1
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Pfeffer PL. The first lineage determination in mammals. Dev Biol 2024; 513:12-30. [PMID: 38761966 DOI: 10.1016/j.ydbio.2024.05.011] [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: 12/18/2023] [Revised: 03/15/2024] [Accepted: 05/16/2024] [Indexed: 05/20/2024]
Abstract
This review describes in detail the morphological, cytoskeletal and gene expression events leading to the gene regulatory network bifurcation point of trophoblast and inner cell mass cells in a variety of mammalian preimplantation embryos. The interrelated processes of compaction and polarity establishment are discussed in terms of how they affect YAP/WWTR activity and the location and fate of cells. Comparisons between mouse, human, cattle, pig and rabbit embryos suggest a conserved role for YAP/WWTR signalling in trophoblast induction in eutherian animals though the mechanisms for, and timing of, YAP/WWTR activation differs among species. Downstream targets show further differences, with the trophoblast marker GATA3 being a direct target in all examined mammals, while CDX2-positive and SOX2-negative regulation varies.
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Affiliation(s)
- Peter L Pfeffer
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.
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2
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Azagury M, Buganim Y. Unlocking trophectoderm mysteries: In vivo and in vitro perspectives on human and mouse trophoblast fate induction. Dev Cell 2024; 59:941-960. [PMID: 38653193 DOI: 10.1016/j.devcel.2024.03.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 11/10/2023] [Accepted: 03/18/2024] [Indexed: 04/25/2024]
Abstract
In recent years, the pursuit of inducing the trophoblast stem cell (TSC) state has gained prominence as a compelling research objective, illuminating the establishment of the trophoblast lineage and unlocking insights into early embryogenesis. In this review, we examine how advancements in diverse technologies, including in vivo time course transcriptomics, cellular reprogramming to TSC state, chemical induction of totipotent stem-cell-like state, and stem-cell-based embryo-like structures, have enriched our insights into the intricate molecular mechanisms and signaling pathways that define the mouse and human trophectoderm/TSC states. We delve into disparities between mouse and human trophectoderm/TSC fate establishment, with a special emphasis on the intriguing role of pluripotency in this context. Additionally, we re-evaluate recent findings concerning the potential of totipotent-stem-like cells and embryo-like structures to fully manifest the trophectoderm/trophoblast lineage's capabilities. Lastly, we briefly discuss the potential applications of induced TSCs in pregnancy-related disease modeling.
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Affiliation(s)
- Meir Azagury
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Yosef Buganim
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
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3
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Zhao Y, Zhang M, Liu J, Hu X, Sun Y, Huang X, Li J, Lei L. Nr5a2 ensures inner cell mass formation in mouse blastocyst. Cell Rep 2024; 43:113840. [PMID: 38386558 DOI: 10.1016/j.celrep.2024.113840] [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: 10/10/2023] [Revised: 12/14/2023] [Accepted: 02/05/2024] [Indexed: 02/24/2024] Open
Abstract
Recent studies have elucidated Nr5a2's role in activating zygotic genes during early mouse embryonic development. Subsequent research, however, reveals that Nr5a2 is not critical for zygotic genome activation but is vital for the gene program between the 4- and 8-cell stages. A significant gap exists in experimental evidence regarding its function during the first lineage differentiation's pivotal period. In this study, we observed that approximately 20% of embryos developed to the blastocyst stage following Nr5a2 ablation. However, these blastocysts lacked inner cell mass (ICM), highlighting Nr5a2's importance in first lineage differentiation. Mechanistically, using RNA sequencing and CUT&Tag, we found that Nr5a2 transcriptionally regulates ICM-specific genes, such as Oct4, to establish the pluripotent network. Interference with or overexpression of Nr5a2 in single blastomeres of 2-cell embryos can alter the fate of daughter cells. Our results indicate that Nr5a2 works as a doorkeeper to ensure ICM formation in mouse blastocyst.
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Affiliation(s)
- Yanhua Zhao
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China
| | - Meiting Zhang
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China
| | - Jiqiang Liu
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China
| | - Xinglin Hu
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China
| | - Yuchen Sun
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China
| | - Xingwei Huang
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China
| | - Jingyu Li
- Chongqing Key Laboratory of Human Embryo Engineering, Center for Reproductive Medicine, Women and Children's Hospital of Chongqing Medical University, Chongqing 400010, China.
| | - Lei Lei
- Department of Histology and Embryology, Harbin Medical University, Harbin 150081, China.
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4
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Sakurada K, Ishikawa T. Synthesis of causal and surrogate models by non-equilibrium thermodynamics in biological systems. Sci Rep 2024; 14:1001. [PMID: 38200211 PMCID: PMC10781949 DOI: 10.1038/s41598-024-51426-8] [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: 10/17/2023] [Accepted: 01/04/2024] [Indexed: 01/12/2024] Open
Abstract
We developed a model to represent the time evolution phenomena of life through physics constraints. To do this, we took into account that living organisms are open systems that exchange messages through intracellular communication, intercellular communication and sensory systems, and introduced the concept of a message force field. As a result, we showed that the maximum entropy generation principle is valid in time evolution. Then, in order to explain life phenomena based on this principle, we modelled the living system as a nonlinear oscillator coupled by a message and derived the governing equations. The governing equations consist of two laws: one states that the systems are synchronized when the variation of the natural frequencies between them is small or the coupling strength through the message is sufficiently large, and the other states that the synchronization is broken by the proliferation of biological systems. Next, to simulate the phenomena using data obtained from observations of the temporal evolution of life, we developed an inference model that combines physics constraints and a discrete surrogate model using category theory, and simulated the phenomenon of early embryogenesis using this inference model. The results show that symmetry creation and breaking based on message force fields can be widely used to model life phenomena.
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Affiliation(s)
- Kazuhiro Sakurada
- Department of Extended Intelligence for Medicine, The Ishii-Ishibashi Laboratory, Keio University School of Medicine, Tokyo, Japan.
- Open Systems Information Science Team, Advanced Data Science Project, RIKEN Information R&D and Strategy Headquarters, RIKEN, Tokyo, Japan.
| | - Tetsuo Ishikawa
- Department of Extended Intelligence for Medicine, The Ishii-Ishibashi Laboratory, Keio University School of Medicine, Tokyo, Japan
- Medical Data Mathematical Reasoning Team, Advanced Data Science Project, RIKEN Information R&D and Strategy Headquarters, RIKEN, Yokohama, Japan
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5
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Hawdon A, Geoghegan ND, Mohenska M, Elsenhans A, Ferguson C, Polo JM, Parton RG, Zenker J. Apicobasal RNA asymmetries regulate cell fate in the early mouse embryo. Nat Commun 2023; 14:2909. [PMID: 37253716 DOI: 10.1038/s41467-023-38436-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 05/03/2023] [Indexed: 06/01/2023] Open
Abstract
The spatial sorting of RNA transcripts is fundamental for the refinement of gene expression to distinct subcellular regions. Although, in non-mammalian early embryogenesis, differential RNA localisation presages cell fate determination, in mammals it remains unclear. Here, we uncover apical-to-basal RNA asymmetries in outer blastomeres of 16-cell stage mouse preimplantation embryos. Basally directed RNA transport is facilitated in a microtubule- and lysosome-mediated manner. Yet, despite an increased accumulation of RNA transcripts in basal regions, higher translation activity occurs at the more dispersed apical RNA foci, demonstrated by spatial heterogeneities in RNA subtypes, RNA-organelle interactions and translation events. During the transition to the 32-cell stage, the biased inheritance of RNA transcripts, coupled with differential translation capacity, regulates cell fate allocation of trophectoderm and cells destined to form the pluripotent inner cell mass. Our study identifies a paradigm for the spatiotemporal regulation of post-transcriptional gene expression governing mammalian preimplantation embryogenesis and cell fate.
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Affiliation(s)
- Azelle Hawdon
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Niall D Geoghegan
- Walter and Eliza Hall Institute of Medical Research, Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
| | - Monika Mohenska
- Department of Anatomy and Developmental Biology, Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Clayton, VIC, 3800, Australia
- Adelaide Centre for Epigenetics, University of Adelaide, Adelaide, South Australia, Australia
- South Australian immunoGENomics Cancer Institute, University of Adelaide, Adelaide, South Australia, Australia
| | - Anja Elsenhans
- Department of Biology, University of Duisburg-Essen, Essen, Germany
| | - Charles Ferguson
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Jose M Polo
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
- Department of Anatomy and Developmental Biology, Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Clayton, VIC, 3800, Australia
- Adelaide Centre for Epigenetics, University of Adelaide, Adelaide, South Australia, Australia
- South Australian immunoGENomics Cancer Institute, University of Adelaide, Adelaide, South Australia, Australia
| | - Robert G Parton
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
- Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland, Australia
| | - Jennifer Zenker
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia.
