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

Effects of atrazine on movement, metabolism and gene expression in Pelophylax nigromaculatus larvae under global warming

Global warming and environmental pollutants both pose a threat to the behavior and physiology of animals, but research on the combined effects of the two is limited. Atrazine, a widely used herbicide, has toxic effects on organisms. In this study, the effects of environmental concentrations of atrazine exposure (100 μg/L) for seven days on the movement, metabolism and gene expression related to motility of Pelophylax nigromaculatus larvae (GS8) were investigated under global warming. The results showed that compared to the optimal growth temperature (18 °C), atrazine treatment under global warming (21 °C) significantly increased the average speed (about 11.2 times) and maximum acceleration (about 1.98 times) of P. nigromaculatus larvae, altered the relative abundance of 539 metabolites, including Formyl-5-hydroxykynurenamine, 2,4-Dihydroxybenzophenone, and FAPy-adenine, and changed the nucleotide metabolism, pyrimidine metabolism, glycerophospholipid metabolism, and purine metabolism, as well as increased the gene expression of SPLA2 (about 6.46 times) and CHK (about 3.25 times). In summary, atrazine treatment under global warming caused metabolic disorders in amphibian larvae and increased the expression of some movement-related genes in the brain, resulting in abnormally active.

Mustn1 in Skeletal Muscle: A Novel Regulator?

Skeletal muscle is a complex organ essential for locomotion, posture, and metabolic health. This review explores our current knowledge of Mustn1, particularly in the development and function of skeletal muscle. Mustn1 expression originates from Pax7-positive satellite cells in skeletal muscle, peaks during around the third postnatal month, and is crucial for muscle fiber differentiation, fusion, growth, and regeneration. Clinically, Mustn1 expression is potentially linked to muscle-wasting conditions such as muscular dystrophies. Studies have illustrated that Mustn1 responds dynamically to injury and exercise. Notably, ablation of Mustn1 in skeletal muscle affects a broad spectrum of physiological aspects, including glucose metabolism, grip strength, gait, peak contractile strength, and myofiber composition. This review summarizes our current knowledge of Mustn1's role in skeletal muscle and proposes future research directions, with a goal of elucidating the molecular function of this regulatory gene.

Transcriptome Profiling Identifies Differentially Expressed Genes in Skeletal Muscle Development in Native Chinese Ducks

China boasts a rich diversity of indigenous duck species, some of which exhibit desirable economic traits. Here, we generated transcriptome sequencing datasets of breast muscle tissue samples from 1D of four groups: Pekin duck pure breeding group (P), Jinling White duck breeding group (J), P ♂ × J ♀ orthogonal group (PJ) and J ♂ × P ♀ reciprocal-cross group (JP) (n = 3), chosen based on the distinctive characteristics of duck muscle development during the embryonic period. We identified 5053 differentially expressed genes (DEGs) among the four groups. Network prediction analysis showed that ribosome and oxidative phosphorylation-related genes were the most enriched, and muscular protein-related genes were found in the 14-day-old embryonic group. We found that previously characterized functional genes, such as FN1, AGRN, ADNAMST3, APOB and FGF9, were potentially involved in muscle development in 14-day-old embryos. Functional enrichment analysis suggested that genes that participated in molecular function and cell component and key signaling pathways (e.g., hippo, ribosome, oxidative phosphorylation) were significantly enriched in the development of skeletal muscle at 14 days of embryonic age. These results indicate a possible role of muscle metabolism and myoglobin synthesis in skeletal muscle development in both duck parents and hybrids.

