Regulatory role of N6-Methyladenosine on skeletal muscle development in Hu sheep.

N6-Methyladenosine (m6A) RNA modification plays an essential role in many biological processes. To investigate the regulatory role of m6A on the skeletal muscle development in Hu sheep, this study took newborn Hu sheep (b_B Group) and six-month-old Hu sheep (s_B Group) as the objects. MeRIP-seq and RNA-Seq analysis techniques were used to detect differentially methylated genes (DMGs) and differentially expressed genes (DEGs) in the longissimus dorsi muscle of Hu sheep at different months of age. Then, conjoint analysis was further employed to screen for key genes involved in skeletal muscle development that are modified by m6A and expressed by mRNA. According to the results of the MeRIP-seq analysis, there were 285 m6A differentially methylated peaks (DMPs) in total between b_B Group and s_B Group, with 192 significant upregulated peaks and 93 significant downregulated peaks. GO and KEGG analysis revealed that DMGs are mainly enriched in actin-binding, cellular transport, and metabolic pathways. According to the results of the RNA-seq analysis, there were 4,349 DEGs in total between b_B Group and s_B Group, with 2010 upregulated genes and 2,339 downregulated genes. DEGs are found to be mainly enriched in the regulation of actin cytoskeleton tissue, AMPK and FoxO signaling pathways, etc. The conjoint analysis demonstrated that 283 genes were both modified by m6A and expressed by mRNA. Among them, three genes relevant to muscle growth (RGMB, MAPK8IP3, and RSPO3) were selected as candidates for quantitative validation, and the results were in line with the sequencing results. The results mentioned above all suggest that m6A plays a certain role in the skeletal muscle development in Hu sheep.

SRSF2 is a key player in orchestrating the directional migration and differentiation of MyoD progenitors during skeletal muscle development.

SRSF2 plays a dual role, functioning both as a transcriptional regulator and a key player in alternative splicing. The absence of Srsf2 in MyoD + progenitors resulted in perinatal mortality in mice, accompanied by severe skeletal muscle defects. SRSF2 deficiency disrupts the directional migration of MyoD progenitors, causing them to disperse into both muscle and non-muscle regions. Single-cell RNA-sequencing analysis revealed significant alterations in Srsf2-deficient myoblasts, including a reduction in extracellular matrix components, diminished expression of genes involved in ameboid-type cell migration and cytoskeleton organization, mitosis irregularities, and premature differentiation. Notably, one of the targets regulated by Srsf2 is the serine/threonine kinase Aurka. Knockdown of Aurka led to reduced cell proliferation, disrupted cytoskeleton, and impaired differentiation, reflecting the effects seen with Srsf2 knockdown. Crucially, the introduction of exogenous Aurka in Srsf2-knockdown cells markedly alleviated the differentiation defects caused by Srsf2 knockdown. Furthermore, our research unveiled the role of Srsf2 in controlling alternative splicing within genes associated with human skeletal muscle diseases, such as BIN1, DMPK, FHL1, and LDB3. Specifically, the precise knockdown of the Bin1 exon17-containing variant, which is excluded following Srsf2 depletion, profoundly disrupted C2C12 cell differentiation. In summary, our study offers valuable insights into the role of SRSF2 in governing MyoD progenitors to specific muscle regions, thereby controlling their differentiation through the regulation of targeted genes and alternative splicing during skeletal muscle development.

The maternal lifestyle in pregnancy: Implications for foetal skeletal muscle development.

The world is facing a global nutrition crisis, as evidenced by the rising incidence of metabolic disorders such as obesity, insulin resistance and chronic inflammation. Skeletal muscle is the largest tissue in humans and plays an important role in movement and host metabolism. Muscle fibre formation occurs mainly during the embryonic stage. Therefore, maternal lifestyle, especially nutrition and exercise during pregnancy, has a critical influence on foetal skeletal muscle development and the subsequent metabolic health of the offspring. In this review, the influence of maternal obesity, malnutrition and micronutrient intake on foetal skeletal muscle development is systematically summarized. We also aim to describe how maternal exercise shapes foetal muscle development and metabolic health in the offspring. The role of maternal gut microbiota and its metabolites on foetal muscle development is further discussed, although this field is still in its 'infancy'. This review will provide new insights to reduce the global crisis of metabolic disorders and highlight current gaps to promote further research.

