Myostatinand its implications on animal breeding: a review

Transcriptome profiling reveals SLC5A5 regulates chicken ovarian follicle granulosa cell proliferation, apoptosis, and steroid hormone synthesis

The egg-laying performance of hens holds significant economic importance within the poultry industry. Broody inheritance of the parent stock of chickens can result in poor options for the improvement of egg production, and is a phenomenon influenced by multiple genetic factors. However, few studies have been conducted to delineate the molecular mechanism of ovarian regression in brooding chickens. Here, we explored the pivotal genes responsible for the regulation of ovarian follicles in laying hens, using RNA-sequencing analysis on the small ovarian follicles from broody and laying chickens. Sequencing data analysis revealed the differential expression of 200 genes, with a predominant enrichment in biological processes related to cell activation and metabolism. Among these genes, we focused on solute carrier family 5 member 5 (SLC5A5), which exhibited markedly higher RNA expression levels in follicles from laying compared with broody chickens. Subsequent cellular function studies with knockdown of SLC5A5 in chicken ovarian follicle granulosa cells (GCs) led to the down-regulation of genes associated with cell proliferation and steroid hormone synthesis, and concurrent promotion of gene expression linked to apoptosis. These findings indicated that SLC5A5 deficiency led to the inhibition of proliferation, steroid hormone synthesis and secretion, and promotion of apoptosis in chicken GCs. Our study demonstrated a pivotal role for SLC5A5 in the development and function of chicken GCs, shedding light on its potential significance in the broader context of chicken ovarian follicle development, and providing a prospective target to improve the egg-laying performance of chickens via molecular marker-assisted breeding technology.

Application of PCR-RFLP for quick identification of MSTN mutants in MSTN mutant pig breeding

Knockout of the MSTN gene is linked to the enlarged tongue, and it causes suckling difficulty in animals. The suckling difficulty has a severe effect on animal mortality. Thus, special care was required to ensure their survivability. Here, it is critical to promptly ascertain the genotype of all pigs after birth. The main objective of the present study was to develop the restriction enzyme-mediated PCR-RFLP assay for MSTN mutant pig genotyping. To accomplish this, conserved oligonucleotide primer and restriction site were deduced according to the mutated sequence of the MSTN mutant pigs. PCR amplification yielded a 176 bp band for all homozygous MSTN mutant (MSTN-/-), heterozygous MSTN mutant (MSTN+/-) and wild-type (WT) pigs. However, MSTN+/- samples produced two fragments with 176 and 87 bp, and WT samples produced one fragment with 87 bp after being digested by BstNI. MSTN-/- samples were not digested by BstNI and yielded a 176 bp band. Thus, we were able to determine the genotype of all pigs using BstNI restriction enzyme-mediated PCR-RFLP method. Overall, the present study reported a simple and fast PCR-RFLP genotyping method for MSTN mutant pig breeding. The present study may contribute to the establishment of commercial breeding systems and the production of double muscle pigs.

Relationship between Some Myostatin Variants and Meat Production Related Calving, Weaning and Muscularity Traits in Charolais Cattle

The slaughter value of live cattle can be assessed during visual conformation scoring, as well as by examining different molecular genetic information, e.g., the myostatin gene, which can be responsible for muscle development. In this study, the F94L, Q204X, nt267, nt324 and nt414 alleles of the myostatin gene (MSTN) were examined in relation to birth weight (BIW), calving ease (CAE), 205-day weaning weight (CWW), muscle score of shoulder (MSS), muscle score of back (MSB), muscle score of thigh (MST), roundness score of thigh (RST), loin thickness score (LTS), and overall muscle development percentage (OMP) of Charolais weaned calves in Hungary. Multi-trait analysis of variance (GLM) and weighted linear regression analysis were used to process the data. Calves carrying the Q204X allele in the heterozygous form achieved approximately 0.14 points higher MSB, MST and LTS, and 1.2% higher OMP, and gained 8.56 kg more CWW than their counterparts not carrying the allele (p < 0.05). As for the F94L allele, there was a difference of 4.08 kg in CWW of the heterozygous animals, but this difference could not be proved statistically. The other alleles had no significant effect on the evaluated traits.

Polymorphism of Genes and Their Impact on Beef Quality

The single-nucleotide polymorphism (SNP) form of genes is a valuable source of information regarding their suitability for use as specific markers of desirable traits in beef cattle breeding. For several decades, breeding work focused on improving production efficiency through optimizing the feed conversion ratio and improving daily gains and meat quality. Many research teams previously undertook research work on single-nucleotide polymorphism in myostatin (MSTN), thyroglobulin (TG), calpain (CAPN), and calpastatin (CAST) proteins. The literature review focuses on the most frequently addressed issues concerning these genes in beef cattle production and points to a number of relevant studies on the genes' polymorphic forms. The four genes presented are worth considering during breeding work as a set of genes that can positively influence productivity and production quality.

When Less Is More: Targeting the Myostatin Gene in Livestock for Augmenting Meat Production

How to increase meat production is one of the main questions in animal breeding. Selection for improved body weight has been made and, due to recent genomic advances, naturally occurring variants that are responsible for controlling economically relevant phenotypes have been revealed. The myostatin (MSTN) gene, a superstar gene in animal breeding, was discovered as a negative controller of muscle mass. In some livestock species, natural mutations in the MSTN gene could generate the agriculturally desirable double-muscling phenotype. However, some other livestock species or breeds lack these desirable variants. Genetic modification, particularly gene editing, offers an unprecedented opportunity to induce or mimic naturally occurring mutations in livestock genomes. To date, various MSTN-edited livestock species have been generated using different gene modification tools. These MSTN gene-edited models have higher growth rates and increased muscle mass, suggesting the high potential of utilizing MSTN gene editing in animal breeding. Additionally, post-editing investigations in most livestock species support the favorable influence of targeting the MSTN gene on meat quantity and quality. In this Review, we provide a collective discussion on targeting the MSTN gene in livestock to further encourage its utilization opportunities. It is expected that, shortly, MSTN gene-edited livestock will be commercialized, and MSTN-edited meat will be on the tables of ordinary customers.

Novel Polymorphisms in Caprine Myostatin Gene and its Relationship with Growth Traits in Saburai Does (Capra hircus)

<b>Background and Objective:</b> Saburai goat (<i>Capra hircus</i>) is a crossbred goat from Boer buck (75%) and Ettawa doe (25%) for meat production purposes. This study was carried out to detect the mutation points or Single Nucleotide Polymorphisms (SNPs) in the myostatin (<i>MSTN</i>) gene of Saburai with the forward sequencing method. <b>Materials and Methods:</b> A total of twenty-one blood samples of Saburai does (75% Boer, 25% Ettawa) were collected from the Villager Breeder Center (VBC) at Tanggamus Regency of Lampung Province, Indonesia. The DNA analysis consists of DNA isolation, PCR analysis and sequencing analysis. The record data were used for association study with the mathematical model: Y_ij = μ+G_i+Є_ij. <b>Results:</b> Research showed that one common SNP of g.217_218.indel.TTTTA (5'UTR) and three novel SNPs of c.386G>C (exon 1), g.641_642.indel.T (intron 2) and c.4957G>C (exon 3) were detected in the present study. In this study, a novel SNP on exon 1 and intron 2 of Saburai <i>MSTN</i> gene has a moderate PIC value (>0.30). In addition, a novel SNP on exon 1 and exon 3 of the Saburai <i>MSTN</i> gene was detected as a missense mutation of A55P and A43P, respectively. Goats with the heterozygous genotype have higher growth traits compared to goats with the homozygous genotype. <b>Conclusion:</b> The goats with heterozygous genotypes can be further developed to increase the productivity of Saburai goats.

