1
|
Goto N, Suke K, Yonezawa N, Nishihara H, Handa T, Sato Y, Kujirai T, Kurumizaka H, Yamagata K, Kimura H. ISWI chromatin remodeling complexes recruit NSD2 and H3K36me2 in pericentromeric heterochromatin. J Cell Biol 2024; 223:e202310084. [PMID: 38709169 PMCID: PMC11076809 DOI: 10.1083/jcb.202310084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 03/04/2024] [Accepted: 04/16/2024] [Indexed: 05/07/2024] Open
Abstract
Histone H3 lysine36 dimethylation (H3K36me2) is generally distributed in the gene body and euchromatic intergenic regions. However, we found that H3K36me2 is enriched in pericentromeric heterochromatin in some mouse cell lines. We here revealed the mechanism of heterochromatin targeting of H3K36me2. Among several H3K36 methyltransferases, NSD2 was responsible for inducing heterochromatic H3K36me2. Depletion and overexpression analyses of NSD2-associating proteins revealed that NSD2 recruitment to heterochromatin was mediated through the imitation switch (ISWI) chromatin remodeling complexes, such as BAZ1B-SMARCA5 (WICH), which directly binds to AT-rich DNA via a BAZ1B domain-containing AT-hook-like motifs. The abundance and stoichiometry of NSD2, SMARCA5, and BAZ1B could determine the localization of H3K36me2 in different cell types. In mouse embryos, H3K36me2 heterochromatin localization was observed at the two- to four-cell stages, suggesting its physiological relevance.
Collapse
Affiliation(s)
- Naoki Goto
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Kazuma Suke
- Faculty of Biology-Oriented Science and Technology, Kindai University, Kinokawa, Japan
| | - Nao Yonezawa
- Faculty of Biology-Oriented Science and Technology, Kindai University, Kinokawa, Japan
| | - Hidenori Nishihara
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
- Department of Advanced Bioscience, Graduate School of Agriculture, Kindai University, Nara, Japan
| | - Tetsuya Handa
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Yuko Sato
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Tomoya Kujirai
- Institute for Quantitative Biosciences, The University of Tokyo, Tokyo, Japan
| | - Hitoshi Kurumizaka
- Institute for Quantitative Biosciences, The University of Tokyo, Tokyo, Japan
| | - Kazuo Yamagata
- Faculty of Biology-Oriented Science and Technology, Kindai University, Kinokawa, Japan
| | - Hiroshi Kimura
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| |
Collapse
|
2
|
Halliwell JA, Martin-Gonzalez J, Hashim A, Dahl JA, Hoffmann ER, Lerdrup M. Sex-specific DNA-replication in the early mammalian embryo. Nat Commun 2024; 15:6323. [PMID: 39060312 PMCID: PMC11282264 DOI: 10.1038/s41467-024-50727-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 07/18/2024] [Indexed: 07/28/2024] Open
Abstract
The timing of DNA replication in mammals is crucial for minimizing errors and influenced by genome usage and chromatin states. Replication timing in the newly formed mammalian embryo remains poorly understood. Here, we have investigated replication timing in mouse zygotes and 2-cell embryos, revealing that zygotes lack a conventional replication timing program, which then emerges in 2-cell embryos. This program differs from embryonic stem cells and generally correlates with transcription and genome compartmentalization of both parental genomes. However, consistent and systematic differences existed between the replication timing of the two parental genomes, including considerably later replication of maternal pericentromeric regions compared to paternal counterparts. Moreover, maternal chromatin modified by Polycomb Repressive Complexes in the oocyte, undergoes early replication, despite belonging to the typically late-replicating B-compartment of the genome. This atypical and asynchronous replication of the two parental genomes may advance our understanding of replication stress in early human embryos and trigger strategies to reduce errors and aneuploidies.
Collapse
Affiliation(s)
- Jason Alexander Halliwell
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Javier Martin-Gonzalez
- Core Facility for Transgenic Mice, Department of Experimental Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Adnan Hashim
- Department of Microbiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
- Centre for Embryology and Healthy Development, University of Oslo, Oslo, Norway
| | - John Arne Dahl
- Department of Microbiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
- Centre for Embryology and Healthy Development, University of Oslo, Oslo, Norway
| | - Eva R Hoffmann
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Mads Lerdrup
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
- Centre for Embryology and Healthy Development, University of Oslo, Oslo, Norway.
| |
Collapse
|
3
|
Han X, Xing L, Hong Y, Zhang X, Hao B, Lu JY, Huang M, Wang Z, Ma S, Zhan G, Li T, Hao X, Tao Y, Li G, Zhou S, Zheng Z, Shao W, Zeng Y, Ma D, Zhang W, Xie Z, Deng H, Yan J, Deng W, Shen X. Nuclear RNA homeostasis promotes systems-level coordination of cell fate and senescence. Cell Stem Cell 2024; 31:694-716.e11. [PMID: 38631356 DOI: 10.1016/j.stem.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 02/01/2024] [Accepted: 03/26/2024] [Indexed: 04/19/2024]
Abstract
Understanding cellular coordination remains a challenge despite knowledge of individual pathways. The RNA exosome, targeting a wide range of RNA substrates, is often downregulated in cellular senescence. Utilizing an auxin-inducible system, we observed that RNA exosome depletion in embryonic stem cells significantly affects the transcriptome and proteome, causing pluripotency loss and pre-senescence onset. Mechanistically, exosome depletion triggers acute nuclear RNA aggregation, disrupting nuclear RNA-protein equilibrium. This disturbance limits nuclear protein availability and hinders polymerase initiation and engagement, reducing gene transcription. Concurrently, it promptly disrupts nucleolar transcription, ribosomal processes, and nuclear exporting, resulting in a translational shutdown. Prolonged exosome depletion induces nuclear structural changes resembling senescent cells, including aberrant chromatin compaction, chromocenter disassembly, and intensified heterochromatic foci. These effects suggest that the dynamic turnover of nuclear RNA orchestrates crosstalk between essential processes to optimize cellular function. Disruptions in nuclear RNA homeostasis result in systemic functional decline, altering the cell state and promoting senescence.
Collapse
Affiliation(s)
- Xue Han
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Linqing Xing
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Yantao Hong
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Xuechun Zhang
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Bo Hao
- SXMU-Tsinghua Collaborative Innovation Center for Frontier Medicine, Shanxi Medical University, Taiyuan, Shanxi 030001, China
| | - J Yuyang Lu
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Mengyuan Huang
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Zuhui Wang
- Biomedical Pioneering Innovation Center (BIOPIC), Beijing Advanced Innovation Center for Genomics (ICG), Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Shaoqian Ma
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Ge Zhan
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Tong Li
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaowen Hao
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Yibing Tao
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Guanwen Li
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Shuqin Zhou
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Zheng Zheng
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Wen Shao
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Yitian Zeng
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China
| | - Dacheng Ma
- MOE Key Laboratory of Bioinformatics and Bioinformatics Division, Center for Synthetic and Systems Biology, Department of Automation, Beijing National Research Center for Information Science and Technology, Tsinghua University, Beijing 100084, China
| | - Wenhao Zhang
- MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhen Xie
- MOE Key Laboratory of Bioinformatics and Bioinformatics Division, Center for Synthetic and Systems Biology, Department of Automation, Beijing National Research Center for Information Science and Technology, Tsinghua University, Beijing 100084, China
| | - Haiteng Deng
- MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jiangwei Yan
- SXMU-Tsinghua Collaborative Innovation Center for Frontier Medicine, Shanxi Medical University, Taiyuan, Shanxi 030001, China
| | - Wulan Deng
- Biomedical Pioneering Innovation Center (BIOPIC), Beijing Advanced Innovation Center for Genomics (ICG), Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Xiaohua Shen
- State Key Laboratory of Membrane Biology, Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Basic Medical Sciences, Tsinghua University, Beijing 100084, China; SXMU-Tsinghua Collaborative Innovation Center for Frontier Medicine, Shanxi Medical University, Taiyuan, Shanxi 030001, China.
| |
Collapse
|
4
|
Fu B, Ma H, Liu D. Essential roles of the nucleolus during early embryonic development: a regulatory hub for chromatin organization. Open Biol 2024; 14:230358. [PMID: 38689555 PMCID: PMC11065130 DOI: 10.1098/rsob.230358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/26/2023] [Accepted: 03/15/2024] [Indexed: 05/02/2024] Open
Abstract
The nucleolus is the most prominent liquid droplet-like membrane-less organelle in mammalian cells. Unlike the nucleolus in terminally differentiated somatic cells, those in totipotent cells, such as murine zygotes or two-cell embryos, have a unique nucleolar structure known as nucleolus precursor bodies (NPBs). Previously, it was widely accepted that NPBs in zygotes are simply passive repositories of materials that will be gradually used to construct a fully functional nucleolus after zygotic genome activation (ZGA). However, recent research studies have challenged this simplistic view and demonstrated that functions of the NPBs go beyond ribosome biogenesis. In this review, we provide a snapshot of the functions of NPBs in zygotes and early two-cell embryos in mice. We propose that these membrane-less organelles function as a regulatory hub for chromatin organization. On the one hand, NPBs provide the structural platform for centric and pericentric chromatin remodelling. On the other hand, the dynamic changes in nucleolar structure control the release of the pioneer factors (i.e. double homeobox (Dux)). It appears that during transition from totipotency to pluripotency, decline of totipotency and initiation of fully functional nucleolus formation are not independent events but are interconnected. Consequently, it is reasonable to hypothesize that dissecting more unknown functions of NPBs may shed more light on the enigmas of early embryonic development and may ultimately provide novel approaches to improve reprogramming efficiency.
Collapse
Affiliation(s)
- Bo Fu
- Institute of Animal Husbandry, HeiLongJiang Academy of
Agricultural Sciences, Harbin150086, People's Republic of China
- Key Laboratory of Combining Farming and Animal Husbandry,
Ministry of Agriculture and Rural Affairs, Harbin150086, People's Republic of China
| | - Hong Ma
- Institute of Animal Husbandry, HeiLongJiang Academy of
Agricultural Sciences, Harbin150086, People's Republic of China
- Key Laboratory of Combining Farming and Animal Husbandry,
Ministry of Agriculture and Rural Affairs, Harbin150086, People's Republic of China
| | - Di Liu
- Institute of Animal Husbandry, HeiLongJiang Academy of
Agricultural Sciences, Harbin150086, People's Republic of China
- Key Laboratory of Combining Farming and Animal Husbandry,
Ministry of Agriculture and Rural Affairs, Harbin150086, People's Republic of China
| |
Collapse
|
5
|
Han Q, Ma R, Liu N. Epigenetic reprogramming in the transition from pluripotency to totipotency. J Cell Physiol 2024; 239:e31222. [PMID: 38375873 DOI: 10.1002/jcp.31222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 01/08/2024] [Accepted: 02/05/2024] [Indexed: 02/21/2024]
Abstract
Mammalian development commences with the zygote, which can differentiate into both embryonic and extraembryonic tissues, a capability known as totipotency. Only the zygote and embryos around zygotic genome activation (ZGA) (two-cell embryo stage in mice and eight-cell embryo in humans) are totipotent cells. Epigenetic modifications undergo extremely extensive changes during the acquisition of totipotency and subsequent development of differentiation. However, the underlying molecular mechanisms remain elusive. Recently, the discovery of mouse two-cell embryo-like cells, human eight-cell embryo-like cells, extended pluripotent stem cells and totipotent-like stem cells with extra-embryonic developmental potential has greatly expanded our understanding of totipotency. Experiments with these in vitro models have led to insights into epigenetic changes in the reprogramming of pluri-to-totipotency, which have informed the exploration of preimplantation development. In this review, we highlight the recent findings in understanding the mechanisms of epigenetic remodeling during totipotency capture, including RNA splicing, DNA methylation, chromatin configuration, histone modifications, and nuclear organization.
