Journal of Neuroscience, Vol 6, 208-217, Copyright © 1986 by Society for Neuroscience
Neurons of the olfactory epithelium in adult rats contain vimentin
JE Schwob, NB Farber and DI Gottlieb
In the developing nervous system, the intermediate filament protein
vimentin is found in the proliferating neuroepithelium and neural crest. As
development proceeds, postmitotic neurons cease vimentin expression and
neurofilament proteins begin to accumulate. We have shown that olfactory
receptor neurons deviate from the general pattern of neuronal intermediate
filament expression, in that they continue to express vimentin or a highly
vimentin-like protein rather than neurofilament proteins in the adult rat.
With light-microscopic immunohistochemistry, three independently derived
antibodies to vimentin label all portions of the primary olfactory
projection, including the sensory neuron cell bodies in the olfactory
epithelium, the fascicles of the olfactory nerve, and their axonal arbors
in the glomeruli of the olfactory bulb. In contrast, anti-neurofilament
antisera stain only rare scattered receptor cells and a small number of
axons in the olfactory nerve. Electron-microscopic immunohistochemistry
shows dense staining of olfactory axons with anti-vimentin. The
vimentin-like immunoreactive material in the olfactory nerve layer was
characterized by SDS-PAGE and by immunoblotting. On immunoblots of
homogenates of the olfactory nerve, the anti-vimentin monoclonal antibody
SBV-21 (Blose et al., 1984) stains only a single protein of Mr = 55 kDa.
This band comigrates with vimentin in crude cytoskeletal material from the
neonatal rat brain prepared according to the method of Dahl et al. (1981).
SBV-21 does not stain neurofilament triplet proteins or glial fibrillary
acidic protein, which are also present in these blots. These results
demonstrate that the vast majority of olfactory receptor neurons and their
axons contain vimentin or a protein of similar immunological character and
electrophoretic mobility, while identifiable expression of neurofilament
proteins is confined to a very small subpopulation. Hence, the switch in
intermediate filament proteins that normally accompanies neuronal
maturation is arrested in most olfactory neurons, and a "juvenile"
biochemical marker is retained. This population of neurons is also unique
among mammalian neurons in several other respects, including that olfactory
neurons die during normal adult life or following injury and then are
replaced from a proliferating pool of stem cells.