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6
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Lamba A, Zernicka-Goetz M. The role of polarization and early heterogeneities in the mammalian first cell fate decision. Curr Top Dev Biol 2023; 154:169-196. [PMID: 37100517 DOI: 10.1016/bs.ctdb.2023.02.006] [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: 04/28/2023]
Abstract
The first cell fate decision is the process by which cells of an embryo take on distinct lineage identities for the first time, representing the beginning of patterning during development. In mammals, this process separates an embryonic inner cell mass lineage (future new organism) from an extra-embryonic trophectoderm lineage (future placenta), and in the mouse, this is classically attributed to the consequences of apical-basal polarity. The mouse embryo acquires this polarity at the 8-cell stage, indicated by cap-like protein domains on the apical surface of each cell; those cells which retain polarity over subsequent divisions are specified as trophectoderm, and the rest as inner cell mass. Recent research has advanced our knowledge of this process - this review will discuss mechanisms behind the establishment of polarity and distribution of the apical domain, different factors affecting the first cell fate decision including heterogeneities between cells of the very early embryo, and the conservation of developmental mechanisms across species, including human.
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Affiliation(s)
- Adiyant Lamba
- Mammalian Embryo and Stem Cell Group, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Magdalena Zernicka-Goetz
- Mammalian Embryo and Stem Cell Group, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom; Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States.
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7
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Liu W, Chen J, Yang C, Lee KF, Lee YL, Chiu PCN, Zhang Y, Duan YG, Liu K, Yeung WSB. Expression of microRNA let-7 in cleavage embryos modulates cell fate determination and formation of mouse blastocysts†. Biol Reprod 2022; 107:1452-1463. [PMID: 36136742 DOI: 10.1093/biolre/ioac181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 06/30/2022] [Accepted: 09/14/2022] [Indexed: 12/24/2022] Open
Abstract
After fertilization, the zygote undergoes cell division. Up to the 8-cell stage, the blastomeres of mouse preimplantation embryos are morphologically identical. The first cell differentiation starts in the morula leading to the formation of trophectoderm cells and inner cell mass cells of the blastocyst. The regulation of the differentiation event and the formation of blastocysts are not fully known. Lethal-7 (let-7) is a family of evolutionarily conserved microRNAs. Here, we showed that the expression of let-7a and let-7g decreased drastically from the 1-cell stage to the 2-cell stage, remained low up to the 8-cell stage and slightly increased after the morula stage of mouse embryos. The expression of let-7 in the inner cell mass was higher than that in the trophectoderm. Forced expression of let-7a in embryos at the 1-cell and 4-cell stage inhibited blastocyst formation and downregulated the expression of CDX2 but maintained that of OCT4 in the trophectoderm. Forced expression of other let-7 isoforms exhibited similar inhibitory action on blastulation. On the other hand, inhibition of let-7a at the 4-cell stage and the 8-cell stage enhanced blastocyst formation. Co-injection of green fluorescent protein (GFP) mRNA (lineage tracer) with either precursor of let-7a (pre-let-7a) or scramble control into one blastomere of 2-cell embryos showed that ~75% of the resulting blastocysts possessed GFP+ cells in their inner cell mass only. The biased development towards the inner cell mass with forced expression of let-7 was reproduced in 2-cell chimeric embryos consisting of one wildtype blastomere and one GFP mRNA-injected blastomere from another 2-cell embryo carrying a doxycycline-inducible let-7g gene. Bioinformatics analysis indicated that Tead4 was a potential target of let-7. Let-7 bound to the 3'UTR of Tead4 and let-7 forced expression downregulated the expression of Tead4 in mouse blastocysts. Co-injection of Tead4 mRNA partially nullified the modulatory roles of let-7a in the inner cell mass cell fate. In conclusion, a high level of let-7 at the 2-cell stage favored the formation of the inner cell mass, whereas a low level of let-7 at the 4-cell to 8-cell stage enhanced blastocyst formation. Tead4 mediated the action of let-7 on the inner cell mass cell-fate determination.
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Affiliation(s)
- Weimin Liu
- Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.,Shenzhen Key Laboratory of Fertility Regulation, Center of Reproductive Medicine and Prenatal Diagnosis, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China
| | - Jing Chen
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Chen Yang
- Shenzhen Key Laboratory of Fertility Regulation, Center of Reproductive Medicine and Prenatal Diagnosis, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China
| | - Kai-Fai Lee
- Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Yin-Lau Lee
- Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Philip Chi-Ngong Chiu
- Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Yihui Zhang
- Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.,Shenzhen Key Laboratory of Fertility Regulation, Center of Reproductive Medicine and Prenatal Diagnosis, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China
| | - Yong-Gong Duan
- Shenzhen Key Laboratory of Fertility Regulation, Center of Reproductive Medicine and Prenatal Diagnosis, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China
| | - Kui Liu
- Shenzhen Key Laboratory of Fertility Regulation, Center of Reproductive Medicine and Prenatal Diagnosis, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China.,Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - William Shu-Biu Yeung
- Shenzhen Key Laboratory of Fertility Regulation, Center of Reproductive Medicine and Prenatal Diagnosis, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China.,Department of Obstetrics and Gynaecology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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8
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New insights into the epitranscriptomic control of pluripotent stem cell fate. Exp Mol Med 2022; 54:1643-1651. [PMID: 36266446 PMCID: PMC9636187 DOI: 10.1038/s12276-022-00824-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/26/2022] [Accepted: 06/01/2022] [Indexed: 12/29/2022] Open
Abstract
Each cell in the human body has a distinguishable fate. Pluripotent stem cells are challenged with a myriad of lineage differentiation options. Defects are more likely to be fatal to stem cells than to somatic cells due to the broad impact of the former on early development. Hence, a detailed understanding of the mechanisms that determine the fate of stem cells is needed. The mechanisms by which human pluripotent stem cells, although not fully equipped with complex chromatin structures or epigenetic regulatory mechanisms, accurately control gene expression and are important to the stem cell field. In this review, we examine the events driving pluripotent stem cell fate and the underlying changes in gene expression during early development. In addition, we highlight the role played by the epitranscriptome in the regulation of gene expression that is necessary for each fate-related event.
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9
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Guo Y, Lee RE. Long-term imaging of individual mRNA molecules in living cells. CELL REPORTS METHODS 2022; 2:100226. [PMID: 35784652 PMCID: PMC9243547 DOI: 10.1016/j.crmeth.2022.100226] [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] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 03/10/2022] [Accepted: 05/04/2022] [Indexed: 12/04/2022]
Abstract
Single-cell imaging of individual mRNAs has revealed core mechanisms of the central dogma. However, most approaches require cell fixation or have limited sensitivity for live-cell applications. Here, we describe SunRISER (SunTag-based reporter for imaging signal-enriched mRNA), a computationally and experimentally optimized approach for unambiguous detection of single mRNA molecules in living cells. When viewed by epifluorescence microscopy, SunRISER-labeled mRNAs show strong signal to background and resistance to photobleaching, which together enable long-term mRNA imaging studies. SunRISER variants, using 8× and 10× stem-loop arrays, demonstrate effective mRNA detection while significantly reducing alterations to target mRNA sequences. We characterize SunRISER to observe mRNA inheritance during mitosis and find that stressors enhance diversity among post-mitotic sister cells. Taken together, SunRISER enables a glimpse into living cells to observe aspects of the central dogma and the role of mRNAs in rare and dynamical trafficking events.
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Affiliation(s)
- Yue Guo
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Robin E.C. Lee
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Center for Systems Immunology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
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10
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Bioimaging approaches for quantification of individual cell behavior during cell fate decisions. Biochem Soc Trans 2022; 50:513-527. [PMID: 35166330 DOI: 10.1042/bst20210534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 01/10/2022] [Accepted: 01/24/2022] [Indexed: 11/17/2022]
Abstract
Tracking individual cells has allowed a new understanding of cellular behavior in human health and disease by adding a dynamic component to the already complex heterogeneity of single cells. Technically, despite countless advances, numerous experimental variables can affect data collection and interpretation and need to be considered. In this review, we discuss the main technical aspects and biological findings in the analysis of the behavior of individual cells. We discuss the most relevant contributions provided by these approaches in clinically relevant human conditions like embryo development, stem cells biology, inflammation, cancer and microbiology, along with the cellular mechanisms and molecular pathways underlying these conditions. We also discuss the key technical aspects to be considered when planning and performing experiments involving the analysis of individual cells over long periods. Despite the challenges in automatic detection, features extraction and long-term tracking that need to be tackled, the potential impact of single-cell bioimaging is enormous in understanding the pathogenesis and development of new therapies in human pathophysiology.
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11
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Pomp O, Lim HYG, Skory RM, Moverley AA, Tetlak P, Bissiere S, Plachta N. A monoastral mitotic spindle determines lineage fate and position in the mouse embryo. Nat Cell Biol 2022; 24:155-167. [PMID: 35102267 DOI: 10.1038/s41556-021-00826-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 11/30/2021] [Indexed: 12/11/2022]
Abstract
During mammalian development, the first asymmetric cell divisions segregate cells into inner and outer positions of the embryo to establish the pluripotent and trophectoderm lineages. Typically, polarity components differentially regulate the mitotic spindle via astral microtubule arrays to trigger asymmetric division patterns. However, early mouse embryos lack centrosomes, the microtubule-organizing centres (MTOCs) that usually generate microtubule asters. Thus, it remains unknown whether spindle organization regulates lineage segregation. Here we find that heterogeneities in cell polarity in the early 8-cell-stage mouse embryo trigger the assembly of a highly asymmetric spindle organization. This spindle arises in an unusual modular manner, forming a single microtubule aster from an apically localized, non-centrosomal MTOC, before joining it to the rest of the spindle apparatus. When fully assembled, this 'monoastral' spindle triggers spatially asymmetric division patterns to segregate cells into inner and outer positions. Moreover, the asymmetric inheritance of spindle components causes differential cell polarization to determine pluripotent versus trophectoderm lineage fate.
