JAK and STAT members in channel catfish: Identification, phylogenetic analysis and expression profiling after Edwardsiella ictaluri infection

Molecular mechanism of Yersinia ruckeri Flagellin C (FliC) induced intestinal inflammation in channel catfish (Ictalurus punctatus)

Yersinia ruckeri is known to cause enteric red mouth disease (ERM) in channel catfish (Ictalurus punctatus). This study established a model of Y. ruckeri-induced intestinal inflammation in channel catfish. Subsequently, using quantitative polymerase chain reaction (qPCR), gene cloning, recombinant protein expression, protein molecular docking, and tissue pathology techniques, we investigated the role and molecular mechanism of Flagellin C (FliC) from Y. ruckeri in inducing inflammation. The findings indicated that FliC was the main virulence gene in Y. ruckeri responsible for inducing intestinal inflammation. Specifically, FliC bound to the host Toll-like receptor 5 (tlr5), leading to the upregulation of multiple inflammatory factors such as tumor necrosis factor (tnf)-α, interleukin (il)-6, and il-1β, and the activation of the nuclear factor-kappaB (NF-κB) and JAK-STAT signaling pathways, thereby initiating inflammation. The results were validated through experiments conducted both in cellular models and in vivo. In summary, this study identified FliC as a virulence gene in Y. ruckeri infection of channel catfish and elucidated its role in inducing intestinal inflammation.

Cloning and expression analysis of Janus activated kinase family genes from spotted seabass (Lateolabrax maculatus)

Janus kinases (JAKs) are important components of the JAK-STAT signaling pathway and play vital roles in innate immunity, autoimmune diseases, and inflammation. However, information about JAKs remains largely unknown in the spotted seabass, a fish species of Perciformes with great commercial value in the aquaculture industry. The aims of this study are to obtain the complete cDNA sequences of JAKs (JAK1, JAK2A, JAK2B, JAK3 and TYK2) from spotted seabass and to investigate their roles upon stimulation with lipopolysaccharides (LPS) and Edwardsiella tarda, using RT-PCR, PCR and qRT-PCR methods. All five JAK genes from the spotted seabass, each encode more than 1100 amino acids residues. JAK1 and JAK3 consist of 24 exons and 23 introns, whereas JAK2A, JAK2B and TYK2 consist of 23 exons and 22 introns. Furthermore, these five spotted seabass JAKs share high sequence identities with those of other fish species in protein domain analysis, synteny analysis, and phylogenetic analysis. Moreover, these five JAK genes were ubiquitously expressed in all tissues examined from healthy fish, and inducible expressions of JAKs were observed in the intestine, gill, head kidney, and spleen following LPS treatment or E. tarda infection. These findings indicate that all these JAK genes are involved in the antibacterial immunity of the spotted seabass and provide a basis for further understanding the mechanism of JAKs antibacterial response in the spotted sea bass.

Climate change can impair bacterial pathogen defences in sablefish via hypoxia-mediated effects on adaptive immunity

Low-oxygen levels (hypoxia) in aquatic habitats are becoming more common because of global warming and eutrophication. However, the effects on the health/disease status of fishes, the world's largest group of vertebrates, are unclear. Therefore, we assessed how long-term hypoxia affected the immune function of sablefish, an ecologically and economically important North Pacific species, including the response to a formalin-killed Aeromonas salmonicida bacterin. Sablefish were held at normoxia or hypoxia (100% or 40% air saturated seawater, respectively) for 6-16 weeks, while we measured a diverse array of immunological traits. Given that the sablefish is a non-model organism, this involved the development of a species-specific methodological toolbox comprised of qPCR primers for 16 key immune genes, assays for blood antibacterial defences, the assessment of blood immunoglobulin (IgM) levels with ELISA, and flow cytometry and confocal microscopy techniques. We show that innate immune parameters were typically elevated in response to the bacterial antigens, but were not substantially affected by hypoxia. In contrast, hypoxia completely prevented the ∼1.5-fold increase in blood IgM level that was observed under normoxic conditions following bacterin exposure, implying a serious impairment of adaptive immunity. Since the sablefish is naturally hypoxia tolerant, our results demonstrate that climate change-related deoxygenation may be a serious threat to the immune competency of fishes.

