Evidence for multiple alleles effecting muscling and fatness at the ovine GDF8 locus

Insights into the influence of diet and genetics on feed efficiency and meat production in sheep

Feed costs and carcass yields affect the profitability and sustainability of sheep production. Therefore, it is crucial to select animals with a higher feed efficiency and high-quality meat production. This study focuses on the impact of dietary and genetic factors on production traits such as feed efficiency, carcass quality, and meat quality. Diets promote optimal sheep growth and development and provide sufficient protein can lead to higher-quality meat. However, establishing an optimized production system requires careful consideration and balance of dietary parameters. This includes ensuring adequate protein intake and feeding diets with higher intestinal absorption rates to enhance nutrient absorption in the gut. The study identifies specific genes, such as Callipyge, Calpastatin, and Myostatin, and the presence of causal mutations in these genes, as factors influencing animal growth rates, feed efficiency, and meat fatty acid profiles. Additionally, variants of other reported genes, including PIGY, UCP1, MEF2B, TNNC2, FABP4, SCD, FASN, ADCY8, ME1, CA1, GLIS1, IL1RAPL1, SOX5, SOX6, and IGF1, show potential as markers for sheep selection. A meta-analysis of reported heritability estimates reveals that residual feed intake (0.27 ± 0.07), hot carcass weight (0.26 ± 0.05), dressing percentage (0.23 ± 0.05), and intramuscular fat content (0.45 ± 0.04) are moderately to highly heritable traits. This suggests that these traits are less influenced by environmental factors and could be improved through genetic selection. Additionally, positive genetic correlations exist between body weight and hot carcass weight (0.91 ± 0.06), dressing percentage (0.35 ± 0.15), and shear force (0.27 ± 0.24), indicating that selecting for higher body weight could lead to favorable changes in carcass quality, and meat quality.

Comparison of the growth performance between pure Moghani sheep and crosses with Texel or Booroola sheep carrying major genes contributing to muscularity and prolificacy

This study aimed to compare growth performance between Moghani sheep and crossbred lambs resulting from crossbreeding between Moghani pure breed ewes and the lines of rams e.g., Texel Tamlet, Texel Dalzell, Booroola Merino, and Booroola Romney. The first visible phenotypic characteristic was the presence of lean tail in all F1 crossbred lambs, whereas Moghani pure sheep is a well-known large fat-tailed breed. Moreover, the first generation of backcross (BC1) lambs from mating four types of F1 crossbred rams with Moghani pure ewes revealed lean-tailed to short fat-tailed. Comparative results showed that the F1 crossbred lambs had significantly (p < 0.0001) greater birth weight (BW) than the Moghani pure breed lambs. Despite no significant differences observed between Moghani pure breed sheep and its F1 crossbred lambs for body weight at pre-weaning, but F1 crossbred lambs achieved significantly (p < 0.0001) greater body weight after weaning compared to Moghani sheep. The growth performance of BC1 lambs was outperformed than F1 crossbred and Moghani sheep. These results encourage the continuation of the Moghani sheep crossbreeding programs to improve overall lamb growth, particularly post-weaning and to benefit from a better reproductive efficiency by elimination or reduction of the fat tail.

NCAPG Regulates Myogenesis in Sheep, and SNPs Located in Its Putative Promoter Region Are Associated with Growth and Development Traits

Previously, NCAPG was identified as a candidate gene associated with sheep growth traits. This study aimed to investigate the direct role of NCAPG in regulating myogenesis in embryonic myoblast cells and to investigate the association between single-nucleotide polymorphisms (SNPs) in its promoter region and sheep growth traits. The function of NCAPG in myoblast proliferation and differentiation was detected after small interfering RNAs (siRNAs) knocked down the expression of NCAPG. Cell proliferation was detected using CCK-8 assay, EdU proliferation assay, and flow cytometry cell cycle analysis. Cell differentiation was detected via cell immunofluorescence and the quantification of myogenic regulatory factors (MRFs). SNPs in the promoter region were detected using Sanger sequencing and genotyped using the improved multiplex ligation detection reaction (iMLDR®) technique. As a result, a notable decrease (p < 0.01) in the percentage of EdU-positive cells in the siRNA-694-treated group was observed. A significant decrease (p < 0.01) in cell viability after treatment with siRNA-694 for 48 h and 72 h was detected using the CCK-8 method. The quantity of S-phase cells in the siRNA-694 treatment group was significantly decreased (p < 0.01). After interfering with NCAPG in myoblasts during induced differentiation, the relative expression levels of MRFs were markedly (p < 0.05 or p < 0.01) reduced compared with the control group on days 5-7. The myoblast differentiation in the siRNA-694 treatment group was obviously suppressed compared with the control group. SNP1, SNP2, SNP3, and SNP4 were significantly (p < 0.05) associated with all traits except body weight measured at birth and one month of age. SNP5 was significantly (p < 0.05) associated with body weight, body height, and body length in six-month-old sheep. In conclusion, interfering with NCAPG can inhibit the proliferation and differentiation of ovine embryonic myoblasts. SNPs in its promoter region can serve as potential useful markers for selecting sheep growth traits.

Effects of a myostatin mutation in Japanese quail (Coturnix japonica) on the physicochemical and histochemical characteristics of the pectoralis major muscle

The aim of this study was to compare the carcass, meat quality, and histochemical characteristics of pectoralis major (PM) muscle between wild type (WT) and myostatin (Mstn) homozygous mutant (HO) quail lines. The HO quail line exhibited significantly heavier body weight (HO vs. WT, 115.7 g vs. 106.2 g, approximately 110%) and PM muscle weight (HO vs. WT, 18.0 g vs. 15.2 g, approximately 120%) compared to the WT (p &lt; 0.001). However, the two groups had similar traits (pH, redness, yellowness, and drip loss) for meat quality, although slightly higher lightness and cooking loss were observed in the mutant quail (103% and 141%, respectively, p &lt; 0.05). For histochemical traits of PM muscle, Mstn mutant quail exhibited lower type IIA and higher type IIB percentage in the deep region than WT quail (p &lt; 0.05), indicating a fiber conversion from the type IIA to IIB. However, the two quail lines had comparable histochemical traits in the superficial region (p &gt; 0.05). These data suggest that Mstn mutation greatly increases muscle mass without significantly affecting meat quality.

