Life Sciences Research for Lifelong Health

Peter Fraser

Please note, Peter now also leads a research group at Florida State University. Visit his page there for full details of his current research.

Research Summary

Dynamic changes in chromatin and chromosome architecture regulates patterns of cellular gene expression during differentiation and development, or in response to environmental signals. Our research looks at various levels of chromatin, chromosome and nuclear structure, from individual nucleosome modifications to the dynamic 3D structure of chromosomes and their inter-relationships in the nucleus and how they affect genome functions.

Latest Publications

Allele-specific control of replication timing and genome organization during development.
Rivera-Mulia JC, Dimond A, Vera D, Trevilla-Garcia C, Sasaki T, Zimmerman J, Dupont C, Gribnau J, Fraser P, Gilbert DM

DNA replication occurs in a defined temporal order known as the replication-timing (RT) program. RT is regulated during development in discrete chromosomal units, coordinated with transcriptional activity and 3D genome organization. Here, we derived distinct cell types from F1 hybrid musculus X castaneus mouse crosses and exploited the high single nucleotide polymorphism (SNP) density to characterize allelic differences in RT (Repli-seq), genome organization (Hi-C and promoter-capture Hi-C), gene [removed]total nuclear RNA-seq) and chromatin accessibility (ATAC-seq). We also present HARP: a new computational tool for sorting SNPs in phased genomes to efficiently measure allele-specific genome-wide data. Analysis of six different hybrid mESC clones with different genomes (C57BL/6, 129/sv and CAST/Ei), parental configurations and gender revealed significant RT asynchrony between alleles across ~12% of the autosomal genome linked to sub-species genomes but not to parental origin, growth conditions or gender. RT asynchrony in mESCs strongly correlated with changes in Hi-C compartments between alleles but not SNP density, gene expression, imprinting or chromatin accessibility. We then tracked mESC RT asynchronous regions during development by analyzing differentiated cell types including extraembryonic endoderm stem (XEN) cells, 4 male and female primary mouse embryonic fibroblasts (MEFs) and neural precursor cells (NPCs) differentiated in vitro from mESCs with opposite parental configurations. We found that RT asynchrony and allelic discordance in Hi-C compartments seen in mESCs was largely lost in all differentiated cell types, coordinated with a more uniform Hi-C compartment arrangement, suggesting that genome organization of homologues converges to similar folding patterns during cell fate commitment.

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Genome research, , 1549-5469, , 2018

PMID: 29735606

Long-Range Enhancer Interactions Are Prevalent in Mouse Embryonic Stem Cells and Are Reorganized upon Pluripotent State Transition.
Novo CL, Javierre BM, Cairns J, Segonds-Pichon A, Wingett SW, Freire-Pritchett P, Furlan-Magaril M, Schoenfelder S, Fraser P, Rugg-Gunn PJ

Transcriptional enhancers, including super-enhancers (SEs), form physical interactions with promoters to regulate cell-type-specific gene expression. SEs are characterized by high transcription factor occupancy and large domains of active chromatin, and they are commonly assigned to target promoters using computational predictions. How promoter-SE interactions change upon cell state transitions, and whether transcription factors maintain SE interactions, have not been reported. Here, we used promoter-capture Hi-C to identify promoters that interact with SEs in mouse embryonic stem cells (ESCs). We found that SEs form complex, spatial networks in which individual SEs contact multiple promoters, and a rewiring of promoter-SE interactions occurs between pluripotent states. We also show that long-range promoter-SE interactions are more prevalent in ESCs than in epiblast stem cells (EpiSCs) or Nanog-deficient ESCs. We conclude that SEs form cell-type-specific interaction networks that are partly dependent on core transcription factors, thereby providing insights into the gene regulatory organization of pluripotent cells.

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Cell reports, 22, 2211-1247, 2615-2627, 2018

PMID: 29514091

Thrombopoietin signaling to chromatin elicits rapid and pervasive epigenome remodeling within poised chromatin architectures.
Comoglio F, Park HJ, Schoenfelder S, Barozzi I, Bode D, Fraser P, Green AR

Thrombopoietin (TPO) is a critical cytokine regulating hematopoietic stem cell maintenance and differentiation into the megakaryocytic lineage. However, the transcriptional and chromatin dynamics elicited by TPO signaling are poorly understood. Here, we study the immediate early transcriptional and cis-regulatory responses to TPO in hematopoietic stem/progenitor cells (HSPCs) and use this paradigm of cytokine signaling to chromatin to dissect the relation between cis- regulatory activity and chromatin architecture. We show that TPO profoundly alters the transcriptome of HSPCs, with key hematopoietic regulators being transcriptionally repressed within 30 minutes of TPO. By examining cis-regulatory dynamics and chromatin architectures, we demonstrate that these changes are accompanied by rapid and extensive epigenome remodeling of cis-regulatory landscapes that is spatially coordinated within topologically associating domains (TADs). Moreover, TPO-responsive enhancers are spatially clustered and engage in preferential homotypic intra- and inter-TAD interactions that are largely refractory to TPO signaling. By further examining the link between cis-regulatory dynamics and chromatin looping, we show that rapid modulation of cis-regulatory activity is largely independent of chromatin looping dynamics. Finally, we show that, although activated and repressed cis-regulatory elements share remarkably similar DNA sequence compositions, transcription factor binding patterns accurately predict rapid cis-regulatory responses to TPO.

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Genome research, , 1549-5469, , 2018

PMID: 29429976

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Keywords

3d genome
genome function

Group Members

Latest Publications

Capturing Three-Dimensional Genome Organization in Individual Cells by Single-Cell Hi-C.

Nagano T, Wingett SW, Fraser P

Methods in molecular biology (Clifton, N.J.)
1654 1940-6029:79-97 (2017)

PMID: 28986784

Chromosome contacts in activated T cells identify autoimmune disease candidate genes.

Burren OS, Rubio García A, Javierre BM

Genome biology
18 1474-760X:165 (2017)

PMID: 28870212

Lineage-specific dynamic and pre-established enhancer-promoter contacts cooperate in terminal differentiation.

Rubin AJ, Barajas BC, Furlan-Magaril M

Nature genetics
1546-1718: (2017)

PMID: 28805829

Platelet function is modified by common sequence variation in megakaryocyte super enhancers.

Petersen R, Lambourne JJ, Javierre BM

Nature communications
8 2041-1723:16058 (2017)

PMID: 28703137

Cell-cycle dynamics of chromosomal organization at single-cell resolution.

Nagano T, Lubling Y, Várnai C

Nature
547 1476-4687:61-67 (2017)

PMID: 28682332

Dynamic Rewiring of Promoter-Anchored Chromatin Loops during Adipocyte Differentiation.

Siersbæk R, Madsen JGS, Javierre BM

Molecular cell
66 1097-4164:420-435.e5 (2017)

PMID: 28475875

GOTHiC, a probabilistic model to resolve complex biases and to identify real interactions in Hi-C data.

Mifsud B, Martincorena I, Darbo E

PloS one
12 1932-6203:e0174744 (2017)

PMID: 28379994