Molecular characterization, expression analysis and subcellular location of the members of STAT family from spotted seabass (Lateolabrax maculatus)

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway is a pervasive intracellular signal transduction pathway, involving in biological processes such as cell proliferation, differentiation, apoptosis and immune regulation. In this study, seven STAT genes, STAT1, STAT1-like, STAT2, STAT3, STAT4, STAT5a and STAT5b, were identified and characterized in spotted seabass (Lateolabrax maculatus). Analyses of multiple sequence alignment, genomic organization, phylogeny and conserved synteny were conducted to infer the evolutionary conservation of these genes in the STAT family. The results of the bioinformatics analysis assumed that STAT1 and STAT1-like might be homologous to STAT1a and STAT1b, respectively. Furthermore, the expression of the seven genes were detected in eight tissues of healthy spotted seabass, which revealed that they were expressed in a variety of tissues, mainly in gill, spleen and muscle, and extremely under-expression in liver. The expression of the seven genes in gill, head-kidney, spleen and intestine were significantly induced by lipopolysaccharide (LPS) or Edwardsiella tarda challenge. The expression of most of the LmSTATs were up-regulated, and the highest expression levels at 12 h after LPS stimulation, however, the LmSTATs were down-regulated by E. tarda infection. The results of subcellular localization show that the native LmSTAT1, LmSTAT1-like, LmSTAT2, LmSTAT3 and LmSTAT5a were localized in the cytoplasm, but they were translocated into the nucleus after LPS stimulation. Whereas, LmSTAT4 and LmSTAT5b were translocation into the nucleus whether with LPS stimulation or not. Overall, this is the first study to systematically revealed the localization of STAT members in fish, and indicated that LmSTATs participate in the process of protecting the host from pathogens invasion in the form of entry into nucleus.

Evolutionary, comparative, and functional analyses of STATs and regulation of the JAK-STAT pathway in lumpfish upon bacterial and poly(I:C) exposure

Background

The Janus kinase/signal transducers and activators of transcription (JAK-STAT) system regulates several biological processes by affecting transcription of genes as a response to cytokines and growth factors. In the present study, we have characterized the STAT genes in lumpfish (Cyclopterus lumpus L.), belonging to the order Perciformes, and investigated regulation of the JAK-STAT signaling pathway upon exposure to bacteria (Vibrio anguillarum) and poly(I:C), the latter mimicking antiviral responses.

Methods

Characterization and evolutionary analyses of the STATs were performed by phylogeny, protein domain, homology similarity and synteny analyses. Antibacterial and antiviral responses were investigated by performing KEGG pathway analysis.

Results

We observed that lumpfish have stat1a, 2, 3, 4, 5a, 5b, and 6. Transcriptome-wide analyses showed that most components of the JAK-STAT pathway were present in lumpfish. il-6, il-10, il-21, iκBα and stat3 were upregulated 6 hours post exposure (hpe) against bacteria while type I interferons (IFNs), irf1, irf3, irf10, stat1 and 2 were upregulated 24 hpe against poly(I:C).

Conclusions

Our findings shed light on the diversity and evolution of the STATs and the data show that the STAT genes are highly conserved among fish, including lumpfish. The transcriptome-wide analyses lay the groundwork for future research into the functional significance of these genes in regulating critical biological processes and make an important basis for development of prophylactic measure such as vaccination, which is highly needed for lumpfish since it is vulnerable for both bacterial and viral diseases.

Daily Rhythmicity of Muscle-Related and Rhythm Genes Expression in Mackerel Tuna (Euthynnus affinis)

The aim of this study was to investigate the circadian rhythm of muscle-related gene expression in mackerel tuna under different weather conditions. The experiment was carried out under two weather conditions at four sampling times (6:00, 12:00, 18:00, and 24:00) to determine the expression of growth, function, and rhythm genes: white muscle rhythm genes were rhythmic on sunny and cloudy days, except for PER3 and RORA; all functional genes had daily rhythmicity. Red muscle had daily rhythmicity on both sunny and cloudy days; functional genes had daily rhythmicity except for MBNL. The expression levels of the rhythm gene PER1 were determined to be significantly different by independent t-test samples in white muscle at 6:00, 12:00, 18:00, and 24:00 under different weather conditions; the expression levels of the functional genes MBNL and MSTN were both significantly different. In the red muscle, the expression of the rhythm genes PER3, REVERBA, and BMAL1 was determined by independent t-test samples at 6:00, 12:00, 18:00, and 24:00 on cloudy and sunny days; the functional gene MBNL was significantly different. The present study showed that mackerel tuna muscle rhythm genes and functional genes varied significantly in expression levels depending on weather, time of day, and light intensity and that the expression levels of myogenic genes were closely related to clock gene expression. The fish were also able to adapt to changes in light intensity in different weather conditions through positive physiological regulation.

