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Nelson CM. Mechanical Control of Cell Differentiation: Insights from the Early Embryo. Annu Rev Biomed Eng 2022; 24:307-322. [PMID: 35385680 DOI: 10.1146/annurev-bioeng-060418-052527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Differentiation is the process by which a cell activates the expression of tissue-specific genes, downregulates the expression of potency markers, and acquires the phenotypic characteristics of its mature fate. The signals that regulate differentiation include biochemical and mechanical factors within the surrounding microenvironment. We describe recent breakthroughs in our understanding of the mechanical control mechanisms that regulate differentiation, with a specific emphasis on the differentiation events that build the early mouse embryo. Engineering approaches to reproducibly mimic the mechanical regulation of differentiation will permit new insights into early development and applications in regenerative medicine. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Celeste M Nelson
- Departments of Chemical & Biological Engineering and Molecular Biology, Princeton University, Princeton, New Jersey USA;
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2
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Mori M, Yao T, Mishina T, Endoh H, Tanaka M, Yonezawa N, Shimamoto Y, Yonemura S, Yamagata K, Kitajima TS, Ikawa M. RanGTP and the actin cytoskeleton keep paternal and maternal chromosomes apart during fertilization. J Cell Biol 2021; 220:e202012001. [PMID: 34424312 PMCID: PMC8404465 DOI: 10.1083/jcb.202012001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 06/18/2021] [Accepted: 08/06/2021] [Indexed: 11/22/2022] Open
Abstract
Zygotes require two accurate sets of parental chromosomes, one each from the mother and the father, to undergo normal embryogenesis. However, upon egg-sperm fusion in vertebrates, the zygote has three sets of chromosomes, one from the sperm and two from the egg. The zygote therefore eliminates one set of maternal chromosomes (but not the paternal chromosomes) into the polar body through meiosis, but how the paternal chromosomes are protected from maternal meiosis has been unclear. Here we report that RanGTP and F-actin dynamics prevent egg-sperm fusion in proximity to maternal chromosomes. RanGTP prevents the localization of Juno and CD9, egg membrane proteins that mediate sperm fusion, at the cell surface in proximity to maternal chromosomes. Following egg-sperm fusion, F-actin keeps paternal chromosomes away from maternal chromosomes. Disruption of these mechanisms causes the elimination of paternal chromosomes during maternal meiosis. This study reveals a novel critical mechanism that prevents aneuploidy in zygotes.
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Affiliation(s)
- Masashi Mori
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Tatsuma Yao
- Research and Development Center, Fuso Pharmaceutical Industries, Ltd., Osaka, Japan
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama, Japan
| | - Tappei Mishina
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Hiromi Endoh
- Laboratory for Ultrastructural Research, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Masahito Tanaka
- Physics and Cell Biology Laboratory, National Institute of Genetics & Department of Genetics, SOKENDAI University, Kanagawa, Japan
| | - Nao Yonezawa
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama, Japan
| | - Yuta Shimamoto
- Physics and Cell Biology Laboratory, National Institute of Genetics & Department of Genetics, SOKENDAI University, Kanagawa, Japan
| | - Shigenobu Yonemura
- Laboratory for Ultrastructural Research, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
- Department of Cell Biology, Tokushima University Graduate School of Medical Science, Tokushima, Japan
| | - Kazuo Yamagata
- Graduate School of Biology-Oriented Science and Technology, Kindai University, Wakayama, Japan
| | - Tomoya S. Kitajima
- Laboratory for Chromosome Segregation, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
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3
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Cell fate determination and Hippo signaling pathway in preimplantation mouse embryo. Cell Tissue Res 2021; 386:423-444. [PMID: 34586506 DOI: 10.1007/s00441-021-03530-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 09/20/2021] [Indexed: 10/20/2022]
Abstract
First cell fate determination plays crucial roles in cell specification during early phases of embryonic development. Three classical concepts have been proposed to explain the lineage specification mechanism of the preimplantation embryo: inside-outside, pre-patterning, and polarity models. Transcriptional effectors of the Hippo signal pathway are YAP and TAZ activators that can create a shuttle between the cytoplasm and the nucleus. Despite different localizations of YAP in the cell, it determines the fate of ICM and TE. How the decisive cue driving factors that determine YAP localization are coordinated remains a central unanswered question. How can an embryonic cell find its position? The objective of this review is to summarize the molecular and mechanical aspects in cell fate decision during mouse preimplantation embryonic development. The findings will reveal the relationship between cell-cell adhesion, cell polarity, and determination of cell fate during early embryonic development in mice and elucidate the inducing/inhibiting mechanisms that are involved in cell specification following zygotic genome activation and compaction processes. With future studies, new biophysical and chemical cues in the cell fate determination will impart significant spatiotemporal effects on early embryonic development. The achieved knowledge will provide important information to the development of new approaches to be used in infertility treatment and increase the success of pregnancy.
