Project description:Cancer risk by environmental exposure is modulated by an individual’s genetics and age at exposure. This age-specific period of susceptibility is referred to as a “Window of Susceptibility” (WOS). Radiation exposures poses a high breast cancer risk for women between the early childhood and young adult stage and is reduced in the mid-30s. Rats have a similar WOS for developing breast cancer. Previous studies have identified a looping interaction between a genomic region in the mammary carcinoma susceptibility Mcs5c locus and a known cancer gene, PAPPA. However, the global role of three-dimensional organization in the WOS is not known. Therefore, we generated Hi-C and RNA-seq data in rat mammary epithelial cells within and outside WOS. We compared the temporal changes in chromosomal looping to those in expression and find that interactions that have significantly higher counts within WOS are significantly enriched for genes upregulated in WOS. To systematically identify higher-order changes in 3D genome organization, we developed an approach that combines network enhancement to smooth the Hi-C matrices followed by multitask non-negative matrix factorization (NMF) to identify clusters of interacting loci. We found that large-scale topological re-organizations are enriched for differential interactions within and outside the WOS timepoints. Finally, we mapped previously published breast-cancer associated human GWAS variants to rat loci and identified the corresponding rat ortholog gene interacting with the loci. Many of the associated rat genes participate in differential interactions, recapitulate the human SNP- gene interactions and are associated with breast cancer. Our results suggest that WOS-specific changes in 3D genome organization are linked to transcriptional changes that may increase susceptibility to breast cancer.
Project description:Cancer risk by environmental exposure is modulated by an individual’s genetics and age at exposure. This age-specific period of susceptibility is referred to as a “Window of Susceptibility” (WOS). Radiation exposures poses a high breast cancer risk for women between the early childhood and young adult stage and is reduced in the mid-30s. Rats have a similar WOS for developing breast cancer. Previous studies have identified a looping interaction between a genomic region in the mammary carcinoma susceptibility Mcs5c locus and a known cancer gene, PAPPA. However, the global role of three-dimensional organization in the WOS is not known. Therefore, we generated Hi-C and RNA-seq data in rat mammary epithelial cells within and outside WOS. We compared the temporal changes in chromosomal looping to those in expression and find that interactions that have significantly higher counts within WOS are significantly enriched for genes upregulated in WOS. To systematically identify higher-order changes in 3D genome organization, we developed an approach that combines network enhancement to smooth the Hi-C matrices followed by multitask non-negative matrix factorization (NMF) to identify clusters of interacting loci. We found that large-scale topological re-organizations are enriched for differential interactions within and outside the WOS timepoints. Finally, we mapped previously published breast-cancer associated human GWAS variants to rat loci and identified the corresponding rat ortholog gene interacting with the loci. Many of the associated rat genes participate in differential interactions, recapitulate the human SNP- gene interactions and are associated with breast cancer. Our results suggest that WOS-specific changes in 3D genome organization are linked to transcriptional changes that may increase susceptibility to breast cancer.
Project description:Cancer risk by environmental exposure is modulated by an individual's genetics and age at exposure. This age-specific period of susceptibility is referred to as the "Window of Susceptibility" (WOS). Rats have a similar WOS for developing breast cancer. A previous study in rat identified an age-specific long-range regulatory interaction for the cancer gene, Pappa, that is associated with breast cancer susceptibility. However, the global role of three-dimensional genome organization and downstream gene expression programs in the WOS is not known. Therefore, we generated Hi-C and RNA-seq data in rat mammary epithelial cells within and outside the WOS. To systematically identify higher-order changes in 3D genome organization, we developed NE-MVNMF that combines network enhancement followed by multitask non-negative matrix factorization. We examined three-dimensional genome organization dynamics at the level of individual loops as well as higher-order domains. Differential chromatin interactions tend to be associated with differentially up-regulated genes with the WOS and recapitulate several human SNP-gene interactions associated with breast cancer susceptibility. Our approach identified genomic blocks of regions with greater overall differences in contact count between the two time points when the cluster assignments change and identified genes and pathways implicated in early carcinogenesis and cancer treatment. Our results suggest that WOS-specific changes in 3D genome organization are linked to transcriptional changes that may influence susceptibility to breast cancer.
