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Dubos T, Poulet A, Thomson G, Péry E, Chausse F, Tatout C, Desset S, van Wolfswinkel JC, Jacob Y. NODeJ: an ImageJ plugin for 3D segmentation of nuclear objects. BMC Bioinformatics 2022; 23:216. [PMID: 35668354 PMCID: PMC9169307 DOI: 10.1186/s12859-022-04743-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 05/23/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The three-dimensional nuclear arrangement of chromatin impacts many cellular processes operating at the DNA level in animal and plant systems. Chromatin organization is a dynamic process that can be affected by biotic and abiotic stresses. Three-dimensional imaging technology allows to follow these dynamic changes, but only a few semi-automated processing methods currently exist for quantitative analysis of the 3D chromatin organization. RESULTS We present an automated method, Nuclear Object DetectionJ (NODeJ), developed as an imageJ plugin. This program segments and analyzes high intensity domains in nuclei from 3D images. NODeJ performs a Laplacian convolution on the mask of a nucleus to enhance the contrast of intra-nuclear objects and allow their detection. We reanalyzed public datasets and determined that NODeJ is able to accurately identify heterochromatin domains from a diverse set of Arabidopsis thaliana nuclei stained with DAPI or Hoechst. NODeJ is also able to detect signals in nuclei from DNA FISH experiments, allowing for the analysis of specific targets of interest. CONCLUSION AND AVAILABILITY NODeJ allows for efficient automated analysis of subnuclear structures by avoiding the semi-automated steps, resulting in reduced processing time and analytical bias. NODeJ is written in Java and provided as an ImageJ plugin with a command line option to perform more high-throughput analyses. NODeJ can be downloaded from https://gitlab.com/axpoulet/image2danalysis/-/releases with source code, documentation and further information avaliable at https://gitlab.com/axpoulet/image2danalysis . The images used in this study are publicly available at https://www.brookes.ac.uk/indepth/images/ and https://doi.org/10.15454/1HSOIE .
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Affiliation(s)
- Tristan Dubos
- GReD, CNRS, INSERM, Université Clermont Auvergne, Clermont-Ferrand, France
- Institut Pascal, Université Clermont Auvergne, Clermont-Ferrand, France
| | - Axel Poulet
- Department of Molecular, Cellular and Developmental Biology, Faculty of Arts and Sciences, Yale University, New Haven, USA
| | - Geoffrey Thomson
- Department of Molecular, Cellular and Developmental Biology, Faculty of Arts and Sciences, Yale University, New Haven, USA
| | - Emilie Péry
- Institut Pascal, Université Clermont Auvergne, Clermont-Ferrand, France
| | - Frédéric Chausse
- Institut Pascal, Université Clermont Auvergne, Clermont-Ferrand, France
| | - Christophe Tatout
- GReD, CNRS, INSERM, Université Clermont Auvergne, Clermont-Ferrand, France
| | - Sophie Desset
- GReD, CNRS, INSERM, Université Clermont Auvergne, Clermont-Ferrand, France
| | - Josien C. van Wolfswinkel
- Department of Molecular, Cellular and Developmental Biology, Faculty of Arts and Sciences, Yale University, New Haven, USA
| | - Yannick Jacob
- Department of Molecular, Cellular and Developmental Biology, Faculty of Arts and Sciences, Yale University, New Haven, USA
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Brändle F, Frühbauer B, Jagannathan M. Principles and functions of pericentromeric satellite DNA clustering into chromocenters. Semin Cell Dev Biol 2022; 128:26-39. [PMID: 35144860 DOI: 10.1016/j.semcdb.2022.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 02/03/2022] [Accepted: 02/03/2022] [Indexed: 12/29/2022]
Abstract
Simple non-coding tandem repeats known as satellite DNA are observed widely across eukaryotes. These repeats occupy vast regions at the centromere and pericentromere of chromosomes but their contribution to cellular function has remained incompletely understood. Here, we review the literature on pericentromeric satellite DNA and discuss its organization and functions across eukaryotic species. We specifically focus on chromocenters, DNA-dense nuclear foci that contain clustered pericentromeric satellite DNA repeats from multiple chromosomes. We first discuss chromocenter formation and the roles that epigenetic modifications, satellite DNA transcripts and sequence-specific satellite DNA-binding play in this process. We then review the newly emerging functions of chromocenters in genome encapsulation, the maintenance of cell fate and speciation. We specifically highlight how the rapid divergence of satellite DNA repeats impacts reproductive isolation between closely related species. Together, we underline the importance of this so-called 'junk DNA' in fundamental biological processes.
