Chapter 8: Regulation of gene expression in the olfactory neuroepithelium: A neurogenetic matrix

The olfactory neuroepithelium exhibits neurogenesis throughout adult life, and in response to lesions, a phenomenon that distinguishes this neural tissue from the rest of the mammalian brain. This chapter reviews studies on the expression of B50/GAP43 during ontogeny of the olfactory system and following lesioning. This analysis includes the characterization of the expression of olfactory marker protein (OMP), a protein expressed in mature olfactory neurons, as well as protein kinase-C and calmodulin. The latter two molecules are of particular interest to the function of B50/GAP43 because the degree of phosphorylation of B50/GAP43 appears to determine B50/GAP43's ability to bind calmodulin. In the mature olfactory epithelium, B50/ GAP-43 expression is restricted to a subset of cells located in the basal region. Because the expression of B50/GAP43 is high in developing and regenerating nerve cells, the B50/GAP43 positive cells are new neurons derived from the stem cells in the basal region of the epithelium. B50/GAP43 is absent from the stem cells themselves and also from the mature OMP-expressing neurons.