A 1.1 Mb duplication CNV on chromosome 17 contributes to skeletal muscle development in Boer goats

The Boer goat is one of the top meat breeds in modern animal husbandry and has attracted widespread attention for its unique growth performance.However,the genetic basis of muscle development in the Boer goat remains obscure.In this study,we identified specific structural variants in the Boer goat based on genome-wide selection signals and analyzed the basis of the molecular heredity of related candidate genes in muscle development.A total of9 959 autosomal copy number variations(CNVs) were identified through selection signal analysis in 127 goat genomes.Specifically,we confirmed that the highest signal CNV(HSV) was a chromosomal arrangement containing an approximately 1.11 Mb(CHIR17:60062304-61171840 bp) duplicated fragment inserted in reverse orientation and a 5 362 bp deleted region(CHIR17:60145940-60151302 bp) with overlapping genes(e.g.,ARHGAP10,NR3C2,EDNRA,PRMT9,and TMEM184C).The homozygous duplicated HSV genotype(+/+) was found in 96% of Boer goats but was not detected in Eurasian goats and was only detected in 4% of indigenous African goats.The expression network of three candidate genes(ARHGAP10,NR3C2,and EDNRA)regulating dose transcription was constructed by RNA sequencing.Results indicated that these genes were involved in the proliferation and differentiation of skeletal muscle satellite cells(SMSCs) and their overexpression significantly increased the expression of SAA3.The HSV of the Boer goat contributed to superior skeletal muscle growth via the dose effects of overlapping genes.

Vitamin A regulates intramuscular adipose tissue and muscle development:promoting high-quality beef production

During growth in cattle,the development of intramuscular adipose tissue and muscle is dependent upon cell hyperplasia(increased number of adipocytes)and hypertrophy(increased size of adipocytes).Based on the results of previous studies,other adipose tissue depots(e.g.,perirenal and subcutaneous)develop from the fetal stage primarily as brown adipose tissue.The hyperplastic stage of intramuscular adipose is considered to develop from late pregnancy,but there is no evidence indicating that intramuscular adipose tissue develops initially as brown adipose tissue.Hyperplastic growth of intramuscular adipose continues well into postweaning and is dependent on the timing of the transition to grain-based diets;thereafter,the late-stage development of intramuscular adipose tissue is dominated by hypertrophy.For muscle development,hyperplasia of myoblasts lasts from early(following development of somites in the embryo)to middle pregnancy,after which growth of muscle is the result of hypertrophy of myofibers.Vitamin A is a fat-soluble compound that is required for the normal immunologic function,vision,cellular proliferation,and differentiation.Here we review the roles of vitamin A in intramuscular adipose tissue and muscle development in cattle.Vitamin A regulates both hyperplasia and hypertrophy in in vitro experiments.Vitamin A supplementation at the early stage and restriction at fattening stage generate opposite effects in the beef cattle.Appropriate vitamin A supplementation and restriction strategy increase intramuscular adipose tissue development(i.e.,marbling or intramuscular fat)in some in vivo trials.Besides,hyperplasia and hypertrophy of myoblasts/myotubes were affected by vitamin A treatment in in vitro trials.Additionally,some studies reported an interaction between the alcohol dehydrogenase-1C(ADH1C)genotype and vitamin A feed restriction for the development of marbling and/or intramuscular adipose tissue,which was dependent on the timing and level of vitamin A restriction.Therefore,the feed strategy of vitamin A has the visible impact on the marbling and muscle development in the cattle,which will be helpful to promote the quality of the beef.

Dynamic Expression of MicroRNA-127 During Porcine Prenatal and Postnatal Skeletal Muscle Development

MicroRNAs （miRNAs）, evolutionarily conserved non-coding RNAs in length 21-24 bp, play a critical role in skeletal muscle development. In this study, to explore the function of mircoRNA-127 in porcine skeletal muscle development, eight tissue samples from adult pigs and longissimus muscle samples at 26 developmental stages were collected from Tongcheng and Landrace pigs. The spatial-temporal expression proifles of miRNA-127 were carried out using step-loop quantitative real-time PCR （stem-loop RT-PCR）. To explore the molecular functions of miRNA-127, we predicted its target genes and performed functional annotation using bioinformatics methods. Results suggested that miRNA-127 was abundantly expressed in heart, ovary, uterus and spleen tissues and was weakly expressed in liver, lung, kidney and small intestine in both Tongcheng and Landrace pigs. And miRNA-127 showed signiifcant expression differences in heart, ovary, spleen and uterus tissues between these two breeds. miRNA-127 basically kept at a relatively stable high level in middle and later embryonic stages and a low expression level in early embryonic stages and postnatal stages, but the expression levels of miRNA-127 were higher in Tongcheng pigs than in Landrace at most developmental stages. miRNA-127 potentially regulated 240 candidate genes. Results of Gene Ontology and KEGG pathway analysis indicated that these genes could be involved in many molecular functions and mechanisms, such as regulation of the force of heart contraction, regulation of transcription, regulation of T cell differentiation, MAPK signaling pathway and GnRH signaling pathway. Many signiifcantly enriched GO terms and KEGG pathways were related to skeletal muscle development. This study will be helpful to understand the biological function for miRNA-127 and identify candidate gene associated with meat production traits in pigs.

