Genetic variation in the bovine myostatin gene in UK beef cattle: allele frequencies and haplotype analysis in the South Devon

Associations between polymorphisms in the myostatin gene with calving difficulty and carcass merit in cattle

A fully functional myostatin gene inhibits muscle fiber growth. The objective of the present study was to quantify the association between 21 known myostatin mutations with both calving and carcass traits in 12 cattle breeds. The myostatin genotypes of 32,770 dam-progeny combinations were used in the association analysis of calving dystocia, with the genotypes of 129,803 animals used in the mixed model association analyses of carcass weight, conformation, and fat score. The mixed model included additive genetic, maternal, and permanent environmental effects where appropriate. The mutant genotypes of nt821, Q204X, and F94L were all associated (P < 0.01) with more calving difficulty when present in either the dam or the progeny. The nt821 deletion had the greatest association with calving difficulty when the homozygous deletion was present in either the calf (0.37 points greater calving difficulty score relative to calves carrying no copies of the deletion based on a one to four scale) or the dam (1.30 points greater calving difficulty score relative to dams carrying no copies of the deletion), although the association between the calf's nt821 genotype and calving difficulty differed depending on the nt821 genotype of the dam. With the exception of nt748_78, nt414, and nt374_51, all other seven segregating myostatin variants were associated (range of allele substitution effect size relative to animals with no copies of the mutant allele) with carcass weight (2.36 kg lighter to 15.56 kg heavier), all 10 segregating variants with conformation (0.15 units less conformed to 2.24 units more conformed assessed on a scale of 1 to 15), and all segregating variants other than E226X with carcass fat (0.23 units less carcass fat cover to 3.85 units more carcass fat cover assessed on a scale of 1 to 15). Of these, the F94L, Q204X, and nt821 mutations generally had the greatest association with all three carcass traits, giving rise to heavier and more conformed carcasses. Despite the antagonistic genetic relationship between calving difficulty and carcass traits, the nt374_51, F94L, and E226X mutations were all associated with improved carcass merit while having minimal expected consequences on calving difficulty. Thus, animals carrying these mutation(s) may have favorable genetic merit for calving difficulty and carcass merit. Furthermore, depending on the dam genotype, a bull with two copies of the nt821 mutation can produce progeny with improved carcass merit while minimizing calving problems.

Associations between the Bovine Myostatin Gene and Milk Fatty Acid Composition in New Zealand Holstein-Friesian × Jersey-Cross Cows

Simple Summary

The gene that encodes myostatin influences more than one trait, and its expression has been observed in skeletal muscle, as well as the mammary gland. In this study, association analysis revealed that variation in the bovine myostatin gene affects milk fatty acid composition, raising the possibility that this genetic variation may be utilized to increase the amount of unsaturated fatty acid and decrease the amount of saturated fatty acid in milk.

Abstract

The myostatin gene (MSTN), which encodes the protein myostatin, is pleiotropic, and its expression has been associated with both increased and decreased adipogenesis and increased skeletal muscle mass in animals. In this study, the polymerase chain reaction, coupled with single strand conformation polymorphism analysis, was utilized to reveal nucleotide sequence variation in bovine MSTN in 410 New Zealand (NZ) Holstein-Friesian × Jersey (HF × J)-cross cows. These cows ranged from 3 to 9 years of age and over the time studied, produced an average 22.53 ± 2.18 L of milk per day, with an average milk fat content of 4.94 ± 0.17% and average milk protein content of 4.03 ± 0.10%. Analysis of a 406-bp amplicon from the intron 1 region, revealed five nucleotide sequence variants (A–E) that contained seven nucleotide substitutions. Using general linear mixed-effect model analyses the AD genotype was associated with reduced C10:0, C12:0, and C12:1 levels when compared to levels in cows with the AA genotype. These associations in NZ HF × J cross cows are novel, and they suggest that this variation in bovine MSTN could be explored for increasing the amount of milk unsaturated fatty acid and decreasing the amount of saturated fatty acid.

Generation of Myostatin Gene-Edited Channel Catfish (Ictalurus punctatus) via Zygote Injection of CRISPR/Cas9 System

The myostatin (MSTN) gene is important because of its role in regulation of skeletal muscle growth in all vertebrates. In this study, CRISPR/Cas9 was utilized to successfully target the channel catfish, Ictalurus punctatus, muscle suppressor gene MSTN. CRISPR/Cas9 induced high rates (88-100%) of mutagenesis in the target protein-encoding sites of MSTN. MSTN-edited fry had more muscle cells (p < 0.001) than controls, and the mean body weight of gene-edited fry increased by 29.7%. The nucleic acid alignment of the mutated sequences against the wild-type sequence revealed multiple insertions and deletions. These results demonstrate that CRISPR/Cas9 is a highly efficient tool for editing the channel catfish genome, and opens ways for facilitating channel catfish genetic enhancement and functional genomics. This approach may produce growth-enhanced channel catfish and increase productivity.

