Fig. 4. Defective oligodendrocyte differentiation in the Nkx2.2 mutant brains. (A,B) Sagittal sections of the E17.5 wild-type (A) and mutant (B) hindbrain/midbrain tissues were subject to in situ hybridization with MBP probe. Many fewer MBP-positive cells are detected in the ventral brain stem of the mutant. (C-F) Coronal sections of P7 wild type (C,E) and mutant (D,F) were hybridized with MBP (C,D) and PLP-DM-20 (E,F) riboprobes. In the wild-type mice, numerous MBP-positive and PLP-DM20-positive oligodendrocytes are found in association with corpus callosum (cc) and anterior commissure (ac), whereas in the mutants, no clear labeling of MBP and PLP-DM20 is observed.