Proteins in longissimus muscle of Korean native cattle and their relationship to meat quality

Reverse phase protein arrays for the identification/validation of biomarkers of beef texture and their use for early classification of carcasses

The validation of biomarkers and tools for the prediction of beef texture remains a challenging task. In this study, reverse phase protein arrays (RPPA) quantified 29 protein biomarkers in the m. Longissimus thoracis of Charolais cattle sampled early post-mortem. Myosin heavy chain 1 (MHC1, slow-oxidative fibers) and Retinal dehydrogenase 1 (ALDH1A1, oxidative enzyme) discriminated between tender and juicy vs. tough meat with residues classes and are validated as prime biomarkers of beef texture. Several proteins belonging to energy metabolism, heat shock and oxidative stress, cytoskeletal, cell signaling and apoptosis were related with tenderness. Among the unusual proteins, Four and a half LIM domains 1 (FHL1) and Tripartite motif protein 72 (TRIM72) correlated respectively negatively and positively with beef tenderness. Principal component regression was used for the first time to explain beef texture traits using biomarkers. The results are very promising as they revealed sophisticated mechanisms behind the tenderizing process.

Identification of Biomarkers Associated with the Rearing Practices, Carcass Characteristics, and Beef Quality: An Integrative Approach

Data from birth to slaughter of cull cows allowed using a PCA-based approach coupled with the iterative K-means algorithm the identification of three rearing practices classes. The classes were different in their carcass characteristics. Old cows raised mainly on pasture have better carcass characteristics, while having an equivalent tenderness, juiciness, flavor, intramuscular fat content, and pHu to those fattened with hay or haylage. The Longissimus thoracis muscle of the cows raised on pasture (with high physical activity) showed greater proportions of IIA fibers at the expense of the fast IIX ones. Accordingly, the meat of these animals have better color characteristics. Superoxide dismutase (SOD1) and αB-crystallin quantified by Dot-Blot were the only other biomarkers to be more abundant in "Grass" class compared to "Hay" and "Haylage" classes. The relationships between the biomarkers and the 6 carcass and 11 meat quality traits were investigated using multiple regression analyses per rearing practices. The associations were rearing practice class and phenotype trait-dependent. ICDH and TP53 were common for the three classes, but the direction of their entrance was different. In addition, rearing practices and carcass traits were not related with Hsp70-Grp75 and μ-calpain abundances. The other relationships were specific for two or one rearing practices class. The rearing practices dependency of the relationships was also found with meat quality traits. Certain proteins were for the first time related with some beef quality traits. MyHC-IIx, PGM1, Hsp40, ICDH, and Hsp70-Grp75 were common for the three rearing practices classes and retained to explain at list one beef quality trait. A positive relationship was found between PGM1 and hue angle irrespective of rearing practices class. This study confirms once again that production-related traits in livestock are the result of sophisticated biological processes finely orchestrated during the life of the animal and soon after slaughter.

Identification of novel regulatory GRE-binding elements in the porcine IP3R1 gene promoter and their transcriptional activation under glucocorticoid stimulation