A Preliminary Investigation of Myostatin Gene (MSTN) Variation in Red Deer (Cervus elaphus) and Its Implications for Venison Production in New Zealand

Simple Summary

Myostatin is a negative regulator of skeletal muscle growth. Despite variation in the myostatin gene having been reported in livestock species, little work has been undertaken in red deer (Cervus elaphus). This study describes the presence of two nucleotide sequences of the myostatin gene in New Zealand red deer, but no association was found between this variation and selected muscle and growth traits.

Abstract

Myostatin (MSTN), also known as growth differentiation factor 8 (GDF-8), is a negative regulator of lean muscle tissue growth. Variation in the gene has been studied in many domesticated species, because of its potential to dramatically increase muscle mass. It has, however, not been investigated in red deer (Cervus elaphus). In this study, variation in MSTN intron 1 was investigated in 211 male New Zealand red deer, for which phenotypic measurements of M. Longissimus dorsi (eye muscle) (width, depth, and area, together with 12-month weight) were recorded. Two sequence variants (named A and B) differing by one nucleotide (c.373 + 224) were identified in the intron 1 region of the gene resulting in three genotypes (AA, AB, and BB; frequencies of 63.5%, 30.8%, and 5.7%, respectively), but no association between this variation and any of the quantitative measurements was detected. These results suggest that the deer MSTN is less variable than for other livestock species and that its activity may be controlled to maintain a size–growth equilibrium.

Optimized Cas9:sgRNA delivery efficiently generates biallelic MSTN knockout sheep without affecting meat quality

BACKGROUND

CRISPR/Cas9-based genome-editing systems have been used to efficiently engineer livestock species with precise genetic alterations intended for biomedical and agricultural applications. Previously, we have successfully generated gene-edited sheep and goats via one-cell-stage embryonic microinjection of a Cas9 mRNA and single-guide RNAs (sgRNAs) mixture. However, most gene-edited animals produced using this approach were heterozygotes. Additionally, non-homozygous gene-editing outcomes may not fully generate the desired phenotype in an efficient manner.

RESULTS

We report the optimization of a Cas9 mRNA-sgRNA delivery system to efficiently generate homozygous myostatin (MSTN) knockout sheep for improved growth and meat production. Firstly, an sgRNA selection software (sgRNAcas9) was used to preliminarily screen for highly efficient sgRNAs. Ten sgRNAs targeting the MSTN gene were selected and validated in vitro using sheep fibroblast cells. Four out of ten sgRNAs (two in exon 1 and two in exon 2) showed a targeting efficiency > 50%. To determine the optimal CRISPR/Cas9 microinjection concentration, four levels of Cas9 mRNA and three levels of sgRNAs in mixtures were injected into sheep embryos. Microinjection of 100 ng/μL Cas9 mRNA and 200 ng/μL sgRNAs resulted in the most improved targeting efficiency. Additionally, using both the highly efficient sgRNAs and the optimal microinjection concentration, MSTN-knockout sheep were generated with approximately 50% targeting efficiency, reaching a homozygous knockout efficiency of 25%. Growth rate and meat quality of MSTN-edited lambs were also investigated. MSTN-knockout lambs exhibited increased body weight and average daily gain. Moreover, pH, drip loss, intramuscular fat, crude protein, and shear force of gluteal muscles of MSTN-knockout lambs did not show changes compared to the wild-type lambs.

CONCLUSIONS

This study highlights the importance of in vitro evaluation for the optimization of sgRNAs and microinjection dosage of gene editing reagents. This approach enabled efficient engineering of homozygous knockout sheep. Additionally, this study confirms that MSTN-knockout lambs does not negatively impact meat quality, thus supporting the adoption of gene editing as tool to improve productivity of farm animals.

Developmental Profiling of Dietary Carbohydrate Digestion in Piglets

Carbohydrates are the main source of energy in the diet, accounting for the largest proportion in the diets of humans and monogastric animals. Although recent progress has been made in the study of intestinal carbohydrate digestion in piglets, there is a lack of comprehensive study on the dynamic changes in intestinal carbohydrate digestion with age in the early growth stage of piglets. To fill in this gap of knowledge, we collected samples of the small intestine, pancreatic tissues, and colonic digesta from 42 piglets during newborn [day (d) 0], lactation (d 7, 14), weaning (d 21), and nursery (d 28, 35, and 42) stages. Intestinal and pancreatic tissues and colonic digesta were collected at necropsy and analyzed for morphology, digestive enzyme activities, short-chain fatty acids (SCFA), and microbial abundance. Villus height reached a maximum at 1 week (d 7) in the duodenum and jejunum (P <0.01), and a higher ratio of villus height to crypt depth and lactase activity were observed on d 0 and 7 (P < 0.001) compared to other ages. However, the sucrase and maltase activities were increased with piglets' age. Similar activities of sucrase and maltase were found in the small intestine. In addition, amylase, lipase, and protease activities were assayed in the pancreas. The activity of amylase increased with age, while lipase and protease decreased gradually from birth to weaning (d 21, 28) and then increased after weaning (d 35, 42). Compared with d 0, d 42 increased the abundance of Firmicutes and Bacteroidetes with a higher concentration of total SCFA (P < 0.001) and decreased the abundance of Proteobacteria, but weaning (d 21, 28) increased the abundance of Proteobacteria in the colon. These results indicate that with the increase in piglet age, the carbohydrate digestive function gradually increased, but weaning hindered the development of intestinal function. These results provide us with new insights into the healthy development of piglets' intestines, which may help us to better regulate the physiological health of piglets in the future.

Effect of Myostatin Gene Mutation on Slaughtering Performance and Meat Quality in Marchigiana Bulls

Simple Summary

The aim of this work was the evaluation of slaughtering performance in a sample of 78 Marchigiana bulls with different allelic situation at the myostatin locus; in addition, the qualitative composition of meat samples collected from Longissimus thoracis muscle was evaluated. At the myostatin gene, 67 homozygotes normal, 11 heterozygotes, and no double-muscled homozygote bulls were detected. Heterozygote bulls showed high values in final live weight and dressing yield; moreover, they were characterized by a low incidence of fat at steak dissection, as well as in meat chemical composition. A better muscular conformation in heterozygote bulls’ carcasses was highlighted, with a higher incidence of their carcasses in class E and evident convexity of round, back, and shoulder muscular masses compared to the carcasses of Marchigiana bulls which were normal at the myostatin gene.

Abstract

The myostatin gene also called Growth Differentiation Factor 8 gene (GDF8) is one of the most investigated loci that can be responsible for several quantitative and qualitative carcass and meat traits in double-muscled beef cattle. The objective of the study was to bring to light the effect of the myostatin polymorphism on slaughtering performance and meat quality in Marchigiana beef cattle. The experiment was carried out on 78 bulls reared according to the “cow-calf” extensive managing system. At the end of the fattening period, in vivo and carcass data were recorded. From each carcass, a steak of Longissimus thoracis was taken and used to determine the meat’s analytical composition and colorimetric properties. Finally, from each steak a sample of Longissimus thoracis was collected, then used for DNA extraction and genotyping at the myostatin locus. The heterozygous bulls showed slight superiority in the carcass data (e.g., hot carcass weight: 426.09 kg—heterozygotes vs. 405.32 kg—normal) and meat quality parameters, although not always with statistical significance. Only fat and ashes content were significantly affected by the myostatin genotype (heterozygotes: 2.01%, 1.26%; normal: 3.04%, 1.15%). The greater muscularity of heterozygous animals compared to normal ones could be a starting point to improving productive efficiency in Marchigiana beef cattle.