Collapse
Affiliation(s)
- Qingsheng Han
- School of Medicine, Nankai University, Tianjin, China
| | - Ru Ma
- School of Medicine, Nankai University, Tianjin, China
| | - Na Liu
- School of Medicine, Nankai University, Tianjin, China
| |
Collapse
|
6
|
Ye Y, Homer HA. A surge in cytoplasmic viscosity triggers nuclear remodeling required for Dux silencing and pre-implantation embryo development. Cell Rep 2024; 43:113917. [PMID: 38446665 DOI: 10.1016/j.celrep.2024.113917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 12/17/2023] [Accepted: 02/16/2024] [Indexed: 03/08/2024] Open
Abstract
Embryonic genome activation (EGA) marks the transition from dependence on maternal transcripts to an embryonic transcriptional program. The precise temporal regulation of gene expression, specifically the silencing of the Dux/murine endogenous retrovirus type L (MERVL) program during late 2-cell interphase, is crucial for developmental progression in mouse embryos. How this finely tuned regulation is achieved within this specific window is poorly understood. Here, using particle-tracking microrheology throughout the mouse oocyte-to-embryo transition, we identify a surge in cytoplasmic viscosity specific to late 2-cell interphase brought about by high microtubule and endomembrane density. Importantly, preventing the rise in 2-cell viscosity severely impairs nuclear reorganization, resulting in a persistently open chromatin configuration and failure to silence Dux/MERVL. This, in turn, derails embryo development beyond the 2- and 4-cell stages. Our findings reveal a mechanical role of the cytoplasm in regulating Dux/MERVL repression via nuclear remodeling during a temporally confined period in late 2-cell interphase.
Collapse
Affiliation(s)
- Yunan Ye
- The Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, The University of Queensland, Herston, QLD 4029, Australia
| | - Hayden Anthony Homer
- The Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, The University of Queensland, Herston, QLD 4029, Australia.
| |
Collapse
|
7
|
Kumari A, Vertii A. Perspective: "Current understanding of NADs dynamics and mechanisms of Disease". Gene 2024; 894:147960. [PMID: 37923094 DOI: 10.1016/j.gene.2023.147960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 10/09/2023] [Accepted: 10/31/2023] [Indexed: 11/07/2023]
Abstract
Chromatin architecture is essential for gene regulation, and multiple levels of the 3D chromatin organization exhibit dynamic changes during organismal development and cell differentiation. Heterochromatin, termed compartment B in Hi-C datasets, is a phase-separating gene-silencing form of chromatin, preferentially located at the two nuclear sites, nuclear (lamina-associate chromatin domains, LADs) and nucleoli (nucleoli-associated chromatin domains, NADs) peripheries. LADs and NADs contain both interchangeable and location-specific chromatin domains. Recent studies suggest striking dynamics in LADs and NADs during the differentiation of embryonic stem cells into neural progenitors and neurons. Here we discuss recent advances in understanding NADs changes during neuronal differentiation and future questions on how NADs integrity can contribute to healthy neurodevelopment and neurodevelopment diseases.
Collapse
Affiliation(s)
- Amrita Kumari
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 1605, US
| | - Anastassiia Vertii
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 1605, US.
| |
Collapse
|
8
|
Bogolyubova IO, Sailau ZK, Bogolyubov DS. Nuclear Distribution of the Chromatin-Remodeling Protein ATRX in Mouse Early Embryos during Normal Development and Developmental Arrest In Vitro. Life (Basel) 2023; 14:5. [PMID: 38276254 PMCID: PMC10817635 DOI: 10.3390/life14010005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 12/12/2023] [Accepted: 12/17/2023] [Indexed: 01/27/2024] Open
Abstract
The chromatin-remodeling protein ATRX, which is currently recognized as one of the key genome caretakers, plays an important role in oogenesis and early embryogenesis in mammals. ATRX distribution in the nuclei of mouse embryos developing in vivo and in vitro, including when the embryos are arrested at the two-cell stage-the so-called two-cell block in vitro-was studied using immunofluorescent labeling and FISH. In normally developing two- and four-cell embryos, ATRX was found to be closely colocalized with pericentromeric DNA sequences detected with a probe to the mouse major satellite DNA. The association of ATRX with pericentromeric heterochromatin is mediated by nuclear actin and reduced after the treatment of embryos with latrunculin B. When culturing embryos in vitro, the distribution pattern of ATRX changes, leading to a decrease in the association of this protein with major satellite DNA especially under the two-cell block in vitro. Taken together, our data suggest that the intranuclear distribution of ATRX reflects the viability of mouse embryos and their probability of successful preimplantation development.
Collapse
Affiliation(s)
- Irina O. Bogolyubova
- Institute of Cytology of the Russian Academy of Sciences, St. Petersburg 194064, Russia;
| | - Zhuldyz K. Sailau
- PERSONA International Clinical Center for Reproductology, Almaty 050060, Kazakhstan;
| | - Dmitry S. Bogolyubov
- Institute of Cytology of the Russian Academy of Sciences, St. Petersburg 194064, Russia;
| |
Collapse
|
9
|
Pezic D, Weeks S, Varsally W, Dewari PS, Pollard S, Branco MR, Hadjur S. The N-terminus of Stag1 is required to repress the 2C program by maintaining rRNA expression and nucleolar integrity. Stem Cell Reports 2023; 18:2154-2173. [PMID: 37802073 PMCID: PMC10679541 DOI: 10.1016/j.stemcr.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 09/07/2023] [Accepted: 09/08/2023] [Indexed: 10/08/2023] Open
Abstract
Our understanding of how STAG proteins contribute to cell identity and disease have largely been studied from the perspective of chromosome topology and protein-coding gene expression. Here, we show that STAG1 is the dominant paralog in mouse embryonic stem cells (mESCs) and is required for pluripotency. mESCs express a wide diversity of naturally occurring Stag1 isoforms, resulting in complex regulation of both the levels of STAG paralogs and the proportion of their unique terminal ends. Skewing the balance of these isoforms impacts cell identity. We define a novel role for STAG1, in particular its N-terminus, in regulating repeat expression, nucleolar integrity, and repression of the two-cell (2C) state to maintain mESC identity. Our results move beyond protein-coding gene regulation via chromatin loops to new roles for STAG1 in nucleolar structure and function, and offer fresh perspectives on how STAG proteins, known to be cancer targets, contribute to cell identity and disease.
Collapse
Affiliation(s)
- Dubravka Pezic
- Department of Cancer Biology, Cancer Institute, University College London, 72 Huntley Street, London, UK
| | - Samuel Weeks
- Department of Cancer Biology, Cancer Institute, University College London, 72 Huntley Street, London, UK
| | - Wazeer Varsally
- Department of Cancer Biology, Cancer Institute, University College London, 72 Huntley Street, London, UK
| | - Pooran S Dewari
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, Cancer Research UK Scotland Centre, Edinburgh, UK
| | - Steven Pollard
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, Cancer Research UK Scotland Centre, Edinburgh, UK
| | - Miguel R Branco
- Blizard Institute, Faculty of Medicine and Dentistry, QMUL, London, UK
| | - Suzana Hadjur
- Department of Cancer Biology, Cancer Institute, University College London, 72 Huntley Street, London, UK.
| |
Collapse
|
10
|
Bari MW, Morishita Y, Kishigami S. Heterogeneity of nucleolar morphology in four-cell mouse embryos after IVF: association with developmental potential. Anim Sci J 2023; 94:e13907. [PMID: 38102887 DOI: 10.1111/asj.13907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 11/22/2023] [Accepted: 11/27/2023] [Indexed: 12/17/2023]
Abstract
In mammals, around fertilization, the nucleolus of embryos transforms into the nucleolus precursor bodies (NPBs), which continue to mature until the blastocyst stage, leading to distinct morphological changes. In our study, we observed two types of nucleolar morphology in mouse in vitro fertilized embryos at the four-cell stage, which we refer to single nucleolus (SN) and multiple nucleoli (MN). To visualize nucleolar morphology, four-cell embryos were immunostained with anti-NOPP140 antibody. These embryos were categorized into five types based on the number of blastomeres carrying SN: SN4/MN0, SN3/MN1, SN2/MN2, SN1/MN3, and SN0/MN4, with percentages of 13, 27, 21, 23 and 9, respectively. Next, using a light microscope, we divided the four-cell in vitro fertilized embryos without fixation into two groups: those with at least two blastomeres displaying SN (SN embryos) and those without (MN embryos). Notably, significantly more SN embryos developed into blastocysts and offspring at 18.5 dpc compared with MN embryos. Furthermore, SN embryos displayed a higher NANOG-positive cell number at the blastocyst stage, significantly lower body and placental weights, resulting in a higher fetal/placental ratio. These findings suggest a close association between nucleolar state at the four-cell stage and subsequent developmental potential.
Collapse
Affiliation(s)
- Md Wasim Bari
- Department of Integrated Applied Life Science, Integrated Graduate School of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi, Kofu, Japan
| | - Yoshiya Morishita
- Graduate School of Life and Environmental Sciences, Integrated Graduate School of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi Kofu, Japan
| | - Satoshi Kishigami
- Department of Integrated Applied Life Science, Integrated Graduate School of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi, Kofu, Japan
- Graduate School of Life and Environmental Sciences, Integrated Graduate School of Medicine, Engineering, and Agricultural Sciences, University of Yamanashi Kofu, Japan
- Center for advanced Assisted Reproductive Technologies, University of Yamanashi, Kofu, Japan
| |
Collapse
|
11
|
Ghazimoradi MH, Khalafizadeh A, Babashah S. A critical review on induced totipotent stem cells: Types and methods. Stem Cell Res 2022; 63:102857. [PMID: 35872523 DOI: 10.1016/j.scr.2022.102857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/22/2022] [Accepted: 07/05/2022] [Indexed: 11/25/2022] Open
Abstract
Totipotent stem cells are cells with the capacity to form an entire embryo. Many attempts have been made to convert other types of cells to totipotent stem cells which we called induced totipotent stem cells. Various aspects of these cells such as transcriptional and epigenetics networks are unique. By taking advantage of these aspects, efficient methods have been provided to induce totipotent stem cells. Although this advancement is significant, many aspects of induction such as the underlying mechanism remain to be elucidated. On the other hand, embryonic stem cells usually are the source of induction which raise important questions regarding if these methods are induction or promotion of 2C intrinsic totipotent cells in ESC culture. Here, we review the latest mouse progress in underling mechanism of induction of totipotent stem cells. In addition, we follow up on the progress of Blastoids derived from totipotent stem cells.
Collapse
Affiliation(s)
- Mohammad H Ghazimoradi
- Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Ali Khalafizadeh
- Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Sadegh Babashah
- Department of Molecular Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran.
| |
Collapse
|
12
|
Abstract
Dramatic nuclear reorganization occurs during early development to convert terminally differentiated gametes to a totipotent zygote, which then gives rise to an embryo. Aberrant epigenome resetting severely impairs embryo development and even leads to lethality. How the epigenomes are inherited, reprogrammed, and reestablished in this critical developmental period has gradually been unveiled through the rapid development of technologies including ultrasensitive chromatin analysis methods. In this review, we summarize the latest findings on epigenetic reprogramming in gametogenesis and embryogenesis, and how it contributes to gamete maturation and parental-to-zygotic transition. Finally, we highlight the key questions that remain to be answered to fully understand chromatin regulation and nuclear reprogramming in early development.