Inositol 1,4,5-trisphosphate receptor 1 (IP3R1) is a type of ligand-gated calcium channel that is expressed predominantly in mammalian skeletal muscle, where it acts as a key regulator of calcium homeostasis. In meat, calcium disequilibrium is accompanied by the deterioration of meat quality. Here we show that serum cortisol concentration was higher and the IP3R1 gene expression level increased markedly in pigs exposed to high stress. In porcine primary muscle cells, dexamethasone (DEX, a synthetic glucocorticoid) increased the protein levels of porcine IP3R1 and GRα, and cell apoptosis, and the specific GRα inhibitor RU486 attenuated these effects. DEX also increased the expression of IP3R1 at both the gene and protein levels, and this expression was attenuated by RU486, siRNA against GRα, and the transcriptional inhibitor actinomycin D. DEX significantly reduced cell viability and increased the intracellular calcium concentration, and these effects were attenuated by siRNA against GRα. Bioinformatics analyses predicted a potential glucocorticoid response element (GRE) located in the region -326 to -309 upstream of the IP3R1 promoter and highly conserved in pigs and other mammalian species. Promoter analysis showed that this region containing the GRE was critical for transcriptional activity of porcine IP3R1 under DEX stimulation. This was confirmed by deletion and site-mutation methods. EMSA and ChIP assays showed that this potential GRE bound specifically to GRα and this complex activated the transcription of the IP3R1 gene. Taken together, these data suggest that DEX-mediated induction of IP3R1 influences porcine muscle cells through the transcriptional activation of a mechanism involving interactions between GRα and a GRE present in the proximal IP3R1 promoter. This process can lead to an imbalance in intracellular calcium concentration, which may subsequently activate the apoptosis signal and decrease cell activity, and cause deterioration of meat quality.

Associations among Protein Biomarkers and pH and Color Traits in Longissimus thoracis and Rectus abdominis Muscles in Protected Designation of Origin Maine-Anjou Cull Cows

This study investigated the relationships among a list of 23 protein biomarkers with CIE-L*a*b* meat color traits and ultimate pH on Longissimus thoracis (LT) and Rectus abdominis (RA) muscles of 48 protected designation of origin Maine-Anjou cows. The technological parameters were correlated with several biomarkers and were in some cases muscle-dependent. More biomarkers were related to pHu in LT than in RA muscle. Some consistencies were found, by the common correlation of pHu with MyHC-IIa and MyHC-IIx. The pHu of the LT muscle was also correlated with other cytoskeletal entities and proteins belonging to metabolism and cellular stress. In contrast to the relationships found between biomarkers and LT pHu, more proteins were related to the instrumental color coordinates in RA than in LT muscle. The regression equations were parameter- and muscle-dependent. Certain of the retained proteins explained more than one color coordinate. Hsp70-Grp75 was positive in the models of L*, a*, b*, and C* of LT and of b* in the RA muscle. Further heat shock proteins were strongly related with the meat color coordinates in both muscles. The involvement of metabolic enzymes and myofibrillar proteins in the meat color development was also verified in this experiment. This study confirmed once again the importance of numerous biological pathways in beef color.

Analysis of Longissimus thoracis Protein Expression Associated with Variation in Carcass Quality Grade and Marbling of Beef Cattle Raised in the Pacific Northwestern United States

Longissimus thoracis (LD) samples from 500 cattle were screened for protein expression differences relative to carcass quality grade. The LD of the top 5% (low prime and high choice, HQ) and bottom 5% (low select, LQ) carcasses were analyzed using two-dimensional difference gel electrophoresis and Western blot. Following initial screening, 11 candidate proteins were selected for Western blot analyses. Differentially expressed proteins were clustered into four groups: (1) heat shock proteins and oxidative protection, (2) sarcomeric proteins (muscle maturity and fiber type), (3) metabolism and energetics, and (4) miscellaneous proteins. Proteins from groups 1 and 2 were greater in HQ carcasses. Alternatively, increased quantities of proteins from group 3 were observed in LQ carcasses. Proteomic differences provide insights into pathways contributing to carcass quality grade. A deeper understanding of the physiological pathways involved in carcass quality grade development may allow producers to employ production practices that improve quality grade.

