Medaka genomic BAC clones, which contained two types of medaka hemopexin-like protein gene (Wap65), mWap65-1 and mWap65-2, were screened and their genomic sequences were determined by the shotgun strategy. The exon-intron organizations were highly conserved between both mWap65s and human hemopexin genes. The 5′-flanking regions of mWap65-1 and mWap65-2 contained various putative transcription factor binding sites including elements for developmental regulation. The expression patterns of mWap65s during embryonic development were examined by quantitative real-time PCR, demonstrating that both mWap65 transcripts were observed in early embryonic stages, but their expression patterns were different. Interestingly, in situ hybridization revealed that mWap65-2 transcripts were restricted to liver, whereas mWap65-1 transcripts were detected along the edge of pectoral fin buds and the median fin fold of tail buds in embryos at stage 32. Furthermore, we generated transgenic medaka expressing GFP driven by mWap65-1 and mWap65-2 promoters and observed GFP expression patterns during ontogeny. Although localizations of GFP varied among individuals, embryos uniformly expressed GFP 1 day after injection of mWap65-1-hrGFP and mWap65-2-hrGFP constructs, suggesting that mWap65-1 and mWap65-2 promoters were activated in very early stages. The differences between mWap65-1 and mWap65-2 in their expression profiles indicate their distinct roles during ontogeny.
We cloned a full-length cDNA encoding vitellogenin (VTG) from a marine teleost, the Japanese sillago Sillago japonica. The cloned sillago VTG contained signal peptide, lipovitellin heavy chain, phosvitin, lipovitellin light chain, and beta'-component in the order from the N-terminus. An exposure to 17beta-estradiol significantly increased the levels of plasma VTG, but not hepatic VTG mRNA in males. Neither plasma VTG nor hepatic VTG mRNA levels were affected by the exposure to 4-tert-octylphenol. Hepatic VTG mRNA levels in males increased at 1 day after intraperitoneal administration of 17beta-estradiol but decreased in the subsequent 5 days. However, plasma VTG levels remained high for 5 days after administration, suggesting that the accumulation period of plasma VTG is longer than that of hepatic VTG mRNA in males. Therefore, VTG mRNA may be a suitable indicator of temporal exposure to estrogenic chemicals in the environment, whereas plasma VTG is useful to detect consecutive exposure.
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