Hepatic and extrahepatic expression of vitellogenin genes in the zebrafish, Danio rerio.
ABSTRACT Vitellogenins (Vtgs) are yolk precursor proteins in oviparous species and are cleaved into three portions-lipovitellin I (LVI), phosvitin (PV), and lipovitellin II (LVII)-in oocytes in vertebrates. In the present study, we found that the zebrafish genome contains at least seven vtg genes (vtg1-7) encoding heterogeneous vitellogenins with three distinct types of Vtgs: type I (Vtg1, 4-7) contains all the three major portions but lacks the C-terminal half of LVII; type II (Vtg2) is the only one including intact three portions; type III (Vtg3) lacks both PV and the LVII C-terminal half. The seven vtgs were located in two different chromosomes: one (vtg3) in LG11 and the rest closely linked in LG22, probably arisen from local gene duplication events. All of the seven vtgs are predominantly expressed in female liver and can be induced in male liver by 17beta-estradiol (E2). The level of vtg1 mRNA was about 100x and 1000x higher than those of vtg2 and vtg3 mRNAs. We also found vtg mRNAs in several non-liver tissues, but the expression level is generally <10% of that in the liver. In situ hybridization experiments confirmed that the extrahepatic expression was actually in adipocytes associated with several organs such as the intestine, ovary, and E2-induced testis.
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ABSTRACT: Deep RNA sequencing (RNA-seq) was performed to provide an in-depth view of the transcriptome of red and white skeletal muscle of exercised and non-exercised rainbow trout (Oncorhynchus mykiss) with the specific objective to identify expressed genes and quantify the transcriptomic effects of swimming-induced exercise. Pubertal autumn-spawning seawater-raised female rainbow trout were rested (n = 10) or swum (n = 10) for 1176 km at 0.75 body-lengths per second in a 6,000-L swim-flume under reproductive conditions for 40 days. Red and white muscle RNA of exercised and non-exercised fish (4 lanes) was sequenced and resulted in 15-17 million reads per lane that, after de novo assembly, yielded 149,159 red and 118,572 white muscle contigs. Most contigs were annotated using an iterative homology search strategy against salmonid ESTs, the zebrafish Danio rerio genome and general Metazoan genes. When selecting for large contigs (>500 nucleotides), a number of novel rainbow trout gene sequences were identified in this study: 1,085 and 1,228 novel gene sequences for red and white muscle, respectively, which included a number of important molecules for skeletal muscle function. Transcriptomic analysis revealed that sustained swimming increased transcriptional activity in skeletal muscle and specifically an up-regulation of genes involved in muscle growth and developmental processes in white muscle. The unique collection of transcripts will contribute to our understanding of red and white muscle physiology, specifically during the long-term reproductive migration of salmonids.PLoS ONE 01/2013; 8(1):e53171. · 4.09 Impact Factor
Article: Molecular conservation of estrogen-response associated with cell cycle regulation, hormonal carcinogenesis and cancer in zebrafish and human cancer cell lines.[show abstract] [hide abstract]
ABSTRACT: The zebrafish is recognized as a versatile cancer and drug screening model. However, it is not known whether the estrogen-responsive genes and signaling pathways that are involved in estrogen-dependent carcinogenesis and human cancer are operating in zebrafish. In order to determine the potential of zebrafish model for estrogen-related cancer research, we investigated the molecular conservation of estrogen responses operating in both zebrafish and human cancer cell lines. Microarray experiment was performed on zebrafish exposed to estrogen (17β-estradiol; a classified carcinogen) and an anti-estrogen (ICI 182,780). Zebrafish estrogen-responsive genes sensitive to both estrogen and anti-estrogen were identified and validated using real-time PCR. Human homolog mapping and knowledge-based data mining were performed on zebrafish estrogen responsive genes followed by estrogen receptor binding site analysis and comparative transcriptome analysis with estrogen-responsive human cancer cell lines (MCF7, T47D and Ishikawa). Our transcriptome analysis captured multiple estrogen-responsive genes and signaling pathways that increased cell proliferation, promoted DNA damage and genome instability, and decreased tumor suppressing effects, suggesting a common mechanism for estrogen-induced carcinogenesis. Comparative analysis revealed a core set of conserved estrogen-responsive genes that demonstrate enrichment of estrogen receptor binding sites and cell cycle signaling pathways. Knowledge-based and network analysis led us to propose that the mechanism involving estrogen-activated estrogen receptor mediated down-regulation of human homolog HES1 followed by up-regulation cell cycle-related genes (human homologs E2F4, CDK2, CCNA, CCNB, CCNE), is highly conserved, and this mechanism may involve novel crosstalk with basal AHR. We also identified mitotic roles of polo-like kinase as a conserved signaling pathway with multiple entry points for estrogen regulation. The findings demonstrate the use of zebrafish for characterizing estrogen-like environmental carcinogens and anti-estrogen drug screening. From an evolutionary perspective, our findings suggest that estrogen regulation of cell cycle is perhaps one of the earliest forms of steroidal-receptor controlled cellular processes. Our study provides first evidence of molecular conservation of estrogen-responsiveness between zebrafish and human cancer cell lines, hence demonstrating the potential of zebrafish for estrogen-related cancer research.BMC Medical Genomics 01/2011; 4:41. · 3.69 Impact Factor
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ABSTRACT: In most oviparous animal species, oocyte growth occurs via the uptake of plasma egg yolk precursors, predominantly vitellogenins (Vtg). These glycolipoproteins are members of the large lipid transfer protein superfamily and key players in reproduction. While the vertebrate liver has been demonstrated to synthesize large amounts of Vtg, mostly under 17beta-estradiol control, the ability of other tissues to express significant amounts of Vtg has not been conclusively demonstrated. RT-PCR revealed vtg1 transcripts in female zebrafish and rainbow trout white adipose tissue (WAT). It was also found to coexpress mtp, known to perform the intracellular lipidation of Vtg prior to secretion. The liver and pancreas markers apobb2 and ins, or ela2, respectively, were not expressed in adipocytes. Whole-mount in situ hybridization and in situ RT-PCR tests of histological sections revealed vtg1 signal in adipocytes, whereas no signal was detected in infiltrated pancreatic islets. Transcript expression of vtg1 was induced in WAT of 17beta-estradiol-treated males, and the transcript and corresponding protein were detected in the thin rim of cytoplasm surrounding the adipocyte. Real-time quantitative RT-PCR showed that rainbow trout perivisceral WAT vtg1 transcript levels were high during early compared to late vitellogenesis. Taking normalized mRNA levels and tissue somatic index into account, vtg1 transcript levels at the beginning of oocyte yolk deposition were approximately 45 times lower in WAT than in liver, and these levels were not correlated to plasma Vtg and 17beta-estradiol concentrations. These findings suggest that WAT Vtg is implicated in providing components to the ovary during the early stages of vitellogenesis.Biology of Reproduction 01/2012; 86(2):38. · 4.01 Impact Factor