1
|
Sran S, Ringland A, Bedrosian TA. Building the brain mosaic: an expanded view. Trends Genet 2024; 40:747-756. [PMID: 38853120 PMCID: PMC11387136 DOI: 10.1016/j.tig.2024.05.008] [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: 03/31/2024] [Revised: 05/20/2024] [Accepted: 05/21/2024] [Indexed: 06/11/2024]
Abstract
The complexity of the brain is closely tied to its nature as a genetic mosaic, wherein each cell is distinguished by a unique constellation of somatic variants that contribute to functional and phenotypic diversity. Postzygotic variation arising during neurogenesis is recognized as a key contributor to brain mosaicism; however, recent advances have broadened our understanding to include sources of neural genomic diversity that develop throughout the entire lifespan, from embryogenesis through aging. Moving beyond the traditional confines of neurodevelopment, in this review, we delve into the complex mechanisms that enable various origins of brain mosaicism.
Collapse
Affiliation(s)
- Sahibjot Sran
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Amanda Ringland
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Tracy A Bedrosian
- Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA.
| |
Collapse
|
2
|
DiPeso L, Pendyala S, Huang HZ, Fowler DM, Hatch EM. Image-based identification and isolation of micronucleated cells to dissect cellular consequences. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.05.04.539483. [PMID: 37205341 PMCID: PMC10187275 DOI: 10.1101/2023.05.04.539483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Recent advances in isolating cells based on visual phenotypes have transformed our ability to identify the mechanisms and consequences of complex traits. Micronucleus (MN) formation is a frequent outcome of genome instability, triggers extensive disease-associated changes in genome structure and signaling coincident with MN rupture, and is almost exclusively defined by visual analysis. Automated MN detection in microscopy images has proved extremely challenging, limiting unbiased discovery of the mechanisms and consequences of MN formation and rupture. In this study we describe two new MN segmentation modules: a rapid and precise model for classifying micronucleated cells and their rupture status (VCS MN), and a robust model for accurate MN segmentation (MNFinder) from a broad range of microscopy images. As a proof-of-concept, we define the transcriptome of non-transformed human cells with intact or ruptured MN after inducing chromosome missegregation by combining VCS MN with photoactivation-based cell isolation and RNASeq. Surprisingly, we find that neither MN formation nor rupture triggers a unique transcriptional response. Instead, transcriptional changes are correlated with increased aneuploidy in these cell classes. Our MN segmentation modules overcome a significant challenge to reproducible MN quantification, and, joined with visual cell sorting, enable the application of powerful functional genomics assays, including pooled CRISPR screens and time-resolved analyses of cellular and genetic consequences, to a wide-range of questions in MN biology.
Collapse
Affiliation(s)
- Lucian DiPeso
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Molecular & Cellular Biology, University of Washington, Seattle, WA, USA
| | | | - Heather Z. Huang
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | | | - Emily M. Hatch
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Human Biology Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| |
Collapse
|
3
|
Ono Y, Shirasawa H, Takahashi K, Goto M, Ono T, Sakaguchi T, Okabe M, Hirakawa T, Iwasawa T, Fujishima A, Sugawara T, Makino K, Miura H, Fukunaga N, Asada Y, Kumazawa Y, Terada Y. Shape of the first mitotic spindles impacts multinucleation in human embryos. Nat Commun 2024; 15:5381. [PMID: 38918406 PMCID: PMC11199590 DOI: 10.1038/s41467-024-49815-8] [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: 01/18/2024] [Accepted: 06/18/2024] [Indexed: 06/27/2024] Open
Abstract
During human embryonic development, early cleavage-stage embryos are more susceptible to errors. Studies have shown that many problems occur during the first mitosis, such as direct cleavage, chromosome segregation errors, and multinucleation. However, the mechanisms whereby these errors occur during the first mitosis in human embryos remain unknown. To clarify this aspect, in the present study, we image discarded living human two-pronuclear stage zygotes using fluorescent labeling and confocal microscopy without microinjection of DNA or mRNA and investigate the association between spindle shape and nuclear abnormality during the first mitosis. We observe that the first mitotic spindles vary, and low-aspect-ratio-shaped spindles tend to lead to the formation of multiple nuclei at the 2-cell stage. Moreover, we observe defocusing poles in many of the first mitotic spindles, which are strongly associated with multinucleation. Additionally, we show that differences in the positions of the centrosomes cause spindle abnormality in the first mitosis. Furthermore, many multinuclei are modified to form mononuclei after the second mitosis because the occurrence of pole defocusing is firmly reduced. Our study will contribute markedly to research on the occurrence of mitotic errors during the early cleavage of human embryos.
Collapse
Affiliation(s)
- Yuki Ono
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan.
| | - Hiromitsu Shirasawa
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Kazumasa Takahashi
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Mayumi Goto
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Takahiro Ono
- Department of Neurosurgery, Akita University Graduate School of Medicine, Akita, Japan
| | - Taichi Sakaguchi
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Motonari Okabe
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Takeo Hirakawa
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Takuya Iwasawa
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Akiko Fujishima
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Tae Sugawara
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Kenichi Makino
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Hiroshi Miura
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Noritaka Fukunaga
- Asada Institute for Reproductive Medicine, Asada Ladies Clinic, Nagoya, Aichi, Japan
| | - Yoshimasa Asada
- Asada Institute for Reproductive Medicine, Asada Ladies Clinic, Nagoya, Aichi, Japan
| | - Yukiyo Kumazawa
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| | - Yukihiro Terada
- Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
| |
Collapse
|
4
|
Kurumizaka M, Yao T, Tokoro M, Fukunaga N, Asada Y, Yamagata K. Effect of ovarian stimulation on developmental speed of preimplantation embryo in a mouse model. J Reprod Dev 2024; 70:160-168. [PMID: 38494726 PMCID: PMC11153123 DOI: 10.1262/jrd.2023-089] [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: 10/27/2023] [Accepted: 02/16/2024] [Indexed: 03/19/2024] Open
Abstract
Ovarian stimulation protocols are widely used to collect oocytes in assisted reproductive technologies (ARTs). Although the influence of ovarian stimulation on embryo quality has been described, this issue remains controversial. Here, we analyzed the influence of ovarian stimulation on developmental speed and chromosome segregation using live cell imaging. Female mice at the proestrus stage were separated by the appearance of the vagina as the non-stimulation (-) group, and other mice were administered pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) as the stimulation (+) groups. The cumulus-oocyte complexes from both groups were inseminated with sperm suspensions from the same male mice. Fertilization rates and developmental capacities were examined, and the developmental speed and frequency of chromosome segregation errors were measured by live-cell imaging using a Histone H2B-mCherry probe. The number of fertilized oocytes obtained was 1.4-fold more frequent in the stimulation (+) group. The developmental rate and chromosome stability did not differ between the groups. Image analysis showed that the mean speed of development in the stimulation (+) group was slightly higher than that in the non-stimulation (-) group. This increase in speed seemed to arise from the slight shortening of the 2- and 4-cell stages and third division lengths and consequent synchronization of cleavage timing in each embryo, not from the emergence of an extremely rapidly developing subpopulation of embryos. In conclusion, ovarian stimulation does not necessarily affect embryo quality but rather increases the chances of obtaining high-quality oocytes in mice.
Collapse
Affiliation(s)
- Mayuko Kurumizaka
- Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
- Present: Reproductive Medical Center, Yokohama City University Medical Center, Kanagawa 232-0024, Japan
| | - Tatsuma Yao
- Research and Development Center, Fuso Pharmaceutical Industries, Ltd., Osaka 536-8523, Japan
- Present: Faculty of Biology-Oriented Science and Technology (BOST), KINDAI University, Wakayama 649-6493, Japan
| | - Mikiko Tokoro
- Asada Institute for Reproductive Medicine, Asada Ladies Clinic, Aichi 486-0931, Japan
- Present: Faculty of Biology-Oriented Science and Technology (BOST), KINDAI University, Wakayama 649-6493, Japan
| | - Noritaka Fukunaga
- Asada Institute for Reproductive Medicine, Asada Ladies Clinic, Aichi 486-0931, Japan
| | - Yoshimasa Asada
- Asada Institute for Reproductive Medicine, Asada Ladies Clinic, Aichi 486-0931, Japan
| | - Kazuo Yamagata
- Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
- Present: Faculty of Biology-Oriented Science and Technology (BOST), KINDAI University, Wakayama 649-6493, Japan
| |
Collapse
|
5
|
Cai Q, Sahu R, Ueberschlag-Pitiot V, Souali-Crespo S, Charvet C, Silem I, Cottard F, Ye T, Taleb F, Metzger E, Schuele R, Billas IML, Laverny G, Metzger D, Duteil D. LSD1 inhibition circumvents glucocorticoid-induced muscle wasting of male mice. Nat Commun 2024; 15:3563. [PMID: 38670969 PMCID: PMC11053113 DOI: 10.1038/s41467-024-47846-9] [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: 06/09/2023] [Accepted: 04/15/2024] [Indexed: 04/28/2024] Open
Abstract
Synthetic glucocorticoids (GC), such as dexamethasone, are extensively used to treat chronic inflammation and autoimmune disorders. However, long-term treatments are limited by various side effects, including muscle atrophy. GC activities are mediated by the glucocorticoid receptor (GR), that regulates target gene expression in various tissues in association with cell-specific co-regulators. Here we show that GR and the lysine-specific demethylase 1 (LSD1) interact in myofibers of male mice, and that LSD1 connects GR-bound enhancers with NRF1-associated promoters to stimulate target gene expression. In addition, we unravel that LSD1 demethylase activity is required for triggering starvation- and dexamethasone-induced skeletal muscle proteolysis in collaboration with GR. Importantly, inhibition of LSD1 circumvents muscle wasting induced by pharmacological levels of dexamethasone, without affecting their anti-inflammatory activities. Thus, our findings provide mechanistic insights into the muscle-specific GC activities, and highlight the therapeutic potential of targeting GR co-regulators to limit corticotherapy-induced side effects.
Collapse
Affiliation(s)
- Qingshuang Cai
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Rajesh Sahu
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | | | - Sirine Souali-Crespo
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Céline Charvet
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Ilyes Silem
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Félicie Cottard
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Tao Ye
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Fatima Taleb
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Eric Metzger
- Klinik für Urologie und Zentrale Klinische Forschung, Klinikum der Albert-Ludwigs-Universität Freiburg, D-79106, Freiburg, Germany
| | - Roland Schuele
- Klinik für Urologie und Zentrale Klinische Forschung, Klinikum der Albert-Ludwigs-Universität Freiburg, D-79106, Freiburg, Germany
| | - Isabelle M L Billas
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Gilles Laverny
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Daniel Metzger
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France
| | - Delphine Duteil
- Université de Strasbourg, CNRS, Inserm, IGBMC UMR 7104- UMR-S 1258, F-67400, Illkirch, France.
| |
Collapse
|
6
|
Messer CL, Fox DT. Broken chromosomes heading into mitosis: More than one way to patch a flat tire. J Cell Biol 2024; 223:e202401085. [PMID: 38477879 PMCID: PMC10937182 DOI: 10.1083/jcb.202401085] [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: 01/17/2024] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 03/14/2024] Open
Abstract
A cell dealing with a broken chromosome in mitosis is like a driver dealing with a flat tire on the highway: damage repair must occur under non-ideal circumstances. Mitotic chromosome breaks encounter problems related to structures called micronuclei. These aberrant nuclei are linked to cell death, mutagenesis, and cancer. In the last few years, a flurry of studies illuminated two mechanisms that prevent mitotic problems related to micronuclei. One mechanism prevents micronuclei from forming during mitosis and involves DNA Polymerase Theta, a DNA repair regulator that patches up broken mitotic chromosomes. A second mechanism is activated after micronuclei form and then rupture, and involves CIP2A and TOPBP1 proteins, which patch micronuclear fragments to promote their subsequent mitotic segregation. Here, we review recent progress in this field of mitotic DNA damage and discuss why multiple mechanisms exist. Future studies in this exciting area will reveal new DNA break responses and inform therapeutic strategies.