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New Insights into the Mammalian Egg Zona Pellucida. Int J Mol Sci 2021; 22:ijms22063276. [PMID: 33806989 PMCID: PMC8005149 DOI: 10.3390/ijms22063276] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 03/19/2021] [Indexed: 12/23/2022] Open
Abstract
Mammalian oocytes are surrounded by an extracellular coat called the zona pellucida (ZP), which, from an evolutionary point of view, is the most ancient of the coats that envelope vertebrate oocytes and conceptuses. This matrix separates the oocyte from cumulus cells and is responsible for species-specific recognition between gametes, preventing polyspermy and protecting the preimplantation embryo. The ZP is a dynamic structure that shows different properties before and after fertilization. Until very recently, mammalian ZP was believed to be composed of only three glycoproteins, ZP1, ZP2 and ZP3, as first described in mouse. However, studies have revealed that this composition is not necessarily applicable to other mammals. Such differences can be explained by an analysis of the molecular evolution of the ZP gene family, during which ZP genes have suffered pseudogenization and duplication events that have resulted in differing models of ZP protein composition. The many discoveries made in recent years related to ZP composition and evolution suggest that a compilation would be useful. Moreover, this review analyses ZP biosynthesis, the role of each ZP protein in different mammalian species and how these proteins may interact among themselves and with other proteins present in the oviductal lumen.
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Trebichalská Z, Holubcová Z. Perfect date-the review of current research into molecular bases of mammalian fertilization. J Assist Reprod Genet 2020; 37:243-256. [PMID: 31909446 PMCID: PMC7056734 DOI: 10.1007/s10815-019-01679-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 12/22/2019] [Indexed: 12/21/2022] Open
Abstract
Fertilization is a multistep process during which two terminally differentiated haploid cells, an egg and a sperm, combine to produce a totipotent diploid zygote. In the early 1950s, it became possible to fertilize mammalian eggs in vitro and study the sequence of cellular and molecular events leading to embryo development. Despite all the achievements of assisted reproduction in the last four decades, remarkably little is known about the molecular aspects of human conception. Current fertility research in animal models is casting more light on the complexity of the process all our lives start with. This review article provides an update on the investigation of mammalian fertilization and highlights the practical implications of scientific discoveries in the context of human reproduction and reproductive medicine.
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Affiliation(s)
- Zuzana Trebichalská
- Faculty of Medicine, Department of Histology and Embryology, Masaryk University, Kamenice 5, Brno, Czech Republic
| | - Zuzana Holubcová
- Faculty of Medicine, Department of Histology and Embryology, Masaryk University, Kamenice 5, Brno, Czech Republic. .,Reprofit International, Clinic of Reproductive Medicine, Brno, Czech Republic.
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Abstract
Marsupials and monotremes differ from eutherian mammals in many features of their reproduction and development. Some features appear to be representative of transitional stages in evolution from therapsid reptiles to humans and mice, particularly with respect to the extraembryonic tissues that have undergone remarkable modifications to accommodate reduced egg size and quantity of yolk/deutoplasm, and increasing emphasis on viviparity and placentation. Trophoblast and hypoblast contribute the epithelial layers in most of the extraembryonic membranes and are the first two lineages to differentiate from the embryonic lineage. How they are specified varies greatly among mammals, perhaps largely due to heterochrony in the stage at which they must function. Differences probably also exist in the stage at which lineages are specified relative to the stage at which they fully commit to differentiation. The dogma of sequential commitment to trophoblast and hypoblast with progressive loss of potency may not be a fundamental feature of early mammalian development, but merely a recently acquired developmental pattern in eutherians, or at least mice.
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Hosseini SM, Moulavi F, TanhaieVash N, Shams-Esfandabadi N, Nasr-Esfahani MH, Shirazi A. Evidence of Oocyte Polarity in Bovine; Implications for Intracytoplasmic Sperm Injection and Somatic Cell Nuclear Transfer. CELL JOURNAL 2017; 19:482-491. [PMID: 28836411 PMCID: PMC5570413 DOI: 10.22074/cellj.2017.4887] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 09/19/2016] [Indexed: 12/03/2022]
Abstract
Objective We recently demonstrated spatial regionalization of maternal transcripts and
proteins within unfertilized ovine oocyte. Here, we investigated the likelihood of oocyte
polarity for the first time in bovine. Materials and Methods In this experimental study, in vitro matured bovine oocytes were
used for manual bisection [into oocyte halve that were near-to (HNS) and far-from (FS)
spindle] or trisection [into MII-spindle (S), the spindle-side half (NS), and the distal half
unassociated with the spindle (FS)]. Prepared pools of oocyte substructures were used
for comparative quantitative real-time polymerase chain reaction (RT-qPCR). To map the
possible preferential sperm entry point (SEP), the spatial relationship between SEP and
MII-spindle was measured 5 hours post-fertilization. Results The proportional amount of maternal mRNA in S oocyte fragment was estimated
to be 6 to 11-fold higher than NS and FS counterparts. The relative abundances
of Nanog, Oct4, Fgf4 and Tead4 were significantly higher in HNS oocyte fragment
compared t0 FS. The relative abundances of Ctnb, Carm1, Rex1, Sox2 and Cdx2 were
comparable between HNS and NS oocyte fragments. FS oocyte fragment possessed significantly
higher transcripts of Gata4 compared to HNS. The distribution of certain transcripts
related to pluripotency and lineage commitment were different depending upon the
region of the oocyte; either enriched at S (Tead4, Nanog, Ctnb and Sox2), NS (Oct4), or
FS (Gata6). The SEP in almost (90%) fertilized oocytes was located in MII-hemisphere. Conclusion The observation of spatial restriction of mRNAs and SEP within MII-oocyte
may indicate that the principal forces of oocyte polarity are evolutionary conserved. This
may in turn highlight the need for refinements in the methodology of intracytoplasmic
sperm injection (where a sperm is injected far from the MII-spindle) and somatic cell nuclear
transfer (where a major amount of regulative mRNAs that are associated with MIIspindle
is removed during enucleation).
