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Kiyomitsu A, Nishimura T, Hwang SJ, Ansai S, Kanemaki MT, Tanaka M, Kiyomitsu T. Ran-GTP assembles a specialized spindle structure for accurate chromosome segregation in medaka early embryos. Nat Commun 2024; 15:981. [PMID: 38302485 PMCID: PMC10834446 DOI: 10.1038/s41467-024-45251-w] [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: 07/09/2023] [Accepted: 01/19/2024] [Indexed: 02/03/2024] Open
Abstract
Despite drastic cellular changes during cleavage, a mitotic spindle assembles in each blastomere to accurately segregate duplicated chromosomes. Mechanisms of mitotic spindle assembly have been extensively studied using small somatic cells. However, mechanisms of spindle assembly in large vertebrate embryos remain little understood. Here, we establish functional assay systems in medaka (Oryzias latipes) embryos by combining CRISPR knock-in with auxin-inducible degron technology. Live imaging reveals several unexpected features of microtubule organization and centrosome positioning that achieve rapid, accurate cleavage. Importantly, Ran-GTP assembles a dense microtubule network at the metaphase spindle center that is essential for chromosome segregation in early embryos. This unique spindle structure is remodeled into a typical short, somatic-like spindle after blastula stages, when Ran-GTP becomes dispensable for chromosome segregation. We propose that despite the presence of centrosomes, the chromosome-derived Ran-GTP pathway has essential roles in functional spindle assembly in large, rapidly dividing vertebrate early embryos, similar to acentrosomal spindle assembly in oocytes.
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Affiliation(s)
- Ai Kiyomitsu
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Toshiya Nishimura
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
- Hokkaido University Fisheries Sciences, 3-1-1, Minato-cho, Hakodate, Hokkaido, 041-8611, Japan
| | - Shiang Jyi Hwang
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Satoshi Ansai
- Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Laboratory of Genome Editing Breeding, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Masato T Kanemaki
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), and Graduate Institute for Advanced Studies, SOKENDAI, Yata 1111, Mishima, Shizuoka, 411-8540, Japan
- Department of Biological Science, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Minoru Tanaka
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Tomomi Kiyomitsu
- Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan.
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Pal M, Altamirano-Pacheco L, Schauer T, Torres-Padilla ME. Reorganization of lamina-associated domains in early mouse embryos is regulated by RNA polymerase II activity. Genes Dev 2023; 37:901-912. [PMID: 37914351 PMCID: PMC10691468 DOI: 10.1101/gad.350799.123] [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: 05/15/2023] [Accepted: 10/12/2023] [Indexed: 11/03/2023]
Abstract
Fertilization in mammals is accompanied by an intense period of chromatin remodeling and major changes in nuclear organization. How the earliest events in embryogenesis, including zygotic genome activation (ZGA) during maternal-to-zygotic transition, influence such remodeling remains unknown. Here, we have investigated the establishment of nuclear architecture, focusing on the remodeling of lamina-associated domains (LADs) during this transition. We report that LADs reorganize gradually in two-cell embryos and that blocking ZGA leads to major changes in nuclear organization, including altered chromatin and genomic features of LADs and redistribution of H3K4me3 toward the nuclear lamina. Our data indicate that the rearrangement of LADs is an integral component of the maternal-to-zygotic transition and that transcription contributes to shaping nuclear organization at the beginning of mammalian development.
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Affiliation(s)
- Mrinmoy Pal
- Institute of Epigenetics and Stem Cells (IES), Helmholtz Zentrum München, D-81377 München, Germany
| | - Luis Altamirano-Pacheco
- Institute of Epigenetics and Stem Cells (IES), Helmholtz Zentrum München, D-81377 München, Germany
| | - Tamas Schauer
- Institute of Epigenetics and Stem Cells (IES), Helmholtz Zentrum München, D-81377 München, Germany
| | - Maria-Elena Torres-Padilla
- Institute of Epigenetics and Stem Cells (IES), Helmholtz Zentrum München, D-81377 München, Germany;
- Faculty of Biology, Ludwig-Maximilians Universität, D-81377 München, Germany
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Galitsyna A, Ulianov SV, Bykov NS, Veil M, Gao M, Perevoschikova K, Gelfand M, Razin SV, Mirny L, Onichtchouk D. Extrusion fountains are hallmarks of chromosome organization emerging upon zygotic genome activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.15.549120. [PMID: 37503128 PMCID: PMC10370019 DOI: 10.1101/2023.07.15.549120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
The first activation of gene expression during development (zygotic genome activation, ZGA) is accompanied by massive changes in chromosome organization. The connection between these two processes remains unknown. Using Hi-C for zebrafish embryos, we found that chromosome folding starts by establishing "fountains", novel elements of chromosome organization, emerging selectively at enhancers upon ZGA. Using polymer simulations, we demonstrate that fountains can emerge as sites of targeted cohesin loading and require two-sided, yet desynchronized, loop extrusion. Specific loss of fountains upon loss of pioneer transcription factors that drive ZGA reveals a causal connection between enhancer activity and fountain formation. Finally, we show that fountains emerge in early Medaka and Xenopus embryos; moreover, we found cohesin-dependent fountain pattern on enhancers of mouse embryonic stem cells. Taken together, fountains are the first enhancer-specific elements of chromosome organization; they constitute starting points of chromosome folding during early development, likely serving as sites of targeted cohesin loading.
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Affiliation(s)
- Aleksandra Galitsyna
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sergey V. Ulianov
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Nikolai S. Bykov
- Institute for Information Transmission Problems (the Kharkevich Institute), Russian Academy of Sciences, Moscow, 127051, Russia
- Centro Nacional de Análisis Genómico (CNAG), Baldiri Reixac 4, Barcelona, 08028 Spain
| | - Marina Veil
- Department of Developmental Biology, University of Freiburg, Freiburg, 79104, Germany
| | - Meijiang Gao
- Department of Developmental Biology, University of Freiburg, Freiburg, 79104, Germany
- Signalling Research Centres BIOSS and CIBSS, Freiburg, 79104, Germany
| | - Kristina Perevoschikova
- Faculty of Bioengineering and Bioinformatics, M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Mikhail Gelfand
- Institute for Information Transmission Problems (the Kharkevich Institute), Russian Academy of Sciences, Moscow, 127051, Russia
| | - Sergey V. Razin
- Institute of Gene Biology, Russian Academy of Sciences, 119334, Russia
- Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Leonid Mirny
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Daria Onichtchouk
- Department of Developmental Biology, University of Freiburg, Freiburg, 79104, Germany
- Signalling Research Centres BIOSS and CIBSS, Freiburg, 79104, Germany
- Koltzov Institute of Developmental Biology RAS, Moscow, 119991, Russia
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