Collapse
Affiliation(s)
- C. Luke Messer
- Department of Biology, St. Bonaventure University, St. Bonaventure, NY, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Donald T. Fox
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
- Duke Regeneration Center, Duke University Medical Center, Durham, NC, USA
- Duke Cancer Institute, Duke University Medical Center, Durham, NC, USA
| |
Collapse
|
7
|
Paim LMG, Lopez-Jauregui AA, McAlear TS, Bechstedt S. The spindle protein CKAP2 regulates microtubule dynamics and ensures faithful chromosome segregation. Proc Natl Acad Sci U S A 2024; 121:e2318782121. [PMID: 38381793 PMCID: PMC10907244 DOI: 10.1073/pnas.2318782121] [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: 11/07/2023] [Accepted: 12/28/2023] [Indexed: 02/23/2024] Open
Abstract
Regulation of microtubule dynamics by microtubule-associated proteins (MAPs) is essential for mitotic spindle assembly and chromosome segregation. Altered microtubule dynamics, particularly increased microtubule growth rates, were found to be a contributing factor for the development of chromosomal instability, which potentiates tumorigenesis. The MAP XMAP215/CKAP5 is the only known microtubule growth factor, and whether other MAPs regulate microtubule growth in cells is unclear. Our recent in vitro reconstitution experiments have demonstrated that Cytoskeleton-Associated Protein 2 (CKAP2) increases microtubule nucleation and growth rates, and here, we find that CKAP2 is also an essential microtubule growth factor in cells. By applying CRISPR-Cas9 knock-in and knock-out (KO) as well as microtubule plus-end tracking live cell imaging, we show that CKAP2 is a mitotic spindle protein that ensures faithful chromosome segregation by regulating microtubule growth. Live cell imaging of endogenously labeled CKAP2 showed that it localizes to the spindle during mitosis and rapidly shifts its localization to the chromatin upon mitotic exit before being degraded. Cells lacking CKAP2 display reduced microtubule growth rates and an increased proportion of chromosome segregation errors and aneuploidy that may be a result of an accumulation of kinetochore-microtubule misattachments. Microtubule growth rates and chromosome segregation fidelity can be rescued upon ectopic CKAP2 expression in KO cells, revealing a direct link between CKAP2 expression and microtubule dynamics. Our results unveil a role of CKAP2 in regulating microtubule growth in cells and provide a mechanistic explanation for the oncogenic potential of CKAP2 misregulation.
Collapse
Affiliation(s)
- Lia Mara Gomes Paim
- Department of Anatomy and Cell Biology, McGill University, Montréal, QCH3A 0C7, Canada
| | | | - Thomas S. McAlear
- Department of Anatomy and Cell Biology, McGill University, Montréal, QCH3A 0C7, Canada
| | - Susanne Bechstedt
- Department of Anatomy and Cell Biology, McGill University, Montréal, QCH3A 0C7, Canada
| |
Collapse
|
8
|
Horakova A, Konecna M, Anger M. Chromosome Division in Early Embryos-Is Everything under Control? And Is the Cell Size Important? Int J Mol Sci 2024; 25:2101. [PMID: 38396778 PMCID: PMC10889803 DOI: 10.3390/ijms25042101] [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: 12/22/2023] [Revised: 02/02/2024] [Accepted: 02/06/2024] [Indexed: 02/25/2024] Open
Abstract
Chromosome segregation in female germ cells and early embryonic blastomeres is known to be highly prone to errors. The resulting aneuploidy is therefore the most frequent cause of termination of early development and embryo loss in mammals. And in specific cases, when the aneuploidy is actually compatible with embryonic and fetal development, it leads to severe developmental disorders. The main surveillance mechanism, which is essential for the fidelity of chromosome segregation, is the Spindle Assembly Checkpoint (SAC). And although all eukaryotic cells carry genes required for SAC, it is not clear whether this pathway is active in all cell types, including blastomeres of early embryos. In this review, we will summarize and discuss the recent progress in our understanding of the mechanisms controlling chromosome segregation and how they might work in embryos and mammalian embryos in particular. Our conclusion from the current literature is that the early mammalian embryos show limited capabilities to react to chromosome segregation defects, which might, at least partially, explain the widespread problem of aneuploidy during the early development in mammals.
Collapse
Affiliation(s)
- Adela Horakova
- Department of Genetics and Reproductive Biotechnologies, Veterinary Research Institute, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Science, 277 21 Libechov, Czech Republic
- Faculty of Science, Masaryk University, 602 00 Brno, Czech Republic
| | - Marketa Konecna
- Department of Genetics and Reproductive Biotechnologies, Veterinary Research Institute, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Science, 277 21 Libechov, Czech Republic
- Faculty of Science, Masaryk University, 602 00 Brno, Czech Republic
| | - Martin Anger
- Department of Genetics and Reproductive Biotechnologies, Veterinary Research Institute, 621 00 Brno, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Science, 277 21 Libechov, Czech Republic
| |
Collapse
|
9
|
Budrewicz J, Chavez SL. Insights into embryonic chromosomal instability: mechanisms of DNA elimination during mammalian preimplantation development. Front Cell Dev Biol 2024; 12:1344092. [PMID: 38374891 PMCID: PMC10875028 DOI: 10.3389/fcell.2024.1344092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Accepted: 01/15/2024] [Indexed: 02/21/2024] Open
Abstract
Mammalian preimplantation embryos often contend with aneuploidy that arose either by the inheritance of meiotic errors from the gametes, or from mitotic mis-segregation events that occurred following fertilization. Regardless of the origin, mis-segregated chromosomes become encapsulated in micronuclei (MN) that are spatially isolated from the main nucleus. Much of our knowledge of MN formation comes from dividing somatic cells during tumorigenesis, but the error-prone cleavage-stage of early embryogenesis is fundamentally different. One unique aspect is that cellular fragmentation (CF), whereby small subcellular bodies pinch off embryonic blastomeres, is frequently observed. CF has been detected in both in vitro and in vivo-derived embryos and likely represents a response to chromosome mis-segregation since it only appears after MN formation. There are multiple fates for MN, including sequestration into CFs, but the molecular mechanism(s) by which this occurs remains unclear. Due to nuclear envelope rupture, the chromosomal material contained within MN and CFs becomes susceptible to double stranded-DNA breaks. Despite this damage, embryos may still progress to the blastocyst stage and exclude chromosome-containing CFs, as well as non-dividing aneuploid blastomeres, from participating in further development. Whether these are attempts to rectify MN formation or eliminate embryos with poor implantation potential is unknown and this review will discuss the potential implications of DNA removal by CF/blastomere exclusion. We will also extrapolate what is known about the intracellular pathways mediating MN formation and rupture in somatic cells to preimplantation embryogenesis and how nuclear budding and DNA release into the cytoplasm may impact overall development.
Collapse
Affiliation(s)
- Jacqueline Budrewicz
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, OR, United States
- Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Beaverton, OR, United States
| | - Shawn L. Chavez
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, OR, United States
- Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Beaverton, OR, United States
- Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR, United States
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR, United States
| |
Collapse
|
10
|
Zierhut C. p53 and Innate Immune Signaling in Development and Cancer: Insights from a Hematologic Model of Genome Instability. Cancer Res 2023; 83:2807-2808. [PMID: 37655431 DOI: 10.1158/0008-5472.can-23-1855] [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: 06/21/2023] [Accepted: 06/23/2023] [Indexed: 09/02/2023]
Abstract
Genome instability due to the loss of DNA repair factors can drive developmental defects, autoinflammatory disease, and cancer. Two major signaling pathways are activated by genome instability-DNA damage checkpoint signaling, leading to p53 activation, and innate immunity, largely driven by the DNA sensor cGAS. Like p53, cGAS is thought to drive cell death and senescence during genotoxic stress in addition to its canonical inflammatory functions, but its role during cellular differentiation and carcinogenesis is poorly understood. Furthermore, it is heavily debated whether the cGAS pathway primarily has tumor-suppressive or oncogenic functions. A study in this issue of Cancer Research used a hematopoietic lineage-specific knockout of the ribonucleotide repair gene Rnaseh2b to introduce genotoxic stress, resulting in severe hematopoiesis defects and increased incidence of hematologic cancers. These two effects were driven by and antagonized by p53, respectively. Surprisingly, despite increased innate immune signaling, the cGAS pathway did not seem to play a role in either process. These findings suggest that innate immune responses to genotoxic stress may be more subtle and context-specific than appreciated, indicating that a more detailed understanding of pathway activation and signaling consequences is needed. See related article by Dressel et al., p. 2858.
Collapse
Affiliation(s)
- Christian Zierhut
- Division of Cancer Biology, Institute of Cancer Research, London, United Kingdom
| |
Collapse
|
11
|
Domingo-Muelas A, Skory RM, Moverley AA, Ardestani G, Pomp O, Rubio C, Tetlak P, Hernandez B, Rhon-Calderon EA, Navarro-Sánchez L, García-Pascual CM, Bissiere S, Bartolomei MS, Sakkas D, Simón C, Plachta N. Human embryo live imaging reveals nuclear DNA shedding during blastocyst expansion and biopsy. Cell 2023; 186:3166-3181.e18. [PMID: 37413989 PMCID: PMC11170958 DOI: 10.1016/j.cell.2023.06.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 04/05/2023] [Accepted: 06/05/2023] [Indexed: 07/08/2023]
Abstract
Proper preimplantation development is essential to assemble a blastocyst capable of implantation. Live imaging has uncovered major events driving early development in mouse embryos; yet, studies in humans have been limited by restrictions on genetic manipulation and lack of imaging approaches. We have overcome this barrier by combining fluorescent dyes with live imaging to reveal the dynamics of chromosome segregation, compaction, polarization, blastocyst formation, and hatching in the human embryo. We also show that blastocyst expansion mechanically constrains trophectoderm cells, causing nuclear budding and DNA shedding into the cytoplasm. Furthermore, cells with lower perinuclear keratin levels are more prone to undergo DNA loss. Moreover, applying trophectoderm biopsy, a mechanical procedure performed clinically for genetic testing, increases DNA shedding. Thus, our work reveals distinct processes underlying human development compared with mouse and suggests that aneuploidies in human embryos may not only originate from chromosome segregation errors during mitosis but also from nuclear DNA shedding.
Collapse
Affiliation(s)
- Ana Domingo-Muelas
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Igenomix Foundation and Carlos Simon Foundation, Spain
| | - Robin M Skory
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Adam A Moverley
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; University College London, London WC1E 6BT, UK
| | | | - Oz Pomp
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Piotr Tetlak
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Blake Hernandez
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Eric A Rhon-Calderon
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | - Stephanie Bissiere
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Marisa S Bartolomei
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Carlos Simón
- Igenomix Foundation and Carlos Simon Foundation, Spain; Department of Pediatrics Obstetrics & Gynecology, University of Valencia, Valencia 46010, Spain; INCLIVA Health Research Institute, Valencia 46010, Spain; Department of Obstetrics and Gynecology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
| | - Nicolas Plachta
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| |
Collapse
|
12
|
Al Jord A, Verlhac MH. Dyes illuminate live human embryogenesis. Cell 2023; 186:3143-3145. [PMID: 37478818 DOI: 10.1016/j.cell.2023.06.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 06/15/2023] [Accepted: 06/15/2023] [Indexed: 07/23/2023]
Abstract
Assisted reproduction is on the rise globally. Cell morphology is commonly used for embryo selection, but the cell biology of early preimplantation development remains poorly understood. In this issue of Cell, Domingo-Muelas et al. reveal novel features of human embryos with critical implications for preimplantation genetic testing.
