Histological analysis of myelination after CNS-specific Sox10 deletion and consequences of combined deletion of Sox8 and Sox10 on myelin gene expression.

<p>(<b>A–C</b>) Light microscopy of 1 µm semi-thin sections of the spinal cord ventral horn in wildtype (wt) (<b>A</b>) and <i>Sox10^ΔCNS</i> (ko) mice (<b>B,C</b>) at P14 following Richardson's stain. Myelinated axons are stained in the white matter (WM) of the wildtype, but not the mutant. Sections from <i>Sox10^ΔCNS</i> mice contain myelin only in the anterior rootlet (AR) where it is formed by Schwann cells. <b>C</b> represents a higher magnification of the area boxed in B. GM, grey matter. Scale bars, 100 µm. (<b>D–F</b>) Transmission electron microscopy of the wildtype spinal cord ventral horn at P14 shows myelinated axons (<b>D</b>, black arrows) around an OL (OL) in the white matter. In contrast, OL in <i>Sox10^ΔCNS</i> mice are surrounded by axons that lack myelin sheaths (<b>E</b>,<b>F</b>, black arrows). In mutant mice only Schwann cells in the anterior rootlet have formed myelin sheaths (<b>F</b>, white arrow). Scale bars, 2.5 µm. (<b>G–R</b>) Differentiating OL were visualized by in situ hybridization on transverse spinal cord sections from the forelimb region of wildtype (wt) (<b>G,H,K,L,O,P</b>) or <i>Sox10^ΔCNS Sox8^lacZ/lacZ</i> (dko) (<b>I,J,M,N,Q,R</b>) mice at P7 (<b>G,I,K,M,O,Q</b>), and P16 (<b>H,J,L,N,P,R</b>) using antisense probes against <i>Mbp</i> (<b>G–J</b>), <i>Plp</i> (<b>K–N</b>), and <i>Myrf</i> (<b>O–R</b>). Ventral horn region is shown. Scale bar, 200 µm.