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Expression of estrogen receptor-alpha and -beta mRNA in the brain of Japanese quail embryos
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
2007 (English)In: Developmental Neurobiology, ISSN 1932-8451, Vol. 67, no 13, 1742-1750 p.Article in journal (Refereed) Published
Abstract [en]

The present study was conducted to investigate the mRNA expression of the two estrogen receptor (ER) subtypes ERα and ERβ in the brain of Japanese quail embryos. We found expression of both ERα and ERβ mRNA in homogenate of whole head from 6-day-old embryos, and in brain homogenate from 9- and 12-day-old embryos using real-time PCR. In 9- and 12-day-old embryos the ERα expression was higher in females than in males. We used in situ hybridization to examine the localization of the ERs in sections from male and female brains on day 9 and day 17 of incubation. On day 9, ERβ mRNA was detected in the developing medial preoptic nucleus (POM), in the medial part of the bed nucleus of the striae terminalis (BSTm), and in the tuberal region of the hypothalamus. ERα signal could not be detected in the POM, the BSTm or the tuberal region in 9-day-old embryos. In 17-day-old embryos, ERβ was highly expressed in the preoptic area, the nucleus Taeniae of the Amygdala (TnA) and the BSTm. Expression of ERα mRNA was detected in parts of the preoptic area and in the telencephalic TnA. No ERα expression was found in the BSTm, an area known to be sexually dimorphic in adults. The high embryonic expression of ERβ in brain areas linked to sexual behavior indicates that ERβ plays a role in sexual differentiation of the Japanese quail brain.

Place, publisher, year, edition, pages
2007. Vol. 67, no 13, 1742-1750 p.
Keyword [en]
Japanese quail, estrogen receptors, embryo brain, real-time PCR, sexual differentiation
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96944DOI: 10.1002/dneu.20544ISI: 000250606300005PubMedID: 17638389OAI: oai:DiVA.org:uu-96944DiVA: diva2:171688
Available from: 2008-03-28 Created: 2008-03-28 Last updated: 2012-02-03
In thesis
1. Differentiation of Brain and Reproductive Organs in Birds: Effects of Environmental Contaminants
Open this publication in new window or tab >>Differentiation of Brain and Reproductive Organs in Birds: Effects of Environmental Contaminants
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The first objective of this thesis was to investigate effects of endocrine disruptors on the developing brain and gonads of bird embryos. The substances studied were the insecticide methoxychlor, and nine UV-filters (3-benzylidene camphor (3BC), 4 methyl benzylidene camphor (4MBC), benzophenone (BP) 1,2 and 3, 4 hydroxy benzophenone (4 HB), 4 dihydroxy benzophenone (4DHB), benzyl salicylate (BS), and ethyl-4-aminobenzoate Et-PABA)), commonly used in cosmetic products. Some of these substances have no estrogenic effect in vitro, but have been shown to be estrogenic in vivo. The PCB-mixture Clophen A50 is a well-known inducer of biotransformation enzymes and was co-administered with methoxychlor and the UV-filters 3BC and 4MBC.

Exposure to 3BC or 4MBC caused ovotestis formation and malformations of the Müllerian ducts in Japanese quail embryos. Co-exposure to one of these compounds and Clophen A50 enhanced the effects, indicating that Clophen A50 potentiates the effects of the UV-filters. Embryonic co-exposure to Clophen A50 and methoxychlor caused a disturbed male sexual behaviour. The metabolites of methoxychlor are estrogen receptor (ER)α-selective, which indicates that the effects on behaviour following embryonic treatment were mediated by ERα.

Another objective in this thesis was to localize estrogen receptors (ERs) in the brain of adult and embryonic Japanese quail. The ER localization provides a basis for mechanistic studies on effects of endocrine disruptors, by the identification of estrogen-responsive areas in the brain. We found that ERβ, not previously implicated in sex-differentiation of the brain, was the only ER-subtype present in a sexually dimorphic brain area during differentiation.

In conclusion, the estrogenic effects of 3BC, 4MBC and methoxychlor were increased by co-exposure to PCB. These results raise concern since many wildlife species, as well as humans, carry large body burdens of persistent organic pollutants like PCBs, which potentially can interact and enhance the effects of other endocrine disruptors.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 414
Keyword
Zoophysiology, Bird, endocrine disruption, estrogen receptor, methoxychlor, UV-filter, sexual behavior, ovotestis, Zoofysiologi
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-8592 (URN)978-91-554-7141-5 (ISBN)
Public defence
2008-04-19, Lindahlsalen, Evolutionsbiologiskt Centrum, Norbyvägen 18A, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2008-03-28 Created: 2008-03-28 Last updated: 2009-04-03Bibliographically approved
2. Roles of ERα and ERβ in Normal and Disrupted Sex Differentiation in Japanese Quail
Open this publication in new window or tab >>Roles of ERα and ERβ in Normal and Disrupted Sex Differentiation in Japanese Quail
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Exposure to xenoestrogens during development has been shown to impair sexual differentiation in various species. The major aim of this thesis was to elucidate the respective roles of the two estrogen receptors ERα and ERβ in normal and disrupted differentiation of sex organs and copulatory behavior in the Japanese quail (Coturnix japonica). The expression of ERα mRNA was much stronger than that of ERβ mRNA in the gonads and Müllerian ducts (embryonic oviducts) in early embryos. By contrast, ERβ seemed to be predominantly expressed in regions of the embryonic brain that are associated with male sexual behavior. Embryos were exposed to the selective ERα agonists propyl-pyrazole-triol (PPT) and 16α-lactone-estradiol (16α-LE2). The estrogens 17β-estradiol (E2) and 17α-ethynylestradiol (EE2), which activate both ERα and ERβ, were used as positive controls. All substances impaired reproductive organ differentiation. The effects observed included oviductal malformations in females and partial development of oviducts in males. All substances also induced testis feminization (ovotestis) in male embryos. The male copulatory behavior was severely impaired by the positive controls but was unaffected by PPT and 16α-LE2 at doses that disrupted sex organ differentiation. A higher dose of 16α-LE2 significantly suppressed the behavior. However, it is possible that this effect was caused by cross-activation of ERβ. The substances also induced hepatic expression of mRNA encoding the egg-yolk proteins vitellogenin II and very low-density apolipoprotein II, which are commonly used as indicators of estrogen exposure. In conclusion, the results suggest that ERα is important for female reproductive organ differentiation. Excess activation of ERα by xenoestrogens impairs differentiation in both females and males and induces hepatic expression of egg-yolk proteins. The results also indicate that ERα alone cannot mediate demasculinization of male copulatory behavior in quail, although further studies are needed to test this hypothesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 445
Keyword
Toxicology, sex differentiation, estrogen receptor, sexual behavior, endocrine disruption, Japanese quail, Toxikologi
Identifiers
urn:nbn:se:uu:diva-8921 (URN)978-91-554-7232-0 (ISBN)
Public defence
2008-06-12, Lindahlsalen, Evolutionsbiologiskt centrum (EBC), Norbyvägen 18A, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2010-01-07Bibliographically approved

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