Effects of diets rich in Agaricus bisporus polysaccharides on the growth, antioxidant, immunity, and resistance to Yersinia ruckeri in channel catfish

To promote the application of Agaricus bisporus polysaccharides (ABPs) in channel catfish (Ictalurus punctatus) culture, we evaluated the effects of ABPs on the growth, immunity, antioxidant, and antibacterial activity of channel catfish. When the amount of ABPs was 250 mg/kg, channel catfish's weight gain and specific growth rates increased significantly while the feed coefficient decreased. We also found that adding ABPs in the feed effectively increased the activities of ACP, MDA, T-SOD, AKP, T-AOC, GSH, and CAT enzymes and immune-related genes such as IL-1β, Hsp70, and IgM in the head kidney of channel catfish. Besides, long-term addition will not cause pathological damage to the head kidney. When the amount of ABPs was over 125 mg/kg, the protection rate of channel catfish was more than 60%. According to the intestinal transcriptome analysis, the addition of ABPs promoted the expression of intestinal immunity genes and growth metabolism-related genes and enriched multiple related KEEG pathways. When challenged by Yersinia ruckeri infection, the immune response of channel catfish fed with ABPs was intenser and quicker. Additionally, the 16S rRNA gene sequencing analysis showed that the composition of the intestinal microbial community of channel catfish treated with ABPs significantly changed, and the abundance of microorganisms beneficial to channel catfish growth, such as Firmicutes and Bacteroidota increased. In conclusion, feeding channel catfish with ABPs promoted growth, enhanced immunity and antioxidant, and improved resistance to bacterial infections. Our current results might promote the use of ABPs in channel catfish and even other aquacultured fish species.

Janus kinase 1 in Megalobrama amblycephala: Identification, phylogenetic analysis and expression profiling after Aeromonas hydrophila infection

Janus kinase 1 (JAK1), a member of the JAK family, plays an essential and non-redundant role in the mammalian immune system. However, the potential role of JAK1 in fish immune response remains largely unclear. In the present study, the JAK1 gene of Megalobrama amblycephala (MamJAK1) was identified and characterized. The open reading frame (ORF) of MamJAK1 was 3462 bp, encoding 1153 amino acids. MamJAK1 consists of four common domains of the JAK family, including B41, SH2, STyrKc (a pseudo kinase domain), and TyrKc (a kinase domain). Phylogenetic analysis showed that JAK1s are divided into two evolutionary clades, one containing fish JAK1s, and the other containing JAK1s from other vertebrates. The results of quantitative real-time PCR (qPCR) showed that in healthy M. amblycephala, MamJAK1 mRNA was highest expressed in blood, followed by spleen, intestine and mid-kidney, and lowly expressed in other tissues including gill, liver, head kidney, muscle, brain and heart. After Aeromonas hydrophila infection, the expression of MamJAK1 mRNA was significantly induced in four selected tissues including spleen, mid-kidney, liver and intestine, reaching a peak at 24 hpi (hour post infection) in spleen and mid-kidney, at 12 hpi in liver and at 4 hpi in intestine, and then the expression level was restricted to control levels at 72 or 120 hpi. In addition, the results of Western blot showed that the phosphorylation level of MamJAK1 protein in spleen and mid-kidney increased significantly after A. hydrophila infection, although MamJAK1 protein did not change obviously. Further, the JAK1 phosphorylation in Ctenopharyngodon idellus kidney (CIK) cells was found to be significantly induced by LPS stimulation and IL-6R over-expression. The results above suggest that MamJAK1 may play an essential role in the immune response against bacterial infection through the IL-6R mediated JAK1/STAT signaling pathway, which further deepen our understanding of JAK1 and provides a potential target for the treatment and prevention of bacterial diseases in teleost.