Mustn1 ablation in skeletal muscle results in functional alterations

Mustn1, a gene expressed exclusively in the musculoskeletal system, was shown in previous in vitro studies to be a key regulator of myogenic differentiation and myofusion. Other studies also showed Mustn1 expression associated with skeletal muscle development and hypertrophy. However, its specific role in skeletal muscle function remains unclear. This study sought to investigate the effects of Mustn1 in a conditional knockout (KO) mouse model in Pax7 positive skeletal muscle satellite cells. Specifically, we investigated the potential effects of Mustn1 on myogenic gene expression, grip strength, alterations in gait, ex vivo investigations of isolated skeletal muscle isometric contractions, and potential changes in the composition of muscle fiber types. Results indicate that Mustn1 KO mice did not present any substantial phenotypic changes or significant variations in genes related to myogenic differentiation and fusion. However, an approximately 10% decrease in overall grip strength was observed in the 2-month-old KO mice in comparison to the control wild type (WT), but this decrease was not significant when normalized by weight. KO mice also generated approximately 8% higher vertical force than WT at 4 months in the hindlimb. Ex vivo experiments revealed decreases in about 20 to 50% in skeletal muscle contractions and about 10%-20% fatigue in soleus of both 2- and 4-month-old KO mice, respectively. Lastly, immunofluorescent analyses showed a persistent increase of Type IIb fibers up to 15-fold in the KO mice while Type I fibers decreased about 20% and 30% at both 2 and 4 months, respectively. These findings suggest a potential adaptive or compensatory mechanism following Mustn1 loss, as well as hinting at an association between Mustn1 and muscle fiber typing. Collectively, Mustn1's complex roles in skeletal muscle physiology requires further research, particularly in terms of understanding the potential role of Mustn1 in muscle repair and regeneration, as well as with influence of exercise. Collectively, these will offer valuable insights into Mustn1's key biological functions and regulatory pathways.

Genome-wide epigenetic dynamics during postnatal skeletal muscle growth in Hu sheep

Hypertrophy and fiber transformation are two prominent features of postnatal skeletal muscle development. However, the role of epigenetic modifications is less understood. ATAC-seq, whole genome bisulfite sequencing, and RNA-seq were applied to investigate the epigenetic dynamics of muscle in Hu sheep at 3 days, 3 months, 6 months, and 12 months after birth. All 6865 differentially expressed genes were assigned into three distinct tendencies, highlighting the balanced protein synthesis, accumulated immune activities, and restrained cell division in postnatal development. We identified 3742 differentially accessible regions and 11799 differentially methylated regions that were associated with muscle-development-related pathways in certain stages, like D3-M6. Transcription factor network analysis, based on genomic loci with high chromatin accessibility and low methylation, showed that ARID5B, MYOG, and ENO1 were associated with muscle hypertrophy, while NR1D1, FADS1, ZFP36L2, and SLC25A1 were associated with muscle fiber transformation. Taken together, these results suggest that DNA methylation and chromatin accessibility contributed toward regulating the growth and fiber transformation of postnatal skeletal muscle in Hu sheep.

Integrative analysis of circRNA, miRNA, and mRNA profiles to reveal ceRNA regulation in chicken muscle development from the embryonic to post-hatching periods

Background

The growth and development of skeletal muscle are regulated by protein-coding genes and non-coding RNA. Circular RNA (circRNA) is a type of non-coding RNA involved in a variety of biological processes, especially in post-transcriptional regulation. To better understand the regulatory mechanism of circRNAs during the development of muscle in chicken, we performed RNA-seq with linear RNA depletion for chicken breast muscle in 12 (E 12) and17 (E 17) day embryos, and 1 (D 1), 14 (D 14), 56 (D 56), and 98 (D 98) days post-hatch.

Results

We identified 5755 differentially expressed (DE)-circRNAs during muscle development. We profiled the expression of DE-circRNAs and mRNAs (identified in our previous study) at up to six time points during chicken muscle development and uncovered a significant profile (profile 16) for circRNA upregulation during aging in muscle tissues. To investigate competing endogenous RNA (ceRNA) regulation in muscle and identify muscle-related circRNAs, we constructed a circRNA-miRNA-mRNA regulatory network using the circRNAs and mRNAs from profile 16 and miRNAs identified in our previous study, which included 361 miRNAs, 68 circRNAs, 599 mRNAs, and 31,063 interacting pairs. Functional annotation showed that upregulated circRNAs might contribute to glycolysis/gluconeogenesis, biosynthesis of amino acids, pyruvate metabolism, carbon metabolism, glycogen and sucrose metabolism through the ceRNA network, and thus affected postnatal muscle development by regulating muscle protein deposition. Of them, circRNA225 and circRNA226 from the same host gene might be key circRNAs that could regulate muscle development by interacting with seven common miRNAs and 207 mRNAs. Our experiments also demonstrated that there were interactions among circRNA225, gga-miR-1306-5p, and heat shock protein alpha 8 (HSPA8).

