1
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Ohta N, Christiaen L. Cellular remodeling and JAK inhibition promote zygotic gene expression in the Ciona germline. EMBO Rep 2024; 25:2188-2201. [PMID: 38649664 PMCID: PMC11094015 DOI: 10.1038/s44319-024-00139-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/22/2024] [Accepted: 03/28/2024] [Indexed: 04/25/2024] Open
Abstract
Transcription control is a major determinant of cell fate decisions in somatic tissues. By contrast, early germline fate specification in numerous vertebrate and invertebrate species relies extensively on RNA-level regulation, exerted on asymmetrically inherited maternal supplies, with little-to-no zygotic transcription. However delayed, a maternal-to-zygotic transition is nevertheless poised to complete the deployment of pre-gametic programs in the germline. Here, we focus on early germline specification in the tunicate Ciona to study zygotic genome activation. We first demonstrate that a peculiar cellular remodeling event excludes localized postplasmic Pem-1 mRNA, which encodes the general inhibitor of transcription. Subsequently, zygotic transcription begins in Pem-1-negative primordial germ cells (PGCs), as revealed by histochemical detection of elongating RNA Polymerase II, and nascent Mef2 transcripts. In addition, we uncover a provisional antagonism between JAK and MEK/BMPRI/GSK3 signaling, which controls the onset of zygotic gene expression, following cellular remodeling of PGCs. We propose a 2-step model for the onset of zygotic transcription in the Ciona germline and discuss the significance of germ plasm dislocation and remodeling in the context of developmental fate specification.
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Affiliation(s)
- Naoyuki Ohta
- Michael Sars Centre, University of Bergen, Bergen, Norway.
| | - Lionel Christiaen
- Michael Sars Centre, University of Bergen, Bergen, Norway.
- Center for Developmental Genetics, Department of Biology, New York University, New York, NY, USA.
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2
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Frese AN, Mariossi A, Levine MS, Wühr M. Quantitative proteome dynamics across embryogenesis in a model chordate. iScience 2024; 27:109355. [PMID: 38510129 PMCID: PMC10951915 DOI: 10.1016/j.isci.2024.109355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 12/11/2023] [Accepted: 02/23/2024] [Indexed: 03/22/2024] Open
Abstract
The evolution of gene expression programs underlying the development of vertebrates remains poorly characterized. Here, we present a comprehensive proteome atlas of the model chordate Ciona, covering eight developmental stages and ∼7,000 translated genes, accompanied by a multi-omics analysis of co-evolution with the vertebrate Xenopus. Quantitative proteome comparisons argue against the widely held hourglass model, based solely on transcriptomic profiles, whereby peak conservation is observed during mid-developmental stages. Our analysis reveals maximal divergence at these stages, particularly gastrulation and neurulation. Together, our work provides a valuable resource for evaluating conservation and divergence of multi-omics profiles underlying the diversification of vertebrates.
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Affiliation(s)
- Alexander N. Frese
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Andrea Mariossi
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Michael S. Levine
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Martin Wühr
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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3
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Li Y, Chen S, Liu W, Zhao D, Gao Y, Hu S, Liu H, Li Y, Qu L, Liu X. A full-body transcription factor expression atlas with completely resolved cell identities in C. elegans. Nat Commun 2024; 15:358. [PMID: 38195740 PMCID: PMC10776613 DOI: 10.1038/s41467-023-42677-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 10/18/2023] [Indexed: 01/11/2024] Open
Abstract
Invariant cell lineage in C. elegans enables spatiotemporal resolution of transcriptional regulatory mechanisms controlling the fate of each cell. Here, we develop RAPCAT (Robust-point-matching- And Piecewise-affine-based Cell Annotation Tool) to automate cell identity assignment in three-dimensional image stacks of L1 larvae and profile reporter expression of 620 transcription factors in every cell. Transcription factor profile-based clustering analysis defines 80 cell types distinct from conventional phenotypic cell types and identifies three general phenotypic modalities related to these classifications. First, transcription factors are broadly downregulated in quiescent stage Hermaphrodite Specific Neurons, suggesting stage- and cell type-specific variation in transcriptome size. Second, transcription factor expression is more closely associated with morphology than other phenotypic modalities in different pre- and post-differentiation developmental stages. Finally, embryonic cell lineages can be associated with specific transcription factor expression patterns and functions that persist throughout postembryonic life. This study presents a comprehensive transcription factor atlas for investigation of intra-cell type heterogeneity.
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Affiliation(s)
- Yongbin Li
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Siyu Chen
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Weihong Liu
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Intelligent Perception Lab, Hanwang Technology Co., Ltd, Beijing, 100193, China
| | - Di Zhao
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Tianjin Key Laboratory of Exercise Physiology and Sports Medicine, Institute of Sport, Exercise & Health, Tianjin University of Sport, Tianjin, 300381, China
| | - Yimeng Gao
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Shipeng Hu
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Hanyu Liu
- College of Life Sciences, Capital Normal University, Beijing, 100048, China
| | - Yuanyuan Li
- Ministry of Education Key Laboratory of Intelligent Computation & Signal Processing, Information Materials and Intelligent Sensing Laboratory of Anhui Province, School of Electronics and Information Engineering, Anhui University, Hefei, 230039, China
| | - Lei Qu
- Ministry of Education Key Laboratory of Intelligent Computation & Signal Processing, Information Materials and Intelligent Sensing Laboratory of Anhui Province, School of Electronics and Information Engineering, Anhui University, Hefei, 230039, China
| | - Xiao Liu
- College of Life Sciences, Capital Normal University, Beijing, 100048, China.
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4
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Tokuoka M, Satou Y. A digital twin reproducing gene regulatory network dynamics of early Ciona embryos indicates robust buffers in the network. PLoS Genet 2023; 19:e1010953. [PMID: 37756274 PMCID: PMC10530022 DOI: 10.1371/journal.pgen.1010953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 09/01/2023] [Indexed: 09/29/2023] Open
Abstract
How gene regulatory networks (GRNs) encode gene expression dynamics and how GRNs evolve are not well understood, although these problems have been studied extensively. We created a digital twin that accurately reproduces expression dynamics of 13 genes that initiate expression in 32-cell ascidian embryos. We first showed that gene expression patterns can be manipulated according to predictions by this digital model. Next, to simulate GRN rewiring, we changed regulatory functions that represented their regulatory mechanisms in the digital twin, and found that in 55 of 100 cases, removal of a single regulator from a conjunctive clause of Boolean functions did not theoretically alter qualitative expression patterns of these genes. In other words, we found that more than half the regulators gave theoretically redundant temporal or spatial information to target genes. We experimentally substantiated that the expression pattern of Nodal was maintained without one of these factors, Zfpm, by changing the upstream regulatory sequence of Nodal. Such robust buffers of regulatory mechanisms may provide a basis of enabling developmental system drift, or rewiring of GRNs without changing expression patterns of downstream genes, during evolution.
