Project description:Boar taint is an offensive odour and flavour from developed in a proportion of non-castrated male pigs (boars). Surgical castration is an effective solution but is under debate due to animal welfare concerns. Gene-based selection for low boar taint has been proposed as concentrations of the main compounds responsible for boar taint (androstenone, skatole and indole [ASI]) exhibit heritability but candidate biomarkers are lacking. The aims of this study were to identify expression quantitative trait loci (eQTLs) associated with ASI in order to aid development of candidate biomarkers and to generate insights into biological pathways. Gene expression profiles were obtained by RNA-Seq from testis of Danish Duroc × Landrace/Yorkshire boars fed either a control or chicory-added diet and genotyping was conducted with a high density SNP panel. A tendency (P = 0.052) of lowered ASI concentrations was found in the chicory group. Furthermore, a high correlation was found between estimated breeding values (EBVs) of androstenone and androstenone concentrations (r2 = 0.48). A total of 213 eQTLs, representing 125 unique genes including MVP, COX1, MAP2K4 and RDH16, contained genotypes associated with summed ASI concentrations and of these, six genes were also differentially expressed across ASI/diet groups. The genes were functionally associated with membrane localised proteins, extracellular exosomes, ATP binding, MAPK cascade and oxidative stress. The highest densities of the eQTLs were on pig chromosomes (SSC) SSC18, SSC12, SSC2, SSC7 and SSC14, in that order. A total of 42 known porcine traits were enriched by the genomic coordinates, including health, meat quality and one reproduction trait. A total of 33 candidate eQTLs enriched known genomic coordinates for androstenone and odour intensity in fat. Our findings suggests that careful monitoring of important productions parameters is necessary, if gene-based selection is performed with markers located within the genomic coordinates of the candidate eQTLs or the eQTLs themselves.

Project description:Boar taint is a major obstacle when using uncastrated male pigs for swine production. One of the main compounds causing this taint is androstenone, a pheromone produced in porcine testis. Here we use microarrays to study the expression of thousands of genes simultaneously in testis of high and low androstenone boars. The study allows identification of genes and pathways associated with elevated androstenone levels. Testicular tissue was collected from 60 boars, 30 with extreme high and 30 with extreme low levels of androstenone, from each of the two breeds Duroc and Norwegian Landrace. The samples were hybridised to porcine arrays containing 26.877 cDNA clones, detecting 563 and 160 genes that were differentially expressed (p < 0.01) in Duroc and Norwegian Landrace, respectively. Of these significantly up- and down-regulated clones, 72 were found to be common for the two breeds, suggesting both general and breed specific mechanisms in regulation of, or response to androstenone levels in boars. Ten of the most significant genes were chosen for verification of expression patterns by quantitative real competitive PCR and real-time PCR. As expected, our results point towards steroid hormone metabolism and biosynthesis as important biological processes for the androstenone levels, but other potential pathways were identified as well. Among these were oxidoreductase activity, ferric iron binding, iron ion binding and electron transport activities. Genes belonging to the cytochrome P450 and hydroxysteroid dehydrogenase families were highly up-regulated, in addition to several genes encoding different families of conjugation enzymes. Furthermore, a number of genes encoding transcription factors were found both up- and down-regulated. The high number of clones belonging to ferric iron and iron ion binding suggests an importance of these genes, and the association between these pathways and androstenone levels is not previously described. This study contributes to the understanding of the complex genetic system controlling and responding to androstenone levels in pig testis. The identification of new pathways and genes involved in the biosynthesis and metabolism of androstenone is an important first step towards finding molecular markers to reduce boar taint. Keywords: high vs low Testicle samples from animals with extreme androstenone values, 30 high and 30 low from each of the two breeds Norwegian Landrace and Duroc, were used for the experiment. Each microarray was hybridised with one high and one low androstenone sample from the same breed, giving a total of 30 arrays for each breed.

Project description:Boar taint is a major obstacle when using uncastrated male pigs for swine production. One of the main compounds causing this taint is androstenone, a pheromone produced in porcine testis. Here we use microarrays to study the expression of thousands of genes simultaneously in testis of high and low androstenone boars. The study allows identification of genes and pathways associated with elevated androstenone levels. Testicular tissue was collected from 60 boars, 30 with extreme high and 30 with extreme low levels of androstenone, from each of the two breeds Duroc and Norwegian Landrace. The samples were hybridised to porcine arrays containing 26.877 cDNA clones, detecting 563 and 160 genes that were differentially expressed (p < 0.01) in Duroc and Norwegian Landrace, respectively. Of these significantly up- and down-regulated clones, 72 were found to be common for the two breeds, suggesting both general and breed specific mechanisms in regulation of, or response to androstenone levels in boars. Ten of the most significant genes were chosen for verification of expression patterns by quantitative real competitive PCR and real-time PCR. As expected, our results point towards steroid hormone metabolism and biosynthesis as important biological processes for the androstenone levels, but other potential pathways were identified as well. Among these were oxidoreductase activity, ferric iron binding, iron ion binding and electron transport activities. Genes belonging to the cytochrome P450 and hydroxysteroid dehydrogenase families were highly up-regulated, in addition to several genes encoding different families of conjugation enzymes. Furthermore, a number of genes encoding transcription factors were found both up- and down-regulated. The high number of clones belonging to ferric iron and iron ion binding suggests an importance of these genes, and the association between these pathways and androstenone levels is not previously described. This study contributes to the understanding of the complex genetic system controlling and responding to androstenone levels in pig testis. The identification of new pathways and genes involved in the biosynthesis and metabolism of androstenone is an important first step towards finding molecular markers to reduce boar taint. Keywords: high vs low

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Systems genomics study reveals expression quantitative trait loci, regulator genes and pathways associated with boar taint in pigs (SNP60v2 BeadChip data set)

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