Vitellogenin Transcript Research Articles

Vitellogenin gene characterization and expression of Asian paddle crabs (Charybdis japonica) following endocrine disrupting chemicals

Vitellogenin (VTG), the yolk-precursor lipoprotein, has been widely recognized as a biomarker for the detection of estrogenic activity in water-borne chemical pollutants. The Asian paddle crab, Charybdis japonica, is a potential bio-indicator for monitoring marine environments. The aim of this study was to identify the possibility of using C. japonica VTG as biomarkers of stress caused by endocrine disrupting chemicals (EDCs). We characterized a partial sequence of the VTG cDNA in the C. japonica crab and evaluated the crab’s mRNA expression profiles following exposure to different concentrations of bisphenol A (BPA) and 4-nonylphenol (NP) for 24 or 96 h. The sequence homology of C. japonica VTG is over 93% in nucleotide and over 98% in amino acid with the corresponding gene of other crabs. Phylogenetic analysis revealed that the C. japonica VTG is an ortholog of other species of lobster and shrimp. Tissue distribution analysis of the C. japonica VTG mRNA revealed that the expression of VTG mRNA was highest in the ovary of females and hepatopancreas. The expression of the C. japonica VTG gene in various BPA or NP concentrations during shorter and longer times was assessed. The expression of VTG transcripts was significantly increased in the C. japonica crab exposed to BPA and NP at different concentrations for 24 h. The mRNA expression of the VTG gene was significantly induced in concentration- and time-dependent manners after BPA or NP exposures for 96 h. These results indicate that crab C. japonica VTG could be used as a potential biomarker of EDCs in marine environment monitoring.

Low-dose bisphenol A disrupts gonad development and steroidogenic genes expression in adult female rare minnow Gobiocypris rarus

Bisphenol A (BPA), an estrogenic monomer, has attracted many researchers to study its adverse effects in animal reproduction, especially in fish. To explore the effects of low dose BPA on adult female rare minnow Gobiocypris rarus, we exposed the fish to BPA at nominal concentrations of 5, 15, and 50μgL−1 for 14 and 35d. The 35-d BPA exposure at 50μgL−1 had obviously suppressive effects on oocyte development, and BPA at all the three concentrations in both exposure durations of 14 and 35d had stimulative effects on hepatic vitellogenin (vtg) transcription. BPA at lower concentrations (5 and 15μgL−1) exhibited stimulative effects on the expressions of ovarian steroidogenic genes while at higher concentration (50μgL−1) displayed inhibitive effects. Analysis of ovarian steroidogenic genes 5′-flanking regions and mRNA expressions of their potential regulatory factors revealed that the BPA-mediated actions on steroidogenesis in G. rarus ovary probably involve estrogen receptor (Esr) and androgen receptor (Ar) signaling, nuclear receptor subfamily 5, group A, number 1 (Nr5a1) pathway, and epigenetic regulation.

Effects of clofibric acid alone and in combination with 17β-estradiol on mRNA abundance in primary hepatocytes isolated from rainbow trout

Clofibric acid (CA) is the active substance of lipid lowering drugs. It is resistant to degradation, polar in nature, and has been found ubiquitously in the aquatic environment. Though CA is classified as a peroxisomal proliferator in rodents and is considered as a potential endocrine disruptor, little information exists on the effects of CA in aquatic organisms, such as fish. In the present study, we examined the mRNA levels of peroxisome proliferator- and estrogen-sensitive genes on the exposure of primary rainbow trout (Oncorhynchus mykiss) hepatocytes to CA alone and in combination with the natural female sex hormone, 17β-estradiol (E2). Our results demonstrate that rainbow trout hepatocytes are relatively refractory to the effects of CA on the PPAR signaling pathway and lipid metabolism. Moreover, CA did not show recognizable estrogenic activity, but after the induction of vitellogenesis by E2, CA significantly reduced vitellogenin (VTG) mRNA abundance. Apparently, the indirect repression of VTG transcription, independent of estrogen receptors, occurred. The mechanism is not yet clearly understood but may involve disruption of the stabilization of VTG mRNA known to be induced by E2.

