Aromatase and Estrogens: Involvement in Constitutive and Regenerative Neurogenesis in Adult Zebrafish

Unlike that of mammals, the brain of adult teleost fish exhibits some unique features, such as a strong aromatase activity, an intense neurogenesis and a high capability for brain repair. In the last few years, zebrafish have become a well-recognized model for studying adult neurogenesis and brain regeneration. Interestingly, in the zebrafish brain, the estrogen-synthesizing enzyme (aromatase B) is only expressed in radial glial cells acting as neural “stem” cells. It suggests key roles for aromatase and estrogens in brain cell proliferation, differentiation, migration and survival. Here, we document the unique features exhibited by the brains of fish, focusing on the zebrafish. We discuss neurosteroid synthesis and signaling in zebrafish brain, and the potential roles of aromatase and estrogens in constitutive and regenerative neurogenesis. We emphasize and confront these data with respect to what was reported concerning mammalian and nonmammalian models, with a special focus on amphibians.