Conclusions

Our results suggest that adequate supply of nutrients such as energy and protein after hatching may be a key factor in ensuring chicken yield, and provide several candidate circRNAs for future studies concerning ceRNA regulation during chicken muscle development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08525-5.

Genomic diversity and signatures of selection in meat and fancy rabbit breeds based on high-density marker data

Background

Domestication of the rabbit (Oryctolagus cuniculus) has led to a multi-purpose species that includes many breeds and lines with a broad phenotypic diversity, mainly for external traits (e.g. coat colours and patterns, fur structure, and morphometric traits) that are valued by fancy rabbit breeders. As a consequence of this human-driven selection, distinct signatures are expected to be present in the rabbit genome, defined as signatures of selection or selective sweeps. Here, we investigated the genome of three Italian commercial meat rabbit breeds (Italian Silver, Italian Spotted and Italian White) and 12 fancy rabbit breeds (Belgian Hare, Burgundy Fawn, Champagne d’Argent, Checkered Giant, Coloured Dwarf, Dwarf Lop, Ermine, Giant Grey, Giant White, Rex, Rhinelander and Thuringian) by using high-density single nucleotide polymorphism data. Signatures of selection were identified based on the fixation index (F_ST) statistic with different approaches, including single-breed and group-based methods, the latter comparing breeds that are grouped based on external traits (different coat colours and body sizes) and types (i.e. meat vs. fancy breeds).

Results

We identified 309 genomic regions that contained signatures of selection and that included genes that are known to affect coat colour (ASIP, MC1R and TYR), coat structure (LIPH), and body size (LCORL/NCAPG, COL11A1 and HOXD) in rabbits and that characterize the investigated breeds. Their identification proves the suitability of the applied methodologies for capturing recent selection events. Other regions included novel candidate genes that might contribute to the phenotypic variation among the analyzed breeds, including genes for pigmentation-related traits (EDNRA, EDNRB, MITF and OCA2) and body size, with a strong candidate for dwarfism in rabbit (COL2A1).

Conclusions

We report a genome-wide view of genetic loci that underlie the main phenotypic differences in the analyzed rabbit breeds, which can be useful to understand the shift from the domestication process to the development of breeds in O. cuniculus. These results enhance our knowledge about the major genetic loci involved in rabbit external traits and add novel information to understand the complexity of the genetic architecture underlying body size in mammals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12711-022-00696-9.

MUSTN1 is an indispensable factor in the proliferation, differentiation and apoptosis of skeletal muscle satellite cells in chicken

The yield and quality of the skeletal muscle are important economic traits in livestock and poultry production. The musculoskeletal embryonic nuclear protein 1 (MUSTN1) gene has been shown to be associated with embryonic development, postnatal growth, bone and skeletal muscle regeneration; however, its function in the skeletal muscle development of chicken remains unclear. Therefore, in this study, we observed that the expression level of MUSTN1 increased in conjunction with the proliferation of chicken skeletal muscle satellite cells (SMSCs). Knockdown of MUSTN1 in SMSCs downregulated the expression of cell proliferation genes as Pax7, CDK-2 and differentiation-relate genes including MyoD, MyoG, MyHC and MyH1B, whereas it upregulates the expression of cell apoptosis gene (Caspase-3) (P < 0.05). However, the combined analysis of CCK-8 and EdU showed that the cell vitality and EdU-positive cells of the si-MUSTN1 transfected group were significantly lower than those of the negative siRNA group (P < 0.05). In addition, the knockdown of MUSTN1 significantly increased the cell population in the G0/G1 phase and significantly decreased the cell population in the G2/M phase (P < 0.05), whereas the overexpression of MUSTN1 showed opposite effect. Taken together, our findings indicates that MUSTN1 is an important molecular factor that is responsible for regulating muscle growth and development in chickens, particularly, proliferation and differentiation of SMSCs.

