Aromatase in the brain of teleost fish: expression, regulation and putative functions.Report as inadecuate

Aromatase in the brain of teleost fish: expression, regulation and putative functions. - Download this document for free, or read online. Document in PDF available to download.

* Corresponding author 1 ICM - Interactions cellulaires et moléculaires 2 IMB Sinica - Institute of Molecular Biology 3 INERIS - Institut National de l-Environnement Industriel et des Risques

Abstract : Unlike that of mammals, the brain of teleost fish exhibits an intense aromatase activity due to the strong expression of one of two aromatase genes aromatase A or cyp19a1a and aromatase B or cyp19a1b that arose from a gene duplication event. In situ hybridization, immunohistochemistry and expression of GFP green fluorescent protein in transgenic tgcyp19a1b-GFP fish demonstrate that aromatase B is only expressed in radial glial cells RGC of adult fish. These cells persist throughout life and act as progenitors in the brain of both developing and adult fish. Although aromatase B-positive radial glial cells are most abundant in the preoptic area and the hypothalamus, they are observed throughout the entire central nervous system and spinal cord. In agreement with the fact that brain aromatase activity is correlated to sex steroid levels, the high expression of cyp19a1b is due to an auto-regulatory loop through which estrogens and aromatizable androgens up-regulate aromatase expression. This mechanism involves estrogen receptor binding on an estrogen response element located on the cyp19a1b promoter. Cell specificity is achieved by a mandatory cooperation between estrogen receptors and unidentified glial factors. Given the emerging roles of estrogens in neurogenesis, the unique feature of the adult fish brain suggests that, in addition to classical functions on brain sexual differentiation and sexual behaviour, aromatase expression in radial glial cells could be part of the mechanisms authorizing the maintenance of a high proliferative activity in the brain of fish.

Keywords : Aromatase cyp19a1b Estrogen synthase Radial glial cells Estrogen receptors Androgens Neurogenesis Sexual behaviour Neurosteroids

Author: Nicolas Diotel - Yann Le Page - Karen Mouriec - Sok-Keng Tong - Elisabeth Pellegrini - Colette Vaillant - Isabelle Anglade - Fran



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