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Affiliation(s)
- Oz Pomp
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Hui Yi Grace Lim
- Institute of Molecular and Cell Biology, ASTAR, Singapore, Singapore
| | - Robin M Skory
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Adam A Moverley
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Piotr Tetlak
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Stephanie Bissiere
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nicolas Plachta
- Department of Cell and Developmental Biology, Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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12
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Wadkin LE, Orozco-Fuentes S, Neganova I, Lako M, Parker NG, Shukurov A. A mathematical modelling framework for the regulation of intra-cellular OCT4 in human pluripotent stem cells. PLoS One 2021; 16:e0254991. [PMID: 34347824 PMCID: PMC8336844 DOI: 10.1371/journal.pone.0254991] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 07/07/2021] [Indexed: 12/04/2022] Open
Abstract
Human pluripotent stem cells (hPSCs) have the potential to differentiate into all cell types, a property known as pluripotency. A deeper understanding of how pluripotency is regulated is required to assist in controlling pluripotency and differentiation trajectories experimentally. Mathematical modelling provides a non-invasive tool through which to explore, characterise and replicate the regulation of pluripotency and the consequences on cell fate. Here we use experimental data of the expression of the pluripotency transcription factor OCT4 in a growing hPSC colony to develop and evaluate mathematical models for temporal pluripotency regulation. We consider fractional Brownian motion and the stochastic logistic equation and explore the effects of both additive and multiplicative noise. We illustrate the use of time-dependent carrying capacities and the introduction of Allee effects to the stochastic logistic equation to describe cell differentiation. We conclude both methods adequately capture the decline in OCT4 upon differentiation, but the Allee effect model has the advantage of allowing differentiation to occur stochastically in a sub-set of cells. This mathematical framework for describing intra-cellular OCT4 regulation can be extended to other transcription factors and developed into predictive models.
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Affiliation(s)
- L E Wadkin
- School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - S Orozco-Fuentes
- Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - I Neganova
- Institute of Cytology, RAS St Petersburg, Novosibirsk, Russia
| | - M Lako
- Bioscience Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - N G Parker
- School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - A Shukurov
- School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, United Kingdom
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13
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Abstract
The cytoskeleton - comprising actin filaments, microtubules and intermediate filaments - serves instructive roles in regulating cell function and behaviour during development. However, a key challenge in cell and developmental biology is to dissect how these different structures function and interact in vivo to build complex tissues, with the ultimate aim to understand these processes in a mammalian organism. The preimplantation mouse embryo has emerged as a primary model system for tackling this challenge. Not only does the mouse embryo share many morphological similarities with the human embryo during its initial stages of life, it also permits the combination of genetic manipulations with live-imaging approaches to study cytoskeletal dynamics directly within an intact embryonic system. These advantages have led to the discovery of novel cytoskeletal structures and mechanisms controlling lineage specification, cell-cell communication and the establishment of the first forms of tissue architecture during development. Here we highlight the diverse organization and functions of each of the three cytoskeletal filaments during the key events that shape the early mammalian embryo, and discuss how they work together to perform key developmental tasks, including cell fate specification and morphogenesis of the blastocyst. Collectively, these findings are unveiling a new picture of how cells in the early embryo dynamically remodel their cytoskeleton with unique spatial and temporal precision to drive developmental processes in the rapidly changing in vivo environment.
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14
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Zhu M, Zernicka-Goetz M. Principles of Self-Organization of the Mammalian Embryo. Cell 2021; 183:1467-1478. [PMID: 33306953 DOI: 10.1016/j.cell.2020.11.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/23/2020] [Accepted: 11/02/2020] [Indexed: 02/07/2023]
Abstract
Early embryogenesis is a conserved and self-organized process. In the mammalian embryo, the potential for self-organization is manifested in its extraordinary developmental plasticity, allowing a correctly patterned embryo to arise despite experimental perturbation. The underlying mechanisms enabling such regulative development have long been a topic of study. In this Review, we summarize our current understanding of the self-organizing principles behind the regulative nature of the early mammalian embryo. We argue that geometrical constraints, feedback between mechanical and biochemical factors, and cellular heterogeneity are all required to ensure the developmental plasticity of mammalian embryo development.
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Affiliation(s)
- Meng Zhu
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK; Present address: Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
| | - Magdalena Zernicka-Goetz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, USA.
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15
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Corradi E, Baudet ML. In the Right Place at the Right Time: miRNAs as Key Regulators in Developing Axons. Int J Mol Sci 2020; 21:ijms21228726. [PMID: 33218218 PMCID: PMC7699167 DOI: 10.3390/ijms21228726] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/12/2020] [Accepted: 11/16/2020] [Indexed: 01/02/2023] Open
Abstract
During neuronal circuit formation, axons progressively develop into a presynaptic compartment aided by extracellular signals. Axons display a remarkably high degree of autonomy supported in part by a local translation machinery that permits the subcellular production of proteins required for their development. Here, we review the latest findings showing that microRNAs (miRNAs) are critical regulators of this machinery, orchestrating the spatiotemporal regulation of local translation in response to cues. We first survey the current efforts toward unraveling the axonal miRNA repertoire through miRNA profiling, and we reveal the presence of a putative axonal miRNA signature. We also provide an overview of the molecular underpinnings of miRNA action. Our review of the available experimental evidence delineates two broad paradigms: cue-induced relief of miRNA-mediated inhibition, leading to bursts of protein translation, and cue-induced miRNA activation, which results in reduced protein production. Overall, this review highlights how a decade of intense investigation has led to a new appreciation of miRNAs as key elements of the local translation regulatory network controlling axon development.
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16
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Lim HYG, Alvarez YD, Gasnier M, Wang Y, Tetlak P, Bissiere S, Wang H, Biro M, Plachta N. Keratins are asymmetrically inherited fate determinants in the mammalian embryo. Nature 2020; 585:404-409. [PMID: 32848249 DOI: 10.1038/s41586-020-2647-4] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 07/30/2020] [Indexed: 11/08/2022]
Abstract
To implant in the uterus, the mammalian embryo first specifies two cell lineages: the pluripotent inner cell mass that forms the fetus, and the outer trophectoderm layer that forms the placenta1. In many organisms, asymmetrically inherited fate determinants drive lineage specification2, but this is not thought to be the case during early mammalian development. Here we show that intermediate filaments assembled by keratins function as asymmetrically inherited fate determinants in the mammalian embryo. Unlike F-actin or microtubules, keratins are the first major components of the cytoskeleton that display prominent cell-to-cell variability, triggered by heterogeneities in the BAF chromatin-remodelling complex. Live-embryo imaging shows that keratins become asymmetrically inherited by outer daughter cells during cell division, where they stabilize the cortex to promote apical polarization and YAP-dependent expression of CDX2, thereby specifying the first trophectoderm cells of the embryo. Together, our data reveal a mechanism by which cell-to-cell heterogeneities that appear before the segregation of the trophectoderm and the inner cell mass influence lineage fate, via differential keratin regulation, and identify an early function for intermediate filaments in development.
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Affiliation(s)
- Hui Yi Grace Lim
- Institute of Molecular and Cell Biology, ASTAR, Singapore, Singapore
| | - Yanina D Alvarez
- Institute of Molecular and Cell Biology, ASTAR, Singapore, Singapore
| | - Maxime Gasnier
- Institute of Molecular and Cell Biology, ASTAR, Singapore, Singapore
| | - Yiming Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Science, Beijing, China
| | - Piotr Tetlak
- Institute of Molecular and Cell Biology, ASTAR, Singapore, Singapore
| | | | - Hongmei Wang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Science, Beijing, China
| | - Maté Biro
- EMBL Australia, Single Molecule Science Node, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Nicolas Plachta
- Institute of Molecular and Cell Biology, ASTAR, Singapore, Singapore.
- Department of Cell and Developmental Biology and Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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17
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Trylinski M, Baum B. Developing cells remember where they came from, thanks to keratin filaments. Nature 2020; 585:352-353. [PMID: 32848238 DOI: 10.1038/d41586-020-02443-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Abstract
Asymmetric cell division (ACD) is an evolutionarily conserved mechanism used by prokaryotes and eukaryotes alike to control cell fate and generate cell diversity. A detailed mechanistic understanding of ACD is therefore necessary to understand cell fate decisions in health and disease. ACD can be manifested in the biased segregation of macromolecules, the differential partitioning of cell organelles, or differences in sibling cell size or shape. These events are usually preceded by and influenced by symmetry breaking events and cell polarization. In this Review, we focus predominantly on cell intrinsic mechanisms and their contribution to cell polarization, ACD and binary cell fate decisions. We discuss examples of polarized systems and detail how polarization is established and, whenever possible, how it contributes to ACD. Established and emerging model organisms will be considered alike, illuminating both well-documented and underexplored forms of polarization and ACD.