Collapse
Affiliation(s)
- Adel Al Jord
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France.
| | - Marie-Hélène Verlhac
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France.
| |
Collapse
|
13
|
Cimini D. Twenty years of merotelic kinetochore attachments: a historical perspective. Chromosome Res 2023; 31:18. [PMID: 37466740 PMCID: PMC10411636 DOI: 10.1007/s10577-023-09727-7] [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: 05/01/2023] [Revised: 06/20/2023] [Accepted: 07/08/2023] [Indexed: 07/20/2023]
Abstract
Micronuclei, small DNA-containing structures separate from the main nucleus, were used for decades as an indicator of genotoxic damage. Micronuclei containing whole chromosomes were considered a biomarker of aneuploidy and were believed to form, upon mitotic exit, from chromosomes that lagged behind in anaphase as all other chromosomes segregated to the poles of the mitotic spindle. However, the mechanism responsible for inducing anaphase lagging chromosomes remained unknown until just over twenty years ago. Here, I summarize what preceded and what followed this discovery, highlighting some of the open questions and opportunities for future investigation.
Collapse
Affiliation(s)
- Daniela Cimini
- Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, 24061, USA.
| |
Collapse
|
14
|
Sanders KD, Griffin DK, Martell HJ, Blazek J, Large M, Gordon T. What proportion of embryos should be considered for transfer following a mosaic diagnosis? A study of 115 clinics from a central diagnostic laboratory. J Assist Reprod Genet 2023; 40:653-664. [PMID: 36708429 PMCID: PMC10033805 DOI: 10.1007/s10815-022-02678-8] [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: 11/01/2021] [Accepted: 12/02/2022] [Indexed: 01/29/2023] Open
Abstract
PURPOSE The aim of this study is to identify what proportion of mosaic embryo diagnoses should be considered for transfer, and thereby assess the impact on patient cases. METHODS We categorised mosaic embryos into 3 groups; high, medium and low priority for transfer based on the percentage of biopsy sample being aneuploid and the chromosomes involved. The categories were applied to those patients that had no euploid embryo diagnoses but 1 or more mosaic embryos identified as mosaic available after PGT-A. RESULTS In total, 6614 PGT-A cases from 115 clinics and a single diagnostic laboratory were reviewed. Further, 1384 [20.9%] cases only had aneuploid embryos, 4538 [68.6%] cases had one or more euploid embryos and 692 [10.5%] cases had no euploid and one or more mosaic embryo. The mosaic embryos in the no euploid, one or more mosaic group, when reviewed using priorities, resulted in: 111 [1.7%] of cases having at least one high priority mosaic available. 184 [2.8%] of cases having no high priority but at least one medium priority mosaic available. 397 [6.0%] of cases only having low priority mosaic embryos available. CONCLUSION Based on this data, embryos identified as mosaic will only be considered for transfer in the first instance for around 4.5% (when taking high and medium priority and excluding low priority cases) of all PGT-A cases.
Collapse
Affiliation(s)
| | - Darren K Griffin
- School of Biosciences, University of Kent, Canterbury, CT2 7NJ, UK
| | - Henry J Martell
- School of Biosciences, University of Kent, Canterbury, CT2 7NJ, UK
| | | | | | | |
Collapse
|
15
|
Reimann H, Stopper H, Hintzsche H. Fate of micronuclei and micronucleated cells after treatment of HeLa cells with different genotoxic agents. Arch Toxicol 2023; 97:875-889. [PMID: 36564592 PMCID: PMC9968706 DOI: 10.1007/s00204-022-03433-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022]
Abstract
Although micronuclei are well-known biomarkers of genotoxic damage, the biological consequences of micronucleus induction are only poorly understood. To further elucidate these consequences, HeLa cells stably expressing histone 2B coupled with green fluorescent protein were used for long-term live cell imaging to investigate the fate of micronuclei and micronucleated cells after treatment of cells with various genotoxic agents (doxorubicin (20, 30 and nM), tert-butyl hydroperoxide (tBHP, 50, 100 and 150 µM), radiation (0.5, 1 and 2 Gy), methyl methanesulfonate (MMS, 20, 25 and 30 µg/ml) and vinblastine (1, 2 and 3 nM)). Most micronuclei persist for multiple cell cycles or reincorporate while micronucleated cells were more prone to cell death, senescence and fatal mitotic errors compared to non-micronucleated cells, which is consistent with previous studies using etoposide. No clear substance-related effects on the fate of micronuclei and micronucleated cells were observed. To further investigate the fate of micronuclei, extrusion of micronuclei was studied with treatments reported as inducing the extrusion of micronuclei. Since extrusion was not observed in HeLa cells, the relevance of extrusion of micronuclei remains unclear. In addition, degradation of micronuclei was analysed via immunostaining of γH2AX, which demonstrated a high level of DNA damage in micronuclei compared to the main nuclei. Furthermore, transduction with two reporter genes (LC3B-dsRed and LaminB1-dsRed) was conducted followed by long-term live cell imaging. While autophagy marker LC3B was not associated with micronuclei, Lamin B1 was found in approximately 50% of all micronuclei. While degradation of micronuclei was not observed to be a frequent fate of micronuclei, the results show impaired stability of DNA and micronuclear envelope indicating rupture of micronuclei as a pre-step to chromothripsis.
Collapse
Affiliation(s)
- Hauke Reimann
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
- Bavarian Health and Food Safety Authority, Erlangen, Germany
| | - Helga Stopper
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
| | | |
Collapse
|
16
|
Micronucleus formation during early cleavage division is a potential hallmark of preimplantation embryonic loss in cattle. Biochem Biophys Res Commun 2022; 617:25-32. [PMID: 35689839 DOI: 10.1016/j.bbrc.2022.05.075] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Accepted: 05/21/2022] [Indexed: 11/22/2022]
Abstract
In assisted reproductive technology (ART)-derived embryos of non-rodent mammals, including humans and cattle, chromosome segregation errors are highly likely to occur during early cleavage division, resulting in aneuploidy, including mosaicism. However, the relationship between chromosomal segregation errors during early cleavage and subsequent embryonic development has not been detailed in these mammals. In the present study, we developed non-invasive live-cell imaging of chromosome segregation dynamics using a histone H2B-mCherry mRNA probe in bovine preimplantation embryos. Chromosome segregation errors in early cleavage affected blastocyst formation. Especially, embryos that underwent abnormal chromosome segregation (ACS) with multiple or large micronucleus formation rarely developed into blastocysts. Embryos with the severe ACS had prolonged cell cycle duration. After transfer of blastocysts with live-cell imaging of chromosome segregation to ten cows, six became pregnant and four of them gave full-term offspring. Interestingly, two of them were derived from blastocysts with ACS. Hence, chromosomal segregation errors with micronucleus formation during early cleavage can be a fatal hallmark of preimplantation embryogenesis in cattle. This technique has shown potential for understanding the relationship between chromosome segregation error and subsequent embryo development, and for selecting viable ART-derived embryos for medical and livestock production.
Collapse
|
17
|
Wang J, Thomas HR, Chen Y, Percival SM, Waldrep SC, Ramaker RC, Thompson RG, Cooper SJ, Chong Z, Parant JM. Reduced sister chromatid cohesion acts as a tumor penetrance modifier. PLoS Genet 2022; 18:e1010341. [PMID: 35994499 PMCID: PMC9436123 DOI: 10.1371/journal.pgen.1010341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 09/01/2022] [Accepted: 07/14/2022] [Indexed: 11/23/2022] Open
Abstract
Sister chromatid cohesion (SCC) is an important process in chromosome segregation. ESCO2 is essential for establishment of SCC and is often deleted/altered in human cancers. We demonstrate that esco2 haploinsufficiency results in reduced SCC and accelerates the timing of tumor onset in both zebrafish and mouse p53 heterozygous null models, but not in p53 homozygous mutant or wild-type animals. These data indicate that esco2 haploinsufficiency accelerates tumor onset in a loss of heterozygosity (LOH) sensitive background. Analysis of The Cancer Genome Atlas (TCGA) confirmed ESCO2 deficient tumors have elevated number of LOH events throughout the genome. Further, we demonstrated heterozygous loss of sgo1, important in maintaining SCC, also results in reduced SCC and accelerated tumor formation in a p53 heterozygous background. Surprisingly, while we did observe elevated levels of chromosome missegregation and micronuclei formation in esco2 heterozygous mutant animals, this chromosomal instability did not contribute to the accelerated tumor onset in a p53 heterozygous background. Interestingly, SCC also plays a role in homologous recombination, and we did observe elevated levels of mitotic recombination derived p53 LOH in tumors from esco2 haploinsufficient animals; as well as elevated levels of mitotic recombination throughout the genome of human ESCO2 deficient tumors. Together these data suggest that reduced SCC contributes to accelerated tumor penetrance through elevated mitotic recombination. Tumorigenesis often involves the inactivation of tumor suppressor genes. This often encompasses an inactivation mutation in one allele and loss of the other wild-type allele, referred to as loss of heterozygosity (LOH). The rate at which the cells lose the wild-type allele can influence the timing of tumor onset, and therefore an indicator of a patient’s risk of cancer. Factors that influence this process could be used as a predictive indicator of cancer risk, however these factors are still unclear. We demonstrate that partial impairment of sister chromatid cohesion (SCC), a fundamental component of the chromosome segregation in mitosis and homologous recombination repair, enhanced tumorigenesis. Our data suggest this is through elevated levels of mitotic recombination derived p53 LOH. This study emphasizes the importance of understanding how impaired SCC, mitotic recombination rates, and LOH rates influence cancer risk.
Collapse
Affiliation(s)
- Jun Wang
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
| | - Holly R. Thomas
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
| | - Yu Chen
- Department of Genetics, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
- Informatics Institute, University of Alabama at Birmingham Heersink School of Medicine, Alabama, United States of America
| | - Stefanie M. Percival
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
| | - Stephanie C. Waldrep
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
| | - Ryne C. Ramaker
- Hudson Alpha Institute for Biotechnology, Huntsville, Alabama, United States of America
| | - Robert G. Thompson
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
| | - Sara J. Cooper
- Hudson Alpha Institute for Biotechnology, Huntsville, Alabama, United States of America
| | - Zechen Chong
- Department of Genetics, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
- Informatics Institute, University of Alabama at Birmingham Heersink School of Medicine, Alabama, United States of America
| | - John M. Parant
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States of America
- * E-mail:
| |
Collapse
|
18
|
Wang Y, Oda S, Suzuki MG, Mitani H, Aoki F. Cell cycle-dependent radiosensitivity in mouse zygotes. DNA Repair (Amst) 2022; 117:103370. [PMID: 35863142 DOI: 10.1016/j.dnarep.2022.103370] [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: 03/14/2022] [Revised: 06/22/2022] [Accepted: 07/05/2022] [Indexed: 11/18/2022]
Abstract
Mammalian zygotes are hypersensitive to radiation exposure compared with later-stage embryos and somatic cells, which may be due to an unusual DNA damage response (DDR). DNA damage checkpoints are an essential part of the DDR, allowing for faithful replication of cells. Although the DDR and radiosensitivity of somatic cells are dependent on the cell cycle phase, it remains largely unclear how the irradiation of zygotes at different phases affects cell cycle progression and preimplantation development. Here, mouse zygotes were irradiated with 10 Gy γ-rays at all four cell cycle phases. DNA damage checkpoints were activated by γ-irradiation at the G2 phase, but not at the G1, S, and M phases. The absence of DNA damage checkpoints at the G1 and M phases seems to be due to the low abundance of phosphorylated CHK2, which plays a key role in checkpoint activation in response to ionizing radiation. The cause of the inoperative S phase checkpoint may lie downstream of CHK2 activation. The inactive DNA damage checkpoints at the G1 and S phases contributed to micronucleus formation in the subsequent 2-cell stage, whereas irradiation at the M phase led to the highest incidence of chromatin bridges. The low developmental rates of embryos irradiated at the G1, S, and M phases suggest that embryos with these two types of chromatin abnormalities are prone to developmental failure. Taken together, these results suggest that the radiosensitivity of zygotes can be ascribed to a defective DDR at the G1, S, and M phases.