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Affiliation(s)
- Miki Tokuoka
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto, Japan
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5
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Treen N, Chavarria E, Weaver CJ, Brangwynne CP, Levine M. An FGF timer for zygotic genome activation. Genes Dev 2023; 37:80-85. [PMID: 36801820 PMCID: PMC10069452 DOI: 10.1101/gad.350164.122] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 01/19/2023] [Indexed: 02/19/2023]
Abstract
Zygotic genome activation has been extensively studied in a variety of systems including flies, frogs, and mammals. However, there is comparatively little known about the precise timing of gene induction during the earliest phases of embryogenesis. Here we used high-resolution in situ detection methods, along with genetic and experimental manipulations, to study the timing of zygotic activation in the simple model chordate Ciona with minute-scale temporal precision. We found that two Prdm1 homologs in Ciona are the earliest genes that respond to FGF signaling. We present evidence for a FGF timing mechanism that is driven by ERK-mediated derepression of the ERF repressor. Depletion of ERF results in ectopic activation of FGF target genes throughout the embryo. A highlight of this timer is the sharp transition in FGF responsiveness between the eight- and 16-cell stages of development. We propose that this timer is an innovation of chordates that is also used by vertebrates.
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Affiliation(s)
- Nicholas Treen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA;
| | - Emily Chavarria
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Claire J Weaver
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Clifford P Brangwynne
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
- Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA
| | - Michael Levine
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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6
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Nishida H, Matsuo M, Konishi S, Ohno N, Manni L, Onuma TA. Germline development during embryogenesis of the larvacean, Oikopleura dioica. Dev Biol 2021; 481:188-200. [PMID: 34755656 DOI: 10.1016/j.ydbio.2021.10.009] [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: 07/21/2021] [Revised: 10/08/2021] [Accepted: 10/24/2021] [Indexed: 11/18/2022]
Abstract
Germ cells develop into eggs and sperms and represent a lineage that survives through multiple generations. Germ cell specification during embryogenesis proceeds through one of two basic modes: either the cell-autonomous mode or the inductive mode. In the cell-autonomous mode, specification of germ cell fate involves asymmetric partitioning of the specialized maternal cytoplasm, known as the germplasm. Oikopleura dioica is a larvacean (class Appendicularia) and a chordate. It is regarded as a promising animal model for studying chordate development because of its short life cycle (5 days) and small genome size (∼60 Mb). We show that their embryos possess germplasm, as observed in ascidians (class Ascidiacea). The vegetal cytoplasm shifted towards the future posterior pole before the first cleavage occurred. A bilateral pair of primordial germ cells (PGC, B11 cells) was formed at the posterior pole at the 32-cell stage through two rounds of unequal cleavage. These B11 cells did not undergo further division before hatching of the tadpole-shaped larvae. The centrosome-attracting body (CAB) is a subcellular structure that contains the germplasm and plays crucial roles in germ cell development in ascidians. The presence of CAB with germplasm was observed in the germline lineage cells of larvaceans via electron microscopy and using extracted embryos. The CAB appeared at the 8-cell stage and persisted until the middle stage of embryogenesis. The antigen for the phosphorylated histone 3 antibody was localized to the CAB and persisted in the PGC until hatching after the CAB disappeared. Maternal snail mRNA, which encodes a transcription factor, was co-localized with the antigen for the H3S28p antibody. Furthermore, we found a novel PGC-specific subcellular structure that we call the germ body (GB). This study thus highlights the conserved and non-conserved features of germline development between ascidians and larvaceans. The rapid development and short life cycle (five days) of O. dioica would open the way to genetically analyze germ cell development in the future.
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Affiliation(s)
- Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
| | - Masaki Matsuo
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Shohei Konishi
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Nobuhiko Ohno
- Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan; Division of Histology and Cell Biology, Department of Anatomy, Jichi Medical University, Shimotsuke, Tochigi, 329-0498, Japan
| | - Lucia Manni
- Dipartimento di Biologia, Università degli Studi di Padova, via U. Bassi 58/B, I-35121, Padova, Italy
| | - Takeshi A Onuma
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
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7
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Porras-Gómez TJ, Villagrán-SantaCruz M, Moreno-Mendoza N. Biology of primordial germ cells in vertebrates with emphasis in urodeles amphibians. Mol Reprod Dev 2021; 88:773-792. [PMID: 34532913 DOI: 10.1002/mrd.23533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 08/23/2021] [Accepted: 08/26/2021] [Indexed: 11/08/2022]
Abstract
Primordial germ cells (PGCs) are highly specialized cells that play a relevant role in the maintenance and evolution of the species, since they create new combinations of genetic information between the organisms. Amphibians are a class of amniote vertebrates that are divided into three subclasses, the anurans (frogs and toads), the urodeles (salamanders and newts), and the gymnophiones (caecilians). The study of PGCs in amphibians has been addressed in more detail in anurans while little is known about the biology of this cell lineage in urodeles. Studies in some urodeles species have suggested that PGCs are of mesodermal origin, specifying in the lateral plate mesoderm at the late gastrula stage. With classical experiments it shown that, there is an induction of mesoderm, therefore most likely urodeles PGCs develop from unspecialized mesodermal tissue that responds to extracellular signals. However, some fundamental biological processes of PGCs such as the analysis of their specification, arrival, and colonization to the gonads, and their maintenance and differentiation into mature and fertile gametes remain to be elucidated. Therefore, knowledge about the biology of PGCs is of great importance to ensure the perpetuation of urodeles amphibians, as some species are in danger of becoming extinct.
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Affiliation(s)
- Tania J Porras-Gómez
- Laboratorio de Biología Tisular y Reproductora, Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Maricela Villagrán-SantaCruz
- Laboratorio de Biología Tisular y Reproductora, Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Norma Moreno-Mendoza
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
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8
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Oda-Ishii I, Yu D, Satou Y. Two distinct motifs for Zic-r.a drive specific gene expression in two cell lineages. Development 2021; 148:269043. [PMID: 34100063 DOI: 10.1242/dev.199538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/26/2021] [Indexed: 11/20/2022]
Abstract
Zic-r.a, a maternal transcription factor, specifies posterior fate in ascidian embryos. However, its direct target, Tbx6-r.b, does not contain typical Zic-r.a-binding sites in its regulatory region. Using an in vitro selection assay, we found that Zic-r.a binds to sites dissimilar to the canonical motif, by which it activates Tbx6-r.b in a sub-lineage of muscle cells. These sites with non-canonical motifs have weak affinity for Zic-r.a; therefore, it activates Tbx6-r.b only in cells expressing Zic-r.a abundantly. Meanwhile, we found that Zic-r.a expressed zygotically in late embryos activates neural genes through canonical sites. Because different zinc-finger domains of Zic-r.a are important for driving reporters with canonical and non-canonical sites, it is likely that the non-canonical motif is not a divergent version of the canonical motif. In other words, our data indicate that the non-canonical motif represents a motif distinct from the canonical motif. Thus, Zic-r.a recognizes two distinct motifs to activate two sets of genes at two timepoints in development. This article has an associated 'The people behind the papers' interview.