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Affiliation(s)
- Seyed Morteza Hosseini
- Research Institute of Animal Embryo Technology, Shahrekord University, Shahrekord, Iran.,Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Fariba Moulavi
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Nima TanhaieVash
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | | | - Mohammad Hossein Nasr-Esfahani
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran.
| | - Abolfazl Shirazi
- Research Institute of Animal Embryo Technology, Shahrekord University, Shahrekord, Iran.,Reproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iran.
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Korotkevich E, Niwayama R, Courtois A, Friese S, Berger N, Buchholz F, Hiiragi T. The Apical Domain Is Required and Sufficient for the First Lineage Segregation in the Mouse Embryo. Dev Cell 2017; 40:235-247.e7. [PMID: 28171747 PMCID: PMC5300053 DOI: 10.1016/j.devcel.2017.01.006] [Citation(s) in RCA: 139] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 12/10/2016] [Accepted: 01/09/2017] [Indexed: 11/29/2022]
Abstract
Mammalian development begins with segregation of the extra-embryonic trophectoderm from the embryonic lineage in the blastocyst. While cell polarity and adhesion play key roles, the decisive cue driving this lineage segregation remains elusive. Here, to study symmetry breaking, we use a reduced system in which isolated blastomeres recapitulate the first lineage segregation. We find that in the 8-cell stage embryo, the apical domain recruits a spindle pole to ensure its differential distribution upon division. Daughter cells that inherit the apical domain adopt trophectoderm fate. However, the fate of apolar daughter cells depends on whether their position within the embryo facilitates apical domain formation by Cdh1-independent cell contact. Finally, we develop methods for transplanting apical domains and show that acquisition of this domain is not only required but also sufficient for the first lineage segregation. Thus, we provide mechanistic understanding that reconciles previous models for symmetry breaking in mouse development. A reduced system was established to study symmetry breaking in mouse development 8-cell stage blastomeres acquire the capacity to self-organize the apical domain The apical domain is required and sufficient for the first lineage segregation Contact asymmetry specifies cell fate, leading to self-organized embryo patterning
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Affiliation(s)
- Ekaterina Korotkevich
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Ritsuya Niwayama
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Aurélien Courtois
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Stefanie Friese
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Nicolas Berger
- Medical Systems Biology, UCC, University Hospital and Medical Faculty Carl Gustav Carus, TU Dresden, 01062 Dresden, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Frank Buchholz
- Medical Systems Biology, UCC, University Hospital and Medical Faculty Carl Gustav Carus, TU Dresden, 01062 Dresden, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Takashi Hiiragi
- Developmental Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany.
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9
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Localization in Oogenesis of Maternal Regulators of Embryonic Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 953:173-207. [DOI: 10.1007/978-3-319-46095-6_5] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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10
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Hosseini SM, Moulavi F, Tanhaie-Vash N, Asgari V, Ghanaei HR, Abedi-Dorche M, Jafarzadeh N, Gourabi H, Shahverdi AH, Dizaj AV, Shirazi A, Nasr-Esfahani MH. The Principal Forces of Oocyte Polarity Are Evolutionary Conserved but May Not Affect the Contribution of the First Two Blastomeres to the Blastocyst Development in Mammals. PLoS One 2016; 11:e0148382. [PMID: 27030988 PMCID: PMC4816511 DOI: 10.1371/journal.pone.0148382] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 01/18/2016] [Indexed: 11/26/2022] Open
Abstract
Oocyte polarity and embryonic patterning are well-established features of development in lower species. Whether a similar form of pre-patterning exists in mammals is currently under hot debate in mice. This study investigated this issue for the first time in ovine as a large mammal model. Microsurgical trisection of unfertilized MII-oocytes revealed that cortical cytoplasm around spindle (S) contained significant amounts of total maternal mRNAs and proteins compared to matched cytoplast hemispheres that were located either near (NS) or far (FS) -to-spindle. RT-qPCR provided striking examples of maternal mRNA localized to subcellular substructures S (NPM2, GMNN, H19, PCAF, DNMT3A, DNMT1, and STELLA), NS (SOX2, NANOG, POU5F1, and TET1), and FS (GCN) of MII oocyte. Immunoblotting revealed that specific maternal proteins DNMT3A and NANOG were asymmetrically enriched in MII-spindle-half of the oocytes. Topological analysis of sperm entry point (SEP) revealed that sperm preferentially entered via the MII-spindle-half of the oocytes. Even though, the topological position of first cleavage plane with regard to SEP was quite stochastic. Spatial comparison of lipid content revealed symmetrical distribution of lipids between 2-cell blastomeres. Lineage tracing using Dil, a fluorescent dye, revealed that while the progeny of leading blastomere of 2-cell embryos contributed to more cells in the developed blastocysts compared to lagging counterpart, the contributions of leading and lagging blastomeres to the embryonic-abembryonic parts of the developed blastocysts were almost unbiased. And finally, separated sister blastomeres of 2-cell embryos had an overall similar probability to arrest at any stage before the blastocyst (2-cell, 4-cell, 8-cell, and morula) or to achieve the blastocyst stage. It was concluded that the localization of maternal mRNAs and proteins at the spindle are evolutionarily conserved between mammals unfertilized ovine oocyte could be considered polar with respect to the spatial regionalization of maternal transcripts and proteins. Even though, the principal forces of this definitive oocyte polarity may not persist during embryonic cleavages.
