Fig. 1. Reduced and delayed Olig2 expression in Nkx6.1 mutant spinal cord at the thoracic region. Transverse spinal cord sections from E12.0 (A,B), E13.5 (C,D), E15.5 (E,F), E17.5 (G,H) and P0 (I,J) wild-type (A,C,E,G,I) and Nkx6.1 (B,D,F,H,J) mutants embryos were subjected to in situ hybridization with riboprobe for Olig2. In Nkx6.1 mutants, the early expression of Olig2 in the ventral ventricular zone is markedly reduced and asymmetrically displayed, and the generation of Olig2+ OPC cells is dramatically delayed and reduced.