Short-term treatment of adult male zebrafish (Danio Rerio) with 17α-ethinyl estradiol affects the transcription of genes involved in development and male sex differentiation

The synthetic estrogen 17α-ethinyl estradiol (EE2) disturbs reproduction and causes gonadal malformation in fish. Effects on the transcription of genes involved in gonad development and function that could serve as sensitive biomarkers of reproductive effects in the field is, however, not well known. We have studied mRNA expression in testes and liver of adult zebrafish (Danio rerio) males treated with 0, 5 or 25ng/L EE2for 14days. qPCR analysis showed that the mRNA expression of four genes linked to zebrafish male sex determination and differentiation, Anti-Mullerian Hormone, Double sex and mab-related protein, Sry-related HMG box-9a and Nuclear receptor subfamily 5 group number 1b were significantly decreased by 25ng/L, but not 5ng/L EE2 compared with the levels in untreated fish. The decreased transcription was correlated with a previously shown spawning failure in these males (Reyhanian et al., 2011. Aquat Toxicol 105, 41–48), suggesting that decreased mRNA expression of genes regulating male sexual function could be involved in the functional sterility. The mRNA level of Cytochrome P-45019a, involved in female reproductive development, was unaffected by hormone treatment. The transcription of the female-specific Vitellogenin was significantly induced in testes. While testicular Androgen Receptor and the Estrogen Receptor-alpha mRNA levels were unchanged, Estrogen receptor-beta was significantly decreased by 25ng/L EE2. Hepatic Estrogen Receptor-alpha mRNA was significantly increased by both exposure concentrations, while Estrogen Receptor-beta transcription was unaltered. The decreased transcription of male-predominant genes supports a demasculinization of testes by EE2 and might reflect reproductive disturbances in the environment.

20‐hydroxyecdysone mediates non‐canonical regulation of mosquito vitellogenins through alternative splicing

Vitellogenesis is one of the most well-studied physiological processes in mosquitoes. Expression of mosquito vitellogenin genes is classically described as being restricted to female adult reproduction. We report premature vitellogenin transcript expression in three vector mosquitoes: Culex tarsalis, Aedes aegypti and Anopheles gambiae. Vitellogenins expressed during non-reproductive stages are alternatively spliced to retain their first intron and encode premature termination codons. We show that intron retention results in transcript degradation by translation-dependent nonsense-mediated mRNA decay. This is probably an example of regulated unproductive splicing and translation (RUST), a mechanism known to regulate gene expression in numerous organisms but which has never been described in mosquitoes. We demonstrate that the hormone 20-hydroxyecdysone (20E) is responsible for regulating post-transcriptional splicing of vitellogenin. After exposure of previtellogenic fat bodies to 20E, vitellogenin expression switches from a non-productive intron-retaining transcript to a spliced protein-coding transcript. This effect is independent of factors classically known to influence transcription, such as juvenile hormone-mediated competence and amino acid signalling through the target of rapamycin pathway. Non-canonical regulation of vitellogenesis through RUST is a novel role for the multifunctional hormone 20E, and may have important implications for general patterns of gene regulation in mosquitoes.

Characterization of the shrimp neuroparsin (MeNPLP): RNAi silencing resulted in inhibition of vitellogenesis

