Dynamic expression of basic helix-loop-helix Olig family members: implication of Olig2 in neuron and oligodendrocyte differentiation and identification of a new member, Olig3

Basic helix-loop-helix (bHLH) transcription factors have been shown to be e ssential for specification of various cell types. Here, we describe a novel bHLH family consisting of three members, two of which (Olig1, Olig2) are e xpressed in a nervous tissue-specific manner, whereas the third, Olig3 is f ound mainly in non-neural tissues. Olig1 and Olig2, which recently have bee n implicated in oligodendrogenesis, are expressed in the region of the vent ral ventricular zone of late embryonic spinal cord where oligodendrocyte pr ogenitors appear. In the embryonic brain, the Olig2 expression domain is br oader than that of Olig1 and does not overlap with an oligodendrocyte proge nitor marker, CNP. Furthermore, Olig2 is expressed in most cells in the ven tral half of the early embryonic spinal cord, which do not yet express an e arly neuronal marker TuJ1. These results indicate that Olig2 expression is not limited to the oligodendrocyte lineage but includes immature neuronal p rogenitors and multipotential neuron/glia progenitors as well as embryonic olfactory neurons. (C) 2000 Elsevier Science Ireland Ltd. All rights reserv ed.