Generation of cloned adult muscular pigs with myostatin gene mutation by genetic engineering

Skeletal muscle is the most economically valuable tissue in meat-producing animals and enhancing muscle growth in these species may enhance the efficiency of meat production.

Epigenetics and developmental programming of welfare and production traits in farm animals

The concept that postnatal health and development can be influenced by events that occur in utero originated from epidemiological studies in humans supported by numerous mechanistic (including epigenetic) studies in a variety of model species. Referred to as the 'developmental origins of health and disease' or 'DOHaD' hypothesis, the primary focus of large-animal studies until quite recently had been biomedical. Attention has since turned towards traits of commercial importance in farm animals. Herein we review the evidence that prenatal risk factors, including suboptimal parental nutrition, gestational stress, exposure to environmental chemicals and advanced breeding technologies, can determine traits such as postnatal growth, feed efficiency, milk yield, carcass composition, animal welfare and reproductive potential. We consider the role of epigenetic and cytoplasmic mechanisms of inheritance, and discuss implications for livestock production and future research endeavours. We conclude that although the concept is proven for several traits, issues relating to effect size, and hence commercial importance, remain. Studies have also invariably been conducted under controlled experimental conditions, frequently assessing single risk factors, thereby limiting their translational value for livestock production. We propose concerted international research efforts that consider multiple, concurrent stressors to better represent effects of contemporary animal production systems.

Genomic BLUP including additive and dominant variation in purebreds and F1 crossbreds, with an application in pigs

BACKGROUND

Most developments in quantitative genetics theory focus on the study of intra-breed/line concepts. With the availability of massive genomic information, it becomes necessary to revisit the theory for crossbred populations. We propose methods to construct genomic covariances with additive and non-additive (dominance) inheritance in the case of pure lines and crossbred populations.

RESULTS

We describe substitution effects and dominant deviations across two pure parental populations and the crossbred population. Gene effects are assumed to be independent of the origin of alleles and allelic frequencies can differ between parental populations. Based on these assumptions, the theoretical variance components (additive and dominant) are obtained as a function of marker effects and allelic frequencies. The additive genetic variance in the crossbred population includes the biological additive and dominant effects of a gene and a covariance term. Dominance variance in the crossbred population is proportional to the product of the heterozygosity coefficients of both parental populations. A genomic BLUP (best linear unbiased prediction) equivalent model is presented. We illustrate this approach by using pig data (two pure lines and their cross, including 8265 phenotyped and genotyped sows). For the total number of piglets born, the dominance variance in the crossbred population represented about 13 % of the total genetic variance. Dominance variation is only marginally important for litter size in the crossbred population.

CONCLUSIONS

We present a coherent marker-based model that includes purebred and crossbred data and additive and dominant actions. Using this model, it is possible to estimate breeding values, dominant deviations and variance components in a dataset that comprises data on purebred and crossbred individuals. These methods can be exploited to plan assortative mating in pig, maize or other species, in order to generate superior crossbred individuals in terms of performance.

An interpretive review of selective sweep studies in Bos taurus cattle populations: identification of unique and shared selection signals across breeds

This review compiles the results of 21 genomic studies of European Bos taurus breeds and thus provides a general picture of the selection signatures in taurine cattle identified by genome-wide selection-mapping scans. By performing a comprehensive summary of the results reported in the literature, we compiled a list of 1049 selection sweeps described across 37 cattle breeds (17 beef breeds, 14 dairy breeds, and 6 dual-purpose breeds), and four different beef-vs.-dairy comparisons, which we subsequently grouped into core selective sweep (CSS) regions, defined as consecutive signals within 1 Mb of each other. We defined a total of 409 CSSs across the 29 bovine autosomes, 232 (57%) of which were associated with a single-breed (Single-breed CSSs), 134 CSSs (33%) were associated with a limited number of breeds (Two-to-Four-breed CSSs) and 39 CSSs (9%) were associated with five or more breeds (Multi-breed CSSs). For each CSS, we performed a candidate gene survey that identified 291 genes within the CSS intervals (from the total list of 5183 BioMart-extracted genes) linked to dairy and meat production, stature, and coat color traits. A complementary functional enrichment analysis of the CSS positional candidates highlighted other genes related to pathways underlying behavior, immune response, and reproductive traits. The Single-breed CSSs revealed an over-representation of genes related to dairy and beef production, this was further supported by over-representation of production-related pathway terms in these regions based on a functional enrichment analysis. Overall, this review provides a comparative map of the selection sweeps reported in European cattle breeds and presents for the first time a characterization of the selection sweeps that are found in individual breeds. Based on their uniqueness, these breed-specific signals could be considered as “divergence signals,” which may be useful in characterizing and protecting livestock genetic diversity.