A Genome-Wide Search for Candidate Genes of Meat Production in Jalgin Merino Considering Known Productivity Genes

In a group of Jalgin merino rams with no significant influence on the dispersion of the phenotypes of known productivity genes (MSTN, MEF2B, FABP4, etc.), a genome-wide search for associations of individual polymorphisms with intravital indicators of meat productivity was performed. Using the Ovine Infinium HD BeadChip 600K, 606,000 genome loci were evaluated. Twenty-three substitutions were found to be significantly associated with external measurements of the body and ultrasonic parameters. This made it possible to describe 14 candidate genes, the structural features of which can cause changes in animal phenotypes. No closely spaced genes were found for two substitutions. The identified polymorphisms were found in the exons, introns, and adjacent regions of the following genes and transcripts: CDCA2, ENSOARG00000014477, C4BPA, RIPOR2, ENSOARG00000007198, ENSOARG00000026965 (LincRNA), ENSOARG00000026436 (LincRNA), ENSOARG00000026782 (LincRNA), TENM3, RTL8A, MOSPD1, RTL8С, RIMS2, and P4HA3. The detected genes affect the metabolic pathways of cell differentiation and proliferation and are associated with the regulation of the immune system. This confirms their possible participation in the formation of the phenotypes of productivity parameters in animals and indicates the need for further study of the structure of candidate genes in order to identify their internal polymorphisms.

The comparative results of myostatin introgression from donor Texel to recipient Ramlıç sheep with the aspects of growth, pre-, and post-slaughter carcass traits in the second backcross generation

The aim of the study was to evaluate the growth, body and ultrasonic measurements and some carcass traits of purebred Ramlıç, Texel and crossbred (87.5 % Ramlıç and 12.5 % Texel) lambs in a marker-assisted introgression (MAI) project. The effects of some environmental factors such as genotype, sex, birth type, dam age, weaning age, and birth weight on growth, ultrasound measurements, and carcass traits were significant (P<0.05). There were no significant differences between pure Ramlıç and its myostatin carrier (+/-) and non-carrier (-/-) second backcrosses (BC2) for birth weight, daily live weight gain, and weaning weight. The BC2 genotype (+/-) was statistically caught up with pure Ramlıç for wither height, body length, and rump width. Differences in the longissimus muscle depth indicated that the BC2 (+/-) genotypes tended to be better for both pure Ramlıç and Texel lambs. Texel lambs were superior to Ramlıç in the aspect of some carcass characteristics such as leg length, cold right-half carcass weight, foreleg weight in the left-half carcass, and muscle weight in the left leg. BC2 (+/-) lambs were in the middle of both breeds for the traits. BC2 lambs carrying myostatin did not vary from Ramlıç morphologically. The new type of Ramlıç was also closer to Texel in the aspect of carcass characteristics. In this connection, improvement of indigenous breeds could be achieved by MAI without changing the essential characteristics. For the summary, please visit http://www.mustafatekerli.com (last access: 14 June 2022).

Myostatin: Basic biology to clinical application

Myostatin is a member of the transforming growth factor (TGF)-β superfamily. It is expressed by animal and human skeletal muscle cells where it limits muscle growth and promotes protein breakdown. Its effects are influenced by complex mechanisms including transcriptional and epigenetic regulation and modulation by extracellular binding proteins. Due to its actions in promoting muscle atrophy and cachexia, myostatin has been investigated as a promising therapeutic target to counteract muscle mass loss in experimental models and patients affected by different muscle-wasting conditions. Moreover, growing evidence indicates that myostatin, beyond to regulate skeletal muscle growth, may have a role in many physiologic and pathologic processes, such as obesity, insulin resistance, cardiovascular and chronic kidney disease. In this chapter, we review myostatin biology, including intracellular and extracellular regulatory pathways, and the role of myostatin in modulating physiologic processes, such as muscle growth and aging. Moreover, we discuss the most relevant experimental and clinical evidence supporting the extra-muscle effects of myostatin. Finally, we consider the main strategies developed and tested to inhibit myostatin in clinical trials and discuss the limits and future perspectives of the research on myostatin.

Identification of polymorphisms in the MSTN and ADRB3 genes associated with growth and ultrasound carcass traits in Kajli sheep

The aim of this investigation was to find single nucleotide polymorphisms (SNPs) in the myostatin (MSTN) and the beta-3 adrenergic receptor (ADRB3) genes associated with growth and ultrasound carcass traits in Kajli sheep. The five growth traits were birth weight (BWT-EBV), 120-day weight (120DWT-EBV), 180-day weight (180DWT-EBV), 270-day weight (270DWT-EBV), and 365-day weight (365DWT-EBV). The three ultrasound carcass traits were width (WLD) and depth of longissimus dorsi (DLD) and back fat thickness (BFT). The analysis of the MSTN sequence revealed one non-synonymous substitution (c.197T > A) in exon 1, one single nucleotide substitution (c.373 + 18G > T) in intron 1, and one synonymous substitution (c.861T > A) in exon 3. However, there were four single nucleotide synonymous substitutions (c.130C > T, c.294C > G, c.579G > T, and c.654C > G) in exon 1 of the ADRB3 gene. All the SNPs in the MSTN gene, except for c.373 + 18G > T, were in Hardy-Weinberg Equilibrium (HWE). Conversely, none of the SNPs found in ADRB3 were in HWE. Two of the MSTN SNPs (c.197T > A and c.373 + 18G > T) had significant associations with all evaluated growth and ultrasound carcass traits. The SNPs c.130C > T and c.294C > G in ADRB3 were significantly associated with 180DWT-EBV. Collectively, these findings indicate that several SNPs in the studied genes were significantly related to growth and carcass traits in Kajli sheep.

Genetic variations in the Myostatin gene affecting growth traits in sheep

Background and Aim

Sheep productivity in developing countries is crucial, as this animal is an essential source of meat and wool. Myostatin (MSTN) plays an important role in the regulation of muscle mass through the regulation of muscle growth, differentiation, and regeneration. The present study sought to investigate genetic variation in the first intron of the MSTN gene and the association of variants with growth traits in major sheep breeds in Egypt (Barki, Ossimi, and Rahmani) and Saudi Arabia (Najdi) using polymerase chain reaction (PCR) and sequencing.

Materials and Methods

Blood samples were collected, and DNA was extracted from 75 animals. A 386 bp fragment in the first intron of the MSTN gene was amplified using PCR. Polymorphic sites were detected using direct sequencing and then correlated with growth traits using a general linear model.

Results

Sequence analysis of the first intron of MSTN gene identified six single-nucleotide polymorphisms (SNPs) in the studied breeds. Four mutual SNPs were determined: c.18 G>T, c.241 T>C, c.243 G>A, and c.259 G>T. In addition, two SNPs c.159 A>T and c.173 T>G were monomorphic (AA and TT, respectively) in the Ossimi, Rahmani, and Najdi breeds and polymorphic in the Barki breed. The association analysis revealed that the c.18 G>T and c.241 C>T significantly associated (p<0.05) with birth weight and average daily weight gain, respectively.