Single nucleotide polymorphism scanning and expression analysis of ACSL1 from different duck breeds

Accumulating studies have indicated that the long-chain fatty acyl-CoA1 (ACSL1) gene is related to fat deposition and meat quality in mammals. However, few studies have investigated the relationship between ACSL1 and lipid deposition in ducks. To examine this, we assessed the physicochemical property, homologous alignment, and phylogenetic analyses of the ACSL1 amino acid sequence using bioinformatics tools. The analysis indicated that the ACSL1 amino acid sequence varies in animals, and the duck ACSL1 protein is most closely related to that of chicken. Two single nucleotide polymorphism (SNP) sites were identified at 1749 and 1905 bp of the coding region of ACSL1 by sequencing. Quantitative real-time PCR and western blotting were used to measure mRNA and protein levels in abdominal fat, breast muscle, and liver tissue of Pekin duck (BD) and Cherry Valley duck (CD). mRNA and protein expression were significantly higher in BD than in CD in abdominal fat and liver tissue (P < 0.05). In breast muscle, the mRNA level of ACSL1 was also significantly higher in BD than in CD (P < 0.05), and protein expression in BD tended to be higher than that of CD. These results suggest that ACSL1 may contribute to lipid deposition and meat quality in ducks.

Dietary resveratrol supplement improves carcass traits and meat quality of Pekin ducks

With the increase of consumer demand for high-quality animal protein, it becomes imperative to improve meat quality through nutritional strategy. Resveratrol is a plant polyphenol that exists in grapes and grape products, and it has been considered as a potential functional feed additive. Here, we aimed to explore the optimal dose of resveratrol in Pekin ducks' diet and its effect on improving meat quality. A total of 432 male Pekin ducks (1-day-old) were selected and randomly allotted to 4 treatment groups, with each group containing 6 replicates. Four different levels of resveratrol were evaluated (0, 150, 300, and 450 mg/kg) for 42 d. The carcass traits, meat quality, and muscle fiber characteristics of Pekin ducks were investigated. Results showed that a∗_24h, b∗_24h, intramuscular fat, crude protein, total flavor amino acid content of duck breast muscle, and a∗_45min of duck leg muscle were increased (P < 0.05) by resveratrol. Resveratrol also reduced abdominal fat deposition, shear force, L∗_45min of breast muscle and drip loss, shear force, and L∗_45min of leg muscle. In addition, the breast muscle fibers of resveratrol-fed ducks had lower diameter and cross-sectional area and higher density (P < 0.05). Overall, we conclude that dietary resveratrol supplement can effectively improve Pekin duck meat quality, the optimal additional range in diet being 300 to 450 mg/kg. Its underlying mechanism might be partly through stimulation of intramuscular fat and flavor amino deposition and alteration of muscle fiber characteristics.

Mechanism and Functions of Identified miRNAs in Poultry Skeletal Muscle Development – A Review

Development of the skeletal muscle goes through several complex processes regulated by numerous genetic factors. Although much efforts have been made to understand the mechanisms involved in increased muscle yield, little work is done about the miRNAs and candidate genes that are involved in the skeletal muscle development in poultry. Comprehensive research of candidate genes and single nucleotide related to poultry muscle growth is yet to be experimentally unraveled. However, over a few periods, studies in miRNA have disclosed that they actively participate in muscle formation, differentiation, and determination in poultry. Specifically, miR-1, miR-133, and miR-206 influence tissue development, and they are highly expressed in the skeletal muscles. Candidate genes such as CEBPB, MUSTN1, MSTN, IGF1, FOXO3, mTOR, and NFKB1, have also been identified to express in the poultry skeletal muscles development. However, further researches, analysis, and comprehensive studies should be made on the various miRNAs and gene regulatory factors that influence the skeletal muscle development in poultry. The objective of this review is to summarize recent knowledge in miRNAs and their mode of action as well as transcription and candidate genes identified to regulate poultry skeletal muscle development.

Genomic variation in Pekin duck populations developed in three different countries as revealed by whole-genome data

It is well known that both British and American Pekin ducks originated from China. However, the populations differ substantially in production performance, but the genetic changes involved are still poorly understood. Herein, we sequenced 24 individual Pekin ducks (eight from each population) with an average sequencing depth of more than 45× for each population (mean coverage of 6.29 per individual). Among these populations from three different countries, we identified a large number of SNPs and indels as well as many unique population variants, which can be used as population-specific molecular markers. Genomic comparisons among the three duck populations revealed many candidate genes as well as pathways and Gene Ontology categories that are putatively associated with meat yield in the British population, growth in the American population and brain development in all three populations. These findings will enable a better understanding of the artificial selection history of Pekin ducks and provide a valuable resource for future research on the breeding of this species.