Collapse
Affiliation(s)
- Yuan Wang
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Shoji Oda
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Masataka G Suzuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Hiroshi Mitani
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Fugaku Aoki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.
| |
Collapse
|
19
|
Allais A, FitzHarris G. Absence of a robust mitotic timer mechanism in early preimplantation mouse embryos leads to chromosome instability. Development 2022; 149:275859. [DOI: 10.1242/dev.200391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 05/12/2022] [Indexed: 01/07/2023]
Abstract
ABSTRACT
Preimplantation embryos often consist of a combination of euploid and aneuploid cells, suggesting that safeguards preventing the generation and propagation of aneuploid cells in somatic cells might be deficient in embryos. In somatic cells, a mitotic timer mechanism has been described, in which even a small increase in the duration of M phase can cause a cell cycle arrest in the subsequent interphase, preventing further propagation of cells that have undergone a potentially hazardously long M phase. Here, we report that cell divisions in the mouse embryo and embryonic development continue even after a mitotic prolongation of several hours. However, similar M-phase extensions caused cohesion fatigue, resulting in prematurely separated sister chromatids and the production of micronuclei. Only extreme prolongation of M phase caused a subsequent interphase arrest, through a mechanism involving DNA damage. Our data suggest that the simultaneous absence of a robust mitotic timer and susceptibility of the embryo to cohesion fatigue could contribute to chromosome instability in mammalian embryos.
This article has an associated ‘The people behind the papers’ interview.
Collapse
Affiliation(s)
- Adélaïde Allais
- Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM) 1 , H2X 0A9 Montréal, Québec , Canada
| | - Greg FitzHarris
- Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM) 1 , H2X 0A9 Montréal, Québec , Canada
- Université de Montréal 2 Department of OBGYN, and Department of Pathology and Cell Biology , , H3T 1C5 Montréal, Québec , Canada
| |
Collapse
|
20
|
Miskel D, Poirier M, Beunink L, Rings F, Held E, Tholen E, Tesfaye D, Schellander K, Salilew-Wondim D, Blaschka C, Große-Brinkhaus C, Brenig B, Hoelker M. The cell cycle stage of bovine zygotes electroporated with CRISPR/Cas9-RNP affects frequency of Loss-of-heterozygosity editing events. Sci Rep 2022; 12:10793. [PMID: 35750764 PMCID: PMC9232522 DOI: 10.1038/s41598-022-14699-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 06/10/2022] [Indexed: 12/14/2022] Open
Abstract
At the embryonic level, CRISPR technologies have been used to edit genomes reliably and efficiently in various mammalian models, with Ribonucleoprotein (RNP) electroporation potentially representing a superior delivery method into mammalian zygotes. However, detailed insights of the interactions between varying technical settings as well as the time point of electroporation in a bovine zygote's cell cycle on developmental metrics and the frequency and type of editing events are largely unknown. The present study uncovers that increasing pulse lengths result in higher Full Edit rates, with Mosaicism in Full-Edit embryos being significantly affected by adjusting RNP-electroporation relative to zygote cell cycle. A considerable proportion of Full Edit embryos demonstrated loss-of-heterozygosity after RNP-electroporation prior to S-phase. Some of these loss-of-heterozygosity events are a consequence of chromosomal disruptions along large sections of the target chromosomes making it necessary to check for their presence prior use of this technique in animal breeding. One out of 2 of these loss-of-heterozygosity events, however, was not associated with loss of an entire chromosome or chromosomal sections. Whether analysed loss-of-heterozygosity in these cases, however, was a false negative result due to loss of PCR primer sequences after INDEL formation at the target side or indeed due to interhomolog recombination needs to be clarified in follow up studies since the latter would for sure offer attractive options for future breeding schedules.
Collapse
Affiliation(s)
- Dennis Miskel
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Mikhael Poirier
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Luisa Beunink
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Franca Rings
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Eva Held
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Ernst Tholen
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Dawit Tesfaye
- Department of Biomedical Sciences, Animal Reproduction and Biotechnology Laboratory, Colorado State University, 3105 Rampart Rd, Fort Collins, CO, 80521, USA
| | - Karl Schellander
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Dessie Salilew-Wondim
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Carina Blaschka
- Department of Animal Science, Biotechnology and Reproduction of Farm Animals, Georg August University Goettingen, Burckhardtweg 2, 37077, Goettingen, Germany
| | - Christine Große-Brinkhaus
- Institute of Animal Sciences, Animal Breeding, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
| | - Bertram Brenig
- Department of Molecular Biology of Livestock, Institute of Veterinary Medicine, Georg August University Goettingen, Burckhardtweg 2, 37077, Goettingen, Germany
| | - Michael Hoelker
- Department of Animal Science, Biotechnology and Reproduction of Farm Animals, Georg August University Goettingen, Burckhardtweg 2, 37077, Goettingen, Germany.
| |
Collapse
|
21
|
Vertegaal ACO. Signalling mechanisms and cellular functions of SUMO. Nat Rev Mol Cell Biol 2022; 23:715-731. [PMID: 35750927 DOI: 10.1038/s41580-022-00500-y] [Citation(s) in RCA: 115] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/23/2022] [Indexed: 12/22/2022]
Abstract
Sumoylation is an essential post-translational modification that is catalysed by a small number of modifying enzymes but regulates thousands of target proteins in a dynamic manner. Small ubiquitin-like modifiers (SUMOs) can be attached to target proteins as one or more monomers or in the form of polymers of different types. Non-covalent readers recognize SUMO-modified proteins via SUMO interaction motifs. SUMO simultaneously modifies groups of functionally related proteins to regulate predominantly nuclear processes, including gene expression, the DNA damage response, RNA processing, cell cycle progression and proteostasis. Recent progress has increased our understanding of the cellular and pathophysiological roles of SUMO modifications, extending their functions to the regulation of immunity, pluripotency and nuclear body assembly in response to oxidative stress, which partly occurs through the recently characterized mechanism of liquid-liquid phase separation. Such progress in understanding the roles and regulation of sumoylation opens new avenues for the targeting of SUMO to treat disease, and indeed the first drug blocking sumoylation is currently under investigation in clinical trials as a possible anticancer agent.
Collapse
Affiliation(s)
- Alfred C O Vertegaal
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands.
| |
Collapse
|
22
|
Regin M, Spits C, Sermon K. On the origins and fate of chromosomal abnormalities in human preimplantation embryos: an unsolved riddle. Mol Hum Reprod 2022; 28:6566308. [DOI: 10.1093/molehr/gaac011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/30/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
About 8 out of 10 human embryos obtained in vitro harbour chromosomal abnormalities of either meiotic or mitotic origin. Abnormalities of mitotic origin lead to chromosomal mosaicism, a phenomenon which has sparked much debate lately as it confounds results obtained through preimplantation genetic testing for aneuploidy (PGT-A). PGT-A in itself is still highly debated, not only on the modalities of its execution, but also on whether it should be offered to patients at all.
We will focus on post-zygotic chromosomal abnormalities leading to mosaicism. First, we will summarize what is known of the rates of chromosomal abnormalities at different developmental stages. Next, based on the current understanding of the origin and cellular consequences of chromosomal abnormalities, which is largely based on studies on cancer cells and model organisms, we will offer a number of hypotheses on which mechanisms may be at work in early human development. Finally, and very briefly, we will touch upon the impact our current knowledge has on the practice of PGT-A. What is the level of abnormal cells that an embryo can tolerate before it loses its potential for full development? And is blastocyst biopsy as harmless as it seems?
Collapse
Affiliation(s)
- Marius Regin
- Research group Reproduction and Genetics, Vrije Universiteit Brussel, Brussels, 1090, Belgium
| | - Claudia Spits
- Research group Reproduction and Genetics, Vrije Universiteit Brussel, Brussels, 1090, Belgium
| | - Karen Sermon
- Research group Reproduction and Genetics, Vrije Universiteit Brussel, Brussels, 1090, Belgium
| |
Collapse
|
23
|
Zhang CZ, Pellman D. Cancer Genomic Rearrangements and Copy Number Alterations from Errors in Cell Division. ANNUAL REVIEW OF CANCER BIOLOGY 2022. [DOI: 10.1146/annurev-cancerbio-070620-094029] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Analysis of cancer genomes has shown that a large fraction of chromosomal changes originate from catastrophic events including whole-genome duplication, chromothripsis, breakage-fusion-bridge cycles, and chromoplexy. Through sophisticated computational analysis of cancer genomes and experimental recapitulation of these catastrophic alterations, we have gained significant insights into the origin, mechanism, and evolutionary dynamics of cancer genome complexity. In this review, we summarize this progress and survey the major unresolved questions, with particular emphasis on the relative contributions of chromosome fragmentation and DNA replication errors to complex chromosomal alterations.
Collapse
Affiliation(s)
- Cheng-Zhong Zhang
- Department of Data Science, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Department of Biomedical Informatics, Blavatnik Institute of Harvard Medical School, Boston, Massachusetts, USA
- Cancer Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - David Pellman
- Cancer Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Department of Cell Biology, Blavatnik Institute of Harvard Medical School, Boston, Massachusetts, USA
| |
Collapse
|
24
|
West JD, Everett CA. Preimplantation chromosomal mosaics, chimaeras and confined placental mosaicism. REPRODUCTION AND FERTILITY 2022; 3:R66-R90. [PMID: 35514539 PMCID: PMC9066951 DOI: 10.1530/raf-21-0095] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 04/05/2022] [Indexed: 02/06/2023] Open
Abstract
Some human preimplantation embryos are chromosomally mosaic. For technical reasons, estimates of the overall frequency vary widely from <15 to >90% and the true frequency remains unknown. Aneuploid/diploid and aneuploid/aneuploid mosaics typically arise during early cleavage stages before the embryonic genome is fully activated and when cell cycle checkpoints are not operating normally. Other mosaics include chaotic aneuploid mosaics and mixoploids, some of which arise by abnormal chromosome segregation at the first cleavage division. Chimaeras are similar to mosaics, in having two genetically distinct cell populations, but they arise from more than one zygote and occur less often. After implantation, the frequency of mosaic embryos declines to about 2% and most are trisomic/diploid mosaics, with trisomic cells confined to the placenta. Thus, few babies are born with chromosomal mosaicism. This review discusses the origin of different types of chromosomal mosaics and chimaeras; their fate and the relationship between preimplantation chromosomal mosaicism and confined placental mosaicism in human conceptuses and animal models. Abnormal cells in mosaic embryos may be depleted by cell death, other types of cell selection or cell correction but the most severely affected mosaic embryos probably die. Trisomic cells could become restricted to placental lineages if cell selection or correction is less effective in placental lineages and/or they are preferentially allocated to a placental lineage. However, the relationship between preimplantation mosaicism and confined placental mosaicism may be complex because the specific chromosome(s) involved will influence whether chromosomally abnormal cells survive predominately in the placental trophoblast and/or placental mesenchyme. Lay summary Human cells normally have 23 pairs of chromosomes, which carry the genes. During the first few days of development, some human embryos are chromosomal mosaics. These mosaic embryos have both normal cells and cells with an abnormal number of chromosomes, which arise from the same fertilised egg. (More rarely, the different cell populations arise from more than one fertilised egg and these embryos are called chimaeras.) If chromosomally abnormal cells survive to term, they could cause birth defects. However, few abnormal cells survive and those that do are usually confined to the placenta, where they are less likely to cause harm. It is not yet understood how this restriction occurs but the type of chromosomal abnormality influences which placental tissues are affected. This review discusses the origin of different types of chromosomally abnormal cells, their fate and how they might become confined to the placenta in humans and animal models.