Review: On-farm and processing factors affecting bovine carcass and meat quality

This paper reviews the current state of knowledge on beef carcass and meat quality, with particular emphasis on on-farm and processing factors associated with its high and inconsistent variability. The diversity of livestock systems comes from the diversity of breeds (dairy or beef), ages and gender (bulls, steers, heifers, cull cows) used to produce either mainly beef or beef and milk. In addition, there are factors linked to farming practices (including diet, especially grazing) which significantly influence the sensory, nutritional, technological and extrinsic (such as image) quality attributes of meat. These can become factors of positive differentiation when controlled by the application and certification of technical specifications. Finally, preslaughter (such as stress), slaughter (such as the chilling and hanging method of carcasses) and postslaughter (such as ageing, packaging and cooking) conditions have a strong influence on the microbiological, sensory, technological and image quality attributes of beef. In this review, potential synergisms or antagonisms between the different quality attributes are highlighted. For example, finishing cattle on grass, compared to indoor fattening on a high concentrate diet, has the advantage of producing leaner meat with a higher proportion of omega-3 fatty acids while exhibiting superior oxidative stability, but with the consequence of a darker meat colour and lower productivity, as well as higher seasonality and land surface requirements. Moreover, the control of on-farm factors is often guided by productivity (growth rate, feed conversion ratio) and carcass quality attributes (weight, conformation and fatness). Genetic selection has often been oriented in this direction, without taking other quality attributes into account. Finally, the interactions between all these factors (and especially between on-farm and slaughter or processing factors) are not considered in the quality grading schemes in European countries. This means that positive efforts at farm level may be mitigated or even eliminated by poor slaughtering or processing conditions. All these considerations explain why between-animal variability in quality can be high, even when animals come from the same farming system. The ability to predict the sensory and nutritional properties of meat according to production factors has become a major objective of the supply chain.

Genetic Variations and Haplotypic Diversity in the Myostatin Gene of Different Cattle Breeds in Russia

Simple Summary

This paper presents the results of the study of two polymorphisms of the myostatin gene associated with muscular hypertrophy in the Russian populations of Aberdeen Angus, Limousin, Simmental, and Belgian Blue cattle breeds. For their diagnostics, test systems based on modern molecular genetic methods were developed, and the population analysis showed a low frequency of the undesirable allele associated with the genetic defect of double-muscling, and a high frequency of the allele that presumably positively influences meat productivity traits.

Abstract

The myostatin gene (MSTN) in cattle has a number of polymorphisms associated with increased muscle mass. The aim of the current study was to determine the haplotype frequencies of F94L and nt821(del11) MSTN polymorphisms among cattle bred for meat in Russia, using DNA analysis. Using the earlier created test systems based on the AS-PCR and PCR-RFLP methods, six populations of Aberdeen Angus (n = 684), two populations of Limousin (n = 54), one population of Simmental (n = 55), and one population of Belgian Blue (n = 137) belonging to Russian farms were genotyped on nt821(del11) and F94LMSTN polymorphisms. The animal carriers of the mutant allele of nt821(del11)MSTN associated with the double-muscling genetic defect were found in one Aberdeen Angus population at a frequency of 2.18%, but were not found in the Limousin and Simmental populations. However, 100% of the Belgian Blue population were heterozygous carriers of nt821(del11)MSTN. The frequencies of the A allele F94LMSTN desirable for productivity traits in the Limousin populations were the highest and accounted for 0.97 and 1 in populations one and two, while in the Aberdeen Angus, Simmental, and Belgian Blue populations, these figures were considerably lower at 0.04–0.08, depending on the population. The obtained data show the high genetic potential of Russian beef cattle, and facilitate an improvement in meat productivity by preserving the health of animals.

HMEJ-mediated site-specific integration of a myostatin inhibitor increases skeletal muscle mass in porcine

As a robust antagonist of myostatin (MSTN), follistatin (FST) is an important regulator of skeletal muscle development, and the delivery of FST to muscle tissue represents a potential therapeutic strategy for muscular dystrophies. The N terminus and FSI domain of FST are the functional domains for MSTN binding. Here, we aimed to achieve site-specific integration of FSI-I-I, including the signal peptide, N terminus, and three FSI domains, into the last codon of the porcine MSTN gene using a homology-mediated end joining (HMEJ)-based strategy mediated by CRISPR-Cas9. Based on somatic cell nuclear transfer (SCNT) technology, we successfully obtained FSI-I-I knockin pigs. H&E staining of longissimus dorsi and gastrocnemius cross-sections showed larger myofiber sizes in FSI-I-I knockin pigs than in controls. Moreover, the Smad and Erk pathways were inhibited, whereas the PI3k/Akt pathway was activated in FSI-I-I knockin pigs. In addition, the levels of MyoD, Myf5, and MyoG transcription were upregulated while that of MRF4 was downregulated in FSI-I-I knockin pigs. These results indicate that the FSI-I-I gene mediates skeletal muscle hypertrophy through an MSTN-related signaling pathway and the expression of myogenic regulatory factors. Overall, FSI-I-I knockin pigs with hypertrophic muscle tissue hold great promise as a therapeutic model for human muscular dystrophies.

Detection of Genomic Regions with Pleiotropic Effects for Growth and Carcass Quality Traits in the Rubia Gallega Cattle Breed

Simple Summary

The breeding scheme in the Rubia Gallega cattle population is based upon traits measured in farms and slaughterhouses. We have developed a ssGWAS by backsolving the SNP effects after implementing a ssGBLUP. The results showed an apparent heterogeneity of the additive genetic variance across the genome. Some of the genomic regions explaining the most of this additive variance were shared across traits, indicating the presence of pleiotropic effects, which were reflected in their genetic correlations.

Abstract

The breeding scheme in the Rubia Gallega cattle population is based upon traits measured in farms and slaughterhouses. In recent years, genomic evaluation has been implemented by using a ssGBLUP (single-step Genomic Best Linear Unbiased Prediction). This procedure can reparameterized to perform ssGWAS (single-step Genome Wide Association Studies) by backsolving the SNP (single nucleotide polymorphisms) effects. Therefore, the objective of this study was to identify genomic regions associated with the genetic variability in growth and carcass quality traits. We implemented a ssGBLUP by using a database that included records for Birth Weight (BW-327,350 records-), Weaning Weight (WW-83,818-), Cold Carcass Weight (CCW-91,621-), Fatness (FAT-91,475-) and Conformation (CON-91,609-). The pedigree included 464,373 individuals, 2449 of which were genotyped. After a process of filtering, we ended up using 43,211 SNP markers. We used the GBLUP and SNPBLUP model equivalences to obtain the effects of the SNPs and then calculated the percentage of variance explained by the regions of the genome between 1 Mb. We identified 7 regions of the genome for CCW; 8 regions for BW, WW, FAT and 9 regions for CON, which explained the percentage of variance above 0.5%. Furthermore, a number of the genome regions had pleiotropic effects, located at: BTA1 (131–132 Mb), BTA2 (1–11 Mb), BTA3 (32–33 Mb), BTA6 (36–38 Mb), BTA16 (24–26 Mb), and BTA 21 (56–57 Mb). These regions contain, amongst others, the following candidate genes: NCK1, MSTN, KCNA3, LCORL, NCAPG, and RIN3.