Mustn1: A Developmentally Regulated Pan-Musculoskeletal Cell Marker and Regulatory Gene

The Mustn1 gene encodes a small nuclear protein (~9.6 kDa) that does not belong to any known family. Its genomic organization consists of three exons interspersed by two introns and it is highly homologous across vertebrate species. Promoter analyses revealed that its expression is regulated by the AP family of transcription factors, especially c-Fos, Fra-2 and JunD. Mustn1 is predominantly expressed in the major tissues of the musculoskeletal system: bone, cartilage, skeletal muscle and tendon. Its expression has been associated with normal embryonic development, postnatal growth, exercise, and regeneration of bone and skeletal muscle. Moreover, its expression has also been detected in various musculoskeletal pathologies, including arthritis, Duchenne muscular dystrophy, other skeletal muscle myopathies, clubfoot and diabetes associated muscle pathology. In vitro and in vivo functional perturbation revealed that Mustn1 is a key regulatory molecule in myogenic and chondrogenic lineages. This comprehensive review summarizes our current knowledge of Mustn1 and proposes that it is a new developmentally regulated pan-musculoskeletal marker as well as a key regulatory protein for cell differentiation and tissue growth.

Gene expression profiling in Pekin duck embryonic breast muscle

Lean-type Pekin duck is a breed gained through long-term selection and great effort has been exerted to understand the mechanisms underlying increased muscle yields. However, the genes involved in Pekin duck embryonic breast muscle development have not been explored to date. In this study, we investigated gene expression profiles in Pekin Duck embryonic breast muscle at hatched day 13 (E13), E19, and E27 using RNA-seq. In total, we produced 519,312,178 raw reads resulting in 497,348,158 high-quality reads after filtering. The mapping, distribution of reads along annotated genes, and consistency across replicates demonstrates the high quality of the RNA-seq data used in this study, allowing us to continue with the downstream analysis. Significantly fewer differentially expressed genes (DEGs) were identified between E13 and E19 (203 DEGs) compared to E27 and E19 (2,797 DEGs). Many DEGs highly expressed in E19 are involved in metabolic processes and cell division. KEGG analysis showed many pathways associated with fat development were significantly enriched for DEGs highly expressed in E27. These results provide a basis for the further investigation of the mechanisms involved in Pekin duck embryonic breast muscle development.

Mining the key regulatory genes of chicken inosine 5'-monophosphate metabolism based on time series microarray data

IMP (inosine 5'-monophosphate) is a compound that enhances the flavor of poultry meat. IMP has become a new breeding trait to improve poultry meat quality. We tried to identify several potential regulatory genes, and construct their predicted regulatory relationships. Time series gene expression profiles of thigh muscle tissues of Rugao chicken, a famous indigenous breed in China, were performed for analysis of genes that are co-expressed or correlated with the concentration of IMP. We found 15 crucial co-expression genes, which are Hspa2, Pten, Gabpa, Bpi, Mkl1, Srf, Cd34, Hspa4, Etv6, Bmpr2, Gde1, Igfbp5, Cd28, Pecam1 and Gja1, that may directly or indirectly regulate IMP metabolism. Eventually, we computed the correlation coefficient between 19 IMP Genes and 15 CGs (15 co-expression genes), and we identified and constructed a predicted regulation network. In conclusion, variation of IMP concentration was primarily connected with the muscle development process. During this process, 15 CGs were identified that may have significant influence on IMP metabolism. In particular, Bmpr2, Pten and co-expression genes correlated with Entpd8 might play important roles in regulating IMP de novo synthesis, decomposition and salvage synthesis.

Identification of differentially expressed genes related to metabolic syndrome induced with high-fat diet in E3 rats