Differences in Beef Quality between Angus (Bos taurus taurus) and Nellore (Bos taurus indicus) Cattle through a Proteomic and Phosphoproteomic Approach

Proteins are the major constituents of muscle and are key molecules regulating the metabolic changes during conversion of muscle to meat. Brazil is one of the largest exporters of beef and most Brazilian cattle are composed by zebu (Nellore) genotype. Bos indicus beef is generally leaner and tougher than Bos taurus such as Angus. The aim of this study was to compare the muscle proteomic and phosphoproteomic profile of Angus and Nellore. Seven animals of each breed previously subjected the same growth management were confined for 84 days. Proteins were extracted from Longissimus lumborum samples collected immediately after slaughter and separated by two-dimensional electrophoresis. Pro-Q Diamond stain was used in phosphoproteomics. Proteins identification was performed using matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Tropomyosin alpha-1 chain, troponin-T, myosin light chain-1 fragment, cytoplasmic malate dehydrogenase, alpha-enolase and 78 kDa glucose-regulated protein were more abundant in Nellore, while myosin light chain 3, prohibitin, mitochondrial stress-70 protein and heat shock 70 kDa protein 6 were more abundant in Angus (P<0.05). Nellore had higher phosphorylation of myosin regulatory light chain-2, alpha actin-1, triosephosphate isomerase and 14-3-3 protein epsilon. However, Angus had greater phosphorylation of phosphoglucomutase-1 and troponin-T (P<0.05). Therefore, proteins involved in contraction and muscle organization, myofilaments expressed in fast or slow-twitch fibers and heat shock proteins localized in mitochondria or sarcoplasmic reticulum and involved in cell flux of calcium and apoptosis might be associated with differences in beef quality between Angus and Nellore. Furthermore, prohibitin appears to be a potential biomarker of intramuscular fat in cattle. Additionally, differences in phosphorylation of myofilaments and glycolytic enzymes could be involved with differences in muscle contraction force, susceptibility to calpain, apoptosis and postmortem glycolysis, which might also be related to differences in beef quality among Angus and Nellore.

Bos indicus cattle possess greater basal concentrations of HSP27, alpha B-crystallin, and HSP70 in skeletal muscle in vivo compared with cattle

The objectives of the present study were to evaluate the basal concentrations of heat shock proteins (HSP) between and cattle and to determine if HSP basal concentrations change as an animal matures. A total of 40 cattle were used in a 2 × 2 factorial design to evaluate the effects of genotype and age (heifers and mature cows) on basal concentrations of heat shock protein 27 (HSP27), α B-crystallin (Cryab), and heat shock protein 70 (HSP70). Each experimental group of 10 animals was sampled on a separate day over a period of 4 wk during July 2014. A muscle sample was collected from the longissimus thoracis (LT) and concentrations of HSP were quantified using ELISA. There were no significant differences in HSP concentration for the interaction between age and genotype or for age alone. cattle had greater ( < 0.05) basal concentrations of HSP27, Cryab, and HSP70 in the LT than cattle. The results of this study show that basal in vivo HSP concentrations differ between and cattle. However, further studies are needed to investigate the relationship between HSP concentrations and meat tenderness with respect to genotypes to see if HSP concentrations account for at least some variability in tenderness differences.

Proteomic analysis of goat Longissimus dorsi muscles with different drip loss values related to meat quality traits

Longissimus dorsi muscles from 3 goat species were assigned to high and low drip loss groups. Physio-chemical properties, sarcomere length, and proteome profiles were investigated. The high drip loss group had lower pH, higher brightness, and higher shear force values, and shorter sarcomere lengths than the low drip loss group. 22 differential proteins were identified between high and low loss groups. α-Enolase, NADH dehydrogenase, pyruvate dehydrogenase E1, HSP27, superoxide dismutase, peroxiredoxin-2, myosin, and the myosin light chain were among these proteins, which were metabolic enzymes, stress response factors, and structural proteins that affected glycolysis, oxidation, and muscle contraction. Drip loss was probably produced via proteins involved in glycolysis, oxidation, and muscle contraction.

