Fig. 1.

Altered mitochondrial morphology, distribution, and activity in SRF-deficient neurons. (A and B) Mitochondria (arrows) in P14 corpus callosal axons of WT neurons are electron-dense. (C) Higher magnification reveals a double membrane of a mitochondrion indicated by the dashed area in A. (B) In contrast, in axons of SRF-deficient neurons, mitochondria are vacuolized and frequently bottle-shaped (higher magnification flipped 90° in D). WT (E and F) and Srf mutant (G and H) P14 cortices were labeled for mitochondria (Tom20, red) and neurites (Smi32, green). In WT neurons, mitochondria were present in neurites (arrows in E), whereas abundance was reduced in SRF-deficient neurons (arrows in G). (I) Number of vacuolized mitochondria (vac. mito.) in an axon cross-section is depicted. ko, knockout; wt, wild type. (J) Basal ATP content in mitochondria of P14 Srf mutant brains is reduced compared with WT. (K) ATP production rate is decreased in mitochondria derived from SRF-deficient hippocampi compared with WT. (L) Percentage of mitochondria found in neurite segments ranging from 0 to ≥60 μm. In neurite parts >60 μm away from the cell body, mitochondria were reduced in Srf mutants compared with WT. Numbers in bars represent numbers of independent animals. (Scale bar: A–D, 1 μm; E–H, 10 μm.)