Fig. 7. Role of Fgf8 in olfactory neurogenesis. Cartoon illustrating the relative positions of the Fgf8 expression domain (anterior morphogenetic center) and different neuronal cell types during primary neurogenesis at E10.5 in normal OE (wild type) and a model for the role of Fgf8 in primary olfactory neurogenesis based on the consequences of inactivating Fgf8 in the anterior morphogenetic center using Foxg1-driven Cre (mutant). Fgf8 expression domain, orange; Sox2 expression domain (definitive neuroepithelium), yellow; primordial neural stem cells (co-expressing Sox2 and Fgf8), green; Mash1-expressing committed neuronal progenitors, dark blue; INPs, light blue; Ncam1-expressing neurons, pink. Cells in the Fgf8 expression domain that undergo apoptosis when Fgf8 is inactivated are shown in red, and apoptotic primordial neural stem cells in green with a red jagged border. Vestigial populations of other neuronal cell types are shown in their corresponding colors, but with jagged borders. For discussion, see text.