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Molecular cloning and characterization of ligand- and species-specificity of amphibian estrogen receptors |
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| Authors: | Yoshinao Katsu Ena Taniguchi Shinichi Miyagawa Kaoru Kubokawa Tomohiro Oka Jan Myburgh Taisen Iguchi |
| Institution: | a Okazaki Institute for Integrative Bioscience, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan b Department of Biological Science, Faculty of Life and Environmental Sciences, Shimane University, Matsue 690-0823, Japan c Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, Hiroshima 739-8526, Japan d Center for Advanced Marine Sciences, Ocean Research Institute, University of Tokyo, Nakano, Tokyo 164-8639, Japan e Institute of Environmental Ecology, IDEA Consultants, Inc., Shizuoka 421-0212, Japan f Center of Chemical Management and Information, Department of Environmental Business and Technology, Japan Environmental Management Association for Industry (JEMAI), Chiyoda-ku, Tokyo 101-0044, Japan g Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag 04, Onderstepoort 0110, Republic of South Africa |
| Abstract: | Estrogens are essential for normal reproductive activity in both males and females as well as for ovarian differentiation during a critical developmental stage in most vertebrates. To understand the molecular mechanisms of estrogen action and to evaluate estrogen receptor ligand interactions in amphibians, we isolated cDNAs encoding the estrogen receptors (ERα and ERβ) from the Japanese firebelly newt (Cynops pyrrhogaster), Tokyo salamander (Hynobius tokyoensis), axolotl (Ambystoma mexicanum), and Raucous toad (Bufo rangeri). Full-length amphibian ER cDNAs were obtained using 5′ and 3′ rapid amplification of cDNA ends. The predicted amino acid sequences of these amphibian ERs showed a high degree of amino acid sequence identity (over 70%) to each other. We analyzed the relationships of these amphibian ER sequences to other vertebrate ER sequences by constructing a phylogenetic tree. We verified that these were bona fide estrogen receptors using receptor dependent reporter gene assays. We analyzed the effects of natural estrogens, ethinylestradiol, and DDT and its metabolites on the transactivation of the four amphibian species listed above, and Xenopus tropicalis ERs and found that there were species-specific differences in the sensitivity of these ERs to hormones and environmental chemicals. These findings will expand our knowledge of endocrine-disrupting events in amphibians. |
| Keywords: | Estrogen receptor Amphibian Transactivation Ligand-specificity Ethinylestradiol DDT |
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