Abstract
Olfactory neurons are replaced in the adult olfactory epithelium by division and differentiation of cells close to the basement membrane of the olfactory epithelium. Among the basal cells is a stem cell which undergoes an asymmetric division, giving rise to a new stem cell and a precursor cell. The precursor cell divides again symmetrically and there may be additional symmetrical divisions before the progeny leave the cell cycle to differentiate [1]. We report here the characterization of cell lines created by retroviral insertion of the n-myc proto-oncogene into dividing cells of the adult mouse olfactory epithelium [2]. We have approximately 60 cell lines generated by this procedure, many of them cloned by single cell micromanipulation. These clones are heterogeneous in morphology but they fall into three broad categories: class 1 are mainly flat, epithelial-like cells; class 2 are a mixture of epithelial-like cells, round cells, and bipolar cells with short processes; and class 3 are a mixture of very large epithelial-like cells and bipolar cells with very long processes. Due to the slow growth of the class 3 cell lines and the difficulty of cloning them, we have concentrated our analysis on the class 1 and class 2 cells. Expression of neural and non-neural proteins was studied with a combination of immunocytochemistry, Western analysis, and reverse transcriptase polymerase chain reaction (RT-PCR). All cell lines express vimentin and keratin. Class 1 cell lines failed to express any neural cell markers when grown under our standard growth conditions (10% fetal calf serum, Dulbecco’s modified Eagle’s medium (DMEM), 5% CO2). Class 2 cell lines expressed a variety of neuronal proteins (neurofilament, 13tubulin, MAP-2, NCAM), although not all cell lines expressed all markers. Some clonal cell lines expressed the intermediate filament protein of glial cells (GFAP) in addition to neurofilament.
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