Region-specific expression of cell cycle inhibitors in the adult brain

In the adult brain, neural proliferation is almost absent and neurons are generally not renewed. By contrast, in the olfactory organ, olfactory neurons are produced continuously throughout life. To investigate whether specific cell cycle inhibitors are involved in the control of neural quiescence in adulthood, we compared their expression either in different regions of the adult brain weakly or non neurogenic or, for comparison, in the olfactory mucosa. We show that numerous cell cycle inhibitors are expressed in the adult brain either in an ubiquitous fashion (as p191nk4d) or in specific brain regions (p15lnk4b in the forebrain, p27Kip1 and p21Cip1 in the cerebellum). By contrast p18lnk4c was expressed detectably only in the highly neurogenic olfactory epithelium. The present data suggest that various CDK inhibitors may be involved in a region-specific fashion in the maintenance of nerve cell quiescence in adults. NeuroReport 12:3127-3131 (C) 2001 Lippincott Williams & Wilkins.