Molecular Mechanisms Regulating Muscle Plasticity in Fish

Characterization of the myostatin gene in the neotropical species Piaractus mesopotamicus and the possibility of its use in genetic improvement programs

BACKGROUND

The myostatin gene has played an important role in the genetic improvement of the main species of economic importance; however, it has not yet been described for some Neotropical fish essential for aquaculture. This study aimed to characterize the myostatin gene of pacu, Piaractus mesopotamicus, and investigate the association of a microsatellite marker in this gene with the weight of fish.

METHODS AND RESULTS

The myostatin gene sequence was obtained after following a RACE-PCR strategy based on a partial mRNA sequence available in the GenBank database and the alignment of myostatin sequences from other fish species. The obtained sequence for the P. mesopotamicus gene was analyzed for short tandem repeats, and one dinucleotide was observed at the 3´untranslated region. A short tandem repeat polymorphism was verified in a wild population. Subsequently, the STR was evaluated in a test population of 232 animals in two 220 m² concrete tanks at the Aquaculture Center of Unesp. Eight alleles and 22 genotype combinations were identified. A significant association was observed between microsatellite marker polymorphisms and the weight traits (WEIGHT1 and WEIGHT2). Alleles 210, 222, 226, and 230 were found to favor weight gain.

CONCLUSIONS

In summary, this study contributes to the characterization of the myostatin gene in pacu fish and identifies an association between a STR and weight traits. Thus, this gene could be used as a target for genetic breeding using molecular strategies such as CRISPR and quantitative strategies such as marker-assisted selection, which would contribute to improving the production of the species.

Dietary supplementation with succinic acid improves growth performance and flesh quality of adult Nile tilapia (Oreochromis niloticus) fed a high-carbohydrate diet

To evaluate the effects of dietary supplementation with succinic acid on growth performance, flesh quality, glucose, and lipid metabolism of Nile tilapia (Oreochromis niloticus) fed a high-carbohydrate diet (HCD), five iso-nitrogenous and iso-lipidic diets were prepared as follows: HCD (control group) consisting of 55% corn starch and HCD supplemented with 0.5%, 1.0%, 2.0%, and 4.0% succinic acid, respectively. Tilapia with an initial body weight of 204.90 ± 1.23 g randomly assigned to 15 tanks with 3 replicates per group and 10 fish per tank fed for 8 weeks. Increasing dietary succinic acid supplementation resulted in significant second-order polynomial relationship in the weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency rate (PER), viscerosomatic index, condition factor, and contents of muscular crude lipid and glycogen (P < 0.05). The hepatosomatic index, mesenteric fat index, liver glycogen content and crude lipid contents of the whole-body and liver demonstrated significantly linear and second-order polynomial relationship (P < 0.05). Quadratic curve model analysis based on WGR, SGR, PER, and FCR demonstrated that optimal supplementation with succinic acid in the HCD of Nile tilapia ranged from 1.83% to 2.43%. Fish fed with 1.0% succinic acid had higher muscular hardness, increased the contents of alkali-soluble hydroxyproline in collagen, docosahexaenoic acid (DHA) and n-3 polyunsaturated fatty acid (n-3PUFA) in muscle, and lower total fatty acid content in muscle (P < 0.05) compared with the control group. Compared to the control group, dietary supplementation with 1.0% succinic acid significantly increased the contents of total bounding amino acid (arginine, histidine, isoleucine, lysine, methionine, alanine, proline), total flavor amino acid (free aspartic acid), the catalase (CAT) activity and total antioxidant capacity, and the mRNA relative expression levels of CAT, superoxide dismutase (SOD), and nuclearfactor erythroidderived 2-like 2 (Nrf2) in muscle (P < 0.05). Furthermore, succinic acid supplementation significantly up-regulated mRNA relative expression levels of glycolysis genes (hexokinase 2 [HK2], phosphofructokinase, muscle-A [PFKMA], and phosphofructokinase, muscle-B [PFKMB]), a key glycogen synthesis gene (glycogen synthase [GYS]), and lipid catabolism genes (carnitine palmitoyltransferase-1B [CPT1B], hormone sensitive lipase [HSL], and lipoprotein lipase [LPL]), while down-regulating the mRNA relative expression level of fatty acid synthase (FASN) in muscle (P < 0.05). In conclusion, dietary supplementation with 1.83% to 2.43% succinic acid improved muscle quality by increasing muscle antioxidant capacity and hardness, changing muscle amino acid and fatty acid composition, and regulating muscle glucose and lipid metabolism.