Modified halloysite nanotubes reduce the toxic effects of zearalenone in gestating sows on growth and muscle development of their offsprings

Background： Zearalenone （ZEN） is an estrogenic mycotoxin that is primarily produced by Fusarium fungi and has been proven to affect the reproductive capacity of many species to varying degrees. The present experiment was designed to study the maternal persistent effects of zearalenone toxicity in gestating sows on growth and muscle development of their offsprings, and the alleviation of zearalenone toxicity by modified halloysite nanotubes （MHNTs）. Methods： Eighteen sows were fed with one of three dietary treatments that included the following： （1） a control diet, （2） a contaminated grain diet （with 50 % moldy corn, 2.77 mg/kg ZEN）, and （3） a contaminated grain diet （with 50 % moldy corn, 2.76 mg/kg ZEN） ＋ 1% MHNTs. Each sow was exclusively fed its experimental diets from 35 to 70 d of gestation at a total of 2 kg daily. Muscle samples were collected from six piglets per treatment at birth, weaning and finishing. Results： The results showed that feeding the sows with the ZEN-contaminated diets from 35 to 70 d of gestation decreased the ADG, ADFI and G：F of their offsprings （P 〈 0.05）. The muscle fiber numbers in the newborn, weaning and growing-finishing pigs and the muscle fiber diameters at birth and weaning were also decreased by maternal ZEN exposure （P 〈 0.05）. The expressions of IGF-I, IGF-II, Myf-5 and Mstn at birth and IGF-II, Pax7, Myf-5 and MyoD1 at weaning were altered by feeding gestating sows with ZEN-contaminated diets （P 〈 0.05）. The MHNTs reduced most of the ZEN-induced toxic effects： the ADG and ADFI on growth performance, the muscle fiber numbers at weaning and finishing and the muscle fiber diameters at weaning （P 〈 0.05）. The expression levels of IGF-II and Mstn in newborn piglets and IGF-II and Myf-5 in weaning piglets were also prevented by adding 1% MHNTs （P 〈 0.05）. Conclusions： The present study demonstrated that the offsprings of sows fed with ZEN-contaminated diets from 35 to 70 day of gestation exhibited weakening on growth performance, physiological changes in their muscle fibers and alterations of mRNA expression in their muscle tissues, and also indicated that MHNTs prevented most of the ZEN- induced weakening in the muscle tissues.

Poor maternal nutrition inhibits muscle development in ovine offspring

Background： Maternal over and restricted nutrition has negative consequences on the muscle of offspring by reducing muscle fiber number and altering regulators of muscle growth. To determine if over and restricted maternal nutrition affected muscle growth and gene fed 60%, 100% or 140% of National Research Council and protein expression in offspring, 36 pregnant ewes were requirements from d 31 ＋ 1,3 of gestation until parturition. Lambs from control-fed （CON）, restricted-fed （RES） or over-fed （OVER） ewes were necropsied within 1 d of birth （n = 18） or maintained on a control diet for 3 mo （n = ] 5）. Semitendinosus muscle was collected for immunohistochemistry, and protein and gene expression analysis. Results： Compared with CON, muscle fiber cross-sectional area （CSA） increased in RES （58%） and OVER （47%） lambs at 1 d of age （P〈 0.01）; however at 3 mo, CSA decreased 15% and 17% compared with CON, respectively （P 〈 0.01）. Compared with CON, muscle lipid content was increased in OVER （212.4%） and RES （92.5%） at d 1 （P 〈 0.0001）. Muscle lipid content was increased 36.1% in OVER and decreased 23.6% in RES compared with CON at 3 mo （P 〈 0.0001）. At d 1, myostatin mRNA abundance in whole muscle tended to be greater in OVER （P = 0.07） than CON. Follistatin mRNA abundance increased in OVER （P = 0.04） and tended to increase in RES （P = 0.06） compared with CON at d 1. However, there was no difference in myostatin or follistatin protein expression （P 〉 0.3）. Phosphorylated Akt （ser473） was increased in RES at 3 mo compared with CON （P = 0.006）. Conclusions： In conclusion, maternal over and restricted nutrient intake alters muscle lipid content and growth of offspring, possibly through altered gene and protein expression.

