Fig. 1

Global DNA methylation level measured by LUMA is low in bovine sperm. a Global DNA methylation level in bovine sperm and PBMCs. Each colored dot represents one individual. The black dots and horizontal bars indicate the means ± standard deviations. The difference between cell types is highly significant (p < 2.2e-16, Welch’s t-test). b Global DNA methylation level of sperm in four bovine breeds. The effect of the breed on CCGG methylation is significant (p < 0.05, one-way analysis of variance for independent samples). Significant differences between breeds are indicated by different letters (p < 0.05, multiple comparisons of means using Tukey’s test). c, d Global DNA methylation level in bull and ram samples. Significant differences between independent samples are indicated by asterisks (p < 0.05, permutation test), while paired samples are connected by plain lines. c Global DNA methylation level in blood cells and semen for bulls (n = 6) and rams (n = 5). The p-values are indicated in red (bulls) and green (rams) for comparisons involving samples collected from the same individuals (permutation test for paired samples). d Global DNA methylation level in bull (n = 6) and ram (n = 4) sperm cells from fresh and frozen semen. The difference between fresh and frozen semen is not significant. e Global sperm DNA methylation level and CCGG distribution in several mammalian species. The CCGG sites were annotated relative to gene features, CpG density and overlapping repeats. For each genomic feature examined, species with extreme values are indicated (min. and max.). In the bovine genome, CCGG sites are particularly enriched in CpG islands and satellites, and are within the ranges of other species for other genomic features. SD: standard deviation