The full-length Metapenaeus ensis neuroparsin (MeNPLP) cDNA was cloned which encodes a shrimp protein homologous to the insect neuroparsin and vertebrate insulin-like growth factor binding protein (IGFBP). MeNPLP cDNA is 1389bp in length and the longest open reading frame is 303bp in length. The first 27 aa are predicted to be the signal peptide and aa 28–101 is the mature peptide with an estimated molecular weight of 7.83kDa and pI of 5. It shows high amino acid sequence similarity (42–68%) to the neuroparsin of insects and N-terminal end of the IGFBP of vertebrates. The cysteine residues in MeNPLP responsible for disulfide bond formation are conserved as in other neuroparsin-like proteins. The expression level of MeNPLP is the highest in the hepatopancreas, followed by the nerve cord, brain, heart, ovary, and muscle. However, it was not expressed in the testis. Using an insect neuroparsin antibody, MeNPLP could only be detected in the hepatopancreatic tubules, suggesting that MeNPLP may be a secretary product. Although MeNPLP expression was stimulated in the ovary, it was inhibited in the hepatopancreas after treatment with neurotransmitter serotonin (5-HT). In vivo gene silencing of MeNPLP could cause a significant decrease of vitellogenin transcript level in the hepatopancreas and ovary. As a result, a corresponding decrease in vitellogenin protein level was observed in the hemolymph and ovary. In conclusion, this study has provided the first evidence that MeNPLP is involved in the initial stage of ovary maturation in shrimp.

Dietary CdSe/ZnS quantum dot exposure in estuarine fish: Bioavailability, oxidative stress responses, reproduction, and maternal transfer

Continued development, use, and disposal of quantum dots (QDs) ensure their entrance into aquatic environments where they could pose a risk to biological organisms as whole nanoparticles or as degraded metal constituents. Reproductive Fundulus heteroclitus were fed a control diet with lecithin, diets containing 1 or 10μg of lecithin-encapsulated CdSe/ZnS QD/day, or a diet containing 5.9μg CdCl2/day for 85 days. Cadmium concentrations in liver, intestine, and eggs were quantified with inductively coupled plasma mass spectrometry. In fish fed 10μg QD/day, QDs or their degradation products traversed the intestinal epithelia and accumulated in the liver. Less than 0.01% of the QD's cadmium was retained in the liver or intestinal tissues. This compares to 0.9% and 0.5% of the cadmium in the intestine and liver, respectively of fish fed a CdCl2 diet. Cadmium was also detected in the eggs from parents fed 10μg QD/day. No significant changes in hepatic total glutathione, lipid peroxidation, or expression of genes involved in metal metabolism or oxidative stress were observed. While QDs in the diet are minimally bioavailable, unusual levels of vitellogenin transcription in male fish as well as declining fecundity require further investigation to determine if endocrine disruption is of environmental concern.

Disruption of zebrafish (Danio rerio) sexual development after full life-cycle exposure to environmental levels of triadimefon

In this study, zebrafish was exposed to environmental levels of triadimefon (0.125, 0.25, 0.5μg/mL) from 24h post fertilization to 120 days post fertilization. Several endpoints that related to reproductive function were evaluated. It was found that the body length, body weight and vitellogenin transcription were significantly reduced for fish exposed to triadimefon. Histological examination showed that the sex ratio of fish skewed to male and female exposed to 0.5μg/mL triadimefon had immature ovary. The breeding success, as determined from data on egg production and spawning, was reduced in fish exposed to 0.25μg/mL triadimefon. In the offspring, the reduced egg fertility, hatching rate and survival were observed in eggs exposed to 0.5μg/mL triadimefon. These findings indicated that triadimefon had the potential to adversely affect the sexual development and breeding success through the multiple endocrine actions.

The Synthetic Progestin Levonorgestrel Is a Potent Androgen in the Three-Spined Stickleback (Gasterosteus aculeatus)

The use of progestins has resulted in contamination of aquatic environments and some progestins have in experimental studies been shown to impair reproduction in fish and amphibians at low ng L(-1) concentrations. The mechanisms underlying their reproductive toxicity are largely unknown. Some progestins, such as levonorgestrel (LNG), exert androgenic effects in mammals by activating the androgen receptor (AR). Male three-spined stickleback (Gasterosteus aculeatus) kidneys produce spiggin, a gluelike glycoprotein used in nest building, and its production is directly governed by androgens. Spiggin is normally absent in females but its production in female kidneys can be induced by AR agonists. Spiggin serves as the best known biomarker for androgens in fish. We exposed adult female sticklebacks to LNG at 5.5, 40, and 358 ng L(-1) for 21 days. Androgenic effects were found at LNG concentrations ≥40 ng L(-1) including induction of spiggin transcription, kidney hypertrophy, and suppressed liver vitellogenin transcription. These are the first in vivo quantitative data showing that LNG is a potent androgen in fish supporting the contention that androgenic effects of certain progestins contribute to their reproductive toxicity.

