Project description:The timing of DNA replication is an important developmentally regulated regional property that is correlated with gene expression, chromatin state, GC content, subnuclear structure. These correlations reflect the variable accessibility of origins to a limited pool of initiation factors within different context, and the extent to which changes in replication timing occur during differentiation. Therefore, temporal order of genome replication could be sufficient to identify the cell type. Several studies for characterizing DNA replication have been done using many different types of cells, however, the pattern of it in the totipotent cells is still entirely unknown. In this study, we try to understand the molecular basis underlying totipotency by identifying specific DNA replication features found exclusively in totipotent cells.
Project description:Replication timing is cell type specific, is tightly linked to the 3D nuclear organisation of the genome and is considered an epigenetic fingerprint. In spite of its importance in maintaining the epigenome the developmental regulation of replication timing in mammals in vivo has not been explored. Here, using single cell Repli-seq, we generated the genome-wide replication timing maps of mouse embryos from the zygote until the blastocyst stage.
Project description:This SuperSeries is composed of the following subset Series: GSE17980: Genome-Wide Dynamics of Replication Timing Revealed by In Vitro Models of Mouse Embryogenesis (Expression) GSE17983: Genome-Wide Dynamics of Replication Timing Revealed by In Vitro Models of Mouse Embryogenesis (WG_CGH; Replication Timing) GSE17980 (Expression): 8 cell lines, with a total of 14 individual replicates (i.e. 6 in duplicates, 2 in single replicates) GSE17983 (WG_CGH; Replication Timing): 22 cell lines, with a total of 36 individual replicates (i.e. 14 in duplicates, 8 in single replicates)
Project description:The timing of DNA replication is an important developmentally regulated regional property that is correlated with gene expression, chromatin state, GC content, subnuclear structure. These correlations reflect the variable accessibility of origins to a limited pool of initiation factors within different context, and the extent to which changes in replication timing occur during differentiation. Therefore, temporal order of genome replication could be sufficient to identify the cell type. A lot of studies for characterizing DNA replication have been done using many different types of cells, however, the pattern of it in the totipotent cells is still entirely unknown. In this study, we try to understand the molecular basis underlying totipotency by identifying specific DNA replication features found exclusively in totipotent cells.
Project description:Differentiation of mouse embryonic stem cells (mESCs) is accompanied by changes in replication timing. To explore the relationship between replication timing and cell fate transitions, we constructed genome-wide replication-timing profiles of 22 independent mouse cell lines representing 10 stages of early mouse development, and transcription profiles for seven of these stages. Replication profiles were cell-type specific, with 45% of the genome exhibiting significant changes at some point during development that were generally coordinated with changes in transcription. Comparison of early and late epiblast cell culture models revealed a set of lineage-independent early-to-late replication switches completed at a stage equivalent to the post-implantation epiblast, prior to germ layer specification and down-regulation of key pluripotency transcription factors (Oct4/Nanog/Sox2) and coinciding with the emergence of compact chromatin near the nuclear periphery. These changes were conserved in all subsequent lineages and involved a group of irreversibly down-regulated genes, at least some of which were repositioned closer to the nuclear periphery. Importantly, many genomic regions of partially reprogrammed induced pluripotent stem cells (piPSCs) failed to re-establish ESC-specific replication timing and transcription programs. These regions were enriched for lineage-independent early-to-late changes, which in female cells included the inactive X-chromosome. Taken together, we demonstrate that replication-timing changes are extensive during development. Moreover, a distinct set of lineage-independent, early-to-late changes completed in and stably maintained after the post-implantation epiblast stage is difficult to reprogram and therefore coincides with an epigenetic commitment to differentiation prior to germ layer specification. 8 cell lines, with a total of 14 individual replicates (i.e. 6 in duplicates, 2 in single replicates)
Project description:DNA replication is initiated at multiple sites or origins enriched with AT-rich sequences at various times during the S-phase. While current studies of genome-wide DNA replication profiles have focused on the timing of replication and the location of origins, the efficiency of replication/firing at various origins remains unclear. In this study, we show different efficiencies of DNA replication at various loci by using ORF-specific DNA microarrays. DNA copy-number increases as a function of time at individual loci are approximated to near-sigmoidal models for estimation of replication initiation and completion timings in HU-challenged cells. Duplicating times (from initiation to completion) vary from loci to loci, partly contributing to various firing efficiencies at origins. DNA replication timing profiles are strikingly similar to the reported patterns of enriched ssDNA, suggesting that majority stalled forks are restored for resumption of DNA replication. Although the DNA replication timing profiles are disrupted in HU-challenged cds1? cells, ~85% of potential origins overlapped with those found in wild type cells, significantly, most of which represents inefficiently fired origins in wild type cells. Together, our result indicates that replication checkpoint plays a role in monitoring efficient origins and thus maintaining global DNA replication patterns in HU-challenged cells. Keywords: WT or Cds1 HU synchronized cells released in HU free media and harvested at different time points vs WT or Cds1 synchronized with HU for 3 hrs. We analyzed 32 arrays for WT and 38 arrays for Cds1 cells which were synchronized with HU and released in HU free media and harvested at different time points. At least two biological repeats were done for each time points.