DNA Methylation Profiling in Genetically Selected Clarias magur (Hamilton, 1822) Provides Insights into the Epigenetic Regulation of Growth and Development

DNA methylation is an epigenetic alteration that impacts gene expression without changing the DNA sequence affecting an organism's phenotype. This study utilized a reduced representation bisulfite sequencing (RRBS) approach to investigate the patterns of DNA methylation in genetically selected Clarias magur stocks. RRBS generated 249.22 million reads, with an average of 490,120 methylation sites detected in various parts of genes, including exons, introns, and intergenic regions. A total of 896 differentially methylated regions (DMRs) were identified; 356 and 540 were detected as hyper-methylated and hypo-methylated regions, respectively. The DMRs and their association with overlapping genes were explored using whole genome data of magur, which revealed 205 genes in exonic, 210 in intronic, and 480 in intergenic regions. The analysis identified the maximum number of genes enriched in biological processes such as RNA biosynthetic process, response to growth factors, nervous system development, neurogenesis, and anatomical structure morphogenesis. Differentially methylated genes (DMGs) such as myrip, mylk3, mafb, egr3, ndnf, meis2a, foxn3, bmp1a, plxna3, fgf6, sipa1l1, mcu, cnot8, trim55b, and myof were associated with growth and development. The selected DMGs were analyzed using real-time PCR, which showed altered mRNA expression levels. This work offers insights into the epigenetic mechanisms governing growth performance regulation in magur stocks. This work provides a valuable resource of epigenetic data that could be integrated into breeding programs to select high-performing individuals.

Pikeperch muscle tissues: a comparative study of structure, enzymes, genes, and proteins in wild and farmed fish

Pikeperch (Sander lucioperca) is a freshwater species and an internationally highly demanded fish in aquaculture. Despite intensive research efforts on this species, fundamental knowledge of skeletal muscle biology and structural characteristics is missing. Therefore, we conducted a comprehensive analysis of skeletal muscle parameters in adult pikeperch from two different origins, wild-caught specimens from a lake and those reared in a recirculating aquaculture system. The analyses comprised the biochemical characteristics (nucleic acid, protein content), enzyme activities (creatine kinase, lactate dehydrogenase, NADP-dependent isocitrate dehydrogenase), muscle-specific gene and protein expression (related to myofibre formation, regeneration and permanent growth, muscle structure), and muscle fibre structure. The findings reveal distinct differences between the skeletal muscle of wild and farmed pikeperch. Specifically, nucleic acid content, enzyme activity, and protein expression varied significantly. The higher enzyme activity observed in wild pikeperch suggests greater metabolically activity in their muscles. Conversely, farmed pikeperch indicated a potential for pronounced muscle growth. As the data on pikeperch skeletal muscle characteristics is sparse, the purpose of our study is to gain fundamental insights into the characteristics of adult pikeperch muscle. The presented data serve as a foundation for further research on percids' muscle biology and have the potential to contribute to advancements and adaptations in aquaculture practices.

Effects of Substituting Tenebrio molitor and Elodea nuttallii as Feed on Growth, Flesh Quality and Intestinal Microbiota of Red Swamp Crayfish (Procambarus clarkii)

