Promotes formation and maturation of oligodendrocytes, especially within the brain. Cooperates with OLIG2 to establish the pMN domain of the embryonic neural tube. Expressed specifically in brain. Expressed in the ventral spinal cord as early as 9.5 dpc. Expression declines to undetectable levels by 10.5 dpc and reappears in a narrow zone within the ventral neuroepithelium of the spinal cord. In the 14.5 dpc spinal cord, expressed in the oligodendrocyte progenitors of the ventral ventricular zone, but not dorsal root ganglia Schwann cells. Also expressed scattered in the mantle zone, likely corresponding to oligodendrocyte progenitors migrating out from their site of origin. By 15.5 dpc, dispersed throughout the gray matter, with little or no residual expression in the ventricular zone. In the postnatal brain, present preferentially in the white matter, such as corpus callosum and cerebellar medulla. Expressed in the olfactory epithelium from 11.5dpc onward. By SHH.