Fig. 7. KBP is required for microtubule organization, localization of axonal mitochondria and synaptic vesicles, and axonal maintenance in the PNS. (A,B) TEM images of transverse sections through the PLLn at 30 hpf shows more organized microtubules (black arrowheads) in wild-type (A) axons than in kbp^st23 mutant (B) axons and disorganized microtubules (white arrowheads) in kbp^st23 mutant (B) axons. Scale bars: 200 nm. (C,D) TEM images of longitudinal sections through the PLLn at 50 hpf show more profiles of properly oriented microtubules (arrowheads) running parallel to the long axis of the axon in wild type (C) than in the kbp^st23 mutant (D). White arrow indicates an accumulation of synaptic vesicles in a kbp^st23 mutant axon. Scale bars: 0.5 µm. (E,F) TEM images of transverse sections through the PLLn at 72 hpf show more myelinated axons (black asterisks) and mitochondria within axons (white arrowheads) in the wild type (E) than in the kbp^st23 mutant. White asterisks in F indicate myelinated axons undergoing degeneration. Scale bars: 0.5 µm.