1
|
Validation of reference genes for expression analysis in a teleost fish (Catla catla Hamilton) exposed to an endocrine-disrupting chemical, bisphenol-A. RENDICONTI LINCEI-SCIENZE FISICHE E NATURALI 2017. [DOI: 10.1007/s12210-017-0653-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
2
|
Quesada-García A, Encinas P, Valdehita A, Baumann L, Segner H, Coll JM, Navas JM. Thyroid active agents T3 and PTU differentially affect immune gene transcripts in the head kidney of rainbow trout (Oncorynchus mykiss). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 174:159-168. [PMID: 26963519 DOI: 10.1016/j.aquatox.2016.02.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 02/16/2016] [Accepted: 02/20/2016] [Indexed: 06/05/2023]
Abstract
In mammals, numerous reports describe an immunomodulating effect of thyroid-active compounds. In contrast, only few reports have been published on this subject in fish. We previously demonstrated that immune cells of rainbow trout (Oncorhynchus mykiss) possess thyroid hormone receptors (THRs) and that exposure of trout to the thyroid hormone 3,3',5-triiodo-l-thyronine (T3) or the antithyroid drug propylthiouracil (PTU) alters immune cell transcript levels of THR and several immune genes. The present study aims to further characterize the immunomodulating action of thyroid-active compounds in trout immune cells. We report here the use of a custom-designed 60-mer oligo immune-targeted microarray for rainbow trout to analyze the gene expression profiles induced in the head kidney by T3 and PTU. Morphometric analyses of the thyroid showed that PTU exposure increased the size of the epithelial cells, whereas T3 induced no significant effects. Both T3 and PTU had diverse and partly contrasting effects on immune transcript profiles. The strongest differential effects of T3 and PTU on gene expressions were those targeting the Mitogen Associated Protein Kinase (MAPK), NFkB, Natural Killer (NK) and Toll-Like Receptor (TLR) pathways, a number of multipath genes (MPG) such as those encoding pleiotropic transcription factors (atf1, junb, myc), as well as important pro-inflammatory genes (tnfa, tnf6, il1b) and interferon-related genes (ifng, irf10). With these results we show for the first time in a fish species that the in vivo thyroidal status modulates a diversity of immune genes and pathways. This knowledge provides the basis to investigate both mechanisms and consequences of thyroid hormone- and thyroid disruptor-mediated immunomodulation for the immunocompetence of fish.
Collapse
Affiliation(s)
- Alba Quesada-García
- Instituto Nacional Investigaciones Agrarias y Alimentarias. INIA, Dpto. Medio Ambiente, Ctra. De la Coruña Km 7.5., E-28040 Madrid, Spain
| | - Paloma Encinas
- Instituto Nacional Investigaciones Agrarias y Alimentarias. INIA, Dpto. Biotecnologia, Ctra. De la Coruña Km 7.5., E-28040 Madrid, Spain
| | - Ana Valdehita
- Instituto Nacional Investigaciones Agrarias y Alimentarias. INIA, Dpto. Medio Ambiente, Ctra. De la Coruña Km 7.5., E-28040 Madrid, Spain
| | - Lisa Baumann
- Faculty of Vetsuisse, Centre for Fish and Wildlife Health, University of Bern, Länggasstra. 122, CH-3001 Bern, Switzerland
| | - Helmut Segner
- Faculty of Vetsuisse, Centre for Fish and Wildlife Health, University of Bern, Länggasstra. 122, CH-3001 Bern, Switzerland
| | - Julio M Coll
- Instituto Nacional Investigaciones Agrarias y Alimentarias. INIA, Dpto. Biotecnologia, Ctra. De la Coruña Km 7.5., E-28040 Madrid, Spain
| | - José M Navas
- Instituto Nacional Investigaciones Agrarias y Alimentarias. INIA, Dpto. Medio Ambiente, Ctra. De la Coruña Km 7.5., E-28040 Madrid, Spain.
