Identification of differentially expressed genes from contaminant and thermal exposed goldfish Carassius auratus in Gaobeidian Lake in Beijing, China

Effects on the Liver Transcriptome in Baltic Salmon: Contributions of Contamination with Organohalogen Compounds and Origin of Salmon

Hatchery-reared Atlantic salmon (Salmo salar) has been released to support the wild salmon stocks in the Baltic Sea for decades. During their feeding migration, salmon are exposed to organohalogen compounds (OHCs). Here, we investigated the OHC levels and transcriptome profiles in the liver of wild and hatchery-reared salmon collected from the Baltic main basin (BMB), the Bothnian Sea (BS), and the Gulf of Finland (GoF) and examined whether salmon origin and OHC levels contributed to the hepatic transcriptome profiles. There were no differences in the OHC concentrations between wild and reared fish but larger differences between areas. Several transcript levels were associated with non-dioxin-like polychlorinated biphenyls, polybrominated diphenylethers, chlordanes, and dichlorodiphenyltrichloroethane in a concentration-dependent manner. Between wild and reared salmon, lipid metabolism and related signaling pathways were enriched within the BMB and BS, while amino acid metabolism was altered within the GoF. When comparing the different areas, lipid metabolism, environmental stress and cell growth, and death-related pathways were enriched. Class coinertia analysis showed that the covariation in the OHC levels and the transcriptome were significantly similar. These results suggest that the hepatic transcriptomes in wild and hatchery-reared salmon are more affected by the OHC levels rather than the origin of salmon.

Under control: The innate immunity of fish from the inhibitors' perspective

The innate immune response involves a concerted network of induced gene products, preformed immune effectors, biochemical signalling cascades and specialised cells. However, the multifaceted activation of these defensive measures can derail or overshoot and, if left unchecked, overwhelm the host. A plenty of regulatory devices therefore mediate the fragile equilibrium between pathogen defence and pathophysiological manifestations. Over the past decade in particular, an almost complete set of teleostean sequences orthologous to mammalian immunoregulatory factors has been identified in various fish species, which prove the remarkable conservation of innate immune-control concepts among vertebrates. This review will present the current knowledge on more than 50 teleostean regulatory factors (plus additional fish-specific paralogs) that are of paramount importance for controlling the clotting cascade, the complement system, pattern-recognition pathways and cytokine-signalling networks. A special focus lies on those immunoregulatory features that have emerged as potential biomarker genes in transcriptome-wide research studies. Moreover, we report on the latest progress in elucidating control elements that act directly with immune-gene-encoding nucleic acids, such as transcription factors, hormone receptors and micro- and long noncoding RNAs. Investigations into the function of teleostean inhibitory factors are still mainly based on gene-expression profiling or overexpression studies. However, in support of structural and in-vitro analyses, evidence from in-vivo trials is also available and revealed many biochemical details on piscine immune regulation. The presence of multiple gene copies in fish adds a degree of complexity, as it is so far hardly understood if they might play distinct roles during inflammation. The present review addresses this and other open questions that should be tackled by fish immunologists in future.

Spatial variation in transcript and protein abundance of Atlantic salmon during feeding migration in the Baltic Sea

The fitness and reproductive output of fishes can be affected by environmental disturbances. In this study, transcriptomics and label-free proteomics were combined to investigate Atlantic salmon (Salmo salar) sampled from three different field locations within the Baltic Sea (Baltic Main Basin (BMB), Gulf of Finland (GoF), and Bothnian Sea (BS)) during marine migration. The expression of several stress related mRNAs and proteins of xenobiotic metabolism, oxidative stress, DNA damage, and cell death were increased in salmon from GoF compared to salmon from BMB or BS. Respiratory electron chain and ATP synthesis related gene ontology-categories were upregulated in GoF salmon, whereas those associated with RNA processing and synthesis, translation, and protein folding decreased. Differences were seen also in metabolism and immune function related gene expression. Comparisons of the transcriptomic and proteomic profiles between salmon from GoF and salmon from BMB or BS suggest environmental stressors, especially exposure to contaminants, as a main explanation for differences. Salmon feeding in GoF are thus “disturbed by hazardous substances”. The results may also be applied in evaluating the conditions of pelagic ecosystems in the different parts of Baltic Sea.