Conclusion

Our results strongly support MSTN as a candidate gene for marker-assisted selection in sheep breeding programs. Furthermore, the identified variants may be considered as putative markers to improve growth traits in sheep.

Key Genes Regulating Skeletal Muscle Development and Growth in Farm Animals

Simple Summary

Skeletal muscle mass is an important economic trait, and muscle development and growth is a crucial factor to supply enough meat for human consumption. Thus, understanding (candidate) genes regulating skeletal muscle development is crucial for understanding molecular genetic regulation of muscle growth and can be benefit the meat industry toward the goal of increasing meat yields. During the past years, significant progress has been made for understanding these mechanisms, and thus, we decided to write a comprehensive review covering regulators and (candidate) genes crucial for muscle development and growth in farm animals. Detection of these genes and factors increases our understanding of muscle growth and development and is a great help for breeders to satisfy demands for meat production on a global scale.

Abstract

Farm-animal species play crucial roles in satisfying demands for meat on a global scale, and they are genetically being developed to enhance the efficiency of meat production. In particular, one of the important breeders’ aims is to increase skeletal muscle growth in farm animals. The enhancement of muscle development and growth is crucial to meet consumers’ demands regarding meat quality. Fetal skeletal muscle development involves myogenesis (with myoblast proliferation, differentiation, and fusion), fibrogenesis, and adipogenesis. Typically, myogenesis is regulated by a convoluted network of intrinsic and extrinsic factors monitored by myogenic regulatory factor genes in two or three phases, as well as genes that code for kinases. Marker-assisted selection relies on candidate genes related positively or negatively to muscle development and can be a strong supplement to classical selection strategies in farm animals. This comprehensive review covers important (candidate) genes that regulate muscle development and growth in farm animals (cattle, sheep, chicken, and pig). The identification of these genes is an important step toward the goal of increasing meat yields and improves meat quality.

Association of a polymorphism in exon 3 of the IGF1R gene with growth, body size, slaughter and meat quality traits in Colored Polish Merino sheep

This study aimed to genotype the polymorphism (c.654G > A) in the exon 3 of the insulin-like growth factor 1 receptor gene (IGF1R) and to analyze its association with growth, body size, slaughter and meat quality traits in Colored Polish Merino sheep. In total, 67 traits were analyzed. The IGF1R polymorphism was genotyped using the polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) method. The MIXED procedure of the SAS software was used to assess the genotypic effects of the polymorphism (c.654G > A) on production traits of interest. The IGF1R c.654G > A genotypes were found to have a significant effect on the average daily gain between the 56th and 78th day of life, cold carcass, leg part, leg cut, fore shank, and kidney weights, as well as eye of loin depth, intramuscular fat content, and water-holding capacity of meat. The results suggest that the studied polymorphism may provide useful information for marker-assisted selection for increased meat performance in Colored Polish Merino sheep.

SNP screening of the MSTN gene and correlation analysis between genetic polymorphisms and growth traits in Dazu black goat

The aim of this study was to detect SNPs in myostatin (MSTN) gene of four goat breeds, and analyze the correlation of these markers on body measurement traits in the Dazu black goat breed. In total, twenty polymorphic sites were found in one hundred forty-eight individuals, and all SNPs were distributed in introns 1 and 2, except g. 425 C > T, which was found in the regulatory region. Three SNPs (g. 2732 C > T, g. 2752 G > A and g. 4552 A > C) were polymorphic in all four breeds. None of the tag SNPs (g. 425 C > T, g. 1583 A > G, 2732 C > T, g. 4552 A > C and g. 5167 C > T) were significantly correlated with body measurement traits (p > 0.05) in the Dazu black goat. However, individuals with genotype combination 3 (GtC 3) of tag SNPs had higher birth weight and weaning weight than individuals with the other genotype combinations (p < 0.05). Moreover, the genotype combination 4 (GtC 4) was significantly associated with body length and height at the age of 2 months (p < 0.05), and genotype combination 13 (GtC 13) was significantly correlated with body height at 6 months (p < 0.05). Briefly, the combined tag SNP markers might be useful for goat marker-associated selective breeding.

Variants in myostatin and MyoD family genes are associated with meat quality traits in Santa Inês sheep

Myostatin and MyoD family genes play vital roles in myogenesis and this study aimed to identify association of variants in MyoD1, MyoG, MyF5, MyF6, and MSTN genes with meat traits in Santa Inês sheep. A dataset with 44 variants and records of seven meat traits in 192 lambs (pH0, pH24, a*, b*, L*, tenderness assessed by shear force, and water-holding capacity) was used. Single-locus and haplotype association analyses were performed, and the significance threshold was established according to Bonferroni's method. Single-locus analysis revealed two associations at a Bonferroni level, where the variant c.935-185C > G in MyoD1 had an additive effect (-4.31 ± 1.08 N) on tenderness, while the variant c.464 + 185G > A in MyoG had an additive effect (-2.86 ± 0.64) on a*. Additionally, the haplotype replacement GT>AC in MSTN was associated with pH0 (1.26 ± 0.31), pH24 (1.07 ± 0.27), a* (-1.40 ± 0.51), and tenderness (3.83 ± 1.22 N), while the replacement GT > AG in MyoD1 was associated with pH0 (1.43 ± 0.26), pH24 (1.25 ± 0.22), b* (-1.06 ± 0.39), and tenderness (-4.13 ± 1.16 N). Our results have demonstrated that some variants in MyoG, MyF6, MyoD1, and MSTN can be associated with physicochemical meat traits in Santa Inês sheep.

Association between polymorphisms of Myf5, MSTN and CAST genes and fattening performance in Brown Swiss and Holstein cattle breeds

This study determined the association between Myf5, CAST and MSTN genes and fattening performance traits in 228 (Holstein = 103 and Brown = 125) cattle breeds. Classification and regression tree (CART) was used to determine association between genes and fattening performance. The allele frequencies of Holstein cattle in terms of Myf5, CAST and MSTN genes were A:0.30, B:0.70; A:0.43, G:0.56; A:0.97, B:0.03, respectively, whereas in the Brown Swiss cattle were A:0.36, B:0.64; A:0.65, G:0.34; A:0.88, B:0.12 respectively. The Myf5, CAST, and MSTN genes were found to be in the Hardy-Weinberg equilibrium (p > 0.05) in both of the cattle breeds. As a result, the association between Myf5, CAST and MSTN genes and fattening performance traits were found to be significant according to CART analysis.