Body composition and gene expression QTL mapping in mice reveals imprinting and interaction effects

BACKGROUND

Shifts in body composition, such as accumulation of body fat, can be a symptom of many chronic human diseases; hence, efforts have been made to investigate the genetic mechanisms that underlie body composition. For example, a few quantitative trait loci (QTL) have been discovered using genome-wide association studies, which will eventually lead to the discovery of causal mutations that are associated with tissue traits. Although some body composition QTL have been identified in mice, limited research has been focused on the imprinting and interaction effects that are involved in these traits. Previously, we found that Myostatin genotype, reciprocal cross, and sex interacted with numerous chromosomal regions to affect growth traits.

RESULTS

Here, we report on the identification of muscle, adipose, and morphometric phenotypic QTL (pQTL), translation and transcription QTL (tQTL) and expression QTL (eQTL) by applying a QTL model with additive, dominance, imprinting, and interaction effects. Using an F2 population of 1000 mice derived from the Myostatin-null C57BL/6 and M16i mouse lines, six imprinted pQTL were discovered on chromosomes 6, 9, 10, 11, and 18. We also identified two IGF1 and two Atp2a2 eQTL, which could be important trans-regulatory elements. pQTL, tQTL and eQTL that interacted with Myostatin, reciprocal cross, and sex were detected as well. Combining with the additive and dominance effect, these variants accounted for a large amount of phenotypic variation in this study.

CONCLUSIONS

Our study indicates that both imprinting and interaction effects are important components of the genetic model of body composition traits. Furthermore, the integration of eQTL and traditional QTL mapping may help to explain more phenotypic variation than either alone, thereby uncovering more molecular details of how tissue traits are regulated.

Gene-based single nucleotide polymorphism discovery in bovine muscle using next-generation transcriptomic sequencing

Background

Genetic information based on molecular markers has increasingly being used in cattle breeding improvement programmes, as a mean to improve conventionally phenotypic selection. Advances in molecular genetics have led to the identification of several genetic markers associated with genes affecting economic traits. Until recently, the identification of the causative genetic variants involved in the phenotypes of interest has remained a difficult task. The advent of novel sequencing technologies now offers a new opportunity for the identification of such variants. Despite sequencing costs plummeting, sequencing whole-genomes or large targeted regions is still too expensive for most laboratories. A transcriptomic-based sequencing approach offers a cheaper alternative to identify a large number of polymorphisms and possibly to discover causative variants. In the present study, we performed a gene-based single nucleotide polymorphism (SNP) discovery analysis in bovine Longissimus thoraci, using RNA-Seq. To our knowledge, this represents the first study done in bovine muscle.

Results

Messenger RNAs from Longissimus thoraci from three Limousin bull calves were subjected to high-throughput sequencing. Approximately 36–46 million paired-end reads were obtained per library. A total of 19,752 transcripts were identified and 34,376 different SNPs were detected. Fifty-five percent of the SNPs were found in coding regions and ~22% resulted in an amino acid change. Applying a very stringent SNP quality threshold, we detected 8,407 different high-confidence SNPs, 18% of which are non synonymous coding SNPs. To analyse the accuracy of RNA-Seq technology for SNP detection, 48 SNPs were selected for validation by genotyping. No discrepancies were observed when using the highest SNP probability threshold. To test the usefulness of the identified SNPs, the 48 selected SNPs were assessed by genotyping 93 bovine samples, representing mostly the nine major breeds used in France. Principal component analysis indicates a clear separation between the nine populations.

Conclusions

The RNA-Seq data and the collection of newly discovered coding SNPs improve the genomic resources available for cattle, especially for beef breeds. The large amount of variation present in genes expressed in Limousin Longissimus thoracis, especially the large number of non synonymous coding SNPs, may prove useful to study the mechanisms underlying the genetic variability of meat quality traits.

Detection of signatures of selective sweeps in the Blonde d'Aquitaine cattle breed

Identifying recent positive selection signatures in domesticated animals could provide information on genome response to strong directional selection from domestication and artificial selection and therefore could help in identifying mutations responsible for improved traits. We used genotyping data generated using Illumina's BovineSNP50 Genotyping BeadChips to identify selection signatures in the Blonde d'Aquitaine breed, a well-muscled French beef breed. For this purpose, we employed a hidden Markov model-based test, which detects selection by studying local variations in the allele frequency spectrum along the genome, within a single population. Three regions containing selective sweeps were identified. Annotation of genes located within these regions revealed interesting candidate genes. For example, myostatin (also known as GDF8), a known muscle growth factor inhibitor, is located within the selection signature region found on chromosome 2. In addition, we have identified chromosomal regions that show some evidence of selection within QTL regions for economically important traits. The results of this study could help to better understand the mechanisms related to the selection of the Blonde d'Aquitaine breed.

