MyoD expression profile and developmental differences of leg and breast muscle in Peking duck (Anas platyrhynchos Domestica) during embryonic to neonatal stages

Association of variants and expression levels of MYOD1 gene with carcass and muscle characteristic traits in domestic pigeons

This study was to investigate the correlations of myogenic differentiation 1 (MYOD1) gene polymorphisms with carcass traits and its expression with breast muscle development in pigeons. Four SNPs were found in the pigeon MYOD1 gene. Correlation analysis showed that individuals with AA genotype at both SNPs g.2967A > G (p < .01) and g.3044G > A (p < .05) have significantly higher live weight (LW), carcass weight (CW), semi-eviscerated weight (SEW), eviscerated weight (EW) and breast muscle weight (BMW). Moreover, the two SNPs also had the same significant effects on MYOD1 mRNA expression levels in breast muscle of pigeons, ie, the AA genotype showed higher MYOD1 mRNA expression levels. The diameter and cross-section area of muscle fibers continuously increased from 0w to 4w (p < .05), accompanied with the increasing expression of MYOD1 gene, while the density decreased (p < .05) dramatically from 0w to 1w and continuously fell over in the next few weeks (p > .05). What's more, the expression level of MYOD1 gene was positively correlated with a diameter (r = 0.937, p < .05) and cross-sectional area (r = 0.956, p < .01) of myofiber, and negatively correlated with density (r = -0.769, p < .01). The results showed that individuals with AA genotype at both SNPs g.2967A > G and g.3044G > A have showed higher carcass traits (LW, CW, SEW, EW, and BMW) and higher MYOD1 mRNA expression level in breast muscle than AB and BB genotypes. Moreover, the expression level of MYOD1 gene was closely correlated with muscle characteristic traits, indicating variants of MYOD1 gene was closely related to muscle development and could be a potential candidate gene in marker-assisted selection of pigeons.

Developmental Characteristics of Skeletal Muscle during the Embryonic Stage in Chinese Yellow Quail (Coturnix japonica)

The quail is an important research model, and the demand for quail meat has been increasing in recent years; therefore, it is worthwhile investigating the development of embryonic skeletal muscle and the expression patterns of regulatory genes. In this study, the expression of MyoD and Pax7 in the breast muscle (m. pectoralis major) and leg muscle (m. biceps femoris) of quail embryos on days 10 through 17 were determined using qRT-PCR. Paraffin sections of embryonic muscle were analyzed to characterize changes over time. Results showed that MyoD and Pax7 were expressed in both breast and leg muscles and played a significant role in embryonic muscle development. Compared to breast muscle, leg muscle grew faster and had greater weight and myofiber size. The findings suggested that embryonic day 12 (E12) may be a key point for muscle development. Correlation analysis showed that MyoD expression was significantly negatively correlated with muscle and embryo weight, whereas Pax7 gene expression had no significant correlation with these characteristics. These fundamental results provide a theoretical basis for understanding the characteristics and transition points of skeletal muscle development in quail embryos and an important reference for farmers raising quail from eggs.

Sox6 Differentially Regulates Inherited Myogenic Abilities and Muscle Fiber Types of Satellite Cells Derived from Fast- and Slow-Type Muscles

Adult skeletal muscle is primarily divided into fast and slow-type muscles, which have distinct capacities for regeneration, metabolism and contractibility. Satellite cells plays an important role in adult skeletal muscle. However, the underlying mechanisms of satellite cell myogenesis are poorly understood. We previously found that Sox6 was highly expressed in adult fast-type muscle. Therefore, we aimed to validate the satellite cell myogenesis from different muscle fiber types and investigate the regulation of Sox6 on satellite cell myogenesis. First, we isolated satellite cells from fast- and slow-type muscles individually. We found that satellite cells derived from different muscle fiber types generated myotubes similar to their origin types. Further, we observed that cells derived from fast muscles had a higher efficiency to proliferate but lower potential to self-renew compared to the cells derived from slow muscles. Then we demonstrated that Sox6 facilitated the development of satellite cells-derived myotubes toward their inherent muscle fiber types. We revealed that higher expression of Nfix during the differentiation of fast-type muscle-derived myogenic cells inhibited the transcription of slow-type isoforms (MyH7B, Tnnc1) by binding to Sox6. On the other hand, Sox6 activated Mef2C to promote the slow fiber formation in slow-type muscle-derived myogenic cells with Nfix low expression, showing a different effect of Sox6 on the regulation of satellite cell development. Our findings demonstrated that satellite cells, the myogenic progenitor cells, tend to develop towards the fiber type similar to where they originated. The expression of Sox6 and Nfix partially explain the developmental differences of myogenic cells derived from fast- and slow-type muscles.

