NEUROGENESIS AND CELL-DEATH IN OLFACTORY EPITHELIUM

The olfactory epithelium (OE) of the mammal is uniquely suited as a mo del system for studying how neurogenesis and cell death interact to re gulate neuron number during development and regeneration. To identify factors regulating neurogenesis and neuronal death in the OE, and to d etermine the mechanisms by which these factors act, investigators stud ied OE using two major experimental paradigms: tissue culture of OE; a nd ablation of the olfactory bulb or severing the olfactory nerve in a dult animals, procedures that induce cell death and a subsequent surge of neurogenesis in the OE in vivo, These studies characterized the ce llular stages in the olfactory receptor neuron (ORN) lineage, leading to the realization that at least three distinct stages of proliferatin g neuronal precursor cells are employed in generating ORNs, The identi fication of a number of factors that act to regulate proliferation and survival of ORNs and their precursors suggests that these multiple de velopmental stages may serve as control points at which cell number is regulated by extrinsic factors, In vivo surgical studies, which have shown that all cell types in the neuronal lineage of the OE undergo ap optotic cell death, support this idea, These studies, and the possible coregulation of neuronal birth and apoptosis in the OE, are discussed . (C) 1996 John Wiley & Sons, Inc.