Postnatal neurogenesis and gliogenesis in the olfactory bulb from NG2-expressing progenitors of the subventricular zone

We used a 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNP)-enhanced green fluorescent protein (EGFP) transgenic mouse to study postnatal subventricular zone (SVZ) progenitor fate, with a focus on the olfactory bulb (OB). The postnatal OB of the CNP-EGFP mouse contained EGFP(+) interneurons and oligodendrocytes. In the anterior SVZ, the majority of EGFP(+) progenitors were NG2(+). These NG2(+)/EGFP(+) progenitors expressed the OB interneuron marker Er81, the neuroblast markers doublecortin (DC) and Distalless-related homeobox (DLX), or the oligodendrocyte progenitor marker Nkx2.2. In the rostral migratory stream (RMS), EGFP(+) cells displayed a migrating phenotype. A fraction of these cells were either NG2(-)/Er81(+)/DC+/DLX+ or NG2(+)/Nkx2.2(+). DiI (1,1'-dioctadecyl-3,3,3', 3'-tetramethylindocarbocyanine perchlorate) injection into the lateral ventricle (LV) of early postnatal mice demonstrated that NG2 (+)/EGFP(+) progenitors migrate from the SVZ through the RMS into the OB. Moreover, fluorescence-activated cell-sorting- purified NG2(+)/CNP-EGFP (+) or NG2(+)/beta-actin-enhanced yellow fluorescent protein-positive (EYFP+) progenitors transplanted into the early postnatal LV displayed extensive rostral and caudal migration. EYFP+ or EGFP (+) graft-derived cells within the RMS were DLX+/ Er81(+) or Nkx2.2(+), migrated to the OB, and differentiated to interneurons and oligodendrocytes. In the subcortical white matter (SCWM), grafted cells differentiated to either oligodendrocytes or astrocytes. Transplantation of NG2(+)/EYFP+ progenitors selectively purified from the SVZ showed that these cells were migratory and generated glia and neurons in the OB, hippocampus, and striatum. In contrast, cortical, OB, or cerebellar NG2(+) cells had a very limited migratory potential and gave rise to glia in the SCWM and striatum. Our findings indicate region-specific differences between NG2(+) progenitor cells and show that NG2(+) cells can migrate throughout the RMS and contribute to both gliogenesis and neurogenesis in the postnatal OB.