Figure 5.
Ascl1 lineage cells become interneurons in granule and periglomerular layers of the olfactory bulb. Immunofluorescence of Ascl1 CreERTM;R26R-stop-YFP mouse brain sections harvested 5 or 30 d after tamoxifen administration at P60. A–D, Five days after tamoxifen treatment some YFP cells (green) are located near the SVZ (A) and colabel with Sox2 (A, inset; red), but most YFP cells were found within the RMS (B, C) and colabel with the neuroblast marker Dcx (D, arrows). In contrast, 30 d after tamoxifen treatment no YFP cells were detected around the SVZ or RMS (A', B'). At this time the YFP cells were found in the olfactory bulb (C') and express the mature neuronal marker NeuN (E, arrows). F–I, Most YFP cells in the olfactory bulb 30 d after tamoxifen treatment localized to the GCL where newly generated neurons are homogenously GABAergic shown here as overlap with GAD67 (F). A much smaller proportion of YFP cells were located near the GL in diverse interneuron types overlapping with calretinin (G), TH (H), or calbindin (I). Diagrams depict SVZ in a coronal section, or SVZ and RMS, or olfactory bulb in a sagittal section of an adult mouse brain. Boxes indicate the location where images were taken. LV, Lateral ventricle; TH, tyrosine hydroxylase; TM, tamoxifen. Scale bars: 20 μm.