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Affiliation(s)
- Franziska Brändle
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, Zürich CH-8093, Switzerland
| | - Benjamin Frühbauer
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, Zürich CH-8093, Switzerland
| | - Madhav Jagannathan
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, Zürich CH-8093, Switzerland.
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Pavlova P, van Zanten M, Snoek BL, de Jong H, Fransz P. 2D morphometric analysis of Arabidopsis thaliana nuclei reveals characteristic profiles of different cell types and accessions. Chromosome Res 2021. [PMID: 34665365 DOI: 10.1007/s10577-021-09673-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 09/19/2021] [Accepted: 09/22/2021] [Indexed: 11/21/2022]
Abstract
Functional changes of cells upon developmental switches and in response to environmental cues are often reflected in nuclear phenotypes, showing distinctive chromatin states corresponding to transcriptional changes. Such characteristic nuclear shapes have been microscopically monitored and can be quantified after differential staining of euchromatin and heterochromatin domains. Here, we examined several nuclear parameters (size, DNA content, DNA density, chromatin compaction, relative heterochromatin fraction (RHF), and number of chromocenters) in relation to spatial distribution of genes and transposon elements (TEs), using standard 2D fluorescence microscopy. We provide nuclear profiles for different cell types and different accessions of Arabidopsis thaliana. A variable, yet significant, fraction of TEs was found outside chromocenters in all cell types, except for guard cells. The latter cell type features nuclei with the highest level of chromatin compaction, while their chromocenters seem to contain gene-rich regions. The highest number of parameter correlations was found in the accession Cvi, whereas Ler showed only few correlations. This may point at differences in phenotype robustness between accessions. The significantly high association of NOR chromocenters in accessions Ws and Cvi corresponds to their low RHF level.
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Frank L, Weinmann R, Erdel F, Trojanowski J, Rippe K. Transcriptional Activation of Heterochromatin by Recruitment of dCas9 Activators. Methods Mol Biol 2021; 2351:307-20. [PMID: 34382197 DOI: 10.1007/978-1-0716-1597-3_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
The transition from silenced heterochromatin to a biologically active state and vice versa is a fundamental part of the implementation of cell type-specific gene expression programs. To reveal structure-function relationships and dissect the underlying mechanisms, experiments that ectopically induce transcription are highly informative. In particular, the approach to perturb chromatin states by recruiting fusions of the catalytically inactive dCas9 protein in a sequence-specific manner to a locus of interest has been used in numerous applications. Here, we describe how this approach can be applied to activate pericentric heterochromatin (PCH) in mouse cells as a prototypic silenced state by providing protocols for the following workflow: (a) Recruitment of dCas9 fusion constructs with the strong transcriptional activator VPR to PCH. (b) Analysis of the resulting changes in chromatin compaction, epigenetic marks, and active transcription by fluorescence microscopy-based readouts. (c) Automated analysis of the resulting images with a set of scripts in the R programming language. Furthermore, we discuss how parameters for chromatin decondensation and active transcription are extracted from these experiments and can be combined with other readouts to gain insights into PCH activation.