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Affiliation(s)
- Izumi Oda-Ishii
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Deli Yu
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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9
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Tokuoka M, Maeda K, Kobayashi K, Mochizuki A, Satou Y. The gene regulatory system for specifying germ layers in early embryos of the simple chordate. SCIENCE ADVANCES 2021; 7:7/24/eabf8210. [PMID: 34108211 PMCID: PMC8189585 DOI: 10.1126/sciadv.abf8210] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 04/23/2021] [Indexed: 06/12/2023]
Abstract
In animal embryos, gene regulatory networks control the dynamics of gene expression in cells and coordinate such dynamics among cells. In ascidian embryos, gene expression dynamics have been dissected at the single-cell resolution. Here, we revealed mathematical functions that represent the regulatory logics of all regulatory genes expressed at the 32-cell stage when the germ layers are largely specified. These functions collectively explain the entire mechanism by which gene expression dynamics are controlled coordinately in early embryos. We found that regulatory functions for genes expressed in each of the specific lineages contain a common core regulatory mechanism. Last, we showed that the expression of the regulatory genes became reproducible by calculation and controllable by experimental manipulations. Thus, these regulatory functions represent an architectural design for the germ layer specification of this chordate and provide a platform for simulations and experiments to understand the operating principles of gene regulatory networks.
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Affiliation(s)
- Miki Tokuoka
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Kazuki Maeda
- Faculty of Informatics, University of Fukuchiyama, 3370 Hori, Fukuchiyama, Kyoto 620-0886, Japan
| | - Kenji Kobayashi
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Atsushi Mochizuki
- Institute for Frontier Life and Medical Sciences, Kyoto University, Sakyo, Kyoto 606-8507, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
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10
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Zheng T, Nakamoto A, Kumano G. H3K27me3 suppresses sister-lineage somatic gene expression in late embryonic germline cells of the ascidian, Halocynthia roretzi. Dev Biol 2020; 460:200-214. [PMID: 31904374 DOI: 10.1016/j.ydbio.2019.12.017] [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: 08/20/2019] [Revised: 11/21/2019] [Accepted: 12/29/2019] [Indexed: 10/25/2022]
Abstract
Protection of the germline from somatic differentiation programs is crucial for germ cell development. In many animals, whose germline development relies on the maternally inherited germ plasm, such protection in particular at early stages of embryogenesis is achieved by maternally localized global transcriptional repressors, such as PIE-1 of Caenorhabditis elegans, Pgc of Drosophila melanogaster and Pem of ascidians. However, zygotic gene expression starts in later germline cells eventually and mechanisms by which somatic gene expression is selectively kept under repression in the transcriptionally active cells are poorly understood. By using the ascidian species Halocynthia roretzi, we found that H3K27me3, a repressive transcription-related chromatin mark, became enriched in germline cells starting at the 64-cell stage when Pem protein level and its contribution to transcriptional repression decrease. Interestingly, inhibition of H3K27me3 together with Pem knockdown resulted in ectopic expression in germline cells of muscle developmental genes Muscle actin (MA4) and Snail, and of Clone 22 (which is expressed in all somatic but not germline cells), but not of other tissue-specific genes such as the notochord gene Brachyury, the nerve cord marker ETR-1 and a heart precursor gene Mesp, at the 110-cell stage. Importantly, these ectopically expressed genes are normally expressed in the germline sister cells (B7.5), the last somatic lineage separated from the germline. Also, the ectopic expression of MA4 was dependent on a maternally localized muscle determinant Macho-1. Taken together, we propose that H3K27me3 may be responsible for selective transcriptional repression for somatic genes in later germline cells in Halocynthia embryos and that the preferential repression of germline sister-lineage genes may be related to the mechanism of germline segregation in ascidian embryos, where the germline is segregated progressively by successive asymmetric cell divisions during cell cleavage stages. Together with findings from C. elegans and D. melanogaster, our data for this urochordate animal support the proposal for a mechanism, conserved widely throughout the animal kingdom, where germline transcriptional repression is mediated initially by maternally localized factors and subsequently by a chromatin-based mechanism.
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Affiliation(s)
- Tao Zheng
- Asamushi Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Japan.
| | - Ayaki Nakamoto
- Asamushi Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Japan
| | - Gaku Kumano
- Asamushi Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Japan
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11
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Ilsley GR, Suyama R, Noda T, Satoh N, Luscombe NM. Finding cell-specific expression patterns in the early Ciona embryo with single-cell RNA-seq. Sci Rep 2020; 10:4961. [PMID: 32188910 PMCID: PMC7080732 DOI: 10.1038/s41598-020-61591-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 02/24/2020] [Indexed: 11/09/2022] Open
Abstract
Single-cell RNA-seq has been established as a reliable and accessible technique enabling new types of analyses, such as identifying cell types and studying spatial and temporal gene expression variation and change at single-cell resolution. Recently, single-cell RNA-seq has been applied to developing embryos, which offers great potential for finding and characterising genes controlling the course of development along with their expression patterns. In this study, we applied single-cell RNA-seq to the 16-cell stage of the Ciona embryo, a marine chordate and performed a computational search for cell-specific gene expression patterns. We recovered many known expression patterns from our single-cell RNA-seq data and despite extensive previous screens, we succeeded in finding new cell-specific patterns, which we validated by in situ and single-cell qPCR.
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Affiliation(s)
- Garth R Ilsley
- Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan.,European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SD, United Kingdom
| | - Ritsuko Suyama
- Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan.,Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Takeshi Noda
- Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan.,Shinshu University, Matsumoto, Nagano, 390-8621, Japan
| | - Nori Satoh
- Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Nicholas M Luscombe
- Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan. .,The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK. .,UCL Genetics Institute, University College London, Gower Street, London, WC1E 6BT, UK.
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12
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Satou Y. A gene regulatory network for cell fate specification in Ciona embryos. Curr Top Dev Biol 2020; 139:1-33. [DOI: 10.1016/bs.ctdb.2020.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Yu D, Oda-Ishii I, Kubo A, Satou Y. The regulatory pathway from genes directly activated by maternal factors to muscle structural genes in ascidian embryos. Development 2019; 146:dev.173104. [PMID: 30674480 DOI: 10.1242/dev.173104] [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: 10/22/2018] [Accepted: 01/14/2019] [Indexed: 10/27/2022]
Abstract
Striated muscle cells in the tail of ascidian tadpole larvae differentiate cell-autonomously. Although several key regulatory factors have been identified, the genetic regulatory pathway is not fully understood; comprehensive understanding of the regulatory pathway is essential for accurate modeling in order to deduce principles for gene regulatory network dynamics, and for comparative analysis on how ascidians have evolved the cell-autonomous gene regulatory mechanism. Here, we reveal regulatory interactions among three key regulatory factors, Zic-r.b, Tbx6-r.b and Mrf, and elucidate the mechanism by which these factors activate muscle structural genes. We reveal a cross-regulatory circuit among these regulatory factors, which maintains the expression of Tbx6-r.b and Mrf during gastrulation. Although these two factors combinatorially activate muscle structural genes in late-stage embryos, muscle structural genes are activated mainly by Tbx6-r.b before gastrulation. Time points when expression of muscle structural genes become first detectable are strongly correlated with the degree of Tbx6-r.b occupancy. Thus, the genetic pathway, starting with Tbx6-r.b and Zic-r.b, which are activated by maternal factors, and ending with expression of muscle structural genes, has been revealed.