Comprehensive analysis of single-nucleotide variants and alternative polyadenylation between inbred and outbred pigs.

Inbreeding can lead to the accumulation of homozygous single nucleotide polymorphisms (SNPs) in the genome, which can significantly affect gene expression and phenotype. In this study, we examined the impact of homozygous SNPs resulting from inbreeding on alternative polyadenylation (APA) site selection and the underlying genetic mechanisms using inbred Luchuan pigs. Genome resequencing revealed that inbreeding results in a high accumulation of homozygous SNPs within the pig genome. 3' mRNA-seq on leg muscle, submandibular lymph node, and liver tissues was performed to identify differences in APA events between inbred and outbred Luchuan pigs. We revealed different tissue-specific APA usage caused by inbreeding, which were associated with different biological processes. Furthermore, we explored the role of polyadenylation signal (PAS) SNPs in APA regulation under inbreeding and identified key genes such as PUM1, SCARF1, RIPOR2, C1D, and LRRK2 that are involved in biological processes regulation. This study provides resources and sheds light on the impact of genomic homozygosity on APA regulation, offering insights into genetic characteristics and biological processes associated with inbreeding.

Give it a rest: a systematic review with Bayesian meta-analysis on the effect of inter-set rest interval duration on muscle hypertrophy.

We systematically searched the literature for studies with a randomized design that compared different inter-set rest interval durations for estimates of pre-/post-study changes in lean/muscle mass in healthy adults while controlling all other training variables. Bayesian meta-analyses on non-controlled effect sizes using hierarchical models of all 19 measurements (thigh: 10; arm: 6; whole body: 3) from 9 studies meeting inclusion criteria analyses showed substantial overlap of standardized mean differences across the different inter-set rest periods [binary: short: 0.48 (95%CrI: 0.19-0.81), longer: 0.56 (95%CrI: 0.24-0.86); Four categories: short: 0.47 (95%CrI: 0.19-0.80), intermediate: 0.65 (95%CrI: 0.18-1.1), long: 0.55 (95%CrI: 0.15-0.90), very long: 0.50 (95%CrI: 0.14-0.89)], with substantial heterogeneity in results. Univariate and multivariate pairwise meta-analyses of controlled binary (short vs. longer) effect sizes showed similar results for the arm and thigh with central estimates tending to favor longer rest periods [arm: 0.13 (95%CrI: -0.27 to 0.51); thigh: 0.17 (95%CrI: -0.13 to 0.43)]. In contrast, central estimates closer to zero but marginally favoring shorter rest periods were estimated for the whole body [whole body: -0.08 (95%CrI: -0.45 to 0.29)]. Subanalysis of set end-point data indicated that training to failure or stopping short of failure did not meaningfully influence the interaction between rest interval duration and muscle hypertrophy. In conclusion, results suggest a small hypertrophic benefit to employing inter-set rest interval durations >60 s, perhaps mediated by reductions in volume load. However, our analysis did not detect appreciable differences in hypertrophy when resting >90 s between sets, consistent with evidence that detrimental effects on volume load tend to plateau beyond this time-frame. Systematic Review Registration: OSF, https://doi.org/10.17605/OSF.IO/YWEVC.

Transcriptomic Analysis across Crayfish (Cherax quadricarinatus) Claw Regeneration Reveals Potential Stem Cell Sources for Cultivated Crustacean Meat.