This study aimed to evaluate the impact of substituting a portion of feed with Tenebrio molitor (TM) and Elodea nuttallii (EN) on crayfish culture. A total of 270 crayfish (5.1 ± 0.4 g) were fed three different diet combinations (A: 100% feed; B: 80% feed + 10% TM + 10% EN; C: 75% feed + 15% TM + 10% EN) for 12 weeks. The findings demonstrated that group C had an important beneficial impact on the growth performance of crayfish. This was evidenced by a rise in digestive enzyme activity (trypsin, lipase, and cellulase) in the intestinal and hepatopancreas, as well as an upregulation in the expression of growth-related genes (ghsr, igfbp7, mhc, mlc1, mef2, and pax7) in the muscle. Furthermore, the assessment of the flesh quality of crayfish muscle in group C was conducted. The findings indicated a significant increase (p < 0.05) in the energy value (moisture, crude protein, and crude lipid) within the muscle. The levels of delicious amino acids (Glu, Ala, Ser, Gly, and Tyr) and polyunsaturated fatty acids (ARA, DHA) were enhanced, resulting in an improved nutritional profile and flavor of the muscle while maintaining the Σn-3/Σn-6 ratio. The remodeling of the intestinal microbiota (abundance of Proteobacteria and ratio of Firmicutes/Bacteroidota bacteria) also revealed improved growth performance. Additional research is necessary to ascertain whether excessive use of TM or EN feed substitution can have negative effects on crayfish culture.

Skeletal muscle feature of different populations in large yellow croaker (Larimichthys crocea): from an epigenetic point of view

Fish skeletal muscle is composed of well-defined fiber types. In order to identify potential candidate genes affecting muscle growth and development under epigenetic regulation. Bisulfite sequencing was utilized to analyze and compare the muscle DNA methylation profiles of Larimichthys crocea inhabiting different environments. The results revealed that DNA methylation in L. crocea was predominantly CG methylation, with 2,396 differentially methylated regions (DMRs) identified through comparisons among different populations. The largest difference in methylation was observed between the ZhouShan and JinMen wild populations, suggesting that L. crocea may have undergone selection and domestication. Additionally, GO and KEGG enrichment analysis of differentially methylated genes (DMGs) revealed 626 enriched GO functional categories, including various muscle-related genes such as myh10, myf5, myf6, ndufv1, klhl31, map3k4, syn2b, sostdc1a, bag4, and hsp90ab. However, significant enrichment in KEGG pathways was observed only in the JinMen and XiangShan populations of L. crocea. Therefore, this study provides a theoretical foundation for a better understanding of the epigenetic regulation of skeletal muscle growth and development in L. crocea under different environmental conditions.

Single nucleotide polymorphisms in the MRFs gene family associated with growth in Nile tilapia

BACKGROUND

Muscle occupies most of the fish body, promoting the proliferation of fish muscle fibers can facilitate rapid growth and increase the body weight of fish. Some studiesSeveral previous suggest that Myogenic regulatory factors (MRFs) play an important role in the growth of fish.

OBJECTIVE

To investigate the association between the polymorphism of MRFs gene family and growth traits in Nile tilapia (Oreochromis niloticus), get more molecular markers for growth.

METHODS

Amplified the Nile tilapia MRFs family gene, including Myogenic determination 1 (Myod1), Myogenic determination 2 (Myod2), Myogenin (Myog), Myogenic factor 5 (Myf5), and Myogenic factor 6 (Myf6), single nucleotide polymorphism (SNP) were screened by Sanger sequencing.

RESULTS

A total of 16 SNP loci were screened, including six for Myf5, six for Myf6, one for Myog, one for Myod1 and two for Myod2. The growth traits were analyzed in relation to these 16 SNP loci, and the results indicated significant associations between all 16 SNP loci and the growth traits (P < 0.05). The linkage disequilibrium analysis revealed that D1 and D2 diplotypes of Myf5 gene, E1, E2, E3 and E4 of Myf6 gene, and F1 diplotype of Myod2 gene were significantly associated with superior growth traits.

CONCLUSION

There were 6, 6, 1, 1 and 2 growth-related molecular markers in Myf5, Myf6, Myog, Myod1 and Myod2 genes, respectively, which could be applied to the breeding of Nile tilapia.