Collapse
Affiliation(s)
- John D West
- Section of Obstetrics and Gynaecology, Clinical Sciences, The Queen's Medical Research Institute, The University of Edinburgh, Edinburgh, UK
| | - Clare A Everett
- Section of Obstetrics and Gynaecology, Clinical Sciences, The Queen's Medical Research Institute, The University of Edinburgh, Edinburgh, UK
| |
Collapse
|
25
|
Cleavage of Early Mouse Embryo with Damaged DNA. Int J Mol Sci 2022; 23:ijms23073516. [PMID: 35408877 PMCID: PMC8998204 DOI: 10.3390/ijms23073516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 03/21/2022] [Accepted: 03/22/2022] [Indexed: 02/02/2023] Open
Abstract
The preimplantation period of embryogenesis is crucial during mammalian ontogenesis. During this period, the mitotic cycles are initiated, the embryonic genome is activated, and the primary differentiation of embryonic cells occurs. All cellular abnormalities occurring in this period are the primary cause of fetal developmental disorders. DNA damage is a serious cause of developmental failure. In the context of DNA damage response on the cellular level, we analyzed the course of embryogenesis and phenotypic changes during the cleavage of a preimplantation embryo. Our results document that DNA damage induced before the resumption of DNA synthesis in a zygote can significantly affect the preimplantation development of the embryo. This developmental ability is related to the level of the DNA damage. We showed that one-cell embryos can correct the first cleavage cycle despite low DNA damage and incomplete replication. It seems that the phenomenon creates a predisposition to a segregation disorder of condensed chromatin that results in the formation of micronuclei in the developmental stages following the first cleavage. We conclude that zygote tolerates a certain degree of DNA damage and considers its priority to complete the first cleavage stage and continue embryogenesis as far as possible.
Collapse
|
26
|
Cell size and polarization determine cytokinesis furrow ingression dynamics in mouse embryos. Proc Natl Acad Sci U S A 2022; 119:e2119381119. [PMID: 35294282 PMCID: PMC8944651 DOI: 10.1073/pnas.2119381119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The final step of cell division, termed cytokinesis, comprises the constriction of a furrow that divides the cytoplasm to form two daughter cells. Although cytokinesis is well studied in traditional cell systems, how cytokinesis is regulated in complex multicellular settings and during cell-fate decisions is less well understood. Here, using live imaging and physical and molecular interventions, we find that the emergence of cell polarity during mouse embryo morphogenesis dramatically impacts cytokinesis mechanisms. Specifically, the assembly of the apical domain in outer cells locally inhibits the cytokinetic machinery, leading to an unexpected laterally biased cytokinesis. Cytokinesis is the final step of cell division during which a contractile ring forms a furrow that partitions the cytoplasm in two. How furrow ingression is spatiotemporally regulated and how it is adapted to complex cellular environments and developmental transitions remain poorly understood. Here, we examine furrow ingression dynamics in the context of the early mouse embryo and find that cell size is a powerful determinant of furrow ingression speed during reductive cell divisions. In addition, the emergence of cell polarity and the assembly of the apical domain in outer cells locally inhibits the recruitment of cytokinesis components and thereby negatively regulates furrow ingression specifically on one side of the furrow. We show that this biasing of cytokinesis is not dependent upon cell–cell adhesion or shape but rather is cell intrinsic and is caused by a paucity of cytokinetic machinery in the apical domain. The results thus reveal that in the mouse embryo cell polarity directly regulates the recruitment of cytokinetic machinery in a cell-autonomous manner and that subcellular organization can instigate differential force generation and constriction speed in different zones of the cytokinetic furrow.
Collapse
|
27
|
Mammel AE, Huang HZ, Gunn AL, Choo E, Hatch EM. Chromosome length and gene density contribute to micronuclear membrane stability. Life Sci Alliance 2022; 5:e202101210. [PMID: 34789512 PMCID: PMC8605325 DOI: 10.26508/lsa.202101210] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 11/01/2021] [Accepted: 11/03/2021] [Indexed: 11/24/2022] Open
Abstract
Micronuclei are derived from missegregated chromosomes and frequently lose membrane integrity, leading to DNA damage, innate immune activation, and metastatic signaling. Here, we demonstrate that two characteristics of the trapped chromosome, length and gene density, are key contributors to micronuclei membrane stability and determine the timing of micronucleus rupture. We demonstrate that these results are not due to chromosome-specific differences in spindle position or initial protein recruitment during post-mitotic nuclear envelope assembly. Micronucleus size strongly correlates with lamin B1 levels and nuclear pore density in intact micronuclei, but, unexpectedly, lamin B1 levels do not completely predict nuclear lamina organization or membrane stability. Instead, small gene-dense micronuclei have decreased nuclear lamina gaps compared to large micronuclei, despite very low levels of lamin B1. Our data strongly suggest that nuclear envelope composition defects previously correlated with membrane rupture only partly explain membrane stability in micronuclei. We propose that an unknown factor linked to gene density has a separate function that inhibits the appearance of nuclear lamina gaps and delays membrane rupture until late in the cell cycle.
Collapse
Affiliation(s)
- Anna E Mammel
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Heather Z Huang
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Amanda L Gunn
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Emma Choo
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Emily M Hatch
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| |
Collapse
|
28
|
Papathanasiou S, Markoulaki S, Blaine LJ, Leibowitz ML, Zhang CZ, Jaenisch R, Pellman D. Whole chromosome loss and genomic instability in mouse embryos after CRISPR-Cas9 genome editing. Nat Commun 2021; 12:5855. [PMID: 34615869 PMCID: PMC8494802 DOI: 10.1038/s41467-021-26097-y] [Citation(s) in RCA: 73] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 09/13/2021] [Indexed: 12/26/2022] Open
Abstract
Karyotype alterations have emerged as on-target complications from CRISPR-Cas9 genome editing. However, the events that lead to these karyotypic changes in embryos after Cas9-treatment remain unknown. Here, using imaging and single-cell genome sequencing of 8-cell stage embryos, we track both spontaneous and Cas9-induced karyotype aberrations through the first three divisions of embryonic development. We observe the generation of abnormal structures of the nucleus that arise as a consequence of errors in mitosis, including micronuclei and chromosome bridges, and determine their contribution to common karyotype aberrations including whole chromosome loss that has been recently reported after editing in embryos. Together, these data demonstrate that Cas9-mediated germline genome editing can lead to unwanted on-target side effects, including major chromosome structural alterations that can be propagated over several divisions of embryonic development.
Collapse
Affiliation(s)
- Stamatis Papathanasiou
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | | | - Logan J Blaine
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Mitchell L Leibowitz
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Cheng-Zhong Zhang
- Department of Biomedical Informatics, Harvard Medical School, Boston, MA, USA
- Department of Data Sciences, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Rudolf Jaenisch
- Whitehead Institute, Cambridge, MA, USA.
- Massachusetts Institute of Technology, Department of Biology, Cambridge, MA, USA.
| | - David Pellman
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.
- Howard Hughes Medical Institute, Chevy Chase, MD, USA.
| |
Collapse
|
29
|
Li X, Hao Y, Chen D, Ji D, Zhu W, Zhu X, Wei Z, Cao Y, Zhang Z, Zhou P. Non-invasive preimplantation genetic testing for putative mosaic blastocysts: a pilot study. Hum Reprod 2021; 36:2020-2034. [PMID: 33974705 DOI: 10.1093/humrep/deab080] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 03/06/2021] [Indexed: 12/27/2022] Open
Abstract
STUDY QUESTION What is the potential of applying non-invasive preimplantation genetic testing (niPGT) for chromosome abnormalities in blastocysts reported with a mosaic trophectoderm (TE) biopsy? SUMMARY ANSWER niPGT of cell-free DNA in blastocyst culture medium exhibited a good diagnostic performance in putative mosaic blastocysts. WHAT IS KNOWN ALREADY Advances in niPGT have demonstrated the potential reliability of cell-free DNA as a resource for genetic assessment, but information on mosaic embryos is scarce because the mosaicism may interfere with niPGT. In addition, the high incidence of mosaicism reported in the context of PGT and the viability of mosaic blastocysts raise questions about whether mosaicism really exists. STUDY DESIGN, SIZE, DURATION The study was performed between May 2020 and July 2020. First, clinical data collected by a single-center over a 6-year period on PGT for chromosome aneuploidies (PGT-A) or chromosomal structural rearrangements (PGT-SR) were analyzed. After confirming the reliability of niPGT, 41 blastocysts classified as mosaics by trophectoderm (TE) biopsy were re-cultured. The chromosomal copy number of the blastocyst embryo (BE, the gold standard), TE re-biopsy, and corresponding cell-free DNA in the culture medium was assessed. PARTICIPANTS/MATERIALS, SETTING, METHODS Data on patients enrolled for PGT at a single center from 2014 to 2019 were collected and the cycles with available putative mosaic blastocysts were evaluated. To verify the diagnostic validity of niPGT, eight aneuploid blastocysts were thawed and re-cultured for 14-18 h. The concordance of the niPGT diagnosis results and the whole blastocyst testing results was analyzed. Forty-one blastocysts reported as mosaics from 22 patients were included and re-cultured for 14-18 h. The genetic material of the BE, TE re-biopsy, and corresponding cell-free DNA in the culture medium was amplified using multiple annealing and looping-based amplification cycles. The karyotype data from niPGT and TE re-biopsy were compared with that from the whole blastocyst, and the efficiency of niPGT was assessed. MAIN RESULTS AND THE ROLE OF CHANCE Data on 3738 blastocysts from 785 PGT-A or PGT-SR cycles of 677 patients were collected. According to the TE biopsy report, of the 3662 (98%) successfully amplified samples, 24 (0.6%) yielded no results, 849 (23.2%) were euploid, 2245 (61.3%) were aneuploid, and 544 (14.9%) were mosaic. Sixty patients without euploid blastocysts opted for a single mosaic blastocyst transfer, and 30 (50%) of them obtained a clinical pregnancy. With the BE chromosome copy number as the gold standard, niPGT and TE re-biopsy showed reliable detection ability and diagnostic efficiency in eight putative aneuploid blastocysts. Of the 41 putative mosaic blastocysts re-cultured and re-tested, 35 (85.4%) showed euploid BE results. All but two of the blastocysts previously diagnosed with segmental chromosomal mosaic were actually euploid. In addition, all blastocysts previously classified as low degree (20-50%) mosaics were identified as euploid by BE PGT, whereas four of the six putative high degree (50-80%) mosaic blastocysts showed chromosomal abnormalities. The raw concordance rates of spent culture medium (SCM) and TE re-biopsies compared with BE were 74.4% and 82%, respectively, in terms of overall ploidy and 96.2% and 97.6%, respectively, per single chromosome when considering all degree mosaic results as true positives. However, when we set a mosaicism identification threshold of 50%, the concordance rates of SCM and TE re-biopsies compared with BE were 87.2% and 85% at the overall ploidy level and 98.8% and 98.3% at the chromosomal level, respectively. At the full ploidy level, the sensitivity and false negative rates for niPGT were 100% and 0, respectively. After adjustment of the threshold for mosaicism, the specificity of niPGT increased from 69.7% to 84.8% in terms of overall ploidy and from 96.1% to 98.9% at the chromosomal level. LIMITATIONS, REASONS FOR CAUTION The primary limitation of this study is the small sample size, which decreases the strength of our conclusions. If possible, identifying the clinical outcome of niPGT on reassessed mosaic blastocysts would be further progress in this field. WIDER IMPLICATIONS OF THE FINDINGS This study is the first to explore the practicability of niPGT in diagnostic reassessment of putative mosaicism. The present study provides a novel opportunity for patients with only mosaic blastocysts and no euploid blastocysts, regardless of the technical or biological basis of mosaicism. Employing niPGT after 14-18 h of re-culturing might be a superior option for the best use of blastocysts because of its minimally invasive nature. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by grants from National Key Technology Research and Development Program of China (No. 2017YFC1002004), the Central Guiding the Science and Technology Development of the Local (2018080802D0081) and College Natural Science Project of Anhui Province (KJ2019A0287). There are no competing interests to declare. TRIAL REGISTRATION NUMBER N/A.
