Figure 1. Stat3^fl/fl;BLG-Cre⁺ glands show incomplete involution and luminal progenitors have reduced proliferative capacity.

(A) RT-PCR analysis of Stat3 expression in FACS sorted populations of mammary epithelial cells. MRU: mammary repopulating units. (B, C) H&E staining of sections of Stat3^fl/fl;BLG-Cre⁻ and Stat3^fl/fl;BLG-Cre⁺ mammary glands collected at day 5 of the second gestation (B) or four weeks after natural weaning (C). (D) Western blot analysis of four Stat3^fl/fl;BLG-Cre⁻ and five Stat3^fl/fl;BLG-Cre⁺ mammary glands four weeks after natural weaning for the expression or activation of Stat5, Erk, Akt, β-casein and WAP. β-actin was used as a loading control. (E) Immunohistochemistry staining for pStat5 (red) and E-cadherin (green) in mammary gland sections from Stat3^fl/fl;BLG-Cre⁻ and Stat3^fl/fl;BLG-Cre⁺ mice collected four weeks after natural weaning. Nuclei were stained with Hoechst 33342 (blue). (F) Flow cytometry analysis of luminal progenitors isolated from mammary glands of Stat3^fl/fl;BLG-Cre⁻ and Stat3^fl/fl;BLG-Cre⁺ females four weeks after natural weaning. (G) In vitro colony forming analysis performed on CD24⁺ CD49f^hi CD61⁺ luminal progenitor cells sorted from Stat3^fl/fl;BLG-Cre⁻ and Stat3^fl/fl;BLG-Cre⁺ mammary glands. Points represent the value for each mouse and lines depict mean values for each group. p value was determined using Student’s t test, * p<0.05.