In the face of rising global demand and unsustainable production methods, cultivated crustacean meat (CCM) is proposed as an alternative means to produce delicious lobster, shrimp, and crab products. Cultivated meat requires starting stem cells that may vary in terms of potency and the propensity to proliferate or differentiate into myogenic (muscle-related) tissues. Recognizing that regenerating limbs are a non-lethal source of tissue and may harbor relevant stem cells, we selected those of the crayfish Cherax quadricarinatus as our model. To investigate stem cell activity, we conducted RNA-Seq analysis across six stages of claw regeneration (four pre-molt and two post-molt stages), along with histology and real-time quantitative PCR (qPCR). Our results showed that while genes related to energy production, muscle hypertrophy, and exoskeletal cuticle synthesis dominated the post-molt stages, growth factor receptors (FGFR, EGFR, TGFR, and BMPR) and those related to stem cell proliferation and potency (Cyclins, CDKs, Wnts, C-Myc, Klf4, Sox2, PCNA, and p53) were upregulated before the molt. Pre-molt upregulation in several genes occurred in two growth peaks; Stages 2 and 4. We therefore propose that pre-molt limb regeneration tissues, particularly those in the larger Stage 4, present a prolific and non-lethal source of stem cells for CCM development.

Changes of mRNA, miRNA and lncRNA expression contributing to skeletal muscle differences between fetus and adult Mongolian horses.

The growth and development of myofibers, as the fundamental units comprising muscle tissue, and their composition type are indeed among the most crucial factors influencing skeletal muscle types. Muscle fiber adaptation is closely associated with alterations in physiological conditions. Muscle fiber types undergo dynamic changes in fetus and adult horses. Our aim is to investigate the mechanisms influencing the differences in muscle fiber types between fetal and adult stages of Mongolian horses. The study investigated the distribution of muscle fiber types within longissimus dorsi muscle of fetus and adult Mongolian horses. A total of 652 differentially expressed genes (DEGs), 476 Differentially expressed lncRNAs (DELs), and 174 Differentially expressed miRNAs (DEMIRs) were identified using deep RNA-seq analysis. The results of functional analysis reveal the transformations in muscle fiber type from the fetal to adult stage in Mongolian horses. The up-regulated DEGs were implicated in the development and differentiation of muscle fibers, while down-regulated DEGs were associated with muscle fiber contraction, transformation, and metabolism. Additionally, connections between non-coding RNA and mRNA landscapes were identified based on their functional alterations, some non-coding RNA target genes may be associated with immunity. These data have broadened our understanding of the specific roles and interrelationships among regulatory molecules involved in Mongolian horse development, this provides new perspectives for selecting and breeding superior individuals and for disease prevention.

N-acetylcysteine stimulates the proliferation and differentiation in heat-stressed skeletal muscle cells.

N-acetylcysteine (NAC) is known for its beneficial effects on health due to its antioxidant and antiapoptotic properties. This study explored the protective effects of NAC against oxidative stress in heat-stressed (HS) skeletal muscle cells and its role in promoting muscle development. NAC reduced the heat shock response by decreasing the expression of heat shock protein 70 (HSP70) in HS-induced muscle cells during proliferation and differentiation. NAC also mitigated HS-induced oxidative stress via increasing the antioxidant enzyme levels and reducing oxidant enzyme levels. Treatment with NAC at 2 mM increased cell viability from 43.68% ± 5.14%-66.69% ± 14.43% and decreased the apoptosis rate from 7.89% ± 0.53%-5.17% ± 0.11% in skeletal muscle cells. Additionally, NAC promoted the proliferation and differentiation of HS-induced skeletal muscle cells by upregulating the expression of PAX7, MYF5, MRF4 and MYHC. These findings suggest that NAC alleviates HS-induced oxidative damage in skeletal muscle cells and support muscle development.

Tumor necrosis factor α deficiency promotes myogenesis and muscle regeneration.