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 146.92μg/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-β(TGF-β)/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 collagenⅠ,lamininβ1 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 26.77μg/kg diet according to the PC levels in grass carp muscle.

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.

Tumor necrosis factor α deficiency promotes myogenesis and muscle regeneration

Tumor necrosis factorα(TNFα)exhibits diverse biological functions;however,its regulatory roles in myogenesis are not fully understood.In the present study,we explored the function of TNFαin myoblast proliferation,differentiation,migration,and myotube fusion in primary myoblasts and C2C12 cells.To this end,we constructed TNFαmuscle-conditional knockout(TNFα-CKO)mice and compared them with flox mice to assess the effects of TNFαknockout 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 TNFαdeficiency 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.

The genetic regulation of skeletal muscle development:insights from chicken studies

Skeletal muscle development is a complex multi-process trait regulated by various genetic factors.The chicken embryo is an ideal model system for studying skeletal muscle development. However, only a small proportion of the genetic factors affecting skeletal muscle development have been identified in chicken. The aim of this review is to summarize recent knowledge about the genetic factors involved in the regulation of skeletal muscle development in the chicken, such as gene polymorphisms, epigenetic modification, noncoding RNAs and transcription factors, which can influence skeletal muscle development at the genome, epigenome,transcriptome and proteome levels. Research on the regulation of skeletal muscle development in chicken is not yet comprehensive and most of the candidate genes and single nucleotide polymorphisms related to chicken muscle growth remain to be verified in experimental studies. In addition, the data derived from transcriptome sequencing and genome-wide association studies still require further investigation and analysis and comprehensive studies on the regulation of chicken skeletal muscle development will continue as a major research focus.

Function and regulation of muscle stem cells in skeletal muscle development and regeneration:a narrative review

Skeletal muscle plays an essential role in generating the mechanical force necessary to support the movement of our body and daily exercise. Compared with cardiac and smooth muscle, in mammals, skeletal muscle exhibits remarkable regenerative capacity in response to damage. Muscle stem cells, also known as satellite cells, directly contribute to regeneration. Here, we review primary and secondary myogenesis processes with a focus on muscle stem cells, as well as the function and regulation of muscle stem cells in adult muscle regeneration in mammals.

Effect of Botubinum toxin type A injection into the masseter muscle on mandibular development in rats

Objective To investigate the effect of Botulinum toxin type A(Botox)injection into the masseter muscle on mandibular development in rats.Methods 1228-day-old Wistar rats were divided into two groups as Botox group(n=6)and control group(n=6)

3D genome organization and its study in livestock breeding

Eukaryotic genomes are hierarchically packaged into cell nucleus,affecting gene regulation.The genome is organized into multiscale structural units,including chromosome territories,compartments,topologically associating domains(TADs),and DNA loops.The identification of these hierarchical structures has benefited from the development of experimental approaches,such as 3C-based methods(Hi-C,ChIA-PET,etc.),imaging tools(2D-FISH,3D-FISH,Cryo-FISH,etc.)and ligation-free methods(GAM,SPRITE,etc.).In recent two decades,numerous studies have shown that the 3D organization of genome plays essential roles in multiple cellular processes via various mechanisms,such as regulating enhancer activity and promoter-enhancer interactions.However,there are relatively few studies about the 3D genome in livestock species.Therefore,studies for exploring the function of 3D genomes in livestock are urgently needed to provide a more comprehensive understanding of potential relationships between the genome and production traits.In this review,we summarize the recent advances of 3D genomics and its biological functions in human and mouse studies,drawing inspiration to explore the 3D genomics of livestock species.We then mainly focus on the biological functions of 3D genome organization in muscle development and its implications in animal breeding.