Beef quality with different intramuscular fat content and proteomic analysis using isobaric tag for relative and absolute quantitation of differentially expressed proteins

Intramuscular fat (IMF) is an important trait for beef eating quality. The mechanism of how IMF is deposited in beef cattle muscle is not clear at the molecular level. The muscle (M. longissimus lumborum: LL) of a group of Xiangxi yellow×Angus cattle with high fat levels (HF), was compared to the muscle of a low fat group (LF). The meat quality and the expressed protein patterns were compared. It was shown that LL from the HF animals had a greater fat content (P<0.05) and lower moisture content (P<0.05) than LL from LF animals. Forty seven sarcoplasmic proteins were differentially expressed and identified between the two groups. These proteins are involved in 6 molecular functions and 16 biological processes, and affect the Mitogen-activated protein kinases pathway, insulin pathway and c-Jun N-terminal kinases leading to greater IMF deposition. Cattle in the HF group had greater oxidative capacity and lower glycolytic levels suggesting a greater energetic efficiency.

Expression Marker-Based Strategy to Improve Beef Quality

For beef cattle research, a main objective is to control concomitantly the development of muscles and the qualities of beef cuts. Beef quality is a complex phenotype that is only detectable after slaughter and is highly variable. The beef industry is in need of tools to estimate beef quality of live cattle or online in abattoirs, with specific attention towards sensory attributes (tenderness, juiciness, flavour, and colour). Identification of relevant genetic and genomic markers is ongoing, especially for tenderness—a top priority quality attribute. In this paper, we describe the steps of an expression marker-based strategy to improve beef sensory quality, from the discovery of biomarkers that identify consistent beef and the biological functions governing beef tenderness to the integration of the knowledge into detection tests for desirable animals. These tools should soon be available for the management of sensory quality in the beef production chain for meeting market's demands and assuring good quality standards.

The Effect of Weight Loss on the Muscle Proteome in the Damara, Dorper and Australian Merino Ovine Breeds

Seasonal Weight Loss (SWL) is an important constraint, limiting animal production in the Tropics and the Mediterranean. As a result, the study of physiological and biochemical mechanisms by which domestic animal breeds respond to SWL is important to those interested in animal breeding and the improvement thereof. To that end, the study of the proteome has been instrumental in gathering important information on physiological mechanisms, including those underlying SWL. In spite of that, little information is available concerning physiological mechanisms of SWL in production animals. The objective of this study was to determine differential protein expression in the muscle of three different breeds of sheep, the Australian Merino, the Dorper and the Damara, each showing different levels of tolerance to weight loss (low, medium and high, respectively). Per breed, two experimental groups were established, one labeled “Growth” and the other labeled “Restricted.” After forty-two days of dietary treatment, all animals were euthanized. Muscle samples were then taken. Total protein was extracted from the muscle, then quantified and two-dimensional gel electrophoresis were conducted using 24 cm pH 3–10 immobiline dry strips and colloidal coomassie staining. Gels were analyzed using Samespots^® software and spots of interest were in-gel digested with trypsin. The isolated proteins were identified using MALDI-TOF/TOF. Results indicated relevant differences between breeds; several proteins are suggested as putative biomarkers of tolerance to weight loss: Desmin, Troponin T, Phosphoglucomutase and the Histidine Triad nucleotide-binding protein 1. This information is of relevance to and of possible use in selection programs aiming towards ruminant animal production in regions prone to droughts and weight loss.

Effect of Dietary Processed Sulfur Supplementation on Texture Quality, Color and Mineral Status of Dry-cured Ham

This study was performed to investigate the chemical composition, mineral status, oxidative stability, and texture attributes of dry-cured ham from pigs fed processed sulfur (S, 1 g/kg feed), and from those fed a basal diet (CON), during the period from weaning to slaughter (174 d). Total collagen content and soluble collagen of the S group was significantly higher than that of the control group (p<0.05). The pH of the S group was significantly higher than that of the control group, whereas the S group had a lower expressible drip compared to the control group. The S group also showed the lower lightness compared to the control group (p<0.05). In regard to the mineral status, the S group had significantly lower Fe(2+) and Ca(2+) content than the control group (p<0.05), whereas the proteolysis index of the S group was significantly increased compared to the control group (p<0.05). The feeding of processed sulfur to pigs led to increased oxidative stability, related to lipids and pigments, in the dry-cured ham (p<0.05). Compared to the dry-cured ham from the control group, that from the S group exhibited lower springiness and gumminess; these results suggest that feeding processed sulfur to pigs can improve the quality of the texture and enhance the oxidative stability of dry-cured ham.

