Expression of myelin genes in the embryonic spinal cord in the presence and absence of Sox10. In situ hybridizations with probes specific for MBP (a–h), PLP (i–p), or MAG (k,o, insets) were performed on transverse sections from the forelimb region of embryos. (a–d,i–l) Wild-type embryos. (e–h,m–p) Sox10lacZ/Sox10lacZ embryos. (a,e,i,m) 14.5 dpc. (b,f,j,n) 16.5 dpc. (c,g,k,o) 18.5 dpc. (d,h,l,p) Newborn at 20 dpc. The in situ hybridization signal at 14.5 dpc is marked by an arrowhead.