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Kurita K, Sakamoto Y, Naruse S, Matsunaga TM, Arata H, Higashiyama T, Habu Y, Utsumi Y, Utsumi C, Tanaka M, Takahashi S, Kim JM, Seki M, Sakamoto T, Matsunaga S. Intracellular localization of histone deacetylase HDA6 in plants. J Plant Res 2019; 132:629-640. [PMID: 31338715 DOI: 10.1007/s10265-019-01124-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 07/03/2019] [Indexed: 05/26/2023]
Abstract
Histone modification is an important epigenetic mechanism in eukaryotes. Histone acetyltransferase and deacetylase regulate histone acetylation levels antagonistically, leading to dynamic control of chromatin structure. One of the histone deacetylases, HDA6, is involved in gene silencing in the heterochromatin regions, chromocenter formation, and metabolic adaptation under drought stress. Although HDA6 plays an important role in chromatin control and response to drought stress, its intracellular localization has not been observed in detail. In this paper, we generated transformants expressing HDA6-GFP in the model plant, Arabidopsis thaliana, and the crops, rice, and cassava. We observed the localization of the fusion protein and showed that HDA6-GFP was expressed in the whole root and localized at the nucleus in Arabidopsis, rice, and cassava. Remarkably, HDA6-GFP clearly formed speckles that were actively colocalized with chromocenters in Arabidopsis root meristem. In contrast, such speckles were unlikely to be formed in rice or cassava. Because AtHDA6 directly binds to the acetate synthesis genes, which function in drought tolerance, we performed live imaging analyses to examine the cellular dynamics of pH in roots and the subnuclear dynamics of AtHDA6 responding to acetic acid treatment. The number of HDA6 speckles increased during drought stress, suggesting a role in contributing to drought stress tolerance.
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Affiliation(s)
- Kazuki Kurita
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan
| | - Yuki Sakamoto
- Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan
| | - Sota Naruse
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan
| | - Tomoko M Matsunaga
- Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan
| | - Hideyuki Arata
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan
| | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan
| | - Yoshiki Habu
- Plant Physiology Research Unit, Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 2-1-2 Kannondai, Tsukuba, Ibaraki, 305-8602, Japan
| | - Yoshinori Utsumi
- Plant Genomic Network Research Team, RIKEN Centre for Sustainable Resource Science (CSRS), 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Chikako Utsumi
- Plant Genomic Network Research Team, RIKEN Centre for Sustainable Resource Science (CSRS), 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Maho Tanaka
- Plant Genomic Network Research Team, RIKEN Centre for Sustainable Resource Science (CSRS), 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Satoshi Takahashi
- Plant Genomic Network Research Team, RIKEN Centre for Sustainable Resource Science (CSRS), 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Jong-Myong Kim
- Plant Genomic Network Research Team, RIKEN Centre for Sustainable Resource Science (CSRS), 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Motoaki Seki
- Plant Genomic Network Research Team, RIKEN Centre for Sustainable Resource Science (CSRS), 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
- Plant Epigenome Regulation Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Takuya Sakamoto
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan
| | - Sachihiro Matsunaga
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan.
- Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510, Japan.
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Eyster C, Chuong HH, Lee CY, Pezza RJ, Dawson D. The pericentromeric heterochromatin of homologous chromosomes remains associated after centromere pairing dissolves in mouse spermatocyte meiosis. Chromosoma 2019; 128:355-367. [PMID: 31165256 PMCID: PMC6823320 DOI: 10.1007/s00412-019-00708-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 05/02/2019] [Accepted: 05/09/2019] [Indexed: 01/27/2023]
Abstract
In meiosis, crossovers between homologous chromosomes link them together. This enables them to attach to microtubules of the meiotic spindle as a unit, such that the homologs will be pulled away from one another at anaphase I. Homologous pairs can sometimes fail to become linked by crossovers. In some organisms, these non-exchange partners are still able to segregate properly. In several organisms, associations between the centromeres of non-exchange partners occur in meiotic prophase. These associations have been proposed to promote segregation in meiosis I. But it is unclear how centromere pairing could promote subsequent proper segregation. Here we report that meiotic centromere pairing of chromosomes in mouse spermatocytes allows the formation of an association between chromosome pairs. We find that heterochromatin regions of homologous centromeres remain associated even after centromere-pairing dissolves. Our results suggest the model that, in mouse spermatocytes, heterochromatin maintains the association of homologous centromeres in the absence crossing-over.