Characterization of myosin heavy chain (MYH) genes and their differential expression in white and red muscles of Chinese perch, Siniperca chuatsi

Fish skeletal muscle is composed of two anatomically and functionally different fiber layers, white or fast and red or slow muscles. Myosin, the major structural protein of fish skeletal muscle, contains multiple myosin heavy chain (MYH) isoforms involved in the high plasticity of muscle in response to varying functional demands and/or environmental changes. In this study, we comparatively assayed the cellular and ultrastructural feature of white and red skeletal muscles. Then, a total of 28 class II myosin heavy chain genes were identified in by searching the Chinese perch genome database. Among them, 14 genes code for the fast-muscle-type myosin heavy chain, and 7 genes code for the slow-muscle-type myosin heavy chain. Further, the different isoform gene structures, function domains, phylogenetic relations, and muscle-fiber type-specific expression were characterized. This is the first systematic work on the molecular characterization of class II myosin heavy chain isoforms and the differential analysis of their expression in red and white muscle tissues in Chinese perch Siniperca chuatsi. Our work provided valuable information for a better understanding of myh genes and their molecular characteristics, and the correlations of multiple myosin isoforms with potential functions in response to varying functional demands and/or environmental changes.

Influence of DUX4 Expression in Facioscapulohumeral Muscular Dystrophy and Possible Treatments

Facioscapulohumeral muscular dystrophy (FSHD) represents the third most common form of muscular dystrophy and is characterized by muscle weakness and atrophy. FSHD is caused by the altered expression of the transcription factor double homeobox 4 (DUX4), which is involved in several significantly altered pathways required for myogenesis and muscle regeneration. While DUX4 is normally silenced in the majority of somatic tissues in healthy individuals, its epigenetic de-repression has been linked to FSHD, resulting in DUX4 aberrant expression and cytotoxicity in skeletal muscle cells. Understanding how DUX4 is regulated and functions could provide useful information not only to further understand FSHD pathogenesis, but also to develop therapeutic approaches for this disorder. Therefore, this review discusses the role of DUX4 in FSHD by examining the possible molecular mechanisms underlying the disease as well as novel pharmacological strategies targeting DUX4 aberrant expression.

Nutritional status affects Igf1 regulation of skeletal muscle myogenesis, myostatin, and myofibrillar protein degradation pathways in gopher rockfish (Sebastes carnatus)

Insulin-like growth factor-1 (Igf1) regulates skeletal muscle growth in fishes by increasing protein synthesis and promoting muscle hypertrophy. When fish experience periods of insufficient food intake, they undergo slower muscle growth or even muscle wasting, and those changes emerge in part from nutritional modulation of Igf1 signaling. Here, we examined how food deprivation (fasting) modulates Igf1 regulation of liver and skeletal muscle gene expression in gopher rockfish (Sebastes carnatus), a nearshore rockfish of importance for commercial and recreational fisheries in the northeastern Pacific Ocean, to understand how food limitation impacts Igf regulation of muscle growth pathways. Rockfish were either fed or fasted for 14 d, after which a subset of fish from each group was treated with recombinant Igf1 from sea bream (Sparus aurata). Fish that were fasted lost body mass and had lower body condition, reduced hepatosomatic index, and lower plasma Igf1 concentrations, as well as a decreased abundance of igf1 gene transcripts in the liver, increased hepatic mRNAs for Igf binding proteins igfbp1a, igfbp1b, and igfbp3a, and decreased mRNA abundances for igfbp2b and a putative Igf acid labile subunit (igfals) gene. In skeletal muscle, fasted fish showed a reduced abundance of intramuscular igf1 mRNAs but elevated gene transcripts encoding Igf1 receptors A (igf1ra) and B (igf1rb), which also showed downregulation by Igf1. Fasting increased skeletal muscle mRNAs for myogenin and myostatin1, as well as ubiquitin ligase F-box only protein 32 (fbxo32) and muscle RING-finger protein-1 (murf1) genes involved in muscle atrophy, while concurrently downregulating mRNAs for myoblast determination protein 2 (myod2), myostatin2, and myogenic factors 5 (myf5) and 6 (myf6 encoding Mrf4). Treatment with Igf1 downregulated muscle myostatin1 and fbxo32 under both feeding conditions, but showed feeding-dependent effects on murf1, myf5, and myf6/Mrf4 gene expression indicating that Igf1 effects on muscle growth and atrophy pathways is contingent on recent food consumption experience.