Collapse
Affiliation(s)
- Zhenhai Du
- Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| | - Ke Zhang
- Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| | - Wei Xie
- Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, Tsinghua University, Beijing 100084, China
- Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| |
Collapse
|
13
|
Nuclear Lamins: Key Proteins for Embryonic Development. BIOLOGY 2022; 11:biology11020198. [PMID: 35205065 PMCID: PMC8869099 DOI: 10.3390/biology11020198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/21/2022] [Accepted: 01/24/2022] [Indexed: 11/28/2022]
Abstract
Simple Summary The biology of a multicellular organism is extremely complex, leaving behind a realm of compound yet systematic mechanisms still to be unraveled. The nucleus is a vital cellular organelle adapted to storing and regulating the hereditary genetic information. Dysregulation of the nucleus can have profound effects on the physiology and viability of cells. This becomes extremely significant in the context of development, where the whole organism arises from a single cell, the zygote. Therefore, even a mild aberration at this stage can have profound effects on the whole organism. However, studying the function of individual nuclear components at this point is exceptionally complicated because this phase is inherently under the control of maternal factors stored in the female germ cell, the egg. Here, we focus on the lamins, as essential nuclear components, and summarize the current knowledge of their role in development. Although scientists encounter challenges working with these miniscule yet key proteins, the demand to know more is increasing gradually due to the mutations caused in lamins leading to irreversible phenotypic conditions in humans. Abstract Lamins are essential components of the nuclear envelope and have been studied for decades due to their involvement in several devastating human diseases, the laminopathies. Despite intensive research, the molecular basis behind the disease state remains mostly unclear with a number of conflicting results regarding the different cellular functions of nuclear lamins being published. The field of developmental biology is no exception. Across model organisms, the types of lamins present in early mammalian development have been contradictory over the years. Due to the long half-life of the lamin proteins, which is a maternal factor that gets carried over to the zygote after fertilization, investigators are posed with challenges to dive into the functional aspects and significance of lamins in development. Due to these technical limitations, the role of lamins in early mammalian embryos is virtually unexplored. This review aims in converging results that were obtained so far in addition to the complex functions that ceases if lamins are mutated.
Collapse
|
14
|
Chebrout M, Koné MC, Jan HU, Cournut M, Letheule M, Fleurot R, Aguirre-Lavin T, Peynot N, Jouneau A, Beaujean N, Bonnet-Garnier A. Transcription of rRNA in early mouse embryos promotes chromatin reorganization and expression of major satellite repeats. J Cell Sci 2022; 135:274059. [DOI: 10.1242/jcs.258798] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 01/09/2022] [Indexed: 11/20/2022] Open
Abstract
During the first cell cycles of the early development, the chromatin of the embryo is highly reprogrammed alongside that embryonic genome starts its own transcription. The spatial organization of the genome is a major process that contributes to regulating gene transcription in time and space, however, it is poorly studied in the context of early embryos. To study the cause and effect link between transcription and spatial organization in embryos, we focused on the ribosomal genes, that are first silent and begin to transcribe during the 2-cell stage in the mouse. We demonstrated that ribosomal sequences and early unprocessed rRNAs are spatially organized in a very peculiar manner from the 2-cell to the 16-cell. Using drugs interfering with ribosomal DNA transcription, we show that this organization, totally different from somatic cells, depends on an active transcription of ribosomal genes and induces a unique chromatin environment that favors transcription of major satellite sequences after the 4-cell stage.
Collapse
Affiliation(s)
- Martine Chebrout
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Maïmouna Coura Koné
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Habib U. Jan
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Marie Cournut
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Martine Letheule
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Renaud Fleurot
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Tiphaine Aguirre-Lavin
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Nathalie Peynot
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Alice Jouneau
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Nathalie Beaujean
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| | - Amélie Bonnet-Garnier
- Université Paris-Saclay, UVSQ, INRAE, BREED, 78350, Jouy-en-Josas, France
- Ecole Nationale Vétérinaire d'Alfort, BREED, 94700, Maisons-Alfort, France
| |
Collapse
|
15
|
FULKA H, LOI P, PALAZZESE L, BENC M, FULKA, Jr. J. Nucleus reprogramming/remodeling through selective enucleation (SE) of immature oocytes and zygotes: a nucleolus point of view. J Reprod Dev 2022; 68:165-172. [PMID: 35431279 PMCID: PMC9184824 DOI: 10.1262/jrd.2022-004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is now approximately 25 years since the sheep Dolly, the first cloned mammal where the somatic cell nucleus from an adult donor was used for transfer, was born. So far, somatic cell
nucleus transfer, where G1-phase nuclei are transferred into cytoplasts obtained by enucleation of mature metaphase II (MII) oocytes followed by the activation of the reconstructed cells, is
the most efficient approach to reprogram/remodel the differentiated nucleus. In general, in an enucleated oocyte (cytoplast), the nuclear envelope (NE, membrane) of an injected somatic cell
nucleus breaks down and chromosomes condense. This condensation phase is followed, after subsequent activation, by chromatin decondensation and formation of a pseudo-pronucleus (i) whose
morphology should resemble the natural postfertilization pronuclei (PNs). Thus, the volume of the transferred nuclei increases considerably by incorporating the content released from the
germinal vesicles (GVs). In parallel, the transferred nucleus genes must be reset and function similarly as the relevant genes in normal embryo reprogramming. This, among others, covers the
relevant epigenetic modifications and the appropriate organization of chromatin in pseudo-pronuclei. While reprogramming in SCNT is often discussed, the remodeling of transferred nuclei is
much less studied, particularly in the context of the developmental potential of SCNT embryos. It is now evident that correct reprogramming mirrors appropriate remodeling. At the same time,
it is widely accepted that the process of rebuilding the nucleus following SCNT is instrumental to the overall success of this procedure. Thus, in our contribution, we will mostly focus on
the remodeling of transferred nuclei. In particular, we discuss the oocyte organelles that are essential for the development of SCNT embryos.
Collapse
Affiliation(s)
- Helena FULKA
- Institute of Experimental Medicine, Prague, Czech Republic
| | - Pasqualino LOI
- Faculty of Veterinary Medicine, University of Teramo, Teramo, Italy
| | - Luca PALAZZESE
- Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, 05-552 Jastrzebiec, Poland
| | - Michal BENC
- Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Slovak Republic
| | | |
Collapse
|
16
|
Li Y, Tang J, Ji X, Hua MM, Liu M, Chang L, Gu Y, Shi C, Ni W, Liu J, Shi HJ, Huang X, O'Neill C, Jin X. Regulation of the mammalian maternal-to-embryonic transition by eukaryotic translation initiation factor 4E. Development 2021; 148:268308. [PMID: 34013332 PMCID: PMC8254863 DOI: 10.1242/dev.190793] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Accepted: 05/12/2021] [Indexed: 12/24/2022]
Abstract
Eukaryotic translation initiation factor 4E (eIF4E) mediates cap-dependent translation. Genetic and inhibitor studies show that eIF4E expression is required for the successful transition from maternal to embryonic control of mouse embryo development. eIF4E was present in the oocyte and in the cytoplasm soon after fertilization and during each stage of early development. Functional knockout (Eif4e−/−) by PiggyBac [Act-RFP] transposition resulted in peri-implantation embryonic lethality because of the failure of normal epiblast formation. Maternal stores of eIF4E supported development up to the two- to four-cell stage, after which new expression occurred from both maternal and paternal inherited alleles. Inhibition of the maternally acquired stores of eIF4E (using the inhibitor 4EGI-1) resulted in a block at the two-cell stage. eIF4E activity was required for new protein synthesis in the two-cell embryo and Eif4e−/− embryos had lower translational activity compared with wild-type embryos. eIF4E-binding protein 1 (4E-BP1) is a hypophosphorylation-dependent negative regulator of eIF4E. mTOR activity was required for 4E-BP1 phosphorylation and inhibiting mTOR retarded embryo development. Thus, this study shows that eIF4E activity is regulated at key embryonic transitions in the mammalian embryo and is essential for the successful transition from maternal to embryonic control of development. Summary: Combined use of a PB [Act-RFP] transgenesis model, selective pharmacological inhibition and expression analyses verified the essential role of eIF4E in the transition from maternal to embryonic control of mouse development.
Collapse
Affiliation(s)
- Yan Li
- Reproductive Medicine Center, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, China
| | - Jianan Tang
- NHC Key Lab of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, 200032, China
| | - Xu Ji
- Department of Pharmacology, School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, Jiangsu Province, 211816, China
| | - Min-Min Hua
- NHC Key Lab of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, 200032, China
| | - Miao Liu
- Reproductive Medical Center, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Lu Chang
- Department of Pharmacology, School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, Jiangsu Province, 211816, China
| | - Yihua Gu
- NHC Key Lab of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, 200032, China
| | - Changgen Shi
- NHC Key Lab of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, 200032, China
| | - Wuhua Ni
- Reproductive Medicine Center, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, China
| | - Jing Liu
- Department of Pharmacology, School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, Jiangsu Province, 211816, China
| | - Hui-Juan Shi
- NHC Key Lab of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, 200032, China
| | - Xuefeng Huang
- Reproductive Medicine Center, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, China
| | - Christopher O'Neill
- Human Reproduction Unit, Sydney Center for Regenerative and Developmental Medicine, Kolling Institute for Medical Research, Sydney Medical School, University of Sydney, St. Leonards, New South Wales, 2065, Australia
| | - Xingliang Jin
- Reproductive Medicine Center, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, China.,Human Reproduction Unit, Sydney Center for Regenerative and Developmental Medicine, Kolling Institute for Medical Research, Sydney Medical School, University of Sydney, St. Leonards, New South Wales, 2065, Australia
| |
Collapse
|
17
|
Payne AC, Chiang ZD, Reginato PL, Mangiameli SM, Murray EM, Yao CC, Markoulaki S, Earl AS, Labade AS, Jaenisch R, Church GM, Boyden ES, Buenrostro JD, Chen F. In situ genome sequencing resolves DNA sequence and structure in intact biological samples. Science 2021; 371:eaay3446. [PMID: 33384301 PMCID: PMC7962746 DOI: 10.1126/science.aay3446] [Citation(s) in RCA: 113] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 08/17/2020] [Accepted: 12/14/2020] [Indexed: 12/11/2022]
Abstract
Understanding genome organization requires integration of DNA sequence and three-dimensional spatial context; however, existing genome-wide methods lack either base pair sequence resolution or direct spatial localization. Here, we describe in situ genome sequencing (IGS), a method for simultaneously sequencing and imaging genomes within intact biological samples. We applied IGS to human fibroblasts and early mouse embryos, spatially localizing thousands of genomic loci in individual nuclei. Using these data, we characterized parent-specific changes in genome structure across embryonic stages, revealed single-cell chromatin domains in zygotes, and uncovered epigenetic memory of global chromosome positioning within individual embryos. These results demonstrate how IGS can directly connect sequence and structure across length scales from single base pairs to whole organisms.
Collapse
Affiliation(s)
- Andrew C Payne
- Media Arts and Sciences, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA
| | - Zachary D Chiang
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Paul L Reginato
- Media Arts and Sciences, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA
- Department of Biological Engineering, MIT, Cambridge, MA, 02139, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
| | | | - Evan M Murray
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA
| | - Chun-Chen Yao
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA
- Department of Brain and Cognitive Sciences, MIT, Cambridge, MA 02139, USA
| | | | - Andrew S Earl
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Ajay S Labade
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Rudolf Jaenisch
- Whitehead Institute for Biomedical Research, Cambridge, MA 02139, USA
- Department of Biology, MIT, Cambridge, MA 02139, USA
| | - George M Church
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
| | - Edward S Boyden
- Media Arts and Sciences, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.
