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Advisor(s)
Abstract(s)
Estrogen actions are mainly mediated by specific nuclear estrogen receptors (ERs), for which different genes
and a diversity of transcript variants have been identified, mainly in mammals. In this study, we investigated
the presence of ER splice variants in the teleost fish gilthead sea bream (Sparus auratus), by comparison with
the genomic organization of the related species Takifugu rubripes. Two exon2-deleted ERα transcript variants
were isolated from liver cDNA of estradiol-treated fish. The ΔE2 variant lacks ERα exon 2, generating a
premature termination codon and a putative C-terminal truncated receptor, while the ΔE2,3* variant contains
an in-frame deletion of exon 2 and part of exon 3 and codes for a putative ERα protein variant lacking most of
the DNA-binding domain. Both variants were expressed at very low levels in several female and male sea
bream tissues, and their expression was highly inducible in liver by estradiol-17β treatment with a strong
positive correlation with the typical wild-type (wt) ERα response in this tissue. These findings identify
novel estrogen responsive splice variants of fish ERα, and provide the basis for future studies to investigate
possible modulation of wt-ER actions by splice variants.