Project description:Breast cancer progression entails intricate, multi-level alterations in genome organization and expression. To gain insights into the modifications in chromatin's three-dimensional (3D) structure during breast cancer progression, we conducted an analysis combining Hi-C data with lamina-associated domains (LADs), epigenomic marks, and gene expression in an in vitro model of breast cancer progression. Our results reveal that while the fundamental properties of topologically associating domains (TADs) remain largely stable, significant changes occur in the organization of compartments and subcompartments. These changes are closely correlated with alterations in the expression of oncogenic genes. We also observed a restructuring of TAD-TAD interactions, coinciding with a loss of spatial compartmentalization and radial positioning of the 3D genome. Notably, we identified a previously unrecognized interchromosomal insertion event, wherein a locus on chromosome 8 housing the MYC oncogene becomes inserted into a highly active region on chromosome 10. This insertion event leads to the formation of de novo enhancer contacts and activation of the oncogene, illustrating how structural variants can interact with the 3D genome to drive oncogenic states. In summary, our findings provide evidence for the degradation of genome organization at multiple scales during breast cancer progression revealing the complex interplay between genomic structure and oncogenic processes.
Project description:Breast cancer progression entails intricate, multi-level alterations in genome organization and expression. To gain insights into the modifications in chromatin's three-dimensional (3D) structure during breast cancer progression, we conducted an analysis combining Hi-C data with lamina-associated domains (LADs), epigenomic marks, and gene expression in an in vitro model of breast cancer progression. Our results reveal that while the fundamental properties of topologically associating domains (TADs) remain largely stable, significant changes occur in the organization of compartments and subcompartments. These changes are closely correlated with alterations in the expression of oncogenic genes. We also observed a restructuring of TAD-TAD interactions, coinciding with a loss of spatial compartmentalization and radial positioning of the 3D genome. Notably, we identified a previously unrecognized interchromosomal insertion event, wherein a locus on chromosome 8 housing the MYC oncogene becomes inserted into a highly active region on chromosome 10. This insertion event leads to the formation of de novo enhancer contacts and activation of the oncogene, illustrating how structural variants can interact with the 3D genome to drive oncogenic states. In summary, our findings provide evidence for the degradation of genome organization at multiple scales during breast cancer progression revealing the complex interplay between genomic structure and oncogenic processes.
Project description:Breast cancer progression entails intricate, multi-level alterations in genome organization and expression. To gain insights into the modifications in chromatin's three-dimensional (3D) structure during breast cancer progression, we conducted an analysis combining Hi-C data with lamina-associated domains (LADs), epigenomic marks, and gene expression in an in vitro model of breast cancer progression. Our results reveal that while the fundamental properties of topologically associating domains (TADs) remain largely stable, significant changes occur in the organization of compartments and subcompartments. These changes are closely correlated with alterations in the expression of oncogenic genes. We also observed a restructuring of TAD-TAD interactions, coinciding with a loss of spatial compartmentalization and radial positioning of the 3D genome. Notably, we identified a previously unrecognized interchromosomal insertion event, wherein a locus on chromosome 8 housing the MYC oncogene becomes inserted into a highly active region on chromosome 10. This insertion event leads to the formation of de novo enhancer contacts and activation of the oncogene, illustrating how structural variants can interact with the 3D genome to drive oncogenic states. In summary, our findings provide evidence for the degradation of genome organization at multiple scales during breast cancer progression revealing the complex interplay between genomic structure and oncogenic processes.
Project description:Triple-negative breast cancer (TNBC) is malignant cancer with a high risk of recurrence. To date, the underlying 3D chromatin organizations of TNBC have remained unclear. Here, using in situ Hi-C, we characterized the 3D chromatin organizations in cells representing five distinct subtypes of breast cancer (including TNBC) and TNBC tissues, compared to normal cells/tissues. We found that the global and local 3D architectures are severely disrupted in TNBC cells. Importantly, we detected CTCF-dependent TNBC-susceptible loss/gain of 3D chromatin organizations and found that these changes were strongly associated with perturbed chromatin accessibility and transcriptional dysregulations. Although some discrepancies exist between TNBC cell lines and tissues, we observed that perturbed local 3D architectures found in TNBC cells are partially conserved in TNBC tissues. Furthermore, we discovered distinct tissue-specific chromatin loops by comparing normal and TNBC tissues. Collectively, our findings provide important features of 3D chromatin organization in TNBC.