Development of breast muscle parameters, glycogen reserves, and myogenic gene expression in goslings during pre- and post-hatching periods

This study aimed to better understand the development patterns of breast muscle and glycogen reserves in goslings during pre- and post-hatching periods. The timepoints for sampling were embryonic days 23 and 27 of hatching and days 1, 4, and 7 post hatching. We found that the body weight of goslings increased with age. The small intestine developed with age and remained reasonably constant on day 4 post hatching. The breast muscle development decreased with age and stayed relatively stable on day 1 post hatching. The diameter of myofiber increased prior to hatching and then decreased while hatching. The development patterns of breast muscle glycogen reserves were similar to the diameter of myofiber. In contrast, the contents of liver glycogen began to decrease before hatching and then increased rapidly after hatching. Moreover, the expression of Myf-5 increased with age. The expression of MSTN was maintained at high levels prior to hatching, dropped immediately after hatching, and then gradually increased with age. Additionally, we also observed that the glycogen content in the breast muscle was positively correlated with the diameter of the myofiber. The liver glycogen content was positively correlated to the relative weight of the breast muscle, the diameter of the myofiber, and the breast muscle glycogen content. The development pattern of the myofiber was synchronized with the change in the MSTN/Myf-5 ratio. This study provided a profile to understand the development patterns of breast muscle, glycogen reserves, and myogenic gene expression in goslings, which was beneficial to understanding the characteristics of energy reserves during the early life of goslings.

circPTPN4 regulates myogenesis via the miR-499-3p/NAMPT axis

Background

Circular RNAs (circRNAs) are a novel class of endogenous ncRNA, which widely exist in the transcriptomes of different species and tissues. Recent studies indicate important roles for circRNAs in the regulation of gene expression by acting as competing endogenous RNAs (ceRNAs). However, the specific role of circRNAs in myogenesis is still poorly understood. In this study, we attempted to systematically identify the circRNAs involved in myogenesis and analyze the biological functions of circRNAs in chicken skeletal muscle development.

Results

In total, 532 circRNAs were identified as being differentially expressed between pectoralis major (PEM) and soleus (SOL) in 7-week-old Xinghua chicken. Among them, a novel circRNA (novel_circ_002621), generated by PTPN4 gene, was named circPTPN4 and identified. circPTPN4 is highly expressed in skeletal muscle, and its expression level is upregulated during myoblast differentiation. circPTPN4 facilitates the proliferation and differentiation of myoblast. Moreover, circPTPN4 suppresses mitochondria biogenesis and activates fast-twitch muscle phenotype. Mechanistically, circPTPN4 can function as a ceRNA to regulate NAMPT expression by sponging miR-499-3p, thus participating in AMPK signaling.

Conclusions

circPTPN4 functions as a ceRNA to regulate NAMPT expression by sponging miR-499-3p, thus promoting the proliferation and differentiation of myoblast, as well as activating fast-twitch muscle phenotype.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00664-1.

Current Issues and Technical Advances in Cultured Meat Production: A Review

As the global population grows, we need a stable protein supply to meet the demands. Although plant-derived protein sources are widely available, animal meat maintains its popularity as a high-quality and savory protein source. Recently, cultured meat, also known as in vitro meat, has been suggested as a meat analog produced through in vitro cell culture technology. Cultured meat has several advantages over conventional meat, such as environmental protection, disease prevention, and animal welfare. However, cultured meat manufacturing is an emerging technology; thus, its further and dynamic development would be pivotal. Commercialization of cultured meat to the public will take a long time but cultured meat undoubtedly will come to our table someday. Here, we discuss the social and economic aspects of cultured meat production as well as the recent technical advances in cultured meat technology.

