Fig. 1

Loss of β1-integrin leads to reduced organoid and luminal progenitor populations. a Primary mammary epithelial cells (MECs) were isolated from β1-integrin^fxfx;CreESR mice and cultured as single cells to form organoids in the absence or presence of 4-hydroxytamoxifen (4-OHT). Gene expression levels were quantified using qRT-PCR. b Immunofluorescence staining of β1-integrin^fxfx cells cultured on collagen-coated coverslips for 3 days in the absence or presence of 4-OHT and then stained with antibodies against β1-integrin and 4′,6-diamidino-2-phenylindole as counterstain. Scale bar = 50 μm. c Representative images of organoid cultures on culture day 10. Spheres formed in the absence of 4-OHT; however, no spheres were present in cultures treated with 4-OHT, leading to the genetic deletion of β1-integrin. Scale bar = 500 μm. d Percentage of organoid-forming cells within β1-integrin^fxfx cells with or without 4-OHT (n = 4). Error bars = SEM (Student’s t test for paired samples). e Basal, total luminal, luminal progenitor and differentiated luminal cell populations, stained for CD45, CD31, epithelial cell adhesion molecule (EpCAM), α6-integrin (CD49f) and α2-integrin (CD49b). The fluorescence-activated cell sorting diagrams show the reduction in basal and luminal progenitor populations in β1-integrin-null MECs (treated with 4-OHT). f Quantification of cell types from β1-integrin^fx/fx MECs in the absence or presence of 4-OHT (n = 3). There was a significant reduction in basal and luminal progenitor cell populations, as well as an increase in the differentiated luminal cells. Error bars = SEM (Student’s t test for paired samples). * = p < 0.05, ** = p < 0.01, *** = p < 0.001