Effects of parity on Wnt transcription-factor activities and nuclear β-catenin in basal mammary epithelial cells. (A) Wnt transcription factor LEF1/TCF7 motif activity in basal stem/progenitor cells from parous as compared with virgin control mice, as predicted by MARA . The binding motif of the LEF1/TCF7 transcription factor is shown in color. (B) Representative images of immunostaining for β-catenin in mammary gland sections from age-matched virgin and parous mice in estrus. Arrow, basal mammary epithelial cells with nuclear β-catenin. Arrowhead, basal mammary epithelial cells lacking nuclear β-catenin. Scale bar, 10 μm. (C) Bar graph representing the quantification of nuclear β-catenin in mammary gland sections of virgin and parous mice. Data represent the mean ± SD (virgin mice: n = 3; parous mice: n = 3). P = 0.004 with the two-tailed unpaired Student t test. (D) Transcription-factor activities in basal stem/progenitor cells, predicted on the basis of target gene expression by Ingenuity IPA . Activity is reported as Z scores (positive Z score, upregulation; negative Z score, downregulation) by using a cut-off of linear fold change > 1.5 and P value < 0.05. (E) BioFunctions most strongly downregulated (blue) or upregulated (orange) in basal stem/progenitor cells, as calculated by Ingenuity IPA . The color of the fields represents the Z score; the size of the fields represents the number of genes. A stringent cut-off of linear fold change > 2 and P value < 0.01 was used to minimize the number of false positives.