Analysis of myelinating cells in uninjured and injured zebrafish spinal cord

<p><b>:</b> A-C) A transverse section of uninjured cord stained with CNPase/MAG/DAPI (A), only CNPase (B) and only MAG (C) respectively. D-G) A 10 dpi cord section stained with CNPase/MAG/DAPI (D) and only CNPase and MAG respectively (E-F) and its DIC image (G) D1) Higher magnification of boxed area in section D showing many colocalized CNPase⁺ and MAG⁺ cells (white arrows) in the white matter. E1) Higher magnification of boxed area in section E, showing CNPase⁺ cells (white arrows) are in the white matter. H-K) A 10 dpi cord section stained with CNPase/GFAP/DAPI (H) and only CNPase and GFAP respectively (I-J), same DIC image (K). H1) Higher magnification of boxed area in section H showing colocalized CNPase⁺ and GFAP⁺ cells (yellow arrows). I1) Higher magnification of boxed area in section I showing CNPase⁺ cells in the white matter. L) Ultrastructure of an oligodendrocyte in the injury site of a 10 dpi cord (blue arrow) with presence of characteristic cisternae of smooth endoplasmic reticulum (white arrowheads, SER), microtubules (MT, red arrows), primary lysosome (pLY, green arrow) and polyribosomes (pRB). Note that the cytoplasm of this oligodendrocyte is without demyelinated axon fibers hence may not actively involved in remyelination process. M) Ultrastructure of a 10 dpi cord section shows three newly formed Schwann cells (red arrowheads) with small cytoplasmic area and nucleus (NU), high N/C index, very thin intercellular spaces and basal lamina (BL, black arrow) close to axolemma (AXL, white arrow). Some cells also have microtubules (MT, red arrows) and few cytoplasmic organelles like primary lysosomes (pLY, green arrows). N) A 30 dpi cord section shows a Schwann cell (red arrow) with a prominent nucleus (NU) remyelinating two demyelinated axons (DAX) surrounded by plasmalemma (PL). The cytoplasm also contains many mitochondria (MITO). ‘cc’ denotes central canal of the cord. Scale bar = 50 μm (A-K); 20 μm (D1, E1, H1, I1); 1 μm (L, M, N).