Integrative analysis of miRNA and mRNA expression associated with the immune response in the intestine of rainbow trout (Oncorhynchus mykiss) infected with infectious hematopoietic necrosis virus

Rainbow trout (Oncorhynchus mykiss), an economically important cold-water fish cultured worldwide, suffers from infectious hematopoietic necrosis virus (IHNV) infection, resulting in huge financial losses. In order to understand the immune response of rainbow trout during virus infection, we explored trout intestine transcriptome profiles following IHNV challenge, and identified 3355 differentially expressed genes (DEGs) and 80 differentially expressed miRNAs (DEMs). Transcriptome analysis revealed numerous DEGs involved in immune responses, such as toll-like receptor 3 (TLR3), toll-like receptor 7/8 (TLR7/8), tripartite motif-containing 25 (TRIM25), DExH-Box helicase 58 (DHX58), interferon-induced with helicase C domain 1 (IFIH1), interferon regulatory factor 3 (IRF3/7), signal transducer and activator of transcription 1 (STAT1) and heat shock protein 90-alpha 1 (HSP90A1). Integrated analysis identified five key miRNAs (miR-19-y, miR-181-z, miR-203-y, miR-143-z and miR-206-y) targeting at least two important immune genes (TRIM25, DHX58, STAT1, TLR7/8 and HSP90A1). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that DEGs and target genes were significantly enriched in various immune-related terms including immune system process, binding, cell part and pathways of Toll-like receptor signalling, RIG-I-like receptor signalling, NOD-like receptor signalling, JAK-STAT signalling, PI3K-Akt signalling, NF-kappa B signalling, IL-17 signalling and AGE-RAGE signalling. In addition, protein-protein interaction networks (PPI) was used to display highly interactive DEG networks involving eight immune-related pathways. The expression trends of 12 DEGs and 10 DEMs were further verified by quantitative real-time PCR, which confirmed the reliability of the transcriptome sequencing results. This study expands our understanding of the immune response of rainbow trout infected with IHNV, and provides valuable resources for future studies on the immune molecular mechanism and disease resistance breeding.

Nuclear and Morphological Alterations in Erythrocytes, Antioxidant Enzymes, and Genetic Disparities Induced by Brackish Water in Mrigal Carp (Cirrhinus mrigala)

Salinization of aquatic ecosystem, abrupt climate change, and anthropogenic activities cause adverse impact on agricultural land/soil as well as the aquaculture industry. This experimental study was designed to evaluate different biomarkers of oxidative stress, antioxidant enzymes, and genotoxic potential of diverse salinities of brackish water on freshwater fish. A total of 84 fresh water mrigal carp (Cirrhinus mrigala) were randomly segregated and maintained in four groups (T0, T1, T2, and T3) in a glass aquarium under similar laboratory conditions at various salinity levels (0, 3, 5, and 7 parts per thousand) to determine the pathological influence of brackish water. All the fish in groups T1, T2, and T3 were exposed to various salinity levels of brackish water for a period of 90 days while the fish of group T0 served as the control group. The experimental fish reared in different groups T1, T2, and T3 displayed various physical and behavioral ailments. The results revealed significantly augmented quantity of different oxidative stress indicators including reactive oxygen species (ROS) and thiobarbituric acid reactive substance (TBARS) in different visceral tissues (kidneys, liver, and gills) of exposed fish. Different antioxidant enzymes such as reduced glutathione (GSH), peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) along with total proteins were remarkably reduced in the kidneys, gills, and liver tissues. Results showed significantly increased values of different nuclear abnormalities (erythrocyte with micronucleus, erythrocyte with condensed nucleus, and erythrocyte with lobed nucleus) and morphological changes (pear shaped erythrocyte, spindle-shaped erythrocytes, and spherocyte) in red blood cells of experimental fish. The results on genotoxic effects exhibited significantly increased DNA damage in isolated cells of liver, kidneys, and gills of exposed fish. The findings of our experimental research suggested that brackish water causes adverse toxicological impacts on different visceral tissues of fresh water fish at higher salinity level through disruption and disorder of physiological and biochemical markers.

Identification of four STAT3 isoforms and functional investigation of IL-6/JAK2/STAT3 pathway in blunt snout bream (Megalobrama amblycephala)

