Mitochondrial transport impacts terminal mitochondrial recruitment and growth cone size. (A and B) Representative images (A) and quantitative analysis (B) showing correlation of mitochondrial density in the axonal terminals and growth cone size of adult DRG neurons after dissociation axotomy. Adult DRG neurons isolated from P60 mice were cotransfected with DsRed-Mito, GFP, and control vector, SNPH, SNPH-dMTB, or Mrio1, followed by immunostaining with Tau at DIV2. Note that expressing SNPH, but not its loss-of-function mutant SNPH-dMTB, blocks the delivery of mitochondria into growth tips and reduces average size of growth cones, whereas expressing Miro1 robustly increases terminal mitochondrial density and size of growth cones. (C and D) Images (C) and quantitative analysis (D) of distal mitochondrial distribution and growth cone size in cortical neurons coexpressing DsRed-Mito with GFP or together with SNPH, SNPH-dMTB, or Miro1. Neurons at DIV5 were immunostained with Tau. Note that both mitochondrial density in terminals and the average size of growth cones are decreased in neurons expressing SNPH (P < 0.01 and P < 0.001, respectively), but increased in neurons expressing Miro1 (P < 0.05) relative to control neurons. Arrows indicate the most distal mitochondrion in the SNPH-expressing axons (C). Data were analyzed from the total number of axons indicated within bars from more than three experiments and expressed as mean ± SE and by one-way ANOVA test. Bars, 10 µm.