Understanding tenderness variability and ageing changes in buffalo meat: biochemical, ultrastructural and proteome characterization

Understanding of biological impact of proteome profile on meat quality is vital for developing different approaches to improve meat quality. Present study was conducted to unravel the differences in biochemical, ultrastructural and proteome profile of longissimus dorsi muscle between buffaloes (Bubalus bubalis) of different age groups (young v. old). Higher (P<0.05) myofibrillar and total protein extractability, muscle fibre diameter, and Warner-Bratzler shear force (WBSF) values was observed in old buffalo meat relative to meat from young buffaloes. Scanning electron microscopy photographs revealed reduced fibre size with increased inter-myofibrillar space in young compared with old buffalo meat. Transmission electron microscopy results revealed longer sarcomeres in young buffalo meat relative to meat from old buffaloes. Proteomic characterization using two-dimensional gel electrophoresis (2DE) found 93 differentially expressed proteins between old and young buffalo meat. Proteome analysis using 2DE revealed 191 and 95 differentially expressed protein spots after 6 days of ageing in young and old buffalo meat, respectively. The matrix assisted laser desorption ionization time-of flight/time-of flight mass spectrometry (MALDI-TOF/TOF MS) analysis of selected gel spots helped in identifying molecular markers of tenderness mainly consisting of structural proteins. Protein biomarkers identified in the present study have the potential to differentiate meat from young and old buffaloes and pave the way for optimizing strategies for improved buffalo meat quality.

Proteome Changes in biceps femoris Muscle of Iranian One-Humped Camel and Their Effect on Meat Quality Traits

In this study physicochemical and quality traits of biceps femoris and longissimus thoracis muscles of male and female Iranian one-humped camel were determined during 14 days of refrigeration storage. Analysis of variance of the results showed that only shear force and temperature were affected by the gender (p<0.05). Anatomical location of the muscle influenced the meat properties except for drip loss (p<0.05). Also, except for cooking loss, ageing influenced the physicochemical and quality properties of meat; during 14 days of storage, proteolysis resulted in an increase of L* and b* values, drip loss and myofibrillar fragmentation index, and the decrease of a* value, expressed juice, shear force and sarcomere length. Proteome changes (myofibrillar proteins) during storage were investigated. Gel analysis revealed that 19 protein spots were significantly changed during 24, 72 and 168 h post-mortem. Fifteen spots were identified by MALDI-TOF/TOF mass spectrometer. Correlation analysis revealed significant correlations of actin, troponin T, capping protein, heat shock proteins (HSP) and desmin with physicochemical and quality properties of meat (p<0.05). Actin might be a potential protein marker for colour, tenderness and water-holding capacity, and HSP27 and desmin are good candidate markers for colour and tenderness, respectively.

The effect of electrical stimulation on post mortem myofibrillar protein degradation and small heat shock protein kinetics in bull beef

This study aimed to determine the effect of electrical stimulation and ultimate pH (pHu) on shear force, myofibrillar protein degradation and small heat shock protein (sHSP) concentrations in M. longissimus lumborum (LL). The LL from both sides of carcasses (n=15) was excised with low voltage electrical stimulation (ES) applied to an LL muscle from one side, while the opposing LL muscle was not stimulated (NS). Muscles were categorised into low (pHu<5.8), intermediate (5.8≤pHu<6.2) and high pHu (pHu≥6.2) and aged for up to 28days post mortem at -1.5°C. High pHu meat tenderised faster which corresponded with the faster degradation of titin and desmin in this group compared with low and intermediate pHu meat. Electrical stimulation significantly affected the variable levels of αβ-crystallin and HSP20 with higher concentrations of these sHSP in ES muscles at later ageing timepoints compared with NS muscles.

