FIG. 7.

In-depth analysis of RVN membrane discontinuities after BFA treatment. The tomograms that were used for our ultrastructural analysis of RVN membranes in BFA-treated cells were scrutinized for openings that connect the DMV interior with the cytosol. (A to D) Examples of membrane discontinuities observed in our specimens (arrowheads), including a number that were present on the side of the vesicle facing the CM (e.g., in panels A and C), where double membranes remained tightly apposed. We doubt whether these discontinuities could be associated with viral RNA trafficking between vesicle interior and cytosol and consider it more likely that they may be artifacts resulting from the previously documented fragility of the RVN, which may actually be promoted by BFA treatment. Panels A to D also illustrate the separation of DMV inner and outer membranes during BFA treatment. However, the increased luminal space was generally lacking at the side of the DMV that faces the CM, where the two membranes remained tightly apposed. Panel D also shows an example of a necklike connection between the outer membranes of two DMVs. Bar, 100 nm.