Effect of the myostatin locus on muscle mass and intramuscular fat content in a cross between mouse lines selected for hypermuscularity

Background

This study is aimed at the analysis of genetic and physiological effects of myostatin on economically relevant meat quality traits in a genetic background of high muscularity. For this purpose, we generated G₃ populations of reciprocal crosses between the two hypermuscular mouse lines BMMI866, which carries a myostatin mutation and is lean, and BMMI806, which has high intramuscular and body fat content. To assess the relationship between muscle mass, body composition and muscle quality traits, we also analysed intramuscular fat content (IMF), water holding capacity (WHC), and additional physiological parameters in M. quadriceps and M. longissimus in 308 G₃-animals.

Results

We found that individuals with larger muscles have significantly lower total body fat (r = −0.28) and IMF (r = −0.64), and in females, a lower WHC (r = −0.35). In males, higher muscle mass was also significantly correlated with higher glycogen contents (r = 0.2) and lower carcass pH-values 24 hours after dissection (r = −0.19). Linkage analyses confirmed the influence of the myostatin mutation on higher lean mass (1.35 g), reduced body fat content (−1.15%), and lower IMF in M. longissimus (−0.13%) and M. quadriceps (−0.07%). No effect was found for WHC. A large proportion of variation of intramuscular fat content of the M. longissimus at the myostatin locus could be explained by sex (23%) and direction-of-cross effects (26%). The effects were higher in males (+0.41%). An additional locus with negative over-dominance effects on total fat mass (−0.55 g) was identified on chromosome 16 at 94 Mb (86–94 Mb) which concurs with fat related QTL in syntenic regions on SSC13 in pigs and BTA1 in cattle.

Conclusion

The data shows QTL effects on mouse muscle that are similar to those previously observed in livestock, supporting the mouse model. New information from the mouse model helps to describe variation in meat quantity and quality, and thus contribute to research in livestock.

Structural and functional characterizations of activin type 2B receptor (acvr2b) ortholog from the marine fish, gilthead sea bream, Sparus aurata: evidence for gene duplication of acvr2b in fish

Myostatin (MSTN), a negative regulator of muscle growth and a member of the transforming growth factor-β superfamily, can bind the two activin type 2 receptors (ACVR2). It has been previously shown that WT mice injected with ACVR2B extracellular domain (ACVR2B-ECD) had higher muscle mass. Likewise, fish larvae immersed in Pichia pastoris culture supernatant, containing goldfish Acvr2b-ECD, showed enhanced larval growth. However, it is not clear whether fish Mstn1 and Mstn2 signal through the same receptor and whether fish express more than one acvr2b gene. In the current study, three cDNAs encoding acvr2b (saacvr2b-1, saacvr2b-2a, and saacvr2b-2b) were cloned from gilthead sea bream. All three contain the short extracellular binding domain, a short transmembrane region, and a conserved catalytic domain of serine/threonine protein kinase. Bioinformatics analysis provided evidence for the existence of two acvr2b genes (acvr2b-1 and acvr2b-2) in several other fish species as well, probably as a result of gene or genome duplication. The two isoforms differ in their amino acid sequences. The direct inhibitory effect of Acvr2b-ECD on Mstn activity was tested in vitro. The saAcvr2b-1-ECD was expressed in the yeast P. pastoris. Evidence is provided for N-glycosylation of Acvr2b-1-ECD. The affinity-purified Acvr2b-1-ECD inhibited recombinant mouse/rat/human mature MSTN activity when determined in vitro using the CAGA-luciferase assay in A204 cells. A lower inhibitory activity was obtained when unprocessed purified, furin-digested, and activated saMstn1 was used. Results of this study demonstrate for the first time the existence of two acvr2b genes in fish. In addition, the study shows that bioactive fish Acvr2b-ECD can be produced from P. pastoris.

