EMBRYONIC EXPRESSION OF MYELIN GENES - EVIDENCE FOR A FOCAL SOURCE OFOLIGODENDROCYTE PRECURSORS IN THE VENTRICULAR ZONE OF THE NEUROL TUBE

2',3'-cyclic-nucleotide 3-phosphodiesterase (CNP) is an abundant prote in of myelinating oligodendrocytes. We report that one of the alternat ively spliced CNP mRNAs is also expressed in cultured oligodendrocyte progenitor cells. In situ hybridization revealed a thin longitudinal c olumn of CNP-positive cells in the ventral ventricular zone of the emb ryonic day 14 rat spinal cord, coincident in time and space with cells that express the platelet-derived growth factor a receptor, another p utative marker of the oligodendrocyte lineage. These data support the hypothesis that the oligodendrocyte lineage originates at a discrete l ocation in the ventral ventricular zone of the embryonic day 14 rat sp inal cord. We further report that transcripts encoding the myelin prot eolipid protein (PLP/DM-20) are expressed in an unidentified populatio n of neural progenitors in the ventricular zone abutting the floor pla te. Our results support the idea that the ventricular zone is a mosaic of specialized progenitor cells.