GATA-3 expression is reduced in Twsg1−/− MGs. ECAD was used to mark luminal epithelial cells and most ECAD positive cells in the WT TEB express GATA-3 (A–D) and mature duct (I–L) while the Twsg1−/− TEB (E–H) and mature duct (I–L) consist of a mosaic of GATA-3 positive and GATA-3 negative luminal cells. Most cells shed into the lumen are GATA-3 negative (P). All images were taken at 40X. Boxes in C, G, K, and O correspond to the magnified images in D, H, L, and P, respectively.