Fig. 2. Delayed and reduced production of Pdgfra + (A-H) and NG2+ (I-L) OPCs in Nkx6.1 mutant spinal cords. Spinal cord sections from E13.5 (A,B), E15.5 (C,D,I,J), E17.5 (E,F) and P0 (G,H,K,L) wild-type (A,C,E,G,I,K) and mutant (B,D,F,H,J,L) embryos were subjected to in situ hybridization with Pdgfra riboprobe or double immunofluorescence with anti-NG2 (red) and anti-PECAM1 (green) antibodies. During embryogenesis, NG2 labels both OPC cells and PECAM1+ immature blood vessels (Ozerdem et al., 2001).