Ultrastructure of the sciatic nerve from P60 and P75 control and Miz1ΔPOZ animals reveal signs of demyelination and dysmyelination. Ultrastructure of the sciatic nerve from P60 and P75 control and Miz1ΔPOZ animals reveal signs of demyelination and dysmyelination. A, Nerve from a P75 control animal showing densely packed myelinated (*) axons and Remak bundles (Rb), which contain the unmyelinated axons. B, Nerve from a P60 Miz1ΔPOZ animal, which appears to be similar to nerves from control animals. C, However, at P60 Miz1ΔPOZ mice exhibit occasionally demyelinated axons and myelin loops (arrowheads in the insets), which indicate demyelination. D–G, In P75 Miz1ΔPOZ animals, demyelination occurred extensively, with different grades of myelin loops (D, arrowheads at axon 2, E) and autophagic degradation of myelin by Schwann cells (F), resulting in demyelinated (G) or hypomyelinated (D, compare 3 with the normal-appearing axon 1) axons. Line in E marks a Schwann cell with extensive myelin loops (arrowheads). Note that in G the different size of the unmyelinated axons in the Remak bundle (white line) compared with the demyelinated axon (Ax) in the adjacent Schwann cell (red line). H, In the extracellular space, myelin debris (arrow) is phagocytosed by macrophages (M and arrowheads). I, Higher magnification of area shown in white rectangle in H. Note that this cell has no basement membrane and is thus not a Schwann cell. N, Nucleus; Co, collagen fibers; Sc, Schwann cell. David Fuhrmann et al. J. Neurosci. 2018;38:858-877 ©2018 by Society for Neuroscience