Genomic cloning and promoter functional analysis of myostatin-2 in shi drum, Umbrina cirrosa: conservation of muscle-specific promoter activity

Myostatin (MSTN) is a member of the transforming growth factor-ß superfamily, known as a negative regulator of skeletal muscle development and growth in mammals. In contrast to mammals, fish possess at least two paralogs of MSTN: MSTN-1 and MSTN-2. Here we describe the cloning and sequence analysis of spliced and precursor (unspliced) transcripts as well as the 5' flanking region of MSTN-2 from the marine fish Umbrina cirrosa (ucMSTN-2). In silico analysis revealed numerous putative cis regulatory elements including several E-boxes known as binding sites to myogenic transcription factors. Transient transfection experiments using non-muscle and muscle cell lines showed high transcriptional activity in muscle cells and in differentiated neural cells, in accordance with our previous findings in MSTN-2 promoter from Sparus aurata. Comparative informatics analysis of MSTN-2 from several fish species revealed high conservation of the predicted amino acid sequence as well as the gene structure (exon length) although intron length varied between species. The proximal promoter of MSTN-2 gene was found to be conserved among Perciforms. In conclusion, this study reinforces our conclusion that MSTN-2 promoter is a very strong promoter, especially in muscle cells. In addition, we show that the MSTN-2 gene structure is highly conserved among fishes as is the predicted amino acid sequence of the peptide.

Organization and functional analysis of the 5' flanking regions of myostatin-1 and 2 genes from Larimichthys crocea

Myostatin (MSTN) is a negative regulator of skeletal muscle growth and development. There are two types of MSTNs in fish, but little is known about their gene regulation. Here, the 5' flanking fragments of 1029 bp from MSTN-1 and 643 bp from MSTN-2 were cloned, sequenced, and analyzed in Larimichthys crocea. Both fragments contained CAAT box and several putative cis-regulatory elements. However, putative TATA box, MyoD, MEF3, SP1, USF, and GH-CSE sites were identified only in the L. crocea MSTN-1 (lcMSTN-1) promoter. Transcriptional activities of four fragments (1013, 841, 514, and 261 bp) truncated from lcMSTN-1 upstream region and two fragments (643 and 296 bp) from lcMSTN-2 upstream region were examined in vitro, using transient transfection in CIK and L6 cells. In CIK cells, the promoter activity correlated positively with the length of truncated fragments in both MSTN-1 and 2. The lcMSTN-2 promoter showed a higher activity than lcMSTN-1 in the corresponding region, which was consistent with MSTN gene expression in vivo. In L6 cells, lcMSTN-2 upstream showed an extremely high luciferase activity. These data indicated that both cloned 5' flanking sequences contained functional promoters, and that transcription regulation of lcMSTN-1 and 2 promoters was significantly different between mammalian and fish cells.

Mapping genetic loci that interact with myostatin to affect growth traits

Myostatin, or GDF8, is an inhibitor of skeletal muscle growth. A non-functional myostatin mutation leads to a double muscling phenotype in some species, for example, mice, cattle and humans. Previous studies have indicated that there are loci in the genome that interact with myostatin to control backfat depth and other complex traits. We now report a quantitative trait loci (QTL) mapping study designed to identify loci that interact with myostatin to impact growth traits in mice. Body weight and average daily gain traits were collected on F2 progeny derived from a myostatin-null C57BL/6 strain by M16i cross. In all, 44 main effect QTL were detected above a 5% genome-wide significance threshold when an interval mapping method was used. An additional 37 QTL were identified to significantly interact with myostatin, sex or reciprocal cross. A total of 12 of these QTL interacted with myostatin genotype. These results provide a foundation for the further fine mapping of genome regions that harbor loci that interact with myostatin.

Myostatin-2 gene structure and polymorphism of the promoter and first intron in the marine fish Sparus aurata: evidence for DNA duplications and/or translocations

BACKGROUND

Myostatin (MSTN) is a member of the transforming growth factor-ß superfamily that functions as a negative regulator of skeletal muscle development and growth in mammals. Fish express at least two genes for MSTN: MSTN-1 and MSTN-2. To date, MSTN-2 promoters have been cloned only from salmonids and zebrafish.

RESULTS

Here we described the cloning and sequence analysis of MSTN-2 gene and its 5' flanking region in the marine fish Sparus aurata (saMSTN-2). We demonstrate the existence of three alleles of the promoter and three alleles of the first intron. Sequence comparison of the promoter region in the three alleles revealed that although the sequences of the first 1050 bp upstream of the translation start site are almost identical in the three alleles, a substantial sequence divergence is seen further upstream. Careful sequence analysis of the region upstream of the first 1050 bp in the three alleles identified several elements that appear to be repeated in some or all sequences, at different positions. This suggests that the promoter region of saMSTN-2 has been subjected to various chromosomal rearrangements during the course of evolution, reflecting either insertion or deletion events. Screening of several genomic DNA collections indicated differences in allele frequency, with allele 'b' being the most abundant, followed by allele 'c', whereas allele 'a' is relatively rare. Sequence analysis of saMSTN-2 gene also revealed polymorphism in the first intron, identifying three alleles. The length difference in alleles '1R' and '2R' of the first intron is due to the presence of one or two copies of a repeated block of approximately 150 bp, located at the 5' end of the first intron. The third allele, '4R', has an additional insertion of 323 bp located 116 bp upstream of the 3' end of the first intron. Analysis of several DNA collections showed that the '2R' allele is the most common, followed by the '4R' allele, whereas the '1R' allele is relatively rare. Progeny analysis of a full-sib family showed a Mendelian mode of inheritance of the two genetic loci. No clear association was found between the two genetic markers and growth rate.