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Affiliation(s)
- Deli Yu
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Izumi Oda-Ishii
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Atsushi Kubo
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
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14
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Massive cytoplasmic transport and microtubule organization in fertilized chordate eggs. Dev Biol 2018; 448:154-160. [PMID: 30521810 DOI: 10.1016/j.ydbio.2018.11.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 11/24/2018] [Accepted: 11/30/2018] [Indexed: 01/13/2023]
Abstract
Eggs have developed their own strategies for early development. Amphibian, teleost fish, and ascidian eggs show cortical rotation and an accompanying structure, a cortical parallel microtubule (MT) array, during the one-cell embryonic stage. Cortical rotation is thought to relocate maternal deposits to a certain compartment of the egg and to polarize the embryo. The common features and differences among chordate eggs as well as localized maternal proteins and mRNAs that are related to the organization of MT structures are described in this review. Furthermore, recent studies report progress in elucidating the molecular nature and functions of the noncentrosomal MT organizing center (ncMTOC). The parallel array of MT bundles is presumably organized by ncMTOCs; therefore, the mechanism of ncMTOC control is likely inevitable for these species. Thus, the molecules related to the ncMTOC provide clues for understanding the mechanisms of early developmental systems, which ultimately determine the embryonic axis.
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15
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Initiation of the zygotic genetic program in the ascidian embryo. Semin Cell Dev Biol 2018; 84:111-117. [DOI: 10.1016/j.semcdb.2018.02.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 02/08/2018] [Accepted: 02/08/2018] [Indexed: 12/26/2022]
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16
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Abstract
Ascidians are tunicates, which constitute the sister group of vertebrates. The ascidian genome contains two Zic genes, called Zic-r.a (also called Macho-1) and Zic-r.b (ZicL). The latter is a multi-copy gene, and the precise copy number has not yet been determined. Zic-r.a is maternally expressed, and soon after fertilization Zic-r.a mRNA is localized in the posterior pole of the zygote. Zic-r.a protein is translated there and is involved in specification of posterior fate; in particular it is important for specification of muscle fate. Zic-r.a is also expressed zygotically in neural cells of the tailbud stage. On the other hand, Zic-r.b is first expressed in marginal cells of the vegetal hemisphere of 32-cell embryos and then in neural cells that contribute to the central nervous system during gastrulation. Zic-r.b is required first for specification of mesodermal tissues and then for specification of the central nervous system. Their upstream and downstream genetic pathways have been studied extensively by functional assays, which include gene knockdown and chromatin immunoprecipitation assays. Thus, ascidian Zic genes play central roles in specification of mesodermal and neural fates.
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Affiliation(s)
- Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan.
| | - Kaoru S Imai
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
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17
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Tokuoka M, Kobayashi K, Satou Y. Distinct regulation of Snail in two muscle lineages of the ascidian embryo achieves temporal coordination of muscle development. Development 2018; 145:dev.163915. [PMID: 29764858 DOI: 10.1242/dev.163915] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Accepted: 05/03/2018] [Indexed: 01/29/2023]
Abstract
The transcriptional repressor Snail is required for proper differentiation of the tail muscle of ascidian tadpole larvae. Two muscle lineages (B5.1 and B6.4) contribute to the anterior tail muscle cells, and are consecutively separated from a transcriptionally quiescent germ cell lineage at the 16- and 32-cell stages. Concomitantly, cells of these lineages begin to express Tbx6.b (Tbx6-r.b) at the 16- and 32-cell stages, respectively. Meanwhile, Snail expression begins in these two lineages simultaneously at the 32-cell stage. Here, we show that Snail expression is regulated differently between these two lineages. In the B5.1 lineage, Snail was activated through Tbx6.b, which is activated by maternal factors, including Zic-r.a. In the B6.4 lineage, the MAPK pathway was cell-autonomously activated by a constitutively active form of Raf, enabling Zic-r.a to activate Snail independently of Tbx6.b As a result, Snail begins to be expressed at the 32-cell stage simultaneously in these two lineages. Such shortcuts might be required for coordinating developmental programs in embryos in which cells become separated progressively from stem cells, including germline cells.
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Affiliation(s)
- Miki Tokuoka
- Department of Zoology, Graduate School of Science, Kyoto University Sakyo, Kyoto, 606-8502, Japan
| | - Kenji Kobayashi
- Department of Zoology, Graduate School of Science, Kyoto University Sakyo, Kyoto, 606-8502, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University Sakyo, Kyoto, 606-8502, Japan
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Control of Pem protein level by localized maternal factors for transcriptional regulation in the germline of the ascidian, Halocynthia roretzi. PLoS One 2018; 13:e0196500. [PMID: 29709000 PMCID: PMC5927453 DOI: 10.1371/journal.pone.0196500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 04/13/2018] [Indexed: 12/04/2022] Open
Abstract
Localized maternal mRNAs play important roles in embryogenesis, e.g. the establishment of embryonic axes and the developmental cell fate specification, in various animal species. In ascidians, a group of maternal mRNAs, called postplasmic/PEM RNAs, is localized to a subcellular structure, called the Centrosome-Attracting Body (CAB), which contains the ascidian germ plasm, and is inherited by the germline cells during embryogenesis. Posterior end mark (Pem), a postplasmic/PEM RNAs member, represses somatic gene expression in the germline during cleavage stages by inhibition of RNA polymerase II activity. However, the functions of other postplasmic/ PEM RNAs members in germline formation are largely unknown. In this study, we analyzed the functions of two postplasmic/PEM RNAs, Popk-1 and Zf-1, in transcriptional regulation in the germline cells. We show that Popk-1 contributes to transcriptional quiescence by controlling the size of the CAB and amount of Pem protein translated at the CAB. Our studies also indicated that zygotic expression of a germline gene starts around the onset of gastrulation and that the decrease of Pem protein is necessary and sufficient for the zygotic germline gene expression. Finally, further studies showed that the decrease of the Pem protein level is facilitated by Zf-1. Taken together, we propose that postplasmic/PEM RNAs such as Popk-1 and Zf-1 control the protein level of the transcriptional repressor Pem and regulate its transcriptional state in the ascidian germline.
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Treen N, Heist T, Wang W, Levine M. Depletion of Maternal Cyclin B3 Contributes to Zygotic Genome Activation in the Ciona Embryo. Curr Biol 2018; 28:1150-1156.e4. [PMID: 29576477 PMCID: PMC5996753 DOI: 10.1016/j.cub.2018.02.046] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/18/2017] [Accepted: 02/16/2018] [Indexed: 10/17/2022]
Abstract
Most animal embryos display a delay in the activation of zygotic transcription during early embryogenesis [1]. This process is thought to help coordinate rapid increases in cell number during early development [2]. The timing of zygotic genome activation (ZGA) during the maternal-to-zygotic transition (MZT) remains uncertain despite extensive efforts. We explore ZGA in the simple protovertebrate, Ciona intestinalis. Single-cell RNA sequencing (RNA-seq) assays identified Cyclin B3 (Ccnb3) as a putative mediator of ZGA. Maternal Ccnb3 transcripts rapidly diminish in abundance during the onset of zygotic transcription at the 8-cell and 16-cell stages. Disruption of Ccnb3 activity results in precocious activation of zygotic transcription, while overexpression abolishes normal activation. These observations suggest that the depletion of maternal Cyclin B3 products is a critical component of the MZT and ZGA. We discuss evidence that this mechanism might play a conserved role in the MZT of other metazoans, including mice and humans.