Tumor necrosis factor α (TNFα) exhibits diverse biological functions; however, its regulatory roles in myogenesis are not fully understood. In the present study, we explored the function of TNFα in myoblast proliferation, differentiation, migration, and myotube fusion in primary myoblasts and C2C12 cells. To this end, we constructed TNFα muscle-conditional knockout ( TNFα-CKO) mice and compared them with flox mice to assess the effects of TNFα knockout on skeletal muscles. Results indicated that TNFα-CKO mice displayed phenotypes such as accelerated muscle development, enhanced regenerative capacity, and improved exercise endurance compared to flox mice, with no significant differences observed in major visceral organs or skeletal structure. Using label-free proteomic analysis, we found that TNFα-CKO altered the distribution of several muscle development-related proteins, such as Hira, Casz1, Casp7, Arhgap10, Gas1, Diaph1, Map3k20, Cfl2, and Igf2, in the nucleus and cytoplasm. Gene set enrichment analysis (GSEA) further revealed that TNFα deficiency resulted in positive enrichment in oxidative phosphorylation and MyoD targets and negative enrichment in JAK-STAT signaling. These findings suggest that TNFα-CKO positively regulates muscle growth and development, possibly via these newly identified targets and pathways.

Retinoic acid signalling regulates branchiomeric neck muscle development at the head/trunk interface.

Skeletal muscles of the head and trunk originate in distinct lineages with divergent regulatory programmes converging on activation of myogenic determination factors. Branchiomeric head and neck muscles share a common origin with cardiac progenitor cells in cardiopharyngeal mesoderm (CPM). The retinoic acid (RA) signalling pathway is required during a defined early time window for normal deployment of cells from posterior CPM to the heart. Here, we show that blocking RA signalling in the early mouse embryo also results in selective loss of the trapezius neck muscle, without affecting other skeletal muscles. RA signalling is required for robust expression of myogenic determination factors in posterior CPM and subsequent expansion of the trapezius primordium. Lineage-specific activation of a dominant-negative RA receptor reveals that trapezius development is not regulated by direct RA signalling to myogenic progenitor cells in CPM, or through neural crest cells, but indirectly through the somitic lineage, closely apposed with posterior CPM in the early embryo. These findings suggest that trapezius development is dependent on precise spatiotemporal interactions between cranial and somitic mesoderm at the head/trunk interface.

Aflatoxin B1 decreased flesh flavor and inhibited muscle development in grass carp (Ctenopharyngodon idella).

In nature, aflatoxins, especially aflatoxin B1 (AFB1), are the common mycotoxins, which cause serious health problems for humans and animals. This paper aimed to study the effects of AFB1 on flesh flavor and muscle development of grass carp (Ctenopharyngodon idella) and its mechanism. There were 1440 individual fish in total, with 6 treatments and each treatment replicated 3 times. The 6 treatments were fed a control diet with different doses of AFB1 (0.04, 29.48, 58.66, 85.94, 110.43 and 146.92 µg/kg diet) for 60 d. AFB1 increased myofiber diameter, as well as decreased myofiber density of grass carp muscle (P < 0.05). The contents of free amino acid decreased gradually (P < 0.05) as dietary AFB1 increased in the muscle of grass carp. The levels of reactive oxygen species, malonaldehyde and protein carbonyl (PC) were increased (P < 0.05) with the dietary AFB1 increased. The levels of antioxidant enzyme (glutathione peroxidase, glutathione, glutathione reductase, total antioxidant capacity, anti-superoxide anion, and anti-hydroxyl radical) were decreased (P < 0.05) with the dietary AFB1 increased. In addition, dietary AFB1 decreased the content of collagen, and downregulated the mRNA and protein levels of transforming growth factor-ß (TGF-ß)/Smads signaling pathway in grass carp muscle (P < 0.05). The mRNA and protein levels of myogenic regulatory factors were downregulated in grass carp muscle (P < 0.05). Furthermore, the activities of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) were increased (P < 0.05), and the protein levels of phosphorylate-38 mitogen-activated protein kinase (p-p38MAPK), phosphorylate-c-Jun N-terminal kinase, urokinase-type plasminogen activator (uPA), MMP-2 and MMP-9 were upregulated (P < 0.05), but collagen Ⅰ, laminin ß1 and fibronectin were downregulated (P < 0.05) with the dietary AFB1 increased in the muscle of grass carp. Based on the results of this study, we can draw the following conclusion: dietary AFB1 might damage flesh flavor and inhibit the muscle development through MAPK/uPA/MMP/extracellular matrix (ECM) signaling pathway in grass carp. Moreover, the recommended safe limit of AFB1 in feed is no more than 26.77 µg/kg diet according to the PC levels in grass carp muscle.

