Sonic Hedgehog is a potent inducer of rat oligodendrocyte development from cortical precursors in vitro

Sonic Hedgehog (Shh) induces oligodendrocyte development in the ventral neural tube and telencephalon but its role in oligodendrocyte generation in dorsal telencephalon is debated. Transcripts for Shh and its receptor complex were detected in subventricular zone and neocortex from E17 to birth. As Shh is not yet expressed in E15 neocortex, we grew El 5 cortical precursors (CP) into neurospheres in the presence of recombinant Octyl-Shh (0Shh). After sphere adhesion and removal of O-Shh, enhanced neurite outgrowth and cell migration were already observed at 3 h. Three days after O-Shh treatment, oligodendrocyte progenitors (OP) emerged and continued to increase in number for 7 days while the ratio of neuronal cells decreased compared to control. Shh selectively triggered mitosis of OP but not neuronal progenitors and enhanced growth of neonatal OP. Thus Shh in E15-17 embryonic neocortex can signal CP to adopt an oligodendrocyte fate and favors expansion of this lineage.