- Department of Biological Engineering, MIT, Cambridge, MA, 02139, USA
- Department of Brain and Cognitive Sciences, MIT, Cambridge, MA 02139, USA
- McGovern Institute, MIT, Cambridge, MA 02139, USA
- Koch Institute, MIT, Cambridge, MA 02139, USA
- Howard Hughes Medical Institute, Cambridge, MA 02139, USA
- Centers for Neurobiological Engineering and Extreme Bionics, MIT, Cambridge, MA 02139, USA
| | - Jason D Buenrostro
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA.
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Fei Chen
- Broad Institute of MIT and Harvard University, Cambridge, MA 02142, USA.
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| |
Collapse
|
18
|
The nucleolus-like and precursor bodies of mammalian oocytes and embryos and their possible role in post-fertilization centromere remodelling. Biochem Soc Trans 2021; 48:581-593. [PMID: 32318710 DOI: 10.1042/bst20190847] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 03/27/2020] [Accepted: 03/30/2020] [Indexed: 12/14/2022]
Abstract
In nearly all somatic cells, the ribosome biosynthesis is a key activity. The same is true also for mammalian oocytes and early embryos. This activity is intimately linked to the most prominent nuclear organelles - the nucleoli. Interestingly, during a short period around fertilization, the nucleoli in oocytes and embryos transform into ribosome-biosynthesis-inactive structures termed nucleolus-like or nucleolus precursor bodies (NPBs). For decades, researchers considered these structures to be passive repositories of nucleolar proteins used by the developing embryo to rebuild fully functional, ribosome-synthesis competent nucleoli when required. Recent evidence, however, indicates that while these structures are unquestionably essential for development, the material is largely dispensable for the formation of active embryonic nucleoli. In this mini-review, we will describe some unique features of oocytes and embryos with respect to ribosome biogenesis and the changes in the structure of oocyte and embryonic nucleoli that reflect this. We will also describe some of the different approaches that can be used to study nucleoli and NPBs in embryos and discuss the different results that might be expected. Finally, we ask whether the main function of nucleolar precursor bodies might lie in the genome organization and remodelling and what the involved components might be.
Collapse
|
19
|
Bogolyubova I, Bogolyubov D. DAXX Is a Crucial Factor for Proper Development of Mammalian Oocytes and Early Embryos. Int J Mol Sci 2021; 22:ijms22031313. [PMID: 33525665 PMCID: PMC7866053 DOI: 10.3390/ijms22031313] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/22/2021] [Accepted: 01/26/2021] [Indexed: 12/18/2022] Open
Abstract
The Death-domain associated protein 6 (DAXX) is an evolutionarily conserved and ubiquitously expressed multifunctional protein that is implicated in many cellular processes, including transcription, cellular proliferation, cell cycle regulation, Fas-induced apoptosis, and many other events. In the nucleus, DAXX interacts with transcription factors, epigenetic modifiers, and chromatin-remodeling proteins such as the transcription regulator ATRX-the α-thalassemia/mental retardation syndrome X-linked ATP-dependent helicase II. Accordingly, DAXX is considered one of the main players involved in chromatin silencing and one of the most important factors that maintain integrity of the genome. In this brief review, we summarize available data regarding the general and specific functions of DAXX in mammalian early development, with special emphasis on the function of DAXX as a chaperone of the histone variant H3.3. Since H3.3 plays a key role in the developmental processes, especially in the pronounced rearrangements of heterochromatin compartment during oogenesis and embryogenesis, DAXX can be considered as an important factor supporting proper development. Specifically, loss of DAXX affects the recruitment of ATRX, transcription of tandem repeats and telomere functions, which results in a decrease in the viability of early embryos.
Collapse
|
20
|
Ancelin K, Miyanari Y, Leroy O, Torres-Padilla ME, Heard E. Mapping of Chromosome Territories by 3D-Chromosome Painting During Early Mouse Development. Methods Mol Biol 2021; 2214:175-187. [PMID: 32944910 DOI: 10.1007/978-1-0716-0958-3_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Following fertilization in mammals, the chromatin landscape inherited from the two parental genomes and the nuclear organization are extensively reprogrammed. A tight regulation of nuclear organization is important for developmental success. One main nuclear feature is the organization of the chromosomes in discrete and individual nuclear spaces known as chromosome territories (CTs). In culture cells, their arrangements can be constrained depending on their genomic content (e.g., gene density or repeats) or by specific nuclear constrains such as the periphery or the nucleolus. However, during the early steps of mouse embryonic development, much less is known, specifically regarding how and when the two parental genomes intermingle. Here, we describe a three-dimensional fluorescence in situ hybridization (3D-FISH) for chromosome painting (3D-ChromoPaint) optimized to gain understanding in nuclear organization of specific CTs following fertilization. Our approach preserves the nuclear structure, and the acquired images allow full spatial analysis of interphase chromosome positioning and morphology across the cell cycle and during early development. This method will be useful in understanding the dynamics of chromosome repositioning during development as well as the alteration of chromosome territories upon changes in transcriptional status during key developmental steps. This protocol can be adapted to any other species or organoids in culture.
Collapse
Affiliation(s)
- Katia Ancelin
- Institut Curie, CNRS UMR3215/ INSERM U934, Paris Sciences & Lettres Research University (PSL), Paris, France.
| | - Yusuke Miyanari
- Division of Nuclear Dynamics, Exploratory Research Center on Life and Living Systems: ExCELLS National Institute for Basic Biology, Okazaki, Japan
| | - Olivier Leroy
- Institut Curie, CNRS UMR3215/ INSERM U934, Paris Sciences & Lettres Research University (PSL), Paris, France
| | | | - Edith Heard
- Institut Curie, CNRS UMR3215/ INSERM U934, Paris Sciences & Lettres Research University (PSL), Paris, France.,EMBL, Heidelberg, Germany
| |
Collapse
|
21
|
Genet M, Torres-Padilla ME. The molecular and cellular features of 2-cell-like cells: a reference guide. Development 2020; 147:147/16/dev189688. [PMID: 32847823 DOI: 10.1242/dev.189688] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Currently, two main cell culture models predominate pluripotent stem cell research: embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Thanks to their ability to contribute to and form all tissues within the body, ESCs and iPSCs have proven invaluable in understanding pluripotent states, early embryonic development and cell differentiation, as well as in devising strategies for regenerative medicine. Comparatively little is known about totipotency - a cellular state with greater developmental potential. In mice, only the zygote and the blastomeres of the 2-cell-stage embryo are truly totipotent, as they alone can develop to form the embryo and all of its supportive extra-embryonic tissues. However, the discovery of a rare subpopulation of cells in murine ESC cultures, possessing features of 2-cell embryo blastomeres and expanded cell fate potential, has provided a biochemically tractable model to enable the in vitro study of totipotency. Here, we summarize current known features of these 2-cell-like cells (2CLCs) in an effort to provide a reference for the community, and to clarify what we know about their identity so far.
Collapse
Affiliation(s)
- Marion Genet
- Institute of Epigenetics and Stem Cells (IES), Helmholtz Zentrum München, D-81377, Germany
| | - Maria-Elena Torres-Padilla
- Institute of Epigenetics and Stem Cells (IES), Helmholtz Zentrum München, D-81377, Germany .,Faculty of Biology, Ludwig-Maximilians Universität, 82152 Martinsried, Germany
| |
Collapse
|
22
|
Bogolyubova I, Bogolyubov D. Heterochromatin Morphodynamics in Late Oogenesis and Early Embryogenesis of Mammals. Cells 2020; 9:cells9061497. [PMID: 32575486 PMCID: PMC7348780 DOI: 10.3390/cells9061497] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 06/10/2020] [Accepted: 06/16/2020] [Indexed: 12/15/2022] Open
Abstract
During the period of oocyte growth, chromatin undergoes global rearrangements at both morphological and molecular levels. An intriguing feature of oogenesis in some mammalian species is the formation of a heterochromatin ring-shaped structure, called the karyosphere or surrounded "nucleolus", which is associated with the periphery of the nucleolus-like bodies (NLBs). Morphologically similar heterochromatin structures also form around the nucleolus-precursor bodies (NPBs) in zygotes and persist for several first cleavage divisions in blastomeres. Despite recent progress in our understanding the regulation of gene silencing/expression during early mammalian development, as well as the molecular mechanisms that underlie chromatin condensation and heterochromatin structure, the biological significance of the karyosphere and its counterparts in early embryos is still elusive. We pay attention to both the changes of heterochromatin morphology and to the molecular mechanisms that can affect the configuration and functional activity of chromatin. We briefly discuss how DNA methylation, post-translational histone modifications, alternative histone variants, and some chromatin-associated non-histone proteins may be involved in the formation of peculiar heterochromatin structures intimately associated with NLBs and NPBs, the unique nuclear bodies of oocytes and early embryos.
Collapse
|
23
|
White MD, Plachta N. Specification of the First Mammalian Cell Lineages In Vivo and In Vitro. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035634. [PMID: 31615786 DOI: 10.1101/cshperspect.a035634] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Our understanding of how the first mammalian cell lineages arise has been shaped largely by studies of the preimplantation mouse embryo. Painstaking work over many decades has begun to reveal how a single totipotent cell is transformed into a multilayered structure representing the foundations of the body plan. Here, we review how the first lineage decision is initiated by epigenetic regulation but consolidated by the integration of morphological features and transcription factor activity. The establishment of pluripotent and multipotent stem cell lines has enabled deeper analysis of molecular and epigenetic regulation of cell fate decisions. The capability to assemble these stem cells into artificial embryos is an exciting new avenue of research that offers a long-awaited window into cell fate specification in the human embryo. Together, these approaches are poised to profoundly increase our understanding of how the first lineage decisions are made during mammalian embryonic development.
Collapse
Affiliation(s)
- Melanie D White
- Institute of Molecular and Cell Biology, A*STAR, Singapore 138673
| | - Nicolas Plachta
- Institute of Molecular and Cell Biology, A*STAR, Singapore 138673
| |
Collapse
|
24
|
Saini AK, Saini R, Bansode H, Singh A, Singh L. Stem Cells: A Review Encompassing the Literature with a Special Focus on the Side-Lined Miraculous Panacea; Pre-Morula Stem Cells. Curr Stem Cell Res Ther 2020; 15:379-387. [PMID: 32160851 DOI: 10.2174/1574888x15666200311141731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 02/03/2020] [Accepted: 02/12/2020] [Indexed: 11/22/2022]
Abstract
Stem cells are the undifferentiated cells in the body that possess the ability to differentiate and give rise to any type of cells in the body. In recent years, there has been a growing interest in therapies involving stem cells as different treatment methods got developed. Depending on the source, there are two major kinds of stem cells, embryonic and adult stem cells. The former type is found in the embryo at the different developmental stages before the implantation and excels the latter owing to pluripotency. On the premise of the attributes of stem cells, they are touted as the "panacea for all ills" and are extensively sought for their potential therapeutic roles. There are a lot of robust pieces of evidence that have proved to cure the different ailments in the body like Huntington disease, Parkinson's disease, and Spinal cord injury with stem cell therapy but associated with adverse effects like immune rejection and teratoma formation. In this regard, the pre-morula (isolated at an early pre-morula stage) stem cells (PMSCs) are one of its kind of embryonic stem cells that are devoid of the aforementioned adverse effects. Taking the beneficial factor into account, they are being used for the treatment of disorders like Cerebral palsy, Parkinson's disorder, Aplastic anemia, Multiple sclerosis and many more. However, it is still illegal to use stem cells in the abovementioned disorders. This review encompasses different stem cells and emphasizes on PMSCs for their uniqueness in therapy as no other previously published literature reviews have taken these into consideration. Later in the review, current regulatory aspects related to stem cells are also considered.