Timing of feeding a protein supplement on nitrogen balance and plasma amino acids during exercise recovery in horses.

Eight geldings weighing 544 ± 16 kg were used to evaluate feeding a postexercise protein meal on plasma amino acids during recovery. Horses were fed sweet feed, corn, grass hay and equal amounts of a protein pellet (32% CP) with meals (MP group) or postexercise (EP group). Horses exercised 1-2 h/day, 5 days/week, for 12 weeks. A pre and poststudy 4 days total urine and feces collection was conducted. Urine and fecal samples were analyzed for nitrogen (N) to calculate N balance. Blood samples were drawn immediately after and at 1 and 3 h postexercise at the start and end of the study for plasma amino acid concentrations. Absorbed N and N retention were greater for the MP group compared to the EP group (p = 0.038, 0.033 respectively). An interaction revealed an increase in fecal N (p = 0.01) and decreased N digestibility for the MP group compared to the EP group at the end of the study. Plasma concentrations for 8 out of 14 amino acids were less for the EP group immediately after exercise compared to the MP group (p < 0.02). Plasma concentrations of lysine and arginine were greater for the EP group compared to the MP group at 1 and 3 h after exercise (p < 0.05 and 0.04 respectively). Changes were different for 8 out of the 14 amino acids immediately post exercise, 7 out of 14 amino acids at 1 h postexercise and 10 out of 14 amino acids at 3 h postexercise with positive changes for the EP group and negative changes for the MP group. The EP group had improved supply of plasma amino acids in the recovery period that sustained for 3 h postexercise and are indicative of better amino acid supply supporting muscle development.

Transcriptomic and epigenomic landscapes of muscle growth during the postnatal period of broilers.

BACKGROUND: Broilers stand out as one of the fastest-growing livestock globally, making a substantial contribution to animal meat production. However, the molecular and epigenetic mechanisms underlying the rapid growth and development of broiler chickens are still unclear. This study aims to explore muscle development patterns and regulatory networks during the postnatal rapid growth phase of fast-growing broilers. We measured the growth performance of Cornish (CC) and White Plymouth Rock (RR) over a 42-d period. Pectoral muscle samples from both CC and RR were randomly collected at day 21 after hatching (D21) and D42 for RNA-seq and ATAC-seq library construction. RESULTS: The consistent increase in body weight and pectoral muscle weight across both breeds was observed as they matured, with CC outpacing RR in terms of weight at each stage of development. Differential expression analysis identified 398 and 1,129 genes in the two dimensions of breeds and ages, respectively. A total of 75,149 ATAC-seq peaks were annotated in promoter, exon, intron and intergenic regions, with a higher number of peaks in the promoter and intronic regions. The age-biased genes and breed-biased genes of RNA-seq were combined with the ATAC-seq data for subsequent analysis. The results spotlighted the upregulation of ACTC1 and FDPS at D21, which were primarily associated with muscle structure development by gene cluster enrichment. Additionally, a noteworthy upregulation of MUSTN1, FOS and TGFB3 was spotted in broiler chickens at D42, which were involved in cell differentiation and muscle regeneration after injury, suggesting a regulatory role of muscle growth and repair. CONCLUSIONS: This work provided a regulatory network of postnatal broiler chickens and revealed ACTC1 and MUSTN1 as the key responsible for muscle development and regeneration. Our findings highlight that rapid growth in broiler chickens triggers ongoing muscle damage and subsequent regeneration. These findings provide a foundation for future research to investigate the functional aspects of muscle development.