Determination of the relationship between Anatolian black cattle growth properties and myostatin, GHR and Pit-1 gene

The aim of this study is to determine the relationship between some growth and development characteristics in Anatolian Black cattle from birth to twelve months of age with the Pit-1, GHR and Myostatin genes. PCR-RFLP method was used to detect the polymorphism. Genotype and allele frequencies were found to be AA/AB/BB: 0.096/0.519/0.385 and A/B: 0.356/0.644; AA/AG/GG: 0.346/0.385/0.269 and A/G: 0.538/0.462 in the Pit-1 and GHR genes respectively. Myostatin gene was found to be also monomorphic in all genotypes. Although the chi-square χ² test in the Pit-1 gene showed an agreement to Hardy-Weinberg equilibrium (p > 0.05), in the GHR gene did not showed an agreement (p < 0.05). The results of the statistical analysis indicated an association between Pit-1 and GHR genes polymorphism and growth traits at different stage ages in Anatolian Black cattle. But Pit-1/HinfI gene and GHR/Alul polymorphisms were not found statistically significant in the specified periods, at all characters. On the other hand, since the MSTN/BstF5I gene was found to be monomorphic, no association analysis was performed between the measured values and this gene. In conclusion, mutation of these genes is difficult to suggest as a potential marker in a herd selection regarding the growth and development characteristics.

Reproduction traits of heterozygous myostatin knockout sows crossbred with homozygous myostatin knockout boars

Few studies exist on homozygous myostatin gene mutant (MSTN^-/- ) pigs, especially on their reproductive ability. We have previously shown that semen quality of homozygous MSTN^-/- boars is comparable to that of wild type (WT). However, no data exist on the reproductive ability of heterozygous MSTN gene mutant (MSTN^{+/ -} ) sows. The present study highlights showed that the heterozygous MSTN^{+/ -} sows have delayed pubertal age than WT sows (255.80 ± 6.79 versus 191.10 ± 3.42, respectively). The number of services per pregnancy of heterozygous MSTN^{+/ -} sows is significantly higher than that of WT sows (3.33 ± 0.43 versus 1.60 ± 0.25, respectively). Moreover, although heterozygous MSTN^{+/ -} sows have natural reproduction ability, their litter size was significantly lower than that of WT sows (7.75 ± 0.44 versus 14.25 ± 0.60, respectively). Offsprings generated from heterozygous MSTN^{+/ -} sow and homozygous MSTN^-/- boar were genotyped with the PCR and sequencing method to detect myostatin mutation and to identify whether the piglets are homozygous MSTN^-/- or heterozygous MSTN^{+/ -} . The proportion of homozygous MSTN^-/- piglets was significantly lower than that of heterozygous MSTN^{+/ -} piglets (2.50 ± 0.35 versus 5.25 ± 0.60, respectively). Furthermore, none of the sows presented dystocia, and the phenotype of heterozygous MSTN^{+/ -} piglets was normal. However, 10% homozygous MSTN^-/- piglets died of dyspnoea within 2 hr after birth, 60% of homozygous MSTN^-/- piglets showed large tongues, and 50% had umbilical hernias. In summary, this study for the first time reports the reproduction traits of heterozygous MSTN^{+/ -} sows crossbred with homozygous MSTN^-/- boars. This study will pave the way in a new direction for the breeding and development of super lean meat varieties in the future.

Associations of CAST, CAPN1 and MSTN Genes Polymorphism with Slaughter Value and Beef Quality – A Review

The slaughter value of cattle and beef quality are influenced by many factors, which can generally be divided into antemortem (breed, sex, age, housing system, diet, pre-slaughter handling) and postmortem (post-slaughter processing, chilling temperature, packaging). Studies of many authors have shown that meat quality traits can be also influenced by the individual genetic background of an animal. Numerous studies have been conducted worldwide to determine the functions of various genes as well as polymorphisms with potential effects on fattening and slaughter value of cattle and on beef quality. This study reviews the most important research done on the associations of polymorphisms in the calpain, calpastatin and myostatin genes with carcass traits and beef quality. Knowledge about the genes and chromosome regions associated with desired meat quality characteristics may prove very helpful when selecting pairs for mating and estimating the breeding value of offspring, mainly because it is difficult to improve meat quality traits based on conventional selection methods due to their low heritability and polygenic regulation. Furthermore, meat quality evaluation is expensive and can only be carried out after slaughter.

Genome-Wide Association Study of Weaning Traits in Lori-Bakhtiari Sheep

Weaning traits, including preweaning daily gain (PWDG) and weaning weight (WW) are important economic traits, especially for meat type mammals, with high impacts on growth performance and survival rate in higher ages. This study was conducted to perform a genome-wide association study (GWAS) on weaning traits in a meat type breed of sheep. Body weight records of 7557 Lori-Bakhtiari sheep with PWDG and WW records were used to estimate breeding values (EBVs) using an animal mixed model. A total of 132 animals were selected by two-tailed selection strategy, based on EBVs for body weight and then were genotyped using Illumina 50k Ovine SNP chip. After quality control, a total of 130 animals and 41323 SNPs were remained for further analyses. De-regressed estimates of breeding values were used as a pseudo-phenotype in GWAS analysis. Based on Bonferroni-adjusted p-values, five SNPs, located on chromosomes 2, 3, 4, 12 and 22 were significantly (p < 0.05) associated with weaning traits and accounted for 5.06% and 0.37% of total genetic variations of PWDG and WW, respectively. Two SNPs on chromosomes 2 and 3 were located near to previously reported QTLs for weaning traits. Three genes, including ANGPTL7, mTOR and WDR11, were found within 50 kbp distances from the significant SNPs and thus could be considered as candidate genes for weaning traits. The detected QTLs and candidate genes could be studied for construction of breeding programs for genetic improvement of growth performance in meat type sheep.

Breed- and trait-specific associations define the genetic architecture of calving performance traits in cattle

Reducing the incidence of both the degree of assistance required at calving, as well as the extent of perinatal mortality (PM) has both economic and societal benefits. The existence of heritable genetic variability in both traits signifies the presence of underlying genomic variability. The objective of the present study was to locate regions of the genome, and by extension putative genes and mutations, that are likely to be underpinning the genetic variability in direct calving difficulty (DCD), maternal calving difficulty (MCD), and PM. Imputed whole-genome single-nucleotide polymorphism (SNP) data on up to 8,304 Angus (AA), 17,175 Charolais (CH), 16,794 Limousin (LM), and 18,474 Holstein-Friesian (HF) sires representing 5,866,712 calving events from descendants were used. Several putative quantitative trait loci (QTL) regions associated with calving performance both within and across dairy and beef breeds were identified, although the majority were both breed- and trait-specific. QTL surrounding and encompassing the myostatin (MSTN) gene were associated (P < 5 × 10⁻⁸) with DCD and PM in both the CH and LM populations. The well-known Q204X mutation was the fifth strongest association with DCD in the CH population and accounted for 5.09% of the genetic variance in DCD. In contrast, none of the 259 segregating variants in MSTN were associated (P > × 10⁻⁶) with DCD in the LM population but a genomic region 617 kb downstream of MSTN was associated (P < 5 × 10⁻⁸). The genetic architecture for DCD differed in the HF population relative to the CH and LM, where two QTL encompassing ZNF613 on Bos taurus autosome (BTA)18 and PLAG1 on BTA14 were identified in the former. Pleiotropic SNP associated with all three calving performance traits were also identified in the three beef breeds; 5 SNP were pleiotropic in AA, 116 in LM, and 882 in CH but no SNP was associated with more than one trait within the HF population. The majority of these pleiotropic SNP were on BTA2 surrounding MSTN and were associated with both DCD and PM. Multiple previously reported, but also novel QTL, associated with calving performance were detected in this large study. These also included QTL regions harboring SNP with the same direction of allele substitution effect for both DCD and MCD thus contributing to a more effective simultaneous selection for both traits.

Genetically Modified Babies and a First Application of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR-Cas9)

The world's first babies with CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats)-edited genes were born on November 25, 2018. Dr. Jiankui He of Southern University of Science and Technology in Shenzhen performed this gene editing. Dr. He's objectives and an assessment of how well they were achieved are discussed in the context of existing research in this area.