CONCLUSION

These results show for the first time a substantial degree of polymorphism in both the promoter and first intron of MSTN-2 gene in a perciform fish species which points to chromosomal rearrangements that took place during evolution.

Molecular analysis of the first intron in the bovine myostatin gene

To study the mechanism of transcription and expression of the myostatin gene, we cloned and analyzed the sequence of the bovine myostatin gene promoter and first intron from Qinchuan and Red Angus cattle, then constructed eukaryotic expression vectors encoding the GFP vector by replacing the CMV promoter with the bovine myostatin promoter using PCR method, thereby obtaining an expression vector coding GFP report gene with first intron (identified as pEGFP-MSTNPro-intron1). By transfecting C2C12 cells with the vectors, we then compared the effect on GFP gene expression of the promoter and normal first intron of Qinchuan and Red Angus cattle with that from the promoter and a Qinchuan allele with a 16 base pair insertion. After 48 h incubation, fluorescent indices (FIs), which indicate the expression rate and intensity of gene GFP expression, were analyzed by flow cytometry (FCM). Results showed that Qinchuan sequence homology of promoter was 99% with Red Angus, that Qinchuan first intron sequence homology was 99.51% with Red Angus and that first intron homologies of Qinchuan and Red Angus were 99.08 and 99.02%, respectively, with Accession No.AF320998 in GenBank. Expression of the GFP gene did not differ significantly between preparations using the Qinchuan versus Red Angus promoter. Preparations with a construct that included the first intron had higher GFP gene expression in C2C12 cells than those whose construct lacked the first intron (P < 0.05 or P < 0.01). However, there was no significant difference (P > 0.05) in gene expression between normal first intron and 16 bp insertion first intron (+16 bp) preparations.

Assessment of selection mapping near the myostatin gene (GDF-8) in cattle

Domestic species provide a unique opportunity to examine the effects of selection on the genome. The myostatin gene (GDF-8) has been under strong selection in a number of cattle breeds because of its influence on muscle conformation and association with the 'double-muscling' phenotype. This study examined genetic diversity near this gene in a set of breeds including some nearly fixed for the allele associated with double-muscling (MH), some where the allele is segregating at intermediate frequency and some where the allele is absent. A set of microsatellites and SNPs were used to examine patterns of diversity at the centromeric end of bovine chromosome 2, the region where GDF-8 is located, using various statistical methods. The putative position of a selected gene was moved across the genomic region to determine, by regression, a best position of reduced heterozygosity. Additional analyses examined extended homozygous regions and linkage disequilibrium patterns. While the SNP data was not found to be very informative for selection mapping in this dataset, analyses of the microsatellite data provided evidence of selection on GDF-8 in several breeds. These results suggested that, of the breeds examined, the allele was most recently introduced into the South Devon. Limitations to the selection-mapping approach were highlighted from the analysis of the SNP data and the situation where the MH allele was at intermediate frequency.

The effects of a mutation in the myostatin gene on meat and carcass quality

This study examined the effects of a mutation that inactivates the myostatin gene on calving, growth, carcass and meat quality traits in South Devon cattle. This breed carries at intermediate frequency an 11-bp deletion (MH) in the myostatin gene, known to be associated with the double-muscling phenotype, thus allowing a comparison of three genotype classes. The MH allele was associated with increased calving difficulty, carcass weight, muscle conformation and ratio of polyunsaturated to saturated fatty acids, as well as with reduced growth rate, carcass and meat fatness, and desirable flavour. However, the nature of the genetic effects differed between traits: in some cases the heterozygote MH carriers were more similar to the non-carriers than to homozygote carriers and in some cases, intermediate between the two homozygotes. The direction of these genetic effects has implications for the management of this genetic variation in the South Devon and other breeds.

