Fig. 5. Oligodendrocyte development in Sox9^loxP/loxP, Sox10^lacZ/lacZ, Sox10::Cre spinal cords. Immunohistochemistry with antibodies specific for Sox10 (A,E,I,M,Q), β-galactosidase (B,F,J,N,R) and Olig2 (C,D,G,H,K,L,O,P,S,T) were performed at 12.5 dpc (A-D), 13.5 dpc (E-H), 14.5 dpc (I-L), 15.5 dpc (M-P) and 18.5 dpc (Q-T) on transverse sections from the forelimb region of wild-type (A,C,E,G,I,K,M,O,Q,S) or Sox9^loxP/loxP, Sox10^lacZ/lacZ, Sox10::Cre (Sox9^/ Sox10^-/-) (B,D,F,H,J,L,N,P,R,T) embryos. Subcellular localization of Sox10 (nuclear) and β-galactosidase (cytoplasmic) causes a slightly altered appearance of cells in A,E,I,M,Q when compared with B,F,J,N,R. (U-W) OLP numbers were determined at 12.5 dpc (U), 13.5 dpc and 14.5 dpc (V) as Sox10- or β-galactosidase-positive cells, and at 15.5 dpc and 18.5 dpc (W) as Olig2-positive cells in wild-type (white bars), Sox9^loxP/loxP, Sox10::Cre (light-grey bars), Sox10^lacZ/lacZ (dark-grey bars) and Sox9^loxP/loxP, Sox10^lacZ/lacZ, Sox10::Cre (black bars) spinal cords as indicated. For these quantifications, at least 30 separate 10 µm sections from the forelimb region of two independent embryos were counted for each genotype. Data are presented as mean±s.e.m. Differences to the wild type were statistically significant for oligodendrocyte numbers in Sox9^loxP/loxP, Sox10^lacZ/lacZ, Sox10::Cre spinal cords from 14.5 dpc onwards, as determined by Student's t-test (^***P0.001).