mice at L10 for 2 days, 4 days, two weeks or 2 months (56 days) (F) Experimental design: 10-week old AdipoChaser-LacZ female mice were treated with doxycycline chow diet to label all mature adipocytes as described in panel A. Mice were then bred with male mice to undergo pregnancy and lactation for two rounds. LacZ staining is performed 7 days after weaning. (G) Representative β-gal staining of the mammary gland from female AdipoChaser-LacZ mice, after two rounds of lactations. n = 3–5 mice per group. Scale bar: 100 μm. This experiment is representative of three independent experiments.