| |
Collapse
|
3
|
Kroon FJ, Hook SE, Jones D, Metcalfe S, Osborn HL. Effects of atrazine on endocrinology and physiology in juvenile barramundi, Lates calcarifer (Bloch). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2014; 33:1607-1614. [PMID: 24687275 DOI: 10.1002/etc.2594] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 12/16/2013] [Accepted: 03/24/2014] [Indexed: 06/03/2023]
Abstract
Exposure to certain environmental contaminants such as agricultural pesticides can alter normal endocrine and reproductive parameters in wild fish populations. Recent studies have found widespread pesticide contamination across the rivers that discharge into the Great Barrier Reef lagoon. Potential impacts on native fish species exposed to known endocrine disrupting chemicals such as atrazine, simazine, and diuron have not been assessed. In the present study, the authors examined the endocrine and physiological effects of short-term, acute exposure of environmentally relevant concentrations of analytical grade atrazine in juvenile barramundi (Lates calcarifer) in a controlled laboratory experiment. Expression of hepatic vitellogenin was not affected, supporting results of previous studies that showed that atrazine does not have a direct estrogenic effect via mediation of estrogen receptors. The lack of effect on brain cytochrome P19B (CYP19B) expression levels, combined with increases in testosterone (T) and 17β estradiol and a stable T:17β estradiol ratio, does not support the hypothesis that atrazine has an indirect estrogenic effect via modulation of aromatase expression. Gill ventilation rate, a measure of oxidative stress, did not change in contrast to other studies finding enhanced osmoregulatory disturbance and gill histopathology after atrazine exposure. To more closely reflect field conditions, the authors recommend that laboratory studies should focus more on examining the effects of commercial pesticide formulations that contain additional ingredients that have been found to be disruptive to endocrine function.
Collapse
|
4
|
Connolly MH, Dutkosky RM, Heah TP, Sayler GS, Henry TB. Temporal Dynamics of Oocyte Growth and Vitellogenin Gene Expression in Zebrafish (Danio Rerio). Zebrafish 2014; 11:107-14. [DOI: 10.1089/zeb.2013.0938] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Michelle H. Connolly
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee
| | - Rachel M. Dutkosky
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee
| | - Tze P. Heah
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee
| | - Gary S. Sayler
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee
| | - Theodore B. Henry
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee
- Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, Tennessee
- School of Life Sciences, Heriot-Watt University, Edinburgh, United Kingdom
| |
Collapse
|
5
|
Williams TD, Mirbahai L, Chipman JK. The toxicological application of transcriptomics and epigenomics in zebrafish and other teleosts. Brief Funct Genomics 2014; 13:157-71. [DOI: 10.1093/bfgp/elt053] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
|
6
|
Regier N, Baerlocher L, Münsterkötter M, Farinelli L, Cosio C. Analysis of the Elodea nuttallii transcriptome in response to mercury and cadmium pollution: development of sensitive tools for rapid ecotoxicological testing. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:8825-8834. [PMID: 23802634 DOI: 10.1021/es401082h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Toxic metals polluting aquatic ecosystems are taken up by inhabitants and accumulate in the food web, affecting species at all trophic levels. It is therefore important to have good tools to assess the level of risk represented by toxic metals in the environment. Macrophytes are potential organisms for the identification of metal-responsive biomarkers but are still underrepresented in ecotoxicology. In the present study, we used next-generation sequencing to investigate the transcriptomic response of Elodea nuttallii exposed to enhanced concentrations of Hg and Cd. We de novo assembled more than 60 000 contigs, of which we found 170 to be regulated dose-dependently by Hg and 212 by Cd. Functional analysis showed that these genes were notably related to energy and metal homeostasis. Expression analysis using nCounter of a subset of genes showed that the gene expression pattern was able to assess toxic metal exposure in complex environmental samples and was more sensitive than other end points (e.g., bioaccumulation, photosynthesis, etc.). In conclusion, we demonstrate the feasibility of using gene expression signatures for the assessment of environmental contamination, using an organism without previous genetic information. This is of interest to ecotoxicology in a wider sense given the possibility to develop specific and sensitive bioassays.
Collapse
Affiliation(s)
- Nicole Regier
- Institut F.-A. Forel, University of Geneva , 10 route de Suisse, CP416, 1290 Versoix, Switzerland
| | | | | | | | | |
Collapse
|
7
|
Pujolar JM, Milan M, Marino IAM, Capoccioni F, Ciccotti E, Belpaire C, Covaci A, Malarvannan G, Patarnello T, Bargelloni L, Zane L, Maes GE. Detecting genome-wide gene transcription profiles associated with high pollution burden in the critically endangered European eel. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2013; 132-133:157-164. [PMID: 23518471 DOI: 10.1016/j.aquatox.2013.02.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 01/28/2013] [Accepted: 02/15/2013] [Indexed: 06/01/2023]
Abstract
The European eel illustrates an example of a critically endangered fish species strongly affected by human stressors throughout its life cycle, in which pollution is considered to be one of the factors responsible for the decline of the stock. The objective of our study was to better understand the transcriptional response of European eels chronically exposed to pollutants in their natural environment. A total of 42 pre-migrating (silver) female eels from lowly, highly and extremely polluted environments in Belgium and, for comparative purposes, a lowly polluted habitat in Italy were measured for polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and brominated flame retardants (BFRs). Multipollutant level of bioaccumulation was linked to their genome-wide gene transcription using an eel-specific array of 14,913 annotated cDNAs. Shared responses to pollutant exposure were observed when comparing the highly polluted site in Belgium with the relatively clean sites in Belgium and Italy. First, an altered pattern of transcription of genes was associated with detoxification, with a novel European eel CYP3A gene and gluthatione S-transferase transcriptionally up-regulated. Second, an altered pattern of transcription of genes associated with the oxidative phosphorylation pathway, with the following genes involved in the generation of ATP being transcriptionally down-regulated in individuals from the highly polluted site: NADH dehydrogenase, succinate dehydrogenase, ubiquinol-cytochrome c reductase, cytochrome c oxidase and ATP synthase. Although we did not measure metabolism directly, seeing that the transcription level of many genes encoding enzymes involved in the mitochondrial respiratory chain and oxidative phosphorylation were down-regulated in the highly polluted site suggests that pollutants may have a significant effect on energy metabolism in these fish.
