Unknown,Transcriptomics,Genomics,Proteomics

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Muscle gene expression patterns in pigs with divergent phenotypes for fatness traits

ABSTRACT: Background: Marketing products with added-value characteristics is a current trend in livestock production systems. Regarding meat, selection for intramuscular fat and muscular fatty acid composition is a way to improve the palatability and juiciness of meat while assuring a healthy fat content. This represents selecting animal with a different muscular metabolic profile with respect to the extended selection of lean animals. Results: The present study has analysed the muscular gene expression profiles of 68 commercial Duroc pigs belonging to two groups with extreme phenotypes for traits strongly related with lipid deposition and composition. This has allowed us to compare the physiological and metabolic implications of selecting for each of these extreme groups. Rather than upregulation of a single pathway, the main differences lied on the transcriptional levels of genes related with lipogenesis and lipolysis, revealing the existence of a cycle where triacylglycerols are continuously synthesized and degraded. Most strikingly, several genes which enhanced fatty acid Î²-oxidation and favoured insulin signalling and glucose uptake were upregulated in the fattest animals, indicating that the events leading to peripheral insulin resistance in humans with increased levels of intramuscular fat and obesity do not take place in these pigs. Moreover, neither was detected the well-characterised low-grade inflammatory state observed in overweighed humans. Conclusion: As a whole, our data suggest that selection for increasing intramuscular fat content in pigs would lead to a shift but not a disruption of the metabolic homeostasis of muscle cells. Future studies on the post-translational changes affecting protein activity or expression as well as information about protein location within the cell would be needed to fully understand how lipid deposition affects muscle physiology in pigs. 68 gluteus medius samples form 68 animals belonging to two groups of 34 animals each: HIGH group had higher carcass, plasma and muscle fat content; LOW group had lower carcass, plasma and muscle fat content

ORGANISM(S): Sus scrofa

SUBMITTER: R Pena

PROVIDER: E-GEOD-19275 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:In the last 20 years, there has been significant research towards defining the genetic basis of lipid metabolism and meat quality related traits in pigs. Nowadays, the study of the transcriptome and its regulatory mechanisms allows going far beyond in the genetic dissection of these complex traits. In present study, a genome-wide eQTL scan aiming to detect pig genome regions regulating levels of skeletal muscle mRNA expression has been performed. This study has been conducted on a commercial Duroc population where a number of QTL for muscle fat deposition and fatty acid composition had been detected. GeneChip Porcine Genome® arrays (Affymetrix) were used to determine the gene expression levels of gluteus medius samples from 105 Duroc pigs belonging to two groups with divergent phenotypes for fatness traits. This experimental design aimed to favour detection of eQTL affecting genes related to lipid metabolism and meat quality traits. The whole genome scan with a panel of 110 microsatellites allowed us detecting 613 genome-wide significant eQTL unequally distributed across the pig genome, SSC5 and SSC3 harbouring the highest number of eQTL. Moreover, 11 genome regions with eQTL affecting the expression levels of a high number of genes (eQTL hot spots) have been described. After mapping target probes and discarding low quality probes, a total of 59 cis- and 396 trans-acting eQTL were retained for further analyses. The functional classification showed that lipid-related GO terms were not the most enriched by the list of eQTL-regulated genes. However, a number of regulated genes functionally related to lipid metabolism and fat deposition traits were identified, and their functional relationship with these phenotypes were further investigated. With this purpose, eQTL results were integrated with 1) QTL linkage maps and 2) correlation data between phenotypes and gene expression levels. As a result, a comprehensive list of 29 positional and functional candidate genes was elaborated. These results represent a valuable contribution to the comprehension of genetic regulation of skeletal muscle individual gene expression in swine species, and a first step towards disentangling gene networks and molecular mechanisms involved in lipid metabolism and meat quality traits. 105 gluteus medius samples from 105 animals belonging to two groups of 53 and 52 animals each: HIGH group had higher carcass, plasma and muscle fat content; LOW group had lower carcass, plasma and muscle fat content

Project description:We studied the influence of genetic type (pure Iberian pigs vs crossbred with Duroc) on l.dorsi transcriptome Background: The two main genetic types in Iberian pig production show important phenotypic differences in growth, fattening and tissue composition since early developmental stages. The objective of this work was the evaluation of muscle transcriptome profile in young animals of both genetic types, in order to identify genes, pathways and transcription factors responsible of their phenotypic differences. Contemporary families coming from pure Iberian pigs (IB) or from crossing with Duroc boars (DUxIB) were generated. Piglets (14 from each genetic type) were sacrificed at weaning (28 days) and longissimus dorsi muscle was sampled for composition and gene expression studies. RNA was obtained and hybridized to Affymetrix Porcine Genechip expression arrays. Results: Loin muscle composition showed significant differences between genetic types in intramuscular fat content (6% vs. 4.2% in IB and DUxIB animals, respectively, P=0.009) and in saturated and monounsaturated fatty acid contents (P=0.019 and P=0.044, respectively). Statistical analysis of gene expression data allowed the identification of 256 differentially expressed (DE) genes between genetic types (FDR<0.10), 102 upregulated in IB and 154 upregulated in DUxIB. The size of the effects ranged between 1.2x and 7.8x. Transcript differences were validated for a subset of DE genes by qPCR. Some candidate genes with known effects on muscle growth were found among the DE genes upregulated in DUxIB (IGF2, collagens, integrins). Genes related to lipid metabolism and proteolysis were found among the genes upregulated in IB (ME1, ELOVL6, caspases, catepsins, ubiquitination proteins). We observed alteration in biological functions related to extracellular matrix organization, cellular adhesion, muscle growth and lipid metabolism. Transcription factors (TF) potentially involved in the expression differences found were identified by calculating the regulatory impact factors (RIF). Sixteen TF were found, some of them with known relationship with muscle development (MSTN, SIX4), adipogenesis (CEBPD, PPARGC1B), or extracellular matrix processes (MAX, MXI1). Correlation among the expression of these TF and DE genes show relevant differences between genetic types. Conclusion: The results contribute valuable information about molecular mechanisms determining the phenotypic differences of growth and meat quality between the genetic types studied, mainly related to the development and function of the extracellular matrix and also to some metabolic processes as proteolysis and lipid metabolism. 28 male piglets were employed. 14 animals coming for pure Iberian parents and 14 coming from the crossing of Duroc boars with Iberian sows. Animals were sacrificed at 28 d of age. At the sacrifice, longissimus dorsi muscle tissue was sampled from each animal.

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Muscle gene expression patterns in pigs with divergent phenotypes for fatness traits

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