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Affiliation(s)
- Sayyed-Morteza Hosseini
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Fariba Moulavi
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Nima Tanhaie-Vash
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Vajihe Asgari
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Hamid-Reza Ghanaei
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Maryam Abedi-Dorche
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Naser Jafarzadeh
- Department of Medical Physics, Tarbiat Modares University, Tehran, Iran
| | - Hossein Gourabi
- Department of Genetics at Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, P.O. Box: 19395–4644, Tehran, Iran
| | - Abdol-Hossein Shahverdi
- Department of Embryology at Reproductive Biomedicine Research Center, Royan Institute for Reproductive Medicine, ACECR, Tehran, Iran
| | - Ahmad Vosough Dizaj
- Department of Reproductive Imaging at Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Abolfazl Shirazi
- Reproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iran
- Research Institute of Animal Embryo Technology, Shahrekord University, Shahrekord, Iran
- * E-mail: (AS); (MHNE)
| | - Mohammad-Hossein Nasr-Esfahani
- Department of Reproductive Biotechnology, Reproductive Biomedicine Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
- * E-mail: (AS); (MHNE)
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11
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Abstract
Whether or not early mammalian development results from preformation or epigenesis remains an unresolved issue. Evidence for or against either is weak, inconclusive, and often misinterpreted. Yet, one can parsimoniously conceptualize formation of the mouse blastocyst as a series of random, stochastic events stemming from initial and sequential small asymmetries in egg, zygote, and cleavage stages. Differential compartmentalized gene expression does not lead but follows the morphogenesis and cell fate allocation in the mammalian blastocyst.
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12
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Lorthongpanich C, Issaragrisil S. Emerging Role of the Hippo Signaling Pathway in Position Sensing and Lineage Specification in Mammalian Preimplantation Embryos. Biol Reprod 2015; 92:143. [PMID: 25947059 DOI: 10.1095/biolreprod.114.127803] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 04/29/2015] [Indexed: 12/29/2022] Open
Abstract
In preimplantation mouse embryos, the first lineage differentiation takes place in the 8- to 16-cell-stage embryo and results in formation of the trophectoderm (TE) and inner cell mass (ICM), which will give rise to the trophoblast of the placenta and the embryo proper, respectively. Although, it is widely accepted that positioning of a cell within the embryo influences lineage differentiation, the mechanism underlying differential lineage differentiation and how it involves cell position are largely unknown. Interestingly, novel cues from the Hippo pathway have been recently demonstrated in the preimplantation mouse embryo. Unlike the mechanisms reported from epithelium-cultured cells, the Hippo pathway was found to be responsible for translating positional information to lineage specification through a position-sensing mechanism. Disruption of Hippo pathway-component genes in early embryos results in failure of lineage specification and failure of postimplantation development. In this review, we discuss the unique role of the Hippo signaling pathway in early embryo development and its role in lineage specification. Understanding the activity and regulation of the Hippo pathway may offer new insights into other areas of developmental biology that evolve from understanding of this cell-fate specification in the early embryonic cell.
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Affiliation(s)
- Chanchao Lorthongpanich
- Siriraj Center of Excellence for Stem Cell Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Surapol Issaragrisil
- Siriraj Center of Excellence for Stem Cell Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
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13
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Qiao J, Wang ZB, Feng HL, Miao YL, Wang Q, Yu Y, Wei YC, Yan J, Wang WH, Shen W, Sun SC, Schatten H, Sun QY. The root of reduced fertility in aged women and possible therapentic options: current status and future perspects. Mol Aspects Med 2013; 38:54-85. [PMID: 23796757 DOI: 10.1016/j.mam.2013.06.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 06/06/2013] [Indexed: 12/21/2022]
Abstract
It is well known that maternal ageing not only causes increased spontaneous abortion and reduced fertility, but it is also a high genetic disease risk. Although assisted reproductive technologies (ARTs) have been widely used to treat infertility, the overall success is still low. The main reasons for age-related changes include reduced follicle number, compromised oocyte quality especially aneuploidy, altered reproductive endocrinology, and increased reproductive tract defect. Various approaches for improving or treating infertility in aged women including controlled ovarian hyperstimulation with intrauterine insemination (IUI), IVF/ICSI-ET, ovarian reserve testing, preimplantation genetic diagnosis and screening (PGD/PGS), oocyte selection and donation, oocyte and ovary tissue cryopreservation before ageing, miscarriage prevention, and caloric restriction are summarized in this review. Future potential reproductive techniques for infertile older women including oocyte and zygote micromanipulations, derivation of oocytes from germ stem cells, ES cells, and iPS cells, as well as through bone marrow transplantation are discussed.
