OLIG2 is a basic helix-loop-helix transcription factor which is expressed in oligodendroglial tumors of the brain. OLIG2 is an essential regulator of ventral neuroectodermal progenitor cell fate. It is associated with T-cell acute lymphoblastic leukemia due to a chromosomal translocation t(14;21)(q11.2;q22). OLIG2 might play a role in learning deficits associated with Down syndrome.