Signal transducer and activator of transcription 3 (STAT3) is a major regulator of immune response and chronic inflammatory, which can be activated by interleukin-6 (IL-6). In mammals, STAT3 has multiple isoforms, and its function has been well studied. In teleost, a single stat3 has been cloned and identified in several species, but studies on its function are limited. In the present study, four stat3 isoforms including mastat3α1, mastat3α2, mastat3β1 and mastat3β2 were identified from blunt snout bream (Megalobrama amblycephala). The results of quantitative PCR (qPCR) showed that four mastat3 transcripts were ubiquitously expressed in all 10 tissues examined. After Aeromonas hydrophila challenge, the expression patterns of mastat3a1, mastat3a2 and mastat3β2 were similar, but significantly different from that of mastat3β1. In addition, western blot showed that rmaIL-6+rmasIL-6R (IL-6 trans-signaling) significantly up-regulated phosphorylation levels of the four maSTAT3 isoforms and mRNA levels of the il-10, il-11, tnf-a, socs3a and socs3b genes, while rmaIL-6 (IL-6 classical signaling) only significantly up-regulated phosphorylation levels of the two maSTAT3α isoforms and mRNA levels of the il-10, socs3a and socs3b genes. Meanwhile, overexpression or inhibition of JAK2 could significantly change the STAT3 phosphorylation. Finally, JAK2 and STAT3 inhibitors could significantly inhibit the up-regulation of il-10, il-11, tnf-a, socs3a and socs3b induced by rmaIL-6+rmasIL-6R or rmaIL-6. To sum up, this study reveals the functional distinctions and overlaps among the four maSTAT3 isoforms in blunt snout bream and reveals the differential regulation of IL-6 classical signaling and trans-signaling on downstream immune genes via the JAK2/STAT3 pathway, enriching our knowledge of fish's defense mechanisms against pathogens.

Evolution and expression analysis of STAT family members in blunt snout bream (Megalobrama amblycephala)

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway is involved in regulating the body's immunity, cell proliferation, differentiation, and apoptosis. Members of the STAT family have been extensively studied in different mammalian species. However, there are few studies on the STAT family genes in farmed economic fish. In this study, eight STAT genes including STAT1a, STAT1b, STAT2, STAT3, STAT4, STAT5a, STAT5b and STAT6, in blunt snout bream (Megalobrama amblycephala), an economically important fish in China, were identified and characterized. Analyses of gene location, phylogeny and conserved synteny were conducted to infer the evolutionary origin of these STAT family genes. Furthermore, the evolutionary origin model of STATs was constructed based on the 2R hypothesis and teleost genome duplication (TGD) hypothesis, which clarified the evolutionary origin of the eight STATs in blunt snout bream. Besides, expression of the eight STATs was detected in 10 tissues of healthy blunt snout bream, which showed different expression patterns, and all had the highest level in the blood. In addition, expression of the STATs was significantly induced in the spleen, liver, and kidney after infection of Aeromonas hydrophila, suggesting that they play an important role in protecting the host from pathogens. In general, the evolution of cytokine-related genes parallels that of the immune system, which has likely been a main evolutionary driver. Therefore, the evolutionary model of STAT genes, constructed in the non-model organism pioneeringly, may provide some enlightenment for the evolution of the fish STAT family genes and their involvement in the immune function.

Molecular identification of an androgen receptor and the influence of long-term aggressive interaction on hypothalamic genes expression in black rockfish (Sebastes schlegelii)

This study aims to explore the mechanism on how aggressive interaction alters reproductive physiology by testing whether aggressive interaction can activate the reproductive neuroendocrine function via the hypothalamus-pituitary-gonadal (HPG) axis in black rockfish (Sebastes schlegelii). The expressions of the androgen receptor gene (ar) and gonadotropin-releasing hormone genes (gnrhs), the concentration of plasma androgens, and GSI (the ratio of testes mass to body mass) were compared between the interaction group (dominant males or subordinate males) and the isolation group in male black rockfish after 3 weeks. A full-length cDNA encoding an androgen receptor (AR) of 766 amino acids was isolated. Transcripts encoding this AR were detected at a high relative abundance in the liver, kidney, testis, ovary, muscle, and intestine tissue. Further evaluation of brain genes transcripts abundance revealed that the mRNA levels of gnrh I and ar genes were significantly different between the interaction group and the isolation group in the hypothalamus. However, no significant difference was detected in testosterone, 11-keto-testosterone, and GSI between these two groups. This study indicates that a long-term aggressive interaction affect the expression of hypothalamic gnrh I and ar but may not change the physiological function of the HPG axis in an all-male condition.

