Fig. 3. Increased CED-9 expression alters mitochondrial morphology. (A,B) Increased CED-9 expression resulted in dilated, interconnected mitochondria. This effect is similar to inactivation of mitochondrial fission by expression of dominant negative DRP-1(K40A) (Fig. 2C). However, we note that DRP-1(K40A)-induced mitochondria are more rounded, and only a fraction of the cells possess thin tubules interconnecting various mitochondria. (C) Removing the N-terminal 67 residues of CED-9 did not abolish the ability of CED-9 to alter mitochondria. However, removing either (D) a core structural helix or (E) the C-terminal transmembrane domain prevented CED-9 from altering mitochondria. Increased CED-9 expression also altered mitochondrial outer membrane morphology as judged by mitochondria labeled with TOM70::GFP, a mitochondrial outer membrane tethered GFP (Labrousse et al., 1999). (F) In otherwise wild-type animals, the mitochondria had a fairly stereotypical tubular morphology. (G) By contrast, transgenic animals with increased CED-9 expression displayed altered outer membrane morphologies. n, nucleus. Bar, 10 µm. (H) Mitochondrial morphology in the body wall muscle of adult animals with increased CED-9 expression was further examined by transmission electron microscopy. Two animals were found that possessed markedly distinct mitochondrial morphologies; shown are two cells from one of the animals. Bar, 500 nm.