Transcriptomic Analyses of Sexual Dimorphism of the Zebrafish Liver and the Effect of Sex Hormones

The liver is one of the most sex-dimorphic organs in both oviparous and viviparous animals. In order to understand the molecular basis of the difference between male and female livers, high-throughput RNA-SAGE (serial analysis of gene expression) sequencing was performed for zebrafish livers of both sexes and their transcriptomes were compared. Both sexes had abundantly expressed genes involved in translation, coagulation and lipid metabolism, consistent with the general function of the liver. For sex-biased transcripts, from in addition to the high enrichment of vitellogenin transcripts in spawning female livers, which constituted nearly 80% of total mRNA, it is apparent that the female-biased genes were mostly involved in ribosome/translation, estrogen pathway, lipid transport, etc, while the male-biased genes were enriched for oxidation reduction, carbohydrate metabolism, coagulation, protein transport and localization, etc. Sexual dimorphism on xenobiotic metabolism and anti-oxidation was also noted and it is likely that retinol x receptor (RXR) and liver x receptor (LXR) play central roles in regulating the sexual differences of lipid and cholesterol metabolisms. Consistent with high ribosomal/translational activities in the female liver, female-biased genes were significantly regulated by two important transcription factors, Myc and Mycn. In contrast, Male livers showed activation of transcription factors Ppargc1b, Hnf4a, and Stat4, which regulate lipid and glucose metabolisms and various cellular activities. The transcriptomic responses to sex hormones, 17β-estradiol (E2) or 11-keto testosterone (KT11), were also investigated in both male and female livers and we found that female livers were relatively insensitive to sex hormone disturbance, while the male livers were readily affected. E2 feminized male liver by up-regulating female-biased transcripts and down-regulating male-biased transcripts. The information obtained in this study provides comprehensive insights into the sexual dimorphism of zebrafish liver transcriptome and will facilitate further development of the zebrafish as a human liver disease model.

カットスロートトラウト <i>Oncorhynchus clarki</i> における2 型ビテロジェニン転写産物および蛋白質の卵発達に伴う発現変化

カットスロートトラウト <i>Oncorhynchus clarki</i> における2 型ビテロジェニン転写産物および蛋白質の卵発達に伴う発現変化

Characterisation of genes transcriptionally upregulated in the liver of sand goby (Pomatoschistus minutus) by 17α-ethinyloestradiol: Identification of distinct vitellogenin and zona radiata protein transcripts

The sand goby (Pomatoschistus minutus), is a marine and estuarine teleost that is used in environmental, reproductive and behavioural studies of oestrogenic endocrine disruption. The xeno-oestrogen, 17α-ethinyloestradiol (EE2), induces expression of egg proteins vitellogenin (VTG) and zona radiata protein (ZRP) in male fish and impairs reproduction. Multiple forms of VTG and ZRP genes are found in other teleost species, yet the characteristics of VTG and ZRP in the sand goby are unknown. In this investigation, Suppressive Subtractive Hybridization was used to isolate cDNA fragments from liver, identified as belonging to 11 distinct sand goby genes, suggesting that these genes are transcriptionally upregulated by EE2. Assembly of these fragments revealed three VTG genes which shared homology with VTG classes A, B and C in other fish and two ZRP genes sharing homology with ZRP classes Ba and Bb. RTqPCR of RNA from the sand goby liver was used to show that these VTGs and ZRPs were present in low levels in control males and high levels in mature females. Exposure of males to a concentration of 11ngL−1 EE2 caused a significant increase in all VTG and ZRP transcript levels. The identification of these egg protein transcripts and the development of validated assays for their quantification will facilitate future work with this useful model species.