Type I interferons in ray-finned fish (Actinopterygii)

Interferons (IFNs) are proteins of vital importance in the body's immune response. They are formed in different types of cells and have been found in fish, amphibians, reptiles and mammals. Two types of IFN have been found in ray-finned fish (Superclass: Osteichthyes, Class: Actinopterygii) so far, i.e. IFN type I (IFN I) and IFN type II (IFN II), while the presence of IFN type III (IFN III), which is found in phylogenetically older cartilaginous fishes, was not confirmed in this taxonomic group of vertebrates. Currently, type I IFN in Actinopterygii is divided into three groups, I, II and III, within which there are subgroups. These cytokines in these animals show primarily antiviral activity through the use of a signalling pathway JAK-STAT (Janus kinases - Signal transducer and activator of transcription) and the ability to induce ISG (IFN-stimulated genes) expression, which contain ISRE complexes (IFN-stimulated response elements). On the other hand, in Perciformes and Cyprinidae, it was found that type I/I interferons also participate in the antimicrobial response, inter alia, by inducing the expression of the inducible nitric oxide synthase (iNOS) and influencing the production of reactive oxygen species (ROS) in cells carrying out the phagocytosis process.

Evaluation of Oxidative stress, antioxidant enzymes and genotoxic potential of bisphenol A in fresh water bighead carp (Aristichthys nobils) fish at low concentrations

Bisphenol A (BPA) is one of the emerging contaminants associated with deleterious health effects on both public and wildlife and is extensively incorporated into different industrial products. Therefore, the current trial was conducted to determine the oxidative stress, status of different antioxidant enzymes and genotoxic potential of bisphenol A in fresh water fish at low concentrations. For this purpose, a total of 80 fresh water bighead carp (Aristicthys nobilis) received from commercial fish center were randomly divided and kept in four groups (A-D). Fish in groups (B-D) were exposed to different levels of BPA for a period of 60 days while fish of group A served as control group. Treated fish exhibited different physical and behavioral ailments in a time and treatment manners. Results showed significantly (p < 0.05) increased quantity of different oxidative stress biomarkers such as thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH) and the contents of reactive oxygen species (ROS) in gills, liver, kidneys and brain of exposed fish. Concentration of different antioxidant enzymes like catalase, superoxide dismutase, peroxidase and total proteins was significantly (p < 0.05) decreased in gills, liver, kidneys and brain of exposed fish. Results showed significantly (p < 0.05) increased frequency of morphological alterations, nuclear changes in red blood cells and increased DNA damage potential of bisphenol A in gills, liver, kidneys and brain tissues. The current trial concludes that even at very low concentrations bisphenol A causes toxic effects via turbulences in physiological and biochemical parameters in multiple tissues of fish.

miR-525-5p Modulates Proliferation and Epithelial-Mesenchymal Transition of Glioma by Targeting Stat-1

Background

Glioma is the most aggressive human brain tumor. Recent studies revealed that microRNAs play vital roles in glioma. However, the function of microRNA-525-5p (miR-525-5p) in glioma remains unclear.

Methods

qRT-PCR and Western blotting were used to evaluate mRNA and protein levels in glioma tissues and cells. Colony formation, CCK-8, and Edu assays evaluated the growth of glioma cells. Wound-healing, transwell, and 3D invasion assays examined the migration and invasion activities of glioma cells. Luciferase reporter assays assessed the regulatory relationship interaction between miR-525-5p and Stat-1. A mouse xenograft model was used to examine the effect of miR-525-5p on glioma in vivo.

Results

miR-525-5p expression was downregulated in glioma tissues and cells. Overexpressing miR-525-5p decreased the growth of glioma cells and reduced the migration, invasion, and epithelial–mesenchymal transition of glioma cells. Bioinformatics analysis identified Stat-1 as a potential target of miR-525-5p, and dual luciferase reporter assays revealed that miR-525-5p negatively regulates Stat-1. Decreased Stat-1 led to the inhibition of FOXM1, affecting NF-κB signaling activity. Overexpressing miR-525-5p reduced tumor development in vivo.

Conclusion

miR-525-5p negatively regulates cell proliferation, migration, invasion, and epithelial–mesenchymal transition in glioma, and Stat 1 is a target of miR-525-5p. miR-525-5p may be a potential target for glioma treatment.

Molecular insight, expression profile and subcellular localization of two STAT family members, STAT1a and STAT2, from Japanese eel, Anguilla japonica