Effects of thyroid hormone on monochromatic light combinations mediate skeletal muscle fiber pattern in broilers.

It has been shown that monochromatic green light and blue light promote skeletal muscle development in early (P0-P26) and later growth stages (P27-P42), respectively. This study further investigated the effects of monochromatic light combinations on myogenesis and myofiber types transformation in broilers. Here, a total of 252 chicks were exposed to monochromatic light [red (R), green (G), blue (B), or white light (W)], and monochromatic light combination [green and blue light combination (GB), blue and green light combination (BG), red and blue combination (RB)] until P42. Compared with other groups, GB significantly increased body weight, and muscle organ index, both proportions of larger-size myofibers and oxidative myofibers in the pectoralis major (PM) and gastrocnemius muscle (GAS). Meanwhile, GB up-regulated the abundance of oxidative genes MYH7B and MYH1B, transcription factors PAX7 and Myf5, antioxidant proteins Nrf2, HO-1, and GPX4, and the activities of antioxidant enzymes CAT, GPx, and T-AOC, but down-regulated the abundance of glycolytic related genes MYH 1A, MyoD, MyoG, Mstn, Keap1, TNFa, and MDA levels. Consistent with the change of myofiber pattern, GB significantly reduced serum thyroid hormone (TH) levels, up-regulated skeletal muscle deiodinase DIO3 expression and down-regulated deiodinase DIO2 expression, which may directly lead to the reduction of intramuscular TH levels to affect myofiber types transformation. In contrast, the proportion of fast glycolytic muscle fibers increased in the RR with increasing TH levels. After thyroidectomy, the above parameters were inversed and resulted in no significant difference of each color light treatment group. These data suggested that GB significantly increased the proportion of oxidative muscle fibers and antioxidant capacity in skeletal muscle of broilers, which was regulated by TH-DIO2/DIO3 signaling pathway.

Research progress on regulating factors of muscle fiber heterogeneity in poultry: a review.

Control of meat quality traits is an important goal of any farm animal production, including poultry. A better understanding of the biochemical properties of muscle fiber properties that drive muscle development and ultimately meat quality constitutes one of the major challenging topics in animal production and meat science. In this paper, the existing classification methods of skeletal muscle fibers in poultry were reviewed and the relationship between contractile and metabolic characteristics of muscle fibers and poultry meat quality was described. Finally, a comprehensive review of multiple potential factors affecting muscle fiber distribution and conversion is presented, including breed, sex, hormones, growth performance, diet, muscle position, exercise, and ambient temperature. We emphasize that knowledge of muscle fiber typing is essential to better understand how to control muscle characteristics throughout the life cycle of animals to better manage the final quality of poultry meat.

Transcriptomic and epigenomic insights into pectoral muscle fiber formation at the late embryonic development in pure chicken lines.