Comprehensive analysis of metabolomics on flesh quality of yellow catfish (Pelteobagrus fulvidraco) fed plant-based protein diet

Background

To investigate the mechanism of plant protein components on nutritional value, growth performance, flesh quality, flavor, and proliferation of myocytes of yellow catfish (Pelteobagrus fulvidraco).

Methods

A total of 540 yellow catfish were randomly allotted into six experimental groups with three replicates and fed six different diets for 8 weeks.

Results and Conclusions

The replacement of fish meal with cottonseed meal (CM), sesame meal (SEM), and corn gluten meal (CGM) in the diet significantly reduced growth performance, crude protein, and crude lipid, but the flesh texture (hardness and chewiness) was observably increased. Moreover, the flavor-related amino acid (glutamic acid, glycine, and proline) contents in the CM, SEM, and CGM groups of yellow catfish muscle were significantly increased compared with the fish meal group. The results of metabolomics showed that soybean meal (SBM), peanut meal (PM), CM, SEM, and CGM mainly regulated muscle protein biosynthesis by the variations in the content of vitamin B6, proline, glutamic acid, phenylalanine, and tyrosine in muscle, respectively. In addition, Pearson correlation analysis suggested that the increased glutamic acid content and the decreased tyrosine content were significantly correlated with the inhibition of myocyte proliferation genes. This study provides necessary insights into the mechanism of plant proteins on the dynamic changes of muscle protein, flesh quality, and myocyte proliferation in yellow catfish.

Muscle Nutritive Metabolism Changes after Dietary Fishmeal Replaced by Cottonseed Meal in Golden Pompano (Trachinotus ovatus)

Our previous study demonstrated that based on growth performance and feed utilization, cottonseed meal (CSM) could substitute 20% fishmeal (FM) without adverse effect on golden pompano (Trachinotus ovatus). Muscle deposition was also an important indicator to evaluate the efficiency of alternative protein sources. Therefore, the present study was conducted to explore the changes of physiobiochemical and nutrient metabolism in muscle after FM replaced by CSM. Four isonitrogenous and isolipidic experimental diets (42.5% crude protein, 14.0% crude lipid) were formulated to replace 0% (CSM0 diet), 20% (CSM20 diet), 40% (CSM40 diet), and 60% (CSM60 diet) of FM with CSM. Juvenile fish (24.8 ± 0.02 g) were fed each diet for 6 weeks. The results presented, which, compared with the CSM0 diet, CSM20 and CSM40 diets, had no effect on changing the muscle proximate composition and free essential amino acid (EAA) concentration. For glycolipid metabolism, the CSM20 diet did not change the mRNA expression of hexokinase (hk), glucose transport protein 4 (glut4), glucagon-like peptide 1 receptor (glp-1r), while over 20% replacement impaired glucose metabolism. However, CSM20 and CSM40 diets had no effect on altering lipid metabolism. Mechanistically, compared with the CSM0 diet, the CSM20 diet did not change muscle nutritive metabolism through keeping the activities of the nutrient sensing signaling pathways stable. Higher replacement would break this balance and lead to muscle nutritive metabolism disorders. Based on the results, CSM could substitute 20-40% FM without affecting the muscle nutritive deposition. All data supplemented the powerful support for our previous conclusion that CSM could successfully replace 20% FM based on growth performance.

Cellular Aquaculture: Prospects and Challenges

Aquaculture plays an important role as one of the fastest-growing food-producing sectors in global food and nutritional security. Demand for animal protein in the form of fish has been increasing tremendously. Aquaculture faces many challenges to produce quality fish for the burgeoning world population. Cellular aquaculture can provide an alternative, climate-resilient food production system to produce quality fish. Potential applications of fish muscle cell lines in cellular aquaculture have raised the importance of developing and characterizing these cell lines. In vitro models, such as the mouse C2C12 cell line, have been extremely useful for expanding knowledge about molecular mechanisms of muscle growth and differentiation in mammals. Such studies are in an infancy stage in teleost due to the unavailability of equivalent permanent muscle cell lines, except a few fish muscle cell lines that have not yet been used for cellular aquaculture. The Prospect of cell-based aquaculture relies on the development of appropriate muscle cells, optimization of cell conditions, and mass production of cells in bioreactors. Hence, it is required to develop and characterize fish muscle cell lines along with their cryopreservation in cell line repositories and production of ideal mass cells in suitably designed bioreactors to overcome current cellular aquaculture challenges.

