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H3K27me3 at pericentromeric heterochromatin is a defining feature of the early mouse blastocyst. Sci Rep 2022; 12:13908. [PMID: 35974030 PMCID: PMC9381757 DOI: 10.1038/s41598-022-17730-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 07/29/2022] [Indexed: 11/09/2022] Open
Abstract
Early mouse development is characterized by structural and epigenetic changes while cells progress towards differentiation. At blastocyst stage, the segregation of the three primordial lineages is accompanied by establishment of differential patterns of DNA methylation and post-translational modifications of histones, such as H3K27me3. Here, we analysed the dynamics of H3K27me3 at pericentromeric heterochromatin (PCH) during early development. We also followed the localization of EZH2 and BEND3, previously shown in ESCs to drive PRC2 to hypomethylated PCH. We show that the location of H3K27me3 at PCH, in addition to H3K9me3, is a defining feature of embryonic cells in vivo. Moreover, it may play an important role in structuring PCH and preserving genomic integrity at a time of globally relaxed chromatin. At peri-implantation stages, while DNA methylation is still low, EZH2 and then H3K27me3, leave PCH in epiblast progenitors at the time of their spatial segregation from primitive endoderm cells, while BEND3 remains there up to implantation. The comparison with stem cells (ESCs and TSCs) reveals that the epigenetic marks (i.e. H3K9me3 and H3K27me3) of PCH are reset during in vitro derivation and only partially restored thereafter. This highlights possible divergences between in vitro and "in embryo" epigenetic regulation regarding constitutive heterochromatin.
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Novo CL, Wong EV, Hockings C, Poudel C, Sheekey E, Wiese M, Okkenhaug H, Boulton SJ, Basu S, Walker S, Kaminski Schierle GS, Narlikar GJ, Rugg-Gunn PJ. Satellite repeat transcripts modulate heterochromatin condensates and safeguard chromosome stability in mouse embryonic stem cells. Nat Commun 2022; 13:3525. [PMID: 35725842 PMCID: PMC9209518 DOI: 10.1038/s41467-022-31198-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 06/07/2022] [Indexed: 12/25/2022] Open
Abstract
Heterochromatin maintains genome integrity and function, and is organised into distinct nuclear domains. Some of these domains are proposed to form by phase separation through the accumulation of HP1ɑ. Mouse heterochromatin contains noncoding major satellite repeats (MSR), which are highly transcribed in mouse embryonic stem cells (ESCs). Here, we report that MSR transcripts can drive the formation of HP1ɑ droplets in vitro, and modulate heterochromatin into dynamic condensates in ESCs, contributing to the formation of large nuclear domains that are characteristic of pluripotent cells. Depleting MSR transcripts causes heterochromatin to transition into a more compact and static state. Unexpectedly, changing heterochromatin's biophysical properties has severe consequences for ESCs, including chromosome instability and mitotic defects. These findings uncover an essential role for MSR transcripts in modulating the organisation and properties of heterochromatin to preserve genome stability. They also provide insights into the processes that could regulate phase separation and the functional consequences of disrupting the properties of heterochromatin condensates.
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Affiliation(s)
- Clara Lopes Novo
- Epigenetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
- Tommy's National Miscarriage Research Centre at Imperial College London, London, W12 0NN, UK.
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
| | - Emily V Wong
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Colin Hockings
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB3 0AS, UK
| | - Chetan Poudel
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB3 0AS, UK
| | - Eleanor Sheekey
- Epigenetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Meike Wiese
- Wellcome - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK
| | - Hanneke Okkenhaug
- Imaging Facility, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Simon J Boulton
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
- Artios Pharma Ltd., B940, Babraham Research Campus, Cambridge, CB22 3FH, UK
| | - Srinjan Basu
- Wellcome - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK
| | - Simon Walker
- Imaging Facility, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | | | - Geeta J Narlikar
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Peter J Rugg-Gunn
- Epigenetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK.
- Wellcome - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, CB2 1QR, UK.
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