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Affiliation(s)
- Nicholas Treen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA.
| | - Tyler Heist
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Wei Wang
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Michael Levine
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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Oda-Ishii I, Abe T, Satou Y. Dynamics of two key maternal factors that initiate zygotic regulatory programs in ascidian embryos. Dev Biol 2018; 437:50-59. [PMID: 29550363 DOI: 10.1016/j.ydbio.2018.03.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 03/12/2018] [Accepted: 03/12/2018] [Indexed: 12/21/2022]
Abstract
In animal embryos, transcription is repressed for a definite period of time after fertilization. In the embryo of the ascidian, Ciona intestinalis (type A; or Ciona robusta), transcription of regulatory genes is repressed before the 8- or 16-cell stages. This initial transcriptional quiescence is important to enable the establishment of initial differential gene expression patterns along the animal-vegetal axis by maternal factors, because the third cell division separates the animal and vegetal hemispheres into distinct blastomeres. Indeed, maternal transcription factors directly activate zygotic gene expression by the 16-cell stage; Tcf7/β-catenin activates genes in the vegetal hemisphere, and Gata.a activates genes in the animal hemisphere. In the present study, we revealed the dynamics of Gata.a and β-catenin, and expression profiles of their target genes precisely. β-catenin began to translocate into the nuclei at the 16-cell stage, and thus expression of β-catenin targets began at the 16-cell stage. Although Gata.a is abundantly present before the 8-cell stage, transcription of Gata.a targets was repressed at and before the 4-cell stage, and their expression began at the 8-cell stage. Transcription of the β-catenin targets may be repressed by the same mechanism in early embryos, because β-catenin targets were not expressed in 4-cell embryos treated with a GSK inhibitor, in which β-catenin translocated to the nuclei. Thus, these two maternal factors have different dynamics, which establish the pre-pattern for zygotic genetic programs in 16-cell embryos.
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Affiliation(s)
- Izumi Oda-Ishii
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Tetsuya Abe
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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21
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Olsen LC, Kourtesis I, Busengdal H, Jensen MF, Hausen H, Chourrout D. Evidence for a centrosome-attracting body like structure in germ-soma segregation during early development, in the urochordate Oikopleura dioica. BMC DEVELOPMENTAL BIOLOGY 2018; 18:4. [PMID: 29486709 PMCID: PMC5830320 DOI: 10.1186/s12861-018-0165-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 02/16/2018] [Indexed: 11/27/2022]
Abstract
Background Germ cell formation has been investigated in sessile forms of tunicates. This process involves the release of a subset of maternal transcripts from the centrosome-attracting body (CAB) in the progenitor cells of the germ line. When germ-soma segregation is completed, CAB structures are missing from the newly formed primordial germ cells (PGCs). In free-swimming tunicates, knowledge about germ cell formation is lacking. In this investigation, comparative gene expression and electron microscopy studies were used to address germ cell formation in Oikopleura dioica (O. dioica). Results We found that the RNA localization pattern of pumilio (pum1) is similar to the pattern described for a subset of maternal transcripts marking the posterior end of ascidian embryos. Transcripts marking the posterior end are called postplasmic or posterior-end mark (PEM) transcripts. We found no localization of vasa (vas) transcripts to any sub-region within the germ-line precursor cells. Expression of vas4 was detected in the newly formed PGCs. Electron microscopy studies confirmed the presence of structures with similar morphology to CAB. In the same cytoplasmic compartment, we also identified pum1 transcripts and an epitope recognized by an antibody to histone H3 phosphorylated on serine 28. Conclusions Our findings support that a CAB-like structure participates in the segregation of maternal pum1 transcripts during germ-soma separation in O. dioica. Electronic supplementary material The online version of this article (10.1186/s12861-018-0165-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lisbeth Charlotte Olsen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway. .,Department of Molecular Biology, University of Bergen, Thormöhlensgt 55, 5008, Bergen, Norway. .,Department of Biological Sciences, University of Bergen, Thormöhlensgt 55, 5008, Bergen, Norway.
| | - Ioannis Kourtesis
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Henriette Busengdal
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Marit Flo Jensen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Daniel Chourrout
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
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22
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Dumollard R, Minc N, Salez G, Aicha SB, Bekkouche F, Hebras C, Besnardeau L, McDougall A. The invariant cleavage pattern displayed by ascidian embryos depends on spindle positioning along the cell's longest axis in the apical plane and relies on asynchronous cell divisions. eLife 2017; 6. [PMID: 28121291 PMCID: PMC5319837 DOI: 10.7554/elife.19290] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 01/24/2017] [Indexed: 12/24/2022] Open
Abstract
The ascidian embryo is an ideal system to investigate how cell position is determined during embryogenesis. Using 3D timelapse imaging and computational methods we analyzed the planar cell divisions in ascidian early embryos and found that spindles in every cell tend to align at metaphase in the long length of the apical surface except in cells undergoing unequal cleavage. Furthermore, the invariant and conserved cleavage pattern of ascidian embryos was found to consist in alternate planar cell divisions between ectoderm and endomesoderm. In order to test the importance of alternate cell divisions we manipulated zygotic transcription induced by β-catenin or downregulated wee1 activity, both of which abolish this cell cycle asynchrony. Crucially, abolishing cell cycle asynchrony consistently disrupted the spindle orienting mechanism underpinning the invariant cleavage pattern. Our results demonstrate how an evolutionary conserved cell cycle asynchrony maintains the invariant cleavage pattern driving morphogenesis of the ascidian blastula. DOI:http://dx.doi.org/10.7554/eLife.19290.001 The position of cells within an embryo early in development determines what type of cells they will become in the fully formed embryo. The embryos of ascidians, commonly known as sea squirts, are ideal for studying what influences cell positioning. These embryos consist of a small number of cells that divide according to an “invariant cleavage pattern”, which means that the positioning and timing of the cell divisions is identical between different individuals of the same species. The pattern of cell division is also largely the same across different ascidian species, which raises questions about how it is controlled. When a cell divides, a structure called the spindle forms inside it to distribute copies of the cell’s genetic material between the new cells. The orientation of the spindle determines the direction in which the cell will divide. Now, by combining 3D imaging of living ascidian embryos with computational modeling, Dumollard et al. show that the spindles in every equally dividing cell tend to all align in the long length of the cell’s “apical” surface. Such alignment allows the cells to be on the outside of the embryo and implements the ascidian invariant cleavage pattern. The cells in the embryo do not all divide at the same time. Indeed, the shape of the cells (and especially their apical surface) depends on two layers of cells in the embryo not dividing at the same time; instead, periods of cell division alternate between the layers. A network of genes in the embryo regulates the timing of these cell divisions and makes it possible for the cells to divide according to an invariant cleavage pattern. However, this network of genes is not the only control mechanism that shapes the early embryo. A structure found in egg cells (and hence produced by the embryo’s mother) causes cells at the rear of the embryo to divide unequally, and this influences the shape of all the cells in the embryo. Thus it appears that maternal mechanisms work alongside the embryo’s gene network to shape the early embryo. The next step will be to determine how physical forces – for example, from the cells pressing against each other – influence the position of the embryo’s cells. How do gene networks relay the biomechanical properties of the embryo to help it take shape? DOI:http://dx.doi.org/10.7554/eLife.19290.002
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Affiliation(s)
- Rémi Dumollard
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
| | - Nicolas Minc
- Institut Jacques Monod, UMR7592 CNRS, Paris, France
| | - Gregory Salez
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
| | - Sameh Ben Aicha
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
| | - Faisal Bekkouche
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
| | - Céline Hebras
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
| | - Lydia Besnardeau
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
| | - Alex McDougall
- Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV) UMR7009, Sorbonne Universités, Université Pierre-et-Marie-Curie, CNRS, Villefranche sur mer, France
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23
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Tokuhisa M, Muto M, Nishida H. Eccentric position of the germinal vesicle and cortical flow during oocyte maturation specify the animal-vegetal axis of ascidian embryos. Development 2017; 144:897-904. [DOI: 10.1242/dev.146282] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/11/2017] [Indexed: 01/08/2023]
Abstract
The animal-vegetal (A-V) axis is already set in unfertilized eggs. It plays crucial roles to coordinate germ-layer formation. However, how the A-V axis is set has not been well studied. In ascidians, unfertilized eggs are already polarized along the axis in terms of cellular components. The polarization occurs during oocyte maturation. Oocytes within the gonad have the germinal vesicle (GV) close to the future animal pole. When the GVs of full-grown oocytes were experimentally translocated to the opposite pole by centrifugal force, every aspect that designates A-V polarity was reversed in the eggs and embryos. This was confirmed by examining the cortical allocation of the meiotic spindle, position of the polar body emission, polarized distribution of mitochondria and postplasmic/PEM mRNA, direction of the cortical flow during oocyte maturation, cleavage pattern, and germ-layer formation during embryogenesis. Therefore, the eccentric position of the GV triggers subsequent polarizing events and establishes the A-V axis in eggs and embryos. We emphasize important roles of the cortical flow. This is the first report in which the A-V axis was experimentally and completely reversed in animal oocytes before fertilization.
