NORMAL TEMPORAL AND SPATIAL-DISTRIBUTION OF OLIGODENDROCYTE PROGENITORS IN THE MYELIN-DEFICIENT (MD) RAT

A point mutation in exon 3 of the proteolipid protein (PLP) gene of th e myelin-deficient (md) rat leads to a failure of oligodendrocyte matu ration and early death of oligodendrocytes, resulting in dysmyelinatio n. It has been suggested that an alternative-splice isoform of PLP, kn own as DM-20, might be expressed in oligodendrocyte progenitors in the embryonic central nervous system (CNS), raising the possibility that early development of the oligodendrocyte lineage might also be affecte d in the md rat. To test this suggestion, we visualized oligodendrocyt e progenitors in the embryonic md rat spinal cord and brain by in situ hybridization with a probe to the platelet-derived growth factor alph a receptor (PDGFR). We could detect no abnormalities in the time of fi rst appearance of oligodendrocyte precursors, nor in their subsequent proliferation and dispersal throughout the CNS, These data strongly su ggest that the PLP mutation in the md rat primarily or exclusively aff ects the later stages of oligodendrocyte lineage. (C) 1997 Wiley-Liss, Inc.