FIG. 2.

Cre activity in adult NSC niches and migration targets. (a) Representative X-gal stained brain sections from mice 48 h after two tamoxifen administrations at P28 (12-h interval). X-gal signal was mainly restricted to SVZ (a1), with little or no signal observed in rostral migratory stream (RMS) (a1, a4). Immunohistochemistry following X-gal staining revealed that the majority of X-gal positive cells express glial fibrillary acidic protein (GFAP). A few X-gal positive cells (black arrows) also express doublecortin (DCX) in subventricular zone (SVZ) (a3) and RMS (a4). (b) Representative X-gal-stained brain sections from 6- or 8-week-old Nes73-CreER^T2;Rosa26^lacZ mice that were induced at 4 weeks of age show the dynamics of X-gal-positive cells in the hippocampus (HP), SVZ and olfactory bulb (OB). (c) Representative β-galactosidase (β-Gal) and NeuN staining of hippocampus 2 or 4 weeks after tamoxifen induction at 4 weeks of age. Newly generated β-Gal-positive neurons slowly migrate into the granular cell layer (white arrows). (d–f) Representative immunofluorescence staining showing the presence of β-galactosidase (β-Gal)-expressing (hence, Cre active) cells in Nes73-CreER^T2;Rosa26^lacZ mice 4 weeks after tamoxifen induction. (d) Expression of β-Gal was observed in NSCs that also express nestin and GFAP (white arrows, for example). (e) Doublecortin-positive neural progenitor cells also expressed β-Gal in the SVZ, HP, rostral migratory stream (RMS), and OB (white arrows, for example). In the OB, some β-Gal-positive cells were Doublecortin-negative, and thus possibly represent mature neurons (white arrowheads, for example). (f) Multiple lineages of differentiated cells with β-Gal expression. Top panels: mature neurons (generated by adult NSCs) that migrated into the hippocampal (HP) granular layers were rare (white arrows, for example), while the majority of β-Gal-positive cells were NeuN-negative (white arrowheads, for example). In the OB, a significant number of mature neurons were contributed by adult neurogenesis as shown by β-Gal and NeuN double labeling. Bottom panels: adult NSCs were also found to differentiate into GFAP-positive astrocytes (white arrows, for example) in the OB and corpus callosum (CC).