Identification of two novel single nucleotide polymorphism sites in the Myostatin (MSTN) gene and their association with carcass traits in meat-type rabbits (Oryctolagus cuniculus)

<p>Two unknown single nucleotide polymorphism (SNP) sites in exons 1 (c.194C&gt;T) and 2 (c.445T&gt;A) of meat-type rabbit <em>MSTN</em> gene were identified in the study. Our objective was to analyse the population genetics structure of the two novel SNP sites in 230 individuals from six breeds and their associations with carcass traits of rabbits. We found that live body weight (BW), cold carcass weight (CCW), reference carcass weight (RCW), CCW percentage (P_CCW) and RCW percentage (P_RCW) of the rabbits with the genotype CC at the c.194C&gt;T of exon 1 or AA at the c.445T&gt;A of exon 2 were significantly higher than those with other genotypes. Diplotype significantly affected BW, RCW, CCW, P_RCW (<em>P</em>&lt;0.01) and P_CCW and P_CM (<em>P</em>&lt;0.05). CC/AA was the advantageous diplotype for BW, RCW, CCW and P_CM, and TT/AA was the advantageous diplotype for P_CCW and P_RCW. In contrast, TT/TT was the negative diplotype for BW, CCW, RCW, P_CCW and P_RCW, and TT/AA was the negative diplotype for P_CM. The results suggest that the two new mutations of <em>MSTN</em> gene significantly affected BW, CCW, RCW, P_CCW and P_RCW of rabbits, and <em>MSTN</em> may be an important candidate gene of carcass traits in meat-type rabbits.</p>

Genetic parameters and genome-wide association study regarding feed efficiency and slaughter traits in Charolais cows

Residual energy intake (REI) on two successive diets (hay and maize based) and slaughter traits, including visceral organs, were phenotyped in 584 adult purebred Charolais cows. To investigate the relationships between these traits and their genetic determinism, we first estimated the genetic parameters, including correlations, using REML modeling under WOMBAT software. The animals were then genotyped on the BovineSNP50 SNPchip before being imputed to the 600K density and genome wide association study was performed with GCTA software. We found low heritability for REI (h2 = 0.12 in each of the diet phases). Although the phenotypic correlation between the two diet phases was moderate (0.36), the genetic correlation was high (0.83), indicating a common genetic determinism for feed efficiency regardless of the diet. Correlations between REI and slaughter traits were negative regarding muscle-related traits and positive for fat-related traits, indicating that efficient animals generally had a more muscular carcass. It was also seen that feed efficiency was genetically and phenotypically correlated with smaller organs when expressed as a proportion of their empty body weight. From the GWAS analysis, seven QTLs were found to be associated with a trait at the genome-wide level of significance and 18 others at the chromosome-wide level. One important QTL was detected in BTA 2, reflecting the essential effect of the myostatin gene on both carcass composition and relative organ weight. Three QTLs were detected for REI during the maize diet phase on BTA 13, 19, and 28, the latter being significant at the genome-wide level. The QTLs on BTA 19 mapped into the TANC2 gene and the QTLs on BTA 28 into the KIF1BP gene, which are both known to interact with the same protein (KIF1A). However, no obvious functional link between these genes and feed efficiency could be made. Among the other QTLs detected, one association on BTA 4 with liver proportion mapped to the candidate gene WASL, which has previously been shown to be differentially expressed in liver cells and linked to feed restriction or cancer development. No QTLs were found to be common between feed efficiency and any slaughter traits.

Novel report on mutation in exon 3 of myostatin (MSTN) gene in Nilagiri sheep: an endangered breed of South India

The variability in breeding program leads to rapid loss of genetic potential for which National Bureau of Animal Genetic Resources is emphasized to conserve the indigenous breeds. The variation in myostatin (MSTN) gene and its association with growth traits will throw light on its potential use as marker in selection. Hence, the study was conducted to detect polymorphism in exon 3 of MSTN, one of the most important growth regulatory gene and its association with growth in Nilagiri sheep breed. Blood samples were collected from Nilagiri sheep (n = 103) of South India and growth data up to 1 year of age was recorded. Genomic DNA was isolated and amplified for part of MSTN gene; PCR products were genotyped by restriction digestion (MspI) and confirmed by sequencing. Restriction digestion has revealed a single nucleotide polymorphism at locus G5622C in exon 3 which was confirmed by sequencing. The wild-type DNA molecule (MM) cleaved by MspI produced 301-bp and 314-bp fragments and those with mutation (mm) would remain undigested. The genotypic frequencies were MM (0.689) and Mm (0.311) with complete absence of mm genotype; and allelic frequencies were M (0.8445) and m (0.1555). The locus was in Hardy-Weinberg equilibrium. The association analysis revealed that there was no significant difference in mean birth, weaning, 6-, 9-, and 12-month weight between MM and Mm genotypes at g.5622G>C locus of exon 3 of MSTN gene. This is the first report of mutation in exon 3 of MSTN gene. The non-significant effect and absence of mm genotype at this locus needs further studies based on large population size and haplotype analysis.

Balancing selection at a premature stop mutation in the myostatin gene underlies a recessive leg weakness syndrome in pigs

Balancing selection provides a plausible explanation for the maintenance of deleterious alleles at moderate frequency in livestock, including lethal recessives exhibiting heterozygous advantage in carriers. In the current study, a leg weakness syndrome causing mortality of piglets in a commercial line showed monogenic recessive inheritance, and a region on chromosome 15 associated with the syndrome was identified by homozygosity mapping. Whole genome resequencing of cases and controls identified a mutation causing a premature stop codon within exon 3 of the porcine Myostatin (MSTN) gene, similar to those causing a double-muscling phenotype observed in several mammalian species. The MSTN mutation was in Hardy-Weinberg equilibrium in the population at birth, but significantly distorted amongst animals still in the herd at 110 kg, due to an absence of homozygous mutant genotypes. In heterozygous form, the MSTN mutation was associated with a major increase in muscle depth and decrease in fat depth, suggesting that the deleterious allele was maintained at moderate frequency due to heterozygous advantage (allele frequency, q = 0.22). Knockout of the porcine MSTN by gene editing has previously been linked to problems of low piglet survival and lameness. This MSTN mutation is an example of putative balancing selection in livestock, providing a plausible explanation for the lack of disrupting MSTN mutations in pigs despite many generations of selection for lean growth.

Tendon healing in the context of complex fractures

Tendons connect muscle to bone and play an integral role in bone and joint alignment and loading. Tendons act as pulleys that provide anchorage of muscle forces for joint motion and stability, as well as for fracture reduction and realignment. Patients that experience complex fractures also have concomitant soft tissue injuries, such as tendon damage or rupture. Tendon injuries that occur at the time of bone fracture have long-term ramifications on musculoskeletal health, yet these injuries are often disregarded in clinical treatment and diagnosis for patients with bone fractures as well as in basic science approaches for understanding bone repair processes. Delayed assessment of soft tissue injuries during evaluation of trauma can lead to chronic pain, dysfunction, and delayed bone healing even following successful fracture repair, highlighting the importance of identifying and treating damaged tendons early. Treatment strategies for bone repair, such as mechanical stabilization and biological therapeutics, can impact tendon healing and function. Because poor tendon healing following complex fracture can significantly impact the function of tendon during bone fracture healing, a need exists to understand the healing process of complex fractures more broadly, beyond the healing of bone. In this review, we explored the mechanical and biological interaction of bone and tendon in the context of complex fracture, as well as the relevance and potential ramifications of tendon damage following bone fracture, which has particular impact on patients that experience complex fractures, such as from combat, automobile accidents, and other trauma.