Collapse
Affiliation(s)
- J M Pujolar
- Department of Biology, University of Padova, I-35131 Padova, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Maes GE, Raeymaekers JAM, Hellemans B, Geeraerts C, Parmentier K, De Temmerman L, Volckaert FAM, Belpaire C. Gene transcription reflects poor health status of resident European eel chronically exposed to environmental pollutants. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2013; 126:242-255. [PMID: 23247545 DOI: 10.1016/j.aquatox.2012.11.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 10/30/2012] [Accepted: 11/07/2012] [Indexed: 06/01/2023]
Abstract
Understanding the effects of chronic exposure to pollutants on the genome and transcriptome of diadromous fish populations is crucial for their resilience under combined anthropogenic and environmental selective pressures. The catadromous European eel (Anguilla anguilla L.) has suffered a dramatic decline in recruitment for three decades, necessitating a thorough assessment of the transcriptional effects of environmental pollutants on resident and migrating eels in natural systems. We investigated the relationship between muscular bioaccumulation levels of metals (Hg, Cd, Pb, Cu, Zn, Ni, Cr, As and Se), PCBs and organochlorine pesticides (DDTs), the health status (condition factor and lipid reserves) and the associated transcriptional response in liver and gill tissues for genes involved in metal detoxification (metallothionein, MT) and oxidative metabolism (cytochrome P4501A, CYP1A) of xenobiotic compounds. In total 84 resident eels originating from three Belgian river basins (Scheldt, Meuse and Yzer) were analyzed along with five unpolluted aquaculture samples as control group. There was a large spatial variation in individual contaminant intensity and profile, while tissue pollution levels were strongly and negatively associated with condition indices, suggesting an important impact of pollution on the health of sub-adult resident eels. Gene transcription patterns revealed a complex response mechanism to a cocktail of pollutants, with a high variation at low pollution levels, but strongly down-regulated hepatic and gill gene transcription in highly polluted eels. Resident eels clearly experience a high pollution burden and seem to show a dysfunctional gene transcription regulation of detoxification genes at higher pollutant levels, correlated with low energy reserves and condition. To fully understand the evolutionary implications of pollutants on eel reproductive fitness, analyses of mature migrating eels and the characterization of their transcriptome-wide gene transcription response would be appropriate to unveil the complex responses associated with multiple interacting stressors and the long-term consequences at the entire species level. In the meanwhile, jointly monitoring environmental and tissue pollution levels at a European scale should be initiated, while preserving high quality habitats to increase the recovery chance of European eel in the future.
Collapse
Affiliation(s)
- G E Maes
- University of Leuven, Laboratory of Biodiversity and Evolutionary Genomics, Belgium.
