Widespread expression of rat collapsin response-mediated protein 4 in the telencephalon and other areas of the adult rat central nervous system

The rat collapsin response-mediated protein 4 (rCRMP-4) is a member of a fa mily of proteins that are involved in axonal growth. It is found transientl y in postmitotic neurons, such as those that are generated in the adult hip pocampus. The authors used immunocytochemistry to investigate whether areas of the rat central nervous system (CNS) that retain postnatal neurogenesis express this protein. They found pronounced rCRMP-4 immunoreactivity in re cently generated cells in the dentate granular layer, the subventricular zo ne, the olfactory bulbs, and the rostral migratory stream, four areas in wh ich the production or migration of neurons occurs in adulthood. However, rC RMP-4 immunoreactivity also is expressed in many other regions of the rat b rain in which there is no record of adult neurogenesis or neuronal migratio n, e.g., in the olfactory glomeruli and in neurons of the cerebral cortex. In the hypothalamus, intensely rCRMP-4-labeled neurons populated the suprao ptic, paraventricular, and periventricular nuclei as well as the median emi nence and the arcuate nucleus. Immunoreactivity for rCRMP-4 also was presen t in certain neurons of the interpeduncular nucleus, median raphe, superior colliculus, and scattered granule cerebellar neurons. Many of these region s are known to display axonal outgrowth and/or synaptic rearrangement in ad ulthood and to coexpress the polysialylated form of the neural cell adhesio n molecule. Thus, the results of this study suggest that rCRMP-4 expression in the CNS is associated with cells that are migrating or are undergoing a xonal growth. Nevertheless, small, rCRMP-4-immunoreactive cells were seen t hroughout the brain. These cells did not express neuronal, astroglial, or m icroglial markers, although some of them also were immunoreactive for rip a ntibody, suggesting an oligodendroglial lineage. (C) 2000 Wiley-Liss,Inc.