Collapse
Affiliation(s)
- Aryendu K Saini
- Department of Pharmacy, Pranveer Singh Institute of Technology, Kanpur, U.P., India
| | - Rakesh Saini
- Department of Pharmacy, Chaudhary Sughar Singh College of Pharmacy, Etawah, U.P., India
| | - Himanshu Bansode
- Department of Pharmacy, Pranveer Singh Institute of Technology, Kanpur, U.P., India
| | - Anurag Singh
- Department of Pharmacy, Pranveer Singh Institute of Technology, Kanpur, U.P., India
| | - Lalita Singh
- Department of Pharmacy, Pranveer Singh Institute of Technology, Kanpur, U.P., India
| |
Collapse
|
25
|
Kresoja-Rakic J, Santoro R. Nucleolus and rRNA Gene Chromatin in Early Embryo Development. Trends Genet 2019; 35:868-879. [PMID: 31327501 DOI: 10.1016/j.tig.2019.06.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/17/2019] [Accepted: 06/24/2019] [Indexed: 12/16/2022]
Abstract
The nucleolus is the largest substructure in the nucleus and forms around the nucleolar organizer regions (NORs), which comprise hundreds of rRNA genes. Recent evidence highlights further functions of the nucleolus that go beyond ribosome biogenesis. Data indicate that the nucleolus acts as a compartment for the location and regulation of repressive genomic domains and, together with the nuclear lamina, represents the hub for the organization of the inactive heterochromatin. In this review, we discuss recent findings that have revealed how nucleolar structure and rRNA gene chromatin states are regulated during early mammalian development and their contribution to the higher-order spatial organization of the genome.
Collapse
Affiliation(s)
- Jelena Kresoja-Rakic
- Department of Molecular Mechanisms of Disease, DMMD, University of Zurich, CH-8057 Zurich, Switzerland
| | - Raffaella Santoro
- Department of Molecular Mechanisms of Disease, DMMD, University of Zurich, CH-8057 Zurich, Switzerland.
| |
Collapse
|
26
|
Vertii A, Ou J, Yu J, Yan A, Pagès H, Liu H, Zhu LJ, Kaufman PD. Two contrasting classes of nucleolus-associated domains in mouse fibroblast heterochromatin. Genome Res 2019; 29:1235-1249. [PMID: 31201210 PMCID: PMC6673712 DOI: 10.1101/gr.247072.118] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 06/10/2019] [Indexed: 01/15/2023]
Abstract
In interphase eukaryotic cells, almost all heterochromatin is located adjacent to the nucleolus or to the nuclear lamina, thus defining nucleolus-associated domains (NADs) and lamina-associated domains (LADs), respectively. Here, we determined the first genome-scale map of murine NADs in mouse embryonic fibroblasts (MEFs) via deep sequencing of chromatin associated with purified nucleoli. We developed a Bioconductor package called NADfinder and demonstrated that it identifies NADs more accurately than other peak-calling tools, owing to its critical feature of chromosome-level local baseline correction. We detected two distinct classes of NADs. Type I NADs associate frequently with both the nucleolar periphery and the nuclear lamina, and generally display characteristics of constitutive heterochromatin, including late DNA replication, enrichment of H3K9me3, and little gene expression. In contrast, Type II NADs associate with nucleoli but do not overlap with LADs. Type II NADs tend to replicate earlier, display greater gene expression, and are more often enriched in H3K27me3 than Type I NADs. The nucleolar associations of both classes of NADs were confirmed via DNA-FISH, which also detected Type I but not Type II probes enriched at the nuclear lamina. Type II NADs are enriched in distinct gene classes, including factors important for differentiation and development. In keeping with this, we observed that a Type II NAD is developmentally regulated, and present in MEFs but not in undifferentiated embryonic stem (ES) cells.
Collapse
Affiliation(s)
- Anastassiia Vertii
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Jianhong Ou
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Jun Yu
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Aimin Yan
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Hervé Pagès
- Program in Computational Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA
| | - Haibo Liu
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Lihua Julie Zhu
- Department of Molecular, Cellular and Cancer Biology, Program in Bioinformatics and Integrative Biology, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Paul D Kaufman
- Department of Molecular, Cellular and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| |
Collapse
|
27
|
Yandım C, Karakülah G. Expression dynamics of repetitive DNA in early human embryonic development. BMC Genomics 2019; 20:439. [PMID: 31151386 PMCID: PMC6545021 DOI: 10.1186/s12864-019-5803-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 05/15/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The last decade witnessed a number of genome-wide studies on human pre-implantation, which mostly focused on genes and provided only limited information on repeats, excluding the satellites. Considering the fact that repeats constitute a large portion of our genome with reported links to human physiology and disease, a thorough understanding of their spatiotemporal regulation during human embryogenesis will give invaluable clues on chromatin dynamics across time and space. Therefore, we performed a detailed expression analysis of all repetitive DNA elements including the satellites across stages of human pre-implantation and embryonic stem cells. RESULTS We uncovered stage-specific expressions of more than a thousand repeat elements whose expressions fluctuated with a mild global decrease at the blastocyst stage. Most satellites were highly expressed at the 4-cell level and expressions of ACRO1 and D20S16 specifically peaked at this point. Whereas all members of the SVA elements were highly upregulated at 8-cell and morula stages, other transposons and small RNA repeats exhibited a high level of variation among their specific subtypes. Our repeat enrichment analysis in gene promoters coupled with expression correlations highlighted potential links between repeat expressions and nearby genes, emphasising mostly 8-cell and morula specific genes together with SVA_D, LTR5_Hs and LTR70 transposons. The DNA methylation analysis further complemented the understanding on the mechanistic aspects of the repeatome's regulation per se and revealed critical stages where DNA methylation levels are negatively correlating with repeat expression. CONCLUSIONS Taken together, our study shows that specific expression patterns are not exclusive to genes and long non-coding RNAs but the repeatome also exhibits an intriguingly dynamic pattern at the global scale. Repeats identified in this study; particularly satellites, which were historically associated with heterochromatin, and those with potential links to nearby gene expression provide valuable insights into the understanding of key events in genomic regulation and warrant further research in epigenetics, genomics and developmental biology.
Collapse
Affiliation(s)
- Cihangir Yandım
- İzmir Biomedicine and Genome Center (IBG), 35340, İnciraltı, İzmir, Turkey.,Department of Genetics and Bioengineering, İzmir University of Economics, Faculty of Engineering, 35330, Balçova, İzmir, Turkey.,Department of Medicine, Division of Brain Sciences, Hammersmith Hospital, Imperial College London, Faculty of Medicine, W12 0NN, London, UK
| | - Gökhan Karakülah
- İzmir Biomedicine and Genome Center (IBG), 35340, İnciraltı, İzmir, Turkey. .,İzmir International Biomedicine and Genome Institute (iBG-İzmir), Dokuz Eylül University, 35340, İnciraltı, İzmir, Turkey.
| |
Collapse
|
28
|
The Oocyte’s Nucleolus Precursor Body: The Globe for Life. MACEDONIAN VETERINARY REVIEW 2018. [DOI: 10.2478/macvetrev-2018-0013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
The nucleolus is the cell organelle responsible for ribosome synthesis and, hence, for protein synthesis. In the mammalian oocyte, the nucleolus compacts into a dense sphere with no ribosome synthesis well in advance of ovulation. It seems, that this body is of utmost importance for the development of the embryo. It is unknown, however, how it exerts this essential function. During the last two decades, great attention has been paid to the study of nucleogenesis in oocytes and early embryos, with transcription of ribosomal DNA being evaluated as one of the criteria of normal development. In this review, we summarize some aspects of nucleolus transformation during oocyte growth, as well as during early embryonic development with possible impact on the quality of the embryos used in biomedical research. This knowledge in connection with further observations will substantially contribute to the development of new criteria suitable for evaluation of oocytes and embryos used in biomedical application.
Collapse
|
29
|
Kyogoku H, Wakayama T, Kitajima TS, Miyano T. Single nucleolus precursor body formation in the pronucleus of mouse zygotes and SCNT embryos. PLoS One 2018; 13:e0202663. [PMID: 30125305 PMCID: PMC6101414 DOI: 10.1371/journal.pone.0202663] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/07/2018] [Indexed: 11/18/2022] Open
Abstract
Mammalian oocytes and zygotes have nucleoli that are transcriptionally inactive and structurally distinct from nucleoli in somatic cells. These nucleoli have been termed nucleolus precursor bodies (NPBs). Recent research has shown that NPBs are important for embryonic development, but they are only required during pronuclear formation. After fertilization, multiple small NPBs are transiently formed in male and female pronuclei and then fuse into a single large NPB in zygotes. In cloned embryos produced by somatic cell nuclear transfer (SCNT), multiple NPBs are formed and maintained in the pseudo-pronucleus, and this is considered an abnormality of the cloned embryos. Despite this difference between SCNT and normal embryos, it is unclear how the size and number of NPBs in pronuclei is determined. Here, we show that in mouse embryos, the volume of NPB materials plays a major role in the NPB scaling through a limiting component mechanism and determines whether a single or multiple NPBs will form in the pronucleus. Extra NPB- and extra MII spindle-injection experiments demonstrated that the total volume of NPBs was maintained regardless of the pronucleus number and the ratio of pronucleus/NPB is important for fusion into a single NPB. Based on these results, we examined whether extra-NPB injection rescued multiple NPB maintenance in SCNT embryos. When extra-NPBs were injected into enucleated-MII oocytes before SCNT, the number of NPBs in pseudo-pronuclei of SCNT embryos was reduced. These results indicate that multiple NPB maintenance in SCNT embryos is caused by insufficient volume of NPB.
Collapse
Affiliation(s)
- Hirohisa Kyogoku
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
- Laboratory for Chromosome Segregation, Center for Developmental Biology, RIKEN, Kobe, Japan
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
- * E-mail:
| | - Teruhiko Wakayama
- Faculty of Life and Environmental Sciences, University of Yamanashi, Kofu, Japan
| | - Tomoya S. Kitajima
- Laboratory for Chromosome Segregation, Center for Developmental Biology, RIKEN, Kobe, Japan
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Takashi Miyano
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
| |
Collapse
|
30
|
Pichugin A, Iarovaia OV, Gavrilov A, Sklyar I, Barinova N, Barinov A, Ivashkin E, Caron G, Aoufouchi S, Razin SV, Fest T, Lipinski M, Vassetzky YS. The IGH locus relocalizes to a "recombination compartment" in the perinucleolar region of differentiating B-lymphocytes. Oncotarget 2018; 8:40079-40089. [PMID: 28445143 PMCID: PMC5522243 DOI: 10.18632/oncotarget.16941] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 03/29/2017] [Indexed: 12/22/2022] Open
Abstract
The immunoglobulin heavy chain (IGH) gene loci are subject to specific recombination events during B-cell differentiation including somatic hypermutation and class switch recombination which mark the end of immunoglobulin gene maturation in germinal centers of secondary lymph nodes. These two events rely on the activity of activation-induced cytidine deaminase (AID) which requires DNA double strand breaks be created, a potential danger to the cell. Applying 3D-fluorescence in situ hybridization coupled with immunofluorescence staining to a previously described experimental system recapitulating normal B-cell differentiation ex vivo, we have kinetically analyzed the radial positioning of the two IGH gene loci as well as their proximity with the nucleolus, heterochromatin and γH2AX foci. Our observations are consistent with the proposal that these IGH gene rearrangements take place in a specific perinucleolar “recombination compartment” where AID could be sequestered thus limiting the extent of its potentially deleterious off-target effects.