BTG1 as a New Candidate Gene for Muscle Growth in Pigs: Cloning,Expression and Association Analysis

BTG1 （B-cell Translocation Gene 1） , a member of the BTG / TOB （Transducer of ErbB-2） family of anti-proliferation factors,has been proven to have an unfavorable effect on muscle fiber growth in several species. The porcine BTG1 gene was cloned and its 5＇ flanking promoter region sequence, and characterized the expression patterns in different tissues of adult pigs and in fetal skeletal muscle at different developmental stages in two breeds. The tissue distribution pattern analyses revealed that the mRNA of porcine BTG1 was ubiquitously expressed in the six tissues of both Landrace and Tongcheng pigs. Real-time quantitative reverse transcriptase-PCR results showed that BTG1 mRNA expression levels were significantly different among the three fetal ages in Tongcheng pigs,while no significant differences were found among the three ages in Landrace pigs. Furthermore,the expression of BTG1 in Landrace pigs was significantly lower than in Tongcheng pigs at all three ages. The temporal expression profiles of the BTG1 gene in mouse myoblast C 2 C 12 cells were shown to be consistent with those of the myogenin gene. A single nucleotide polymorphism （SNP） ,g. 281C 〉 T,was identified in the 3＇UTR and allele frequencies were detected in seven pig breed populations. Significant associations were found between the g. 281C 〉 T polymorphism and growth and meat quality traits. Our results indicate that the porcine BTG1 gene could play a potential role in markerassisted selection and as such may be a gene of economic importance.

Targeted myostatin loss-of-function mutation increases type Ⅱ muscle fibers in Meishan pigs

Myostatin(MSTN) is a negative regulator of skeletal muscle growth and development. The skeletal muscle in MSTN^(-/-)mice is significantly hypertrophied, with muscle fiber type II increasing significantly while muscle fiber type I decreasing.However, it is still not clear how the skeletal muscle types change in MSTN^(-/-)pigs, and how the mechanism for MSTN regulates fiber types, especially in large animals like pigs. This study conducted a comprehensive analysis of the composition of skeletal muscle fibers in MSTN^(-/-)pigs produced in our laboratory. It was observed that, compared with wild-type(WT) pigs, both the total mass of skeletal muscle and type IIb muscle fibers increased significantly(P<0.01),while the type I and type IIa muscle fibers decreased significantly(P<0.01), in MSTN^(-/-)Meishan pigs. In addition, to explore the influence of MSTN on muscle fiber type and its regulation mechanism in the embryonic stage, this study selected a few genes(Myf5, Mef2 d, MyoD and Six1) associated with muscle fiber type and validated their expression by quantitative RT-PCR. Herein, it was found that Myh7, Myh2, Myh4 and Myh1 can be detected in the skeletal muscle of pigs at 65 days of gestation(dg). Compared with WT pigs, in MSTN^(-/-)Meishan pigs, Myh7 decreased significantly(P<0.01), while Myh4(P<0.001) and Myh1(P<0.05) increased significantly. Meanwhile, the increased expression of Myf5(P<0.05), Mef2 d(P<0.01) and Six1(P<0.05) in MSTN^(-/-)Meishan pigs suggested that MSTN should regulate the directional development of muscle fiber types in the early stage of embryonic development. Thus, at the embryonic stage, the type II muscle fibers began to increase in MSTN^(-/-)pigs. These results can provide valuable information not only for pig meat quality improvement, but also for the study of human skeletal muscle development and disease treatment.

Integration of genome-wide association study and selection signatures reveals genetic determinants for skeletal muscle production traits in an F2 chicken population

Improving the production of broiler chicken meat has been a goal of broiler breeding programs worldwide for many years. However, the genetic architectures of skeletal muscle production traits in chickens have not yet been fully elucidated. In the present study, a total of 519 F_(2) birds, derived from a cross of Arbor Acres broiler and Baier layer, were re-sequenced(26 F_(0) individuals were re-sequenced at a 10-fold depth;519 F_(2) individuals were re-sequenced at a 3-fold depth) and the coupling of genome-wide association study(GWAS) and selection signatures(FST(fixation index) and θπ(nucleotide diversity)) was carried out to pinpoint the associated loci and genes that contribute to pectoral muscle weight(PMW) and thigh muscle weight(TMW). A total of 7 890 258 single nucleotide polymorphisms(SNPs) remained to be analyzed after quality control and imputation. The integration of GWAS and selection signature analyses revealed that genetic determinants responsible for skeletal muscle production traits were mainly localized on chromosomes 1(168.95–172.43 Mb) and 4(74.37–75.23 Mb). A total of 17 positional candidate genes(PCGs)(LRCH1, CDADC1, CAB39 L, LOC112531568, LOC112531569, FAM124 A, FOXO1, NBEA, GPALPP1, RUBCNL, ARL11, KPNA3, LHFP, GBA3, LOC112532426, KCNIP4, and SLIT2) were identified in these regions. In particular, KPNA3 and FOXO1 were the most promising candidates for meat production in chickens. These findings will help enhance our understanding of the genetic architecture of chicken muscle production traits, and the significant SNPs identified could be promising candidates for integration into practical breeding programs such as genome-wide selection(GS) to improve the meat yield of chickens.

