Schwann cells are not involved in optic nerve remyelination. (A) There are no GFP positive cells in the remyelinated optic nerve of FoxD3:GFP transgenic zebrafish (labelling neural crest-derived Schwann cells) at 28 dpl whereas peripheral nerves in nearby muscle fascicles are detectable (arrows), confirming expression of the transgene. (B) Schwann cells are also not detected in electron microscopic analysis of remyelinated optic nerve cross sections. (C) Schwann cells have a typical phenotype: the nucleus is closely associated with its myelinated axon, with a basal lamina. Scale bars: A = 100 μm, B = 1 μm.