The roles of two myostatins and immune effects after inhibition in Qi river crucian carp (Carassius auratus)

Roles of β-catenin in innate immune process and regulating intestinal flora in Qi river crucian carp (Carassius auratus)

In mammals, β-catenin participates in innate immune process through interaction with NF-κB signaling pathway. However, its role in teleost immune processes remains largely unknown. We aimed to clarify the function of β-catenin in the natural defense mechanism of Qi river crucian carp (Carassius auratus). β-catenin exhibited a ubiquitous expression pattern in adult fish, as indicated by real-time PCR analysis. Following lipopolysaccharide (LPS), Polyinosinic-polycytidylic acid (polyI: C) and Aeromonas hydrophila (A. hydrophila) challenges, β-catenin increased in gill, intestine, liver and kidney, indicating that β-catenin likely plays a pivotal role in the immune response against pathogen infiltration. Inhibition of the β-catenin pathway using FH535, an inhibitor of Wnt/β-catenin pathway, resulting in pathological damage of the gill, intestine, liver and kidney, significant decrease of innate immune factors (C3, defb3, LYZ-C, INF-γ), upregulation of inflammatory factors (NF-κB, TNF-α, IL-1, IL-8), and downregulation of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities, increase of Malondialdehyde (MDA) content. Following A. hydrophila invasion, the mortality rate in the FH535 treatment group exceeded that of the control group. In addition, the diversity of intestinal microflora decreased and the community structure was uneven after FH535 treatment. In summary, our findings strongly suggest that β-catenin plays a vital role in combating pathogen invasion and regulating intestinal flora in Qi river crucian carp.

α-lipoic acid ameliorates hepatotoxicity induced by chronic ammonia toxicity in crucian carp (Carassius auratus gibelio) by alleviating oxidative stress, inflammation and inhibiting ERS pathway

High environment ammonia (HEA) poses a deadly threat to aquatic animals and indirectly impacts human healthy life, while nutritional regulation can alleviate chronic ammonia toxicity. α-lipoic acid exhibits antioxidative effects in both aqueous and lipid environments, mitigating cellular and tissue damage caused by oxidative stress by aiding in the neutralization of free radicals (reactive oxygen species). Hence, investigating its potential as an effective antioxidant and its protective mechanisms against chronic ammonia stress in crucian carp is highly valuable. Experimental fish (initial weight 20.47 ± 1.68 g) were fed diets supplemented with or without 0.1% α-lipoic acid followed by a chronic ammonia exposure (10 mg/L) for 42 days. The results revealed that chronic ammonia stress affected growth (weight gain rate, specific growth rate, and feed conversion rate), leading to oxidative stress (decreased the activities of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase; decreased total antioxidant capacity), increased lipid peroxidation (accumulation of malondialdehyde), immune suppression (decreased contents of nonspecific immune enzymes AKP and ACP, 50% hemolytic complement, and decrease of immunoglobulin M), impaired ammonia metabolism (reduced contents of Glu, GS, GSH, and Gln), imbalance of expression of induced antioxidant-related genes (downregulation of Cu/Zu SOD, CAT, Nrf2, and HO-1; upregulation of GST and Keap1), induction of pro-apoptotic molecules (transcription of BAX, Caspase3, and Caspase9), downregulation of anti-apoptotic gene Bcl-2 expression, and induction of endoplasmic reticulum stress (upregulation of IRE1, PERK, and ATF6 expression). The results suggested that the supplementation of α-lipoic acid could effectively induce humoral immunity, alleviate oxidative stress injury and endoplasmic reticulum stress, and ultimately alleviate liver injury induced by ammonia poisoning (50-60% reduction). This provides theoretical basis for revealing the toxicity of long-term ammonia stress and provides new insights into the anti-ammonia toxicity mechanism of α-lipoic acid.

Effects of Myostatin b Knockout on Offspring Body Length and Skeleton in Yellow Catfish (Pelteobagrus fulvidraco)

Based on obtaining mstnb gene knockout in Pelteobagrus fulvidraco, a study on the effect of the mstn gene on skeletal morphology and growth was performed by comparing the number and length of the vertebrae of mutant and wild-type fish in a sibling group of P. fulvidraco, combined with the differences in cells at the level of vertebral skeletal tissue. It was found that mstnb gene knockdown resulted in a reduction in the number of vertebrae, the length, and the intervertebral distance in P. fulvidraco, and these changes may be the underlying cause of the shorter body length in mutant P. fulvidraco. Further, histological comparison of the same sites in the mstn mutant and wild groups of P. fulvidraco also revealed that the number and density of osteocytes were greater in mstnb knockout P. fulvidraco than in wild-type P. fulvidraco. Our results demonstrated that when using genome editing technology to breed new lines, the effects of knockout need to be analyzed comprehensively and may have some unexpected effects due to insufficient study of the function of certain genes.

