Multiple structurally distinct ER alpha mRNA variants in zebrafish are differentially expressed by tissue type, stage of development and estrogen exposure

作者：Cotter Kellie A; Yershov Anya; Novillo Apolonia; Callard Gloria V^*

来源：General and Comparative Endocrinology, 2013, 194: 217-229.

DOI：10.1016/j.ygcen.2013.09.014

• Estrogen receptor alpha
• mRNA variants
• Zebrafish
• Alternative splicing
• Endocrine disruption

It is well established that estrogen-like environmental chemicals interact with the ligand-binding site of estrogen receptors (ERs) to disrupt transcriptional control of estrogen responsive targets. Here we investigate the possibility that estrogens also impact splicing decisions on estrogen responsive genes, such as that encoding ER alpha itself. Targeted PCR cloning was applied to identify six ER alpha mRNA variants in zebrafish. Sequencing revealed alternate use of transcription and translation start sites, multiple exon deletions, intron retention and alternate polyadenylation. As determined by quantitative (q)PCR, N-terminal mRNA variants predicting long (ER alpha(L)) and short (ER alpha(S)) isoforms were differentially expressed by tissue-type, sex, stage of development and estrogen exposure. Whereas ER alpha(L) mRNA was diffusely distributed in liver, brain, heart, eye, and gonads, ER alpha(S) mRNA was preferentially expressed in liver (female > male) and ovary. Neither ER alpha(L) nor ER alpha(S) transcripts varied significantly during development, but 17 beta-estradiol selectively increased accumulation of ER alpha(S) mRNA (similar to 170-fold by 120 hpf), an effect mimicked by bisphenol-A and diethylstilbestrol. Significantly, a C-truncated variant (ER alpha(S)-Cx) lacking most of the ligand binding and AF-2 domains was transcribed exclusively from the short isoform promoter and was similar to ER alpha(S) in its tissue-, stage- and estrogen inducible expression. These results support the idea that promoter choice and alternative splicing of the esr1 gene of zebrafish are part of the autoregulatory mechanism by which estrogen modulates subsequent ER alpha expression, and further suggest that environmental estrogens could exert some of their toxic effects by altering the relative abundance of structurally and functionally distinct ER alpha isoforms.

• 出版日期2013-12-1