Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression of lipid metabolism-related genes correlated with milk fatty acids in dairy cows

ABSTRACT: The aim of the present study was to correlate lipid metabolism genes in the mammary gland tissue affected by stage of lactation and nutrition to the resulting milk fatty acids composition in grazing dairy cows, and to classify milk fatty acid (FA) groups based on variations in lipid metabolism gene expression patterns. Identifying the relationship between lipid metabolism genes in the mammary gland tissue and the resulting milk fatty acid composition is expected to greatly contribute to our understanding of milk fatty acid metabolism and to enhance opportunities to improve milk fat composition through nutrition. In fact, SNCA, SCD5, and PNPLA2 lipid metabolism-related genes affected by unsaturated fatty acids supplementation, were found to strongly correlated to different milk FA groups, but also contributed most to the classification of these FA groups, suggesting a significant role in mediating the lipid metabolism in the mammary gland tissue and determining the milk fatty acids composition. A total of 28 Holstein-Friesian dairy cows in mid-lactation were blocked according to parity (2.4 ± 0.63 years), days in milk (DIM; 153 ± 32.8 days), milk yield (25.7 ± 3.08 kg/d) and fat content (4.3 ± 0.12%). Cows were then randomly assigned to four UFA-sources based on rapeseed, soybean, linseed or a mixture of the three oils for 23 days (Period I) after which, all 28 cows were switched to a control diet for an additional 28 days (Period II). On the last day of both periods, mammary gland biopsies were taken to study genome-wide differences in lipid metabolism gene expression.

ORGANISM(S): Bos taurus

SUBMITTER: Nuria Mach

PROVIDER: E-GEOD-20908 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The objective of this study was to determine the effect of the DGAT1 K232A polymorphism on the global mRNA expression pattern of genes in the mammary gland tissue of grazing dairy cows in order to get more insight into the effects of this polymorphism on the physiology of the mammary glandgland of grazing dairy cows. Microarray analysis was used to identify genes whose expression was affected by the DGAT1 polymorphism in the mammary gland biopsies of 9 A232A cows, 13 K232A cows, and 4 K232K cows. The Microarray Analysis of Variance (MAANOVA) and Factor Analysis for Multiple Testing method (FAMT) were used to associate the expression of the genes present on Affymettrix Bovine Genome Arrays with the DGAT1 polymorphism. The data was also analysed at the level of functional modules by gene set enrichment analysis. In this experimental setting, DGAT1 polymorphism did not modify milk yield and composition significantly, although changes occurred in the yields of C14:0, C16:1cis-9, and some long chain fatty acids in milk. The DGAT1 polymorphism resulted in 30 differentially expressed genes related to cell growth, proliferation and development, signalling, remodelling and immune system. At the functional level, the pathways most affected by DGAT1 polymorphism were related to lipid biosynthesis, which likely reflected counter mechanisms of mammary tissue to respond to changes in milk FA composition, signalling, as well as immune system responses. A total of 28 Holstein-Friesian dairy cows in mid-lactation (DIM; 153 M-BM-1 32.8 days), milk yield (25.7 M-BM-1 3.08 kg/d) and fat content (4.3 M-BM-1 0.12%) were used in the study. Two consecutive milk samples (a.m. and p.m. milking) were obtained and pooled. One aliquot was stored at 4M-BM-0C until analysis of fat, protein and lactose percentage, and another aliquot was frozen at -20M-BM-0C until analysis for FA composition by gas chromatography. Specific details regarding the analysis of FA in milk are presented in Mach et al. (2011). Approximately 750 to 1,000 mg of mammary tissue from each cow was obtained by surgical biopsy. One part of the tissue was used for isolation of DNA and the other for extraction of the RNA. Genotyping of the DGAT1 polymorphism was performed using a TaqMan allelic discrimination method in an Applied Biosystems 7500 Real-Time PCR System (Applied Biosystems) as described by Schennink et al. (2007). The genotype at the DGAT1 locus was designated KK, KA, or AA for homozygous Lysine, heterozygous Lysine/Alanine, or homozygous Alanine, respectively. Microarray analysis was used to identify genes whose expression was affected by the DGAT1 polymorphism in the mammary gland biopsies of 11 A232A cows, 13 K232A cows, and 4 K232K cows. Total RNA from mammary gland tissue (50-100 mg) was isolated using TRIzol reagent (Invitrogen, Breda, The Netherlands), following the manufacturerM-bM-^@M-^Ys instructions. The RNA purity and concentrations were determined using a NanoDrop ND-1000 spectrophotometer (Isogen, Maarssen, the Netherlands), and the RNA quality was assessed using the BioAnalyzer 2100 (Agilent Technologies, Amsterdam, the Netherlands). The RNA of each biopsy was amplified, biotin-labeled, and hybridized to single-dye Affymetrix GeneChipM-BM-. Bovine Genome Array (#900493) by ServiceXS (Leiden, the Netherlands)

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Gene expression of lipid metabolism-related genes correlated with milk fatty acids in dairy cows

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