A Potential Negative Regulatory Function of Myostatin in the Growth of the Pacific Abalone, Haliotis discus hannai

Myostatin, also known as GDF8, is a member of the transforming growth factor-β (TGF-β) superfamily. In vertebrates, myostatin negatively regulates the growth of skeletal muscle. In invertebrates, it has been reported to be closely related to animal growth. However, knowledge concerning the molecular mechanisms involved in the myostatin regulation of molluscan growth is limited. In this study, we found that the hdh-myostatin open reading frame (ORF) comprised 1470 base pairs that encoded 489 amino acids and contained structural characteristics typical of the TGF-β superfamily, including a C-terminal signal peptide, a propeptide domain, and TGF-β region. Gene expression analysis revealed that hdh-myostatin mRNA was widely expressed at different levels in all of the examined tissues of Haliotis discus hannai. Nine single nucleotide polymorphisms (SNPs) were associated with the growth traits. RNA interference (RNAi) against hdh-myostatin mRNA significantly downregulated hdh-myostatin at days 1, 15, and 30 post injection, and the pattern was correlated with downregulation of the genes TGF-β receptor type-I (hdh-TβR I), activin receptor type-IIB (hdh-ActR IIB), and mothers against decapentaplegic 3 (hdh-Smad3). After one month of the RNAi experiment, the shell lengths and total weights increased in the abalone, Haliotis discus hannai. The results of qRT-PCR showed that the hdh-myostatin mRNA level was higher in the slow-growing group than in the fast-growing group. These results suggest that hdh-myostatin is involved in the regulation of growth, and that these SNPs would be informative for further studies on selective breeding in abalone.

Enhanced Muscle Fibers of Epinephelus coioides by Myostatin Autologous Nucleic Acid Vaccine

Epinephelus coioides is a fish species with high economic value due to its delicious meat, high protein content, and rich fatty acid nutrition. It has become a high-economic fish in southern parts of China and some other Southeast Asian countries. In this study, the myostatin nucleic acid vaccine was constructed and used to immunize E. coioides. The results from body length and weight measurements indicated the myostatin nucleic acid vaccine promoted E. coioides growth performance by increasing muscle fiber size. The results from RT-qPCR analysis showed that myostatin nucleic acid vaccine upregulated the expression of myod, myog and p21 mRNA, downregulated the expression of smad3 and mrf4 mRNA. This preliminary study is the first report that explored the role of myostatin in E. coioides and showed positive effects of autologous nucleic acid vaccine on the muscle growth of E. coioides. Further experiments with increased numbers of animals and different doses are needed for its application to E. coiodes aquaculture production.

Characterization and functional analysis of myostatin and myogenin genes involved in temperature variation and starvation stress in Golden pompano, Trachinotus blochii

Animal growth and development is a complicated process and is regulated by multi-genes. Myostatin (Mstn) and myogenin (Myog) are a pair of negative and positive regulators respectively, which play an important role in the generation of muscle cells. In order to study the function of these two genes in muscle growth of Trachinotus blochii, full lengths of two mstn genes (mstn-1 and mstn-2) and myog gene were cloned using RACE. We first identified and characterized the complete cDNA sequences of mstn-1, mstn-2, and myog genes derived from T. blochii, an economically important mariculture species in China. Multiple sequence alignment of amino acids and phylogenetic analysis revealed that the Mstn and Myog were highly conserved to the other Perciformes. In addition, gene duplication of mstn in T. blochii was observed. mstn-1 mRNA was mainly expressed in the muscle and gonad, while mstn-2 and myog transcripts were detectable mainly in the brain and muscle, respectively. Moreover, the nutritional status and temperature influenced abundance levels in brain and muscle. Results suggested that mstn and myog genes play an important role in muscle growth of T. blochii, mstn may not be limited to control of muscle growth in fish and could also be involved in other biological functions.

Effects of ammonia toxicity on the histopathology, detoxification, oxidative stress, and immune response of the cuttlefish Sepia pharaonis and the mitigation of γ-aminobutyric acid

In this study, γ-aminobutyric acid (GABA) was examined as an additional supplement to improve the ammonia stress resistance of S. pharaonis. Specifically, we added different doses of GABA (0, 20, 40, 60, 80, and 100 mg/kg) to food, cultivated S. pharaonis in regular seawater for 8 weeks and then in 8.40 mg/L ammonia seawater for 48 h and then investigated the accumulation of ammonia (the hepatic ammonia content), ammonia detoxification process (the urea content), antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT) enzyme activities), immune response (the serum haemolytic complement (C3) and lysozyme (LYZ) contents), membrane lipid peroxidation (malondialdehyde (MDA)) and histopathology of the liver. The results showed that ammonia poisoning could induce ammonia and MDA accumulation and subsequently lead to oxidative stress (decreases in SOD and CAT activities), immunosuppression (reductions in the haemolytic C3 and LYZ content), and histopathological injury in the liver. The application of GABA had a significant effect on alleviating the adverse effect of ammonia poisoning, and 80-100 mg/kg treatment exerted the best effect. This treatment significantly reduced the ammonia and MDA contents, significantly increased the urea content, increased the SOD, CAT, C3 and LYZ activities, reduced the MDA content, suppressed membrane lipid peroxidation, and significantly improved the histopathological injury to the liver. In summary, the results could provide a new method for mitigating liver damage, alleviating the physiological and metabolic disorders caused by ammonia stress in cuttlefish, and provide a theoretical basis for the application of GABA in alleviating ammonia poisoning.

