Journal article
The complete nuclear estrogen receptor family in the rainbow trout: Discovery of the novel ERα2 and both ERβ isoforms
Gene, Vol.392(1), pp.164-173
2007
Handle:
https://hdl.handle.net/2376/113211
PMCID: PMC1868691
PMID: 17307310
Abstract
Estrogen hormones interact with cellular
ERs to exert their biological effects in vertebrate animals. Similar to other animals, fishes have two distinct
ER subtypes,
ERα (NR3A1) and
ERβ (NR3A2). The
ERβ subtype is found as two different isoforms in several fish species because of a gene duplication event. Although predicted, two different isoforms of
ERα have not been demonstrated in any fish species. In the rainbow trout (
Oncorhynchus mykiss), the only
ER described is an isoform of the
ERα subtype (i.e.
ERα1, NR3A1a). The purpose of this study was to determine whether the gene for the other
ERα isoform,
ERα2 (i.e., NR3A1b), exists in the rainbow trout. A RT-PCR and cloning strategy, followed by screening a rainbow trout BAC library yielded a unique DNA sequence coding for 558 amino acids. The deduced amino acid sequence had a 75.4% overall similarity to
ERα1. Both the rainbow trout
ERβ subtypes,
ERβ1 [NR3A2a] and
ERβ2, [NR3A2b] which were previously unknown in this species, were also sequenced as part of this study, and the amino acid sequences were found to be very different from the
ERαs (∼
40% similarity).
ERβ1 and
ERβ2 had 594 and 604 amino acids, respectively, and had 57.6% sequence similarity when compared to one another. This information provides what we expect to be the first complete nuclear
ER gene family in a fish. A comprehensive phylogenetic analysis with all other known fish
ER gene sequences was undertaken to understand the evolution of fish
ERs. The results show a single
ERα subtype clade, with the closest relative to rainbow trout
ERα2 being rainbow trout
ERα1, suggesting a recent, unique duplication event to create these two isoforms. For the
ERβ subtype there are two distinct subclades, one represented by the
ERβ1 isoform and the other by the
ERβ2 isoform. The rainbow trout
ERβ1 and
ERβ2 are not closely associated with each other, but instead fall into their respective
ERβ subclades with other known fish species. Real-time RT-PCR was used to measure the mRNA levels of all four
ER isoforms (
ERα1,
ERα2,
ERβ1, and
ERβ2) in stomach, spleen, heart, brain, pituitary, muscle, anterior kidney, posterior kidney, liver, gill, testis and ovary samples from rainbow trout. The mRNAs for each of the four
ERs were detected in every tissue examined. The liver tended to have the highest
ER mRNA levels along with the testes, while the lowest levels were generally found in the stomach or heart. The nuclear
ERs have a significant and ubiquitous distribution in the rainbow trout providing the potential for complex interactions that involve the functioning of many organ systems.
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Details
- Title
- The complete nuclear estrogen receptor family in the rainbow trout: Discovery of the novel ERα2 and both ERβ isoforms
- Creators
- James J Nagler - Department of Biological Sciences, University of Idaho, Moscow, ID, 83844-3051, USATim Cavileer - Department of Biological Sciences, University of Idaho, Moscow, ID, 83844-3051, USAJack Sullivan - Department of Biological Sciences, University of Idaho, Moscow, ID, 83844-3051, USADaniel G Cyr - INRS–Institut Armand-Frappier, Université du Québec, 245 Boulevard Hymus, Pointe-Claire, QC, Canada H9R 1G6Caird Rexroad - USDA/ARS National Center for Cool and Cold Water Aquaculture, 11876 Leetown Road, Kearneysville, WV, 25430, USA
- Publication Details
- Gene, Vol.392(1), pp.164-173
- Academic Unit
- UNKNOWN
- Publisher
- Elsevier B.V
- Identifiers
- 99900547988701842
- Language
- English
- Resource Type
- Journal article