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Liu J, Zhang C. Xenopus cell-free extracts and their applications in cell biology study. BIOPHYSICS REPORTS 2023; 9:195-205. [PMID: 38516620 PMCID: PMC10951473 DOI: 10.52601/bpr.2023.230016] [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: 09/27/2023] [Accepted: 12/05/2023] [Indexed: 03/23/2024] Open
Abstract
Xenopus has proven to be a remarkably versatile model organism in the realm of biological research for numerous years, owing to its straightforward maintenance in laboratory settings and its abundant provision of ample-sized oocytes, eggs, and embryos. The cell cycle of these oocytes, eggs, and early embryos exhibits synchrony, and extracts derived from these cells serve various research purposes. Many fundamental concepts in biochemistry, cell biology, and development have been elucidated through the use of cell-free extracts derived from Xenopus cells. Over the past few decades, a wide array of cell-free extracts has been prepared from oocytes, eggs, and early embryos of different Xenopus species at varying cell cycle stages. Each of these extracts possesses distinct characteristics. This review provides a concise overview of the Xenopus species employed in laboratory research, the diverse types of cell-free extracts available, and their respective properties. Furthermore, this review delves into the extensive investigation of spindle assembly in Xenopus egg extracts, underscoring the versatility and potency of these cell-free systems in the realm of cell biology.
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Affiliation(s)
- Junjun Liu
- Department of Biological Sciences, California State Polytechnic University, Pomona, CA 91768, USA
| | - Chuanmao Zhang
- The Academy for Cell and Life Health, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China
- The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China
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2
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Boettcher S, Simons M. Model organisms for functional validation in genetic renal disease. MED GENET-BERLIN 2022; 34:287-296. [PMID: 38836086 PMCID: PMC11006349 DOI: 10.1515/medgen-2022-2162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Functional validation is key for establishing new disease genes in human genetics. Over the years, model organisms have been utilized in a very effective manner to prove causality of genes or genetic variants for a wide variety of diseases. Also in hereditary renal disease, model organisms are very helpful for functional validation of candidate genes and variants identified by next-generation sequencing strategies and for obtaining insights into the pathophysiology. Due to high genetic conservation as well as high anatomical and physiological similarities with the human kidney, almost all genetic kidney diseases can be studied in the mouse. However, mouse work is time consuming and expensive, so there is a need for alternative models. In this review, we will provide an overview of model organisms used in renal research, focusing on mouse, zebrafish, frog, and fruit flies.
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Affiliation(s)
- Susanne Boettcher
- Sektion Nephrogenetik, Institute of Human Genetics, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Matias Simons
- Sektion Nephrogenetik, Institute of Human Genetics, University Hospital Heidelberg, 69120 Heidelberg, Germany
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3
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Meiosis initiation: a story of two sexes in all creatures great and small. Biochem J 2021; 478:3791-3805. [PMID: 34709374 PMCID: PMC8589329 DOI: 10.1042/bcj20210412] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 09/29/2021] [Accepted: 10/06/2021] [Indexed: 12/22/2022]
Abstract
Meiosis facilitates diversity across individuals and serves as a major driver of evolution. However, understanding how meiosis begins is complicated by fundamental differences that exist between sexes and species. Fundamental meiotic research is further hampered by a current lack of human meiotic cells lines. Consequently, much of what we know relies on data from model organisms. However, contextualising findings from yeast, worms, flies and mice can be challenging, due to marked differences in both nomenclature and the relative timing of meiosis. In this review, we set out to combine current knowledge of signalling and transcriptional pathways that control meiosis initiation across the sexes in a variety of organisms. Furthermore, we highlight the emerging links between meiosis initiation and oncogenesis, which might explain the frequent re-expression of normally silent meiotic genes in a variety of human cancers.
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4
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Distinct roles of XRCC1 in genome integrity in Xenopus egg extracts. Biochem J 2020; 476:3791-3804. [PMID: 31808793 DOI: 10.1042/bcj20190798] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/04/2019] [Accepted: 12/06/2019] [Indexed: 02/06/2023]
Abstract
Oxidative DNA damage represents one of the most abundant DNA lesions. It remains unclear how DNA repair and DNA damage response (DDR) pathways are co-ordinated and regulated following oxidative stress. While XRCC1 has been implicated in DNA repair, it remains unknown how exactly oxidative DNA damage is repaired and sensed by XRCC1. In this communication, we have demonstrated evidence that XRCC1 is dispensable for ATR-Chk1 DDR pathway following oxidative stress in Xenopus egg extracts. Whereas APE2 is essential for SSB repair, XRCC1 is not required for the repair of defined SSB and gapped plasmids with a 5'-OH or 5'-P terminus, suggesting that XRCC1 and APE2 may contribute to SSB repair via different mechanisms. Neither Polymerase beta nor Polymerase alpha is important for the repair of defined SSB structure. Nonetheless, XRCC1 is important for the repair of DNA damage following oxidative stress. Our observations suggest distinct roles of XRCC1 for genome integrity in oxidative stress in Xenopus egg extracts.
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5
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Eastman AE, Guo S. The palette of techniques for cell cycle analysis. FEBS Lett 2020; 594:10.1002/1873-3468.13842. [PMID: 32441778 PMCID: PMC9261528 DOI: 10.1002/1873-3468.13842] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/20/2020] [Accepted: 05/08/2020] [Indexed: 12/13/2022]
Abstract
The cell division cycle is the generational period of cellular growth and propagation. Cell cycle progression needs to be highly regulated to preserve genomic fidelity while increasing cell number. In multicellular organisms, the cell cycle must also coordinate with cell fate specification during development and tissue homeostasis. Altered cell cycle dynamics play a central role also in a number of pathophysiological processes. Thus, extensive effort has been made to define the biochemical machineries that execute the cell cycle and their regulation, as well as implementing more sensitive and accurate cell cycle measurements. Here, we review the available techniques for cell cycle analysis, revisiting the assumptions behind conventional population-based measurements and discussing new tools to better address cell cycle heterogeneity in the single-cell era. We weigh the strengths, weaknesses, and trade-offs of methods designed to measure temporal aspects of the cell cycle. Finally, we discuss emerging techniques for capturing cell cycle speed at single-cell resolution in live animals.
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Affiliation(s)
- Anna E Eastman
- Department of Cell Biology and Yale Stem Cell Center, Yale University, New Haven, CT, USA
| | - Shangqin Guo
- Department of Cell Biology and Yale Stem Cell Center, Yale University, New Haven, CT, USA
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6
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Lin Y, Bai L, Cupello S, Hossain MA, Deem B, McLeod M, Raj J, Yan S. APE2 promotes DNA damage response pathway from a single-strand break. Nucleic Acids Res 2019; 46:2479-2494. [PMID: 29361157 PMCID: PMC5861430 DOI: 10.1093/nar/gky020] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 01/09/2018] [Indexed: 02/06/2023] Open
Abstract
As the most common type of DNA damage, DNA single-strand breaks (SSBs) are primarily repaired by the SSB repair mechanism. If not repaired properly or promptly, unrepaired SSBs lead to genome stability and have been implicated in cancer and neurodegenerative diseases. However, it remains unknown how unrepaired SSBs are recognized by DNA damage response (DDR) pathway, largely because of the lack of a feasible experimental system. Here, we demonstrate evidence showing that an ATR-dependent checkpoint signaling is activated by a defined plasmid-based site-specific SSB structure in Xenopus HSS (high-speed supernatant) system. Notably, the distinct SSB signaling requires APE2 and canonical checkpoint proteins, including ATR, ATRIP, TopBP1, Rad9 and Claspin. Importantly, the SSB-induced ATR DDR is essential for SSB repair. We and others show that APE2 interacts with PCNA via its PIP box and preferentially interacts with ssDNA via its C-terminus Zf–GRF domain, a conserved motif found in >100 proteins involved in DNA/RNA metabolism. Here, we identify a novel mode of APE2–PCNA interaction via APE2 Zf–GRF and PCNA C-terminus. Mechanistically, the APE2 Zf–GRF–PCNA interaction facilitates 3′-5′ SSB end resection, checkpoint protein complex assembly, and SSB-induced DDR pathway. Together, we propose that APE2 promotes ATR–Chk1 DDR pathway from a single-strand break.
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Affiliation(s)
- Yunfeng Lin
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Liping Bai
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Steven Cupello
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Md Akram Hossain
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Bradley Deem
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Melissa McLeod
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Jude Raj
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Shan Yan
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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7
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Hardwick LJA, Philpott A. Xenopus Models of Cancer: Expanding the Oncologist's Toolbox. Front Physiol 2018; 9:1660. [PMID: 30538639 PMCID: PMC6277521 DOI: 10.3389/fphys.2018.01660] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/02/2018] [Indexed: 01/06/2023] Open
Abstract
The use of the Xenopus model system has provided diverse contributions to cancer research, not least because of the striking parallels between tumour pathogenesis and early embryo development. Cell cycle regulation, signalling pathways, and cell behaviours such as migration are frequently perturbed in cancers; all have been investigated using Xenopus, and these developmental events can additionally act as an assay for drug development studies. In this mini-review, we focus our discussion primarily on whole embryo Xenopus models informing cancer biology; the contributions to date and future potential. Insights into tumour immunity, oncogene function, and visualisation of vascular responses during tumour formation have all been achieved with naturally occurring tumours and induced-tumour-like-structures in Xenopus. Finally, as we are now entering the era of genetically modified Xenopus models, we can harness genome editing techniques to recapitulate human disease through creating embryos with analogous genetic abnormalities. With the speed, versatility and accessibility that epitomise the Xenopus system, this new range of pre-clinical Xenopus models has great potential to advance our mechanistic understanding of oncogenesis and provide an early in vivo model for chemotherapeutic development.
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Affiliation(s)
- Laura J A Hardwick
- Philpott Lab, Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Cambridge, United Kingdom.,Wellcome MRC Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.,Peterhouse, University of Cambridge, Cambridge, United Kingdom
| | - Anna Philpott
- Philpott Lab, Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Cambridge, United Kingdom.,Wellcome MRC Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
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8
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Cupello S, Richardson C, Yan S. Cell-free Xenopus egg extracts for studying DNA damage response pathways. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2018; 60:229-236. [PMID: 27160070 DOI: 10.1387/ijdb.160113sy] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In response to a variety of DNA replication stress or DNA damaging agents, the DNA damage response (DDR) pathways are triggered for cells to coordinate DNA repair, cell cycle checkpoints, apoptosis, and senescence. Cell-free Xenopus egg extracts, derived from the eggs of African clawed frogs (Xenopus laevis), have been widely used for studies concerning DDR pathways. In this review, we focus on how different experimental systems have been established using Xenopus egg extracts to investigate the DDR pathways that are activated in response to DNA replication stress, double-strand breaks (DSBs), inter-strand crosslinks (ICLs), and oxidative stress. We summarize how molecular details of DDR pathways are dissected by the mechanistic studies with Xenopus egg extracts. We also provide an update on the regulation of translesion DNA synthesis (TLS) polymerases (Pol ĸ and REV1) in the DDR pathways. A better understanding of DDR pathways using Xenopus egg extracts has opened new avenues for future cancer therapeutics. Finally, we offer our perspectives of future directions for studies of DDR pathways with Xenopus egg extracts.
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Affiliation(s)
- Steven Cupello
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, USA
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9
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Stooke-Vaughan GA, Davidson LA, Woolner S. Xenopus as a model for studies in mechanical stress and cell division. Genesis 2017; 55. [PMID: 28095623 DOI: 10.1002/dvg.23004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 11/17/2016] [Accepted: 11/17/2016] [Indexed: 01/03/2023]
Abstract
We exist in a physical world, and cells within biological tissues must respond appropriately to both environmental forces and forces generated within the tissue to ensure normal development and homeostasis. Cell division is required for normal tissue growth and maintenance, but both the direction and rate of cell division must be tightly controlled to avoid diseases of over-proliferation such as cancer. Recent studies have shown that mechanical cues can cause mitotic entry and orient the mitotic spindle, suggesting that physical force could play a role in patterning tissue growth. However, to fully understand how mechanics guides cells in vivo, it is necessary to assess the interaction of mechanical strain and cell division in a whole tissue context. In this mini-review we first summarise the body of work linking mechanics and cell division, before looking at the advantages that the Xenopus embryo can offer as a model organism for understanding: (1) the mechanical environment during embryogenesis, and (2) factors important for cell division. Finally, we introduce a novel method for applying a reproducible strain to Xenopus embryonic tissue and assessing subsequent cell divisions.
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Affiliation(s)
- Georgina A Stooke-Vaughan
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213.,Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213
| | - Sarah Woolner
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
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10
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Naert T, Van Nieuwenhuysen T, Vleminckx K. TALENs and CRISPR/Cas9 fuel genetically engineered clinically relevant Xenopus tropicalis tumor models. Genesis 2017; 55. [PMID: 28095622 DOI: 10.1002/dvg.23005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 11/18/2016] [Accepted: 11/19/2016] [Indexed: 12/12/2022]
Abstract
The targeted nuclease revolution (TALENs, CRISPR/Cas9) now allows Xenopus researchers to rapidly generate custom on-demand genetic knockout models. These novel methods to perform reverse genetics are unprecedented and are fueling a wide array of human disease models within the aquatic diploid model organism Xenopus tropicalis (X. tropicalis). This emerging technology review focuses on the tools to rapidly generate genetically engineered X. tropicalis models (GEXM), with a focus on establishment of genuine genetic and clinically relevant cancer models. We believe that due to particular advantageous characteristics, outlined within this review, GEXM will become a valuable alternative animal model for modeling human cancer. Furthermore, we provide perspectives of how GEXM will be used as a platform for elucidation of novel therapeutic targets and for preclinical drug validation. Finally, we also discuss some future prospects on how the recent expansions and adaptations of the CRISPR/Cas9 toolbox might influence and push forward X. tropicalis cancer research.
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Affiliation(s)
- Thomas Naert
- Developmental Biology Unit, Department of Biomedical Molecular Biology, Ghent University, Belgium
| | - Tom Van Nieuwenhuysen
- Developmental Biology Unit, Department of Biomedical Molecular Biology, Ghent University, Belgium
| | - Kris Vleminckx
- Developmental Biology Unit, Department of Biomedical Molecular Biology, Ghent University, Belgium.,Center for Medical Genetics, Ghent University and Ghent University Hospital, Belgium
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11
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Azzarelli R, Hurley C, Sznurkowska MK, Rulands S, Hardwick L, Gamper I, Ali F, McCracken L, Hindley C, McDuff F, Nestorowa S, Kemp R, Jones K, Göttgens B, Huch M, Evan G, Simons BD, Winton D, Philpott A. Multi-site Neurogenin3 Phosphorylation Controls Pancreatic Endocrine Differentiation. Dev Cell 2017; 41:274-286.e5. [PMID: 28457793 PMCID: PMC5425251 DOI: 10.1016/j.devcel.2017.04.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 03/10/2017] [Accepted: 04/04/2017] [Indexed: 12/02/2022]
Abstract
The proneural transcription factor Neurogenin3 (Ngn3) plays a critical role in pancreatic endocrine cell differentiation, although regulation of Ngn3 protein is largely unexplored. Here we demonstrate that Ngn3 protein undergoes cyclin-dependent kinase (Cdk)-mediated phosphorylation on multiple serine-proline sites. Replacing wild-type protein with a phosphomutant form of Ngn3 increases α cell generation, the earliest endocrine cell type to be formed in the developing pancreas. Moreover, un(der)phosphorylated Ngn3 maintains insulin expression in adult β cells in the presence of elevated c-Myc and enhances endocrine specification during ductal reprogramming. Mechanistically, preventing multi-site phosphorylation enhances both Ngn3 stability and DNA binding, promoting the increased expression of target genes that drive differentiation. Therefore, multi-site phosphorylation of Ngn3 controls its ability to promote pancreatic endocrine differentiation and to maintain β cell function in the presence of pro-proliferation cues and could be manipulated to promote and maintain endocrine differentiation in vitro and in vivo.
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Affiliation(s)
- Roberta Azzarelli
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Christopher Hurley
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Cancer Research UK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
| | - Magdalena K Sznurkowska
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Steffen Rulands
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany; Center for Systems Biology Dresden, Pfotenhauer Straße 108, 01307 Dresden, Germany
| | - Laura Hardwick
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Ivonne Gamper
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Fahad Ali
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Laura McCracken
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Christopher Hindley
- The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK; Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK
| | - Fiona McDuff
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Sonia Nestorowa
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK; Department of Haematology, Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 0XY, UK
| | - Richard Kemp
- Cancer Research UK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
| | - Kenneth Jones
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - Berthold Göttgens
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK; Department of Haematology, Cambridge Institute for Medical Research, Hills Road, Cambridge CB2 0XY, UK
| | - Meritxell Huch
- The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK
| | - Gerard Evan
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Benjamin D Simons
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK; The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK; Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK
| | - Douglas Winton
- Cancer Research UK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
| | - Anna Philpott
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK.
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12
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Raspelli E, Falbo L, Costanzo V. Xenopus egg extract to study regulation of genome-wide and locus-specific DNA replication. Genesis 2017; 55. [PMID: 28095613 DOI: 10.1002/dvg.22996] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 11/10/2016] [Accepted: 11/10/2016] [Indexed: 11/10/2022]
Abstract
Faithful DNA replication, coupled with accurate repair of DNA damage, is essential to maintain genome stability and relies on different DNA metabolism genes. Many of these genes are involved in the assembly of replication origins, in the coordination of DNA repair to protect replication forks progression in the presence of DNA damage and in the replication of repetitive chromatin regions. Some DNA metabolism genes are essential in higher eukaryotes, suggesting the existence of specialized mechanisms of repair and replication in organisms with complex genomes. The impact on cell survival of many of these genes has so far precluded in depth molecular analysis of their function. The cell-free Xenopus laevis egg extract represents an ideal system to overcome survival issues and to facilitate the biochemical study of replication-associated functions of essential proteins in vertebrate organisms. Here, we will discuss how Xenopus egg extracts have been used to study cellular and molecular processes, such as DNA replication and DNA repair. In particular, we will focus on innovative imaging and proteomic-based experimental approaches to characterize the molecular function of a number of essential DNA metabolism factors involved in the duplication of complex vertebrate genomes.
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Affiliation(s)
- Erica Raspelli
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
| | - Lucia Falbo
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
| | - Vincenzo Costanzo
- DNA metabolism laboratory, IFOM, The FIRC institute for Molecular Oncology, Milan, Italy
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13
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Gómez R, Van Damme K, Gosálvez J, Morán ES, Colbourne JK. Male meiosis in Crustacea: synapsis, recombination, epigenetics and fertility in Daphnia magna. Chromosoma 2015; 125:769-87. [PMID: 26685998 PMCID: PMC5023733 DOI: 10.1007/s00412-015-0558-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 10/28/2015] [Accepted: 11/09/2015] [Indexed: 11/28/2022]
Abstract
We present the first detailed cytological study of male meiosis in Daphnia (Crustacea: Branchiopoda: Cladocera)—an aquatic microcrustacean with a cyclical parthenogenetic life cycle. Using immunostaining of the testes in Daphnia magna for baseline knowledge, we characterized the different stages of meiotic division and spermiogenesis in relation to the distribution of proteins involved in synapsis, early recombination events and sister chromatid cohesion. We also studied post-translational histone modifications in male spermatocytes, in relation to the dynamic chromatin progression of meiosis. Finally, we applied a DNA fragmentation test to measure sperm quality of D. magna, with respect to levels of inbreeding. As a proxy for fertility, this technique may be used to assess the reproductive health of a sentinel species of aquatic ecosystems. Daphnia proves to be a model species for comparative studies of meiosis that is poised to improve our understanding of the cytological basis of sexual and asexual reproduction.
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Affiliation(s)
- Rocío Gómez
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049, Madrid, Spain. .,Environmental Genomics Group. School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK. .,Chromosome Dynamics Group. School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK.
| | - Kay Van Damme
- Environmental Genomics Group. School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - Jaime Gosálvez
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049, Madrid, Spain
| | - Eugenio Sánchez Morán
- Chromosome Dynamics Group. School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - John K Colbourne
- Environmental Genomics Group. School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK
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14
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Walrant A, Saxton DS, Correia GP, Gallop JL. Triggering actin polymerization in Xenopus egg extracts from phosphoinositide-containing lipid bilayers. Methods Cell Biol 2015; 128:125-47. [PMID: 25997346 DOI: 10.1016/bs.mcb.2015.01.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Xenopus egg extracts are a powerful tool to reconstitute complex cell biological processes using a cell-free strategy. When used in conjunction with liposomes and supported lipid bilayers, they can recapitulate the biochemical activities occurring at the cytosol/plasma membrane interface of the cell that underlie remodeling of the actin cytoskeleton. We use these in vitro systems to elucidate how membranes and proteins collaborate to make the appropriate actin structure at a given time and place. We have recently broadened the types of membrane substrate used, and also optimized protocols for preparation of Xenopus egg extracts for actin assembly assays from membranes. Tuning the lipid composition and curvature appropriately demands an appreciation of the native phospholipid and curvature environments that can form transiently in cells. Supported lipid bilayers on glass coverslips that contain phosphatidylserine and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) make actin bundles termed filopodia-like structures that contain fascin and have vasodilator-stimulated phosphoprotein (VASP) at their growing tips, indicating that these resemble filopodia growing from the plasma membrane. The combination of PI(4,5)P2 and phosphatidylinositol 3-phosphate in curved liposomes or supported bilayers on glass nanospheres uses Snx9, Cdc42, N-WASP (neuronal-Wiskott-Aldrich syndrome protein), and Arp2/3 complex for actin polymerization suggesting that this membrane may mimic the progression from plasma membrane to endosomes. Here we describe how to prepare high-speed supernatant frog egg extracts and phosphoinositide-containing liposomes and supported lipid bilayers that can assemble actin structures. We also describe the methods we use to assay actin polymerization using microscopy and spectrofluorometry and our protocol for immunodepleting specific proteins from extracts.
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Affiliation(s)
- Astrid Walrant
- Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Daniel S Saxton
- Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Guilherme Pereira Correia
- Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Jennifer L Gallop
- Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
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15
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Hardwick LJA, Philpott A. An oncologist׳s friend: How Xenopus contributes to cancer research. Dev Biol 2015; 408:180-7. [PMID: 25704511 PMCID: PMC4684227 DOI: 10.1016/j.ydbio.2015.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 01/27/2015] [Accepted: 02/10/2015] [Indexed: 01/10/2023]
Abstract
One of the most striking features of the Xenopus system is the versatility in providing a unique range of both in vitro and in vivo models that are rapid, accessible and easily manipulated. Here we present an overview of the diverse contribution that Xenopus has made to advance our understanding of tumour biology and behaviour; a contribution that goes beyond the traditional view of Xenopus as a developmental model organism. From the utility of the egg and oocyte extract system to the use of whole embryos as developmental or induced tumour models, the Xenopus system has been fundamental to investigation of cell cycle mechanisms, cell metabolism, cell signalling and cell behaviour, and has allowed an increasing appreciation of the parallels between early development and the pathogenesis of tumour progression and metastasis. Although not the prototypical oncological model system, we propose that Xenopus is an adaptable and multifunctional tool in the oncologist׳s arsenal.
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Affiliation(s)
- Laura J A Hardwick
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK
| | - Anna Philpott
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK.
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16
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Ali FR, Cheng K, Kirwan P, Metcalfe S, Livesey FJ, Barker RA, Philpott A. The phosphorylation status of Ascl1 is a key determinant of neuronal differentiation and maturation in vivo and in vitro. Development 2014; 141:2216-24. [DOI: 10.1242/dev.106377] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Generation of neurons from patient fibroblasts using a combination of developmentally defined transcription factors has great potential in disease modelling, as well as ultimately for use in regeneration and repair. However, generation of physiologically mature neurons in vitro remains problematic. Here we demonstrate the cell-cycle-dependent phosphorylation of a key reprogramming transcription factor, Ascl1, on multiple serine-proline sites. This multisite phosphorylation is a crucial regulator of the ability of Ascl1 to drive neuronal differentiation and maturation in vivo in the developing embryo; a phosphomutant form of Ascl1 shows substantially enhanced neuronal induction activity in Xenopus embryos. Mechanistically, we see that this un(der)phosphorylated Ascl1 is resistant to inhibition by both cyclin-dependent kinase activity and Notch signalling, both of which normally limit its neurogenic potential. Ascl1 is a central component of reprogramming transcription factor cocktails to generate neurons from human fibroblasts; the use of phosphomutant Ascl1 in place of the wild-type protein significantly promotes neuronal maturity after human fibroblast reprogramming in vitro. These results demonstrate that cell-cycle-dependent post-translational modification of proneural proteins directly regulates neuronal differentiation in vivo during development, and that this regulatory mechanism can be harnessed to promote maturation of neurons obtained by transdifferentiation of human cells in vitro.
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Affiliation(s)
- Fahad R. Ali
- University of Cambridge, Department of Oncology, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge CB2 0PY, UK
| | - Kevin Cheng
- University of Cambridge, Department of Oncology, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK
| | - Peter Kirwan
- Gurdon Institute, Department of Biochemistry and Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Su Metcalfe
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge CB2 0PY, UK
| | - Frederick J. Livesey
- Gurdon Institute, Department of Biochemistry and Cambridge Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Roger A. Barker
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge CB2 0PY, UK
| | - Anna Philpott
- University of Cambridge, Department of Oncology, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK
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17
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Segota I, Boulet L, Franck D, Franck C. Spontaneous emergence of large-scale cell cycle synchronization in amoeba colonies. Phys Biol 2014; 11:036001. [PMID: 24732749 DOI: 10.1088/1478-3975/11/3/036001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Unicellular eukaryotic amoebae Dictyostelium discoideum are generally believed to grow in their vegetative state as single cells until starvation, when their collective aspect emerges and they differentiate to form a multicellular slime mold. While major efforts continue to be aimed at their starvation-induced social aspect, our understanding of population dynamics and cell cycle in the vegetative growth phase has remained incomplete. Here we show that cell populations grown on a substrate spontaneously synchronize their cell cycles within several hours. These collective population-wide cell cycle oscillations span millimeter length scales and can be completely suppressed by washing away putative cell-secreted signals, implying signaling by means of a diffusible growth factor or mitogen. These observations give strong evidence for collective proliferation behavior in the vegetative state.
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Affiliation(s)
- Igor Segota
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA
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18
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Zhu XN, Kim DH, Lin HR, Budhavarapu VN, Rosenbaum HB, Mueller PR, Yew PR. Proteolysis of Xenopus Cip-type CDK inhibitor, p16Xic2, is regulated by PCNA binding and CDK2 phosphorylation. Cell Div 2013; 8:5. [PMID: 23607668 PMCID: PMC3655096 DOI: 10.1186/1747-1028-8-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 04/17/2013] [Indexed: 11/10/2022] Open
Abstract
Background Cell division is positively regulated by cyclin-dependent kinases (CDKs) partnered with cyclins and negatively regulated by CDK inhibitors. In the frog, Xenopus laevis, three types of CDK inhibitors have been described: p27Xic1 (Xic1) which shares sequence homology with both p21Cip1 and p27Kip1 from mammals, p16Xic2 (Xic2) which shares sequence homology with p21Cip1, and p17Xic3 (Xic3) which shares sequence homology with p27Kip1. While past studies have demonstrated that during DNA polymerase switching, Xic1 is targeted for protein turnover dependent upon DNA, Proliferating Cell Nuclear Antigen (PCNA), and the ubiquitin ligase CRL4Cdt2, little is known about the processes that regulate Xic2 or Xic3. Methods We used the Xenopus interphase egg extract as a model system to examine the regulation of Xic2 by proteolysis and phosphorylation. Results Our studies indicated that following primer synthesis during the initiation of DNA replication, Xic2 is targeted for DNA- and PCNA-dependent ubiquitin-mediated proteolysis and that Cdt2 can promote Xic2 turnover. Additionally, during interphase, Xic2 is phosphorylated by CDK2 at Ser-98 and Ser-131 in a DNA-independent manner, inhibiting Xic2 turnover. In the presence of double-stranded DNA ends, Xic2 is also phosphorylated at Ser-78 and Ser-81 by a caffeine-sensitive kinase, but this phosphorylation does not alter Xic2 turnover. Conversely, in the presence or absence of DNA, Xic3 was stable in the Xenopus interphase egg extract and did not exhibit a shift indicative of phosphorylation. Conclusions During interphase, Xic2 is targeted for DNA- and PCNA-dependent proteolysis that is negatively regulated by CDK2 phosphorylation. During a response to DNA damage, Xic2 may be alternatively regulated by phosphorylation by a caffeine-sensitive kinase. Our studies suggest that the three types of Xenopus CDK inhibitors, Xic1, Xic2, and Xic3 appear to be uniquely regulated which may reflect their specialized roles during cell division or early development in the frog.
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Affiliation(s)
- Xi-Ning Zhu
- Department of Molecular Medicine, Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
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19
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Yasutis KM, Kozminski KG. Cell cycle checkpoint regulators reach a zillion. Cell Cycle 2013; 12:1501-9. [PMID: 23598718 DOI: 10.4161/cc.24637] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Entry into mitosis is regulated by a checkpoint at the boundary between the G2 and M phases of the cell cycle (G2/M). In many organisms, this checkpoint surveys DNA damage and cell size and is controlled by both the activation of mitotic cyclin-dependent kinases (Cdks) and the inhibition of an opposing phosphatase, protein phosphatase 2A (PP2A). Misregulation of mitotic entry can often lead to oncogenesis or cell death. Recent research has focused on discovering the signaling pathways that feed into the core checkpoint control mechanisms dependent on Cdk and PP2A. Herein, we review the conserved mechanisms of the G2/M transition, including recently discovered upstream signaling pathways that link cell growth and DNA replication to cell cycle progression. Critical consideration of the human, frog and yeast models of mitotic entry frame unresolved and emerging questions in this field, providing a prediction of signaling molecules and pathways yet to be discovered.
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20
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Cerdà J, Zapater C, Chauvigné F, Finn RN. Water homeostasis in the fish oocyte: new insights into the role and molecular regulation of a teleost-specific aquaporin. FISH PHYSIOLOGY AND BIOCHEMISTRY 2013; 39:19-27. [PMID: 22278707 DOI: 10.1007/s10695-012-9608-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 01/17/2012] [Indexed: 05/31/2023]
Abstract
The discovery of the role of a teleost-specific aquaporin (Aqp1ab) during the process of oocyte hydration in marine fish producing pelagic (floating) eggs, recently confirmed by molecular approaches, has revealed that this mechanism is more sophisticated than initially thought. Recent phylogenetic and genomic studies suggest that Aqp1ab likely evolved by tandem duplication from a common ancestor and further neofunctionalized in oocytes for water transport. Investigations into the regulation of Aqp1ab during oogenesis indicate that the mRNA and protein product are highly accumulated during early oocyte growth, possibly through the transcriptional activation of the aqp1ab promoter by the classical nuclear progesterone receptor and perhaps by Sry-related high mobility group [HMG]-box (Sox) transcription factors. During oocyte growth and maturation, Aqp1ab intracellular trafficking may be regulated by phosphorylation and/or dephosphorylation of specific C-terminal residues in Aqp1ab, as well as by signal-mediated sorting processes. These mechanisms possibly regulate the temporal insertion of Aqp1ab into the oocyte plasma membrane during oocyte hydration, although the intracellular signaling pathways involved are yet unknown. Interestingly, in some freshwater species that spawn partially hydrated eggs, high accumulation of transcripts encoding functional Aqp1ab channels have also been found in the ovary. These findings suggest that the Aqp1ab-mediated mechanism for oocyte hydration is likely conserved in teleosts. The tight regulation of Aqp1ab during oogenesis, at both the transcriptional and posttranslational levels, highlights the essential physiological role of this water channel and opens new research avenues for understanding the molecular basis of egg formation in fish.
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Affiliation(s)
- J Cerdà
- Laboratory of Institut de Recerca i Tecnologia Agroalimentàries-Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, 08003, Barcelona, Spain.
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21
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Huang TL, Pian JP, Pan BT. Oncogenic Ras suppresses Cdk1 in a complex manner during the incubation of activated Xenopus egg extracts. Arch Biochem Biophys 2013; 532:61-72. [PMID: 23376039 DOI: 10.1016/j.abb.2013.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 01/12/2013] [Accepted: 01/18/2013] [Indexed: 12/30/2022]
Abstract
The activity of Cdk1 is the driving force for entry into M-phase during the cell cycle. Activation of Cdk1 requires synthesis and accumulation of cyclin B, binding of cyclin B to Cdk1, and removal of the inhibitory tyr-15-Cdk1 phosphorylation. It was previously shown that oncogenic Ras suppresses Cdk1 activation during the incubation of activated Xenopus egg extracts. However, how oncogenic Ras suppresses Cdk1 remained unclear. Using the histone H1 kinase assay to follow Cdk1 activity and Western blot analysis to assess levels of both cyclin B2 and phosphorylated-tyr-15-Cdk1, how oncogenic Ras suppresses Cdk1 is studied. The results indicate that oncogenic Ras suppresses Cdk1 via induction of persistent phosphorylation of tyr-15-Cdk1. Interestingly, the results reveal that, compared with cyclin B2 in control activated egg extracts, which increased, peaked and then declined during the incubation, oncogenic Ras induced continuous accumulation of cyclin B2. The results also indicate that oncogenic Ras induces continuous accumulation of cyclin B2 primarily through stabilization of cyclin B2, which is mediated by constitutive activation of the Raf-Mek-Erk-p90(rsk) pathway. Taken together, these results indicate that oncogenic Ras suppresses Cdk1 in a complex manner: It induces continuous accumulation of cyclin B2, but also causes persistent inhibitory phosphorylation of tyr-15-Cdk1.
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Affiliation(s)
- Tun-Lan Huang
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA
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22
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Seah MKY, Holt JE, García-Higuera I, Moreno S, Jones KT. The Anaphase-Promoting Complex activator Fizzy-Related-1 (FZR1) is involved in the establishment of a single mitotic spindle in 1-cell embryos and in the mitotic divisions of early mammalian embryos. J Cell Sci 2012; 125:6030-7. [DOI: 10.1242/jcs.110155] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In early embryos of a number of species the Anaphase-Promoting Complex (APC), an important cell cycle regulator, requires only CDC20 for cell division. In contrast FZR1, a non-essential gene in many cell types, is thought to play a role in APC activation at later cell cycles, and especially in endoreplication. In keeping with this, FZR1 knockout mouse embryos show normal preimplantation development but die due to a lack of endoreplication needed for placentation. However, interpretation of the role of FZR1 during this period is hindered by the presence of maternal stores. Here, therefore, we used an oocyte-specific knockout to examine FZR1 function in early mouse embryo development. Maternal FZR1 was not critical for completion of meiosis, and furthermore viable pups were born to these females mated with normal males. However, in early embryos the absence of both maternal and paternal FZR1 led to a dramatic loss in genome integrity, such that the majority of embryos arrested having undergone only a single mitotic division and contained many γ-H2AX foci, consistent with fragmented DNA. A prominent feature of such embryos was a the establishment of two independent spindles following pronuclear fusion and thus a failure of the chromosomes to mix (syngamy). These generated binucleate 2-cell embryos. In the 10% of embryos that progressed to the 4-cell stage, division was so slow that compaction occurred prematurely. No embryo development to the blastocyst stage was ever observed. We conclude that FZR1 is a surprisingly essential gene involved in the establishment of a single spindle from the two pronuclei in 1-cell embryos as well as being involved in the maintainence of genomic integrity during the mitotic divisions of early mammalian embryos.
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23
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Tokmakov AA, Iguchi S, Iwasaki T, Fukami Y. Unfertilized frog eggs die by apoptosis following meiotic exit. BMC Cell Biol 2011; 12:56. [PMID: 22195698 PMCID: PMC3268744 DOI: 10.1186/1471-2121-12-56] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 12/23/2011] [Indexed: 12/13/2022] Open
Abstract
Background A characteristic feature of frog reproduction is external fertilization accomplished outside the female's body. Mature fertilization-competent frog eggs are arrested at the meiotic metaphase II with high activity of the key meiotic regulators, maturation promoting factor (MPF) and cytostatic factor (CSF), awaiting fertilization. If the eggs are not fertilized within several hours of ovulation, they deteriorate and ultimately die by as yet unknown mechanism. Results Here, we report that the vast majority of naturally laid unfertilized eggs of the African clawed frog Xenopus laevis spontaneously exit metaphase arrest under various environmental conditions and degrade by a well-defined apoptotic process within 48 hours after ovulation. The main features of this process include cytochrome c release, caspase activation, ATP depletion, increase of ADP/ATP ratio, apoptotic nuclear morphology, progressive intracellular acidification, and egg swelling. Meiotic exit seems to be a prerequisite for execution of the apoptotic program, since (i) it precedes apoptosis, (ii) apoptotic events cannot be observed in the eggs maintaining high activity of MPF and CSF, and (iii) apoptosis in unfertilized frog eggs is accelerated upon early meiotic exit. The apoptotic features cannot be observed in the immature prophase-arrested oocytes, however, the maturation-inducing hormone progesterone renders oocytes susceptible to apoptosis. Conclusions The study reveals that naturally laid intact frog eggs die by apoptosis if they are not fertilized. A maternal apoptotic program is evoked in frog oocytes upon maturation and executed after meiotic exit in unfertilized eggs. The meiotic exit is required for execution of the apoptotic program in eggs. The emerging anti-apoptotic role of meiotic metaphase arrest needs further investigation.
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Affiliation(s)
- Alexander A Tokmakov
- Research Center for Environmental Genomics, Kobe University, Rokko dai 1-1, Nada, Kobe, Japan.
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24
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Gotoh T, Villa LM, Capelluto DGS, Finkielstein CV. Regulatory pathways coordinating cell cycle progression in early Xenopus development. Results Probl Cell Differ 2011; 53:171-99. [PMID: 21630146 DOI: 10.1007/978-3-642-19065-0_9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The African clawed frog, Xenopus laevis, is used extensively as a model organism for studying both cell development and cell cycle regulation. For over 20 years now, this model organism has contributed to answering fundamental questions concerning the mechanisms that underlie cell cycle transitions--the cellular components that synthesize, modify, repair, and degrade nucleic acids and proteins, the signaling pathways that allow cells to communicate, and the regulatory pathways that lead to selective expression of subsets of genes. In addition, the remarkable simplicity of the Xenopus early cell cycle allows for tractable manipulation and dissection of the basic components driving each transition. In this organism, early cell divisions are characterized by rapid cycles alternating phases of DNA synthesis and division. The post-blastula stages incorporate gap phases, lengthening progression, and allowing more time for DNA repair. Various cyclin/Cdk complexes are differentially expressed during the early cycles with orderly progression being driven by both the combined action of cyclin synthesis and degradation and the appropriate selection of specific substrates by their Cdk components. Like other multicellular organisms, chief developmental events in early Xenopus embryogenesis coincide with profound remodeling of the cell cycle, suggesting that cell proliferation and differentiation events are linked and coordinated through crosstalk mechanisms acting on signaling pathways involving the expression of cell cycle control genes.
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Affiliation(s)
- Tetsuya Gotoh
- Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, 1981 Kraft Drive, Blacksburg, VA 24061, USA
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25
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McIsaac RS, Huang KC, Sengupta A, Wingreen NS. Does the potential for chaos constrain the embryonic cell-cycle oscillator? PLoS Comput Biol 2011; 7:e1002109. [PMID: 21779158 PMCID: PMC3136431 DOI: 10.1371/journal.pcbi.1002109] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Accepted: 05/14/2011] [Indexed: 11/24/2022] Open
Abstract
Although many of the core components of the embryonic cell-cycle network have been elucidated, the question of how embryos achieve robust, synchronous cellular divisions post-fertilization remains unexplored. What are the different schemes that could be implemented by the embryo to achieve synchronization? By extending a cell-cycle model previously developed for embryos of the frog Xenopus laevis to include the spatial dimensions of the embryo, we establish a novel role for the rapid, fertilization-initiated calcium wave that triggers cell-cycle oscillations. Specifically, in our simulations a fast calcium wave results in synchronized cell cycles, while a slow wave results in full-blown spatio-temporal chaos. We show that such chaos would ultimately lead to an unpredictable patchwork of cell divisions across the embryo. Given this potential for chaos, our results indicate a novel design principle whereby the fast calcium-wave trigger following embryo fertilization synchronizes cell divisions. Cell divisions across an embryo occur in rapid synchrony - like clockwork - starting within minutes of fertilization. How does an embryo achieve this remarkable uniformity? Simple diffusion is too slow: typical proteins diffuse with a rate of 10 µm2/s, requiring nearly 14 hours to traverse a 1 mm embryo. An exciting idea is that the embryo is an active medium, much like the heart where pulses of electrical activity result in organized contractions. However, just as the heart can have arrhythmias, our model predicts that oscillations in the embryo can become chaotic. What would be the biological consequences of this behavior? How do embryos avoid chaos? Our work provides potential answers to these questions: Chaos would lead to an unpredictable patchwork of cell divisions across the embryo - clearly a fatal defect in development. To avoid chaos then, we predict that cell-cycle oscillations need to be triggered throughout the embryo at almost precisely the same time. The threat that chaos will mar development therefore explains the mystery of why embryos universally employ a fast calcium wave to trigger cell-cycle oscillations. In this way, developing organisms get the synchronizing benefits of an active medium without suffering the destructive consequences of chaotic arrhythmias.
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Affiliation(s)
- R. Scott McIsaac
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- Graduate Program in Quantitative and Computational Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Anirvan Sengupta
- Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey, United States of America
- BioMAPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey, United States of America
| | - Ned S. Wingreen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
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26
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Zapater C, Chauvigné F, Norberg B, Finn RN, Cerdà J. Dual neofunctionalization of a rapidly evolving aquaporin-1 paralog resulted in constrained and relaxed traits controlling channel function during meiosis resumption in teleosts. Mol Biol Evol 2011; 28:3151-69. [PMID: 21653921 DOI: 10.1093/molbev/msr146] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The preovulatory hydration of teleost oocytes is a unique process among vertebrates. The hydration mechanism is most pronounced in marine acanthomorph teleosts that spawn pelagic (floating) eggs; however, the molecular pathway for water influx remains poorly understood. Recently, we revealed that whole-genome duplication (WGD) resulted in teleosts harboring the largest repertoire of molecular water channels in the vertebrate lineage and that a duplicated aquaporin-1 paralog is implicated in the oocyte hydration process. However, the origin and function of the aquaporin-1 paralogs remain equivocal. By integrating the molecular phylogeny with synteny and structural analyses, we show here that the teleost aqp1aa and -1ab paralogs (previously annotated as aqp1a and -1b, respectively) arose by tandem duplication rather than WGD and that the Aqp1ab C-terminus is the most rapidly evolving subdomain within the vertebrate aquaporin superfamily. The functional role of Aqp1ab was investigated in Atlantic halibut, a marine acanthomorph teleost that spawns one of the largest pelagic eggs known. We demonstrate that Aqp1ab is required for full hydration of oocytes undergoing meiotic maturation. We further show that the rapid structural divergence of the C-terminal regulatory domain causes ex vivo loss of function of halibut Aqp1ab when expressed in amphibian oocytes but not in zebrafish or native oocytes. However, by using chimeric constructs of halibut Aqp1aa and -1ab and antisera specifically raised against the C-terminus of Aqp1ab, we found that this cytoplasmic domain regulates in vivo trafficking to the microvillar portion of the oocyte plasma membrane when intraoocytic osmotic pressure is at a maximum. Interestingly, by coinjecting polyA(+) mRNA from postvitellogenic halibut follicles, ex vivo intracellular trafficking of Aqp1ab is rescued in amphibian oocytes. These data reveal that the physiological role of Aqp1ab during meiosis resumption is conserved in teleosts, but the remarkable degeneracy of the cytoplasmic domain has resulted in alternative regulation of the trafficking mechanism.
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Affiliation(s)
- Cinta Zapater
- Laboratory of Institut de Recerca i Tecnologia Agroalimentàries, Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Barcelona, Spain
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27
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Ogura Y, Sakaue-Sawano A, Nakagawa M, Satoh N, Miyawaki A, Sasakura Y. Coordination of mitosis and morphogenesis: role of a prolonged G2 phase during chordate neurulation. Development 2011; 138:577-87. [DOI: 10.1242/dev.053132] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Chordates undergo a characteristic morphogenetic process during neurulation to form a dorsal hollow neural tube. Neurulation begins with the formation of the neural plate and ends when the left epidermis and right epidermis overlying the neural tube fuse to close the neural fold. During these processes, mitosis and the various morphogenetic movements need to be coordinated. In this study, we investigated the epidermal cell cycle in Ciona intestinalis embryos in vivo using a fluorescent ubiquitination-based cell cycle indicator (Fucci). Epidermal cells of Ciona undergo 11 divisions as the embryos progress from fertilization to the tadpole larval stage. We detected a long G2 phase between the tenth and eleventh cell divisions, during which fusion of the left and right epidermis occurred. Characteristic cell shape change and actin filament regulation were observed during the G2 phase. CDC25 is probably a key regulator of the cell cycle progression of epidermal cells. Artificially shortening this G2 phase by overexpressing CDC25 caused precocious cell division before or during neural tube closure, thereby disrupting the characteristic morphogenetic movement. Delaying the precocious cell division by prolonging the S phase with aphidicolin ameliorated the effects of CDC25. These results suggest that the long interphase during the eleventh epidermal cell cycle is required for neurulation.
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Affiliation(s)
- Yosuke Ogura
- Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka 415-0025, Japan
| | - Asako Sakaue-Sawano
- Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198, Japan
- Life Function and Dynamics, ERATO, JST, 2-1 Hirosawa, Wako-city, Saitama 351-0198, Japan
| | - Masashi Nakagawa
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako-gun, Hyogo 678-1297, Japan
| | - Nori Satoh
- Marine Genomics Unit, Okinawa Institute of Science and Technology Promotion Corporation, Uruma, Okinawa 904-2234, Japan
| | - Atsushi Miyawaki
- Laboratory for Cell Function and Dynamics, Advanced Technology Development Group, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-city, Saitama 351-0198, Japan
- Life Function and Dynamics, ERATO, JST, 2-1 Hirosawa, Wako-city, Saitama 351-0198, Japan
| | - Yasunori Sasakura
- Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka 415-0025, Japan
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28
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Horb LD, Horb ME. BrunoL1 regulates endoderm proliferation through translational enhancement of cyclin A2 mRNA. Dev Biol 2010; 345:156-69. [PMID: 20633547 DOI: 10.1016/j.ydbio.2010.07.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 06/12/2010] [Accepted: 07/02/2010] [Indexed: 10/19/2022]
Abstract
Developmental control of proliferation relies on tight regulation of protein expression. Although this has been well studied in early embryogenesis, how the cell cycle is regulated during organogenesis is not well understood. Bruno-Like RNA binding proteins bind to consensus sequences in the 3'UTR of specific mRNAs and repress protein translation, but much of this functional information is derived from studies on mainly two members, Drosophila Bruno and vertebrate BrunoL2 (CUGBP1). There are however, six vertebrate and three Drosophila Bruno family members, but less is known about these other family members, and none have been shown to function in the endoderm. We recently identified BrunoL1 as a dorsal pancreas enriched gene, and in this paper we define BrunoL1 function in Xenopus endoderm development. We find that, in contrast to other Bruno-Like proteins, BrunoL1 acts to enhance rather than repress translation. We demonstrate that BrunoL1 regulates proliferation of endoderm cells through translational control of cyclin A2 mRNA. Specifically BrunoL1 enhanced translation of cyclin A2 through binding consensus Bruno Response Elements (BREs) in its 3'UTR. We compared the ability of other Bruno-Like proteins, both vertebrate and invertebrate, to stimulate translation via the cyclin A2 3'UTR and found that only Drosophila Bru-3 had similar activity. In addition, we also found that both BrunoL1 and Bru-3 enhanced translation of mRNAs containing the 3'UTRs of Drosophila oskar or cyclin A, which have been well characterized to mediate repression. Lastly, we show that it is the Linker region of BrunoL1 that is both necessary and sufficient for this activity. These results are the first example of BRE-dependent translational enhancement and are the first demonstration in vertebrates of Bruno-Like proteins regulating translation through BREs.