Myostatin mutation causing double muscling could affect increased psoroptic mange sensitivity in dual purpose Belgian Blue cattle

Belgian Blue cattle are known for their high degree of muscling and good carcass qualities. This high degree of muscling is mainly caused by a mutation in the myostatin gene (MSTN). Although the MSTN mutation is considered as fixed in the Belgian Blue breed, segregation is occurring in a sub-population bred for dual purpose. In the latter population, we observed an association between the mutation in MSTN and susceptibility to psoroptic mange, a skin disease caused by Psoroptes ovis mites that heavily plagues Belgian Blue cattle. In total, 291 animals were sampled and screened for their susceptibility for mange lesions and their MSTN genotype. Via linear mixed modelling, we observed that homozygous mutant animals had a significant increase in the size of mange lesions (+2.51% lesion extent) compared to homozygous wild type. These findings were confirmed with zero-inflated modelling, an animal model and odds analysis. Risk ratios for developing severe mange lesions were 5.9 times as high for homozygous mutant animals. All analyses confirmed an association between the MSTN genotype and psoroptic mange lesion size.

Tartrazine exposure results in histological damage, oxidative stress, immune disorders and gut microbiota dysbiosis in juvenile crucian carp (Carassius carassius)

Tartrazine (TZ) is an azo dye widely used in foods, cosmetics, beverages, textile, and leather. In recent years, there are reports on detecting azo dyes in the aquatic environment, so the impact of these compounds on aquatic organisms could not be ignored. In this study, we aimed to evaluate the adverse effects of TZ exposure on teleosts' embryo development and juvenile's health by using crucian carp (Carassius carassius) as the experimental fish. The results showed that embryos exposed to TZ (0.19, 0.76 and 1.5 mM) exhibited a deformity, delayed egg resorption and decreased fertilization and hatching rate. When the juvenile fish were exposed to TZ at a level higher than those present in water for 30 days caused severe histopathological damages of the gill, intestine, kidney and liver. Antioxidant enzymes (CAT, SOD and GSH-Px) activities in the gill, intestine and liver, exhibited a decreasing trend after TZ exposure, while MDA contents elevated. TZ exposure also resulted in the upregulation of pro-inflammatory cytokines (il1 and il6), lysozymes (lyz), complement component 3 (c3), and β-defensin 3 (defb3). In addition, TZ exposure also affected the intestinal microbiota structure. In summary, the data in the present study indicated that TZ exposure  reduce the embryo fertilization and hatching rate; cause histopathological damage of tissues, trigger oxidative stress, innate immune disorders and dysbiosis of gut microbiota in juvenile crucian carp. Therefore, it is necessary to be informed about the hazards of TZ exposure and the discharge of the dye into waters should be strictly administrated to prevent environmental pollution.

A potential negative regulation of myostatin in muscle growth during the intermolt stage in Exopalaemon carinicauda

Muscle growth in crustacean is a complicated process where the muscle grows and develops through muscle restoration, and the growth rate depends on the net muscle gain during molting. Myostatin (MSTN) is a conserved inhibitor of muscle growth in vertebrates, but until now solid evidence supporting a similar function of MSTN in invertebrates has been lacking. In this study, we identified and characterized MSTN from the shrimp Exopalaemon carinicauda (EcMSTN) to better understand its biological function. The full-length cDNA of EcMSTN was 1,518 bp, encoding 428 amino acid residues, and the genomic sequence was 1,851 bp, including three exons and two introns. EcMSTN was expressed in a wide range of tissues, but predominantly detected in the abdominal muscle (P < 0.05). Low expression was detected in the cleavage, blastula and gastrula stages in the early development stages, increasing after the nauplius stage. EcMSTN expression was negatively correlated with the growth traits. After EcMSTN knockdown using RNA interference, EcMSTN expression was down-regulated in the abdominal muscle and up-regulated the expression of growth-related genes, including fast myosin heavy chain and skeletal muscle actin 3. After inhibiting EcMSTN for 5 weeks, the RNAi-treated shrimp with reduced EcMSTN levels exhibited a dramatically higher body weight compared with that of the control group. Association analysis revealed that two SNP loci g.Mstn220 and g.Mstn567 were markedly associated with both body weight and body length. The results would clarify the negative role of EcMSTN in regulating muscle growth during the intermolt stage and provide growth-related markers for molecular marker assisted breeding of E. carinicauda.