Effect of Quality Grade and Storage Time on the Palatability, Physicochemical and Microbial Quality of Hanwoo Striploin Beef

The effects of quality grade and storage time on physicochemical, sensory properties and microbial population of Hanwoo striploin beef were investigated. After a total of 30 Hanwoo beef were slaughtered, the cold carcasses were graded by official meat grader at 24 h postmortem. The carcasses were categorized into five groups (quality grade 1++, 1+, 1, 2, and 3) and were vacuum-packaged and stored. The samples were kept for 1, 4, 6, 8, 11, 13, 15, 18, 20, 22 and 25 d for analyses. As the quality grade was increased, moisture, protein and ash contents decreased (p<0.05). Higher quality grade corresponded with higher fat contents. The shear force values decreased with increasing quality grade and showed decreases sharply during the first 4 d (p<0.05). pH, water holding capacity, cooking loss, and volatile basic nitrogen for grade 1++ groups were lower than for grade 3 (p<0.05). CIE L* and b* values increased as increased quality grade (p<0.05). Meat color decreased until 13 d and fluctuated after 15 d of storage (p<0.05). Regarding the sensory scores, higher quality grade corresponded with higher juiciness, tenderness, flavor, fatty and palatability scores (p<0.05). Generally, increased storage time for 15 d improved sensory scores attributes. Results indicate that a high quality grade could positively influence physicochemical and sensory properties.

Biomarkers: Non-destructive Method for Predicting Meat Tenderization

Meat tenderness is the primary and most important quality attribute for the consumers worldwide. Tenderness is the process of breakdown of collagen tissue in meat to make it palatable. The earlier methods of tenderness evaluation like taste panels and shear force methods are destructive, time consuming and ill suited as they requires removing a piece of steak from the carcass for performing the test. Therefore, a non-destructive method for predicting the tenderness would be more desirable. The development of a meat quality grading and guarantee system through muscle profiling research can help to meet this demand. Biomarkers have the ability to identify if an exposure has occurred. Biomarkers of the meat quality are of prime importance for meat industry, which has ability to satisfy consumers' expectations. The biomarkers so far identified have been then sorted and grouped according to their common biological functions. All of them refer to a series of biological pathways including glycolytic and oxidative energy production, cell detoxification, protease inhibition and production of Heat Shock Proteins. On this basis, a detailed analysis of these metabolic pathways helps in identifying tenderization of meat having some domains of interest. It was, therefore, stressed forward that biomarkers can be used to determine meat tenderness. This review article summarizes the uses of several biomarkers for predicting the meat tenderness.

Adaptive traits of indigenous cattle breeds: The Mediterranean Baladi as a case study

Generally taken, breeds of Bos taurus ancestry are considered more productive, in comparison with Bos indicus derived breeds that present enhanced hardiness and disease resistance, low nutritional requirements and higher capability of feed utilization. While breeds of B. taurus have been mostly selected for intensive production systems, indigenous cattle, developed mostly from indicine and African taurines, flourish in extensive habitats. Worldwide demographic and economic processes face animal production with new challenges - the increasing demand for animal food products. Intensification of animal husbandry is thus a desired goal in stricken parts of the world. An introduction of productive traits to indigenous breeds might serve to generate improved biological and economic efficiencies. For this to succeed, the genetic merit of traits like efficiency of feed utilization and product quality should be revealed, encouraging the conservation initiatives of indigenous cattle populations, many of which are already extinct and endangered. Moreover, to overcome potential genetic homogeneity, controlled breeding practices should be undertaken. The Baladi cattle are a native local breed found throughout the Mediterranean basin. Purebred Baladi animals are rapidly vanishing, as more European breeds are being introduced or used for backcrosses leading to improved production. The superiority of Baladi over large-framed cattle, in feedlot and on Mediterranean pasture, with respect to adaptability and efficiency, is highlighted in the current review.

