Lindsey, B.W., Darabie, A., and Tropepe, V. (2012) The cellular composition of neurogenic periventricular zones in the adult zebrafish forebrain. The Journal of comparative neurology. 520(10):2275-2316.
A central goal of adult neurogenesis research is to characterize the cellular constituents of a neurogenic niche and to understand how these cells regulate the production of new neurons. Since the generation of adult-born neurons may be tightly coupled to their functional requirement, the organization and output of neurogenic niches may vary across different regions of the brain or between species. We have undertaken a comparative study of six (D, Vd, Vv, Dm, Dl, Ppa) periventricular zones (PVZ) harbouring proliferative cells present in the adult forebrain of the zebrafish (Danio rerio); a species known to possess widespread neurogenesis throughout life. Using electron microscopy we have documented for the first time the detailed cytoarchitecture of these zones, and propose a model of the cellular composition of pallial and subpallial PVZs, and a classification scheme for identifying morphologically distinct cell types. Immunolabelling of resin embedded tissue confirmed the phenotype of three constitutively proliferating (BrdU+) cell populations, including a radial glial-like (Type IIa) cell immunopositive for both S100β and GS. Our data revealed rostrocaudal differences in the density of distinct proliferative populations and cumulative labelling studies suggested that the cell cycle kinetics of these populations are not uniform between PVZs. While the peak number of differentiated neurons were generated after <2 weeks among most PVZs, niche-specific decline in the number of newborn neurons in some regions occurred after 4 weeks. Our data suggest that the cytoarchitecture of neurogenic niches and the tempo of neuronal production are regionally distinct in the adult zebrafish forebrain.