Fig. 4. Quantification of oligodendrocyte marker gene expression in the spinal cord of mice carrying Sox8 and Sox10 null alleles. The number of Olig2-positive cells (A,B), Plp-positive (white bars) or Mbp-positive (black bars) cells (C,D) was determined at 18.5 dpc (A,C) and postnatal day 3 (B,D) in wild-type (+/+), Sox8^lacZ/lacZ, Sox10^+/lacZ and Sox8^lacZ/lacZ, Sox10^+/lacZ spinal cords, as indicated below the bars. At least 15 separate 20 µm sections from the forelimb region of two independent embryos were counted for each genotype. Data are presented as mean±s.e.m. Differences from the wild type were statistically significant for all mutant genotypes in C,D, as determined by Student's t-test (P0.001).