Application to proteomics to understand and modify meat quality

The use of proteomics in the field of meat science has gained in robustness and accuracy. This is consistent with the genomic and bioinformatic tools. Its application to sensorial and technological meat quality traits is discussed as well as the emergence of sanitary and nutritional issue which will grow in a next future.

Heat shock and structural proteins associated with meat tenderness in Nellore beef cattle, a Bos indicus breed

Nellore beef cattle, a Bos indicus (Zebu) breed, is well adapted to tropical conditions and has allowed Brazil to become one of the largest producers of red meat. Nevertheless, B. indicus breeds are reported to have less tender meat than Bos taurus. This study was designed to identify genes associated with meat tenderness and thus provides important information for breeding programs. A group of 138 animals was evaluated for longissimus thoracis muscle shear force (SF). Animals with the highest and lowest SF values (six animals each) were then selected for protein abundance studies. Samples were subjected to two-dimensional gel electrophoresis (2-DE) followed by peptide sequencing through mass spectrometry (MS) to identify differentially expressed proteins associated with SF values. Seventeen differentially expressed spots were observed (p<0.05) between the two groups. The 13 proteins identified included structural proteins (alpha actin-1, MLC1, MLC3, MLC2F and tropomyosin), related to cell organization (HSPB1 and HSP70), metabolism (beta-LG, ACBD6 and Complex III subunit I) and some uncharacterized proteins. Results confirm the existence of differentially expressed proteins associated with SF, which can lead to a better understanding of mechanisms involved in meat tenderness.

A network-based approach for predicting Hsp27 knock-out targets in mouse skeletal muscles

Thanks to genomics, we have previously identified markers of beef tenderness, and computed a bioinformatic analysis that enabled us to build an interactome in which we found Hsp27 at a crucial node. Here, we have used a network-based approach for understanding the contribution of Hsp27 to tenderness through the prediction of its interactors related to tenderness. We have revealed the direct interactors of Hsp27. The predicted partners of Hsp27 included proteins involved in different functions, e.g. members of Hsp families (Hsp20, Cryab, Hsp70a1a, and Hsp90aa1), regulators of apoptosis (Fas, Chuk, and caspase-3), translation factors (Eif4E, and Eif4G1), cytoskeletal proteins (Desmin) and antioxidants (Sod1). The abundances of 15 proteins were quantified by Western blotting in two muscles of HspB1-null mice and their controls. We observed changes in the amount of most of the Hsp27 predicted targets in mice devoid of Hsp27 mainly in the most oxidative muscle. Our study demonstrates the functional links between Hsp27 and its predicted targets. It suggests that Hsp status, apoptotic processes and protection against oxidative stress are crucial for post-mortem muscle metabolism, subsequent proteolysis, and therefore for beef tenderness.

The GENOTEND chip: a new tool to analyse gene expression in muscles of beef cattle for beef quality prediction

Background

Previous research programmes have described muscle biochemical traits and gene expression levels associated with beef tenderness. One of our results concerning the DNAJA1 gene (an Hsp40) was patented. This study aims to confirm the relationships previously identified between two gene families (heat shock proteins and energy metabolism) and beef quality.

