Characterization of aromatase and BLBP-positive radial glial cells in the brain of adult zebrafish

PosterIt is now widely accepted that radial glial cells play a fundamental role in the process of embryonic neurogenesis. In contrast to mammals, radial glial cells are maintained during adulthood in teleost fishes and this persistence is likely to be related to the intense neurogenic activity of the adult fish brain. We and others have recently shown that radial glial cells are progenitor cells capable of generating new neurons in adult zebrafish (Danio rerio). More precisely, we showed that aromatase B (CYP19B, AroB), the synthetic enzyme of estradiol, is strongly expressed in a subset of radial cells, essentially in the forebrain of adult males and females. We also demonstrated that many of these aromatasepositive radial cells have mitotic activity and generate neurons. The purpose of this work is to further characterize cells presenting proliferative activity by looking at other radial cells markers. Among potential markers, BLBP (Brain lipid binding protein) appeared pertinent as it is is highly expressed in the developing central nervous system of mammals and considered as a marker of radial glial cells and immature astrocytes. BLBP (Fabp7 or BFABP) is a brain specific member of the large family of hydrophobic ligand-binding protein (Fatty Acid Binding Proteins: FABPs). In the present study, we compare the expression of BLBP in radial glial cells of the zebrafish with that of AroB using immunohistochemistry. The data showed that BLBP is highly expressed in radial glial cells of the entire brain. In the regions where AroB is strongly expressed, there is a good correlation between the distribution of AroB-positive and BLBP-positive radial glial cells. Double staining for AroB and BLBP showed that most of radial glial cells of the forebrain coexpress the two markers; however, some express only one. We also performed double staining with BLBP and PCNA (Proliferating Cell Nuclear Antigen). Data showed that most BLBP-positive radial glial cells are also PCNA-positive cells, suggesting that the BLBP-positive cells are able to divide. The in vivo data presented here extend previously published data on radial glial markers in adult fish and demonstrate that BLBP is an excellent marker of radial glial cells of the zebrafish adult brain. Nevertheless, the present data suggest that heterogeneity occurs within the radial glial cell population. A more detailed study is thus needed to further characterize the phenotype of mitotically-active radial glial cells in adult fish