Direct evidence that ventral forebrain cells migrate to the cortex and contribute to the generation of cortical myelinating oligodendrocytes

Cortical neuroepithelial cells generate neurons, astrocytes, and oligodendrocytes (OLs) in vitro. However, whether cortical OLs are derived from the cortical neuroepithelium or migrate from the ventral forebrain is under severe debate yet. This is due to the fact that OL progenitor cells (OPCs), as marked by the expression of PDGFR alpha or NG2, are generated at around embryonic day (E) 11 or 12 in the mouse ganglionic eminences, but the myelinating OLs appear during the second week postnatally in the cortex. There has been no labeling method for long-term glial cell-lineage tracing. Thus, we developed a new strategy: plasmid. DNA encoding Cre recombinase Was introduced into the Cre/IoxP reporter forebrain in ventral- or dorsal-specific manner by ill Utero DNA electroporation. The reporter gfp gene is expressed permanently owing to the chromosomal DNA recombination. The GFP-labeled myclinating OLs were detected in the adult cortex when electroporation was targeted to the ventral neuroepithelium, demonstrating at least some of the inyelinating OLs are derived from the ventral forebrain. However, when electroporation was targeted to the dorsal, We Could not find GFP-labeled myelinating OLs. This suggests that the progenitors of cortical OPCs are absent or located at restricted regions in the dorsal forebrain (cortex) at E12. (c) 2005 Elsevier Inc. All rights reserved.