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Affiliation(s)
- Bharath Sunchu
- Department of Biology, University of Washington, Life Science Building, Seattle, WA 98195, USA
| | - Clemens Cabernard
- Department of Biology, University of Washington, Life Science Building, Seattle, WA 98195, USA
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19
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Casser E, Wdowik S, Israel S, Witten A, Schlatt S, Nordhoff V, Boiani M. Differences in blastomere totipotency in 2-cell mouse embryos are a maternal trait mediated by asymmetric mRNA distribution. Mol Hum Reprod 2020; 25:729-744. [PMID: 31504820 PMCID: PMC6884417 DOI: 10.1093/molehr/gaz051] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 07/05/2019] [Accepted: 08/14/2019] [Indexed: 12/13/2022] Open
Abstract
It is widely held that the first two blastomeres of mammalian embryos are equally totipotent and that this totipotency belongs to the group of regulative properties. However, this interpretation neglects an important aspect: evidence only came from successful monozygotic twins which can speak only for those pairs of half-embryos that are able to regulate in the first place. Are the frequently occurring incomplete pairs simply an artefact, or do they represent a real difference, be it in the imperfect blastomere's ability to regulate growth or in the distribution of any compound X that constrains regulation? Using the model system of mouse embryos bisected at the 2-cell stage after fertilization, we present evidence that the interblastomere differences evade regulation by external factors and are already latent in oocytes. Specifically, an interblastomere imbalance of epiblast production persists under the most diverse culture conditions and applies to the same extent in parthenogenetic counterparts. As a result, cases in which twin blastocysts continued to develop in only one member account for 65 and 57% of zygotic and parthenogenetic pairs, respectively. The interblastomere imbalance is related to the subcellular distribution of gene products, as documented for the epiblast-related gene Cops3, using mRNA FISH in super-resolution mode confocal microscopy. Blastomere patterns of Cops3 mRNA distribution are α-amanitin-resistant. Thus, the imbalance originates not from de novo transcription, but from influences which are effective before fertilisation. These data expose previously unrecognized limits of regulative capacities of 2-cell stage blastomeres and point to aspects of cytoplasmic organization of the mouse oocyte that segregate unequally to blastomeres during cleavage.
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Affiliation(s)
- E Casser
- Max Planck Institute for Molecular Biomedicine, Muenster, Germany
| | - S Wdowik
- Max Planck Institute for Molecular Biomedicine, Muenster, Germany
| | - S Israel
- Max Planck Institute for Molecular Biomedicine, Muenster, Germany
| | - A Witten
- Core Genomic Facility, University Hospital Muenster, Muenster, Germany
| | - S Schlatt
- Centre for Reproductive Medicine and Andrology, University Hospital Muenster, Muenster, Germany
| | - V Nordhoff
- Centre for Reproductive Medicine and Andrology, University Hospital Muenster, Muenster, Germany
| | - M Boiani
- Max Planck Institute for Molecular Biomedicine, Muenster, Germany
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20
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Zhu M, Zernicka-Goetz M. Building an apical domain in the early mouse embryo: Lessons, challenges and perspectives. Curr Opin Cell Biol 2019; 62:144-149. [PMID: 31869760 DOI: 10.1016/j.ceb.2019.11.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 11/21/2019] [Indexed: 01/09/2023]
Abstract
Cell polarization is critical for lineage segregation and morphogenesis during mammalian embryogenesis. However, the processes and mechanisms that establish cell polarity in the mammalian embryo are not well understood. Recent studies suggest that unique regulatory mechanisms are deployed by the mouse embryo to establish cell polarization. In this review, we discuss the current understanding of cell polarity establishment, focusing on the formation of the apical domain in the mouse embryo. We will also discuss outstanding questions and possible directions for future study.
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Affiliation(s)
- Meng Zhu
- Mammalian Embryo and Stem Cell Group, University of Cambridge, Department of Physiology, Development and Neuroscience, Downing Street, Cambridge, CB2 3DY, UK
| | - Magdalena Zernicka-Goetz
- Mammalian Embryo and Stem Cell Group, University of Cambridge, Department of Physiology, Development and Neuroscience, Downing Street, Cambridge, CB2 3DY, UK.
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21
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Pfeffer PL. Building Principles for Constructing a Mammalian Blastocyst Embryo. BIOLOGY 2018; 7:biology7030041. [PMID: 30041494 PMCID: PMC6164496 DOI: 10.3390/biology7030041] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 07/19/2018] [Accepted: 07/20/2018] [Indexed: 12/16/2022]
Abstract
The self-organisation of a fertilised egg to form a blastocyst structure, which consists of three distinct cell lineages (trophoblast, epiblast and hypoblast) arranged around an off-centre cavity, is unique to mammals. While the starting point (the zygote) and endpoint (the blastocyst) are similar in all mammals, the intervening events have diverged. This review examines and compares the descriptive and functional data surrounding embryonic gene activation, symmetry-breaking, first and second lineage establishment, and fate commitment in a wide range of mammalian orders. The exquisite detail known from mouse embryogenesis, embryonic stem cell studies and the wealth of recent single cell transcriptomic experiments are used to highlight the building principles underlying early mammalian embryonic development.
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Affiliation(s)
- Peter L Pfeffer
- School of Biological Sciences, Victoria University of Wellington, Wellington 6012, New Zealand.
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22
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Causes and evolutionary consequences of primordial germ-cell specification mode in metazoans. Proc Natl Acad Sci U S A 2018; 114:5784-5791. [PMID: 28584112 DOI: 10.1073/pnas.1610600114] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In animals, primordial germ cells (PGCs) give rise to the germ lines, the cell lineages that produce sperm and eggs. PGCs form in embryogenesis, typically by one of two modes: a likely ancestral mode wherein germ cells are induced during embryogenesis by cell-cell signaling (induction) or a derived mechanism whereby germ cells are specified by using germ plasm-that is, maternally specified germ-line determinants (inheritance). The causes of the shift to germ plasm for PGC specification in some animal clades remain largely unknown, but its repeated convergent evolution raises the question of whether it may result from or confer an innate selective advantage. It has been hypothesized that the acquisition of germ plasm confers enhanced evolvability, resulting from the release of selective constraint on somatic gene networks in embryogenesis, thus leading to acceleration of an organism's protein-sequence evolution, particularly for genes expressed at early developmental stages, and resulting in high speciation rates in germ plasm-containing lineages (denoted herein as the "PGC-specification hypothesis"). Although that hypothesis, if supported, could have major implications for animal evolution, our recent large-scale coding-sequence analyses from vertebrates and invertebrates provided important examples of genera that do not support the hypothesis of liberated constraint under germ plasm. Here, we consider reasons why germ plasm might be neither a direct target of selection nor causally linked to accelerated animal evolution. We explore alternate scenarios that could explain the repeated evolution of germ plasm and propose potential consequences of the inheritance and induction modes to animal evolutionary biology.
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23
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Chen Q, Shi J, Tao Y, Zernicka-Goetz M. Tracing the origin of heterogeneity and symmetry breaking in the early mammalian embryo. Nat Commun 2018; 9:1819. [PMID: 29739935 PMCID: PMC5940674 DOI: 10.1038/s41467-018-04155-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 04/06/2018] [Indexed: 01/02/2023] Open
Abstract
A fundamental question in developmental and stem cell biology concerns the origin and nature of signals that initiate asymmetry leading to pattern formation and self-organization. Instead of having prominent pre-patterning determinants as present in model organisms (worms, sea urchin, frog), we propose that the mammalian embryo takes advantage of more subtle cues such as compartmentalized intracellular reactions that generate micro-scale inhomogeneity, which is gradually amplified over several cellular generations to drive pattern formation while keeping developmental plasticity. It is therefore possible that by making use of compartmentalized information followed by its amplification, mammalian embryos would follow general principle of development found in other organisms in which the spatial cue is more robustly presented.
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Affiliation(s)
- Qi Chen
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Junchao Shi
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, 89557, USA
| | - Yi Tao
- Center for Computational and Evolutionary Biology, Institute of Zoology, Chinese Academy of Sciences, 100101, Beijing, China
| | - Magdalena Zernicka-Goetz
- Mammalian Development and Stem Cell Group, Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK.
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24
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The Role of Maternal-Effect Genes in Mammalian Development: Are Mammalian Embryos Really an Exception? Stem Cell Rev Rep 2017; 12:276-84. [PMID: 26892267 DOI: 10.1007/s12015-016-9648-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The essential contribution of multiple maternal factors to early mammalian development is rapidly altering the view that mammals have a unique pattern of development compared to other species. Currently, over 60 maternal-effect mutations have been described in mammalian systems, including critical determinants of pluripotency. This data, combined with the evidence for lineage bias and differential gene expression in early blastomeres, strongly suggests that mammalian development is to some extent mosaic from the four-cell stage onward.
