Olig family is a novel sub-family of basic helix-loop-helix transcription factors recently identified. Olig 1 and Olig2 were first reported to promote oligodendrocyte differentiation. and later Olig2 was reported to be involved in motorneuron specification as well. Olig3 was isolated as a third member of Olig family. but its precise expression pattern is poorly understood. Here, we describe detailed Olig3 expression analyses in the neural tube of embryonic mice. Olig3 was first detected in the dorsal neural tube from the hindbrain/hindbrain boundary to the spinal cord. In E11.5 spinal cord. Olig3 was transiently expressed in the lateral margin of the subventricular zone as three ventral clusters at the level of the p3, p2 and p0 domains, as well as in the dolorsal neural tube. Olig3 was co-expresed with Nkx2.2 in the lateral margin of the p3 domain. In forebrain Olig3 was expressed in the dorsal thalamus while Olig2 was complementarily expressed in the ventral thalamus with an adjacent boundary at E12.5. Olig3 is specifically and transiently expressed in different types of progenitors of embryonic central nervous system and then disappears in the course of development. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.