Endosome morphologies in cells overexpressing Bro1 or the Bro1 domain. (A–F) 2D cross sections and 3D models from 200-nm-thick section electron tomograms. Spherical endosomal limiting membranes are depicted in yellow, whereas flattened class E compartments are depicted in various colors to discriminate discrete membranes. Lumenal vesicles are red. V, vacuole. Bars, 100 nm or 200 nm as noted. (G–L) Gallery of tomographic slices of wild-type cells with and without overexpression of Bro1 or the Bro1 domain. Freely detached ILVs are traced in red, whereas ILV budding profiles and the limiting endosomal membrane are traced in yellow. In some cases, the continuity of ILV budding profiles with the limiting endosomal membrane is out of plane in the tomographic slice but evident in the 3D reconstruction. Bars, 50 nm.