Estrogen Modulates Hepatic Gene Expression and Survival of Rainbow Trout Infected with Pathogenic Bacteria Yersinia ruckeri

In the aquatic environment, fish are exposed to various stimuli at once and have developed different response mechanisms to deal with these multiple stimuli. The current study assessed the combined impacts of estrogens and bacterial infection on the physiological status of fish. Juvenile rainbow trout were exposed to two different concentrations of 17β-estradiol (E2) (2 or 20mg/kg feed) and then infected with three concentrations of Yersinia ruckeri, a bacterial pathogen causing massive losses in wild and farmed salmonid populations. Organism-level endpoints to assess the impact of the single and combined treatments included hepatic vitellogenin transcript expression to evaluate the E2 exposure efficiency and survival rate of pathogen-challenged fish. The two E2 doses increased vitellogenin levels within the physiological range. Infection with Y. ruckeri caused mortality of trout, and this effect was significantly enhanced by a simultaneous exposure to high E2 dose. The hormone reduced survival at intermediate and high (10(4) and 10(6) colony forming units, cfu) bacterial concentrations, but not for a low one (10(2)cfu). Analysis of hepatic gene expression profiles by a salmonid 2k cDNA microarray chip revealed complex regulations of pathways involved in immune responses, stress responses, and detoxicification pathways. E2 markedly reduced the expression of several genes implicated in xenobiotic metabolism. The results suggest that the interaction between pathogen and E2 interfered with the fish's capability of clearing toxic compounds. The findings of the current study add to our understanding of multiple exposure responses in fish.

Composition and Phylogenetic Analysis of Vitellogenin Coding Sequences in the Indonesian Coelacanth Latimeria menadoensis

The coelacanth Latimeria menadoensis, a living fossil, occupies a key phylogenetic position to explore the changes that have affected the genomes of the aquatic vertebrates that colonized dry land. This is the first study to isolate and analyze L. menadoensis mRNA. Three different vitellogenin transcripts were identified and their inferred amino acid sequences compared to those of other known vertebrates. The phylogenetic data suggest that the evolutionary history of this gene family in coelacanths was characterized by a different duplication event than those which occurred in teleosts, amniotes, and amphibia. Comparison of the three sequences highlighted differences in functional sites. Moreover, despite the presence of conserved sites compared with the other oviparous vertebrates, some sites were seen to have changed, others to be similar only to those of teleosts, and others still to resemble only to those of tetrapods.

Differences in the induction of cyp1A and related genes in cultured rainbow trout Oncorhynchus mykiss. Additional considerations for the use of EROD activity as a biomarker

Two rainbow trout Oncorhynchus mykiss fish farms were repeatedly sampled in order to observe the variability of ethoxyresorufin-O-deethylase (EROD) activity and of related genes in the liver. Fish coming from fish farm A exhibited EROD levels that could be considered as basal according to the scientific literature, however, EROD activity in fish coming from fish farm B was significantly increased. This was accompanied by augmented aryl hydrocarbon receptor (ahr) and cytochrome P4501A (cyp1A) messenger RNA expression and reduced oestrogen receptor (er) and vitellogenin (vtg) transcription. Only sediment extracts from the entry channel of fish farm B induced EROD activity in O. mykiss cultured cells, however, this induction could not be explained by the levels of polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) measured in the sediments. The results of this study point out that O. mykiss cultured in fish farms could be used as sentinels for indication of pollution. In this particular work, however, no conclusive evidence has been found for a relationship between the presence of PAHs and PCBs and the observed EROD induction.