Collapse
Affiliation(s)
- Xinyuan Li
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract, Anhui Medical University, Hefei, Anhui, China.,Key Laboratory of Population Health Across Life Cycle, Anhui Medical University, Ministry of Education of the People's Republic of China, Hefei, Anhui, China
| | - Yan Hao
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract, Anhui Medical University, Hefei, Anhui, China.,Key Laboratory of Population Health Across Life Cycle, Anhui Medical University, Ministry of Education of the People's Republic of China, Hefei, Anhui, China
| | - Dawei Chen
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, Anhui, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, Anhui, China
| | - Dongmei Ji
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, Anhui, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, Anhui, China
| | - Wanbo Zhu
- Affiliated Anhui Provincial Hospital of Anhui Medical University, Anhui, China
| | - Xiaoqian Zhu
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, Anhui, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, Anhui, China
| | - Zhaolian Wei
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, Anhui, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, Anhui, China
| | - Yunxia Cao
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, Anhui, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, Anhui, China
| | - Zhiguo Zhang
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract, Anhui Medical University, Hefei, Anhui, China.,Key Laboratory of Population Health Across Life Cycle, Anhui Medical University, Ministry of Education of the People's Republic of China, Hefei, Anhui, China
| | - Ping Zhou
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, the First Affiliated Hospital of Anhui Medical University, Anhui, China.,NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract, Anhui Medical University, Hefei, Anhui, China.,Key Laboratory of Population Health Across Life Cycle, Anhui Medical University, Ministry of Education of the People's Republic of China, Hefei, Anhui, China
| |
Collapse
|
30
|
Dai X, Guo X. Decoding and rejuvenating human ageing genomes: Lessons from mosaic chromosomal alterations. Ageing Res Rev 2021; 68:101342. [PMID: 33866012 DOI: 10.1016/j.arr.2021.101342] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 04/05/2021] [Accepted: 04/07/2021] [Indexed: 01/10/2023]
Abstract
One of the most curious findings emerged from genome-wide studies over the last decade was that genetic mosaicism is a dominant feature of human ageing genomes. The clonal dominance of genetic mosaicism occurs preceding the physiological and physical ageing and associates with propensity for diseases including cancer, Alzheimer's disease, cardiovascular disease and diabetes. These findings are revolutionizing the ways biologists thinking about health and disease pathogenesis. Among all mosaic mutations in ageing genomes, mosaic chromosomal alterations (mCAs) have the most significant functional consequences because they can produce intercellular genomic variations simultaneously involving dozens to hundreds or even thousands genes, and therefore have most profound effects in human ageing and disease etiology. Here, we provide a comprehensive picture of the landscapes, causes, consequences and rejuvenation of mCAs at multiple scales, from cell to human population, by reviewing data from cytogenetic, genetic and genomic studies in cells, animal models (fly and mouse) and, more frequently, large-cohort populations. A detailed decoding of ageing genomes with a focus on mCAs may yield important insights into the genomic architecture of human ageing, accelerate the risk stratification of age-related diseases (particularly cancers) and development of novel targets and strategies for delaying or rejuvenating human (genome) ageing.
Collapse
Affiliation(s)
- Xueqin Dai
- School of Life Sciences, Yunnan Normal University, Kunming, Yunnan, 650500, China
| | - Xihan Guo
- School of Life Sciences, Yunnan Normal University, Kunming, Yunnan, 650500, China; The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Kunming, Yunnan, 650500, China; Yunnan Environmental Mutagen Society, Kunming, Yunnan, 650500, China.
| |
Collapse
|
31
|
Leibowitz ML, Papathanasiou S, Doerfler PA, Blaine LJ, Sun L, Yao Y, Zhang CZ, Weiss MJ, Pellman D. Chromothripsis as an on-target consequence of CRISPR-Cas9 genome editing. Nat Genet 2021; 53:895-905. [PMID: 33846636 PMCID: PMC8192433 DOI: 10.1038/s41588-021-00838-7] [Citation(s) in RCA: 295] [Impact Index Per Article: 98.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 03/08/2021] [Indexed: 12/16/2022]
Abstract
Genome editing has therapeutic potential for treating genetic diseases and cancer. However, the currently most practicable approaches rely on the generation of DNA double-strand breaks (DSBs), which can give rise to a poorly characterized spectrum of chromosome structural abnormalities. Here, using model cells and single-cell whole-genome sequencing, as well as by editing at a clinically relevant locus in clinically relevant cells, we show that CRISPR-Cas9 editing generates structural defects of the nucleus, micronuclei and chromosome bridges, which initiate a mutational process called chromothripsis. Chromothripsis is extensive chromosome rearrangement restricted to one or a few chromosomes that can cause human congenital disease and cancer. These results demonstrate that chromothripsis is a previously unappreciated on-target consequence of CRISPR-Cas9-generated DSBs. As genome editing is implemented in the clinic, the potential for extensive chromosomal rearrangements should be considered and monitored.
Collapse
Affiliation(s)
- Mitchell L Leibowitz
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Stamatis Papathanasiou
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Phillip A Doerfler
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Logan J Blaine
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Lili Sun
- Single-Cell Sequencing Program, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Yu Yao
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Cheng-Zhong Zhang
- Department of Biomedical Informatics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Department of Data Sciences, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Mitchell J Weiss
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN, USA.
| | - David Pellman
- Howard Hughes Medical Institute, Chevy Chase, MD, USA.
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.
| |
Collapse
|
32
|
Benn P. Uniparental disomy: Origin, frequency, and clinical significance. Prenat Diagn 2021; 41:564-572. [PMID: 33179335 DOI: 10.1002/pd.5837] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 06/28/2020] [Accepted: 09/29/2020] [Indexed: 02/06/2023]
Abstract
Uniparental disomy (UPD) is defined as two copies of a whole chromosome derived from the same parent. There can be multiple mechanisms that lead to UPD; these are reviewed in the context of contemporary views on the mechanism leading to aneuploidy. Recent studies indicate that UPD is rare in an apparently healthy population and also rare in spontaneous abortion tissues. The most common type of UPD is a maternal heterodisomy (both maternal allele sets present). Isodisomy (a duplicated single set of alleles) or segmental loss of heterozygosity is sometimes encountered in SNP-based microarray referrals. Decisions regarding the most appropriate follow-up testing should consider the possibility of consanguinity (that will generally involve multiple regions), an imprinted gene disorder (chromosomes 6, 7, 11, 14, 15, 20), expression of an autosomal recessive disorder, and an occult aneuploid cell line that may be confined to the placenta. Upd(16)mat, per se, does not appear to be associated with an abnormal phenotype. UPD provides an insight into the history of early chromosome segregation error and understanding the rates and fate of these events are of key importance in the provision of fertility management and prenatal healthcare.
Collapse
Affiliation(s)
- Peter Benn
- Department of Genetics and Genome Sciences, UConn Health, Farmington, Connecticut, USA
| |
Collapse
|
33
|
Chuang TH, Chang YP, Lee MJ, Wang HL, Lai HH, Chen SU. The Incidence of Mosaicism for Individual Chromosome in Human Blastocysts Is Correlated With Chromosome Length. Front Genet 2021; 11:565348. [PMID: 33488666 PMCID: PMC7815765 DOI: 10.3389/fgene.2020.565348] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 11/30/2020] [Indexed: 12/18/2022] Open
Abstract
Mosaicism, known as partial aneuploidies, mostly originates from mitotic errors during the post-zygotic stage; it consists of different cell lineages within a human embryo. The incidence of mosaicism has not been shown to correlate with maternal age, and its correlation with individual chromosome characteristics has not been well investigated. In this study, the results of preimplantation genetic testing for aneuploidy (PGT-A) derived from 4,036 blastocysts (930 IVF couples) were collected from 2015 to 2017. Via next-generation sequencing for comprehensive chromosome screening, embryo ploidy was identified as aneuploid, mosaic, and euploid. Total mosaicism was classified into two categories: "mosaic euploid/aneuploidy" (with mosaic aneuploidy between 20 and 80%) and "mosaic and aneuploidy" (a uniformly abnormal embryo superimposed with mosaic aneuploidies). Frequency of mosaicism was analyzed according to the function of chromosomal lengths, which divides involved chromosomes into three groups: group A (156-249 Mb), group B (102-145 Mb), and group C (51-90 Mb). The results show that the aneuploidy was more frequent in group C than in group A and group B (A: 23.7%, B: 35.1, 41.2%, p < 0.0001), while the mosaicism was more frequent in group A and group B than in group C [(Mosaic euploid/aneuploid) A: 14.6%, B: 12.4%, C: 9.9%, p < 0.0001; (mosaic and aneuploid) A: 21.3%, B: 22.9%, C: 18.9%, p < 0.0001; (Total mosaicism) A: 35.9%, B: 35.3%, C: 28.8%, p < 0.0001]. The significantly higher frequency of aneuploidy was on the shorter chromosome (< 90 Mb), and that of mosaicism was on the longer chromosomes (> 100 Mb). The length association did not reach significance in the patients with advanced age (≥ 36 years), and of the chromosome-specific mosaicism rate, the highest prevalence was on chromosome 14 (5.8%), 1 (5.7%), and 9 (5.6%). Although the length association was observed via group comparison, there may be affecting mechanisms other than chromosomes length. Eventually, twenty patients with mosaic embryo cryotransfers resulted in six live births. No significant correlation was observed between the transfer outcomes and chromosome length; however, the analysis was limited by small sample size.
Collapse
Affiliation(s)
- Tzu-Hsuan Chuang
- Stork Fertility Center, Stork Ladies Clinic, Hsinchu City, Taiwan
| | - Ya-Ping Chang
- Stork Fertility Center, Stork Ladies Clinic, Hsinchu City, Taiwan
| | - Meng-Ju Lee
- Stork Fertility Center, Stork Ladies Clinic, Hsinchu City, Taiwan
| | - Huai-Ling Wang
- Stork Fertility Center, Stork Ladies Clinic, Hsinchu City, Taiwan
| | - Hsing-Hua Lai
- Stork Fertility Center, Stork Ladies Clinic, Hsinchu City, Taiwan
| | - Shee-Uan Chen
- Department of Obstetrics and Gynecology, National Taiwan University Hospital and College of Medicine, Taipei City, Taiwan
| |
Collapse
|
34
|
Liu S, Pellman D. The coordination of nuclear envelope assembly and chromosome segregation in metazoans. Nucleus 2020; 11:35-52. [PMID: 32208955 PMCID: PMC7289584 DOI: 10.1080/19491034.2020.1742064] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 03/08/2020] [Accepted: 03/10/2020] [Indexed: 01/25/2023] Open
Abstract
The nuclear envelope (NE) is composed of two lipid bilayer membranes that enclose the eukaryotic genome. In interphase, the NE is perforated by thousands of nuclear pore complexes (NPCs), which allow transport in and out of the nucleus. During mitosis in metazoans, the NE is broken down and then reassembled in a manner that enables proper chromosome segregation and the formation of a single nucleus in each daughter cell. Defects in coordinating NE reformation and chromosome segregation can cause aberrant nuclear architecture. This includes the formation of micronuclei, which can trigger a catastrophic mutational process commonly observed in cancers called chromothripsis. Here, we discuss the current understanding of the coordination of NE reformation with chromosome segregation during mitotic exit in metazoans. We review differing models in the field and highlight recent work suggesting that normal NE reformation and chromosome segregation are physically linked through the timing of mitotic spindle disassembly.