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Affiliation(s)
- Craig Eyster
- Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Hoa H Chuong
- Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Chih-Ying Lee
- Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Roberto J Pezza
- Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.
- Department of Cell Biology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA.
| | - Dean Dawson
- Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.
- Department of Cell Biology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA.
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Maezawa S, Hasegawa K, Alavattam KG, Funakoshi M, Sato T, Barski A, Namekawa SH. SCML2 promotes heterochromatin organization in late spermatogenesis. J Cell Sci 2018; 131:jcs.217125. [PMID: 30097555 DOI: 10.1242/jcs.217125] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 07/31/2018] [Indexed: 12/15/2022] Open
Abstract
Spermatogenesis involves the progressive reorganization of heterochromatin. However, the mechanisms that underlie the dynamic remodeling of heterochromatin remain unknown. Here, we identify SCML2, a germline-specific Polycomb protein, as a critical regulator of heterochromatin organization in spermatogenesis. We show that SCML2 accumulates on pericentromeric heterochromatin (PCH) in male germ cells, where it suppresses PRC1-mediated monoubiquitylation of histone H2A at Lysine 119 (H2AK119ub) and promotes deposition of PRC2-mediated H3K27me3 during meiosis. In postmeiotic spermatids, SCML2 is required for heterochromatin organization, and the loss of SCML2 leads to the formation of ectopic patches of facultative heterochromatin. Our data suggest that, in the absence of SCML2, the ectopic expression of somatic lamins drives this process. Furthermore, the centromere protein CENP-V is a specific marker of PCH in postmeiotic spermatids, and SCML2 is required for CENP-V localization on PCH. Given the essential functions of PRC1 and PRC2 for genome-wide gene expression in spermatogenesis, our data suggest that heterochromatin organization and spermatogenesis-specific gene expression are functionally linked. We propose that SCML2 coordinates the organization of heterochromatin and gene expression through the regulation of Polycomb complexes.
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Affiliation(s)
- So Maezawa
- Division of Reproductive Sciences, Division of Developmental Biology, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA .,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 49267, USA.,Department of Animal Science and Biotechnology, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa 252-5201, Japan
| | - Kazuteru Hasegawa
- Division of Reproductive Sciences, Division of Developmental Biology, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 49267, USA
| | - Kris G Alavattam
- Division of Reproductive Sciences, Division of Developmental Biology, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 49267, USA
| | - Mayuka Funakoshi
- Department of Animal Science and Biotechnology, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa 252-5201, Japan
| | - Taiga Sato
- Department of Animal Science and Biotechnology, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa 252-5201, Japan
| | - Artem Barski
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 49267, USA.,Division of Allergy and Immunology, Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Satoshi H Namekawa
- Division of Reproductive Sciences, Division of Developmental Biology, Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA .,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 49267, USA
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Alvarenga EM, Imperador CH, Bardella VB, Rodrigues VL, Mondin M, Cabral-de-Mello DC, Moraes AS, Mello MLS. Histone acetylation and methylation marks in chromatin of Panstrongylus megistus (Hemiptera, Reduviidae). Acta Histochem 2018; 120:572-577. [PMID: 30005894 DOI: 10.1016/j.acthis.2018.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/03/2018] [Accepted: 07/03/2018] [Indexed: 12/12/2022]
Abstract
Panstrongylus megistus, a potential vector of Chagas disease, currently occupies a wider geographic distribution in Brazil than Triatoma infestans, another member of the hemipteran Reduviidae family and a vector of the same disease. A small heterochromatic body (chromocenter) formed by the Y chromosome is evident in the somatic cells of P. megistus, differing in size and chromosome type contribution from the well-studied chromocenters present in T. infestans. While the overall distribution of histone epigenetic marks differ when comparing the heterochromatin and euchromatin territories in T. infestans, no similar data have been established for other hemipteran reduviids, including P. megistus. In the present work, histone acetylation and methylation marks were investigated in cells of Malpighian tubules of P. megistus 5th instar nymphs using immunocytochemical assays and compared to previously published data for T. infestans. Although similarities between these species were found regarding absence of acetylated H3K9, H4K8 and H4K16, and H3K9me and H3K9me2 in the chromocenter, presence of these marks in euchromatin, and presence of H3K9me3 in the chromocenter, no intimate association of acetylated H4K8 and 18S rDNA was revealed in the chromocenter of P. megistus. The elevated abundance of H3K9me2 marks at the nuclear periphery in P. megistus cells, differing from data for T. infestans, is suggested to reflect differences in the interaction of lamina-associated chromatin domains with the nuclear lamina, methyl-transferase modulation and/or association with the last DNA endoreplication step in 5th instar nymphs, which is a matter for further investigation.