Signal transducer and activator of transcription 1 (STAT1) and STAT2 are critical components of type I and type II IFNs signaling. To date, seven STAT family proteins have been identified from mammals. However, the information on STAT genes in teleost fish is still limited. In the present study, two STAT family genes (STAT1a and STAT2) were identified from Japanese eel, Anguilla japonica and designated as AjSTAT1a and AjSTAT2. The open reading frames of AjSTAT1a and AjSTAT2 are 2244 bp and 2421 bp, encoding for polypeptides of 747 aa and 806 aa, respectively. Both AjSTAT1a and AjSTAT2 contain the conserved domains of STAT proteins. Phylogenetic analysis was performed based on the STATs protein sequences, and showed that AjSTAT1a and AjSTAT2 shared the closest relationship with Oncorhynchus mykiss. Quantitative real-time PCR analysis revealed that AjSTAT1a and AjSTAT2 were expressed in most examined tissues, with the highest expression both in blood. Significantly up-regulated transcripts of AjSTAT1a and AjSTAT2 were detected in response to poly I:C stimulation, and Edwardsiella tarda induced increase in the expression of AjSTAT1a and AjSTAT2 genes. Subcellular localization analysis showed that in both IFNγ-stimulated and unstimulated EPC cells AjSTAT1a and AjSTAT2 were mainly distributed in the cytoplasm, but few AjSTAT1a was distributed in the nucleus. All these results suggested that AjSTAT1a and AjSTAT2 may be critical for regulating the host innate immune defense against pathogens invasion.

Functional characterization of a group II interferon, IFNc in the perciform fish, Nile tilapia (Oreochromis niloticus)

Interferons are a family of class II α-helical cytokines playing vital roles in antiviral immune response, and little information is available to date regarding the interferon system of tilapia. In this study, a type I IFN gene, named On-IFNc, was identified in Nile tilapia, Oreochromis niloticus. The predicted protein of On-IFNc contains several structural features known in type I IFNs, and On-IFNc was clustered together with the known IFNc in fish into a separated clade in the phylogenetic tree. On-IFNc gene was constitutively expressed in all tissues examined, with the highest expression level observed in liver, and was rapidly induced in all organs/tissues tested following the stimulation of poly(I:C). In addition, recombinant On-IFNc has been proven to markedly induce the expression of the antiviral effectors, Mx and viperin, the signalling components, STAT1, STAT2, and IRF9, and the transcription factors, IRF3 and IRF7, as well as the tyrosine phosphorylation of STAT1 and STAT2 in fish cells. Furthermore, recombinant On-IFNc has been proven to possess antiviral activity against ISKNV. The present study thus contributes to a better understanding of the functional properties of the type I IFN system in tilapia.

Vitamin D3 modulates yellow catfish (Pelteobagrus fulvidraco) immune function in vivo and in vitro and this involves the vitamin D3/VDR-type I interferon axis

Vitamin D₃ (VD₃) has been shown to regulate immune function in mammals. 1,25-dihydroxyvitamin (1,25(OH)₂D₃) is the active form of vitamin D₃, which is also known as calcitriol. The current study investigated the immunomodulatory effects of 1,25(OH)₂D₃ on the innate immune response of yellow catfish (Pelteobagrus fulvidraco) after in vivo and in vitro immune challenge. The in vivo results showed that increasing dietary vitamin D₃ decreased mortality, enhanced the immune protective rate, and increased serum lysozyme, catalase and SOD activities in yellow catfish infected with Edwardsiella Ictaluri (p < 0.05). The in vitro results showed that 1,25(OH)₂D₃ (0, 1, 10, 100, 200 pM) dose-dependently attenuated the rate of apoptosis and production or reactive oxygen species and increased the phagocytic activity of head kidney macrophages stimulated with 10 mg/L lipopolysaccharide (LPS) and 100 mg/L of Poly(I:C) (p < 0.05). Real-time quantitative PCR results showed that increasing dietary vitamin D₃ content in vivo and increasing the level of 1,25(OH)₂D₃in vitro partially regulated the expression of VD₃/VDR-type I interferon axis genes (vdr, irf-3, ifn-a, jak1, stat1, ifi56 and ifp35) after immune challenge. These results indicated that vitamin D₃ content helped yellow catfish to resist oxidative stress and inflammation caused by immune challenge, and immunomodulation involved the VD₃/VDR-type I interferon action axis.