Understanding the genes differentially expressing in aberrant organs of metabolic syndrome (MetS) facilitates the uncovering of molecular mechanisms and the identification of novel therapeutic targets for the disease. This study aimed to identify differentially expressed genes related to MetS in livers of E3 rats with high-fat-diet-induced metabolic syndrome (HFD-MetS). E3 rats were fed with high-fat diet for 24 weeks to induce MetS. Then, suppression subtractive hybridization (SSH) technology was used to identify the genes differentially expressed between HFD-MetS and control E3 rat livers. Twenty positive recombinant clones were chosen randomly from forward subtractive library and sent to sequence. BLAST analysis in GenBank database was used to determine the property of each cDNA fragment. In total, 11 annotated genes, 3 ESTs, and 2 novel gene fragments were identified by SSH technology. The expression of four genes (Alb, Pip4k2a, Scd1, and Tf) known to be associated with MetS and other five genes (Eif1, Rnase4, Rps12, Rup2, and Tmsb4) unknown to be relevant to MetS was significantly up-regulated in the livers of HFD-MetS E3 rats compared with control rats using real-time quantitative PCR (RT-qPCR). By analyzing the correlations between the expression of these nine genes and serum concentrations of TG, Tch, HDL-C, and LDL-C, we found that there were significant positive correlations between TG and the expression of five genes (Alb, Eif1, Pip4k2a, Rps12, and Tmsb4x), Tch and three genes (Rnase4, Scd1, and Tmsb4x), and LDL-C and two genes (Rnase4 and Scd1), as well there were significant negative correlations between HDL-C and the expression of three genes (Rup2, Scd1, and Tf). This study provides important clues for unraveling the molecular mechanisms of MetS.

Identification of differentially expressed genes in breast muscle and skin fat of postnatal Pekin duck

Lean-type Pekin duck is a commercial breed that has been obtained through long-term selection. Investigation of the differentially expressed genes in breast muscle and skin fat at different developmental stages will contribute to a comprehensive understanding of the potential mechanisms underlying the lean-type Pekin duck phenotype. In the present study, RNA-seq was performed on breast muscle and skin fat at 2-, 4- and 6-weeks of age. More than 89% of the annotated duck genes were covered by our RNA-seq dataset. Thousands of differentially expressed genes, including many important genes involved in the regulation of muscle development and fat deposition, were detected through comparison of the expression levels in the muscle and skin fat of the same time point, or the same tissue at different time points. KEGG pathway analysis showed that the differentially expressed genes clustered significantly in many muscle development and fat deposition related pathways such as MAPK signaling pathway, PPAR signaling pathway, Calcium signaling pathway, Fat digestion and absorption, and TGF-beta signaling pathway. The results presented here could provide a basis for further investigation of the mechanisms involved in muscle development and fat deposition in Pekin duck.

Genome-wide Association Study of Integrated Meat Quality-related Traits of the Duroc Pig Breed

The increasing importance of meat quality has implications for animal breeding programs. Research has revealed much about the genetic background of pigs, and many studies have revealed the importance of various genetic factors. Since meat quality is a complex trait which is affected by many factors, consideration of the overall phenotype is very useful to study meat quality. For integrating the phenotypes, we used principle component analysis (PCA). The significant SNPs refer to results of the GRAMMAR method against PC1, PC2 and PC3 of 14 meat quality traits of 181 Duroc pigs. The Genome-wide association study (GWAS) found 26 potential SNPs affecting various meat quality traits. The loci identified are located in or near 23 genes. The SNPs associated with meat quality are in or near five genes (ANK1, BMP6, SHH, PIP4K2A, and FOXN2) and have been reported previously. Twenty-five of the significant SNPs also located in meat quality-related QTL regions, these result supported the QTL effect indirectly. Each single gene typically affects multiple traits. Therefore, it is a useful approach to use integrated traits for the various traits at the same time. This innovative approach using integrated traits could be applied on other GWAS of complex-traits including meat-quality, and the results will contribute to improving meat-quality of pork.

Identification of differentially expressed genes of Trichinella spiralis larvae after exposure to host intestine milieu