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Affiliation(s)
- Masumi Tokuhisa
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Miyuki Muto
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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24
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Abstract
Asymmetric cell division during embryogenesis contributes to cell diversity by generating daughter cells that adopt distinct developmental fates. In this chapter, we summarize current knowledge of three examples of asymmetric cell division occurring in ascidian early embryos: (1) Three successive cell divisions that are asymmetric in terms of cell fate and unequal in cell size in the germline lineage at the embryo posterior pole. A subcellular structure, the centrosome-attracting body (CAB), and maternal PEM mRNAs localized within it control both the positioning of the cell division planes and segregation of the germ cell fates. (2) Asymmetric cell divisions involving endoderm and mesoderm germ layer separation. Asymmetric partitioning of zygotically expressed mRNA for Not, a homeodomain transcription factor, promotes the mesoderm fate and suppresses the endoderm fate. This asymmetric partitioning is mediated by transient nuclear migration toward the mesodermal pole of the mother cell, where the mRNA is delivered. In this case, there is no special regulation of cleavage plane orientation. (3) Asymmetric cell divisions in the marginal region of the vegetal hemisphere. The directed extracellular FGF and ephrin signals polarize the mother cells, inducing distinct fates in a pair of daughter cells (nerve versus notochord and mesenchyme versus muscle). The directions of cell division are regulated and oriented but independently of FGF and ephrin signaling. In these examples, polarization of the mother cells is facilitated by localized maternal factors, by delivery of transcripts from the nucleus to one pole of each cell, and by directed extracellular signals. Two cellular processes-asymmetric fate allocation and orientation of the cell division plane-are coupled by a single factor in the first example, but these processes are regulated independently in the third example. Thus, various modes of asymmetric cell division operate even at the early developmental stages in this single type of organism.
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Affiliation(s)
- Takefumi Negishi
- Division of Morphogenesis, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi, 444-8585, Japan
| | - Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-Cho, Toyonaka, Osaka, 560-0043, Japan.
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Mechanisms of Vertebrate Germ Cell Determination. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:383-440. [PMID: 27975276 DOI: 10.1007/978-3-319-46095-6_8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Two unique characteristics of the germ line are the ability to persist from generation to generation and to retain full developmental potential while differentiating into gametes. How the germ line is specified that allows it to retain these characteristics within the context of a developing embryo remains unknown and is one focus of current research. Germ cell specification proceeds through one of two basic mechanisms: cell autonomous or inductive. Here, we discuss how germ plasm driven germ cell specification (cell autonomous) occurs in both zebrafish and the frog Xenopus. We describe the segregation of germ cells during embryonic development of solitary and colonial ascidians to provide an evolutionary context to both mechanisms. We conclude with a discussion of the inductive mechanism as exemplified by both the mouse and axolotl model systems. Regardless of mechanism, several general themes can be recognized including the essential role of repression and posttranscriptional regulation of gene expression.
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26
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Hudson C, Sirour C, Yasuo H. Co-expression of Foxa.a, Foxd and Fgf9/16/20 defines a transient mesendoderm regulatory state in ascidian embryos. eLife 2016; 5. [PMID: 27351101 PMCID: PMC4945153 DOI: 10.7554/elife.14692] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/24/2016] [Indexed: 12/12/2022] Open
Abstract
In many bilaterian embryos, nuclear β-catenin (nβ-catenin) promotes mesendoderm over ectoderm lineages. Although this is likely to represent an evolutionary ancient developmental process, the regulatory architecture of nβ-catenin-induced mesendoderm remains elusive in the majority of animals. Here, we show that, in ascidian embryos, three nβ-catenin transcriptional targets, Foxa.a, Foxd and Fgf9/16/20, are each required for the correct initiation of both the mesoderm and endoderm gene regulatory networks. Conversely, these three factors are sufficient, in combination, to produce a mesendoderm ground state that can be further programmed into mesoderm or endoderm lineages. Importantly, we show that the combinatorial activity of these three factors is sufficient to reprogramme developing ectoderm cells to mesendoderm. We conclude that in ascidian embryos, the transient mesendoderm regulatory state is defined by co-expression of Foxa.a, Foxd and Fgf9/16/20. DOI:http://dx.doi.org/10.7554/eLife.14692.001
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Affiliation(s)
- Clare Hudson
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Villefranche-sur-Mer, France
| | - Cathy Sirour
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Villefranche-sur-Mer, France
| | - Hitoyoshi Yasuo
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Villefranche-sur-Mer, France
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27
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Oda-Ishii I, Kubo A, Kari W, Suzuki N, Rothbächer U, Satou Y. A Maternal System Initiating the Zygotic Developmental Program through Combinatorial Repression in the Ascidian Embryo. PLoS Genet 2016; 12:e1006045. [PMID: 27152625 PMCID: PMC4859511 DOI: 10.1371/journal.pgen.1006045] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 04/20/2016] [Indexed: 01/28/2023] Open
Abstract
Maternal factors initiate the zygotic developmental program in animal embryos. In embryos of the chordate, Ciona intestinalis, three maternal factors—Gata.a, β-catenin, and Zic-r.a—are required to establish three domains of gene expression at the 16-cell stage; the animal hemisphere, vegetal hemisphere, and posterior vegetal domains. Here, we show how the maternal factors establish these domains. First, only β-catenin and its effector transcription factor, Tcf7, are required to establish the vegetal hemisphere domain. Second, genes specifically expressed in the posterior vegetal domain have additional repressive cis-elements that antagonize the activity of β-catenin/Tcf7. This antagonizing activity is suppressed by Zic-r.a, which is specifically localized in the posterior vegetal domain and binds to DNA indirectly through the interaction with Tcf7. Third, Gata.a directs specific gene expression in the animal hemisphere domain, because β-catenin/Tcf7 weakens the Gata.a-binding activity for target sites through a physical interaction in the vegetal cells. Thus, repressive regulation through protein-protein interactions among the maternal transcription factors is essential to establish the first distinct domains of gene expression in the chordate embryo. During animal development, transcription factors and signaling molecules transcriptionally regulate one another and constitute a gene regulatory network. This network is evoked by maternally provided factors. Many maternal factors are localized and thereby activate a set of genes in a specific region. In embryos of the chordate, Ciona intestinalis, three maternal factors with localized activities are known. The present study demonstrated that these localized maternal factors interact with one another through a fourth non-localized transcription factor, Tcf7, and negatively regulate one another. These repressive interactions are essential to establish the first distinct domains of gene expression and evoke the gene regulatory network properly. The findings indicate that not only activating target genes but also repressing activities of other transcription factors through protein-protein interactions are important to properly initiate the zygotic program. Intriguingly, in one repressive interaction, a transcription factor loses its binding activity for target sites through an interaction with another transcription factor. Thus, this study provides a description of the entire system in which maternal factors initiate the zygotic developmental program of the Ciona embryo.
