Project description:The purpose of this data set was to identify the affects of somatic cell introduction of the methylation results of the sperm samples. This data was then used to help build a computational tool to properly identify somatic cell contamination within a sperm sample.
Project description:To establish contamination profiles, the sperm donors with normal sperm counts were analyzed using an Infinium HumanMethylation450 array. Somatic cell lysis, sperm isolation, DNA extraction, and bisulfite conversion were performed as described by Aston et al. The bisulfite converted sperm DNA was hybridized to Illumina Infinium HumanMethylation450K microarrays at the University of Utah and run as recommended by the manufacturer (Bibikova et al. 2011). Unpaired blood samples were extracted using Qiagen's DNeasy Blood and Tissue kit and bisulfite converted using Zymo's EZ DNA Methylation kit. All procedures were performed according to the instructions of the manufacturer. Four permutations were run on each sample, including pure blood, half blood and half sperm by DNA concentration, half blood and half sperm by cell count, and pure sperm (n = 16). Concentration was normalized using a spectrophotometer. A Makler cell counting chamber was used to count white blood cells and sperm, which were then normalized in a 1:1 ratio.
Project description:Epidemiological studies in humans suggest that acquired paternal traits, such as obesity, are associated with a higher risk of fathering small for gestational age offspring. Studies in non-human mammals suggest that such associations could be mediated by DNA methylation changes in spermatozoa that influence offspring development in utero. Human obesity is associated with differential DNA methylation in peripheral blood. It is unclear, however, whether this differential DNA methylation is reflected in less readily available tissues such as spermatozoa. In this study, we profiled genome-wide DNA methylation with the Infinium MethylationEPIC array in matched samples of human blood and sperm from lean (discovery n = 47; replication n = 21) and obese (n = 22) healthy males of proven fertility. To characterize sperm-specific DNA methylation signatures, we compared spermatozoal DNA methylation data to that of nearly 6,000 somatic tissue samples available on the Gene Expression Omnibus database. We studied covariation patterns between whole blood and sperm and investigated consistent obesity-associated DNA methylation differences.
Project description:BACKGROUND: In previous studies using candidate gene approaches, low sperm count (oligospermia) has been associated with altered sperm mRNA content and DNA methylation in both imprinted and non-imprinted genes. We performed a genome-wide analysis of sperm DNA methylation and mRNA content to test for associations with sperm function. METHODS AND RESULTS: Sperm DNA and mRNA were isolated from 21 men with a range of semen parameters presenting to a tertiary male reproductive health clinic. DNA methylation was measured with the Illumina Infinium array at 27,000 CpG loci. Unsupervised clustering of methylation data differentiated the 21 sperm samples by their motility values. Recursively partitioned mixture modeling (RPMM) of methylation data resulted in four distinct methylation profiles that were significantly associated with sperm motility (P=0.01). Linear models of microarray analysis (LIMMA) was performed based on motility and identified 9,189 CpG loci with significantly altered methylation (Q<0.05) in the low motility samples, with many loci located in genes associated with subfertility and epigenetic regulation. In the low motility samples, the majority of disrupted CpG loci (80%) were hypomethylated. Of the aberrantly methylated CpGs, 194 were associated with imprinted genes almost equally distributed into hypermethylated (predominantly paternally expressed) and hypomethylated (predominantly maternally expressed) groups. Sperm mRNA was measured with the Human Gene 1.0 ST Affymetrix GeneChip Array. LIMMA analysis based on motility identified 20 candidate transcripts as differentially expressed in low motility sperm, including HDAC1 (NCBI 3065), SIRT3 (NCBI 23410), and DNMT3A (NCBI 1788). Altered expression of these epigenetic regulatory genes was associated with RPMM DNA methylation class. CONCLUSIONS: Using integrative genome-wide approaches to study epigenetic and gene expression patterns in human sperm we identified CpG methylation profiles and mRNA alterations associated with low sperm motility, and that low motility sperm may have aberrant genome-wide hypomethylation due to excess HDAC1 activity. See summary above