Effects of Intronic SNPs in the Myostatin Gene on Growth and Carcass Traits in Colored Polish Merino Sheep

Myostatin acts as a negative regulator of muscle growth; therefore, its role is important with regard to animal growth and meat production. This study was undertaken with the objective to detect polymorphisms in the first intron and c.*1232 position of the MSTN gene and to analyze effects of the detected alleles/genotypes on growth and carcass traits in Colored Polish Merino sheep. In total, 23 traits were analyzed, i.e., seven describing lamb growth and 16 carcass traits. Single nucleotide polymorphisms (SNPs) in the first intron and the c.*1232 position were identified using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and PCR-restriction fragment length polymorphism (PCR-RFLP) methods, respectively. The MIXED procedure of the SAS software package was used to analyze allelic and genotypic effects of the MSTN gene on growth and carcass traits. Polymorphisms were only detected in the first intron of the MSTN gene. All investigated sheep were monomorphic G in the c.*1232 position. The MSTN genotype was found to have significant effect on body weight at 2nd day of life (BW2) and loin and fore shank weights. Significant allelic effects were detected with respect to BW2, scrag, leg, fore, and hind shank weights. These results suggest that polymorphisms in the first intron of the MSTN gene are relevant with respect to several carcass traits and BW2 in Colored Polish Merino sheep.

Gene Expression and Fatty Acid Profiling in Longissimus thoracis Muscle, Subcutaneous Fat, and Liver of Light Lambs in Response to Concentrate or Alfalfa Grazing

A better understanding of gene expression and metabolic pathways in response to a feeding system is critical for identifying key physiological processes and genes associated with polyunsaturated fatty acid (PUFA) content in lamb meat. The main objective of this study was to investigate transcriptional changes in L. thoracis (LT) muscle, liver, and subcutaneous fat (SF) of lambs that grazed alfalfa (ALF) and concentrate-fed (CON) slaughtered at 23 kg and using the Affymetrix Ovine Gene 1.1 ST whole-genome array. The study also evaluated the relationship between meat traits in LT muscle, including color, pigments and lipid oxidation during 7 days of display, α-tocopherol content, intramuscular fat (IMF) content and the fatty acid (FA) profile. Lambs that grazed on alfalfa had a greater α-tocopherol concentration in plasma than CON lambs (P < 0.05). The treatment did not affect the IMF content, meat color or pigments (P > 0.05). Grazing increased the α-tocopherol content (P < 0.001) and decreased lipid oxidation on day 7 of display (P < 0.05) in LT muscle. The ALF group contained a greater amount of conjugated linoleic acid (CLA), C18:3 n−3, C20:5 n−3, C22:5 n−3, and C22:6 n−3 than did the CON group (P < 0.05). We identified 41, 96 and four genes differentially expressed in LT muscle, liver, and subcutaneous fat, respectively. The most enriched biological processes in LT muscle were skeletal muscle tissue development, being the genes related to catabolic and lipid processes downregulated, except for CPT1B, which was upregulated in the ALF lambs. Animals grazing alfalfa had lower expression of desaturase enzymes in the liver (FADS1 and FADS2), which regulate unsaturation of fatty acids and are directly involved in the metabolism of n−3 PUFA series. The results found in the current study showed that ingesting diets richer in n−3 PUFA might have negative effects on the de novo synthesis of n−3 PUFA by downregulating the FADS1 and FADS2 expression. However, feeding diets poorer in n−3 PUFA can promote fatty acid desaturation, which makes these two genes attractive candidates for altering the content of PUFAs in meat.

Genotypic and allelic effects of the myostatin gene (MSTN) on carcass, meat quality, and biometric traits in Colored Polish Merino sheep

The aim of this study was to identify polymorphisms in the first intron and c.*1232G>A position of the MSTN gene and analyze associations between the detected alleles/genotypes and carcass, meat quality, and biometric traits in Colored Polish Merino sheep. We analyzed 44 traits using the MIXED procedure of the SAS software. Five alleles (MSTN-A, MSTN-B, MSTN-C, MSTN-E and MSTN-E1) were detected. Significant genotypic effects were detected with regard to chest depth (live lamb) and fat depth over ribs, drip loss, subjective meat flavor and color, whereas significant allelic effects were found for chest depth (live lamb), pre-slaughter weight, hot carcass weight, cold carcass dressing out, leg depth (carcass), eye of loin width and area, intramuscular fat (IMF) content, water-holding capacity, and subjective meat tenderness, flavor and color. The results suggest MSTN gene polymorphisms may be considered a genetic marker of carcass quality, meat quality, and biometric traits in sheep.

Effects and interactions of myostatin and callipyge mutations: I. Growth and carcass traits

Objectives were to document effects of the Texel myostatin mutation (MSTN) on growth and carcass traits and also test whether or not interactions with the callipyge mutation (CLPG) could be detected. Twelve rams heterozygous at both loci on the two different chromosomes were mated to 215 terminal-sire type composite crossbred ewes genotyped as non-carriers for both loci. A total of 365 lambs were born, 362 of those were genotyped and 236 lambs contributed carcass data to estimate effects and interactions among the four genotype combinations produced. The four genotype combinations were defined as follows: ++/++ for wild-type at both loci; ++/C+ for wild-type at MSTN and heterozygous at CLPG; M+/++ for heterozygous at MSTN and wild-type at CLPG; and M+/C+ for heterozygous at both loci. The two independently segregating sire-derived alleles represent different breed-of-origin contrasts at each locus (Texel vs. composite origin for MSTN and Dorset vs. Texel origin for CLPG). Birth weight was recorded on all lambs, and subsequent body weights were adjusted to 56 (weaning), 70, and 140 d of age. Within sire-sex-genotype subgroups, naturally reared lambs were assigned to one of eight slaughter groups accounting for variation in birth date. Lambs were serially slaughtered at weekly intervals, 30 lambs per group, from roughly 26 to 33 wk of age. In addition to standard carcass traits, subjective leg scores were assigned and widths of carcasses were measured at the widest points of the shoulder and rump. Differences in birth weight were detected (P < 0.01) for the combination of the two loci and birth type, with single-born differences among genotypes exceeding differences among twin born progeny. Those interaction differences among genotypes were not as important at weaning (P = 0.36). Impact on growth rate differences among the genotypes during the post-weaning period were variable and dependent on sex of the lamb (P < 0.01). A synergistic interaction between MSTN and CLPG was observed for leg muscling scores (P < 0.05) but no other measures of carcass shape were affected. One copy of MSTN had a more modest impact on fat deposition and muscle conformation than did CLPG and did not interact (all values P > 0.20). Although some non-additive interactions that vary by trait and sex were detected, in general the data are consistent with the two mutations acting on muscle growth through independent pathways.