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Affiliation(s)
- Izumi Oda-Ishii
- Department of Zoology, Graduate School of Science, Kyoto University, Kita-Shirakawa Oiwake-cho, Sakyo, Kyoto, Japan
| | - Atsushi Kubo
- Department of Zoology, Graduate School of Science, Kyoto University, Kita-Shirakawa Oiwake-cho, Sakyo, Kyoto, Japan
| | - Willi Kari
- Department of Evolution and Developmental Biology, Zoological Institute, University Innsbruck, Innsbruck, Austria
| | - Nobuhiro Suzuki
- Department of Zoology, Graduate School of Science, Kyoto University, Kita-Shirakawa Oiwake-cho, Sakyo, Kyoto, Japan
| | - Ute Rothbächer
- Department of Evolution and Developmental Biology, Zoological Institute, University Innsbruck, Innsbruck, Austria
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Kita-Shirakawa Oiwake-cho, Sakyo, Kyoto, Japan
- * E-mail:
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Matsubara S, Kawada T, Sakai T, Aoyama M, Osugi T, Shiraishi A, Satake H. The significance of Ciona intestinalis as a stem organism in integrative studies of functional evolution of the chordate endocrine, neuroendocrine, and nervous systems. Gen Comp Endocrinol 2016; 227:101-8. [PMID: 26031189 DOI: 10.1016/j.ygcen.2015.05.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 05/13/2015] [Accepted: 05/16/2015] [Indexed: 11/19/2022]
Abstract
Ascidians are the closest phylogenetic neighbors to vertebrates and are believed to conserve the evolutionary origin in chordates of the endocrine, neuroendocrine, and nervous systems involving neuropeptides and peptide hormones. Ciona intestinalis harbors various homologs or prototypes of vertebrate neuropeptides and peptide hormones including gonadotropin-releasing hormones (GnRHs), tachykinins (TKs), and calcitonin, as well as Ciona-specific neuropeptides such as Ciona vasopressin, LF, and YFV/L peptides. Moreover, molecular and functional studies on Ciona tachykinin (Ci-TK) have revealed the novel molecular mechanism of inducing oocyte growth via up-regulation of vitellogenesis-associated protease activity, which is expected to be conserved in vertebrates. Furthermore, a series of studies on Ciona GnRH receptor paralogs have verified the species-specific regulation of GnRHergic signaling including unique signaling control via heterodimerization among multiple GnRH receptors. These findings confirm the remarkable significance of ascidians in investigations of the evolutionary processes of the peptidergic systems in chordates, leading to the promising advance in the research on Ciona peptides in the next stage based on the recent development of emerging technologies including genome-editing techniques, peptidomics-based multi-color staining, machine-learning prediction, and next-generation sequencing. These technologies and bioinformatic integration of the resultant "multi-omics" data will provide unprecedented insights into the comprehensive understanding of molecular and functional regulatory mechanisms of the Ciona peptides, and will eventually enable the exploration of both conserved and diversified endocrine, neuroendocrine, and nervous systems in the evolutionary lineage of chordates.
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Affiliation(s)
- Shin Matsubara
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan
| | - Tsuyoshi Kawada
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan
| | - Tsubasa Sakai
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan
| | - Masato Aoyama
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Kitauoyahigashi-machi, Nara 630-8506, Japan
| | - Tomohiro Osugi
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan
| | - Akira Shiraishi
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan
| | - Honoo Satake
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan.
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Abstract
Germ cells are the special cells in the body that undergo meiosis to generate gametes and subsequently entire new organisms after fertilization, a process that continues generation after generation. Recent studies have expanded our understanding of the factors and mechanisms that specify germ cell fate, including the partitioning of maternally supplied 'germ plasm', inheritance of epigenetic memory and expression of transcription factors crucial for primordial germ cell (PGC) development. Even after PGCs are specified, germline fate is labile and thus requires protective mechanisms, such as global transcriptional repression, chromatin state alteration and translation of only germline-appropriate transcripts. Findings from diverse species continue to provide insights into the shared and divergent needs of these special reproductive cells.
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Affiliation(s)
- Susan Strome
- Molecular, Cell &Developmental Biology, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - Dustin Updike
- Kathryn W. Davis Center for Regenerative Biology &Medicine, Mount Desert Island Biological Laboratory, Bar Harbor, Maine 04672, USA
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30
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Abstract
With few exceptions, all animals acquire the ability to produce eggs or sperm at some point in their life cycle. Despite this near-universal requirement for sexual reproduction, there exists an incredible diversity in germ line development. For example, animals exhibit a vast range of differences in the timing at which the germ line, which retains reproductive potential, separates from the soma, or terminally differentiated, nonreproductive cells. This separation may occur during embryonic development, after gastrulation, or even in adults, depending on the organism. The molecular mechanisms of germ line segregation are also highly diverse, and intimately intertwined with the overall transition from a fertilized egg to an embryo. The earliest embryonic stages of many species are largely controlled by maternally supplied factors. Later in development, patterning control shifts to the embryonic genome and, concomitantly with this transition, the maternally supplied factors are broadly degraded. This chapter attempts to integrate these processes--germ line segregation, and how the divergence of germ line and soma may utilize the egg to embryo transitions differently. In some embryos, this difference is subtle or maybe lacking altogether, whereas in other embryos, this difference in utilization may be a key step in the divergence of the two lineages. Here, we will focus our discussion on the echinoderms, and in particular the sea urchins, in which recent studies have provided mechanistic understanding in germ line determination. We propose that the germ line in sea urchins requires an acquisition of maternal factors from the egg and, when compared to other members of the taxon, this appears to be a derived mechanism. The acquisition is early--at the 32-cell stage--and involves active protection of maternal mRNAs, which are instead degraded in somatic cells with the maternal-to-embryonic transition. We collectively refer to this model as the Time Capsule method for germ line determination.
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Affiliation(s)
- S Zachary Swartz
- Department of Molecular and Cellular Biology, Brown University, Providence, Rhode Island, USA
| | - Gary M Wessel
- Department of Molecular and Cellular Biology, Brown University, Providence, Rhode Island, USA.