Although it has been known for many years that T. spiralis muscle larvae (ML) can not invade intestinal epithelial cells unless they are exposed to the intestinal milieu and activated into intestinal infective larvae (IIL), which genes in IIL are involved in the process of invasion is still unknown. In this study, suppression subtractive hybridization (SSH) was performed to identify differentially expressed genes between IIL and ML. SSH library was constructed using cDNA generated from IIL as the ‘tester’. About 110 positive clones were randomly selected from the library and sequenced, of which 33 T. spiralis genes were identified. Thirty encoded proteins were annotated according to Gene Ontology Annotation in terms of molecular function, biological process, and cellular localization. Out of 30 annotated proteins, 16 proteins (53.3%) had binding activity and 12 proteins (40.0%) had catalytic activity. The results of real-time PCR showed that the expression of nine genes (Ts7, Ndr family protein; Ts8, serine/threonine-protein kinase polo; Ts11, proteasome subunit beta type-7; Ts17, nudix hydrolase; Ts19, ovochymase-1; Ts22, fibronectin type III domain protein; Ts23, muscle cell intermediate filament protein OV71; Ts26, neutral and basic amino acid transport protein rBAT and Ts33, FACT complex subunit SPT16) from 33 T. spiralis genes in IIL were up-regulated compared with that of ML. The present study provide a group of the potential invasion-related candidate genes and will be helpful for further studies of mechanisms by which T. spiralis infective larvae recognize and invade the intestinal epithelial cells.

A novel GFP reporter mouse reveals Mustn1 expression in adult regenerating skeletal muscle, activated satellite cells and differentiating myoblasts

AIM

Mustn1 has been implicated in myofusion as well as skeletal muscle growth and repair; however, the exact role and spatio-temporal expression of Mustn1 have yet to be fully defined.

METHODS

Transgenic mice were generated with a 1512-bp sequence of the Mustn1 promoter directing the expression of GFP (Mustn1(PRO) -GFP). These mice were used to investigate the spatio-temporal expression of Mustn1(PRO) -GFP during skeletal muscle development and adult skeletal muscle repair, as well as various phases of the satellite cell lifespan (i.e. quiescence, activation, proliferation, differentiation).

RESULTS

Mustn1(PRO) -GFP expression was observed within somites at embryonic day 12 and developing skeletal muscles at embryonic day 15 and 18. While uninjured adult tibialis anterior muscle displayed no detectable Mustn1(PRO) -GFP expression, cardiotoxin injury robustly elevated Mustn1(PRO) -GFP expression at 3 days post-injury with decreasing levels observed at 5 days and minimal, focal expression seen at 10 days. The expression of Mustn1(PRO) -GFP at 3 days post-injury consistently overlaid with MyoD although the strongest expression of Mustn1(PRO) -GFP was noted in newly formed myotubes that were expressing minimal levels of MyoD. By 5 days post-injury, Mustn1(PRO) -GFP overlaid in all myotubes expressing myogenin although cells were present expressing Mustn1(PRO) -GFP alone. The expression patterns of Mustn1(PRO) -GFP in regenerating muscle preceded the expression of desmin throughout the regenerative time course consistent with Mustn1 being upstream of this myogenic protein. Further, quiescent satellite cells located on freshly isolated, single myofibers rarely expressed Mustn1(PRO) -GFP, but within 24 h of isolation, all activated satellite cells expressed Mustn1(PRO) -GFP. Expression of Mustn1(PRO) -GFP in primary myoblasts diminished with prolonged time in proliferation media. However, in response to serum withdrawal, the expression of Mustn1(PRO) -GFP increased during myofusion (day 2) followed by declining expression thereafter.

CONCLUSION

Mustn1(PRO) -GFP is expressed in activated satellite cells and myoblasts but continued time in proliferation media diminished Mustn1(PRO) -GFP expression. However, myoblasts exposed to serum withdrawal increased Mustn1(PRO) -GFP expression consistent with its demonstrated role in myofusion. The in vivo expression pattern of Mustn1 observed in regenerating and developing skeletal muscle is consistent with its presence in satellite cells and its critical role in myofusion.

MUSTN1 mRNA Abundance and Protein Localization is Greatest in Muscle Tissues of Chinese Meat-Quality Chickens

The Mustang, Musculoskeletal Temporally Activated Novel-1 Gene (MUSTN1) plays an important role in regulating musculoskeletal development in mammals. We evaluated the developmental and tissue-specific regulation of MUSTN1 mRNA and protein abundance in Erlang Mountainous (EM) chickens. Results indicated that MUSTN1 mRNA/protein was expressed in most tissues with especially high expression in heart and skeletal muscle. The MUSTN1 protein localized to the nucleus in myocardium and skeletal muscle fibers. There were significant differences in mRNA and protein abundance among tissues, ages and between males and females. In conclusion, MUSTN1 was expressed the greatest in skeletal muscle where it localized to the nucleus. Thus, in chickens MUSTN1 may play a vital role in muscle development.