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25
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Holmes WR, Reyes de Mochel NS, Wang Q, Du H, Peng T, Chiang M, Cinquin O, Cho K, Nie Q. Gene Expression Noise Enhances Robust Organization of the Early Mammalian Blastocyst. PLoS Comput Biol 2017; 13:e1005320. [PMID: 28114387 PMCID: PMC5293272 DOI: 10.1371/journal.pcbi.1005320] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 02/06/2017] [Accepted: 12/19/2016] [Indexed: 12/18/2022] Open
Abstract
A critical event in mammalian embryo development is construction of an inner cell mass surrounded by a trophoectoderm (a shell of cells that later form extraembryonic structures). We utilize multi-scale, stochastic modeling to investigate the design principles responsible for robust establishment of these structures. This investigation makes three predictions, each supported by our quantitative imaging. First, stochasticity in the expression of critical genes promotes cell plasticity and has a critical role in accurately organizing the developing mouse blastocyst. Second, asymmetry in the levels of noise variation (expression fluctuation) of Cdx2 and Oct4 provides a means to gain the benefits of noise-mediated plasticity while ameliorating the potentially detrimental effects of stochasticity. Finally, by controlling the timing and pace of cell fate specification, the embryo temporally modulates plasticity and creates a time window during which each cell can continually read its environment and adjusts its fate. These results suggest noise has a crucial role in maintaining cellular plasticity and organizing the blastocyst. A critical event in mammalian embryo development is construction of a mass of embryonic stem cells surrounded by a distinct shell that later forms the placenta along with other structures. Despite sustained investigation, multiple hypotheses for what is responsible for this organization persist and it remains unclear what is responsible for the robust organization (remarkable ability for embryos to pattern correctly) of these structures. Here, we utilize multi-scale, stochastic modeling along with fluorescence imaging to investigate the factors that contribute to the incredible robustness of this organizational process. Results point to two factors that contribute to this robustness: 1) the timing and pace of cell fate specification and 2) stochastic gene regulatory effects. The former creates a window of time during which each cell can continually read their environment and adjust their gene expressions (and consequently fate) in response to dynamic rearrangements of cells arising from cell divisions and motions. The latter improves cell plasticity, providing the capability for cells to adjust to changes in their local environment. Fluorescence imaging results demonstrate that the magnitude and structure of gene expression variations match those predicted to promote organizational robustness.
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Affiliation(s)
- William R. Holmes
- Department of Physics and Astronomy, Vanderbilt University, Nashville TN, United States of America
| | - Nabora Soledad Reyes de Mochel
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States of America
| | - Qixuan Wang
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Mathematics, University of California, Irvine, Irvine, CA, United States of America
| | - Huijing Du
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Mathematics, University of California, Irvine, Irvine, CA, United States of America
| | - Tao Peng
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Mathematics, University of California, Irvine, Irvine, CA, United States of America
| | - Michael Chiang
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States of America
| | - Olivier Cinquin
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States of America
| | - Ken Cho
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States of America
- * E-mail: (QN); (KC)
| | - Qing Nie
- Center for Complex Biological Systems, University of California, Irvine, Irvine, CA, United States of America
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States of America
- Department of Mathematics, University of California, Irvine, Irvine, CA, United States of America
- * E-mail: (QN); (KC)
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26
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White MD, Zenker J, Bissiere S, Plachta N. How cells change shape and position in the early mammalian embryo. Curr Opin Cell Biol 2016; 44:7-13. [PMID: 28033492 DOI: 10.1016/j.ceb.2016.11.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 11/23/2016] [Accepted: 11/27/2016] [Indexed: 10/20/2022]
Abstract
During preimplantation development, cells of the mammalian embryo must resolve their shape and position to ensure the future viability of the fetus. These initial changes are established as the embryo expands from one to thirty-two cells, and a group of originally spherical cells is transformed into a more polarized structure with distinct cell geometries and lineages. Recent advances in the application of non-invasive imaging technologies have enabled the discovery of mechanisms regulating patterning of the early mammalian embryo. Here, we review recent findings revealing cell protrusions that trigger early changes in cell shape and embryo compaction, and how anisotropies in mechanical forces drive the first spatial segregation of cells in the embryo to form the pluripotent inner mass.
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Affiliation(s)
- Melanie D White
- Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore
| | - Jennifer Zenker
- Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore
| | - Stephanie Bissiere
- Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore
| | - Nicolas Plachta
- Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore.
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27
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Leung CY, Zhu M, Zernicka-Goetz M. Polarity in Cell-Fate Acquisition in the Early Mouse Embryo. Curr Top Dev Biol 2016; 120:203-34. [PMID: 27475853 DOI: 10.1016/bs.ctdb.2016.04.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Establishing polarity is a fundamental part of embryogenesis and can be traced back to the earliest developmental stages. It can be achieved in one of two ways: through the preexisting polarization of germ cells before fertilization or via symmetry breaking after fertilization. In mammals, it seems to be the latter, and we will discuss the various cytological and molecular events that lead up to this event, its mechanisms and the consequences. In mammals, the first polarization event occurs in the preimplantation period, when the embryo is but a cluster of cells, free-floating in the oviduct. This provides a unique, autonomous system to study the de novo polarization that is essential to life. In this review, we will cover modern and past studies on the polarization of the early embryo, using the mouse as a model system, as well as hypothesizing the potential implications and functions of the biological events involved.
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Affiliation(s)
- C Y Leung
- University of Cambridge, Cambridge, United Kingdom
| | - M Zhu
- University of Cambridge, Cambridge, United Kingdom
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28
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Lokken AA, Ralston A. The Genetic Regulation of Cell Fate During Preimplantation Mouse Development. Curr Top Dev Biol 2016; 120:173-202. [PMID: 27475852 DOI: 10.1016/bs.ctdb.2016.04.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The adult body is estimated to contain several hundred distinct cell types, each with a specialized physiological function. Failure to maintain cell fate can lead to devastating diseases and cancer, but understanding how cell fates are assigned and maintained during animal development provides new opportunities for human health intervention. The mouse is a premier model for evaluating the genetic regulation of cell fate during development because of the wide variety of tools for measuring and manipulating gene expression levels, the ability to access embryos at desired developmental stages, and the similarities between mouse and human development, particularly during the early stages of development. During the first 3 days of mouse development, the preimplantation embryo sets aside cells that will contribute to the extraembryonic tissues. The extraembryonic tissues are essential for establishing pregnancy and ensuring normal fetal development in both mice and humans. Genetic analyses of mouse preimplantation development have permitted identification of genes that are essential for specification of the extraembryonic lineages. In this chapter, we review the tools and concepts of mouse preimplantation development. We describe genes that are essential for cell fate specification during preimplantation stages, and we describe diverse models proposed to account for the mechanisms of cell fate specification during early development.
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Affiliation(s)
- A A Lokken
- Michigan State University, East Lansing, MI, United States
| | - A Ralston
- Michigan State University, East Lansing, MI, United States.
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29
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Varela N, Aranguiz A, Lizama C, Sepulveda H, Antonelli M, Thaler R, Moreno RD, Montecino M, Stein GS, van Wijnen AJ, Galindo M. Mitotic Inheritance of mRNA Facilitates Translational Activation of the Osteogenic-Lineage Commitment Factor Runx2 in Progeny of Osteoblastic Cells. J Cell Physiol 2016; 231:1001-14. [PMID: 26381402 PMCID: PMC5812339 DOI: 10.1002/jcp.25188] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 09/03/2015] [Indexed: 12/24/2022]
Abstract
Epigenetic mechanisms mediate the acquisition of specialized cellular phenotypes during tissue development, maintenance and repair. When phenotype-committed cells transit through mitosis, chromosomal condensation counteracts epigenetic activation of gene expression. Subsequent post-mitotic re-activation of transcription depends on epigenetic DNA and histone modifications, as well as other architecturally bound proteins that "bookmark" the genome. Osteogenic lineage commitment, differentiation and progenitor proliferation require the bone-related runt-related transcription factor Runx2. Here, we characterized a non-genomic mRNA mediated mechanism by which osteoblast precursors retain their phenotype during self-renewal. We show that osteoblasts produce maximal levels of Runx2 mRNA, but not protein, prior to mitotic cell division. Runx2 mRNA partitions symmetrically between daughter cells in a non-chromosomal tubulin-containing compartment. Subsequently, transcription-independent de novo synthesis of Runx2 protein in early G1 phase results in increased functional interactions of Runx2 with a representative osteoblast-specific target gene (osteocalcin/BGLAP2) in chromatin. Somatic transmission of Runx2 mRNAs in osteoblasts and osteosarcoma cells represents a versatile mechanism for translational rather than transcriptional induction of this principal gene regulator to maintain osteoblast phenotype identity after mitosis.