Effects of galacto-oligosaccharides on growth and gut function of newborn suckling piglets

Background

Most research on galacto-oligosaccharides (GOS) has mainly focused on their prebiotic effects on the hindgut, but their beneficial effects on the small intestine (SI) have received little attention. Since jejunum is the important place to digest and absorb nutrients efficiently, optimal maturation of the jejunum is necessary for maintaining the high growth rate in the neonate. Therefore, this study investigates the effect of the early intervention with GOS on the intestinal development of the jejunum.

Methods

A total of 6 litters of neonatal piglets (10 piglets per litter; Duroc × Landrace × Large White) with an average birth weight of 1.55 ± 0.05 kg received 1 of 2 treatments based on their assignment to either the control (CON) group or the GOS (GOS) group in each litter. Piglets in the GOS group were orally administrated 10 mL of a GOS solution (reaching 1 g GOS/kg body weight) per day from the age of 1 to 7 d; the piglets in the CON group were treated with the same dose of physiological saline. All piglets were weaned on d 21. On d 8 and 21 of the experimental trial, 1 pig per group from each of the 6 litters was euthanized.

Results

The early intervention with GOS increased the average daily gains in the third week (P < 0.05). Decreased crypt depth was also observed in the jejunum of the piglets on d 21 (P < 0.05). The early intervention with GOS increased the jejunal lactase activity on d 8, maltase activity and sucrase activity on d 21 (P < 0.05). In addition, the early intervention with GOS also facilitated the mRNA expression of Sodium glucose co-transporter 1 (SGLT1) on d 8 and the mRNA expression of Glucose transporter type 2 (GLUT2) on d 21 (P < 0.05). It was further determined that GOS up-regulated the mRNA expression of preproglucagon (GCG), insulin-like growth factor 1 (IGF-1), insulin-like growth factor 1 receptor (IGF-1R) and epidermal growth factor (EGF). GOS also up-regulated the protein expression of glucagon-like peptide-2 (GLP-2) and EGF in the jejunum of the piglets. Furthermore, it was also found that GOS enhanced the protein expression of ZO-1 and occludin on d 8 (P < 0.05), as well as increased the mRNA expression of TGF-β and decrease the mRNA expression of IL-12 (P < 0.05).

Conclusions

These results indicate that GOS have a positive effect on piglet growth performance in addition to decreasing the crypt depth and enhancing functional development in jejunum of suckling piglets.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0290-9) contains supplementary material, which is available to authorized users.

Mapping QTL for white striping in relation to breast muscle yield and meat quality traits in broiler chickens

Background

White striping (WS) is an emerging muscular defect occurring on breast and thigh muscles of broiler chickens. It is characterized by the presence of white striations parallel to the muscle fibers and has significant consequences for meat quality. The etiology of WS remains poorly understood, even if previous studies demonstrated that the defect prevalence is related to broiler growth and muscle development. Moreover, recent studies showed moderate to high heritability values of WS, which emphasized the role of genetics in the expression of the muscle defect. The aim of this study was to identify the first quantitative trait loci (QTLs) for WS as well as breast muscle yield (BMY) and meat quality traits using a genome-wide association study (GWAS). We took advantage of two divergent lines of chickens selected for meat quality through Pectoralis major ultimate pH (pHu) and which exhibit the muscular defect. An expression QTL (eQTL) detection was further performed for some candidate genes, either suggested by GWAS analysis or based on their biological function.

Results

Forty-two single nucleotide polymorphisms (SNPs) associated with WS and other meat quality traits were identified. They defined 18 QTL regions located on 13 chromosomes. These results supported a polygenic inheritance of the studied traits and highlighted a few pleiotropic regions. A set of 16 positional and/or functional candidate genes was designed for further eQTL detection. A total of 132 SNPs were associated with molecular phenotypes and defined 21 eQTL regions located on 16 chromosomes. Interestingly, several co-localizations between QTL and eQTL regions were observed which could suggest causative genes and gene networks involved in the variability of meat quality traits and BMY.

Conclusions

The QTL mapping carried out in the current study for WS did not support the existence of a major gene, but rather suggested a polygenic inheritance of the defect and of other studied meat quality traits. We identified several candidate genes involved in muscle metabolism and structure and in muscular dystrophies. The eQTL analyses showed that they were part of molecular networks associated with WS and meat quality phenotypes and suggested a few putative causative genes.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4598-9) contains supplementary material, which is available to authorized users.

Selection for increased muscling is not detrimental to maternal productivity traits in Angus cows

The aim of the present study was to assess the effect of selection for increased muscling on maternal productivity of a temperate beef cow herd. Cows of predominantly Angus breeding were selected using visual muscle score (1–15 scale, where 1 = lightest and 15 = heaviest muscling) into low- and high-muscled animals, and mated to Angus bulls with low or high muscularity. Initially, low-muscled cows were mated to low-muscled bulls to create the Low line, and high-muscled bulls and cows were mated to create the High line. On discovering that some High cattle carried the myostatin (821 del11) gene, a second High line was created to distinguish between cattle with no copies of the myostatin gene (High line) and those with one copy (HighHet line). Data from 12 breeding cycles, consisting of 2003 joining records, and 1713 resulting weaning records were analysed to assess maternal productivity. Cows from the three lines were similar in weight (547, 548 and 550 kg, P = 0.9), but varied in body composition – from Low to High to HighHet cows, muscling traits increased and fatness traits decreased (all P < 0.001). Compared with Low cows, High cows had a 4.4 units higher muscle score, 10% higher eye muscle area and 21% less fat, and HighHet cows had a 7.1 units higher muscle score, 17% higher eye muscle area and 45% less fat. There were no significant effects of selection for increased muscling on live birth or weaning rates, or weaning weight (all P > 0.1). Dystocia levels of Low and HighHet maidens or cows did not differ significantly, but High maidens or cows had less dystocia (P = 0.013). Low, High and HighHet cows weaned 218, 225 and 216 kg of calf/cow joined.year, indicating similar maternal productivity.

Molecular Cloning, Identification, and Expression Patterns of Myostatin Gene in Water Buffalo (Bubalus Bubalis)

Myostatin (MSTN), also named growth differentiation factor 8 (GDF8), is a transforming growth factor-β (TGF-β) family member with a key role in the negative regulation of skeletal muscle growth. However, its role in ovarian folliculogenesis remains unclear. To provide us with a basis for understanding this role, we cloned MSTN and examined its expression patterns in water buffalo (Bubalus bubalis). The complete ORF of the water buffalo MSTN gene is 1,128 nucleotides, which encode a 375 amino acid protein and sharing 99% identity at the deducted amino acid level with that of Bos taurus. Protein sequence analysis showed that MSTN is a weakly acerbic extracellular protein, consisting of signal peptides at 18-19 sites, a TGF-β propeptide, and a TGF-β domain. RT-PCR analyses demonstrated that water buffalo MSTN was expressed in multiple tissues but not limited to muscle. Immunohistochemistry staining confirmed the presence of MSTN in oocytes and granulosal cells. To our knowledge, this is the first study to confirm the expression of MSTN in the water buffalo ovary, suggesting an additional role of MSTN in water buffalo folliculogenesis, along with its role in skeletal muscle growth regulation. Further study of the regulatory mechanism of MSTN in water buffalo reproduction is warranted.

ABBREVIATIONS

MSTN, myostatin; ORF, open reading frame.