Results

We developed an Agilent chip with specific probes for bovine muscular genes. More than 3000 genes involved in muscle biology or meat quality were selected from genetic, proteomic or transcriptomic studies, or from scientific publications. As far as possible, several probes were used for each gene (e.g. 17 probes for DNAJA1). RNA from Longissimus thoracis muscle samples was hybridised on the chips. Muscles samples were from four groups of Charolais cattle: two groups of young bulls and two groups of steers slaughtered in two different years. Principal component analysis, simple correlation of gene expression levels with tenderness scores, and then multiple regression analysis provided the means to detect the genes within two families (heat shock proteins and energy metabolism) which were the most associated with beef tenderness. For the 25 Charolais young bulls slaughtered in year 1, expression levels of DNAJA1 and other genes of the HSP family were related to the initial or overall beef tenderness. Similarly, expression levels of genes involved in fat or energy metabolism were related with the initial or overall beef tenderness but in the year 1 and year 2 groups of young bulls only. Generally, the genes individually correlated with tenderness are not consistent across genders and years indicating the strong influence of rearing conditions on muscle characteristics related to beef quality. However, a group of HSP genes, which explained about 40% of the variability in tenderness in the group of 25 young bulls slaughtered in year 1 (considered as the reference group), was validated in the groups of 30 Charolais young bulls slaughtered in year 2, and in the 21 Charolais steers slaughtered in year 1, but not in the group of 19 steers slaughtered in year 2 which differ from the reference group by two factors (gender and year). When the first three groups of animals were analysed together, this subset of genes explained a 4-fold higher proportion of the variability in tenderness than muscle biochemical traits.

Conclusion

This study underlined the relevance of the GENOTEND chip to identify markers of beef quality, mainly by confirming previous results and by detecting other genes of the heat shock family as potential markers of beef quality. However, it was not always possible to extrapolate the relevance of these markers to all animal groups which differ by several factors (such as gender or environmental conditions of production) from the initial population of reference in which these markers were identified.

Proteomic analysis and differential expression in protein extracted from chicken with a varying growth rate and water-holding capacity

Chickens from a randomly bred genetic line were segregated into high and low growth rates and high and low water-holding capacities (WHCs). The objective of this study was to identify protein markers associated with slow and fast growth rates and low and high WHCs from water-soluble protein (WSP) and crude myofibrillar protein (CMP) extracts of chicken breast muscle. Proteins were fractionated using two-dimensional electrophoresis, and a total of 22 protein spots were selected, excised, and analyzed by in-gel tryptic digestion and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Proteins expressed in extracts from slow and fast growth rates and low and high WHCs included metabolic enzymes, such as creatine kinase, pyruvate kinase, triosephosphate isomerase, and ubiqitin; housekeeping proteins, such as heat shock protein; contractile proteins, such as myosin heavy chain; actin; and also MHC isoforms and actin isoforms. The mass spectra of 20 protein spots significantly matched (protein score >83; P < 0.05) an online database. In CMP, there were unique proteins that were present only in the fast-growth population: gi|118099530 , gi|20664362 , gi|71895043 , gi|114794125 , gi|297343122 , and gi|71895043 . This information identified protein markers associated with growth rate and water holding capacity. Some of those protein markers could be added to the chicken database.

Heat shock protein B1 and its regulator genes are negatively correlated with intramuscular fat content in the longissimus thoracis muscle of Hanwoo (Korean cattle) steers

In previous proteomic studies, heat shock protein β 1 (HSPB1) was detected as a candidate protein related to meat quality in cattle. This study sought to determine if its gene expression was associated with intramuscular fat content in the longissimus thoracis muscle of Korean cattle (Hanwoo). Tissue from two groups of 10 steers each, low-marbling (mean intramuscular fat content, 7.4 ± 1.5%) and high-marbling (23.5 ± 2.8%), were used for immunoblotting, real-time PCR, and statistical analyses. HSPB1 expression in both mRNA and protein was shown to be negatively related to intramuscular fat content (P < 0.05). Pathway analysis found two genes, TNF receptor superfamily member 6 (FAS) and angiotensinogen (AGT), that were regulators of the HSPB1 gene. The expression of the two genes showed a negative correlation with intramuscular fat content (P < 0.05). These results suggest that HSPB1, FAS, and AGT may be good candidate genes associated with intramuscular fat content in the longissimus muscle of Korean cattle.