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It has been established that the DNAm level of mammalian genomes increases with age, although this relationship seems to differ across the regions of the genome. In general, it has been recognized that DNAm in the promoter region of genes indicates transcriptional suppression while hypomethylation is associated with transcriptional activation and increased gene expression 2.ĭNA methylation profiles are dynamic and susceptible to factors such as age 4, 5, 6, diet 7, 8, sex 9, and exposure to diseases 10. In mammalian genomes, CpG islands are greatly under-represented due to spontaneous evolutionary deamination of 5-methylcytosine to thymine and are usually located within or near promoters and first exons of housekeeping genes 3. This modification exists throughout the genome with remarkably less abundance in cytosine-guanine (CpG) islands 2. Results suggest DNAm profiles are influenced by both genetics and the environmental effect of age in beef cattle.ĭNA methylation (DNAm) is an epigenetic mark characterized by a modification of the chromatin structure in mammals 1. In addition, DNAm level increased with age in regions enriched in CpG and decreased in regions deficient in CpG. The DNAm level across the genome increased with age in the promoter and 5′ UTR and decreased in the exonic, intronic, 3′ UTR, and intergenic regions. The average age effect on DNAm level varied among genomic regions. Heritability estimate of DNAm load was 0.45. Heritability estimates of DNAm levels ranged from 0.18 to 0.72, with a similar average across all regions and chromosomes. Genetic parameters for DNAm were obtained from an animal model based on the genomic relationship matrix, including the fixed effects of age and breed composition.
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All animals were genotyped, and DNAm was obtained using the Infinium array HorvathMammalMethylChip40.
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Blood samples were collected from cows ranging from 217 to 3,192 days (0.6 to 8.7 years) of age ( n = 136). The objectives of this study were to estimate the heritability and age effects of site-specific DNAm (DNAm level) and cumulative DNAm across all sites (DNAm load) in beef cattle. DNA methylation (DNAm) has been considered a promising indicator of biological age in mammals and could be useful to increase the accuracy of phenotypic prediction in livestock.