Collapse
Affiliation(s)
- Shiwei Liu
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - David Pellman
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| |
Collapse
|
35
|
Kwon M, Leibowitz ML, Lee JH. Small but mighty: the causes and consequences of micronucleus rupture. Exp Mol Med 2020; 52:1777-1786. [PMID: 33230251 PMCID: PMC8080619 DOI: 10.1038/s12276-020-00529-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/20/2022] Open
Abstract
Micronuclei are small DNA-containing nuclear structures that are spatially isolated from the main nucleus. They are frequently found in pathologies, including cancer. It was recently shown that these nuclear structures are not only biomarkers of disease but also play an active role in tumor biology. Many consequences of micronucleus formation on tumor biology are dependent on the frequent and irreversible rupture of their nuclear envelopes, which results in the exposure of their DNA contents to the cytoplasm. In this review, we discuss models of defective nuclear envelope deposition on missegregated chromosomes that lead to nuclear envelope rupture. Furthermore, we expound upon the various downstream consequences of micronucleus nuclear envelope rupture on cells. These consequences include a massive DNA rearrangement phenomenon called chromothripsis and activation of the cGAS-STING innate immune signaling pathway, which can be a double-edged sword with tumorigenesis and tumor prevention functions. Although micronuclei are small structures, the impact they have on cells and their microenvironment is quite large. Micronuclei, which contain faulty chromosomes or chromosome fragments and occur outside the main cellular nucleus, are prone to rupturing, which leads to DNA changes that can drive tumor development. A team led by Mijung Kwon from Ewha Womans University in Seoul and Jae-Ho Lee of Ajou University School of Medicine in Suwon, both in South Korea, review how these micronuclei tend to burst, spilling their contents into the cell with devastating consequences. The chromosomes they contain break into tiny fragments and this broken DNA finds its way into the main nucleus, leading to chromosomal rearrangements that can permanently alter genomic function. The rupture of micronuclei also activates a part of the innate immune system that can promote cancer cell invasion and spread. Drugs targeting these processes could aid in the treatment of cancer.
Collapse
Affiliation(s)
- Mijung Kwon
- Department of Life Science and the Research Center for Cellular Homeostasis, Ewha Womans University, Seoul, 03760, Korea.
| | - Mitchell L Leibowitz
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Jae-Ho Lee
- Department of Biochemistry and Molecular Biology, Suwon, 16499, South Korea. .,Institute of Medical Science, Ajou University School of Medicine, Suwon, 16499, South Korea.
| |
Collapse
|
36
|
Abstract
The nuclear envelope is often depicted as a static barrier that regulates access between the nucleus and the cytosol. However, recent research has identified many conditions in cultured cells and in vivo in which nuclear membrane ruptures cause the loss of nuclear compartmentalization. These conditions include some that are commonly associated with human disease, such as migration of cancer cells through small spaces and expression of nuclear lamin disease mutations in both cultured cells and tissues undergoing nuclear migration. Nuclear membrane ruptures are rapidly repaired in the nucleus but persist in nuclear compartments that form around missegregated chromosomes called micronuclei. This review summarizes what is known about the mechanisms of nuclear membrane rupture and repair in both the main nucleus and micronuclei, and highlights recent work connecting the loss of nuclear integrity to genome instability and innate immune signaling. These connections link nuclear membrane rupture to complex chromosome alterations, tumorigenesis, and laminopathy etiologies.
Collapse
Affiliation(s)
- John Maciejowski
- Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA;
| | - Emily M Hatch
- Division of Basic Sciences and Human Biology, The Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA;
| |
Collapse
|
37
|
Ducheyne KD, Rizzo M, Cuervo-Arango J, Claes A, Daels PF, Stout TAE, de Ruijter-Villani M. In vitro production of horse embryos predisposes to micronucleus formation, whereas time to blastocyst formation affects likelihood of pregnancy. Reprod Fertil Dev 2020; 31:1830-1839. [PMID: 31771747 DOI: 10.1071/rd19227] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 11/02/2019] [Indexed: 12/29/2022] Open
Abstract
Invitro embryo production is an increasingly popular means of breeding horses. However, success is limited by a high incidence of early embryo loss. Although there are various possible causes of pregnancy failure, chromosomal abnormalities, including aneuploidy, are important potential contributors. This study evaluated the frequency of micronucleus formation as a proxy for aneuploidy in invitro-produced (IVP) and invivo-derived horse blastocysts. Associations between IVP embryo morphology, frequency of nuclear abnormalities and the likelihood of pregnancy were investigated. IVP blastocysts exhibited a higher frequency of cells with micronuclei than invivo-derived embryos (10% vs 1% respectively; P=0.05). This indication of chromosomal instability may explain the higher incidence of pregnancy failure after transfer of IVP embryos. However, the frequency of micronuclei was not correlated with brightfield microscopic morphological characteristics. Nevertheless, IVP embryos reaching the blastocyst stage after Day 9 of invitro culture were less likely to yield a pregnancy than embryos that developed to blastocysts before Day 9 (27% vs 69%), and embryos that had expanded before transfer were more likely to undergo embryonic death than those that had not expanded (44% vs 10%). These findings indicate that current embryo culture conditions are suboptimal and that the speed of embryo development is correlated with pregnancy survival.
Collapse
Affiliation(s)
- Kaatje D Ducheyne
- Department of Medical Imaging and Small Animal Orthopaedics, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium; and Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Marilena Rizzo
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Juan Cuervo-Arango
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Anthony Claes
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Peter F Daels
- Department of Medical Imaging and Small Animal Orthopaedics, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
| | - Tom A E Stout
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands
| | - Marta de Ruijter-Villani
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 114, 3584CM Utrecht, Netherlands; and Corresponding author.
| |
Collapse
|
38
|
Guo X, Dai X, Wu X, Cao N, Wang X. Small but strong: Mutational and functional landscapes of micronuclei in cancer genomes. Int J Cancer 2020; 148:812-824. [PMID: 32949152 DOI: 10.1002/ijc.33300] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 08/10/2020] [Accepted: 09/09/2020] [Indexed: 12/11/2022]
Abstract
Micronuclei, small spatially-separated, nucleus-like structures, are a common feature of human cancer cells. There are considerable heterogeneities in the sources, structures and genetic activities of micronuclei. Accumulating evidence suggests that micronuclei and main nuclei represent separate entities with respect to DNA replication, DNA damage sensing and repairing capacity because micronuclei are not monitored by the same checkpoints nor covered by the same nuclear envelope as the main nuclei. Thus, micronuclei are spatially restricted "mutation factories." Several large-scale DNA sequencing and bioinformatics studies over the last few years have revealed that most micronuclei display a mutational signature of chromothripsis immediately after their generation and the underlying molecular mechanisms have been dissected extensively. Clonal expansion of the micronucleated cells is context-dependent and is associated with chromothripsis and several other mutational signatures including extrachromosomal circular DNA, kataegis and chromoanasynthesis. These results suggest what was once thought to be merely a passive indicator of chromosomal instability is now being recognized as a strong mutator phenotype that may drive intratumoral genetic heterogeneity. Herein, we revisit the actionable determinants that contribute to the bursts of mutagenesis in micronuclei and present the growing number of evidence which suggests that micronuclei have distinct short- and long-term mutational and functional effects to cancer genomes. We also pose challenges for studying the long-term effects of micronucleation in the upcoming years.
Collapse
Affiliation(s)
- Xihan Guo
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Yunnan Normal University, Kunming, Yunnan, China.,Yunnan Environmental Society, Kunming, Yunnan, China
| | - Xueqin Dai
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Xue Wu
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Yunnan Normal University, Kunming, Yunnan, China
| | - Neng Cao
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Yunnan Normal University, Kunming, Yunnan, China
| | - Xu Wang
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Yunnan Normal University, Kunming, Yunnan, China.,Yunnan Environmental Society, Kunming, Yunnan, China
| |
Collapse
|
39
|
Macaulay AD, Allais A, FitzHarris G. Chromosome dynamics and spindle microtubule establishment in mouse embryos. FASEB J 2020; 34:8057-8067. [PMID: 32329130 DOI: 10.1096/fj.201902947r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 03/25/2020] [Accepted: 03/31/2020] [Indexed: 11/11/2022]
Abstract
Chromosome segregation errors in mammalian embryos are common and jeopardize embryo health. Here, we perform for the first time 4-Dimensional imaging and tracking of chromosomes and centromeres through each preimplantation mitotic cell division in mouse embryos to define the normal dynamics of chromosome segregation. We show that a microtubule (MT)-dependent inward movement of chromosomes occurs at the time of nuclear envelope breakdown (NEBD), particularly in the earliest cell divisions, to position chromosomes prior to spindle assembly. Establishment of a rudimentary metaphase plate occurs immediately after NEBD, and is followed by a progressive alignment and biorientation of mitotic chromosomes. Stable end-on kinetochore-MT attachments form rapidly and attachment errors are uncommon. Altogether our data describe a rapid and efficient spindle assembly pathway that apparently minimizes the need for canonical MT attachment error correction in normally dividing embryos.
Collapse
Affiliation(s)
- Angus D Macaulay
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, QC, Canada
| | - Adélaïde Allais
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, QC, Canada
| | - Greg FitzHarris
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, QC, Canada.,Department of OBGYN, Université de Montréal, Montreal, QC, Canada
| |
Collapse
|
40
|
Guo X, Dai X, Zhou T, Wang H, Ni J, Xue J, Wang X. Mosaic loss of human Y chromosome: what, how and why. Hum Genet 2020; 139:421-446. [DOI: 10.1007/s00439-020-02114-w] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 01/06/2020] [Indexed: 02/07/2023]
|
41
|
Lin E, Li Z, Huang Y, Ru G, He P. High Dosages of Equine Chorionic Gonadotropin Exert Adverse Effects on the Developmental Competence of IVF-Derived Mouse Embryos and Cause Oxidative Stress-Induced Aneuploidy. Front Cell Dev Biol 2020; 8:609290. [PMID: 33634101 PMCID: PMC7900142 DOI: 10.3389/fcell.2020.609290] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/21/2020] [Indexed: 02/05/2023] Open
Abstract
Gonadotropins play vital roles in the regulation of female reproductive ability and fertility. Our study aimed to determine the effects of superovulation induced by increasing doses of equine chorionic gonadotropin [eCG; also referred to as pregnant mare serum gonadotropin (PMSG)] on the developmental competence of mouse embryos and on aneuploidy formation during in vitro fertilization (IVF). eCG dose-dependently enhanced the oocyte yield from each mouse. Administration of 15 IU eCG significantly reduced the fertilization rate and the formation of four-cell embryos and blastocysts and increased the risk of chromosome aneuploidy. The IVF-derived blastocysts in the 15 IU eCG treatment group had the fewest total cells, inner cell mass (ICM) cells and trophectoderm (TE) cells. Moreover, more blastocysts and fewer apoptotic cells were observed in the 0, 5, and 10 IU eCG treatment groups than in the 15 IU eCG treatment group. We also investigated reactive oxygen species (ROS) levels and variations in several variables: mitochondrial membrane potential (MMP); active mitochondria; mitochondrial superoxide production; adenosine triphosphate (ATP) content; spindle structures; chromosome karyotypes; microfilament distribution; and the expression of Aurora B [an important component of the chromosomal passenger complex (CPC)], the spindle assembly checkpoint (SAC) protein mitotic arrest deficient 2 like 1 (MAD2L1), and the DNA damage response (DDR) protein γH2AX. Injection of 15 IU eCG increased ROS levels, rapidly reduced MMP, increased active mitochondria numbers and mitochondrial superoxide production, reduced ATP content, increased abnormal spindle formation rates, and induced abnormalities in chromosome number and microfilament distribution, suggesting that a high dose of eCG might alter developmental competence and exert negative effects on IVF-obtained mouse embryos. Additionally, the appearance of γH2AX and the significantly increased expression of Aurora B and MAD2L1 suggested that administration of relatively high doses of eCG caused Aurora B-mediated SAC activation triggered by ROS-induced DNA damage in early mouse IVF-derived embryos for self-correction of aneuploidy formation. These findings improve our understanding of the application of gonadotropins and provide a theoretical basis for gonadotropin treatment.