Genomic differentiation between Asturiana de los Valles, Avileña-Negra Ibérica, Bruna dels Pirineus, Morucha, Pirenaica, Retinta and Rubia Gallega cattle breeds

The Spanish local beef cattle breeds have most likely common origin followed by a process of differentiation. This particular historical evolution has most probably left detectable signatures in the genome. The objective of this study was to identify genomic regions associated with differentiation processes in seven Spanish autochthonous populations (Asturiana de los Valles (AV), Avileña-Negra Ibérica (ANI), Bruna dels Pirineus (BP), Morucha (Mo), Pirenaica (Pi), Retinta (Re) and Rubia Gallega (RG)). The BovineHD 777K BeadChip was used on 342 individuals (AV, n=50; ANI, n=48; BP, n=50; Mo, n=50; Pi, n=48; Re, n=48; RG, n=48) chosen to be as unrelated as possible. We calculated the fixation index (F ST ) and performed a Bayesian analysis named SelEstim. The output of both procedures was very similar, although the Bayesian analysis provided a richer inference and allowed us to calculate significance thresholds by generating a pseudo-observed data set from the estimated posterior distributions. We identified a very large number of genomic regions, but when a very restrictive significance threshold was applied these regions were reduced to only 10. Among them, four regions can be highlighted because they comprised a large number of single nucleotide polymorphisms and showed extremely high signals (Kullback-Leiber divergence (KLD)>6). They are located in BTA 2 (5 575 950 to 10 152 228 base pairs (bp)), BTA 5 (17 596 734 to 18 850 702 bp), BTA 6 (37 853 912 to 39 441 548 bp) and BTA 18 (13 345 515 to 15 243 838 bp) and harbor, among others, the MSTN (Myostatin), KIT-LG (KIT Ligand), LAP3 (leucine aminopeptidase 3), NAPCG (non-SMC condensing I complex, subunit G), LCORL (ligand dependent nuclear receptor corepressor-like) and MC1R (Melanocortin 1 receptor) genes. Knowledge on these genomic regions allows to identify potential targets of recent selection and helps to define potential candidate genes associated with traits of interest, such as coat color, muscle development, fertility, growth, carcass and immunological response.

Genetic disorders in beef cattle: a review

The main purpose of present review is to describe and organize autosomal recessive disorders (arachnomelia, syndactylism, osteopetrosis, dwarfism, crooked tail syndrome, muscular hyperplasia, glycogen storage disease, protoporphyria), which occur among beef cattle, and methods that can be applied to detect these defects. Prevalence of adverse alleles in beef breeds happens due to human activity—selections of favorable features, e.g. developed muscle tissue. Unfortunately, carriers of autosomal recessive diseases are often characterized by these attributes. Fast and effective identification of individuals, that may carry faulty genes, can prevent economical losses.

Gene Expression and Polymorphism of Myostatin Gene and its Association with Growth Traits in Chicken

Myostatin is a member of TGF-β super family and is directly involved in regulation of body growth through limiting muscular growth. A study was carried out in three chicken lines to identify the polymorphism in the coding region of the myostatin gene through SSCP and DNA sequencing. A total of 12 haplotypes were observed in myostatin coding region of chicken. Significant associations between haplogroups with body weight at day 1, 14, 28, and 42 days, and carcass traits at 42 days were observed across the lines. It is concluded that the coding region of myostatin gene was polymorphic, with varied levels of expression among lines and had significant effects on growth traits. The expression of MSTN gene varied during embryonic and post hatch development stage.

The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs

Follistatin (FST), which was first found in the follicles of cattle and pigs, has been shown to be an essential regulator for muscle development. Mice that were genetically engineered to overexpress Fst specifically in muscle had at least twice the amount of skeletal muscle mass as controls; these findings are similar to earlier results obtained in myostatin-knockout mice. However, the role of follistatin in skeletal muscle development has yet to be clarified in livestock. Here, we describe transgenic Duroc pigs that exogenously express Fst specifically in muscle tissue. The transgenic pigs exhibited an increased proportion of skeletal muscle and a reduced proportion of body fat that were similar to those reported in myostatin-null cattle. The lean percentage of lean meat was significantly higher in the F1 generation of TG pigs (72.95 ± 1.0 %) than in WT pigs (69.18 ± 0.97 %) (N = 16, P < 0.05). Myofiber hypertrophy was also observed in the longissimus dorsi of transgenic pigs, possibly contributing to the increased skeletal muscle mass. Western blot analysis showed a significantly reduced level of Smad2 phosphorylation and an increased level of Akt^S473 phosphorylation in the skeletal muscle tissue of the transgenic pigs. Moreover, no cardiac muscle hypertrophy or reproductive abnormality was observed. These findings indicate that muscle-specific Fst overexpression in pigs enhances skeletal muscle growth, at least partly due to myofiber hypertrophy and providing a promising approach to increase muscle mass in pigs and other livestock.

Correlating single nucleotide polymorphisms in the myostatin gene with performance traits in rabbit

The Myostatin (MSTN), or Growth and Differentiation Factor 8 (GDF8), gene has been implicated in the double muscling phenomenon, in which a series of mutations render the gene inactive and unable to properly regulate muscle fibre deposition. Single nucleotide polymorphisms (SNPs) in the MSTN gene have been correlated to production traits, making it a candidate target gene to enhance livestock and fowl productivity. This study aimed to assess any association of three SNPs in the rabbit MSTN gene (c.713T&gt;A in exon 2, c.747+34C&gt;T in intron 2, and c.*194A&gt;G in 3’-untranslated region) and their combinations, with carcass, production and reproductive traits. The investigated traits included individual body weight, daily body weight gain, carcass traits and reproductive traits. The 3 SNPs were screened using PCR-restriction fragment length polymorphism (RFLP)-based analysis and the effects of the different SNP genotypes and their combinations were estimated in a rabbit population. Additionally, additive and dominance effects were estimated for significant traits. The results found no significant association between the c.713 T&gt;A SNP and all the examined traits. Allele T at the c.747+34C&gt;T SNP was only significantly associated (P&lt;0.05) with increased body weight at 12 wk of age. However, for the SNP residing in the 3’ untranslated region (c.*194A&gt;G), allele G was significantly associated (P&lt;0.05) with increased body weight and high growth rate. Genotype GG at the c.*194A&gt;G SNP also had positive effects on most carcass traits. The estimated additive genetic effect for the c.*194A&gt;G SNP was significant (P&lt;0.05) with most body weight, daily gain and carcass traits. No significant association was obtained between any MSTN SNPs and reproductive traits. In the combinations analysis, regardless of the genotypes of SNPs at c.713T&gt;A and c.747+34C&gt;T, GG at the c.*194A&gt;G SNP correlated with highest values in body weight and daily weight gain. In conclusion, the ‘G’ allele at the c.*194A&gt;G SNP had positive effects on growth and carcass traits and so could be used as a favourable allele in planning rabbit selection. Further population-wide studies are necessary to test the association of the c.*194A&gt;G SNP with carcass traits. We also recommend evaluation of the potential effects of the c.*194A&gt;G SNP on MSTN gene expression.

Transcriptome Profile Analysis of Breast Muscle Tissues from High or Low Levels of Atmospheric Ammonia Exposed Broilers (Gallus gallus)

Atmospheric ammonia is a common problem in poultry industry. High concentrations of aerial ammonia cause great harm to broilers' health and production. For the consideration of human health, the limit exposure concentration of ammonia in houses is set at 25 ppm. Previous reports have shown that 25 ppm is still detrimental to livestock, especially the gastrointestinal tract and respiratory tract, but the negative relationship between ammonia exposure and the tissue of breast muscle of broilers is still unknown. In the present study, 25 ppm ammonia in poultry houses was found to lower slaughter performance and breast yield. Then, high-throughput RNA sequencing was utilized to identify differentially expressed genes in breast muscle of broiler chickens exposed to high (25 ppm) or low (3 ppm) levels of atmospheric ammonia. The transcriptome analysis showed that 163 genes (fold change ≥ 2 or ≤ 0.5; P-value < 0.05) were differentially expressed between Ammonia25 (treatment group) and Ammonia3 (control group), including 96 down-regulated and 67 up-regulated genes. qRT-PCR analysis validated the transcriptomic results of RNA sequencing. Gene Ontology (GO) functional annotation analysis revealed potential genes, processes and pathways with putative involvement in growth and development inhibition of breast muscle in broilers caused by aerial ammonia exposure. This study facilitates understanding of the genetic architecture of the chicken breast muscle transcriptome, and has identified candidate genes for breast muscle response to atmospheric ammonia exposure.