Long-term intensive genetic selection has led to significant differences between broiler and layer chickens, which are evident during the embryonic period. Despite this, there is a paucity of research on the genetic regulation of the initial formation of muscle fiber morphology in chick embryos. Embryonic d 17 (E17) is the key time point for myoblast fusion completion and muscle fiber morphology formation in chickens. This study aimed to explore the genetic regulatory mechanisms underlying the early muscle fiber morphology establishment in broiler chickens of Cornish (CC) and White Plymouth Rock (RR) and layer chickens of White Leghorn (WW) at E17 using the transcriptomic and chromatin accessibility sequencing of pectoral major muscles. The results showed that broiler chickens exhibited significant higher embryo weight and pectoral major muscle weight at E17 compared to layer chickens (P = 0.000). A total of 1,278, 1,248, and 892 differentially expressed genes (DEGs) of RNA-seq data were identified between CC vs. WW, RR vs. WW, and CC vs. RR, separately. All DEGs were combined for cluster analysis and they were divided into 6 clusters, including cluster 1 with higher expression in broilers and cluster 6 with higher expression in layers. DEGs in cluster 1 were enriched in terms related to macrophage activation (P = 0.002) and defense response to bacteria (P = 0.002), while DEGs in cluster 6 showed enrichment in protein-DNA complex (P = 0.003) and monooxygenase activity (P = 0.000). ATAC-seq data analysis identified a total of 38,603 peaks, with 13,051 peaks for CC, 18,780 peaks for RR, and 6,772 peaks for WW. Integrative analysis of transcriptomic and chromatin accessibility data revealed GOLM1, ISLR2, and TOPAZ1 were commonly upregulated genes in CC and RR. Furthermore, screening of all upregulated DEGs in cluster 1 from CC and RR identified GOLM1, ISLR2, and HNMT genes associated with neuroimmune functions and MYOM3 linked to muscle morphology development, showing significantly elevated expression in broiler chickens compared to layer chickens. These findings suggest active neural system connectivity during the initial formation of muscle fiber morphology in embryonic period, highlighting the early interaction between muscle fiber formation morphology and the nervous system. This study provides novel insights into late chick embryo development and lays a deeper foundation for further research.

Genome-wide characteristics and potential functions of circular RNAs from the embryo muscle development in Chengkou mountain chicken.

The Chengkou mountain chicken, a native Chinese poultry breed, holds significant importance in the country's poultry sector due to its delectable meat and robust stress tolerance. Muscle growth and development are pivotal characteristics in poultry breeding, with muscle fiber development during the embryonic period crucial for determining inherent muscle growth potential. Extensive evidence indicates that non-coding RNAs (ncRNAs) play a regulatory role in muscle growth and development. Among ncRNAs, circular RNAs (circRNAs), characterized by a closed-loop structure, have been shown to modulate biological processes through the regulation of microRNAs (miRNAs). This study seeks to identify and characterize the spatiotemporal-specific expression of circRNAs during embryonic muscle development in Chengkou mountain chicken, and to construct the potential regulatory network of circRNAs-miRNA-mRNAs. The muscle fibers of HE-stained sections became more distinct, and their boundaries were more defined over time. Subsequent RNA sequencing of 12 samples from four periods generated 9,904 novel circRNAs, including 917 differentially expressed circRNAs. The weighted gene co-expression network analysis (WGCNA)-identified circRNA source genes significantly enriched pathways related to cell fraction, cell growth, and muscle fiber growth regulation. Furthermore, a competitive endogenous RNA (ceRNA) network constructed using combined data of present and previous differentially expressed circRNAs, miRNA, and mRNA revealed that several circRNA transcripts regulate MYH1D, MYH1B, CAPZA1, and PERM1 proteins. These findings provide insight into the potential pathways and mechanisms through which circRNAs regulate embryonic muscle development in poultry, a theoretical support for trait improvement in domestic chickens.

Full-Length Transcriptome Analysis of Skeletal Muscle of Jiangquan Black Pig at Different Developmental Stages.

Skeletal muscle grows in response to a combination of genetic and environmental factors, and its growth and development influence the quality of pork. Elucidating the molecular mechanisms regulating the growth and development of skeletal muscle is of great significance to both animal husbandry and farm management. The Jiangquan black pig is an excellent pig breed based on the original Yimeng black pig, importing the genes of the Duroc pig for meat traits, and cultivated through years of scientific selection and breeding. In this study, full-length transcriptome sequencing was performed on three growth stages of Jiangquan black pigs, aiming to study the developmental changes in Jiangquan black pigs at different developmental stages at the molecular level and to screen the key genes affecting the growth of skeletal muscle in Jiangquan black pigs. We performed an enrichment analysis of genes showing differential expression and constructed a protein-protein interaction network with the aim of identifying core genes involved in the development of Jiangquan black pigs. Notably, genes such as TNNI2, TMOD4, PLDIM3, MYOZ1, and MYH1 may be potential regulators of muscle development in Jiangquan black pigs. Our results contribute to the understanding of the molecular mechanisms of skeletal muscle development in this pig breed, which will facilitate molecular breeding efforts and the development of pig breeds to meet the needs of the livestock industry.

