Immunofluorescent localization of VWF in primary MKs transfected with wild-type or dominant-negative versions of Rab27. There is no change in the distribution or abundance of VWF in MKs expressing GFP-tagged wild-type (WT, n = 50) or dominant-negative forms Rab27bN133I (n = 54) or Slp1(1-150) (n = 40). MKs were transfected with GFP fusion constructs and harvested 24 hours later, cytocentrifuged onto glass slides, fixed, immunostained for VWF, and scored individually. Cells were mounted with aqueous medium containing DAPI (4,6 diamidino-2-phenylindole) and visualized by fluorescence microscopy. Original magnifications, × 400 for all panels.