Heat-shock responsive genes identified and validated in Atlantic cod (Gadus morhua) liver, head kidney and skeletal muscle using genomic techniques

BACKGROUND

Daily and seasonal changes in temperature are challenges that fish within aquaculture settings cannot completely avoid, and are known to elicit complex organismal and cellular stress responses. We conducted a large-scale gene discovery and transcript expression study in order to better understand the genes that are potentially involved in the physiological and cellular aspects of stress caused by heat-shock. We used suppression subtractive hybridization (SSH) cDNA library construction and characterization to identify transcripts that were dysregulated by heat-shock in liver, skeletal muscle and head kidney of Atlantic cod. These tissues were selected due to their roles in metabolic regulation, locomotion and growth, and immune function, respectively. Fish were exposed for 3 hours to an 8 degrees C elevation in temperature, and then allowed to recover for 24 hours at the original temperature (i.e. 10 degrees C). Tissue samples obtained before heat-shock (BHS), at the cessation of heat-shock (CS), and 3, 12, and 24 hours after the cessation of heat-shock (ACS), were used for reciprocal SSH library construction and quantitative reverse transcription - polymerase chain reaction (QPCR) analysis of gene expression using samples from a group that was transferred but not heat-shocked (CT) as controls.

RESULTS

We sequenced and characterized 4394 ESTs (1524 from liver, 1451 from head kidney and 1419 from skeletal muscle) from three "forward subtracted" libraries (enriched for genes up-regulated by heat-shock) and 1586 from the liver "reverse subtracted" library (enriched for genes down-regulated by heat-shock), for a total of 5980 ESTs. Several cDNAs encoding putative chaperones belonging to the heat-shock protein (HSP) family were found in these libraries, and "protein folding" was among the gene ontology (GO) terms with the highest proportion in the libraries. QPCR analysis of HSP90alpha and HSP70-1 (synonym: HSPA1A) mRNA expression showed significant up-regulation in all three tissues studied. These transcripts were more than 100-fold up-regulated in liver following heat-shock. We also identified HSP47, GRP78 and GRP94-like transcripts, which were significantly up-regulated in all 3 tissues studied. Toll-like receptor 22 (TLR22) transcript, found in the liver reverse SSH library, was shown by QPCR to be significantly down-regulated in the head kidney after heat-shock.

CONCLUSION

Chaperones are an important part of the cellular response to stress, and genes identified in this work may play important roles in resistance to thermal-stress. Moreover, the transcript for one key immune response gene (TLR22) was down-regulated by heat-shock, and this down-regulation may be a component of heat-induced immunosuppression.

Proteomic study of the effects of complex environmental stresses in the livers of goldfish (Carassius auratus) that inhabit Gaobeidian Lake in Beijing, China

Recent advances in proteomics have provided an excellent opportunity to understand biological adaptation under complex environmental stress at the protein level. Gaobeidian Lake, located in Beijing, China, is characterized by complex environmental stresses by serving as both the effluent of a wastewater treatment plant and a coolant of a nearby thermal power plant. Liver is the primary organ of energy metabolism and xenobiotic detoxification. To further our understanding of how organisms that live in Gaobeidian Lake acclimatize themselves to these complex environmental stresses, hepatic protein expression patterns were examined in goldfish Carassius auratus that inhabit the lake. Huairou Reservoir, a drinking water source, was used as a reference site. Twenty four protein spots, which were differently expressed in the two sites, were further digested with trypsin and analyzed by matrix-assisted laser desorption/ionization (MALDI) tandem time of flight mass spectrometry (TOF/TOF). The expression of several energy metabolism and oxidative stress proteins, such as glutathione peroxidase (GPx), ferritin H3, and liver basic fatty acid-binding protein (Lb-FABP) were found to be altered in this stressful environment. In addition to the up-regulation of GPx translation, both the mRNA levels and enzymatic activity of GPx protein were elevated in goldfish living in Gaobeidian Lake. The expression of both peroxisome proliferator activated receptor (PPAR), one of the most important metabolism and stress regulation genes as well as cytochrome P450 1A1 (CYP1A1), a detoxification gene, was also detected by real-time PCR at the two sites. Increased expression levels of both PPAR-beta and CYP1A1 (P < 0.1) were observed in Gaobeidian Lake. Our study provides an integrative view of the expression levels of hepatic proteins and genes in goldfish under complex environmental stress that live in Gaobeidian Lake. Our results showed that anthropogenic environmental stresses in Gaobeidian Lake activated the regulation gene of lipid metabolism PPAR, elevated the lipid metabolism levels, and activated the anti-oxidative adaptation mechanism of organisms in the lake.