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Affiliation(s)
- Jie Qiao
- Center of Reproductive Medicine, Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, People's Republic of China
| | - Zhen-Bo Wang
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Huai-Liang Feng
- Department of Laboratory Medicine, and Obstetrics and Gynecology, New York Hospital Queens, Weill Medical College of Cornell University, New York, NY, USA
| | - Yi-Liang Miao
- Reproductive Medicine Group, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Qiang Wang
- Department of Obstetrics and Gynecology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA
| | - Yang Yu
- Center of Reproductive Medicine, Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, People's Republic of China
| | - Yan-Chang Wei
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Jie Yan
- Center of Reproductive Medicine, Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, People's Republic of China
| | - Wei-Hua Wang
- Houston Fertility Institute, Tomball Regional Hospital, Tomball, TX 77375, USA
| | - Wei Shen
- Laboratory of Germ Cell Biology, Department of Animal Science, Qingdao Agricultural University, Qingdao 266109, People's Republic of China
| | - Shao-Chen Sun
- Department of Animal Science, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
| | - Heide Schatten
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
| | - Qing-Yuan Sun
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.
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14
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Tabansky I, Lenarcic A, Draft RW, Loulier K, Keskin DB, Rosains J, Rivera-Feliciano J, Lichtman JW, Livet J, Stern JNH, Sanes JR, Eggan K. Developmental bias in cleavage-stage mouse blastomeres. Curr Biol 2013; 23:21-31. [PMID: 23177476 PMCID: PMC3543519 DOI: 10.1016/j.cub.2012.10.054] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 07/17/2012] [Accepted: 10/30/2012] [Indexed: 01/08/2023]
Abstract
BACKGROUND The cleavage-stage mouse embryo is composed of superficially equivalent blastomeres that will generate both the embryonic inner cell mass (ICM) and the supportive trophectoderm (TE). However, it remains unsettled whether the contribution of each blastomere to these two lineages can be accounted for by chance. Addressing the question of blastomere cell fate may be of practical importance, because preimplantation genetic diagnosis requires removal of blastomeres from the early human embryo. To determine whether blastomere allocation to the two earliest lineages is random, we developed and utilized a recombination-mediated, noninvasive combinatorial fluorescent labeling method for embryonic lineage tracing. RESULTS When we induced recombination at cleavage stages, we observed a statistically significant bias in the contribution of the resulting labeled clones to the trophectoderm or the inner cell mass in a subset of embryos. Surprisingly, we did not find a correlation between localization of clones in the embryonic and abembryonic hemispheres of the late blastocyst and their allocation to the TE and ICM, suggesting that TE-ICM bias arises separately from embryonic-abembryonic bias. Rainbow lineage tracing also allowed us to demonstrate that the bias observed in the blastocyst persists into postimplantation stages and therefore has relevance for subsequent development. CONCLUSIONS The Rainbow transgenic mice that we describe here have allowed us to detect lineage-dependent bias in early development. They should also enable assessment of the developmental equivalence of mammalian progenitor cells in a variety of tissues.
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Affiliation(s)
- Inna Tabansky
- The Howard Hughes Medical Institute, Harvard Stem Cell Institute and Department of Stem Cell and Regenerative Biology, Harvard University
- The Department of Molecular and Cellular Biology, Harvard University
| | - Alan Lenarcic
- Department of Genetics, University of North Carolina at Chapel Hill
| | - Ryan W. Draft
- The Department of Molecular and Cellular Biology, Harvard University
- Center for Brain Science, Harvard University
| | - Karine Loulier
- Institut de la Vision, INSERM U968, UPMC Univ Paris 06 UMR_S 968 and CNRS UMR_7210, Paris, France
| | - Derin B Keskin
- Department of Developmental Biology, Harvard School of Dental Medicine
- Dana Farber Cancer Institute, Department of Medical Oncology, Harvard Medical School
| | | | - José Rivera-Feliciano
- The Howard Hughes Medical Institute, Harvard Stem Cell Institute and Department of Stem Cell and Regenerative Biology, Harvard University
| | - Jeff W. Lichtman
- The Department of Molecular and Cellular Biology, Harvard University
- Center for Brain Science, Harvard University
| | - Jean Livet
- Institut de la Vision, INSERM U968, UPMC Univ Paris 06 UMR_S 968 and CNRS UMR_7210, Paris, France
| | - Joel NH Stern
- Department of Developmental Biology, Harvard School of Dental Medicine
| | - Joshua R. Sanes
- The Department of Molecular and Cellular Biology, Harvard University
- Center for Brain Science, Harvard University
| | - Kevin Eggan
- The Howard Hughes Medical Institute, Harvard Stem Cell Institute and Department of Stem Cell and Regenerative Biology, Harvard University
- The Department of Molecular and Cellular Biology, Harvard University
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15
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Actin cytoskeleton in cell polarity and asymmetric division during mouse oocyte maturation. Cytoskeleton (Hoboken) 2012; 69:727-37. [DOI: 10.1002/cm.21048] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 06/18/2012] [Accepted: 06/21/2012] [Indexed: 12/22/2022]
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16
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Littwin T, Denker HW. Segregation during cleavage in the mammalian embryo? A critical comparison of whole-mount/CLSM and section immunohistochemistry casts doubts on segregation of axis-relevant leptin domains in the rabbit. Histochem Cell Biol 2011; 135:553-70. [PMID: 21626127 DOI: 10.1007/s00418-011-0816-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2011] [Indexed: 11/30/2022]
Abstract