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Goetz FW, Rise ML, Rise M, Goetz GW, Binkowski F, Shepherd BS. Stimulation of growth and changes in the hepatic transcriptome by 17β-estradiol in the yellow perch (Perca flavescens). Physiol Genomics 2009; 38:261-80. [DOI: 10.1152/physiolgenomics.00069.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The effects of dietary 17β-estradiol (E2) on growth and liver transcriptomics were investigated in the yellow perch ( Perca flavescens). After a 3-mo treatment, E2 significantly stimulated an increase in length and weight of juvenile male and female perch relative to control animals. The increase was significantly greater in females compared with males. Separate, unnormalized cDNA libraries were constructed from equal quantities of RNA from 6 male and 6 female livers of E2-treated and control perch, and 3,546 and 3,719 expressed sequence tags (ESTs) were obtained, respectively. To characterize E2-regulated transcripts, EST frequencies between libraries were calculated within contiguous sequences that were assembled from the combined ESTs of both libraries. Frequencies were also determined in EST transcript groupings produced by aligning all of the ESTs from both libraries at the nucleotide level. From these analyses, there were 28 annotated transcripts that were regulated by 75% between libraries and for which there were at least 5 ESTs of the same transcript between libraries. Regulation of a subset ( 14 ) of these transcripts was confirmed by quantitative reverse transcription-polymerase chain reaction (QPCR). Transcripts that were upregulated by E2 included reproduction-related proteins, binding proteins, and proteases and protease inhibitors. While not part of the transcript frequency analysis, QPCR showed significant upregulation of estrogen receptor esr1 and of insulin-like growth factor I (IGF-I) in E2 livers. E2-downregulated transcripts represented a variety of functional categories including components of the respiratory chain, lipid transport and metabolism, glycolysis, amino acid and nitrogen metabolism, binding proteins, a hydrolytic enzyme, and a transcriptional regulator. In perch it appears that exogenous estrogen drastically shifts liver metabolism toward the production of lipoproteins and carbohydrate binding proteins, and that the growth-promoting action may involve an increase in hepatic IGF-I production.
Collapse
Affiliation(s)
- Frederick W. Goetz
- Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Matthew L. Rise
- Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Marlies Rise
- Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Giles W. Goetz
- Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Frederick Binkowski
- Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Brian S. Shepherd
- Great Lakes WATER Institute/Agricultural Research Service/U.S. Department of Agriculture, Milwaukee, Wisconsin
| |
Collapse
|
10
|
Gallagher EP, LaVire HM, Bammler TK, Stapleton PL, Beyer RP, Farin FM. Hepatic expression profiling in smolting and adult coho salmon (Onchorhynchus kisutch). ENVIRONMENTAL RESEARCH 2008; 106:365-78. [PMID: 18241857 PMCID: PMC3321376 DOI: 10.1016/j.envres.2007.10.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 09/12/2007] [Accepted: 10/04/2007] [Indexed: 05/20/2023]
Abstract
Coho salmon are a critical Pacific salmon species that undergo complex physiological transformations as they migrate towards seawater and enter adult life stages. During these periods, coho may receive exposure to waterborne pollutants that coincide with outmigration through contaminated waterways and return to natal streams. However, little is known regarding the ontogenic modulation of gene expression during these critical life stages. Accordingly, the purpose of the present study was to characterize the hepatic transcriptome of smolting coho, adult males, and adult females by carrying out microarray analysis with a commercially available 16,000 cDNA element platform. Quantitative PCR (Q-PCR) analysis of genes involved in chemical biotransformation (cytochrome P450 isoforms 1A, and 2M1, glutathione S-transferase pi, microsomal GST), defense against metal exposure (metallothionein-A), and reproductive function (vitellogenin receptor) were developed for the purpose of analyzing specific genes of interest and to validate the microarray data. Microarray analysis identified 842 genes that were differentially expressed between smolts and adult males or females (p<0.001 and more than 2-fold difference). These 842 genes were not differentially expressed between adult males and females and, therefore, can be interpreted as a smolt-specific transcriptional profile. Of these 842 genes, 275 were well annotated and formed the basis for further bioinformatics analysis. Many of the differentially expressed genes were involved in basic cellular processes related to protein biosynthesis and degradation (24%), ion transport (12%), transcription (8%), cell structure (8%) and cellular energetics (6%). The majority of differentially expressed genes involved in signal transduction and energy metabolism were expressed at higher levels in adult coho relative to smolts. However, genes associated with cellular protection against chemical injury (i.e. biotransformation, DNA damage repair, and protection against oxidative stress) did not generally differ among the groups. Q-PCR studies revealed extensive interindividual variation in mRNA expression, but were consistent with the microarray results (R(2)=0.74). Collectively, our results indicate differences in liver gene expression in young smolting coho salmon relative to adults and extensive interindividual variation in biotransformation gene expression. However, we did not find a global lack of hepatic biotransformation capacity or poor cellular detoxification response capacity in smolting cohos based on mRNA profiles.
