title: Aromatase, estrogen receptors and brain development in fish and amphibians.
abstract: Estrogens affect brain development of vertebrates, not only by impacting activity and morphology of existing circuits, but also by modulating embryonic and adult neurogenesis. The issue is complex as estrogens can not only originate from peripheral tissues, but also be locally produced within the brain itself due to local aromatization of androgens. In this respect, teleost fishes are quite unique because aromatase is expressed exclusively in radial glial cells, which represent pluripotent cells in the brain of all vertebrates. Expression of aromatase in the brain of fish is also strongly stimulated by estrogens and some androgens. This creates a very intriguing positive auto-regulatory loop leading to dramatic aromatase expression in sexually mature fish with elevated levels of circulating steroids. Looking at the effects of estrogens or anti-estrogens in the brain of adult zebrafish showed that estrogens inhibit rather than stimulate cell proliferation and newborn cell migration. The functional meaning of these observations is still unclear, but these data suggest that the brain of fish is experiencing constant remodeling under the influence of circulating steroids and brain-derived neurosteroids, possibly permitting a diversification of sexual strategies, notably hermaphroditism. Recent data in frogs indicate that aromatase expression is limited to neurons and do not concern radial glial cells. Thus, until now, there is no other example of vertebrates in which radial progenitors express aromatase. This raises the question of when and why these new features were gained and what are their adaptive benefits. This article is part of a Special Issue entitled: Nuclear receptors in animal development.
authors.affiliation: Research Institute in Health, Environment and Occupation, INSERM U1085, SFR Biosit, Université de Rennes 1, Campus de Beaulieu, 35 042 Rennes cedex, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Coumailleau
authors.affiliation: Research Institute in Health, Environment and Occupation, INSERM U1085, SFR Biosit, Université de Rennes 1, Campus de Beaulieu, 35 042 Rennes cedex, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Pellegrini
authors.affiliation: Área de Bioloxía Celular, Departamento de Bioloxía Celular e Ecoloxía, Campus Vida, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: Fátima
authors.initials: F
authors.lastname: Adrio
authors.affiliation: Groupe d'Etude sur l'Inflammation Chronique et l'Obésité (GEICO EA 4516), Faculté des Sciences et Technologies, 15 av René Cassin, BP 7151, 97715 Saint Denis, La Réunion, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Diotel
authors.affiliation: Research Institute in Health, Environment and Occupation, INSERM U1085, SFR Biosit, Université de Rennes 1, Campus de Beaulieu, 35 042 Rennes cedex, France.
authors.forename: Joel
authors.initials: J
authors.lastname: Cano-Nicolau
authors.affiliation: Research Institute in Health, Environment and Occupation, INSERM U1085, SFR Biosit, Université de Rennes 1, Campus de Beaulieu, 35 042 Rennes cedex, France.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Nasri
authors.affiliation: Research Institute in Health, Environment and Occupation, INSERM U1085, SFR Biosit, Université de Rennes 1, Campus de Beaulieu, 35 042 Rennes cedex, France.
authors.forename: Colette
authors.initials: C
authors.lastname: Vaillant
authors.affiliation: Research Institute in Health, Environment and Occupation, INSERM U1085, SFR Biosit, Université de Rennes 1, Campus de Beaulieu, 35 042 Rennes cedex, France. Electronic address: olivier.kah@univ-rennes1.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Kah
mesh_terms: D000663:Amphibians / Q000196:embryology* / Q000235:genetics; D000818:Animals; D001141:Aromatase / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000196:embryology* / Q000502:physiology; D004625:Embryo, Nonmammalian; D052244:Endocrine Disruptors / Q000494:pharmacology; D005399:Fishes / Q000196:embryology* / Q000235:genetics; D055495:Neurogenesis / Q000187:drug effects / Q000235:genetics; D009457:Neuroglia / Q000502:physiology; D011960:Receptors, Estrogen / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics
chemical_list: D052244:Endocrine Disruptors; D011960:Receptors, Estrogen; D001141:Aromatase
keywords: Aromatase; Estrogen receptor; Neurogenesis; Radial glia; Xenopus laevis; Zebrafish