Figure 9.

Model of stem cell and progenitor cell relationships in the olfactory epithelium (OE), based on data presented here and previous published findings regarding globose basal cell (GBC) molecular heterogeneity (Goldstein and Schwob, 1996; Cau et al., 1997, 2002; Manglapus et al., 2004; Jang et al., 2007; Leung et al., 2007; Guo et al., 2010; Packard et al., 2011a,b; Fletcher et al., 2011), results following transplantation of GBCs (Goldstein et al., 1998; Chen et al., 2004), and data obtained via retroviral lineage tracing in the MeBr-lesioned epithelium (Huard et al., 1998). Key points to emphasize include: 1) the subdivision of the population of GBCs on the basis of transcription factor expression and kinetic status into putative stem (STEM), multipotent progenitor (MPP), transit amplifying (TA), and immediate neuronal precursor (INP) stages; the rainbow of colors at stem and multipotent progenitor stages represents the demonstrated capacity of these GBC types to generate all the cell types of the OE; 2) the restoration of label-retaining (LR) and p27-expressing GBCs (GBC_STEM) following the universal proliferation (Ki-67 expression) induced by MeBr lesion of the OE (double-headed arrow between GBC_STEM and GBC_MPP); and 3) the role of upregulation and downregulation of p63 (up arrow and down arrow, respectively) in the conversion of horizontal basal cells (HBCs), a putative reserve stem cell population, to and from dormancy, respectively. OSN, olfactory sensory neuron. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]