Characterization of DYRK2(dual-specificity tyrosine-phosphorylation-regulated kinase 2) from Zebrafish(Dario rerio)

Proteins of the DYRK(dual-specificity tyrosine-phosphorylation-regulated kinase) family are characterized by the presence of a conserved kinase domain and N-terminal DH box.DYRK2 is involved in regulating key developmental and cellular processes,such as neurogenesis,cell proliferation,cytokinesis,and cellular differentiation.Herein,we report that the ortholog of DYRK2 found in zebrafish shares about 70% identity with that of human,mouse,and chick.RT-PCR showed that DYRK2 is expressed maternally and zygotically.In-situ hybridization results show that DYRK2 is expressed in somite cells that will develop into muscles.Our results provide preliminary evidence for investigating the in-vivo function of DYRK2 in zebrafish muscle development.

Vitamin A supplementation downregulates ADH1C and ALDH1A1 mRNA expression in weaned beef calves

Our previous studies demonstrated that oral vitamin A supplementation during late-stage pregnancy and the neonatal stage enhances birth weight,growth performance,and mRNA expression related to muscle and preadipocyte development in beef cattle.The alcohol dehydrogenase 1C(ADH1C)c.-64T>C genotype also correlated with vitamin A concentration in beef production.This study aimed to investigate the effects of vitamin A supplementation on the muscle development and vitamin A metabolism in weaned beef calves with different ADH1C genotypes.Twenty male calves(90 d of age;initial BW:89.03 kg[SD 8.60])were stratified according to ADH1C genotype and vitamin A treatment(duration:3 months)and randomly assigned to 4 groups with a 22 factorial arrangement.Vitamin A treatments included the following:control(10,000 IU/kg of as-fed,a.TT type;b.TC type);treatment(40,000 IU/kg of as-fed,c.TT type;and d.TC type).Parameters including BW,FI,blood,longissimus dorsi muscle,and liver status during the experimental period were analyzed using the generalized linear model(GLM)procedure and Tukey's test by SAS 9.4 program.Serum vitamin A was significantly increased(P<0.05)in the vitamin A treatment group at 4 and 6 months of age.TT type calves showed higher serum vitamin A concentration(P<0.05)than the TC type calves.Serum triglyceride and non-esterified fatty acid(NEFA)levels increased(P<0.05)in the treatment group compared with the control at 6 months of age.However,BW,ADG and FI showed no differences between the groups.In addition,mRNA expression in longissimus dorsi muscle revealed upregulation of paired box 7(PAX7)(P<0.05)after the vitamin A treatment period based on biopsy results.Both ADH1C and aldehyde dehydrogenase(ALDH)1A1 mRNA expression was downregulated(P<0.01)by vitamin A supplementation.The TC type of ADH1C showed higher mRNA expression than the TT type.However,no effect was observed on adipogenic mRNA expression(preadipocyte factor-1[PREF-1],peroxisome proliferator-activated receptor gamma[PPARg],fatty acid binding protein 4[FABP4])in all groups.Our findings suggest that weaned calves treated with vitamin A may promote the storage of satellite cells by elevating PAX7 gene expression in the muscle.The TC type calves may show increased capacity for vitamin A metabolism,which can be used in genetically customizing feed management to maximize beef production in the calves.

Matrix attachment regions included in a bicistronic vector enhances and stabilizes follistatin gene expressions in both transgenic cells and transgenic mice

In the present study, follistatin(FST) gene expression vectors with either a bicistronic gene transfer cassette alone, or a bicistron gene cassette carrying a matrix attachment region(MAR) were constructed and transfected to bovine fetal fibroblasts. Evaluations of both the integration and expression of exogenous FST indicated that the p MAR-CAG-FST-IRES-Ac GFP1-poly A-MAR(pMAR-FST) vector had higher capacity to form monoclonal transgenic cells than the vector without MAR,though transient transfection and integration efficiency were similar with either construct. Remarkably, protein expression in transgenic cells with the p MAR-FST vector was significantly higher than that from the bicistronic vector. Exogenous FST was expressed in all of the p MARFST transgenic mice at F_0, F_1 and F_2. Total muscle growth in F_0 mice was significantly greater than in wild-type mice,with larger muscles in fore and hind limbs of transgenic mice. p MAR-FST transgenic mice were also found with more evenly distributed muscle bundles and thinner spaces between sarcolemma, which suggests a correlation between transgene expression-associated muscle development and the trend of muscle growth. In conclusion, a p MAR-FST vector, which excluded the resistant genes and frame structure, enhances and stabilizes FST gene expressions in both transfected cells and transgenic mice.