Project description:BACKGROUND: In previous studies using candidate gene approaches, low sperm count (oligospermia) has been associated with altered sperm mRNA content and DNA methylation in both imprinted and non-imprinted genes. We performed a genome-wide analysis of sperm DNA methylation and mRNA content to test for associations with sperm function. METHODS AND RESULTS: Sperm DNA and mRNA were isolated from 21 men with a range of semen parameters presenting to a tertiary male reproductive health clinic. DNA methylation was measured with the Illumina Infinium array at 27,000 CpG loci. Unsupervised clustering of methylation data differentiated the 21 sperm samples by their motility values. Recursively partitioned mixture modeling (RPMM) of methylation data resulted in four distinct methylation profiles that were significantly associated with sperm motility (P=0.01). Linear models of microarray analysis (LIMMA) was performed based on motility and identified 9,189 CpG loci with significantly altered methylation (Q<0.05) in the low motility samples, with many loci located in genes associated with subfertility and epigenetic regulation. In the low motility samples, the majority of disrupted CpG loci (80%) were hypomethylated. Of the aberrantly methylated CpGs, 194 were associated with imprinted genes almost equally distributed into hypermethylated (predominantly paternally expressed) and hypomethylated (predominantly maternally expressed) groups. Sperm mRNA was measured with the Human Gene 1.0 ST Affymetrix GeneChip Array. LIMMA analysis based on motility identified 20 candidate transcripts as differentially expressed in low motility sperm, including HDAC1 (NCBI 3065), SIRT3 (NCBI 23410), and DNMT3A (NCBI 1788). Altered expression of these epigenetic regulatory genes was associated with RPMM DNA methylation class. CONCLUSIONS: Using integrative genome-wide approaches to study epigenetic and gene expression patterns in human sperm we identified CpG methylation profiles and mRNA alterations associated with low sperm motility, and that low motility sperm may have aberrant genome-wide hypomethylation due to excess HDAC1 activity.
Project description:In human sperm, preserved histones evading histone-to-protamine replacement were observed in certain genes and gene promoters, but also in distal intergenic and repetitive DNA regions. The substantiality of the latter and its putative biological role are still a subject of hot debate. To shed more light on this issue we analyzed H4K20me3, a histone mark regulating heterochromatic and repetitive DNA in somatic cells, which was recently detected in human sperm. Our immunohistochemical and western blot analyses revealed the presence of H4K20me3 in male germ cells at every stage of spermatogenesis and in mature sperms, respectively. By ChIP-sequencing of the motile sperm fractions from three biological replicates we found 4.56% of the sperm genome to be occupied by H4K20me3. By comparing the genome-wide binding sites of H4K20me3 in sperm cells and somatic cells (K562) we found correspondences in 77% of respective peaks. The majority of binding sites (70%) were detected in distal intergenic and intron regions. Intriguingly, H4K20me3 enrichments could be observed in both somatic and sperm cells within satellite repeats and retrotransposons, particularly in long interspersed nuclear repeats (LINEs) and retrotransposons containing long terminal repeats (LTR-retrotransposons). Broad cluster arrangements and strong enrichments in olfactory receptor genes were also characteristic for H4K20me3. This is the first time H4K20me3 is characterized at the genome-wide level in human sperm and compared to somatic cells. Our results reveal that H4K20me3 constitutes the majority of histones preserved in matured human sperm and maintains a somatic-like distribution pattern.
Project description:Mammalian sperm exhibit an unusual and heavily-compacted genomic packaging state. In addition to its role in organizing the compact and hydrodynamic sperm head, it has been proposed that sperm chromatin architecture helps to program gene expression in the early embryo. Scores of genome-wide surveys in sperm have reported patterns of chromatin accessibility, histone localization, histone modification, and chromosome folding. Here, we revisit these studies in light of recent reports that sperm obtained from the mouse epididymis are contaminated with low levels of cell-free chromatin. In the absence of proper sperm lysis we readily recapitulate multiple prominent genome-wide surveys of sperm chromatin, suggesting that these profiles primarily reflect contaminating cell-free chromatin. Removal of cell-free DNA, along with appropriate lysis conditions, are required to reveal a sperm chromatin state distinct from any yet reported. Using ATAC-Seq to explore relatively accessible genomic loci, we identify a landscape of open loci associated with genes expressed during late spermiogenesis. Histone modification and chromosome folding studies also strongly support the hypothesis that prior studies suffer from contamination, but technical challenges associated with reliably preserving the architecture of the compacted sperm head prevent us from confidently assaying true localization patterns for these epigenetic marks. Together, our studies strongly argue that our knowledge of mammalian chromosome packaging remains largely incomplete, and motivate future efforts to more accurately characterize genome organization in mature sperm.