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Affiliation(s)
- Nelson Varela
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
- Department of Medical Technology, Faculty of Medicine, University of Chile, Santiago, Chile
- Millennium Institute on Immunology and Immunotherapy, University of Chile, Santiago, Chile
| | - Alejandra Aranguiz
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
- Millennium Institute on Immunology and Immunotherapy, University of Chile, Santiago, Chile
| | - Carlos Lizama
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Hugo Sepulveda
- Center for Biomedical Research and FONDAP Center for Genome Regulation, Faculty of Biological Sciences and Faculty of Medicine, Universidad Andres Bello, Santiago, Chile
| | - Marcelo Antonelli
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
| | - Roman Thaler
- Departments of Orthopedic Surgery & Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street S.W., MSB 3-69, Rochester, MN 55905
| | - Ricardo D. Moreno
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Martin Montecino
- Center for Biomedical Research and FONDAP Center for Genome Regulation, Faculty of Biological Sciences and Faculty of Medicine, Universidad Andres Bello, Santiago, Chile
| | - Gary S. Stein
- Department of Biochemistry, HSRF 326, Vermont Cancer Center for Basic and Translational Research, University of Vermont Medical School, Burlington, VT
| | - Andre J. van Wijnen
- Departments of Orthopedic Surgery & Biochemistry and Molecular Biology, Mayo Clinic, 200 First Street S.W., MSB 3-69, Rochester, MN 55905
| | - Mario Galindo
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, University of Chile, Santiago, Chile
- Millennium Institute on Immunology and Immunotherapy, University of Chile, Santiago, Chile
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30
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Chazaud C, Yamanaka Y. Lineage specification in the mouse preimplantation embryo. Development 2016; 143:1063-74. [DOI: 10.1242/dev.128314] [Citation(s) in RCA: 199] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
During mouse preimplantation embryo development, totipotent blastomeres generate the first three cell lineages of the embryo: trophectoderm, epiblast and primitive endoderm. In recent years, studies have shown that this process appears to be regulated by differences in cell-cell interactions, gene expression and the microenvironment of individual cells, rather than the active partitioning of maternal determinants. Precisely how these differences first emerge and how they dictate subsequent molecular and cellular behaviours are key questions in the field. As we review here, recent advances in live imaging, computational modelling and single-cell transcriptome analyses are providing new insights into these questions.
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Affiliation(s)
- Claire Chazaud
- Université Clermont Auvergne, Laboratoire GReD, Clermont-Ferrand F-63000, France
- Inserm, UMR1103, Clermont-Ferrand F-63001, France
- CNRS, UMR6293, Clermont-Ferrand F-63001, France
| | - Yojiro Yamanaka
- Goodman Cancer Research Centre, Department of Human Genetics, McGill University, 1160 Pine Avenue West, rm419, Montreal, Quebec, Canada H3A 1A3
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Graham SJ, Zernicka-Goetz M. The Acquisition of Cell Fate in Mouse Development. Curr Top Dev Biol 2016; 117:671-95. [DOI: 10.1016/bs.ctdb.2015.11.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Lee S, Pallerla SR, Kim S, Shaffer B, Simerly CR, Richard Chaillet J, Barak Y. Esrrb-Cre excises loxP-flanked alleles in early four-cell embryos. Genesis 2015; 54:53-61. [PMID: 26663459 DOI: 10.1002/dvg.22912] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 12/03/2015] [Accepted: 12/03/2015] [Indexed: 11/06/2022]
Abstract
Among transgenic mice with ubiquitous Cre recombinase activity, all strains to date excise loxP-flanked (floxed) alleles either at or before the zygote stage or at nondescript stages of development. This manuscript describes a new mouse strain, in which Cre recombinase, integrated into the Esrrb locus, efficiently excises floxed alleles in pre-implantation embryos at the onset of the four-cell stage. By enabling inactivation of genes only after the embryo has undergone two cleavages, this strain should facilitate in vivo studies of genes with essential gametic or zygotic functions. In addition, this study describes a new, highly pluripotent hybrid C57BL/6J x 129S1/SvImJ mouse embryonic stem cell line, HYB12, in which this knockin and additional targeted alleles have been generated.
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Affiliation(s)
- Sungeun Lee
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
| | - Srinivas R Pallerla
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
| | - Suyeon Kim
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
| | - Benjamin Shaffer
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
| | - Calvin R Simerly
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
| | - J Richard Chaillet
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
| | - Yaacov Barak
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA 15213
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Ajduk A, Zernicka-Goetz M. Polarity and cell division orientation in the cleavage embryo: from worm to human. Mol Hum Reprod 2015; 22:691-703. [PMID: 26660321 PMCID: PMC5062000 DOI: 10.1093/molehr/gav068] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 11/25/2015] [Indexed: 01/01/2023] Open
Abstract
Cleavage is a period after fertilization, when a 1-cell embryo starts developing into a multicellular organism. Due to a series of mitotic divisions, the large volume of a fertilized egg is divided into numerous smaller, nucleated cells—blastomeres. Embryos of different phyla divide according to different patterns, but molecular mechanism of these early divisions remains surprisingly conserved. In the present paper, we describe how polarity cues, cytoskeleton and cell-to-cell communication interact with each other to regulate orientation of the early embryonic division planes in model animals such as Caenorhabditis elegans, Drosophila and mouse. We focus particularly on the Par pathway and the actin-driven cytoplasmic flows that accompany it. We also describe a unique interplay between Par proteins and the Hippo pathway in cleavage mammalian embryos. Moreover, we discuss the potential meaning of polarity, cytoplasmic dynamics and cell-to-cell communication as quality biomarkers of human embryos.
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Affiliation(s)
- Anna Ajduk
- Department of Embryology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland
| | - Magdalena Zernicka-Goetz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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34
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The first two cell-fate decisions of preimplantation mouse embryo development are not functionally independent. Sci Rep 2015; 5:15034. [PMID: 26461180 PMCID: PMC4602213 DOI: 10.1038/srep15034] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 09/02/2015] [Indexed: 11/10/2022] Open
Abstract
During mouse preimplantation embryo development, three distinct cell lineages are formed, represented by the differentiating trophectoderm (TE), primitive endoderm (PrE) and the pluripotent epiblast (EPI). Classically, lineage derivation has been presented as a two-step process whereby outer TE cells are first segregated from inner-cell mass (ICM), followed by ICM refinement into either the PrE or EPI. As ICM founders can be produced following the fourth or fifth cleavage divisions, their potential to equally contribute to EPI and PrE is contested. Thus, modelling the early sequestration of ICM founders from TE-differentiation after the fourth cleavage division, we examined ICM lineage contribution of varying sized cell clones unable to initiate TE-differentiation. Such TE-inhibited ICM cells do not equally contribute to EPI and PrE and are significantly biased to form EPI. This bias is not caused by enhanced expression of the EPI marker Nanog, nor correlated with reduced apical polarity but associated with reduced expression of PrE-related gene transcripts (Dab2 and Lrp2) and down-regulation of plasma membrane associated Fgfr2. Our results favour a unifying model were the three cell lineages are guided in an integrated, yet flexible, fate decision centred on relative exposure of founder cells to TE-differentiative cues.
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35
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Hirate Y, Hirahara S, Inoue KI, Kiyonari H, Niwa H, Sasaki H. Par-aPKC-dependent and -independent mechanisms cooperatively control cell polarity, Hippo signaling, and cell positioning in 16-cell stage mouse embryos. Dev Growth Differ 2015; 57:544-56. [PMID: 26450797 DOI: 10.1111/dgd.12235] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 07/11/2015] [Accepted: 07/12/2015] [Indexed: 12/24/2022]
Abstract
In preimplantation mouse embryos, the Hippo signaling pathway plays a central role in regulating the fates of the trophectoderm (TE) and the inner cell mass (ICM). In early blastocysts with more than 32 cells, the Par-aPKC system controls polarization of the outer cells along the apicobasal axis, and cell polarity suppresses Hippo signaling. Inactivation of Hippo signaling promotes nuclear accumulation of a coactivator protein, Yap, leading to induction of TE-specific genes. However, whether similar mechanisms operate at earlier stages is not known. Here, we show that slightly different mechanisms operate in 16-cell stage embryos. Similar to 32-cell stage embryos, disruption of the Par-aPKC system activated Hippo signaling and suppressed nuclear Yap and Cdx2 expression in the outer cells. However, unlike 32-cell stage embryos, 16-cell stage embryos with a disrupted Par-aPKC system maintained apical localization of phosphorylated Ezrin/Radixin/Moesin (p-ERM), and the effects on Yap and Cdx2 were weak. Furthermore, normal 16-cell stage embryos often contained apolar cells in the outer position. In these cells, the Hippo pathway was strongly activated and Yap was excluded from the nuclei, thus resembling inner cells. Dissociated blastomeres of 8-cell stage embryos form polar-apolar couplets, which exhibit different levels of nuclear Yap, and the polar cell engulfed the apolar cell. These results suggest that cell polarization at the 16-cell stage is regulated by both Par-aPKC-dependent and -independent mechanisms. Asymmetric cell division is involved in cell polarity control, and cell polarity regulates cell positioning and most likely controls Hippo signaling.
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Affiliation(s)
- Yoshikazu Hirate
- Department of Cell Fate Control, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Shino Hirahara
- Laboratory for Embryonic Induction, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Ken-Ichi Inoue
- Animal Resource Development Unit, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Hiroshi Kiyonari
- Animal Resource Development Unit, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,Genetic Engineering Team, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Hiroshi Niwa
- Laboratory for Pluripotent Cell Studies, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,Department of Stem Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Hiroshi Sasaki
- Department of Cell Fate Control, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan.,Laboratory for Embryogenesis, Graduate School of Frontier BioSciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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Eckert JJ, Velazquez MA, Fleming TP. Cell signalling during blastocyst morphogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 843:1-21. [PMID: 25956293 DOI: 10.1007/978-1-4939-2480-6_1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Blastocyst morphogenesis is prepared for even before fertilisation. Information stored within parental gametes can influence both maternal and embryonic gene expression programmes after egg activation at fertilisation. A complex network of intrinsic, cell-cell mediated and extrinsic, embryo-environment signalling mechanisms operates throughout cleavage, compaction and cavitation. These signalling events not only ensure developmental progression, cell differentiation and lineage allocation to inner cell mass (embryo proper) and trophectoderm (future extraembryonic lineages) but also provide a degree of developmental plasticity ensuring survival in prevailing conditions by adaptive responses. Indeed, many cellular functions including differentiation, metabolism, gene expression and gene expression regulation are subject to plasticity with short- or long-term consequences even into adult life. The interplay between intrinsic and extrinsic signals impacting on blastocyst morphogenesis is becoming clearer. This has been best studied in the mouse which will be the focus of this chapter but translational significance to human and domestic animal embryology will be a focus in future years.