Effect of elevated temperature on estrogenic induction of vitellogenesis and zonagenesis in juvenile Atlantic salmon (Salmo salar)

Fertility and embryo survival rates are often low in eggs from thermally challenged Tasmanian Atlantic salmon, partly due to a reduction in plasma 17β-estradiol (E2) levels. We used juvenile Atlantic salmon to assess whether hepatic tissue remains responsive to stimulation by E2 at the higher temperatures sometimes encountered by Tasmanian salmon during summer. E2 administration stimulated vitellogenin (Vtg) and estrogen receptor alpha transcription at 14°C and 22°C, although induction of Vtg occurred more rapidly at 22°C. Consequently, plasma Vtg levels increased and reached a plateau more quickly at 22°C. Zona pellucida (Zp) B and C transcription was significantly lower in E2-treated fish at 22°C relative to 14°C. This shows that the Vtg gene is E2-responsive at high temperature unlike Zp B and C genes that displayed traits of thermal inhibition. Therefore, estrogen replacement therapy in adult salmon may offset some, but not all thermal inhibition of reproductive function.

Vitellogenin induction by 17β‐estradiol and 17α‐ethynylestradiol in male Murray rainbowfish (Melanotaenia fluviatilis)

Hepatic vitellogenin (VTG) mRNA and plasma protein assays were developed for the Murray rainbowfish (Melanotaenia fluviatilis), a native freshwater fish species in Australia. Adult male Murray rainbowfish were exposed to 17β-estradiol (E2) or 17α-ethynylestradiol (EE2) at 0, 1, 5, 10, 50, or 100 ng/L in a semistatic system for 7 d. Vitellogenin mRNA was quantified by quantitative polymerase chain reaction, and VTG protein was semiquantified in plasma using an enzyme-linked immunosorbent assay. Water concentrations were quantified by liquid chromatography coupled with tandem mass spectrometry and were on average 110% and 85% nominal concentrations for E2 and EE2, respectively. Vitellogenin transcripts and protein were upregulated in male Murray rainbowfish exposed to either E2 or EE2 in a dose-responsive manner, with calculated 10% effective concentration (EC10) values for E2 of 3.71 ng/L and 11.6 ng/L for VTG mRNA and protein, respectively, and for EE2 of 2.77 ng/L and 8.47 ng/L for VTG mRNA and protein, respectively. Comparisons of these responses with responses of commonly used test species, including zebrafish (Danio rerio), fathead minnow (Pimephales promelas), and Japanese medaka (Oryzias latipes), revealed the Murray rainbowfish to be a sensitive test species for estrogenic effects via the estrogen receptor pathway. The present study suggests that the Murray rainbowfish would be a suitable candidate for future field studies designed for assessing estrogenic effects of effluent discharges in the Australian freshwater environment.

RNA interference of insulin-related peptide and neuroparsins affects vitellogenesis in the desert locust Schistocerca gregaria

The ‘classic’ insect hormones, juvenile hormone and 20-hydroxyecdysone, can stimulate vitellogenesis and/or ovarian development in adult females of several insect species. Accumulating evidence also indicates a crucial role in female reproductive physiology for peptide hormones, such as insulin-related peptides (IRPs) and neuroparsins (NPs). Especially in dipteran species, IRP signaling has been shown to regulate female reproductive events. The first NP was originally identified from the migratory locust ( Locusta migratoria) as an antigonadotropic factor that delayed vitellogenesis. Moreover, NP family members display sequence similarities with the N-terminal domain of vertebrate insulin-like growth factor binding proteins (IGFBPs). In the current study, RNA interference (RNAi) was employed to investigate the possible involvement of IRP and NPs in the control of the female desert locust ( Schistocerca gregaria) reproductive system. The cDNAs encoding an IRP ( Scg-IRP) and four NPs ( Scg-NPs) had previously been cloned from S. gregaria. An RNAi-mediated knock-down of either Scg-NP or Scg-IRP transcript levels was induced in adult female desert locusts and the subsequent effects were analyzed. Knock-down of the Scg-NPs or Scg-IRP affected vitellogenin transcript levels and oocyte growth in a positive and negative way, respectively. The current findings are indicative for a role of Scg-NPs and Scg-IRP in the control of vitellogenin synthesis. A plausible hypothesis is that Scg-IRP may act as a sensor of the nutritional and metabolic status that determines whether vitellogenesis can occur. That the same processes were affected in opposite ways in both RNAi experiments offers an extra argument for antagonizing roles of Scg-NPs and Scg-IRP.

