Progenitor radial cells and neurogenesis in pejerrey fish forebrain

The central nervous system of adult teleost fish is peculiar because of the following features: (1) the persistence of radial glial cells, (2) an important neurogenic activity and (3) a high aromatase expression by radial cells. In this study, the proliferative zones of the forebrain were described using bromodeoxyuridine (BrdU) treatment in the brain of the pejerrey, an Acanthopterygian teleost fish. These cells were shown to have morphological and immunoreactive characteristics of radial cells and to express aromatase. Three different progenitor populations were identified based on the mobility and proliferation capacity 6 weeks after BrdU treatment: transit amplifying progenitors, slowly proliferating stem cells, and cells remaining in the proliferative zones showing no signs of mitotic activity. The proliferative cells were always located in the ventricular zone and were never observed in the brain parenchyma; however, 3 weeks later they were found away from these proliferative zones and displayed acetylated tubulin immunoreactivity. Other BrdU-positive cells showed astrocyte morphology and were immunoreactive to the S100 glial marker. These results show that in this fish, radial cells are true progenitors generating neurons and possibly astrocytes.