Molecular characterization and expression analysis of signal transducer and activator of transcription 1 (STAT1) in Japanese eel Anguilla japonica

Signal transducer and activator of transcription 1 (STAT1) is one of critical signal transduction proteins of interferon (IFN) pathway and the structure and function of this protein have been well identified in mammals, but the information about the STAT1 is still limited in teleost fishes. In the present study, the full-length cDNA sequence of STAT1 (AjSTAT1) in Japanese eel (Anguilla japonica) was identified and characterized. Multiple alignment of the amino acid sequence showed that the AjSTAT1 protein has the typical conserved domains including the amino-terminal, coiled-coil, DNA-binding, linker, Src homology 2 (SH2), transcriptional activation domains (TAD). Quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed a broad expression for AjSTAT1 in a wide range of tissues, with the predominant expression in liver, followed by the spleen, intestine, gills, skin, kidney, and the very low expression in heart and muscle. The AjSTAT1 expressions in liver, spleen and kidney were significantly induced following injection with LPS, the viral mimic poly I:C, and Aeromonas hydrophila infection. In vitro, the AjSTAT1 transcripts of Japanese eel liver cells were significantly enhanced by the treatment of poly I:C or the stimulation of the high concentration of Aeromonas hydrophila (1 × 10⁷ cfu/mL and 1 × 10⁸ cfu/mL). Subcellular localization showed that in the natural state AjSTAT1was uniformly distributed in the cytoplasm, but AjSTAT1 was found to aggregated in the cytoplasm as well as partly in the nucleus after the stimulation of LPS and poly I:C. These results collectively suggested AjSTAT1 is an important transcription factor possibly involved in Japanese eel defense against viral and bacterial infection.

Cloning, expression prolife, and immune characterization of a novel stat family member (stat5bl) in Chinese tongue sole (Cynoglossus semilaevis)

STAT plays important roles in innate immunity during JAK/STAT signaling pathway, and STAT5 is particularly focused due to the existence of duplicated forms in fish and mammal. In Chinese tongue sole, stat5bl was suggested to be a candidate related to Vibrio harveyi resistance based on previous QTL screening. In this study, the full length of stat5bl cDNA was cloned and its expression patterns were analyzed. stat5bl was predominantly expressed in immune tissues, where the highest level was observed in liver, followed by skin and gill. Time course expression patterns were examined in six tissues (liver, skin, gill, kidney, intestine, spleen) after V. harveyi infection. stat5bl could be up-regulated by V. harveyi infection in all tissues except liver, despite the timepoints of peak were different. In contrast, stat5bl was significantly downregulated in liver. To elucidate the role of stat5bl in liver, in vitro RNAi were performed using primary liver cell culture. Knockdown of stat5bl could regulate the expression of genes closely related to JAK/STAT pathway. This study would enlarge our understanding of stat5bl in fish immunity.

Increased Alternative Splicing as a Host Response to Edwardsiella ictaluri Infection in Catfish

Alternative splicing is the process of generating multiple transcripts from a single pre-mRNA used by eukaryotes to regulate gene expression and increase proteomic complexity. Although alternative splicing profiles have been well studied in mammalian species, they have not been well studied in aquatic species, especially after biotic stresses. In the present study, genomic information and RNA-Seq datasets were utilized to characterize alternative splicing profiles and their induced changes after bacterial infection with Edwardsiella ictaluri in channel catfish (Ictalurus punctatus). A total of 27,476 alternative splicing events, derived from 9694 genes, were identified in channel catfish. Exon skipping was the most abundant while mutually exclusive exon was the least abundant type of alternative splicing. Alternative splicing was greatly induced by E. ictaluri infection with 21.9% increase in alternative splicing events. Interestingly, genes involved in RNA binding and RNA splicing themselves were significantly enriched in differentially alternatively spliced genes after infection. Sequence analyses of splice variants of a representative alternatively spliced gene, splicing factor srsf2, revealed that certain spliced transcripts may undergo nonsense-mediated decay (NMD), suggesting functional significance of the induced alternative splicing. Although statistical analysis was not possible with such large datasets, results from quantitative real-time PCR from representative differential alternative splicing events provided general validation of the bacterial infection-induced alternative splicing. This is the first comprehensive study of alternative splicing and its changes in response to bacterial infection in fish species, providing insights into the molecular mechanisms of host responses to biotic stresses.

A Review of Molecular Responses of Catfish to Bacterial Diseases and Abiotic Stresses

Catfish is one of the major aquaculture species in the United States. However, the catfish industry is threatened by several bacterial diseases such as enteric septicemia of catfish (ESC), columnaris disease and Aeromonas disease, as well as by abiotic stresses such as high temperature and low oxygen. Research has been conducted for several decades to understand the host responses to these diseases and abiotic stresses. With the development of sequencing technologies, and the application of genome-wide association studies in aquaculture species, significant progress has been made. This review article summarizes recent progress in understanding the molecular responses of catfish after bacterial infection and stress challenges, and in understanding of genomic and genetic basis for disease resistance and stress tolerance.