Tetra-primer ARMS-PCR assay for genotyping SNPs in ovine GDF8 gene associated with mutton traits in sheep

Our study indicates the effects of genotypes on paunch girth. The results need to be verified on a larger number of samples. Nonetheless, our study emphasizes the efficacy of the T-ARMS PCR assay for increasing throughput. These assays will enable rapid and cost effective screening of large number of samples for association studies. The generated information can then be utilized in formulation of breeding policies for Indian sheep.

Progesterone signalling in broiler skeletal muscle is associated with divergent feed efficiency

Background

We contrast the pectoralis muscle transcriptomes of broilers selected from within a single genetic line expressing divergent feed efficiency (FE) in an effort to improve our understanding of the mechanistic basis of FE.

Results

Application of a virtual muscle model to gene expression data pointed to a coordinated reduction in slow twitch muscle isoforms of the contractile apparatus (MYH15, TPM3, MYOZ2, TNNI1, MYL2, MYOM3, CSRP3, TNNT2), consistent with diminishment in associated slow machinery (myoglobin and phospholamban) in the high FE animals. These data are in line with the repeated transition from red slow to white fast muscle fibres observed in agricultural species selected on mass and FE. Surprisingly, we found that the expression of 699 genes encoding the broiler mitoproteome is modestly–but significantly–biased towards the high FE group, suggesting a slightly elevated mitochondrial content. This is contrary to expectation based on the slow muscle isoform data and theoretical physiological capacity arguments. Reassuringly, the extreme 40 most DE genes can successfully cluster the 12 individuals into the appropriate FE treatment group. Functional groups contained in this DE gene list include metabolic proteins (including opposing patterns of CA3 and CA4), mitochondrial proteins (CKMT1A), oxidative status (SEPP1, HIG2A) and cholesterol homeostasis (APOA1, INSIG1). We applied a differential network method (Regulatory Impact Factors) whose aim is to use patterns of differential co-expression to detect regulatory molecules transcriptionally rewired between the groups. This analysis clearly points to alterations in progesterone signalling (via the receptor PGR) as the major driver. We show the progesterone receptor localises to the mitochondria in a quail muscle cell line.

Conclusions

Progesterone is sometimes used in the cattle industry in exogenous hormone mixes that lead to a ~20% increase in FE. Because the progesterone receptor can localise to avian mitochondria, our data continue to point to muscle mitochondrial metabolism as an important component of the phenotypic expression of variation in broiler FE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0396-2) contains supplementary material, which is available to authorized users.

Genetic and Nutritional Factors Determining the Production and Quality of Sheep Meat – A Review

In the last 20 years, the importance of sheep and especially lamb meat as the main product of the sheep industry in European conditions increased noticeably. In the same period, people’s interest in food quality grew. This contributed to a significant intensification of research to improve the meat production and quality traits in sheep. The aim of the research performed mainly focuses on the effects of nutrition, the environmental and genetic factors on the value of fattening, slaughter and meat quality characteristics. Much of the research concentrates on determining the fatty acid profile of intramuscular fat, which is important for sensory traits and dietetic value of lamb. Modulation of healthy qualities of lamb is aimed, inter alia, to modify the fatty acid profile, in particular to maintain the proper ratio of polyunsaturated (PUFA ) to saturated fatty acids (SFA). It is also desirable to increase the content of omega-3 fatty acids and conjugated linoleic acid (CLA). Furthermore, it has been proven that changes in the expression of genes involved in lipid metabolism are associated with the change in lipid profile in skeletal muscle. The aim of this review was to summarize the information currently available about the influence of genetic and nutritional factors on meat production and quality traits in different sheep breeds.

Structural and Dynamic Characterization of the C313Y Mutation in Myostatin Dimeric Protein, Responsible for the "Double Muscle" Phenotype in Piedmontese Cattle

The knowledge of the molecular effects of the C313Y mutation, responsible for the “double muscle” phenotype in Piedmontese cattle, can help understanding the actual mechanism of phenotype determination and paves the route for a better modulation of the positive effects of this economic important phenotype in the beef industry, while minimizing the negative side effects, now inevitably intersected. The structure and dynamic behavior of the active dimeric form of Myostatin in cattle was analyzed by means of three state-of-the-art Molecular Dynamics simulations, 200-ns long, of wild-type and C313Y mutants. Our results highlight a role for the conserved Arg333 in establishing a network of short and long range interactions between the two monomers in the wild-type protein that is destroyed upon the C313Y mutation even in a single monomer. Furthermore, the native protein shows an asymmetry in residue fluctuation that is absent in the double monomer mutant. Time window analysis on further 200-ns of simulation demonstrates that this is a characteristic behavior of the protein, likely dependent on long range communications between monomers. The same behavior, in fact, has already been observed in other mutated dimers. Finally, the mutation does not produce alterations in the secondary structure elements that compose the characteristic TGF-β cystine-knot motif.

Post-mortem stability of RNA in skeletal muscle and adipose tissue and the tissue-specific expression of myostatin, perilipin and associated factors in the horse

Obesity, a major concern for equine welfare, is highly prevalent in the leisure horse population. Skeletal-muscle and adipose tissues are important determinants of maintenance energy requirements. The myostatin and perilipin pathways play key roles in the regulation of muscle mass and lipolysis respectively and have both been associated with obesity predisposition in other mammalian species. High quality samples, suitable for molecular biology, are an essential prerequisite for detailed investigations of gene and protein expression. Hence, this study has evaluated a) the post-mortem stability of RNA extracted from skeletal-muscle and adipose-tissues collected under commercial conditions and b) the tissue-specific presence of myostatin, the moystatin receptor (activin receptor IIB, ActRIIB), follistatin and perilipin, genes and proteins across a range of equine tissues. Objectives were addressed using tissues from 7 Thoroughbred horses presented for slaughter at a commercial abattoir; a) samples were collected at 7 time-points from Masseter muscle and perirenal adipose from 5 minutes to 6 hours post-mortem. Extracted RN was appraised by Optical Density analysis and agarose-gel electrophoresis. b) Quantitative real time PCR and Western Blotting were used to evaluate gene and protein expression in anatomically-defined samples collected from 17 tissues (6 organs, 4 skeletal muscles and 7 discrete adipose depots). The results indicate that, under the present collection conditions, intact, good quality RNA could be extracted from skeletal-muscle for up to 2 hours post-mortem. However, RNA from adipose tissue may be more susceptible to degradation/contamination and samples should be collected no later than 30 minutes post-mortem. The data also show that myostatin and ActRIIB genes and proteins were almost exclusively expressed in skeletal muscle. The follistatin gene showed a more diverse gene expression profile, with expression evident in several organs, adipose tissue depots and skeletal muscles. Perilipin gene and protein were almost exclusively expressed by adipose tissue.