Collapse
Affiliation(s)
- Andrey Pichugin
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France.,Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
| | - Olga V Iarovaia
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France
| | - Alexey Gavrilov
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France
| | - Ilya Sklyar
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France
| | - Natalja Barinova
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France
| | - Aleksandr Barinov
- LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France
| | - Evgeny Ivashkin
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France.,Department of Experimental Neurocytology, Research Center of Neurology, Branch of Brain Research, Moscow, Russia
| | - Gersende Caron
- INSERM U1236, CHU de Rennes, Université Rennes 1, Rennes, France
| | - Said Aoufouchi
- UMR8200 CNRS, Université Paris-Sud, Institut de Cancérologie Gustave Roussy, Villejuif, France
| | - Sergey V Razin
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France.,Moscow State University, Moscow, Russia
| | - Thierry Fest
- INSERM U1236, CHU de Rennes, Université Rennes 1, Rennes, France
| | - Marc Lipinski
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France
| | - Yegor S Vassetzky
- UMR8126, CNRS, Université Paris Sud Paris Saclay, Institut Gustave Roussy, Villejuif, France.,LIA 1066, Laboratoire Franco-Russe de Recherche en Oncologie, Villejuif, France.,Moscow State University, Moscow, Russia
| |
Collapse
|
31
|
Bonnet-Garnier A, Kiêu K, Aguirre-Lavin T, Tar K, Flores P, Liu Z, Peynot N, Chebrout M, Dinnyés A, Duranthon V, Beaujean N. Three-dimensional analysis of nuclear heterochromatin distribution during early development in the rabbit. Chromosoma 2018; 127:387-403. [PMID: 29666907 PMCID: PMC6096579 DOI: 10.1007/s00412-018-0671-z] [Citation(s) in RCA: 6] [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: 10/12/2017] [Revised: 03/06/2018] [Accepted: 04/03/2018] [Indexed: 01/29/2023]
Abstract
Changes to the spatial organization of specific chromatin domains such as constitutive heterochromatin have been studied extensively in somatic cells. During early embryonic development, drastic epigenetic reprogramming of both the maternal and paternal genomes, followed by chromatin remodeling at the time of embryonic genome activation (EGA), have been observed in the mouse. Very few studies have been performed in other mammalian species (human, bovine, or rabbit) and the data are far from complete. During this work, we studied the three-dimensional organization of pericentromeric regions during the preimplantation period in the rabbit using specific techniques (3D-FISH) and tools (semi-automated image analysis). We observed that the pericentromeric regions (identified with specific probes for Rsat I and Rsat II genomic sequences) changed their shapes (from pearl necklaces to clusters), their nuclear localizations (from central to peripheral), as from the 4-cell stage. This reorganization goes along with histone modification changes and reduced amount of interactions with nucleolar precursor body surface. Altogether, our results suggest that the 4-cell stage may be a crucial window for events necessary before major EGA, which occurs during the 8-cell stage in the rabbit.
Collapse
Affiliation(s)
| | - Kiên Kiêu
- UR341 MaIAGE, INRA, Université Paris Saclay, 78350 Jouy-en-Josas, France
| | | | - Krisztina Tar
- Present Address: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- BioTalentum Ltd., Aulich Lajos str. 26, Gödöllő, 2100 Hungary
| | - Pierre Flores
- UMR BDR, INRA, ENVA, Université Paris Saclay, 78350 Jouy-en-Josas, France
| | - Zichuan Liu
- UMR BDR, INRA, ENVA, Université Paris Saclay, 78350 Jouy-en-Josas, France
- Present Address: Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101 China
| | - Nathalie Peynot
- UMR BDR, INRA, ENVA, Université Paris Saclay, 78350 Jouy-en-Josas, France
| | - Martine Chebrout
- UMR BDR, INRA, ENVA, Université Paris Saclay, 78350 Jouy-en-Josas, France
| | - András Dinnyés
- BioTalentum Ltd., Aulich Lajos str. 26, Gödöllő, 2100 Hungary
| | | | - Nathalie Beaujean
- UMR BDR, INRA, ENVA, Université Paris Saclay, 78350 Jouy-en-Josas, France
- Present Address: Univ Lyon, Université Claude Bernard Lyon 1, Inserm, INRA, Stem Cell and Brain Research Institute U1208, USC1361, 69500 Bron, France
| |
Collapse
|
32
|
Tardat M, Déjardin J. Telomere chromatin establishment and its maintenance during mammalian development. Chromosoma 2017; 127:3-18. [PMID: 29250704 PMCID: PMC5818603 DOI: 10.1007/s00412-017-0656-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 12/05/2017] [Accepted: 12/05/2017] [Indexed: 12/11/2022]
Abstract
Telomeres are specialized structures that evolved to protect the end of linear chromosomes from the action of the cell DNA damage machinery. They are composed of tandem arrays of repeated DNA sequences with a specific heterochromatic organization. The length of telomeric repeats is dynamically regulated and can be affected by changes in the telomere chromatin structure. When telomeres are not properly controlled, the resulting chromosomal alterations can induce genomic instability and ultimately the development of human diseases, such as cancer. Therefore, proper establishment, regulation, and maintenance of the telomere chromatin structure are required for cell homeostasis. Here, we review the current knowledge on telomeric chromatin dynamics during cell division and early development in mammals, and how its proper regulation safeguards genome stability.
Collapse
Affiliation(s)
- Mathieu Tardat
- Institute of Human Genetics, CNRS UMR 9002, 141 rue de la Cardonille, 34396, Montpellier, France.
| | - Jérôme Déjardin
- Institute of Human Genetics, CNRS UMR 9002, 141 rue de la Cardonille, 34396, Montpellier, France.
| |
Collapse
|
33
|
Nakaya M, Tanabe H, Takamatsu S, Hosokawa M, Mitani T. Visualization of the spatial arrangement of nuclear organization using three-dimensional fluorescence in situ hybridization in early mouse embryos: A new "EASI-FISH chamber glass" for mammalian embryos. J Reprod Dev 2017; 63:167-174. [PMID: 28190810 PMCID: PMC5401810 DOI: 10.1262/jrd.2016-172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fertilized oocyte begins cleavage, leading to zygotic gene activation (ZGA), which re-activates the resting genome to acquire totipotency. In this process, genomic function is regulated by the dynamic structural conversion in the nucleus. Indeed, a considerable number of genes that are essential for embryonic development are located near the pericentromeric regions, wherein the heterochromatin is formed. These genes are repressed transcriptionally in somatic cells. Three-dimensional fluorescence in situ hybridization (3D-FISH) enables the visualization of the intranuclear spatial arrangement, such as gene loci, chromosomal domains, and chromosome territories (CTs). However, the 3D-FISH approach in mammalian embryos has been limited to certain repeated sequences because of its unfavorable properties. In this study, we developed an easy-to-use chamber device (EASI-FISH chamber) for 3D-FISH in early embryos, and visualized, for the first time, the spatial arrangements of pericentromeric regions, the ZGA-activated gene (Zscan4) loci, and CTs (chromosome 7), simultaneously during the early cleavage stage of mouse embryos by 3D-FISH. As a result, it was revealed that morphological changes of the pericentromeric regions and CTs, and relocation of the Zscan4 loci in CTs, occurred in the 1- to 4-cell stage embryos, which was different from those in somatic cells. This convenient and reproducible 3D-FISH technique for mammalian embryos represents a valuable tool that will provide insights into the nuclear dynamics of development.
Collapse
Affiliation(s)
- Masataka Nakaya
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Hideyuki Tanabe
- Department of Evolutionary Studies of Biosystems, School of Advanced Sciences, SOKENDAI (The Graduate University for Advanced Studies), Kanagawa 240-0193, Japan
| | - Shingo Takamatsu
- Department of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Misaki Hosokawa
- Department of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan
| | - Tasuku Mitani
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama 649-6493, Japan.,Institute of Advanced Technology, Kindai University, Wakayama 642-0017, Japan
| |
Collapse
|
34
|
Heterochromatin and the molecular mechanisms of ‘parent-of-origin’ effects in animals. J Biosci 2016; 41:759-786. [DOI: 10.1007/s12038-016-9650-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
35
|
Borsos M, Torres-Padilla ME. Building up the nucleus: nuclear organization in the establishment of totipotency and pluripotency during mammalian development. Genes Dev 2016; 30:611-21. [PMID: 26980186 PMCID: PMC4803048 DOI: 10.1101/gad.273805.115] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In mammals, epigenetic reprogramming, the acquisition and loss of totipotency, and the first cell fate decision all occur within a 3-d window after fertilization from the one-cell zygote to the formation of the blastocyst. These processes are poorly understood in molecular detail, yet this is an essential prerequisite to uncover principles of stem cells, chromatin biology, and thus regenerative medicine. A unique feature of preimplantation development is the drastic genome-wide changes occurring to nuclear architecture. From studying somatic and in vitro cultured embryonic stem cells (ESCs) it is becoming increasingly established that the three-dimensional (3D) positions of genomic loci relative to each other and to specific compartments of the nucleus can act on the regulation of gene expression, potentially driving cell fate. However, the functionality, mechanisms, and molecular characteristics of the changes in nuclear organization during preimplantation development are only now beginning to be unraveled. Here, we discuss the peculiarities of nuclear compartments and chromatin organization during mammalian preimplantation development in the context of the transition from totipotency to pluripotency.
Collapse
Affiliation(s)
- Máté Borsos
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, U964, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale F-67404 Illkirch, France; Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München D-81377 München, Germany
| | - Maria-Elena Torres-Padilla
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, U964, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale F-67404 Illkirch, France; Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München D-81377 München, Germany
| |
Collapse
|
36
|
Sepulveda-Rincon LP, Solanas EDL, Serrano-Revuelta E, Ruddick L, Maalouf WE, Beaujean N. Early epigenetic reprogramming in fertilized, cloned, and parthenogenetic embryos. Theriogenology 2016; 86:91-8. [DOI: 10.1016/j.theriogenology.2016.04.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 02/25/2016] [Accepted: 03/14/2016] [Indexed: 12/17/2022]
|
37
|
Koné MC, Fleurot R, Chebrout M, Debey P, Beaujean N, Bonnet-Garnier A. Three-Dimensional Distribution of UBF and Nopp140 in Relationship to Ribosomal DNA Transcription During Mouse Preimplantation Development. Biol Reprod 2016; 94:95. [PMID: 26984997 DOI: 10.1095/biolreprod.115.136366] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 03/08/2016] [Indexed: 12/31/2022] Open
Abstract
The nucleolus is a dynamic nuclear compartment that is mostly involved in ribosome subunit biogenesis; however, it may also play a role in many other biological processes, such as stress response and the cell cycle. Mainly using electron microscopy, several studies have tried to decipher how active nucleoli are set up during early development in mice. In this study, we analyzed nucleologenesis during mouse early embryonic development using 3D-immunofluorescent detection of UBF and Nopp140, two proteins associated with different nucleolar compartments. UBF is a transcription factor that helps maintain the euchromatic state of ribosomal genes; Nopp140 is a phosphoprotein that has been implicated in pre-rRNA processing. First, using detailed image analyses and the in situ proximity ligation assay technique, we demonstrate that UBF and Nopp140 dynamic redistribution between the two-cell and blastocyst stages (time of implantation) is correlated with morphological and structural modifications that occur in embryonic nucleolar compartments. Our results also support the hypothesis that nucleoli develop at the periphery of nucleolar precursor bodies. Finally, we show that the RNA polymerase I inhibitor CX-5461: 1) disrupts transcriptional activity, 2) alters preimplantation development, and 3) leads to a complete reorganization of UBF and Nopp140 distribution. Altogether, our results underscore that highly dynamic changes are occurring in the nucleoli of embryos and confirm a close link between ribosomal gene transcription and nucleologenesis during the early stages of development.