Collapse
|
42
|
The mechanisms and clinical application of mosaicism in preimplantation embryos. J Assist Reprod Genet 2019; 37:497-508. [PMID: 31838629 DOI: 10.1007/s10815-019-01656-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 12/05/2019] [Indexed: 02/08/2023] Open
Abstract
Embryos containing distinct cell lines are referred to as mosaic embryos, which are considered to be caused by mitotic errors in chromosome segregation during preimplantation development. As the accuracy and resolution of detection techniques improve, more and more mosaic embryos were identified recently. The impacts of mosaic embryos on survival and potential pregnancy outcome have been reported to be diverse in different studies. Because of the universality and clinical significance of mosaicism, it is essential to unravel the mechanisms and consequences with regard to this phenomenon in human pre- and post-implantation embryos. The purpose of this review is to explore the mechanisms, causes of mosaicism, and the development of pre- and post-implantation mosaic embryos in the light of recent emerging data, with the aim of providing new references for clinical applications.
Collapse
|
43
|
Paim LMG, FitzHarris G. Tetraploidy causes chromosomal instability in acentriolar mouse embryos. Nat Commun 2019; 10:4834. [PMID: 31645568 PMCID: PMC6811537 DOI: 10.1038/s41467-019-12772-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 09/20/2019] [Indexed: 11/16/2022] Open
Abstract
Tetraploidisation is considered a common event in the evolution of chromosomal instability (CIN) in cancer cells. The current model for how tetraploidy drives CIN in mammalian cells is that a doubling of the number of centrioles that accompany the genome doubling event leads to multipolar spindle formation and chromosome segregation errors. By exploiting the unusual scenario of mouse blastomeres, which lack centrioles until the ~64-cell stage, we show that tetraploidy can drive CIN by an entirely distinct mechanism. Tetraploid blastomeres assemble bipolar spindles dictated by microtubule organising centres, and multipolar spindles are rare. Rather, kinetochore-microtubule turnover is altered, leading to microtubule attachment defects and anaphase chromosome segregation errors. The resulting blastomeres become chromosomally unstable and exhibit a dramatic increase in whole chromosome aneuploidies. Our results thus reveal an unexpected mechanism by which tetraploidy drives CIN, in which the acquisition of chromosomally-unstable microtubule dynamics contributes to chromosome segregation errors following tetraploidisation.
Collapse
Affiliation(s)
- Lia Mara Gomes Paim
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, H2X 0A9, Montreal, QC, Canada
| | - Greg FitzHarris
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, H2X 0A9, Montreal, QC, Canada.
- Département d'Obstétrique-Gynécologie, Université de Montréal, H3T 1C5, Montreal, QC, Canada.
| |
Collapse
|
44
|
Escribà MJ, Vendrell X, Peinado V. Segmental aneuploidy in human blastocysts: a qualitative and quantitative overview. Reprod Biol Endocrinol 2019; 17:76. [PMID: 31526391 PMCID: PMC6745804 DOI: 10.1186/s12958-019-0515-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/19/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Microarray-based and next generation sequencing (NGS) technologies have revealed that segmental aneuploidy is frequently present in human oocytes, cleavage-stage embryos and blastocysts. However, very little research has analyzed the type, size, chromosomal distribution and topography of the chromosomal segments at the different stages of development. METHODS This is a retrospective study of 822 PGT-A (preimplantation genetic test for aneuploidies) performed on trophectoderm samples from 3565 blastocysts biopsied between January 2016 and April 2017. The cycles in question had been initiated for varying clinical indications. Samples were analyzed by next generation sequencing-based technology. Segmental aneuploidies were evaluated when fragment size was > 5 Mb. Blastocysts presenting a single segmental aneuploidy (SSA), without any additional whole-chromosome gain/loss, were statistically analyzed for incidence, type, size and chromosomal emplacement. Segment sizes relative to the whole chromosome or arm (chromosome- and arm-ratios) were also studied. RESULTS 8.4% (299/3565) of blastocysts exhibited segmental aneuploidy for one or more chromosomes, some of which were associated with whole-chromosome aneuploidy while others were not. Nearly half of them (4.5%: 159/3565 of blastocysts) exhibited pure-SSA, meaning that a single chromosome was affected by a SSA. Segments were more frequent in medium-sized metacentric or submetacentric chromosomes and particularly in q-chrmosome arms, variables that were related to trophectoderm quality. SSA size was related to a greater extent to chromosome number and the arm affected than it was to SSA type. In absolute values (Mb), SSA size was larger in large chromosomes. However, the SSA:chromosome ratio was constant across all chromosomes and never exceeded 50% of the chromosome. CONCLUSIONS SSA frequency is chromosome- and topographically dependent, and its incidence is not related to clinical or embryological factors, but rather to trophectoderm quality. SSA might be originated by chromosome instability in response to chromothripsis, bias introduced by the biopsy and/or iatrogenic effects. TRIAL REGISTRATION Retrospectively registered.
Collapse
Affiliation(s)
| | - Xavier Vendrell
- Reproductive Genetics Unit, Sistemas Genómicos, Parque Tecnológico Paterna, 46980, Valencia, Spain
| | - Vanessa Peinado
- Igenomix, Parque Tecnológico Paterna, 46980, Valencia, Spain
| |
Collapse
|
45
|
Pellestor F, Gatinois V. Chromoanasynthesis: another way for the formation of complex chromosomal abnormalities in human reproduction. Hum Reprod 2019; 33:1381-1387. [PMID: 30325427 DOI: 10.1093/humrep/dey231] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Indexed: 12/24/2022] Open
Abstract
Chromoanasynthesis has been described as a novel cause of massive constitutional chromosomal rearrangements. Based on DNA replication machinery defects, chromoanasynthesis is characterized by the presence of chromosomal duplications and triplications locally clustered on one single chromosome, or a few chromosomes, associated with various other types of structural rearrangements. Two distinct mechanisms have been described for the formation of these chaotic genomic disorders, i.e. the fork stalling and template switching and the microhomology-mediated break-induced replication. Micronucleus-based processes have been evidenced as a causative mechanism, thus, highlighting the close connection between segregation errors and structural rearrangements. Accumulating data indicate that chromoanasynthesis is operating in human germline cells and during early embryonic development. The development of new tools for quantifying chromoanasynthesis events should provide further insight into the impact of this catastrophic cellular phenomenon in human reproduction.
Collapse
Affiliation(s)
- Franck Pellestor
- Unit of Chromosomal Genetics, Department of Medical Genetics, Arnaud de Villeneuve Hospital, Montpellier CHU, Montpellier, France
| | - Vincent Gatinois
- Unit of Chromosomal Genetics, Department of Medical Genetics, Arnaud de Villeneuve Hospital, Montpellier CHU, Montpellier, France
| |
Collapse
|
46
|
Soto M, Raaijmakers JA, Medema RH. Consequences of Genomic Diversification Induced by Segregation Errors. Trends Genet 2019; 35:279-291. [DOI: 10.1016/j.tig.2019.01.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/11/2019] [Accepted: 01/16/2019] [Indexed: 01/02/2023]
|
47
|
Schneider I, Ellenberg J. Mysteries in embryonic development: How can errors arise so frequently at the beginning of mammalian life? PLoS Biol 2019; 17:e3000173. [PMID: 30840627 PMCID: PMC6422315 DOI: 10.1371/journal.pbio.3000173] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 03/18/2019] [Indexed: 12/21/2022] Open
Abstract
Chromosome segregation errors occur frequently during female meiosis but also in the first mitoses of mammalian preimplantation development. Such errors can lead to aneuploidy, spontaneous abortions, and birth defects. Some of the mechanisms underlying these errors in meiosis have been deciphered but which mechanisms could cause chromosome missegregation in the first embryonic cleavage divisions is mostly a “mystery”. In this article, we describe the starting conditions and challenges of these preimplantation divisions, which might impair faithful chromosome segregation. We also highlight the pending research to provide detailed insight into the mechanisms and regulation of preimplantation mitoses. Starting a new life is a challenging business. This Essay explores the changes at the oocyte-to-embryo transition to highlight the circumstances under which the very first and decisive — but ‘mysteriously’ error-prone — mitotic divisions occur.
Collapse
Affiliation(s)
- Isabell Schneider
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Candidate for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, Heidelberg, Germany
| | - Jan Ellenberg
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- * E-mail:
| |
Collapse
|
48
|
|
49
|
Cell-Size-Independent Spindle Checkpoint Failure Underlies Chromosome Segregation Error in Mouse Embryos. Curr Biol 2019; 29:865-873.e3. [PMID: 30773364 DOI: 10.1016/j.cub.2018.12.042] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 11/23/2018] [Accepted: 12/21/2018] [Indexed: 12/31/2022]
Abstract
Chromosome segregation errors during mammalian preimplantation development cause "mosaic" embryos comprising a mixture of euploid and aneuploid cells, which reduce the potential for a successful pregnancy [1-5], but why these errors are common is unknown. In most cells, chromosome segregation error is averted by the spindle assembly checkpoint (SAC), which prevents anaphase-promoting complex (APC/C) activation and anaphase onset until chromosomes are aligned with kinetochores attached to spindle microtubules [6, 7], but little is known about the SAC's role in the early mammalian embryo. In C. elegans, the SAC is weak in early embryos, and it strengthens during early embryogenesis as a result of progressively lessening cell size [8, 9]. Here, using live imaging, micromanipulation, gene knockdown, and pharmacological approaches, we show that this is not the case in mammalian embryos. Misaligned chromosomes in the early mouse embryo can recruit SAC components to mount a checkpoint signal, but this signal fails to prevent anaphase onset, leading to high levels of chromosome segregation error. We find that failure of the SAC to prolong mitosis is not attributable to cell size. We show that mild chemical inhibition of APC/C can extend mitosis, thereby allowing more time for correct chromosome alignment and reducing segregation errors. SAC-APC/C disconnect thus presents a mechanistic explanation for frequent chromosome segregation errors in early mammalian embryos. Moreover, our data provide proof of principle that modulation of the SAC-APC/C axis can increase the likelihood of error-free chromosome segregation in cultured mammalian embryos.
Collapse
|
50
|
Correlative Live Imaging and Immunofluorescence for Analysis of Chromosome Segregation in Mouse Preimplantation Embryos. Methods Mol Biol 2019; 1769:319-335. [PMID: 29564833 DOI: 10.1007/978-1-4939-7780-2_20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Chromothripsis is a phenomenon observed in cancer cells, wherein a single or few chromosome(s) exhibit vast genomic rearrangements. Recent studies elucidated a striking series of events in which defective segregation of chromosomes causes their incorporation into micronuclei, where they are subject to extensive DNA damage prior to re-joining the main mass of chromosomes in a subsequent cell cycle, which provide an appealing mechanism for the etiology of chromothripsis. Micronuclei are well known to be common in human preimplantation embryos. We recently showed that, unlike in cancer cells, in mouse preimplantation embryos the micronuclei are maintained during multiple cell generations and apparently fail to re-join the main set of chromosomes. This unexpected finding could safeguard the early embryonic genome from chromothripsis. Here, we describe an approach that combines live and immunofluorescence imaging methods that was pivotal in that study to reveal the lack of a functional kinetochore in chromosomes from mouse embryo micronuclei.
Collapse
|