Application of myostatin in sheep breeding programs: A review

Plasma membrane H⁺-ATPase is a major integral membrane protein with a role in various physiological processes including abiotic stress response. To study the effect of NaCl on the expression pattern of a gene encoding the plasma membrane H⁺-ATPase, an experiment was carried out in a completely random design with three replications. A pair of specific primers was designed based on the sequence of the gene encoding plasma membrane H⁺-ATPase in Aeluropus littoralis to amplify a 259 bp fragment from the target gene by PCR. A gene encoding actin was used as reference gene to normalize the expression level of the target gene. A pair of specific primers was designed to amplify a 157 bp fragment from the actin gene by PCR. Plants were treated with different concentrations of NaCl, 0, 50, 100, 150, 200, 250, 500 and 1000 mM, for two days. Our results showed that the expression level of the plasma membrane H⁺-ATPase gene increased dramatically at 500 mM and then decreased with increasing concentrations of NaCl. The results also indicated that the leaves of plants, were treated with high concentrations of NaCl changed morphologically, but those grown under low concentrations of NaCl as well as the control plants did not show morphological changes in their leaves. Our results suggest a relation between morphological changes of treated plants and the expression level of the plasma membrane H⁺-ATPase gene in Aeluropus littoralis.

The effects of the myostatin g+6723G>A mutation on carcass and meat quality of lamb

This study evaluated the effects of the myostatin g+6723G>A mutation on carcass and meat quality traits of lamb (AA: n=5; AG: n=8; GG: n=9). Dressing percentage was positively affected by the mutation with homozygotes for the mutation having the highest yield. Regarding carcass composition, there was a significant increase in the proportional weights of the loin and hindquarter muscles. Objective meat quality traits of the M. longissimus lumborum (LL) and M. semimembranosus (SM) were not significantly affected. For the SM, toughness (shear force and compression) tended to be lowest for homozygotes for the mutation. The myostatin g+6723G>A mutation did not affect sensory meat quality traits of grilled steaks for the LL, but resulted in a significant improvement in eating quality for the SM. Given the number of animals in this study, the robustness of the outcome of this study with regard to the effects on meat quality and its causes requires further investigation.

Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires in an extensive rangeland production system: IV. Postfabrication carcass component weights

Postfabrication carcass component weights of 517 crossbred wether lambs were analyzed to evaluate 4 terminal-sire breeds. Wethers were produced over 3 yr from single-sire matings of 22 Columbia, 22 USMARC-Composite (Composite), 21 Suffolk, and 17 Texel rams to adult Rambouillet ewes. Lambs were reared to weaning in an extensive western rangeland production system and finished in a feedlot on a high-energy finishing diet. When wethers reached a mean BW of 54.4, 61.2, or 68.0 kg, they were transported to The Ohio State University abattoir for harvest. After refrigeration for approximately 24 h, chilled carcass weight (CCW) was measured, carcasses were fabricated according to Style A of Institutional Meat Purchase Specifications, and postfabrication weights were recorded. At comparable numbers of days on feed, Suffolk-sired lambs had heavier (P < 0.04) neck, breast, shoulder, foreshank, rack, loin, leg, sirloin, roast-ready rack, trimmed loin, and boneless leg cuts than progeny of the other sire breeds. Boneless sirloins were heavier (P < 0.01) for Suffolk-sired than Composite-sired lambs but did not differ from those for Columbia- or Texel-sired lambs. Columbia- and Suffolk-sired lambs had heavier (P < 0.01) hindshanks than Texel-sired lambs. Suffolk-sired lambs had heavier (P < 0.01) high-value cuts (rack, loin, leg, and sirloin) and trimmed high-value cuts than progeny of the other sire breeds. Cutting loss (CCW - wholesale cut weights) and high-value trimming loss were greatest (P < 0.02) for Suffolk-sired lambs and least for Texel- and Composite-sired lambs. Sire breed did not affect (P > 0.06) flank weight. Data adjusted to comparable CCW reduced the number of significant sire-breed effects and changed sire-breed rankings of carcass component weights, for which sire breeds differed. After adjusting, Suffolk-sired lambs had lighter (P < 0.05) loins than Columbia- and Composite-sired lambs, Composite-sired lambs had heavier (P < 0.05) high-value cuts than Suffolk-sired lambs, and Suffolk- and Columbia-sired lambs had heavier (P < 0.05) necks than Texel-sired lambs. At predicted backfat thickness of 6.6 mm, Composite-sired lambs had a greater (P < 0.05) percentage of high-value cuts than Suffolk-sired lambs before but not after trimming. Producers can use these results to select terminal-sire breeds that will complement their production system and improve lamb value.

Detecting regions of homozygosity to map the cause of recessively inherited disease

Homozygosity is a component of genetic patterning that can be used to search for the cause of genetic disease. In this chapter, methods are presented to analyze SNP data for the presence of homozygosity. Two exercises demonstrate methods to define runs of homozygosity, to identify shared homozygosity between individuals, and to evaluate the results in light of the expectations of a recessively inherited genetic disorder. An example dataset is used to aid in data interpretation.

Lack of association between allelic status and myostatin content in lambs with the myostatin g+6723G>A allele

