Pseudo-WPB formation after WT and mutant rVWF expression. HEK293 cells were transiently transfected with either WT rVWF in (A,B,J); rVWF-Cys1225Gly (C-E); rVWF-Cys788Arg (F-G), or rVWF-Arg273Trp (H,I,K), and were observed by transmission electron microscopy 2 days (WT, Cys788Arg, and Cys1225Gly) or 3 days (Arg273Trp) later. Sections were made en face, as shown in panels A-I, or in a pellet in panels J-K. Longitudinal sections of membrane-bound pseudo-WPBs with internal striations are shown in panels A-I. Note that in some of the pseudo-WPBs, there are few striations, as shown in panel G (arrowhead), or only one striation, shown in panels D-E (arrowhead), and that there is empty space in these organelles, shown in panels E and G (arrows). The inset in panel E shows as enlargement of the region boxed with a dashed line in panel D. After WT rVWF expression, the ER is normal as shown in panel J, but rVWF-Arg273Trp expression induces the deformation of the ER, which becomes swollen. The star in panel J indicates a mitochondrion. Scale bar is 200 nm (50 nm in panel E).