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Affiliation(s)
- Judith J Eckert
- Human Development and Health, Faculty of Medicine, University of Southampton, SO16 6YD, Southampton, UK
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37
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Jedrusik A. Making the first decision: lessons from the mouse. Reprod Med Biol 2015; 14:135-150. [PMID: 29259411 PMCID: PMC5715835 DOI: 10.1007/s12522-015-0206-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 03/31/2015] [Indexed: 01/06/2023] Open
Abstract
Pre-implantation development encompasses a period of 3-4 days over which the mammalian embryo has to make its first decision: to separate the pluripotent inner cell mass (ICM) from the extra-embryonic epithelial tissue, the trophectoderm (TE). The ICM gives rise to tissues mainly building the body of the future organism, while the TE contributes to the extra-embryonic tissues that support embryo development after implantation. This review provides an overview of the cellular and molecular mechanisms that control the critical aspects of this first decision, and highlights the role of critical events, namely zytotic genome activation, compaction, polarization, asymmetric cell divisions, formation of the blastocyst cavity and expression of key transcription factors.
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Affiliation(s)
- Agnieszka Jedrusik
- Wellcome Trust/CR UK Gurdon InstituteTennis Court RoadCB2 1QNCambridgeUK
- Department of Physiology, Development and NeuroscienceUniversity of CambridgeDowning StreetCB2 3DYCambridgeUK
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38
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Leung CY, Zernicka-Goetz M. Mapping the journey from totipotency to lineage specification in the mouse embryo. Curr Opin Genet Dev 2015; 34:71-6. [PMID: 26343010 DOI: 10.1016/j.gde.2015.08.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 08/03/2015] [Accepted: 08/11/2015] [Indexed: 10/23/2022]
Abstract
Understanding the past is to understand the present. Mammalian life, with all its complexity comes from a humble beginning of a single fertilized egg cell. Achieving this requires an enormous diversification of cellular function, the majority of which is generated through a series of cellular decisions during embryogenesis. The first decisions are made as the embryo prepares for implantation, a process that will require specialization of extra-embryonic lineages while preserving an embryonic one. In this mini-review, we will focus on the mouse as a mammalian model and discuss recent advances in the decision making process of the early embryo.
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Affiliation(s)
- Chuen Yan Leung
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom
| | - Magdalena Zernicka-Goetz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom.
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39
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Bedzhov I, Graham SJL, Leung CY, Zernicka-Goetz M. Developmental plasticity, cell fate specification and morphogenesis in the early mouse embryo. Philos Trans R Soc Lond B Biol Sci 2015; 369:rstb.2013.0538. [PMID: 25349447 PMCID: PMC4216461 DOI: 10.1098/rstb.2013.0538] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A critical point in mammalian development is when the early embryo implants into its mother's uterus. This event has historically been difficult to study due to the fact that it occurs within the maternal tissue and therefore is hidden from view. In this review, we discuss how the mouse embryo is prepared for implantation and the molecular mechanisms involved in directing and coordinating this crucial event. Prior to implantation, the cells of the embryo are specified as precursors of future embryonic and extra-embryonic lineages. These preimplantation cell fate decisions rely on a combination of factors including cell polarity, position and cell–cell signalling and are influenced by the heterogeneity between early embryo cells. At the point of implantation, signalling events between the embryo and mother, and between the embryonic and extraembryonic compartments of the embryo itself, orchestrate a total reorganization of the embryo, coupled with a burst of cell proliferation. New developments in embryo culture and imaging techniques have recently revealed the growth and morphogenesis of the embryo at the time of implantation, leading to a new model for the blastocyst to egg cylinder transition. In this model, pluripotent cells that will give rise to the fetus self-organize into a polarized three-dimensional rosette-like structure that initiates egg cylinder formation.
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Affiliation(s)
- Ivan Bedzhov
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Sarah J L Graham
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Chuen Yan Leung
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Magdalena Zernicka-Goetz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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40
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Frum T, Ralston A. Cell signaling and transcription factors regulating cell fate during formation of the mouse blastocyst. Trends Genet 2015; 31:402-10. [PMID: 25999217 DOI: 10.1016/j.tig.2015.04.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/05/2015] [Accepted: 04/07/2015] [Indexed: 11/17/2022]
Abstract
The first cell fate decisions during mammalian development establish tissues essential for healthy pregnancy. The mouse has served as a valuable model for discovering pathways regulating the first cell fate decisions because of the ease with which early embryos can be recovered and the availability of an arsenal of classical and emerging methods for manipulating gene expression. We summarize the major pathways that govern the first cell fate decisions in mouse development. This knowledge serves as a paradigm for exploring how emergent properties of a self-organizing system can dynamically regulate gene expression and cell fate plasticity. Moreover, it brings to light the processes that establish healthy pregnancy and ES cells. We also describe unsolved mysteries and new technologies that could help to overcome experimental challenges in the field.
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Affiliation(s)
- Tristan Frum
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Amy Ralston
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
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41
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Stegle O, Teichmann SA, Marioni JC. Computational and analytical challenges in single-cell transcriptomics. Nat Rev Genet 2015; 16:133-45. [PMID: 25628217 DOI: 10.1038/nrg3833] [Citation(s) in RCA: 733] [Impact Index Per Article: 81.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The development of high-throughput RNA sequencing (RNA-seq) at the single-cell level has already led to profound new discoveries in biology, ranging from the identification of novel cell types to the study of global patterns of stochastic gene expression. Alongside the technological breakthroughs that have facilitated the large-scale generation of single-cell transcriptomic data, it is important to consider the specific computational and analytical challenges that still have to be overcome. Although some tools for analysing RNA-seq data from bulk cell populations can be readily applied to single-cell RNA-seq data, many new computational strategies are required to fully exploit this data type and to enable a comprehensive yet detailed study of gene expression at the single-cell level.
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Affiliation(s)
- Oliver Stegle
- European Molecular Biology Laboratory European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, UK
| | - Sarah A Teichmann
- 1] European Molecular Biology Laboratory European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, UK. [2] Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - John C Marioni
- 1] European Molecular Biology Laboratory European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, UK. [2] Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
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42
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Graham SJL, Wicher KB, Jedrusik A, Guo G, Herath W, Robson P, Zernicka-Goetz M. BMP signalling regulates the pre-implantation development of extra-embryonic cell lineages in the mouse embryo. Nat Commun 2014; 5:5667. [PMID: 25514175 PMCID: PMC4338527 DOI: 10.1038/ncomms6667] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 10/24/2014] [Indexed: 01/22/2023] Open
Abstract
Pre-implantation development requires the specification and organization of embryonic and extra-embryonic lineages. The separation of these lineages takes place when asymmetric divisions generate inside and outside cells that differ in polarity, position and fate. Here we assess the global transcriptional identities of these precursor cells to gain insight into the molecular mechanisms regulating lineage segregation. Unexpectedly, this reveals that complementary components of the BMP signalling pathway are already differentially expressed after the first wave of asymmetric divisions. We investigate the role of BMP signalling by expressing dominant negative forms of Smad4 and Bmpr2, by down-regulating the pathway using RNAi against BMP ligands and by applying three different BMP inhibitors at distinct stages. This reveals that BMP signalling regulates the correct development of both extra-embryonic lineages, primitive endoderm and trophectoderm, but not the embryonic lineage, prior to implantation. Together these findings indicate multiple roles of BMP signalling in the early mouse embryo.
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Affiliation(s)
- Sarah J L Graham
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Krzysztof B Wicher
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Agnieszka Jedrusik
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Guoji Guo
- 1] Developmental Cellomics Laboratory, Genome Institute of Singapore, Singapore 138672, Singapore [2] Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Wishva Herath
- Developmental Cellomics Laboratory, Genome Institute of Singapore, Singapore 138672, Singapore
| | - Paul Robson
- 1] Developmental Cellomics Laboratory, Genome Institute of Singapore, Singapore 138672, Singapore [2] Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Magdalena Zernicka-Goetz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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43
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Jedrusik A, Cox A, Wicher KB, Glover DM, Zernicka-Goetz M. Maternal-zygotic knockout reveals a critical role of Cdx2 in the morula to blastocyst transition. Dev Biol 2014; 398:147-52. [PMID: 25512302 PMCID: PMC4319684 DOI: 10.1016/j.ydbio.2014.12.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 12/06/2014] [Indexed: 12/01/2022]
Abstract
The first lineage segregation in the mouse embryo generates the inner cell mass (ICM), which gives rise to the pluripotent epiblast and therefore the future embryo, and the trophectoderm (TE), which will build the placenta. The TE lineage depends on the transcription factor Cdx2. However, when Cdx2 first starts to act remains unclear. Embryos with zygotic deletion of Cdx2 develop normally until the late blastocyst stage leading to the conclusion that Cdx2 is important for the maintenance but not specification of the TE. In contrast, down-regulation of Cdx2 transcripts from the early embryo stage results in defects in TE specification before the blastocyst stage. Here, to unambiguously address at which developmental stage Cdx2 becomes first required, we genetically deleted Cdx2 from the oocyte stage using a Zp3-Cre/loxP strategy. Careful assessment of a large cohort of Cdx2 maternal-zygotic null embryos, all individually filmed, examined and genotyped, reveals an earlier lethal phenotype than observed in Cdx2 zygotic null embryos that develop until the late blastocyst stage. The developmental failure of Cdx2 maternal-zygotic null embryos is associated with cell death and failure of TE specification, starting at the morula stage. These results indicate that Cdx2 is important for the correct specification of TE from the morula stage onwards and that both maternal and zygotic pools of Cdx2 are required for correct pre-implantation embryogenesis.