Quantitative analysis of performance, carcass and meat quality traits in cattle from two Australian beef herds in which a null myostatin allele is segregating

Two Australian beef cattle herds, in which selection for muscularity was a primary objective, were used in this study to identify bovine myostatin (MSTN) mutations associated with increased muscling, and to assess associations between genotype and performance, carcass and meat quality traits. One was a research herd (herd A) established from Angus × Hereford cows, and comprised a high and low muscle selection line. The other (herd B) was a commercial beef enterprise with cattle of Angus and Charolais origin. Sequencing of the MSTN coding region and flanking splice junctions in an initial sample of 34 animals from both herds identified the 821 del11 mutation as well as six other polymorphic sites. The nucleotide 374–50C > T polymorphism in intron 1 was found to be in linkage disequilibrium with the 821 del11 mutation, with both variants confined to the high muscle selection line in herd A. No other variants were exclusive to either of the two herd A selection lines. The effect of the 821 del11 mutation was further investigated in a total of 803 cattle from both herds. A relatively high prevalence of 821 del11 heterozygotes (herd A 16%; herd B 23%) was found and heterozygotes had significant advantages in eye muscle area and muscle score over their wildtype counterparts, and did not differ in meat quality. Retail beef yield from steers was higher for the 821 del11 heterozygotes from herd A (67.0 v. 63.5%) and herd B (71.8 v. 68.6%), relative to homozygous wildtype contemporaries, demonstrating the benefits of incorporating single null MSTN alleles into breeding programs.

In utero effects on livestock muscle development and body composition

This review will focus on the evidence for in utero effects on development of skeletal muscle in farm and laboratory animals, particularly sheep and pigs. We will describe genetic and environmental factors that have been shown to alter the numbers of muscle fibres formed and outline our working hypothesis for the mechanism involved and the critical window during pregnancy when these effects are seen. We will then discuss the long-term consequences in terms of body composition. Although this review concentrates on skeletal muscle development, the mechanism we suggest might be equally applicable to other tissues in the body (e.g. the brain, kidneys or sex organs) and, therefore, impact on their physiological functions.

Sequence of GDF 8 (myostatin) gene in Bubalus bubalis

The sequence of myostatin gene (growth differentiation factor 8 [GDF 8]) in Indian riverine buffalo (Bubalus bubalis) is reported. The genomic DNA as well as mRNA were sequenced. The sequence is conserved across all the livestock species. Five nonsynonymous changes as compared to cattle were found in this study and were also confirmed by mRNA sequence. Two intronic single nucleotide polymorphisms (SNPs) were identified in buffalo.

Comparative analysis of GDF 8 (myostatin) in Bos indicus and Bos taurus

We report the myostatin gene sequence of Bos indicus cattle in comparison to Bos taurus. B. indicus genomic sequence was obtained by overlapping PCR amplification of genomic DNA. Exon splice sites were confirmed by mRNA sequencing. There were 5 exonic single nucleotide polymorphisms (SNP) only one of which was a non-synonymous mutation that resulted in a serine to asparagine (S214N) amino acid substitution. The B. indicus gene has two insertions of 16 and 12 bases in the first intron. In addition, SNPs in the 3' UTR and intronic regions are also reported.

Expression, purification, renaturation and activation of fish myostatin expressed in Escherichia coli: facilitation of refolding and activity inhibition by myostatin prodomain

Myostatin (growth and differentiation factor-8) is a member of the transforming growth factor-beta superfamily, is expressed mainly in skeletal muscle and acts as a negative growth regulator. Mature myostatin (C-terminal) is a homodimer that is cleaved post-translationally from the precursor myostatin, also yielding the N-terminal prodomain. We expressed in Escherichia coli three forms of fish myostatin: precursor, prodomain and mature. The three forms were over-expressed as inclusion bodies. Highly purified inclusion bodies were solubilized in a solution containing guanidine hydrochloride and the reducing agent DTT. Refolding (indicated by a dimer formation) of precursor myostatin, mature myostatin or a mixture of prodomain and mature myostatin was compared under identical refolding conditions, performed in a solution containing sodium chloride, arginine, a low concentration of guanidine hydrochloride and reduced and oxidized glutathione at 4 degrees C for 14 days. While precursor myostatin formed a reversible disulfide bond with no apparent precipitation, mature myostatin precipitated in the same refolding solution, unless CHAPS was included, and only a small proportion formed a disulfide bond. The trans presence of the prodomain in the refolding solution prevented precipitation of mature myostatin but did not promote formation of a dimer. Proteolytic cleavage of purified, refolded precursor myostatin with furin yielded a monomeric prodomain and a disulfide-linked, homodimeric mature myostatin, which remained as a latent complex. Activation of the latent complex was achieved by acidic or thermal treatments. These results demonstrate that the cis presence of the prodomain is essential for the proper refolding of fish myostatin and that the cleaved mature dimer exists as a latent form.