Collapse
Affiliation(s)
| | - Renaud Fleurot
- UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France
| | - Martine Chebrout
- UMR BDR, INRA, ENVA, Université Paris Saclay, Jouy en Josas, France
| | - Pascale Debey
- Sorbonne-Universités, MNHN, CNRS, INSERM, Structure et instabilité des génomes, Paris, France
| | | | | |
Collapse
|
38
|
Sklyar I, Iarovaia OV, Gavrilov AA, Pichugin A, Germini D, Tsfasman T, Caron G, Fest T, Lipinski M, Razin SV, Vassetzky YS. Distinct Patterns of Colocalization of theCCND1andCMYCGenes With Their Potential Translocation PartnerIGHat Successive Stages of B-Cell Differentiation. J Cell Biochem 2016; 117:1506-10. [DOI: 10.1002/jcb.25516] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 02/10/2016] [Indexed: 01/22/2023]
Affiliation(s)
- Ilya Sklyar
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Institute of Gene Biology; Russian Academy of Sciences; Moscow Russia
| | - Olga V. Iarovaia
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Institute of Gene Biology; Russian Academy of Sciences; Moscow Russia
| | - Alexey A. Gavrilov
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Institute of Gene Biology; Russian Academy of Sciences; Moscow Russia
| | - Andrey Pichugin
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Peter the Great St. Petersburg Polytechnic University; St. Petersburg Russia
| | - Diego Germini
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Peter the Great St. Petersburg Polytechnic University; St. Petersburg Russia
| | - Tatiana Tsfasman
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
| | | | - Thierry Fest
- INSERM U917; Université de Rennes; Rennes France
| | - Marc Lipinski
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
| | - Sergey V. Razin
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Institute of Gene Biology; Russian Academy of Sciences; Moscow Russia
- Faculty of Biology; M.V. Lomonosov Moscow State University; 119992 Moscow Russia
| | - Yegor S. Vassetzky
- UMR8126, CNRS; Université Paris-Sud, Institut de Cancérologie Gustave Roussy; Villejuif France
- LIA1066; Laboratoire Franco-Russe de Recherche en Oncologie; Villejuif France
- Faculty of Biology; M.V. Lomonosov Moscow State University; 119992 Moscow Russia
| |
Collapse
|
39
|
Fulka H, Aoki F. Nucleolus Precursor Bodies and Ribosome Biogenesis in Early Mammalian Embryos: Old Theories and New Discoveries. Biol Reprod 2016; 94:143. [PMID: 26935600 DOI: 10.1095/biolreprod.115.136093] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 02/22/2016] [Indexed: 11/01/2022] Open
Abstract
In mammals, mature oocytes and early preimplantation embryos contain transcriptionally inactive structures termed nucleolus precursor bodies instead of the typical fibrillo-granular nucleoli. These nuclear organelles are essential and strictly of maternal origin. If they are removed from oocytes, the resulting embryos are unable to replace them and consequently fail to develop. Historically, nucleolus precursor bodies have been perceived as a passive repository site of nucleolar proteins that are required for embryos to form fully functional nucleoli. Recent results, however, contradict this long-standing dogma and show that these organelles are dispensable for nucleologenesis and ribosome biogenesis. In this article, we discuss the possible roles of nucleolus precursor bodies and propose how they might be involved in embryogenesis. Furthermore, we argue that these organelles are essential only shortly after fertilization and suggest that they might actively participate in centromeric chromatin establishment.
Collapse
Affiliation(s)
- Helena Fulka
- Institute of Animal Science, Prague, Czech Republic Institute of Molecular Genetics of the ASCR, Prague, Czech Republic
| | - Fugaku Aoki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan
| |
Collapse
|
40
|
Politz JCR, Scalzo D, Groudine M. The redundancy of the mammalian heterochromatic compartment. Curr Opin Genet Dev 2015; 37:1-8. [PMID: 26706451 DOI: 10.1016/j.gde.2015.10.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 01/05/2023]
Abstract
Two chromatin compartments are present in most mammalian cells; the first contains primarily euchromatic, early replicating chromatin and the second, primarily late-replicating heterochromatin, which is the subject of this review. Heterochromatin is concentrated in three intranuclear regions: the nuclear periphery, the perinucleolar space and in pericentromeric bodies. We review recent evidence demonstrating that the heterochromatic compartment is critically involved in global nuclear organization and the maintenance of genome stability, and discuss models regarding how this compartment is formed and maintained. We also evaluate our understanding of how heterochromatic sequences (herein named heterochromatic associated regions (HADs)) might be tethered within these regions and review experiments that reveal the stochastic nature of individual HAD positioning within the compartment. These investigations suggest a substantial level of functional redundancy within the heterochromatic compartment.
Collapse
Affiliation(s)
| | - David Scalzo
- Fred Hutchinson Cancer Research Center, Seattle, WA, United States
| | - Mark Groudine
- Fred Hutchinson Cancer Research Center, Seattle, WA, United States.
| |
Collapse
|
41
|
Fulka H, Kyogoku H, Zatsepina O, Langerova A, Fulka J. Can Nucleoli Be Markers of Developmental Potential in Human Zygotes? Trends Mol Med 2015; 21:663-672. [DOI: 10.1016/j.molmed.2015.09.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 09/18/2015] [Accepted: 09/18/2015] [Indexed: 01/10/2023]
|
42
|
Pauloin A, Adenot P, Hue-Beauvais C, Chanat E. The perilipin-2 (adipophilin) coat of cytosolic lipid droplets is regulated by an Arf1-dependent mechanism in HC11 mouse mammary epithelial cells. Cell Biol Int 2015; 40:143-55. [PMID: 26399370 DOI: 10.1002/cbin.10547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 09/19/2015] [Indexed: 12/11/2022]
Abstract
The cytosolic lipid droplets (cLDs) store excess intracellular lipids, and perilipin-2 is believed to protect cLDs from degradation. Here, we investigated the role of the small G-protein Arf1 and the proteasome in the fates of perilipin-2 and cLDs. In oleate-loaded cells, upon brefeldin A (BFA) treatment, perilipin-2 remained associated with cLDs for at least 30 min before significant release, and proteasomal degradation-mediated decrease was observed. Interestingly, the cLD population did not mimic the decline in perilipin-2. We tested several chemical modulators of regulators of Arf1 activity on the association of perilipin-2 with cLDs. QS11 and Exo2 accelerated the reduction in perilipin-2, although less than BFA. In contrast, Exo1 unexpectedly slowed down its degradation. Correlatively, BFA, QS11, and Exo2 enhanced the dissociation of perilipin-2 from cLDs, whereas Exo1 inhibited it. There was a synergistic effect of BFA with Exo2 and QS11, and of Exo2 with QS11, whereas Exo1 antagonized the effect of BFA without affecting that of Exo2 or QS11. We concluded that the Arf1 complex regulates the association of perilipin-2 with cLDs. Additionally, MG132 and BFA modified the number of cLDs over a relatively short period.
Collapse
Affiliation(s)
- Alain Pauloin
- INRA, UR1196 Génomique et Physiologie de la Lactation, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
| | - Pierre Adenot
- INRA-CRJ MIMA2 Platform, Domaine de Vilvert, UMR1198 Biologie du Développement et Reproduction, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
| | - Catherine Hue-Beauvais
- INRA, UR1196 Génomique et Physiologie de la Lactation, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
| | - Eric Chanat
- INRA, UR1196 Génomique et Physiologie de la Lactation, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
| |
Collapse
|
43
|
Popken J, Koehler D, Brero A, Wuensch A, Guengoer T, Thormeyer T, Wolf E, Cremer T, Zakhartchenko V. Positional changes of a pluripotency marker gene during structural reorganization of fibroblast nuclei in cloned early bovine embryos. Nucleus 2015; 5:542-54. [PMID: 25495180 PMCID: PMC4615807 DOI: 10.4161/19491034.2014.970107] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cloned bovine preimplantation embryos were generated by somatic cell nuclear transfer (SCNT) of bovine fetal fibroblasts with a silent copy of the pluripotency reporter gene GOF, integrated at a single site of a chromosome 13. GOF combines the regulatory Oct4/Pou5f1 sequence with the coding sequence for EGFP. EGFP expression served as a marker for pluripotency gene activation and was consistently detected in preimplantation embryos with 9 and more cells. Three-dimensional radial nuclear positions of GOF, its carrier chromosome territory and non-carrier homolog were measured in nuclei of fibroblasts, and of day 2 and day 4 embryos, carrying 2 to 9 and 15 to 22 cells, respectively. We tested, whether transcriptional activation was correlated with repositioning of GOF toward the nuclear interior either with a corresponding movement of its carrier chromosome territory 13 or via the formation of a giant chromatin loop. A significant shift of GOF away from the nuclear periphery was observed in day 2 embryos together with both carrier and non-carrier chromosome territories. At day 4, GOF, its carrier chromosome territory 13 and the non-carrier homolog had moved back toward the nuclear periphery. Similar movements of both chromosome territories ruled out a specific GOF effect. Pluripotency gene activation was preceded by a transient, radial shift of GOF toward the nuclear interior. The persistent co-localization of GOF with its carrier chromosome territory rules out the formation of a giant chromatin loop during GOF activation.
Collapse
Key Words
- (bovine) preimplantation embryos, chromosome territories, nuclear architecture, nuclear reprogramming, pluripotency gene activation, somatic cell nuclear transfer
- BFF, bovine fetal fibroblasts; BTA, Bos taurus; CLSM, confocal laser scanning microscopy; CT, chromosome territory; eADS, enhanced absolute 3D distances to surfaces; IVF, in vitro fertilization; MGA, major embryonic genome activation; GOF, Oct4/Pou5f1-EGF
Collapse
Affiliation(s)
- Jens Popken
- a Division of Anthropology and Human Genetics Biocenter ; LMU Munich ; Martinsried , Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Popken J, Brero A, Koehler D, Schmid VJ, Strauss A, Wuensch A, Guengoer T, Graf A, Krebs S, Blum H, Zakhartchenko V, Wolf E, Cremer T. Reprogramming of fibroblast nuclei in cloned bovine embryos involves major structural remodeling with both striking similarities and differences to nuclear phenotypes of in vitro fertilized embryos. Nucleus 2015; 5:555-89. [PMID: 25482066 PMCID: PMC4615760 DOI: 10.4161/19491034.2014.979712] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Nuclear landscapes were studied during preimplantation development of bovine embryos, generated either by in vitro fertilization (IVF), or generated as cloned embryos by somatic cell nuclear transfer (SCNT) of bovine fetal fibroblasts, using 3-dimensional confocal laser scanning microscopy (3D-CLSM) and structured illumination microscopy (3D-SIM). Nuclear landscapes of IVF and SCNT embryonic nuclei were compared with each other and with fibroblast nuclei. We demonstrate that reprogramming of fibroblast nuclei in cloned embryos requires changes of their landscapes similar to nuclei of IVF embryos. On the way toward the 8-cell stage, where major genome activation occurs, a major lacuna, enriched with splicing factors, was formed in the nuclear interior and chromosome territories (CTs) were shifted toward the nuclear periphery. During further development the major lacuna disappeared and CTs were redistributed throughout the nuclear interior forming a contiguous higher order chromatin network. At all stages of development CTs of IVF and SCNT embryonic nuclei were built up from chromatin domain clusters (CDCs) pervaded by interchromatin compartment (IC) channels. Quantitative analyses revealed a highly significant enrichment of RNA polymerase II and H3K4me3, a marker for transcriptionally competent chromatin, at the periphery of CDCs. In contrast, H3K9me3, a marker for silent chromatin, was enriched in the more compacted interior of CDCs. Despite these striking similarities, we also detected major differences between nuclear landscapes of IVF and cloned embryos. Possible implications of these differences for the developmental potential of cloned animals remain to be investigated. We present a model, which integrates generally applicable structural and functional features of the nuclear landscape.
