Olfactory Neuronal Cell Lines Generated by Retroviral Insertion of the N-myc Oncogene Display Different Developmental Phenotypes

Abstract

Being genetically homogeneous, clonal cell lines are potentially important for investigating many aspects of cellular differentiation. We describe here the creation of clonal cell lines by immortalization of neuronal precursor cells from the adult mouse olfactory epithelium. Unlike neurons elsewhere in the vertebrate nervous system, the olfactory sensory neuron can be replaced throughout the lifespan of the animal. However, little is known about the molecular aspects of olfactory neurogenesis. Continuous cell lines were generated by retroviral transduction of the n-myc proto-oncogene into the mitotically active basal cells of the olfactory epithelium which give rise to the sensory neuron. Twenty-one clonal cell lines were produced which could be divided into three distinct morphological classes: one with flat, epithelial-like cells only; another with round, flat, and bipolar cells; and a third with large flat and large bipolar cells. These morphological classes had different patterns of intermediate filament expression, as shown by immunocytochemistry and immunoblot analysis. All cells in all cell lines expressed the intermediate filament protein vimentin. Most bipolar cells, but not other cell types, expressed neurofilament protein and in one morphological class the bipolar cells co-expressed neurofilament and glial fibrillary acidic protein. Several cell lines expressed mRNA for OMP, a marker of mature olfactory sensory neurons, and GOLF, a guanine nucleotide binding protein involved in olfactory sensory transduction. It is concluded that these cell lines were immortalized from sensory neuron precursors late in the lineage pathway. Other cell lines appear to have been immortalized at earlier stages in the lineage pathway. These cell lines therefore provide useful tools for the investigation of neuronal differentiation and sensory transduction in the olfactory epithelium.