Figure 3
From: A new vicious cycle involving glutamate excitotoxicity, oxidative stress and mitochondrial dynamics
OPA1 mutation induces mitochondrial fission in the RGC axons in Opa1enu/+ mice. OPA1-mutant mitochondria in optic nerve head axons display fissioning. (a–c) Tomographic reconstruction of a long mitochondrion from an adult wild-type control mouse. (a) A 2.4-nm slice through the center of a tomographic volume of an axon shows the mitochondrial membrane profiles and associations including those of outer and inner boundary membranes and cristae in a long mitochondrion with many cristae. Scale bar, 200 nm. (b) Top view and (c) side view of the segmented and surface-rendered volume showing the outer membrane (blue) and the entire complement of 51 cristae (various colors) provide a 3D snapshot of the packing arrangement, shape, and density of cristae. Most of the cristae have both tubular and lamellar compartments. However, some cristae are completely lamellar or completely tubular. Both lamellar and tubular cristae extend transversely. (d–f) Tomographic reconstruction of a shorter mitochondrion fragmented in two in an optic neve head axon from an adult OPA1-mutant mouse. (d) A 2.4-nm slice through the center of a tomographic volume of an axon shows the arrangement of outer and inner boundary membranes and cristae. The point of fission is indicated by the arrow. Note that the two fragmented portions are unequal in size. Scale bar, 200 nm. (e) Top view and (f) side view of the segmented and surface-rendered volume showing the outer membrane (blue) and the nine cristae in the left-hand fragment and the eight cristae in the right-hand fragment. The left-hand fragment has considerably more lamellar or mixed lamellar/tubular cristae than does the right-hand fragment. In contrast to the wild-type control mouse mitochondria, a few lamellar cristae are arranged longitudinally in the left fragment. Even though the outer membranes of the two fragments are touching, there is a clean break (arrows) between fragments. (g) There is no difference in mitochondrial volume density, defined as the volume occupied by mitochondria divided by the volume occupied by the axoplasm in terms of a percentage, in the optic nerve head axons. The bar is the mean and the error bar is the standard error of the mean. The number of measurements, corresponding to the number of images measured, is posted at the top of each bar. (h) Mitochondrial lengths are much shorter in Opa1enu/+ mouse axons than in the wild-type control mouse axons by a factor of nearly two (*P<0.01). The same images were used as in (g). (i) The number of mitochondria, normalized to the total area occupied by axons in each image, is much greater in Opa1enu/+ mouse axons than in the wild-type control mouse axons by a factor greater than two (*P<0.01)
