Comparative Genomic Hybridisation of 10 Ovarian Granulosa Cell tumors to ethnically-matched reference
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Sandrine Caburet
PROVIDER: E-MTAB-2873 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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2016-04-01 | E-GEOD-70782 | biostudies-arrayexpress
Project description:Differentiation of mouse embryonic stem cells (mESCs) is accompanied by global changes in replication timing. To elucidate this reorganization process and explore its potential impact on mouse development, we constructed genome-wide replication-timing profiles of 15 independent mouse cell types representing nine different stages of early mouse development, including all three germ layers. Overall, 45% of the genome exhibits significant changes in replication timing between cell types, indicating that replication-timing regulation is more extensive than previously estimated from neural differentiation. Intriguingly, analysis of early and late epiblast cell culture models suggest that the earliest changes in development include extensive lineage-independent early-to-late replication switches that are 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). These changes were stable in all subsequent lineages and involved a class of irreversibly silenced genes that were re-positioned closer to the nuclear periphery. Lineage-specific, late-to-early and early-to-late replication switches followed, which created cell-type specific replication profiles. Importantly, partially reprogrammed induced pluripotent stem cells (piPSCs) failed to restore ESC-specific replication timing and transcription programs particularly within regions of lineage-independent early-to-late replication changes, as well as the inactive X-chromosome. We conclude that lineage-independent, early-to-late replication-timing switches that occur in the post-implantation epiblast embody an epigenetic commitment to differentiation prior to germ layer specification. 22 cell lines, with a total of 36 individual replicates (i.e. 14 in duplicates, 8 in single replicates)
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Project description:We have investigated the role of the histone methyltransferase G9a in the establishment of silent nuclear compartments. Following conditional knockout of the G9a methyltransferase in mouse ESCs, 167 genes were significantly up-regulated, and no genes were strongly down-regulated. A partially overlapping set of 119 genes were up-regulated after differentiation of G9a-depleted cells to neural precursors. Promoters of these G9a-repressed genes were AT rich and H3K9me2 enriched but H3K4me3 depleted and were not highly DNA methylated. Representative genes were found to be close to the nuclear periphery, which was significantly enriched for G9a-dependent H3K9me2. Strikingly, although 73% of total genes were early replicating, more than 71% of G9a-repressed genes were late replicating, and a strong correlation was found between H3K9me2 and late replication. However, G9a loss did not significantly affect subnuclear position or replication timing of any non-pericentric regions of the genome, nor did it affect programmed changes in replication timing that accompany differentiation. We conclude that G9a is a gatekeeper for a specific set of genes localized within the late replicating nuclear periphery. 4 cell states each in duplicate (i.e. a total of 8 individual replicates)
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Project description:Extensive changes in replication timing occur during early mouse development, but their biological significance remains uncertain. To identify evolutionarily conserved features of replication timing and their relationships to epigenetic properties in humans, we profiled replication timing genome-wide in four human embryonic stem cell (hESC) lines, hESC-derived neural precursor cells (NPCs), lymphoblastoid cells, and two independently derived human induced pluripotent stem cell lines (hiPSCs). Results confirm the conservation of coordinately replicated megabase-sized units of chromosomes (replication domains) with stable cell type specific molecular boundaries that consolidate into larger replication domains during differentiation. Replication timing changes encompassed units of 400-800 kb and were coordinated with changes in transcription similar to mouse. Moreover, significant cell-type specific conservation of replication timing profiles was observed across regions of conserved synteny, despite significant species variation in the alignment of replication timing to isochore GC/LINE-1 content. Replication profiling also revealed a closer genome-wide epigenetic alignment of hESCs to mouse epiblast-derived stem cells (mEpiSCs) than to mouse ESCs. Finally, we identify a signature of chromatin modifications marking the boundaries of early replicating domains and a remarkably strong link between spatial proximity of chromatin as measured by Hi-C analysis and replication timing. Together, our results reveal evolutionarily conserved elements of the replication program in mammalian early development, demonstrate the power of replication profiling to identify important epigenetic distinctions between closely related stem cell populations (e.g. ESCs vs. EpiSCs), and strengthen the hypothesis that replication domains are structural and functional units of 3D chromosomal architecture. 8 cell types, with a total of 13 individual replicates (i.e. 5 in duplicates, 3 in single replicates)
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Project description:Facioscapulohumeral muscular dystrophy (FSHD) is linked to contraction of an array of tandem 3.3-kb repeats (D4Z4) at 4q35.2 from 11-100 copies to 1-10 copies. The extent to which D4Z4 contraction at 4q35.2 affects overall 4q35.2 chromatin organization remains unclear. Because DNA replication timing is highly predictive of long-range chromatin interactions, we generated genome-wide replication-timing profiles for FSHD and control myogenic precursor cells. We compared non-immortalized myoblasts from four FSHD patients and three control individuals to each other and to a variety of other human cell types. This study also represents the first genome-wide comparison of replication timing profiles in non-immortalized human cell cultures. Myoblasts from both control and FSHD individuals all shared a myoblast-specific replication profile. In contrast, male and female individuals were readily distinguished by monoallelic differences in replication timing at DXZ4 and other regions across the X chromosome affected by X inactivation. We conclude that replication timing is a robust cell-type specific feature that is unaffected by FSHD-related D4Z4 contraction. Profile comparison of myoblast cultures from four FSHD patients and three control individuals
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