title: Aromatase in the brain of teleost fish: expression, regulation and putative functions.
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 tg(cyp19a1b-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.
authors.affiliation: Neurogenesis And OEstrogens, UMR CNRS 6026, IFR 140, Université de Rennes 1, Rennes, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Diotel
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Page
authors.forename: Karen
authors.initials: K
authors.lastname: Mouriec
authors.forename: Sok-Keng
authors.initials: SK
authors.lastname: Tong
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Pellegrini
authors.forename: Colette
authors.initials: C
authors.lastname: Vaillant
authors.forename: Isabelle
authors.initials: I
authors.lastname: Anglade
authors.forename: François
authors.initials: F
authors.lastname: Brion
authors.forename: Farzad
authors.initials: F
authors.lastname: Pakdel
authors.forename: Bon-chu
authors.initials: BC
authors.lastname: Chung
authors.forename: Olivier
authors.initials: O
authors.lastname: Kah
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001921:Brain / Q000201:enzymology*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000201:enzymology; D005399:Fishes; D005786:Gene Expression Regulation; D006066:Gonads / Q000201:enzymology; D008969:Molecular Sequence Data; D055495:Neurogenesis; D010802:Phylogeny; D011960:Receptors, Estrogen / Q000378:metabolism; D012621:Seasons; D012733:Sex Differentiation; D012726:Sexual Behavior, Animal; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism
chemical_list: D011960:Receptors, Estrogen; D001141:Aromatase; D013254:Steroid 17-alpha-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme