Fig. 4.

The lack of MFN1 does not affect mitochondrial juxtaposition but blocks OPA1-induced mitochondrial tubulation. WT (A), Mfn1–/– (B), and Mfn2–/– (C) MEFs were cotransfected with mtYFP and empty vector (Upper) or with mtYFP and OPA1 (Lower), and, after 24 h, confocal z-stacks were acquired as described in Supporting Materials and Methods. Stacks were reconstructed and volume-rendered, and movements of individual mitochondria were tracked. Five-fold magnified portions of single z-planes corresponding to the indicated frames are shown. For the sake of clarity, mitochondria were individually labeled in different colors. Arrowheads indicate sites of mitochondrial contact. Colors of tubular mitochondria resulted from the merging of the colors of the individual mitochondria from which they originated. (Scale bar, 4 μm.)