Lambs with the myostatin (MSTN) g+6723G>A mutation have a greater muscle mass, which is believed to be associated with reduced myostatin protein abundance. This experiment was designed to determine if differences in allelic frequency of the MSTN g+6723G>A mutation affected abundance of myostatin protein from birth to 24 wk of age. A Poll Dorset cross White Suffolk ram (MSTN A/G) was mated to 35 White Suffolk cross Border Leicester cross Merino ewes (MSTN A/G, n=21, and MSTN G/G, n=14). The progeny of these matings delivered 44 lambs with MSTN A/A (n=9), MSTN A/G (n=21), and MSTN G/G (n=14) genotypes. At approximately 1, 4, and 12 wk of age, a biopsy sample was collected and a blood sample was taken to measure the abundance of myostatin protein in muscle and plasma. At approximately 24 wk of age, the wether lambs were slaughtered to determine carcass characteristics and muscle samples were taken from the bicep femoris. The abundance of mature myostatin protein in muscle from 1 wk old lambs was less (P=0.05) in MSTN A/A and MSTN A/G compared with MSTN G/G lambs. However, at 4 and 24 wk the MSTN A/A lambs had a greater (P=0.04) abundance of myostatin protein compared with the MSTN A/G and MSTN G/G lambs. The abundance of mature myostatin did not differ between genotypes in plasma but the myostatin protein did increase as the lambs aged. At slaughter the MSTN A/A wether lambs had greater dressing percentages (P=0.04), shortloin (P=0.01), topside (P<0.001), and round (P=0.01) weights but did not differ in final BW or HCW (P>0.05). The MSTN A/A lambs had more muscle fibers (P=0.02) in the cross-section of LM between the 12th and 13th rib. The MSTN A/A lambs also had greater lean (P=0.002), less fat (P=0.009), and reduced organ (heart, liver, spleen, and kidneys) mass as determined by computed tomography scanning than MSTN G/G lambs. The results of this study demonstrated that lambs homozygous for the MSTN g+6723G>A mutation have changes in carcass characteristics (dressing and total lean), organ weights, and muscle fiber number. This may be due to reduced myostatin protein early in utero, but after 4 wk of age there was no difference in the abundance of mature myostatin protein in muscle or plasma among MSTN A/A, MSTN A/G, and MSTN G/G genotypes.

Effects of the Texel muscling quantitative trait locus on carcass traits in crossbred lambs

Texel muscling quantitative trait locus (TM-QTL) is a QTL on chromosome 18, originally identified in purebred UK Texel sheep, which was reported to increase ultrasonically measured muscle depth at the third lumbar vertebra by around 4% to 7%. The objective of the present study was to comprehensively evaluate the TM-QTL and to determine whether it could provide benefits to the UK sheep industry through increased carcass meat yield in crossbred slaughter lambs. Effects of this QTL on a range of carcass traits, including those measured in vivo and by dissection, were evaluated in heterozygous carrier and non-carrier lambs produced by crossing heterozygous carrier Texel rams with non-carrier Mule (Bluefaced Leicester × Scottish Blackface) ewes from a lowland flock. The TM-QTL was found to increase loin muscling in crossbred lambs at a given live weight or carcass weight, as measured by ultrasound, X-ray computed tomography (CT) and carcass dissection. Depth of M. longissimus lumborum (MLL) was greater in TM-QTL carrier lambs compared to non-carriers as measured by both ultrasound at the third lumbar vertebra (+4.5%; P = 0.033) and CT scanning at the fifth lumbar vertebra (+6.7%; P = 0.004). Width and area of MLL measured using CT were also greater in TM-QTL carrier lambs compared to non-carriers (+3.0%; P = 0.013 and +5.1%; P = 0.047, respectively). Loin muscle volume measured using CT was greater in TM-QTL carriers than in non-carriers (+5.9%; P = 0.005) and the dissected weight of the MLL was +7.1% greater in TM-QTL carriers compared to non-carriers (P < 0.001). The proportion of the total carcass lean meat yield (LMY) that was contained within the loin region was slightly higher in TM-QTL carriers than in non-carriers (0.154 v. 0.145; P = 0.006). However, TM-QTL was found to have no significant effect on the total weight or proportion of LMY or of saleable meat yield in the carcass measured by dissection, or on muscling in the hind leg measured by CT or dissection. This work has verified that the inheritance of TM-QTL is associated with increased loin muscling in crossbred lambs, as has previously been reported for purebred Texel lambs.

Genes contributing to genetic variation of muscling in sheep

Selective breeding programs aiming to increase the productivity and profitability of the sheep meat industry use elite, progeny tested sires. The broad genetic traits of primary interest in the progeny of these sires include skeletal muscle yield, fat content, eating quality, and reproductive efficiency. Natural mutations in sheep that enhance muscling have been identified, while a number of genome scans have identified and confirmed quantitative trait loci (QTL) for skeletal muscle traits. The detailed phenotypic characteristics of sheep carrying these mutations or QTL affecting skeletal muscle show a number of common biological themes, particularly changes in developmental growth trajectories, alterations of whole animal morphology, and a shift toward fast twitch glycolytic fibers. The genetic, developmental, and biochemical mechanisms underpinning the actions of some of these genetic variants are described. This review critically assesses this research area, identifies gaps in knowledge, and highlights mechanistic linkages between genetic polymorphisms and skeletal muscle phenotypic changes. This knowledge may aid the discovery of new causal genetic variants and in some cases lead to the development of biochemical and immunological strategies aimed at enhancing skeletal muscle.

Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires in an extensive rangeland production system: II. Postweaning growth and ultrasonic measures of composition for lambs fed a high-energy feedlot diet

Over 3 yr, postweaning growth patterns and changes in ultrasonic measurements of fat depth (FD) and LM area were assessed for 1,049 crossbred ewe and wether lambs (Ovis aries) produced by mating adult Rambouillet ewes to 1 of 22 Columbia, 22 USMARC-Composite (Composite), 21 Suffolk, or 17 Texel rams and raised to weaning under extensive Western rangeland conditions. After weaning, lambs were transitioned to a high-energy finishing diet in a feedlot, weighed weekly for 13 to 16 wk, and scanned using ultrasound at 2-wk intervals to estimate FD and LM area between the 12th and 13th ribs. Lambs sired by Suffolk rams were 5 to 12% heavier (P < 0.05) at start of test, grew 14 to 22% faster (P < 0.001), and were correspondingly 7 to 14% heavier (P < 0.001) after 90 d on test than lambs sired by rams of the other 3 breeds. At this time, lambs sired by Texel rams were 5% lighter (P < 0.01) than Columbia- or Composite-sired lambs, which did not differ (P > 0.20). Columbia-sired lambs had less FD (8.9 mm) but smaller LM areas (15.6 cm(2)) at 90 d on test (both P < 0.01) than lambs sired by rams of the other breeds (average of 9.8 mm for FD and 16.6 cm(2) for LM area), which did not differ for either measurement at this time. At 60 kg, predicted FD differed among sire breeds (P < 0.001) and were similar for Suffolk- (7.6 mm) and Columbia-sired (7.9 mm) lambs, intermediate for Composite-sired lambs (9.1 mm), and largest for Texel-sired (10.1 mm) lambs. At a BW of 60 kg, LM area differed between all pairs of sire breeds (P < 0.05), and was largest for Texel-sired lambs (16.7 cm(2)), followed by Composite-, Suffolk-, and Columbia-sired lambs (15.7, 14.8, and 14.5 cm(2), respectively). At a predicted FD of 9.1 mm (the boundary between U.S. Yield Grades 3 and 4), the predicted LM area for Suffolk-sired lambs (16.2 cm(2)) was similar (P > 0.10) to that of Texel-sired lambs (16.0 cm(2)) and superior (P < 0.01) to that of Composite- (15.7 cm(2)) and Columbia-sired lambs (15.4 cm(2)). Lambs sired by Suffolk rams were thus equal or superior to lambs sired by the other 3 breeds in growth, FD, and LM area at comparable ages, fatness at 60 kg, and LM area at a FD of 9.1 mm, but inferior in LM area to Texel- and Composite-sired lambs at comparable BW.