Segregation of certain cytoplasmic molecules during cleavage and blastocyst formation that was previously reported to occur in the human and the mouse (Antczak and Van Blerkom Mol Hum Reprod 3:1067-1086, 1997; Antczak and Van Blerkom Hum Reprod 14:429-447, 1999) has been reinvestigated in the rabbit model. Additional methodology was used and two approaches were compared: (1) whole-mount immunohistochemistry followed by confocal laser scanning microscopy (WM-IHC/CLSM) versus (2) IHC performed on histological sections of resin-embedded material (S-IHC). This study concentrates on leptin and cytoskeletal proteins (actin and cytokeratins). With S-IHC, leptin was localized predominantly on the surface of blastomeres which is facing the perivitelline space, and in the extracellular embryonic coats, without any polar asymmetry being detectable along (presumptive) embryonic axes. A polar distribution of leptin with a pattern that could be interpreted as predictive of the prospective embryonic-abembryonic axis was seen only with WM-IHC/CLSM, not with S-IHC, although the latter gave excellent resolution. With both techniques, no differences between blastomeres were detected with respect to actin and cytokeratin patterns, an increased expression of cytokeratin in trophoblast cells occurring no earlier than at blastocyst formation. Artifacts that can occur with the two methodological approaches are critically discussed, as is the possible significance of the findings for theories on the differentiation of trophoblast versus embryoblast and on axis formation in early mammalian development. It is concluded that these data call for cautioning when studying distribution patterns of diffusible molecules with WM-IHC/CLSM technology, whereas patterns obtained with S-IHC are more reliable. Specifically these data cast doubts on previous claims that leptin IHC would allow to monitor cytoplasmic domain segregation occurring during cleavage as an element of early embryonic pattern/axis formation.
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Affiliation(s)
- T Littwin
- Institut für Anatomie, Lehrstuhl für Anatomie und Entwicklungsbiologie, Universität Duisburg-Essen, Hufelandstr. 55, 45122, Essen, Germany.
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17
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VerMilyea MD, Maneck M, Yoshida N, Blochberger I, Suzuki E, Suzuki T, Spang R, Klein CA, Perry ACF. Transcriptome asymmetry within mouse zygotes but not between early embryonic sister blastomeres. EMBO J 2011; 30:1841-51. [PMID: 21468028 DOI: 10.1038/emboj.2011.92] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 03/03/2011] [Indexed: 11/09/2022] Open
Abstract
Transcriptome regionalization is an essential polarity determinant among metazoans, directing embryonic axis formation during normal development. Although conservation of this principle in mammals is assumed, recent evidence is conflicting and it is not known whether transcriptome asymmetries exist within unfertilized mammalian eggs or between the respective cleavage products of early embryonic divisions. We here address this by comparing transcriptome profiles of paired single cells and sub-cellular structures obtained microsurgically from mouse oocytes and totipotent embryos. Paired microsurgical spindle and remnant samples from unfertilized metaphase II oocytes possessed distinguishable profiles. Fertilization produces a totipotent 1-cell embryo (zygote) and associated spindle-enriched second polar body whose paired profiles also differed, reflecting spindle transcript enrichment. However, there was no programmed transcriptome asymmetry between sister cells within 2- or 3-cell embryos. Accordingly, there is transcriptome asymmetry within mouse oocytes, but not between the sister blastomeres of early embryos. This work places constraints on pre-patterning in mammals and provides documentation correlating potency changes and transcriptome partitioning at the single-cell level.
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Affiliation(s)
- Matthew D VerMilyea
- Laboratory of Mammalian Molecular Embryology, RIKEN Center for Developmental Biology, Kobe, Japan
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18
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Brunet S, Verlhac MH. Positioning to get out of meiosis: the asymmetry of division. Hum Reprod Update 2010; 17:68-75. [DOI: 10.1093/humupd/dmq044] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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19
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Simerly CR, Castro CA, Jacoby E, Grund K, Turpin J, McFarland D, Champagne J, Jimenez JB, Frost P, Bauer C, Hewitson L, Schatten G. Assisted Reproductive Technologies (ART) with baboons generate live offspring: a nonhuman primate model for ART and reproductive sciences. Reprod Sci 2010; 17:917-30. [PMID: 20631291 DOI: 10.1177/1933719110374114] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Human reproduction has benefited significantly by investigating nonhuman primate (NHP) models, especially rhesus macaques. To expand the Old World monkey species available for human reproductive studies, we present protocols in baboons, our closest Old World primate relatives, for assisted reproductive technologies (ART) leading to live born offspring. Baboons complement rhesus by confirming or modifying observations generated in humans often obtained by the study of clinically discarded specimens donated by anonymous infertility patient couples. Here, baboon ART protocols, including oocyte collection, in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), preimplantation development to blastocyst stage, and embryo transfer techniques are described. With baboon ART methodologies in place, motility during baboon fertilization was investigated by time-lapse video microscopy (TLVM). The first ART baboons produced by ICSI, a pair of male twins, were delivered naturally at 165 days postgestation. Genetic testing of these twins confirmed their ART parental origins and demonstrated that they are unrelated fraternal twins not identicals. These results have implications for ART outcomes, embryonic stem cell (ESC) derivation, and reproductive sciences.