Ontogeny of factors associated with proliferation and differentiation of muscle in the ovine fetus1,2

The number of muscle fibers within a muscle has been found to be of high importance for the growth potential of an animal, and this number is set during fetal development. The objective of this study was to identify the ontogeny of muscle cell differentiation and fiber formation by observing the changes in expression of factors known to influence myoblast proliferation and differentiation. Twenty-one Swaledale x Leicester Blue Face ewes carrying twins were allotted to this trial. From d 40 of gestation, three ewes were killed every 15 d until term. At each time point, the fetuses were located, removed, and total muscle from both hind limbs was dissected from each fetus and snap frozen in liquid N2. Ribonuclease protection assays were used to quantify transcripts for IGF-I, IGF-II, GH receptor (GHR), and myostatin genes in the muscle samples, whereas quantitative real-time PCR was used to quantify myogenin transcripts. Histological sections also were taken from the fetal muscle samples and observed for evidence of muscle differentiation resulting in fiber formation. The abundance of mRNA for ovine IGF-II and ovine myogenin peaked at d 85 of gestation (P < 0.001). The abundance of ovine IGF-I transcripts peaked at d 100 of gestation, whereas the abundance of ovine GHR mRNA increased throughout gestation (P < 0.05). No change (P = 0.87) in the abundance of myostatin mRNA was observed. The histological sections from the muscle samples demonstrated a clear change in the appearance of the muscle tissue at each time period. Major fiber formation was observed around d 85. The results obtained from the analysis of gene expression and the histological sections suggest that the majority of muscle differentiation and fiber formation takes place around d 85, with myoblast proliferation mainly occurring before this time. It may be possible to manipulate the number of muscle fibers formed by targeting treatments during this proliferation stage immediately before the period of major fiber formation.

Sequence analysis of myostatin promoter in cattle

Myostatin (GDF8) acts as a negative regulator of muscle growth. Mutations in the gene are responsible for the double muscling phenotype in several European cattle breeds. Here we describe the sequence of the upstream 5' region of the myostatin gene. The sequence analysis was carried out on three animals of nine European cattle breeds, with the aim to search for polymorphisms. A T/A polymorphism at -371 and a G/C polymorphism at -805 (relative to ATG) were found. PCR- RFLP was used to further screen 353 animals of the nine breeds studied and to assess the frequencies of the SNPs. The promoter region of the gene contains several binding sites for transcription factors found also in other myogenic genes. This may play an important role in the regulation of the protein and consequently on muscular development.

Double muscling in Marchigiana beef breed is caused by a stop codon in the third exon of myostatin gene

Double muscling is a partially recessive trait present in some beef breeds. It shows a high frequency in some breeds, while in others the frequency is low, and double-muscled individuals are rare. The double muscling is caused by an allelic series of mutations that cause a loss of function of the myostatin gene ( GDF8). We describe here a new mutation in the myostatin gene in Marchigiana breed, a typical beef breed of Central Italy, in which rare double-muscling individuals have been described. A PCR product of the third exon was sequenced in subjects phenotypically showing double muscling, and a G > T transversion was discovered that introduces a premature stop codon. The variant found adds to the large series of mutations present in cattle, and particularly to the only two causative of double muscling in the third exon. A PCR-RFLP test is described for the rapid and effective identification of both heterozygous and homozygous subjects. It was applied to a larger survey carried on the same and also in two other beef breeds, Chianina and Romagnola. Further individuals carrying the new variant were found in Marchigiana, but none in the other breeds. The results may be important for a better comprehension of the role of myostatin in muscular development, for commercial use and for the inference of phylogeny of this gene.

Signatures of selection? Patterns of microsatellite diversity on a chromosome containing a selected locus

This paper explores patterns of genetic diversity near a locus known to have been under selection. The myostatin gene (GDF-8) has been shown to be associated with double muscling, a phenotype selected for in a number of cattle breeds. We examined population genetic parameters for microsatellite loci at varying distances from GDF-8 in double-muscled (DM) and non-double-muscled (non-DM) cattle breeds in order to assess patterns of diversity. A theoretical analysis was also performed to predict the patterns of diversity expected under different scenarios. We found differences in the patterns of heterozygosity, allele diversity and linkage disequilibrium between DM and non-DM breeds. However, there were some exceptions to the predicted patterns. These are discussed in light of the histories of the breeds and the potential for using microsatellite diversity for mapping trait genes in livestock populations.

Myostatin expression and possible functions in animal muscle growth

Myostatin (also known as growth/differentiation factor-8) is a recently identified member of the transforming growth factor-beta family of secreted regulatory factors. Mice having targeted disruption of the myostatin gene displayed a marked increase in muscle mass, up to three times normal size. Additionally, a myostatin mutation has been linked to double muscled cattle breeds characterized by a visible, generalized increase in muscle mass. Therefore, it is suggested that myostatin in muscle may be one of the long sought inhibitors that specifically control the growth of individual tissues or organs. In the present paper, we review involvement of myostatin in muscle growth of different species.