Molecular characterization of exon 3 of caprine myostatin gene in Marwari goat

AIM

To estimate genetic variability in exon 3 of caprine myostatin gene in Marwari goats.

MATERIALS AND METHODS

A total of 120 blood samples from unrelated Marwari goats were randomly collected from different villages of Bikaner (Rajasthan), India. Genomic DNA was extracted from whole blood using blood DNA isolation kit (Himedia Ltd.) as per manufacturer's protocol. The quality of extracted genomic DNA was checked on 0.8% agarose gel. Specifically designed a primer set for caprine myostatin (MSTN) gene (Genebank accession no. DQ167575) was used to amplify the exon 3 region of MSTN gene in Marwari goat. The genetic variability in exon 3 of MSTN gene in Marwari goat was assessed on 8% polyacrylamide gel electrophoresis to detect single strand conformation polymorphism (SSCP) pattern.

RESULTS

The exon 3 of MSTN gene in Marwari goat showed two types of conformation patterns on 8% polyacrylamide gel. One of the patterns showed only two bands and was considered as genotype AA, whereas another pattern having an extra band was designated as genotype AB. The frequencies of AA and AB genotype for exon 3 region of MSTN gene were calculated as 0.90 and 0.10, respectively.

CONCLUSION

Low level of polymorphism was observed at exon 3 region of MSTN gene in Marwari goat through SSCP analysis. This information could be utilized in future breeding plan to exploit the unique characteristics of Marwari goat of Rajasthan.

Efficient Generation of Myostatin Mutations in Pigs Using the CRISPR/Cas9 System

Genetically modified pigs are increasingly used for biomedical and agricultural applications. The efficient CRISPR/Cas9 gene editing system holds great promise for the generation of gene-targeting pigs without selection marker genes. In this study, we aimed to disrupt the porcine myostatin (MSTN) gene, which functions as a negative regulator of muscle growth. The transfection efficiency of porcine fetal fibroblasts (PFFs) was improved to facilitate the targeting of Cas9/gRNA. We also demonstrated that Cas9/gRNA can induce non-homologous end-joining (NHEJ), long fragment deletions/inversions and homology-directed repair (HDR) at the MSTN locus of PFFs. Single-cell MSTN knockout colonies were used to generate cloned pigs via somatic cell nuclear transfer (SCNT), which resulted in 8 marker-gene-free cloned pigs with biallelic mutations. Some of the piglets showed obvious intermuscular grooves and enlarged tongues, which are characteristic of the double muscling (DM) phenotype. The protein level of MSTN was decreased in the mutant cloned pigs compared with the wild-type controls, and the mRNA levels of MSTN and related signaling pathway factors were also analyzed. Finally, we carefully assessed off-target mutations in the cloned pigs. The gene editing platform used in this study can efficiently generate genetically modified pigs with biological safety.

Targeted mutations in myostatin by zinc-finger nucleases result in double-muscled phenotype in Meishan pigs

Myostatin (MSTN) is a dominant inhibitor of skeletal muscle development and growth. Mutations in MSTN gene can lead to muscle hypertrophy or double-muscled (DM) phenotype in cattle, sheep, dog and human. However, there has not been reported significant muscle phenotypes in pigs in association with MSTN mutations. Pigs are an important source of meat production, as well as serve as a preferred animal model for the studies of human disease. To study the impacts of MSTN mutations on skeletal muscle growth in pigs, we generated MSTN-mutant Meishan pigs with no marker gene via zinc finger nucleases (ZFN) technology. The MSTN-mutant pigs developed and grew normally, had increased muscle mass with decreased fat accumulation compared with wild type pigs, and homozygote MSTN mutant (MSTN^−/−) pigs had apparent DM phenotype, and individual muscle mass increased by 100% over their wild-type controls (MSTN^+/+) at eight months of age as a result of myofiber hyperplasia. Interestingly, 20% MSTN-mutant pigs had one extra thoracic vertebra. The MSTN-mutant pigs will not only offer a way of fast genetic improvement of lean meat for local fat-type indigenous pig breeds, but also serve as an important large animal model for biomedical studies of musculoskeletal formation, development and diseases.

Stable suppression of myostatin gene expression in goat fetal fibroblast cells by lentiviral vector-mediated RNAi

Myostatin (MSTN) is a secreted growth factor that negatively regulates skeletal muscle mass, and therefore, strategies to block myostatin-signaling pathway have been extensively pursued to increase the muscle mass in livestock. Here, we report a lentiviral vector-based delivery of shRNA to disrupt myostatin expression into goat fetal fibroblasts (GFFs) that were commonly used as karyoplast donors in somatic-cell nuclear transfer (SCNT) studies. Sh-RNA positive cells were screened by puromycin selection. Using real-time polymerase chain reaction (PCR), we demonstrated efficient knockdown of endogenous myostatin mRNA with 64% down-regulation in sh2 shRNA-treated GFF cells compared to GFF cells treated by control lentivirus without shRNA. Moreover, we have also demonstrated both the induction of interferon response and the expression of genes regulating myogenesis in GFF cells. The results indicate that myostatin-targeting siRNA produced endogenously could efficiently down-regulate myostatin expression. Therefore, targeted knockdown of the MSTN gene using lentivirus-mediated shRNA transgenics would facilitate customized cell engineering, allowing potential use in the establishment of stable cell lines to produce genetically engineered animals.

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

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

The Application of Genomic Technologies to Investigate the Inheritance of Economically Important Traits in Goats

Goat genomics has evolved at a low pace because of a lack of molecular tools and sufficient investment. Whilst thousands and hundreds of quantitative trait loci (QTL) have been identified in cattle and sheep, respectively, about nine genome scans have been performed in goats dealing with traits as conformation, growth, fiber quality, resistance to nematodes, and milk yield and composition. In contrast, a great effort has been devoted to the characterization of candidate genes and their association with milk, meat, and reproduction phenotypes. In this regard, causal mutations have been identified in the αS1-casein gene that has a strong effect on milk composition and the PIS locus that is linked to intersexuality and polledness. In recent times, the development of massive parallel sequencing technologies has allowed to build a reference genome for goats as well as to monitor the expression of mRNAs and microRNAs in a broad array of tissues and experimental conditions. Besides, the recent design of a 52K SNP chip is expected to have a broad impact in the analysis of the genetic architecture of traits of economic interest as well as in the study of the population structure of goats at a worldwide scale.

Identification of selection signatures in livestock species

The identification of regions that have undergone selection is one of the principal goals of theoretical and applied evolutionary genetics. Such studies can also provide information about the evolutionary processes involved in shaping genomes, as well as physical and functional information about genes/genomic regions. Domestication followed by breed formation and selection schemes has allowed the formation of very diverse livestock breeds adapted to a wide variety of environments and with special characteristics. The advances in genomics in the last five years have enabled the development of several methods to detect selection signatures and have resulted in the publication of a considerable number of studies involving livestock species. The aims of this review are to describe the principal effects of natural/artificial selection on livestock genomes, to present the main methods used to detect selection signatures and to discuss some recent results in this area. This review should be useful also to research scientists working with wild animals/non-domesticated species and plant biologists working with breeding and evolutionary biology.