Expression of MSTN gene and its correlation with pectoralis muscle fiber traits in the domestic pigeons (Columba livia)

Myostatin (MSTN) is a negative regulator of skeletal muscle growth and plays an important role in muscle development. In this research, we constructed a tissue expression profile of the pigeon MSTN gene in eight tissues and a spatio-temporal expression profile in the pectoral muscle using qRT-PCR method. And the pectoralis muscle fiber traits during pigeon post-hatching stages at 1, 7, 14, 21, and 28 D were analyzed through the paraffin sections. Then the correlations between the muscle fiber diameter, cross-sectional area, density, and the expression of MSTN in the pectoral muscle were analyzed. Results showed that MSTN mRNA was mainly expressed in breast muscle, heart, spleen, and kidney and it was almost unexpressed in the liver and lungs. Moreover, the MSTN mRNA expression level in breast muscle was significantly higher than that in other tissues (P < 0.05), and showed an interesting trend that it decreased in the first week and then increased with age. Meanwhile, decrease of myostatin transcripts was accompanied by the down-regulation of Myf5 and the up-regulation of MyoG during the first week post-hatching. In addition, the paraffin sections analysis results revealed that the diameter and cross-sectional area of pectoralis muscle fiber significantly increased with age (P < 0.05), and a significant positive correlation was shown between the MSTN gene expression level and muscle fiber diameter (P < 0.05). These fundamental researches might contribute to further understanding of the roles MSTN played in the post-hatching muscle fiber development in pigeon.

Effect of thermal manipulation during embryogenesis on the promoter methylation and expression of myogenesis-related genes in duck skeletal muscle

Avian embryos are an ideal system to investigate the effect of incubation temperature on embryonic development, but the characteristics and mechanisms of temperature effects on poultry embryonic myogenesis are unclear. In this study, we investigated the effect of increasing the incubation temperature by 1 °C on the expression of nine myogenesis-related genes in ducks and then explored the correlation between the alteration of promoter methylation and the expression of two of the nine genes under thermal manipulation (TM). The qRT-PCR results showed that TM during embryonic days (ED) 1-10 promoted (P < 0.05) the expression of genes in breast muscle (PAX3, PAX7, MYOG, MCK, SIX1, TNNC1) and leg muscle (MYOD, MYOG, MYF5, MCK, AKIRIN2, TNNC1). TM during ED10-20 promoted the expression of PAX3, MYF5 and MCK and inhibited AKIRIN2 expression in breast muscle (P < 0.05); however, it inhibited the expression of PAX3, PAX7, MYOD, MYOG, MYF5, SIX1, AKIRIN2 and TNNC1 and promoted MCK expression in leg muscle (P < 0.05). TM during ED20-27 inhibited the expression of genes in breast muscle (PAX7) and leg muscle (MYOD, MYOG, MYF5, TNNC1) and promoted MCK expression in breast and leg muscle (P < 0.05). Furthermore, with the Sequenom MassARRAY platform, it was observed that the average methylation level of AKIRIN2 (ED10) and TNNC1 (ED20) in leg muscle decreased (P < 0.05) after TM. Notably, we found significant (P < 0.05) inverse correlations between the methylation and mRNA levels of AKIRIN2 under TM during ED1-10 (r = - 0.969) and ED10-20 (r = - 0.805). Taken together, TM during ED1-10 was more favorable for improving duck myogenesis-related gene expression than TM during ED10-20 and ED20-27. TM during duck embryogenesis seemed to have a greater effect on the development of leg muscle than breast muscle and might alter AKIRIN2 expression by changing its promoter methylation status. These findings may be helpful to understand temperature effects on the muscle development of avian embryos and to explore the role of epigenetic regulation during this process.

lncRNA-Six1 Is a Target of miR-1611 that Functions as a ceRNA to Regulate Six1 Protein Expression and Fiber Type Switching in Chicken Myogenesis

Emerging studies indicate important roles for non-coding RNAs (ncRNAs) as essential regulators in myogenesis, but relatively less is known about their function. In our previous study, we found that lncRNA-Six1 can regulate Six1 in cis to participate in myogenesis. Here, we studied a microRNA (miRNA) that is specifically expressed in chickens (miR-1611). Interestingly, miR-1611 was found to contain potential binding sites for both lncRNA-Six1 and Six1, and it can interact with lncRNA-Six1 to regulate Six1 expression. Overexpression of miR-1611 represses the proliferation and differentiation of myoblasts. Moreover, miR-1611 is highly expressed in slow-twitch fibers, and it drives the transformation of fast-twitch muscle fibers to slow-twitch muscle fibers. Together, these data demonstrate that miR-1611 can mediate the regulation of Six1 by lncRNA-Six1, thereby affecting proliferation and differentiation of myoblasts and transformation of muscle fiber types.

