Figure 1

Suppression of Brca1 results in defective mammary epithelial morphogenesis in vitro and accumulation of luminal progenitor cells in vivo. (a) Brca1 knockdown by siRNA is confirmed in HC11 cells by real-time PCR (top graph). Brca1 mRNA levels were compared in HC11 cells transfected with scrambled (control) and Brca1 siRNA constructs. Bars represent the mean of three independent experiments and error bars represent s.e. Knockdown of Brca1 reduces dome formation in the HC11 in vitro differentiation assay (bottom panel). Dome formation was calculated at day 8 after initiation of the assay and shown here relative to the scrambled control. Error bars represent s.e. (b) Functional disruption of Brca1 impairs prolactin-induced mammary differentiation of SCp2 cells. Differentiation of SCp2 cells transfected with pZeoSV vector (left column) and trBrca1 (right column). Phase contrast images ( × 20 magnification) are shown of SCp2 cells that were grown on matrigel, four days (top row) and six days (middle row) after the addition of lactogenic hormones. H&E-stained sections (bottom row) of cell aggregates at day 6 were photographed using a light microscope at × 200 magnification. Arrows indicate defective morphogenesis. (c) H&E-stained sections of day 1 lactation mammary glands taken from Brca1^Co/Co (left column) and MMTV-Cre Brca1^Co/Co (right column) mice taken at × 40 (top) and × 100 (bottom) magnifications. Arrows indicate defective morphogenesis. (d) Sorted mammary epithelial cells from MMTV-Cre Brca1^Co/Co mice exhibit increased luminal progenitor cells at day 12 of pregnancy. Histograms showing percentage of CD61⁺ cells in the CD29^loCD24⁺ population isolated from virgin or 12.5-day pregnant Brca1^Co/+and MMTV-Cre, Brca1^Co/Co mammary glands (mean±s.e.m. of 3–6 animals per group). *P<0.05 (Student's t-test).