Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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The distribution of genomic variations in human iPSCs is related to replication timing reorganization during reprogramming [NimbleGen]

ABSTRACT: Cell fate change involves significant genome reorganization, including change in replication timing, but how these changes are related to genetic variation has not been examined. To study how change in replication timing that occurs during reprogramming impacts the copy number variation (CNV) landscape, we generated genome-wide replication timing profiles of induced pluripotent stem cells (iPSCs) and their parental fibroblasts. A significant portion of the genome changes replication timing as a result of reprogramming, indicative of overall genome reorganization. We found that early and late replicating domains in iPSCs are differentially affected by copy number gains and losses, and that in particular CNV gains accumulate in regions of the genome that change to earlier replication during the reprogramming process. This differential relationship was present irrespective of reprogramming method. Overall, our findings reveal a functional association between reorganization of replication timing and the CNV landscape that emerges during reprogramming. 3 cell lines, all in duplicates

ORGANISM(S): Homo sapiens

SUBMITTER: Hu Li

PROVIDER: E-GEOD-55397 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Abnormal replication timing has been observed in cancer but no study has comprehensively evaluated this misregulation. We generated genome-wide replication timing profiles for pediatric leukemias from 17 patients and 3 cell lines, as well as normal B and T cells. Non-leukemic EBV-transformed lymphoblastoid cell lines displayed highly stable replication timing profiles that were more similar to normal T cells than to leukemias. Leukemias were more similar to each other than to B and T cells but were considerably more heterogeneous than non-leukemic controls. Some differences were patient-specific while others were found in all leukemic samples, potentially representing early epigenetic events. Differences encompassed large segments of chromosomes and included genes implicated in other types of cancer. Remarkably, differences that distinguished leukemias aligned in register to the boundaries of developmentally regulated replication timing domains that distinguish normal cell types. Most changes did not coincide with copy number variation or translocations. However, many of the changes that were associated with translocations in some leukemias were also shared between all leukemic samples independent of the genetic lesion, suggesting that they precede and possibly predispose chromosomes to the translocation. Altogether, our results identify sites of abnormal developmental control of DNA replication in cancer that reveal the significance of replication timing boundaries to chromosome structure and function and support the replication domain model of replication timing regulation. They also open new avenues of investigation into the chromosomal basis of cancer and provide a potential novel source of epigenetic cancer biomarkers. Four karyotypically normal B-lymphoblastoid cell types with two replicates each, one peripheral T-lymphoblast replicate, 3 leukemic cell lines with 1-3 replicates each, 17 patient samples with 1-3 replicates each (total of 40 individual replicates)

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The distribution of genomic variations in human iPSCs is related to replication timing reorganization during reprogramming [NimbleGen]

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