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Affiliation(s)
- Agnieszka Jedrusik
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge CB2 3DY, UK
| | - Andy Cox
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge CB2 3DY, UK
| | - Krzysztof B Wicher
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge CB2 3DY, UK
| | - David M Glover
- Department of Genetics, University of Cambridge, Downing Site, Cambridge CB2 3EH, UK
| | - Magdalena Zernicka-Goetz
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge CB2 3DY, UK
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44
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Shimoni R, Pham K, Yassin M, Ludford-Menting MJ, Gu M, Russell SM. Normalized polarization ratios for the analysis of cell polarity. PLoS One 2014; 9:e99885. [PMID: 24963926 PMCID: PMC4070888 DOI: 10.1371/journal.pone.0099885] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 05/11/2014] [Indexed: 12/01/2022] Open
Abstract
The quantification and analysis of molecular localization in living cells is increasingly important for elucidating biological pathways, and new methods are rapidly emerging. The quantification of cell polarity has generated much interest recently, and ratiometric analysis of fluorescence microscopy images provides one means to quantify cell polarity. However, detection of fluorescence, and the ratiometric measurement, is likely to be sensitive to acquisition settings and image processing parameters. Using imaging of EGFP-expressing cells and computer simulations of variations in fluorescence ratios, we characterized the dependence of ratiometric measurements on processing parameters. This analysis showed that image settings alter polarization measurements; and that clustered localization is more susceptible to artifacts than homogeneous localization. To correct for such inconsistencies, we developed and validated a method for choosing the most appropriate analysis settings, and for incorporating internal controls to ensure fidelity of polarity measurements. This approach is applicable to testing polarity in all cells where the axis of polarity is known.
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Affiliation(s)
- Raz Shimoni
- Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria, Australia
- Immune Signalling Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
| | - Kim Pham
- Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria, Australia
- Immune Signalling Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
| | - Mohammed Yassin
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Immune Signalling Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
| | - Mandy J. Ludford-Menting
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Immune Signalling Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
| | - Min Gu
- Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria, Australia
| | - Sarah M. Russell
- Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Immune Signalling Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- * E-mail:
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45
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Ajduk A, Biswas Shivhare S, Zernicka-Goetz M. The basal position of nuclei is one pre-requisite for asymmetric cell divisions in the early mouse embryo. Dev Biol 2014; 392:133-40. [PMID: 24855000 PMCID: PMC4111899 DOI: 10.1016/j.ydbio.2014.05.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Revised: 05/06/2014] [Accepted: 05/07/2014] [Indexed: 10/30/2022]
Abstract
The early mouse embryo undertakes two types of cell division: symmetric that gives rise to the trophectoderm and then placenta or asymmetric that gives rise to inner cells that generate the embryo proper. Although cell division orientation is important, the mechanism regulating it has remained unclear. Here, we identify the relationship between the plane of cell division and the position of the nucleus and go towards identifying the mechanism behind it. We first find that as the 8-cell embryo progresses through the cell cycle, the nuclei of most - but not all - cells move from apical to more basal positions, in a microtubule- and kinesin-dependent manner. We then find that all asymmetric divisions happen when nuclei are located basally and, in contrast, all cells, in which nuclei remain apical, divide symmetrically. To understand the potential mechanism behind this, we determine the effects of modulating expression of Cdx2, a transcription factor key for trophectoderm formation and cell polarity. We find that increased expression of Cdx2 leads to an increase in a number of apical nuclei, whereas down-regulation of Cdx2 leads to more nuclei moving basally, which explains a previously identified relationship between Cdx2 and cell division orientation. Finally, we show that down-regulation of aPKC, involved in cell polarity, decreases the number of apical nuclei and doubles the number of asymmetric divisions. These results suggest a model in which the mutual interdependence of Cdx2 and cell polarity affects the cytoskeleton-dependent positioning of nuclei and, in consequence, the plane of cell division in the early mouse embryo.
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Affiliation(s)
- Anna Ajduk
- The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK; Department of Embryology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland
| | - Sourima Biswas Shivhare
- The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK; Institute of Reproductive Sciences, University of Oxford, Oxford OX4 2HW, UK
| | - Magdalena Zernicka-Goetz
- The Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK; Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK.
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Brison DR, Sturmey RG, Leese HJ. Metabolic heterogeneity during preimplantation development: the missing link? Hum Reprod Update 2014; 20:632-40. [DOI: 10.1093/humupd/dmu018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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Condic ML. Totipotency: what it is and what it is not. Stem Cells Dev 2014; 23:796-812. [PMID: 24368070 PMCID: PMC3991987 DOI: 10.1089/scd.2013.0364] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2013] [Accepted: 12/23/2013] [Indexed: 02/03/2023] Open
Abstract
There is surprising confusion surrounding the concept of biological totipotency, both within the scientific community and in society at large. Increasingly, ethical objections to scientific research have both practical and political implications. Ethical controversy surrounding an area of research can have a chilling effect on investors and industry, which in turn slows the development of novel medical therapies. In this context, clarifying precisely what is meant by "totipotency" and how it is experimentally determined will both avoid unnecessary controversy and potentially reduce inappropriate barriers to research. Here, the concept of totipotency is discussed, and the confusions surrounding this term in the scientific and nonscientific literature are considered. A new term, "plenipotent," is proposed to resolve this confusion. The requirement for specific, oocyte-derived cytoplasm as a component of totipotency is outlined. Finally, the implications of twinning for our understanding of totipotency are discussed.
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Affiliation(s)
- Maureen L Condic
- Department of Neurobiology, School of Medicine, University of Utah , Salt Lake City, Utah
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Leung CY, Zernicka-Goetz M. Angiomotin prevents pluripotent lineage differentiation in mouse embryos via Hippo pathway-dependent and -independent mechanisms. Nat Commun 2014; 4:2251. [PMID: 23903990 PMCID: PMC3741640 DOI: 10.1038/ncomms3251] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 07/03/2013] [Indexed: 01/04/2023] Open
Abstract
Cell identity is specified in the early mammalian embryo by the generation of precursors for two cell lineages: the pluripotent inner cell mass and differentiating trophectoderm. Here we identify Angiomotin as a key regulator of this process. We show that the loss of Angiomotin, together with Angiomotin-like 2, leads to differentiation of inner cell mass cells and compromised peri-implantation development. We show that Angiomotin regulates localization of Yap, and Yap-binding motifs are required for full activity of Angiomotin. Importantly, we also show that Angiomotin function can compensate for the absence of Lats1/2 kinases, indicating the ability of Angiomotin to bypass the classical Hippo pathway for Yap regulation. In polarized outside cells, Angiomotin localizes apically, pointing to the importance of cell polarity in regulating Yap to promote differentiation. We propose that both Hippo pathway-dependent and Hippo pathway-independent mechanisms regulate Yap localization to set apart pluripotent and differentiated lineages in the pre-implantation mouse embryo. Angiomotins retain the transcription co-activator YAP in the cytoplasm and thereby regulate the Hippo pathway in mammalian cultured cells. Here Leung and Zernicka-Goetz show that Angiomotin family members prevent the differentiation of inner cell mass cells in the mouse blastocyst, via both Hippo pathway-dependent and -independent mechanisms.
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Affiliation(s)
- Chuen Yan Leung
- The Wellcome Trust/Cancer Research UK Gurdon Institute, the Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
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Arias AM, Nichols J, Schröter C. A molecular basis for developmental plasticity in early mammalian embryos. Development 2013; 140:3499-510. [DOI: 10.1242/dev.091959] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Early mammalian embryos exhibit remarkable plasticity, as highlighted by the ability of separated early blastomeres to produce a whole organism. Recent work in the mouse implicates a network of transcription factors in governing the establishment of the primary embryonic lineages. A combination of genetics and embryology has uncovered the organisation and function of the components of this network, revealing a gradual resolution from ubiquitous to lineage-specific expression through a combination of defined regulatory relationships, spatially organised signalling, and biases from mechanical inputs. Here, we summarise this information, link it to classical embryology and propose a molecular framework for the establishment and regulation of developmental plasticity.
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Affiliation(s)
| | - Jennifer Nichols
- Wellcome Trust - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge CB2 3EH, UK
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