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:The three-dimensional (3D) organization of chromosomes is crucial for packaging a large mammalian genome into a confined nucleus and ensuring proper nuclear functions in somatic cells. However, the packaging of the much more condensed sperm genome is fundamentally different and not as well understood. In this study, we resolved the 3D whole-genome structures of a single mammalian sperm cell using an enhanced chromosome conformation capture assay. The reconstructed genome structures accurately delineate the species-specific nuclear morphologies for both human and mouse sperm. We discovered that sperm genomes are divided into chromosomal territories and A/B compartments, similarly as somatic cells. However, neither human nor mouse sperm chromosomes contain topologically associating domains or chromatin loops. These results suggest that the fine-scale chromosomal organization of mammalian sperm fundamentally differs from that of somatic cells.
Project description:The three-dimensional (3D) organization of chromosomes is crucial for packaging a large mammalian genome into a confined nucleus and ensuring proper nuclear functions in somatic cells. However, the packaging of the much more condensed sperm genome is fundamentally different and not as well understood. In this study, we resolved the 3D whole-genome structures of a single mammalian sperm cell using an enhanced chromosome conformation capture assay. The reconstructed genome structures accurately delineate the species-specific nuclear morphologies for both human and mouse sperm. We discovered that sperm genomes are divided into chromosomal territories and A/B compartments, similarly as somatic cells. However, neither human nor mouse sperm chromosomes contain topologically associating domains or chromatin loops. These results suggest that the fine-scale chromosomal organization of mammalian sperm fundamentally differs from that of somatic cells.
Project description:The three-dimensional (3D) organization of chromosomes is crucial for packaging a large mammalian genome into a confined nucleus and ensuring proper nuclear functions in somatic cells. However, the packaging of the much more condensed sperm genome is fundamentally different and not as well understood. In this study, we resolved the 3D whole-genome structures of a single mammalian sperm cell using an enhanced chromosome conformation capture assay. The reconstructed genome structures accurately delineate the species-specific nuclear morphologies for both human and mouse sperm. We discovered that sperm genomes are divided into chromosomal territories and A/B compartments, similarly as somatic cells. However, neither human nor mouse sperm chromosomes contain topologically associating domains or chromatin loops. These results suggest that the fine-scale chromosomal organization of mammalian sperm fundamentally differs from that of somatic cells.
Project description:IntroductionRecent interest in sperm epigenetics has stemmed from its implication in sperm DNA quality, sperm fertility, environmental toxicity, and transgenerational inheritance. Sperm epigenetic data may be significantly affected by somatic DNA contamination, resulting in misleading conclusions. However, detecting and dealing with somatic DNA contamination in semen samples can be a challenging task.MethodsIn the present study, we worked out a detailed and robust plan to deal with somatic cell DNA contamination in sperm epigenetic studies in order to draw error-free scientific conclusions. Apart from incorporating simple quality checks, such as microscopic examination and somatic cell lysis buffer (SCLB) treatment, we compared the Infinium Human Methylation 450K BeadChip data for sperm and blood samples to identify the CpG sites that were highly methylated in blood samples in comparison to sperm, but were unrelated to infertility.Results and discussionThe comparison of Infinium Human Methylation 450K BeadChip data for sperm and blood samples identified 9564 CpG sites that can be used as markers for analyzing somatic DNA contamination. We have put together a comprehensive plan including evaluation under a microscope, SCLB treatment, inclusion of CpG biomarkers for sample quality evaluation, and applying a 15% cut off at the time of data analysis to completely eliminate the influence of somatic DNA contamination in sperm epigenetic studies. We conclude that if this comprehensive plan is followed, the influence of somatic DNA contamination in sperm epigenetic studies can be completely eliminated.
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.