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Baroux C, Pecinka A, Fuchs J, Kreth G, Schubert I, Grossniklaus U. Non-random chromosome arrangement in triploid endosperm nuclei. Chromosoma 2017; 126:115-24. [PMID: 26892012 DOI: 10.1007/s00412-016-0578-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/01/2016] [Accepted: 02/03/2016] [Indexed: 01/19/2023]
Abstract
The endosperm is at the center of successful seed formation in flowering plants. Being itself a product of fertilization, it is devoted to nourish the developing embryo and typically possesses a triploid genome consisting of two maternal and one paternal genome complement. Interestingly, endosperm development is controlled by epigenetic mechanisms conferring parent-of-origin-dependent effects that influence seed development. In the model plant Arabidopsis thaliana, we have previously described an endosperm-specific heterochromatin fraction, which increases with higher maternal, but not paternal, genome dosage. Here, we report a detailed analysis of chromosomal arrangement and association frequency in endosperm nuclei. We found that centromeric FISH signals in isolated nuclei show a planar alignment that may results from a semi-rigid, connective structure between chromosomes. Importantly, we found frequent pairwise association of centromeres, chromosomal segments, and entire arms of chromosomes in 3C endosperm nuclei. These associations deviate from random expectations predicted by numerical simulations. Therefore, we suggest a non-random chromosomal organization in the triploid nuclei of Arabidopsis endosperm. This contrasts with the prevailing random arrangement of chromosome territories in somatic nuclei. Based on observations on a series of nuclei with varying parental genome ratios, we propose a model where chromosomes associate pairwise involving one maternal and one paternal complement. The functional implications of this predicted chromosomal arrangement are discussed.
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Müller I, Merk B, Voss KO, Averbeck N, Jakob B, Durante M, Taucher-Scholz G. Species conserved DNA damage response at the inactive human X chromosome. Mutat Res 2013; 756:30-36. [PMID: 23628434 DOI: 10.1016/j.mrgentox.2013.04.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 04/21/2013] [Indexed: 06/02/2023]
Abstract
Chromatin modifications are long known as an essential part of the orchestrated response resulting in the repair of radiation-induced DNA double-strand breaks (DSBs). Only recently, however, the influence of the chromatin architecture itself on the DNA damage response has been recognised. Thus for heterochromatic DSBs the sensing and early recruitment of repair factors to the lesion occurs within the heterochromatic compartments, but the damage sites are subsequently relocated from the inside to the outside of the heterochromatin. While previous studies were accomplished at the constitutive heterochromatin of centromeric regions in mouse and flies, here we examine the DSB repair at the facultative heterochromatin of the inactive X chromosome (Xi) in humans. Using heavy ion irradiation we show that at later times after irradiation the DSB damage streaks bend around the Xi verifying that the relocation process is conserved between species and not specialised to repetitive sequences only. In addition, to measure chromatin relaxation at rare positions within the genome, we established live cell microscopy at the GSI microbeam thus allowing the aimed irradiation of small nuclear structures like the Xi. Chromatin decondensation at DSBs within the Xi is clearly visible within minutes as a continuous decrease of the DNA staining over time, comparable to the DNA relaxation revealed at DSBs in mouse chromocenters. Furthermore, despite being conserved between species, slight differences in the underlying regulation of these processes in heterochromatic DSBs are apparent.
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Affiliation(s)
- Iris Müller
- GSI Helmholtzzentrum für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany.
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