Collapse
Key Words
- 3D-CLSM, 3-dimensional confocal laser scanning microscopy
- 3D-SIM, 3-dimensional structured illumination microscopy
- B23, nucleophosmin B23
- BTA, Bos taurus
- CDC, chromatin domain cluster
- CT, chromosome territory
- EM, electron microscopy
- ENC, embryonic nuclei with conventional nuclear architecture
- ENP, embryonic nuclei with peripheral CT distribution
- H3K4me3
- H3K4me3, histone H3 with tri-methylated lysine 4
- H3K9me3
- H3K9me3, histone H3 with tri-methylated lysine 9
- H3S10p, histone H3 with phosphorylated serine 10
- IC, interchromatin compartment
- IVF, in vitro fertilization
- MCB, major chromatin body
- PR, perichromatin region
- RNA polymerase II
- RNA polymerase II-S2p, RNA polymerase II with phosphorylated serine 2 of its CTD domain
- RNA polymerase II-S5p, RNA polymerase II with phosphorylated serine 5 of its CTD domain
- SC-35, splicing factor SC-35
- SCNT, somatic cell nuclear transfer.
- bovine preimplantation development
- chromatin domain
- chromosome territory
- embryonic genome activation
- in vitro fertilization (IVF)
- interchromatin compartment
- major EGA, major embryonic genome activation
- somatic cell nuclear transfer (SCNT)
Collapse
Affiliation(s)
- Jens Popken
- a Division of Anthropology and Human Genetics ; Biocenter; LMU Munich ; Munich , Germany
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Hashimoto M, Sato T, Muroyama Y, Fujimura L, Hatano M, Saito T. Nepro is localized in the nucleolus and essential for preimplantation development in mice. Dev Growth Differ 2015; 57:529-38. [PMID: 26178919 DOI: 10.1111/dgd.12232] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Revised: 05/26/2015] [Accepted: 05/27/2015] [Indexed: 12/31/2022]
Abstract
We generated knockout (KO) mice of Nepro, which has been shown to be necessary to maintain neural progenitor cells downstream of Notch in the mouse developing neocortex by using knockdown experiments, to explore its function in embryogenesis. Nepro KO embryos were morphologically indistinguishable from wild type (WT) embryos until the morula stage but failed in blastocyst formation, and many cells of the KO embryos resulted in apoptosis. We found that Nepro was localized in the nucleolus at the blastocyst stage. The number of nucleolus precursor bodies (NPBs) and nucleoli per nucleus was significantly higher in Nepro KO embryos compared with WT embryos later than the 2-cell stage. Furthermore, at the morula stage, whereas 18S rRNA and ribosomal protein S6 (rpS6), which are components of the ribosome, were distributed to the cytoplasm in WT embryos, they were mainly localized in the nucleoli in Nepro KO embryos. In addition, in Nepro KO embryos, the amount of the mitochondria-associated p53 protein increased, and Cytochrome c was distributed in the cytoplasm. These findings indicate that Nepro is a nucleolus-associated protein, and its loss leads to the apoptosis before blastocyst formation in mice.
Collapse
Affiliation(s)
- Masakazu Hashimoto
- Department of Developmental Biology, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan
| | - Tatsuya Sato
- Department of Developmental Biology, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan
| | - Yuko Muroyama
- Department of Developmental Biology, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan
| | - Lisa Fujimura
- Biomedical Research Center, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan
| | - Masahiko Hatano
- Biomedical Research Center, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan.,Department of Biomedical Science, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan
| | - Tetsuichiro Saito
- Department of Developmental Biology, Graduate School of Medicine, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba, 260-8670, Japan
| |
Collapse
|
46
|
Dang-Nguyen TQ, Torres-Padilla ME. How cells build totipotency and pluripotency: nuclear, chromatin and transcriptional architecture. Curr Opin Cell Biol 2015; 34:9-15. [PMID: 25935759 DOI: 10.1016/j.ceb.2015.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/25/2015] [Accepted: 04/14/2015] [Indexed: 01/15/2023]
Abstract
Totipotent and pluripotent cells display different degrees of cellular plasticity. After fertilization, embryonic cells transit naturally from a totipotent to a pluripotent state. Major changes in nuclear architecture, chromatin mobility and gene expression occur during this transition. In particular, nuclear architecture has recently emerged as a potential regulator of heterochromatin formation in the early embryo. Future research should address whether a causal, functional link between nuclear organization and gene regulation is a general theme during reprogramming and the formation of pluripotent cells.
Collapse
Affiliation(s)
- Thanh Quang Dang-Nguyen
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM U964, Université de Strasbourg, F-67404 Illkirch, France
| | - Maria-Elena Torres-Padilla
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM U964, Université de Strasbourg, F-67404 Illkirch, France.
| |
Collapse
|
47
|
Ollion J, Loll F, Cochennec J, Boudier T, Escudé C. Proliferation-dependent positioning of individual centromeres in the interphase nucleus of human lymphoblastoid cell lines. Mol Biol Cell 2015; 26:2550-60. [PMID: 25947134 PMCID: PMC4571307 DOI: 10.1091/mbc.e14-05-1002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 04/27/2015] [Indexed: 01/01/2023] Open
Abstract
Centromeres are not randomly distributed in interphase nuclei. High-throughput imaging provides an accurate characterization of how their organization varies as a function of the proliferation state in human lymphoblastoid cells. The results suggest the existence of mechanisms that drive the nuclear positioning of centromeres. The cell nucleus is a highly organized structure and plays an important role in gene regulation. Understanding the mechanisms that sustain this organization is therefore essential for understanding genome function. Centromeric regions (CRs) of chromosomes have been known for years to adopt specific nuclear positioning patterns, but the significance of this observation is not yet completely understood. Here, using a combination of fluorescence in situ hybridization and immunochemistry on fixed human cells and high-throughput imaging, we directly and quantitatively investigated the nuclear positioning of specific human CRs. We observe differential attraction of individual CRs toward both the nuclear border and the nucleoli, the former being enhanced in nonproliferating cells and the latter being enhanced in proliferating cells. Similar positioning patterns are observed in two different lymphoblastoid cell lines. Moreover, the positioning of CRs differs from that of noncentromeric regions, and CRs display specific orientations within chromosome territories. These results suggest the existence of not-yet-characterized mechanisms that drive the nuclear positioning of CRs and therefore pave the way toward a better understanding of how CRs affect nuclear organization.
Collapse
Affiliation(s)
- Jean Ollion
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - François Loll
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Julien Cochennec
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Thomas Boudier
- Université Pierre et Marie Curie, Sorbonne Universités, 75005 Paris, France
| | - Christophe Escudé
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| |
Collapse
|
48
|
Abstract
In mammals, pluripotent stem cells can give rise to every cell type of embryonic lineage, and hold great potential in regenerative medicine and disease modeling. Guided by the mechanism underlying pluripotency, pluripotent stem cells have been successfully induced through manipulating the transcriptional and epigenetic networks of various differentiated cell types. However, the factors that confer totipotency, the ability to give rise to cells in both embryonic and extra-embryonic lineages, still remain poorly understood. It is currently unknown whether totipotency can be induced and maintained in vitro. In this review, we summarize the current progress in the field, with the aim of providing a foundation for understanding the mechanisms that regulate totipotency.
Collapse
Affiliation(s)
- Falong Lu
- Howard Hughes Medical Institute, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115 ; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115 ; Department of Genetics, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115
| | - Yi Zhang
- Howard Hughes Medical Institute, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115 ; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115 ; Department of Genetics, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115 ; Harvard Stem Cell Institute, Harvard Medical School, WAB-149G, 200 Longwood Avenue, Boston, MA 02115
| |
Collapse
|
49
|
Boulesteix C, Beaujean N. Fluorescent immunodetection of epigenetic modifications on preimplantation mouse embryos. Methods Mol Biol 2015; 1222:113-26. [PMID: 25287342 DOI: 10.1007/978-1-4939-1594-1_9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A common problem in research laboratories that study the mammalian embryo after nuclear transfer is the limited supply of material. For this reason, new methods are continually developed, and existing methods for cells in culture are adapted to suit this peculiar experimental model. Among them is the fluorescent immunodetection. Fluorescent immuno-detection on fixed embryos is an invaluable technique to detect and locate proteins, especially nuclear ones such as modified histones, in single embryos thanks to its specificity and its sensitivity. Moreover, with specific fixation procedures that preserve the 3D shape of the embryos, immunostaining can now be performed on whole-mount embryos. Target proteins are detected by specific binding of first antibody usually nonfluorescent, and revealed with a second antibody conjugated with a fluorochrome directed specifically against the host animal in which the first antibody was produced. The result can then be observed on a microscope equipped with fluorescent detection. Here, we describe the 3D fluorescent immunodetection of epigenetic modifications in mouse embryos. This procedure can be used on nuclear transferred embryos but also on in vivo-collected, in vitro-developed and in vitro-fertilized ones.
Collapse
Affiliation(s)
- Claire Boulesteix
- UMR1198 Biologie du Développement et Reproduction, INRA, Domaine de Vilvert, 78352, Jouy-en-Josas Cedex, France
| | | |
Collapse
|
50
|
Salvaing J, Li Y, Beaujean N, O'Neill C. Determinants of valid measurements of global changes in 5ʹ-methylcytosine and 5ʹ-hydroxymethylcytosine by immunolocalisation in the early embryo. Reprod Fertil Dev 2015; 27:755-64. [DOI: 10.1071/rd14136] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 08/26/2014] [Indexed: 12/15/2022] Open
Abstract
A classical model of epigenetic reprogramming of methyl-cytosine–phosphate–guanine (CpG) dinucleotides within the genome of the early embryo involves a process of active demethylation of the paternally derived genome immediately following fertilisation, creating marked asymmetry in global cytosine methylation levels in male and female pronuclei, followed by passive demethylation of the maternally derived genome over subsequent cell cycles. This model has dominated thinking in developmental epigenetics over recent decades. Recent re-analyses of the model show that demethylation of the paternally derived genome is more modest than formerly thought and results in overall similar levels of methylation of the paternal and maternal pronuclei in presyngamal zygotes, although there is little evidence for a pervasive process of passive demethylation during the cleavage stage of development. In contrast, the inner cell mass of the blastocyst shows some loss of methylation within specific classes of loci. Improved methods of chemical analysis now allow global base-level analysis of modifications to CpG dinucleotides within the cells of the early embryo, yet the low cost and convenience of the immunolocalisation techniques mean that they still have a valuable place in the analysis of the epigenetics of embryo development. In this review we consider the key strengths and weaknesses of this methodology and some factors required for its valid use and interpretation.
Collapse
|