Unknown,Transcriptomics,Genomics,Proteomics

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Porcine intramuscular fat content and composition are regulated by quantitative trait loci with muscle-specific effects

ABSTRACT: Intramuscular fat (IMF) storage is a biological process with strong impact on nutritional and technological properties of meat, and also with relevant consequences on human health. The genetic architecture of IMF content and composition phenotypes has been thoroughly studied in pigs through the identification of quantitative trait loci (QTL) and the estimation of genetic parameters. A question that has not been elucidated yet is if the genetic determinants of IMF-related phenotypes are muscle specific or, conversely, they have broad effects on the whole skeletal muscle compartment. We have addressed this question by generating lipid QTL maps for two muscles with a high commercial value, gluteus medius (GM) and longissimus thoracis et lumborum (LTL), in a Duroc commercial population (N=350). As a complementary approach, we have analysed the mRNA expression pattern of both muscles at a whole genome scale. The lack of concordance between the GM and LTL QTL maps evidenced that the effects of polymorphisms influencing IMF, cholesterol and fatty acids contents are modulated to some extent by complex spatial factors related with muscle location, metabolism and function. This interpretation was supported by our finding that genes influencing cell differentiation, muscle development and function and lipid metabolism are differentially expressed between muscles. These results have important implications on the implementation of genomic selection schemes aimed to improve the lipid profile of swine meat. Moreover, they confirm pigs as a valuable model to dissect the genetic basis of muscle lipid phenotypes of clinical interest in human. Longissimus thoracis et lumborum muscle tissue from 10 high and 9 low fattening Duroc pigs were compared in this study.

ORGANISM(S): Sus scrofa

SUBMITTER: angela canovas

PROVIDER: E-GEOD-25708 | 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:Purpose: Next-generation sequencing (NGS) was used to select genes potentially associated with fiber-type distribution and cell size in porcine muscle tissue. Methods: The histological profile of the longissimus lumborum muscle was establish by method involving detection of NADPH dehydrogenase (diaphorase) and immunohistochemically detection of myosin chains. The muscle transcriptome sequencing was performed for 11 pigs using Illumina HiScan SQ in 50 single-end cycles. The quantifying transcript abundances was made using the RSEM supported by STAR aligner. The raw reads were aligned to the Sus scrofa reference genome (assembly Sscrofa10.2). Differentially expressed genes were detected by edgeR, baySeq and DESeq2. The RNA-seq results were validated using by qPCR. Results: The RNA-seq approach allows to identify 397 differentially expressed genes (DEGs) indicated as significant (FDR<0.05) using three software: DESeq2, edgeR and baySeq. Detected genes and pathways deregulated in muscle depend on tissue microstructure were associated with metabolic processes â?? 158 genes; cellular processes â?? 122; biological regulation â?? 62; localization â?? 51 and 35 genes with developmental processes. The detected DEGs were included in such pathways as: PI3K-Akt; FoxO and MAPK signaling pathways, regulation of actin cytoskeleton, lysine degradation and insulin signaling pathway as well as in mTOR and Hippo signaling. Conclusions: This results highlight the mainly metabolic pathways related with glucose metabolism and contraction processes of muscle cells. The comparison of whole gene expression profiles between muscles characterized by different fiber-type distribution showed that processes of growth and proliferation of different fiber types are determined by diverse molecular mechanism, which conditioned the unique histological structure of muscle tissue. The muscle (longissimus lumborum) transcriptome sequencing was performed for 11 pigs using Illumina HiScan SQ in 50 single-end cycles and in five technical repetitions.

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Porcine intramuscular fat content and composition are regulated by quantitative trait loci with muscle-specific effects

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