Expression of ssa-miR-155 during ISAV infection in vitro: Putative role as a modulator of the immune response in Salmo salar

Multiple cellular components are involved in pathogen-host interaction during viral infection; in this context, the role of miRNAs have become highly relevant. We assessed the expression of selected miRNAs during an in vitro infection of a Salmo salar cell line with Infectious Salmon Anemia Virus (ISAV), the causative agent of a severe disease by the same name. Salmon orthologs for miRNAs that regulate antiviral responses were measured using RT-qPCR in an in vitro time-course assay. We observed a modulation of specific miRNAs expression, where ssa-miR-155-5p was differentially over-expressed. Using in silico analysis, we identified the putative mRNA targets for ssa-miR-155-5p, finding a high prevalence of hosts immune response-related genes; moreover, several mRNAs involved in the viral infective process were also identified as targets for this miRNA. Our results suggest a relevant role for miR-155-5p in Salmo salar during an ISAV infection as a regulator of the immune response to the virus.

Proteomic profile and morphological characteristics of skeletal muscle from the fast- and slow-growing yellow perch (Perca flavescens)

The objective of the present study was to compare skeletal muscle proteomic profiles, histochemical characteristics, and expression levels of myogenic regulatory factors (MRFs) between fast- versus slow-growing yellow perch Perca flavescens and identify the proteins/peptides that might play a crucial role in the muscle growth dynamic. Yellow perch were nursed in ponds for 6 weeks from larval stage and cultured in two meter diameter tanks thereafter. The fingerlings were graded to select the top 10% and bottom 10% fish which represented fast- and slow-growing groups (31 yellow perch per each group). Our statistical analyses showed 18 proteins that had different staining intensities between fast- and slow-growing yellow perch. From those proteins 10 showed higher expression in slow-growers, and 8 demonstrated higher expression in fast-growers. Fast-growing yellow perch with a greater body weight was influenced by both the muscle fiber hypertrophy and mosaic hyperplasia compared to slow-growing fish. These hyperplastic and hypertrophic growth in fast-grower were associated with not only metabolic enzymes, including creatine kinase, glycogen phosphorylase, and aldolase, but also myoD and myogenin as MRFs. Overall, the results of the present study contribute to the identification of different expression patterns of gene products in fast- and slow-growing fish associated with their muscle growth.

Characterization of MRF genes and their tissue distributions and analysis of the effects of starvation and refeeding on the expression of these genes in Acipenser dabryanus muscle

The purpose of the study was to clone the sequences of myogenic regulatory factors in Acipenser dabryanus and explore the changes in their expression during starvation and refeeding in A. dabryanus muscle. One hundred twenty fish (60.532 ± 0.284 g) were randomly assigned to four groups (fasted for 0, 3, 7 or 14 d and then refed for 14 d). Our predictions showed that the coding sequences of myod1, myf5, myog and myf6 in A. dabryanus encoded 275, 248, 248 and 243 amino acids, respectively, and the expression of the four genes was the highest in muscle. During fasting, the expression of myod1 in muscle was significantly decreased in the 14 d group. The expressions of myf5 and myf6 were increased significantly at first and then decreased with prolonged starvation time. The expression of myog in the 14 d group was significantly decreased compared with other groups (P < 0.05). During refeeding, the highest values of myod1 and myf6 expression were found in the 3 d group (P < 0.05).The expressions of myf5 and myog in 0 d and 3 d group were significantly higher than those in 7 d and 14 d group (P < 0.05). These results indicate that myogenic regulatory factors (MRFs) play important roles in muscle growth and development in A. dabryanus. The inhibition of long-term starvation (14 d) on the expression of myogenic regulatory factors is probably one of the reasons why it can not achieve full compensation for growth.