a, LATS is mostly nuclear in basal cells and cytoplasmic in luminal cells. Representative pictures of LATS1 staining (immunohistochemistry) in normal human breast (left; scale bar, 100 μm), of PHBECs stained (immunofluorescence) with KRT19, KRT14 and LATS1 (middle; scale bars, 150 μm), and of a human breast tumour TMA (right; scale bars, 50 μm). Quantification of LATS nuclear and cytoplasmic staining by immunofluorescence in PHBECs (middle, n = 8). Box plots representing ERα-index of tumours characterized by cytoplasmic or nuclear LATS immunohistochemistry staining (right; n = 471; P < 0.0001). b, qPCR analysis of sorted PHBEC subpopulations (fold change over stroma and mesenchymal cells (MSC)). Luminal markers are shown in blue, basal markers are shown in red (n = 2 biological replicates with 3 experimental replicates each). c, The fractions of mature luminal and luminal progenitor cells increase upon removal of LATS. Representative scatter plots and bar graphs of cell-surface/intracellular FACS analysis of shNT- and shLATS-treated PHBECs stained with antibodies against c-KIT and ERα (n = 2 biological replicates with 3 experimental replicates each). d, Representative immunofluorescence pictures of colonies formed by breast cell subpopulations. Scale bars, 150 μm. e, YAP/TAZ targets are highly expressed in basal cells. qPCR analysis of sorted basal and c-KIT+ luminal progenitor cells (n = 2 biological replicates with 3 experimental replicates each). f, Sorted basal primary mouse MECs acquire a luminal phenotype upon removal of Lats, and removal of Lats enhances the luminal phenotype in sorted luminal MECs. Representative immunofluorescence pictures and quantification of the colony phenotype of sorted basal (top) and luminal (bottom) MECs with and without Lats1 + 2 stained for KRT14 and KRT8/18. n = 20 pooled mice; basal shNT, n = 46 colonies; basal shLats, n = 23 colonies; luminal shNT, n = 30 colonies; luminal shLats, n = 20 colonies. Scale bars, 200 μm. g, Depletion of Lats in sorted primary MECs increases luminal mature and progenitor markers and decreases basal and mammary stem-cell-related markers (qPCR; n = 20 pooled mice; 6 experimental replicates). h, Cells lacking LATS exhibit a luminal progenitor-like phenotype when grown in 3D collagen gels. Left, representative pictures of TDLU- and sphere-like structures formed by PHBECs on floating collagen. Right, representative immunofluorescence confocal pictures of 3D structures stained for basal (KRT14) and luminal (KRT18, E-cadherin) markers. Scale bars, 200 μm. i, Depletion of Lats in primary mouse MECs increases luminal mature and progenitor markers and decreases basal and mammary stem-cell-related markers (qPCR, n = 25 pooled mice, 6 experimental replicates). j, Graphical summary. Depletion of LATS expands luminal and bipotent progenitors and enhances differentiation along the luminal lineage at the expense of basal progenitors and basal cells. This results in a population of cells with high sphere-forming capacity, low mammary repopulating activity, and a luminal phenotype. Data are mean ± s.d.(a–c, e, g, i); *P < 0.05; **P < 0.01.