Tissue processing was performed essentially as described previously7. Briefly, mice were deeply anesthetized, perfused with pre-cold sodium cacodylate buffer. Optic nerve and spinal cord were dissected immediately and postfix with 2.5% glutaraldehyde overnight at 4 °C. Treated with 1% osmium tetroxide, dehydrated, and embedded into PolyBed resin. 70-nm ultrathin sections stained with lead citrate for electron microscopy imaging by using JEM-2100HC and Hitachi HT-7800.