Transcriptome analysis revealed differences in gene expression in sheep muscle tissue at different developmental stages.

BACKGROUND: The analysis of differentially expressed genes in muscle tissues of sheep at different ages is helpful to analyze the gene expression trends during muscle development. In this study, the longissimus dorsi muscle of pure breeding Hu sheep (H), Suffolk sheep and Hu sheep hybrid F1 generation (SH) and East Friesian and Hu sheep hybrid sheep (EHH) three strains of sheep born 2 days (B2) and 8 months (M8) was used as the research object, and transcriptome sequencing technology was used to identify the differentially expressed genes of sheep longissimus dorsi muscle in these two stages. Subsequently, GO and KEGG enrichment analysis were performed on the differential genes. Nine differentially expressed genes were randomly selected and their expression levels were verified by qRT-PCR. RESULTS: The results showed that 842, 1301 and 1137 differentially expressed genes were identified in H group, SH group and EHH group, respectively. Among them, 191 differential genes were enriched in these three strains, including pre-folding protein subunit 6 (PFDN6), DnaJ heat shock protein family member A4 (DNAJA4), myosin heavy chain 8 (MYH8) and so on. GO and KEGG enrichment analysis was performed on 191 differentially expressed genes shared by the three strains to determine common biological pathways. The results showed that the differentially expressed genes were significantly enriched in ribosomes, unfolded protein binding, FoxO signaling pathway, glycolysis / glycogen generation and glutathione signaling pathway that regulate muscle protein synthesis and energy metabolism. The results of qRT-PCR were consistent with transcriptome sequencing, which proved that the sequencing results were reliable. CONCLUSIONS: Overall, this study revealed the important genes and signaling pathways related to sheep skeletal muscle development, and the result laid a foundation for further understanding the mechanism of sheep skeletal muscle development.

Muscle Transcriptome Analysis of Mink at Different Growth Stages Using RNA-Seq.

Mink is a kind of small and precious fur animal resource. In this study, we employed transcriptomics technology to analyze the gene expression profile of mink pectoral muscle tissue, thereby elucidating the regulatory mechanisms underlying mink growth and development. Consequently, a total of 25,954 gene expression profiles were acquired throughout the growth and development stages of mink at 45, 90, and 120 days. Among these profiles, 2607 genes exhibited significant differential expression (|log2(fold change)| ≥ 2 and p_adj < 0.05). GO and KEGG enrichment analyses revealed that the differentially expressed genes were primarily associated with the mitotic cell cycle process, response to growth factors, muscle organ development, and insulin resistance. Furthermore, GSEA enrichment analysis demonstrated a significant enrichment of differentially expressed genes in the p53 signaling pathway at 45 days of age. Subsequent analysis revealed that genes associated with embryonic development (e.g., PEG10, IGF2, NRK), cell cycle regulation (e.g., CDK6, CDC6, CDC27, CCNA2), and the FGF family (e.g., FGF2, FGF6, FGFR2) were all found to be upregulated at 45 days of age in mink, which suggested a potential role for these genes in governing early growth and developmental processes. Conversely, genes associated with skeletal muscle development (PRVA, TNNI1, TNNI2, MYL3, MUSTN1), a negative regulator of the cell cycle gene (CDKN2C), and IGFBP6 were found to be up-regulated at 90 days of age, suggesting their potential involvement in the rapid growth of mink. In summary, our experimental data provide robust support for elucidating the regulatory mechanisms underlying the growth and development of mink.