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Affiliation(s)
- Calvin R Simerly
- Division of Developmental and Regenerative Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, Pittsburgh Development Center; Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, PA 15213, USA
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20
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Abstract
A mature animal body contains a variety of different cell types, and these cells are distributed in a well-organized fashion along the body axes. One of the major questions in developmental biology is how cells acquire different characteristics. In addition, it is important to understand how the embryo forms the body axes and how cells are allocated along these axes during development. Among mammalian species, the molecular mechanisms that regulate embryonic development have been well analyzed and characterized in mice. Here, mouse preimplantation embryonic development is briefly summarized and our current understanding of this complex process based on recent observations is reviewed.
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Affiliation(s)
- Toshihiko Fujimori
- Division of Embryology, National Institute for Basic Biology, Okazaki, Aichi, Japan.
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21
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Abstract
This review describes the three classical models (mosaic, positional, and polarization) proposed to explain blastocyst formation and summarizes the evidence concerning them. It concludes that the polarization model incorporates elements of the other two models and best explains most known information. I discuss key requirements of a molecular basis for the generation and stabilization of polarity and identify ezrin/E-cadherin, PAR proteins, and Cdx2 as plausible key molecular players. I also discuss the idea of a network process operating to build cell allocations progressively into committed differences. Finally, this review critically considers the possibility of developmental information being encoded within the oocyte and zygote. No final decision can be reached on a mechanism of action underlying any encoded information, but a cell interaction process model is preferred over one that relies solely on differential inheritance.
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Affiliation(s)
- Martin H Johnson
- Department of Physiology, Development, and Neuroscience and Center for Trophoblast Research, The Anatomy School, Cambridge CB2 3DY, United Kingdom.
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22
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23
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Evsikov AV, Marín de Evsikova C. Gene expression during the oocyte-to-embryo transition in mammals. Mol Reprod Dev 2009; 76:805-18. [PMID: 19363788 DOI: 10.1002/mrd.21038] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The seminal question in modern developmental biology is the origins of new life arising from the unification of sperm and egg. The roots of this question begin from 19th to 20th century embryologists studying fertilization and embryogenesis. Although the revolution of molecular biology has yielded significant insight into the complexity of this process, the overall orchestration of genes, molecules, and cells is still not fully formed. Early mammalian development, specifically the oocyte-to-embryo transition, is essentially under "maternal command" from factors deposited in the cytoplasm during oocyte growth, independent of de novo transcription from the nascent embryo. Many of the advances in understanding this developmental period occurred in tandem with application of new methods and techniques from molecular biology, from protein electrophoresis to sequencing and assemblies of whole genomes. From this bed of knowledge, it appears that precise control of mRNA translation is a key regulator coordinating the molecular and cellular events occurring during oocyte-to-embryo transition. Notably, oocyte transcriptomes share, yet retain some uniqueness, common genetic motifs among all chordates. The common genetic motifs typically define fundamental processes critical for cellular maintenance, whereas the unique genetic features may be a source of variation and a substrate for sexual selection, genetic drift, or gene flow. One purpose for this complex interplay among genes, proteins, and cells may allow for evolution to transform and act upon the underlying processes, at molecular, structural and organismal levels, to increase diversity, which is the ultimate goal of sexual reproduction.