Vitellogenin gene expression in autogenous Culex tarsalis

Autogeny, the ability of a mosquito to mature an initial batch of eggs without blood feeding, is an alternative reproductive strategy with important implications for vector-borne disease transmission. Regulation of the major yolk protein (vitellogenin; Vg) genes during bloodmeal-induced oogenesis is well studied, but little is known about regulation of vitellogenesis in autogenous mosquitoes. We characterized the expression of four vitellogenin genes (Vg1a, Vg1b, Vg2a and Vg2b) in an autogenous strain of the West Nile Virus vector, Culex tarsalis. All vitellogenin genes were expressed during autogenous reproduction and following a bloodmeal, although the intensity and duration of expression varied amongst genes. Quantitative PCR analysis of vitellogenin transcription during autogeny revealed a similar temporal pattern to known vitellogenin expression profiles in anautogenous Aedes aegypti. Vitellogenin transcript, primarily produced from the Vg1b gene, was also detected in the larval and pupal stages of development, but no detectable vitellogenin protein was produced during this time period.

Mechanisms of toxicity of di(2-ethylhexyl) phthalate on the reproductive health of male zebrafish

Phthalates are ubiquitous in the aquatic environment and are known to adversely affect male reproductive health in mammals through interactions with multiple receptor systems. However, little is known about the risks they pose to fish. This project investigated the effects of di(2-ethylhexyl) phthalate (DEHP), the most commonly used phthalate, on the reproductive health of male zebrafish ( Danio rerio). Males were treated with 0.5, 50 and 5000 mg DEHP kg −1 (body weight) for a period of 10 days via intraperitoneal injection. The effects of the exposure were assessed by analysing fertilisation success, testis histology, sperm DNA integrity and transcript profiles of the liver and testis. A significant increase in the hepatosomatic index and levels of hepatic vitellogenin transcript were observed following exposure to 5000 mg DEHP kg −1. Exposure to 5000 mg DEHP kg −1 also resulted in a reduction in fertilisation success of oocytes spawned by untreated females. However, survival and development of the resulting embryos were unaffected by all treatments, and no evidence of DEHP-induced sperm DNA damage was observed. Exposure to 50 and 5000 mg DEHP kg −1 caused alterations in the proportion of germ cells at specific stages of spermatogenesis in the testis, including a reduction in the proportion of spermatozoa and an increase in the proportion of spermatocytes, suggesting that DEHP may inhibit the progression of meiosis. In parallel, exposure to 5000 mg DEHP kg −1 increased the levels of two peroxisome proliferator-activated receptor (PPAR) responsive genes ( acyl-coenzyme A oxidase 1 ( acox1) and enoyl-coenzyme A, hydratase/3-hydroxyacyl coenzyme A dehydrogenase ( ehhadh). These data demonstrated that exposure to high concentrations of DEHP disrupts spermatogenesis in adult zebrafish with a consequent decrease in their ability to fertilise oocytes spawned by untreated females. Furthermore, our data suggest that the adverse effects caused by exposure to DEHP are likely to occur preferentially via PPAR signalling pathways in the testis and oestrogen signalling pathways in the liver. We found no evidence of adverse effects on zebrafish reproductive health following exposure to the concentrations occurring in most aquatic systems, indicating that DEHP alone may not be a causative agent of the reproductive abnormalities seen in wildlife, at least as a result of short-term exposures.