Collapse
Affiliation(s)
- Evan P Gallagher
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195, USA.
| | | | | | | | | | | |
Collapse
|
11
|
Poynton HC, Wintz H, Vulpe CD. Progress in ecotoxicogenomics for environmental monitoring, mode of action, and toxicant identification. COMPARATIVE TOXICOGENOMICS 2008. [DOI: 10.1016/s1872-2423(08)00002-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
12
|
Hook SE, Skillman AD, Gopalan B, Small JA, Schultz IR. Gene expression profiles in rainbow trout, Onchorynchus mykiss, exposed to a simple chemical mixture. Toxicol Sci 2007; 102:42-60. [PMID: 18084045 DOI: 10.1093/toxsci/kfm293] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Among proposed uses for microarrays in environmental toxiciology is the identification of key contributors to toxicity within a mixture. However, it remains uncertain whether the transcriptomic profiles resulting from exposure to a mixture have patterns of altered gene expression that contain identifiable contributions from each toxicant component. We exposed isogenic rainbow trout Onchorynchus mykiss, to sublethal levels of ethynylestradiol, 2,2,4,4-tetrabromodiphenyl ether, and chromium VI or to a mixture of all three toxicants Fluorescently labeled complementary DNA (cDNA) were generated and hybridized against a commercially available Salmonid array spotted with 16,000 cDNAs. Data were analyzed using analysis of variance (p<0.05) with a Benjamani-Hochberg multiple test correction (Genespring [Agilent] software package) to identify up and downregulated genes. Gene clustering patterns that can be used as "expression signatures" were determined using hierarchical cluster analysis. The gene ontology terms associated with significantly altered genes were also used to identify functional groups that were associated with toxicant exposure. Cross-ontological analytics approach was used to assign functional annotations to genes with "unknown" function. Our analysis indicates that transcriptomic profiles resulting from the mixture exposure resemble those of the individual contaminant exposures, but are not a simple additive list. However, patterns of altered genes representative of each component of the mixture are clearly discernible, and the functional classes of genes altered represent the individual components of the mixture. These findings indicate that the use of microarrays to identify transcriptomic profiles may aid in the identification of key stressors within a chemical mixture, ultimately improving environmental assessment.
Collapse
Affiliation(s)
- Sharon E Hook
- Battelle, Marine Research Operations, West Sequim Bay Road, Sequim, Washington 98382, USA.
| | | | | | | | | |
Collapse
|
13
|
Filby AL, Tyler CR. Appropriate 'housekeeping' genes for use in expression profiling the effects of environmental estrogens in fish. BMC Mol Biol 2007; 8:10. [PMID: 17288598 PMCID: PMC1802086 DOI: 10.1186/1471-2199-8-10] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Accepted: 02/08/2007] [Indexed: 11/25/2022] Open
Abstract
Background Attempts to develop a mechanistic understanding of the effects of environmental estrogens on fish are increasingly conducted at the level of gene expression. Appropriate application of real-time PCR in such studies requires the use of a stably expressed 'housekeeping' gene as an internal control to normalize for differences in the amount of starting template between samples. Results We sought to identify appropriate genes for use as internal controls in experimental treatments with estrogen by analyzing the expression of eight functionally distinct 'housekeeping' genes (18S ribosomal RNA [18S rRNA], ribosomal protein l8 [rpl8], elongation factor 1 alpha [ef1a], glucose-6-phosphate dehydrogenase [g6pd], beta actin [bactin], glyceraldehyde-3-phosphate dehydrogenase [gapdh], hypoxanthine phosphoribosyltransferase 1 [hprt1], and tata box binding protein [tbp]) following exposure to the environmental estrogen, 17α-ethinylestradiol (EE2), in the fathead minnow (Pimephales promelas). Exposure to 10 ng/L EE2 for 21 days down-regulated the expression of ef1a, g6pd, bactin and gapdh in the liver, and bactin and gapdh in the gonad. Some of these effects were gender-specific, with bactin in the liver and gapdh in the gonad down-regulated by EE2 in males only. Furthermore, when ef1a, g6pd, bactin or gapdh were used for normalization, the hepatic expression of two genes of interest, vitellogenin (vtg) and cytochrome P450 1A (cyp1a) following exposure to EE2 was overestimated. Conclusion Based on the data presented, we recommend 18S rRNA, rpl8, hprt1 and/or tbp, but not ef1a, g6pd, bactin and/or gapdh, as likely appropriate internal controls in real-time PCR studies of estrogens effects in fish. Our studies show that pre-validation of control genes considering the scope and nature of the experiments to be performed, including both gender and tissue type, is critical for accurate assessments of the effects of environmental estrogens on gene expression in fish.
Collapse
Affiliation(s)
- Amy L Filby
- Environmental and Molecular Fish Biology Group, School of Biosciences, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter, Devon, EX4 4PS, UK
| | - Charles R Tyler
- Environmental and Molecular Fish Biology Group, School of Biosciences, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter, Devon, EX4 4PS, UK
| |
Collapse
|