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Affiliation(s)
- Lori Dawn Horb
- Laboratory of Molecular Organogenesis, Institut de Recherches Cliniques de Montréal, Montreal, QC, Canada
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Cross MK, Powers MA. Learning about cancer from frogs: analysis of mitotic spindles in Xenopus egg extracts. Dis Model Mech 2010; 2:541-7. [PMID: 19892884 DOI: 10.1242/dmm.002022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The mitotic spindle is responsible for correctly segregating chromosomes during cellular division. Disruption of this process leads to genomic instability in the form of aneuploidy, which can contribute to the development of cancer. Therefore, identification and characterization of factors that are responsible for the assembly and regulation of the spindle are crucial. Not only are these factors often altered in cancer, but they also serve as potential therapeutic targets. Xenopus egg extract is a powerful tool for studying spindle assembly and other cell cycle-related events owing, in large part, to the ease with which protein function can be manipulated in the extract. Importantly, the spindle factors that have been characterized in egg extract are conserved in human spindle assembly. In this review, we explain how the extract is prepared and manipulated to study the function of individual factors in spindle assembly and the spindle checkpoint. Furthermore, we provide examples of several spindle factors that have been defined functionally using the extract system and discuss how these factors are altered in human cancer.
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Affiliation(s)
- Marie K Cross
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
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30
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Fauré A, Thieffry D. Logical modelling of cell cycle control in eukaryotes: a comparative study. MOLECULAR BIOSYSTEMS 2009; 5:1569-81. [PMID: 19763341 DOI: 10.1039/b907562n] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Dynamical modelling is at the core of the systems biology paradigm. However, the development of comprehensive quantitative models is complicated by the daunting complexity of regulatory networks controlling crucial biological processes such as cell division, the paucity of currently available quantitative data, as well as the limited reproducibility of large-scale experiments. In this context, qualitative modelling approaches offer a useful alternative or complementary framework to build and analyse simplified, but still rigorous dynamical models. This point is illustrated here by analysing recent logical models of the molecular network controlling mitosis in different organisms, from yeasts to mammals. After a short introduction covering cell cycle and logical modelling, we compare the assumptions and properties underlying these different models. Next, leaning on their transposition into a common logical framework, we compare their functional structure in terms of regulatory circuits. Finally, we discuss assets and prospects of qualitative approaches for the modelling of the cell cycle.
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Affiliation(s)
- Adrien Fauré
- Aix-Marseille University & INSERM U928-TAGC, Marseille, France.
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31
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Goley ED, Toro E, McAdams HH, Shapiro L. Dynamic chromosome organization and protein localization coordinate the regulatory circuitry that drives the bacterial cell cycle. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2009; 74:55-64. [PMID: 19687139 DOI: 10.1101/sqb.2009.74.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The bacterial cell has less internal structure and genetic complexity than cells of eukaryotic organisms, yet it is a highly organized system that uses both temporal and spatial cues to drive its cell cycle. Key insights into bacterial regulatory programs that orchestrate cell cycle progression have come from studies of Caulobacter crescentus, a bacterium that divides asymmetrically. Three global regulatory proteins cycle out of phase with one another and drive cell cycle progression by directly controlling the expression of 200 cell-cycle-regulated genes. Exploration of this system provided insights into the evolution of regulatory circuits and the plasticity of circuit structure. The temporal expression of the modular subsystems that implement the cell cycle and asymmetric cell division is also coordinated by differential DNA methylation, regulated proteolysis, and phosphorylation signaling cascades. This control system structure has parallels to eukaryotic cell cycle control architecture. Remarkably, the transcriptional circuitry is dependent on three-dimensional dynamic deployment of key regulatory and signaling proteins. In addition, dynamically localized DNA-binding proteins ensure that DNA segregation is coupled to the timing and cellular position of the cytokinetic ring. Comparison to other organisms reveals conservation of cell cycle regulatory logic, even if regulatory proteins, themselves, are not conserved.
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Affiliation(s)
- E D Goley
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
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32
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Kieserman EK, Wallingford JB. In vivo imaging reveals a role for Cdc42 in spindle positioning and planar orientation of cell divisions during vertebrate neural tube closure. J Cell Sci 2009; 122:2481-90. [PMID: 19549689 DOI: 10.1242/jcs.042135] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Specialization of the cell-division process is a common feature of developing embryos, but most studies on vertebrate cell division have focused on cells dividing in culture. Here, we used in vivo four-dimensional confocal microscopy to explore the role of Cdc42 in governing cell division in the developing neural epithelium of Xenopus laevis. We find that Cdc42 is crucial for stable positioning of the metaphase spindle in these cells, but was not required for spindle positioning in epidermal epithelial cells. We also find that divisions in the Xenopus neural plate are planar oriented, and that rotations of mitotic spindles are essential for establishing this orientation. When Cdc42 is disrupted, spindles over-rotate and the final orientation of divisions is changed. Finally, the planar orientation of cell divisions in this tissue seems to be independent of planar cell polarity (PCP) signaling and does not require normal neural morphogenesis. Our data provide new insights into the coordination of cell division and morphogenesis in epithelial cell sheets and reveal novel, cell-type-specific roles for Cdc42 in spindle positioning and spindle orientation.
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Affiliation(s)
- Esther K Kieserman
- Department of Molecular Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA
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Lévy N, Oehlmann M, Delalande F, Nasheuer HP, Van Dorsselaer A, Schreiber V, de Murcia G, Ménissier-de Murcia J, Maiorano D, Bresson A. XRCC1 interacts with the p58 subunit of DNA Pol alpha-primase and may coordinate DNA repair and replication during S phase. Nucleic Acids Res 2009; 37:3177-88. [PMID: 19305001 PMCID: PMC2691816 DOI: 10.1093/nar/gkp144] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Repair of single-stranded DNA breaks before DNA replication is critical in maintaining genomic stability; however, how cells deal with these lesions during S phase is not clear. Using combined approaches of proteomics and in vitro and in vivo protein-protein interaction, we identified the p58 subunit of DNA Pol alpha-primase as a new binding partner of XRCC1, a key protein of the single strand break repair (SSBR) complex. In vitro experiments reveal that the binding of poly(ADP-ribose) to p58 inhibits primase activity by competition with its DNA binding property. Overexpression of the XRCC1-BRCT1 domain in HeLa cells induces poly(ADP-ribose) synthesis, PARP-1 and XRCC1-BRCT1 poly(ADP-ribosyl)ation and a strong S phase delay in the presence of DNA damage. Addition of recombinant XRCC1-BRCT1 to Xenopus egg extracts slows down DNA synthesis and inhibits the binding of PCNA, but not MCM2 to alkylated chromatin, thus indicating interference with the assembly of functional replication forks. Altogether these results suggest a critical role for XRCC1 in connecting the SSBR machinery with the replication fork to halt DNA synthesis in response to DNA damage.
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Affiliation(s)
- Nicolas Lévy
- FRE 3211, Institut de Recherche de l'Ecole de Biotechnologie de Strasbourg, CNRS/Université de Strasbourg, Ecole Supérieure de Biotechnologie de Strasbourg, Boulevard S. Brant, BP 10413, F-67412, Illkirch Cedex, France
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