Short-term lineage analysis of dorsally derived Olig3 cells in the developing spinal cord.

We examined the migration and differentiation of cells expressing Olig3, a basic helix-loop-helix transcriptional factor, in the developing spinal cord. Distribution of Olig3 lineage cells was demonstrated with in situ hybridization and X-gal staining in an Olig3-lacZ knock-in mouse. Olig3-positive cells first appeared in the dorsal spinal cord, except for the roof plate. Some of the dorsal Olig3 lineage cells co-expressed Islet1/2, Math1, or Brn3a, markers for dorsal interneuron. LacZ-positive cells were observed in the ventral-most part of the E10.5 spinal cord, suggesting that some dorsal Olig3 lineage cells migrate into the ventral-most part by E10.5. Ventral-ward migration of dorsal cells and contribution to commissural interneurons were substantiated by electroporation of EGFP expression plasmid in the dorsal spinal cord of chick embryo. Dorsal midline cells were also LacZ-positive during development. These findings suggest that dorsal Olig3 cells contribute to dorsal midline cells and commissural interneurons at intermediate and ventral levels.