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24
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PARK SK, WON C, CHOI YJ, KANG H, ROH S. The Leading Blastomere of the 2-Cell Stage Parthenogenetic Porcine Embryo Contributes to the Abembryonic Part First. J Vet Med Sci 2009; 71:569-76. [DOI: 10.1292/jvms.71.569] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Sang Kyu PARK
- Embryo Biotechnology Laboratory, CLS21 and Dental Research Institute, Seoul National University School of Dentistry
| | - Cheolhee WON
- Embryo Biotechnology Laboratory, CLS21 and Dental Research Institute, Seoul National University School of Dentistry
| | - Young-Ju CHOI
- Embryo Biotechnology Laboratory, CLS21 and Dental Research Institute, Seoul National University School of Dentistry
| | - Hoin KANG
- Embryo Biotechnology Laboratory, CLS21 and Dental Research Institute, Seoul National University School of Dentistry
| | - Sangho ROH
- Embryo Biotechnology Laboratory, CLS21 and Dental Research Institute, Seoul National University School of Dentistry
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25
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Mouse early oocytes are transiently polar: three-dimensional and ultrastructural analysis. Exp Cell Res 2008; 314:3245-54. [PMID: 18662685 DOI: 10.1016/j.yexcr.2008.07.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Revised: 07/07/2008] [Accepted: 07/07/2008] [Indexed: 11/22/2022]
Abstract
The oocytes of many invertebrate and non-mammalian vertebrate species are not only asymmetrical but also polar in the distribution of organelles, localized RNAs and proteins, and the oocyte polarity dictates the patterning of the future embryo. Polarily located within the oocytes of many species is the Balbiani body (Bb), which in Xenopus is known to be associated with the germinal granules responsible for the determination of germ cell fate. In contrast, in mammals, it is widely believed that the patterning of the embryo does not occur before implantation, and that oocytes are non-polar and symmetrical. Although the oocytes of many mammals, including mice and humans, contain Bbs, it remains unknown how and if the presence of Bbs relates to mouse oocyte and egg polarity. Using three-dimensional reconstruction of mouse neonatal oocytes, we showed that mouse early oocytes are both asymmetrical and transiently polar. In addition, the specifics of polarity in mouse oocytes are highly reminiscent of those in Xenopus early oocytes. Based on these findings, we conclude that the polarity of early oocytes imposed by the position of the centrioles at the cytoplasmic bridges is a fundamental and ancestral feature across the animal kingdom.
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Bauer T, Motosugi N, Miura K, Sabe H, Hiiragi T. Dynamic rearrangement of surface proteins is essential for cytokinesis. Genesis 2008; 46:152-62. [PMID: 18327789 DOI: 10.1002/dvg.20377] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cytokinesis is a complex process that involves dynamic cortical rearrangement. Our recent time-lapse recordings of the mouse egg unexpectedly revealed a high motility of the second polar body (2pb). Experiments to address its underlying mechanism show that neither mechanical compression by the zona pellucida nor the connection via the mid-body is required for the 2pb movement. Time-lapse recordings establish that the 2pb moves together with the cell membrane. These recordings, in which cell surface proteins are labeled with fluorescent latex-microbeads or monovalent antibodies against whole mouse proteins, indicate that the majority of the surface proteins dynamically accumulate in the cleavage furrow at every cell division. Comparable dynamics of the cell surface proteins, and specifically of E-cadherin, are also observed in cultured epithelial cells. The surface protein dynamics are closely correlated with, and dependent on, those of the underlying cortical actin. The cortical actin network may form a scaffold for membrane proteins and thereby transfer them during contractile ring formation toward the cleavage furrow. Immobilization of surface proteins by tetravalent lectin-mediated crosslinking results in the failure of cleavage, demonstrating that the observed protein dynamics are essential for cytokinesis. We propose that dynamic rearrangement of the cell surface proteins is a common feature of cytokinesis, playing a key role in modifying the mechanical properties of the cell membrane during cortical ingression.
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Affiliation(s)
- Tobias Bauer
- Department of Developmental Biology, Max-Planck Institute of Immunobiology, Freiburg D-79108, Germany
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27
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Ninomiya Y, Ichinose S. Subcellular distribution of mitochondrial ribosomal RNA in the mouse oocyte and zygote. PLoS One 2007; 2:e1241. [PMID: 18043748 PMCID: PMC2082410 DOI: 10.1371/journal.pone.0001241] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 11/05/2007] [Indexed: 11/19/2022] Open
Abstract
Mitochondrial ribosomal RNAs (mtrRNAs) have been reported to translocate extra-mitochondrially and localize to the germ cell determinant of oocytes and zygotes in some metazoa except mammals. To address whether the mtrRNAs also localize in the mammals, expression and distribution of mitochondrion-encoded RNAs in the mouse oocytes and zygotes was examined by whole-mount in situ hybridization (ISH). Both 12S and 16S rRNAs were predominantly distributed in the animal hemisphere of the mature oocyte. This distribution pattern was rearranged toward the second polar body in zygotes after fertilization. The amount of mtrRNAs decreased around first cleavage, remained low during second cleavage and increased after third cleavage. Staining intensity of the 12S rRNA was weaker than that of the 16S rRNA throughout the examined stages. Similar distribution dynamics of the 16S rRNA was observed in strontium-activated haploid parthenotes, suggesting the distribution rearrangement does not require a component from sperm. The distribution of 16S rRNAs did not coincide with that of mitochondrion-specific heat shock protein 70, suggesting that the mtrRNA is translocated from mitochondria. The ISH-scanning electron microscopy confirms the extra-mitochondrial mtrRNA in the mouse oocyte. Chloramphenicol (CP) treatment of late pronuclear stage zygotes perturbed first cleavage as judged by the greater than normal disparity in size of blastomeres of 2-cell conceptuses. Two-third of the CP-treated zygotes arrested at either 2-cell or 3-cell stage even after the CP was washed out. These findings indicate that the extra-mitochondrial mtrRNAs are localized in the mouse oocyte and implicated in correct cytoplasmic segregation into blastomeres through cleavages of the zygote.
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Affiliation(s)
- Youichirou Ninomiya
- Mammalian Development Laboratory, Department of Zoology, University of Oxford, Oxford, United Kingdom.
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