Long-term thermal manipulation in the late incubation period can inhibit breast muscle development by activating endoplasmic reticulum stress in duck (Anasplatyrhynchos domestica)

Poultry embryos are easily affected by environmental changings during incubation, thereinto, the temperature modification is the most important one, but the mechanism of temperature effects on bird eggs is not clear. By using RNA-seq, we have previously found that endoplasmic reticulum stress (ERS) may involve in regulating embryonic muscle development of duck under the influence of temperature alteration. To further clarify the role of ERS in the effect, in the present study, we detected the impact of increasing the incubation temperature by 1℃ during embryonic days 10-27 (E10-27) on the development of duck embryos, and investigated the changes in mRNA and protein expression of ERS marker genes and muscle-related genes under the thermal manipulation (TM). The results of relative weight comparison showed that only the relative weight of breast muscle was steadily decreased by TM from E10 to the first day after hatching (W0). Meanwhile, the real-time PCR and western-blot analysis revealed that raising the incubation temperature stimulated the expression of ERS marker genes in breast muscle at E20. The mRNA expressions of muscle hypertrophy and atrophy-related genes were also detected, and were not changed regularly, however, the protein expressions of hypertrophy-related genes were all decreased at both E20 and W0, and the protein expression of atrophy-related genes were up-regulated at E20. The protein expression of muscle proliferation-related genes were also decreased at E20. Additionally, these results were the same as that in the ERS positive control groups. Taken together, these results indicated that long-term TM during late embryonic period could block the development of duck breast muscle by inhibiting muscle hypertrophy and proliferation, and promoting muscle atrophy at a post-transcriptional level via the activation of ERS.

Transiently expressed pattern during myogenesis and candidate miRNAs of Tmem8C in goose

Transmembrane protein 8C (Tmem8C) is a muscle-specific membrane protein that controls myoblast fusion, which is essential for the formation of multinucleated muscle fibres. As most of the birds can fly, they have enormous requirement for the muscle, but there are only a few studies of Tmem8C in birds. In this study, we obtained the coding sequence (CDS) of Tmem8C in goose, predicted miRNAs that can act on the 3'UTR, analysed expression profiles of this gene in breast and leg muscles (BM and LM) during the embryonic period and neonatal stages, and identified miRNAs that might affect the targeted gene. The results revealed a high homology between Tmem8C in goose and other animals (indicated by sequence comparisons and phylogenetic trees), some conservative characteristics (e.g., six transmembrane domains and two E-boxes in the 5'UTR might be the potential binding sites of muscle regulatory factors (MRFs)), and the d_N/d_S ratio indicated purifying selection acting on this gene, facilitating conservatism in vertebrates. Q-PCR indicated Tmem8C had a peak expression pattern, reaching its highest expression levels in stage E15 in LM and E19 in BM, and then dropping transiently in E23 (P < 0.05). We examined 13 candidate miRNAs, and negative relationships were detected both in BM and LM (mir-125b-5p, mir-15a, mir-16-1 and mir-n23). Notably, mir-16-1 significantly decreased luciferase activity in dual luciferase reporter gene (LRG) assay, suggesting that it can be identified as potential factors affecting Tmem8C. This study investigated Tmem8C in water bird for the first time, and provided useful information about this gene and its candidate miRNAs in goose.

The relative expression levels of insulin-like growth factor 1 and myostatin mRNA in the asynchronous development of skeletal muscle in ducks during early development

Genetic selection is a powerful tool for modifying poultry muscle yield. Insulin-like growth factor I (IGF-I) and myostatin (MSTN) are important regulators of muscle growth, especially in the myogenesis stage. This study compared the developmental pattern of the pectoralis major (PM) and lateral gastrocnemius (LM) muscles, mRNA expression characterization of IGF-I and MSTN-A and their correlation between 14 days in ovo and 1 week post-hatch in two Chinese local duck breeds. During early development, the growth of duck PM and LM followed an asynchronous pattern. Variations in PM growth rate observed with development followed the relative variations of MSTN and IGF-I expression; however, the same behavior was not observed in LM. Moreover, the profile of IGF-I expression in duck skeletal muscles indicated that genetic selection for high meat-yield poultry has altered the temporal expression of IGF-I and affected cellular characteristics and mass by hatch in a PM-specific manner. The MSTN-A expression profile showed synchronization with the growth of skeletal muscle and peaks of myofiber proliferation. The expression patterns of IGF-I and MSTN suggest that duck pectoralis fibers are prioritized for proliferation in embryogenesis. The IGF-1/MSTN-A mRNA ratios in PM and LM presented very similar trends in the changes of myofiber characteristics, and differences in the IGF-1/MSTN-A mRNA ratio in PM between the two breeds corresponded to the timing of differences in PM mass between the varieties. Our results support the hypothesis that relative levels of IGF-I and MSTN mRNA may participate in ordering muscle growth rates with selected development.