Design and phenotyping procedures for recording wool, skin, parasite resistance, growth, carcass yield and quality traits of the SheepGENOMICS mapping flock

A major aim of the research program known as SheepGENOMICS was to deliver DNA markers for commercial breeding programs. To that end, a resource flock was established, comprehensively phenotyped and genotyped with DNA markers. The flock of nearly 5000 sheep, born over two consecutive years, was extensively phenotyped, with more than 100 recorded observations being made on most of the animals. This generated more than 460 000 records over 17 months of gathering information on each animal. Here, we describe the experimental design and sample-collection procedures, and provide a summary of the basic measurements taken. Data from this project are being used to identify collections of genome markers for estimating genomic breeding values for new sheep industry traits.

Characterization of a myostatin gene (MSTN1) from spotted halibut (Verasper variegatus) and association between its promoter polymorphism and individual growth performance

Myostatin (MSTN) is a member of the transforming growth factor-β superfamily which could play an important role in negatively regulating skeletal muscle growth and development in mammal and non-mammal species. In the present study, a MSTN1 gene (designated as VvMSTN1) was cloned and characterized in one flatfish species, spotted halibut (Verasper variegatus). In the 3078 bp genomic sequence, three exons, two introns and a promoter sequence were identified. Sequence analysis of the promoter region revealed that it contained several cis-regulatory elements such as CAAT-box, TATA-box and E-boxes. The deduced protein sequence included a signal peptide, a TGF-β propeptide in the N-terminal region and the TGF-β active peptide in the C-terminal region. Phylogenetic analysis suggested that VvMSTN1 is an orthologue of teleost MSTN1 proteins which arose along with MSTN2 during a duplication event at the base of teleost evolution. Quantitative real-time PCR analysis revealed that VvMSTN1 mRNA was ubiquitously expressed in all nine tested tissues, with the most transcriptionally abundant in skeletal muscle. A primary assessment of sequence variability revealed five single nucleotide polymorphisms (SNPs) existed in the promoter region, among which three (G-653T, T-355C and G-253A) were genotyped with an advanced melting temperature (T(m))-shift method and tested for their association with growth traits (body length, body depth and total mass). Results indicated that genotype CC of locus T-355C had significantly higher growth traits than genotype TC and TT (P<0.05) in female spotted halibut. These results suggest that V. variegatus MSTN could be selected as a candidate gene for the future molecular breeding of stains with enhanced individual growth performance.

QTL mapping for sexually dimorphic fitness-related traits in wild bighorn sheep

Dissecting the genetic architecture of fitness-related traits in wild populations is key to understanding evolution and the mechanisms maintaining adaptive genetic variation. We took advantage of a recently developed genetic linkage map and phenotypic information from wild pedigreed individuals from Ram Mountain, Alberta, Canada, to study the genetic architecture of ecologically important traits (horn volume, length, base circumference and body mass) in bighorn sheep. In addition to estimating sex-specific and cross-sex quantitative genetic parameters, we tested for the presence of quantitative trait loci (QTLs), colocalization of QTLs between bighorn sheep and domestic sheep, and sex × QTL interactions. All traits showed significant additive genetic variance and genetic correlations tended to be positive. Linkage analysis based on 241 microsatellite loci typed in 310 pedigreed animals resulted in no significant and five suggestive QTLs (four for horn dimension on chromosomes 1, 18 and 23, and one for body mass on chromosome 26) using genome-wide significance thresholds (Logarithm of odds (LOD) >3.31 and >1.88, respectively). We also confirmed the presence of a horn dimension QTL in bighorn sheep at the only position known to contain a similar QTL in domestic sheep (on chromosome 10 near the horns locus; nominal P<0.01) and highlighted a number of regions potentially containing weight-related QTLs in both species. As expected for sexually dimorphic traits involved in male-male combat, loci with sex-specific effects were detected. This study lays the foundation for future work on adaptive genetic variation and the evolutionary dynamics of sexually dimorphic traits in bighorn sheep.

Histological and transcriptome-wide level characteristics of fetal myofiber hyperplasia during the second half of gestation in Texel and Ujumqin sheep

BACKGROUND

Whether myofibers increase with a pulsed-wave mode at particular developmental stages or whether they augment evenly across developmental stages in large mammals is unclear. Additionally, the molecular mechanisms of myostatin in myofiber hyperplasia at the fetal stage in sheep remain unknown. Using the first specialized transcriptome-wide sheep oligo DNA microarray and histological methods, we investigated the gene expression profile and histological characteristics of developing fetal ovine longissimus muscle in Texel sheep (high muscle and low fat), as a myostatin model of natural mutation, and Ujumqin sheep (low muscle and high fat). Fetal skeletal muscles were sampled at 70, 85, 100, 120, and 135 d of gestation.

RESULTS

Myofiber number increased sharply with a pulsed-wave mode at certain developmental stages but was not augmented evenly across developmental stages in fetal sheep. The surges in myofiber hyperplasia occurred at 85 and 120 d in Texel sheep, whereas a unique proliferative surge appeared at 100 d in Ujumqin sheep. Analysis of the microarray demonstrated that immune and hematological systems' development and function, lipid metabolism, and cell communication were the biological functions that were most differentially expressed between Texel and Ujumqin sheep during muscle development. Pathways associated with myogenesis and the proliferation of myoblasts, such as calcium signaling, chemokine (C-X-C motif) receptor 4 signaling, and vascular endothelial growth factor signaling, were affected significantly at specific fetal stages, which underpinned fetal myofiber hyperplasia and postnatal muscle hypertrophy. Moreover, we identified some differentially expressed genes between the two breeds that could be potential myostatin targets for further investigation.

CONCLUSIONS

Proliferation of myofibers proceeded in a pulsed-wave mode at particular fetal stages in the sheep. The myostatin mutation changed the gene expression pattern in skeletal muscle at a transcriptome-wide level, resulting in variation in myofiber phenotype between Texel and Ujumqin sheep during the second half of gestation. Our findings provide a novel and dynamic description of the effect of myostatin on skeletal muscle development, which contributes to understanding the biology of muscle development in large mammals.