Expression of genes related to oligodendrogenesis, including Olg1 and GPR17 (Chen et al., 2009; Lu et al., 2000) were down-regulated on the array in the Nkx2.1-Cre mutant (Table S1); we failed to detect GPR17 expression by in situ hybridization and Olg1 expression was weak. For this reason, we studied Olg2 expression; its expression was reduced in the SVZ of the MGE at E12.5 (Figures S5P-S5R’). The down-regulation of oligodendrocyte markers may be related to the increase in ID4 RNA; ID proteins can repress oligodendrogenesis (Wang et al., 2001). By E15.5, we did not detect a change in Olg2 expression (Figures S2P-S2R’). The DlxI12b-Cre mutant did not show changes in Olg2 expression (Figure S5NN-S5PP’) suggesting the Zfhx1b function in the VZ, and not SVZ, regulates oligodendrogenesis.