Identification and characterization of genes related to the development of breast muscles in Pekin duck

Pekin Duck is world-famous for its fast growth, but its breast muscle development is later and breast muscle content is lower compared with other muscular ducks. Therefore, it is very important to discover the genetic mechanism between breast muscle development and relative gene expression in Pekin duck. In current study, the genes which have relationships with breast muscle development were identified by suppression subtractive hybridization. A total of 403 positive clones were sequenced and 257 unigenes were obtained. The expression of 23 genes were analyzed in the breast muscle of 2-, 4-, 6-, 8- week old Pekin ducks. The results showed that unknown clone A233, C83 and C99 showed descending tendency as age increased; KBTBD10, HSPA8, MYL1, ZFP622, MARCH4, Nexilin, FABP4 and MUSTN1 had high expression levels at 6 weeks old; WAC, NT5C3, HSP90AA1, MRPL33, KLF6, TSNAX, CDC42EP3, HSPA4, TRAK1, NR2F2, HAUS1 and IGF1 had high expression levels at 8 weeks and showed ascending tendency as age increased. Expression of these 23 genes were also analyzed in breast muscle, leg muscle, heart, kidney, liver, muscular stomach and sebum cutaneum in 4-8-week old Pekin duck and results showed that most of these genes had high expression in breast muscle, leg muscle and heart.

In ovo feeding of IGF-1 to ducks influences neonatal skeletal muscle hypertrophy and muscle mass growth upon satellite cell activation

To investigate reasons for the muscle increase observed when eggs are treated by IGF-1 and whether or not satellite cell activation is specific to different types of myofibers, duck eggs were administrated with IGF-1. After injection, during the neonatal stages, the duck breast muscle and leg muscle were isolated for analysis. The muscle weight, muscle fiber diameter (MFD), cross-sectional area (CSA), the number of myofibers per unit area (MFN) and frequency of satellite cell activation and mitosis at the embryo stage of 27 days (27E) and the postnatal stage of 2 days after hatching (P2D) were determined. In addition, expression of two important myogenic transcription factors MyoD and Myf5 were detected and compared in the two types of muscle tissues. Results indicated that IGF-1 administration increased the duck body weight, MFD, CSA, MFN, and quantity of activated satellite cells and mitotic nuclei in the two types of muscle tissues. The MyoD and Myf5 expressed at a higher level in IGF-1-treated muscle. IGF-1 stimulated muscle weight growth more in the leg muscle than in the breast muscle. These results indicate that in ovo feeding of IGF-1 can stimulate duck growth and, especially, lead to increased muscle hypertrophy. These increases appear to be mainly dependent on the activation of satellite cells, some of which proliferate and fuse to the myofiber, enabling increased muscle mass. IGF-1 can indirectly affect satellite cells by regulating the expression of two important myogenic transcription factors, MyoD and Myf5, which help activate satellite cells.

Developmental expression and alternative splicing of the duck myostatin gene

Myostatin (MSTN) plays a key role in the negative regulation of muscle growth and development during embryogenesis. The MSTN genes have different genetic characteristics in vertebrates: sole gene in mammals, gene duplication in fish, and alternative splicing in birds. To investigate the alternative splicing sites and developmental expression patterns of the duck MSTN genes, the mRNA and genome sequences were cloned, and the expression patterns were detected during breast muscle and leg muscle development by real-time PCR. In our study, four alternatively spliced forms of MSTN mRNA were found in the developing skeletal muscle of Peking duck, including two novel alternatively spliced transcripts, MSTN-c and MSTN-d. As a result of alternative splicing at the common GT-AG processing sites, MSTN-b and MSTN-c retained only the N-terminal TGFβ-propeptide superfamily domains. However, MSTN-d was not missing these domains, in contrast to MSTN-a. The real-time PCR results showed that there was no significant difference between breast muscle and leg muscle in MSTN-a mRNA expression, also in MSTN-b and MSTN-c. MSTN-a and MSTN-b have significant higher expressions than MSTN-c and MSTN-d, suggesting that they play the major role during embryo muscle development.