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31
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Abstract
Embryos of many animal models express germ line determinants that suppress transcription and mediate early germ line commitment, which occurs before the somatic cell lineages are established. However, not all animals segregate their germ line in this manner. The 'last cell standing' model describes primordial germ cell (PGC) development in axolotls, in which PGCs are maintained by an extracellular signalling niche, and germ line commitment occurs after gastrulation. Here, we propose that this 'stochastic' mode of PGC specification is conserved in vertebrates, including non-rodent mammals. We postulate that early germ line segregation liberates genetic regulatory networks for somatic development to evolve, and that it therefore emerged repeatedly in the animal kingdom in response to natural selection.
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Affiliation(s)
- Andrew D Johnson
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK
| | - Ramiro Alberio
- School of Biosciences, Sutton Bonington Campus, University of Nottingham, Loughborough LE12 5RD, UK
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32
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Kumano G. Evolution of germline segregation processes in animal development. Dev Growth Differ 2015; 57:324-32. [DOI: 10.1111/dgd.12211] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 03/05/2015] [Accepted: 03/05/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Gaku Kumano
- Asamushi Research Center for Marine Biology; Graduate School of Life Science; Tohoku University; 9 Sakamoto Asamushi Aomori 039-3501 Japan
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33
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Satou Y, Imai KS. Gene regulatory systems that control gene expression in the Ciona embryo. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2015; 91:33-51. [PMID: 25748582 PMCID: PMC4406867 DOI: 10.2183/pjab.91.33] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 11/05/2014] [Indexed: 06/04/2023]
Abstract
Transcriptional control of gene expression is one of the most important regulatory systems in animal development. Specific gene expression is basically determined by combinatorial regulation mediated by multiple sequence-specific transcription factors. The decoding of animal genomes has provided an opportunity for us to systematically examine gene regulatory networks consisting of successive layers of control of gene expression. It remains to be determined to what extent combinatorial regulation encoded in gene regulatory networks can explain spatial and temporal gene-expression patterns. The ascidian Ciona intestinalis is one of the animals in which the gene regulatory network has been most extensively studied. In this species, most specific gene expression patterns in the embryo can be explained by combinations of upstream regulatory genes encoding transcription factors and signaling molecules. Systematic scrutiny of gene expression patterns and regulatory interactions at the cellular resolution have revealed incomplete parts of the network elucidated so far, and have identified novel regulatory genes and novel regulatory mechanisms.
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Affiliation(s)
- Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University; CREST, JST, Saitama, Japan.
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34
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Nishida H, Stach T. Cell Lineages and Fate Maps in Tunicates: Conservation and Modification. Zoolog Sci 2014; 31:645-52. [DOI: 10.2108/zs140117] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Thomas Stach
- lnstitute of Biology, Comparative Zoology, Humboldt-Unlversity Berlin, 10115 Berlin, Germany
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35
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Wessel GM, Brayboy L, Fresques T, Gustafson EA, Oulhen N, Ramos I, Reich A, Swartz SZ, Yajima M, Zazueta V. The biology of the germ line in echinoderms. Mol Reprod Dev 2014; 81:679-711. [PMID: 23900765 PMCID: PMC4102677 DOI: 10.1002/mrd.22223] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 07/23/2013] [Indexed: 12/16/2022]
Abstract
The formation of the germ line in an embryo marks a fresh round of reproductive potential. The developmental stage and location within the embryo where the primordial germ cells (PGCs) form, however, differs markedly among species. In many animals, the germ line is formed by an inherited mechanism, in which molecules made and selectively partitioned within the oocyte drive the early development of cells that acquire this material to a germ-line fate. In contrast, the germ line of other animals is fated by an inductive mechanism that involves signaling between cells that directs this specialized fate. In this review, we explore the mechanisms of germ-line determination in echinoderms, an early-branching sister group to the chordates. One member of the phylum, sea urchins, appears to use an inherited mechanism of germ-line formation, whereas their relatives, the sea stars, appear to use an inductive mechanism. We first integrate the experimental results currently available for germ-line determination in the sea urchin, for which considerable new information is available, and then broaden the investigation to the lesser-known mechanisms in sea stars and other echinoderms. Even with this limited insight, it appears that sea stars, and perhaps the majority of the echinoderm taxon, rely on inductive mechanisms for germ-line fate determination. This enables a strongly contrasted picture for germ-line determination in this phylum, but one for which transitions between different modes of germ-line determination might now be experimentally addressed.
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Affiliation(s)
- Gary M. Wessel
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Lynae Brayboy
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Tara Fresques
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Eric A. Gustafson
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Nathalie Oulhen
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Isabela Ramos
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Adrian Reich
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - S. Zachary Swartz
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Mamiko Yajima
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Vanessa Zazueta
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
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36
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Swartz SZ, Reich AM, Oulhen N, Raz T, Milos PM, Campanale JP, Hamdoun A, Wessel GM. Deadenylase depletion protects inherited mRNAs in primordial germ cells. Development 2014; 141:3134-42. [PMID: 25100654 PMCID: PMC4197533 DOI: 10.1242/dev.110395] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/22/2014] [Indexed: 12/12/2022]
Abstract
A crucial event in animal development is the specification of primordial germ cells (PGCs), which become the stem cells that create sperm and eggs. How PGCs are created provides a valuable paradigm for understanding stem cells in general. We find that the PGCs of the sea urchin Strongylocentrotus purpuratus exhibit broad transcriptional repression, yet enrichment for a set of inherited mRNAs. Enrichment of several germline determinants in the PGCs requires the RNA-binding protein Nanos to target the transcript that encodes CNOT6, a deadenylase, for degradation in the PGCs, thereby creating a stable environment for RNA. Misexpression of CNOT6 in the PGCs results in their failure to retain Seawi transcripts and Vasa protein. Conversely, broad knockdown of CNOT6 expands the domain of Seawi RNA as well as exogenous reporters. Thus, Nanos-dependent spatially restricted CNOT6 differential expression is used to selectively localize germline RNAs to the PGCs. Our findings support a 'time capsule' model of germline determination, whereby the PGCs are insulated from differentiation by retaining the molecular characteristics of the totipotent egg and early embryo.
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Affiliation(s)
- S Zachary Swartz
- Department of Molecular, Cellular Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Adrian M Reich
- Department of Molecular, Cellular Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Nathalie Oulhen
- Department of Molecular, Cellular Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Tal Raz
- Helicos BioSciences Corporation, One Kendall Square, Building 700, Cambridge, MA 02139, USA
| | - Patrice M Milos
- Helicos BioSciences Corporation, One Kendall Square, Building 700, Cambridge, MA 02139, USA
| | - Joseph P Campanale
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, 8750 Biological Grade Road, La Jolla, CA 92037, USA
| | - Amro Hamdoun
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, 8750 Biological Grade Road, La Jolla, CA 92037, USA
| | - Gary M Wessel
- Department of Molecular, Cellular Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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37
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Chatfield J, O'Reilly MA, Bachvarova RF, Ferjentsik Z, Redwood C, Walmsley M, Patient R, Loose M, Johnson AD. Stochastic specification of primordial germ cells from mesoderm precursors in axolotl embryos. Development 2014; 141:2429-40. [PMID: 24917499 PMCID: PMC4050694 DOI: 10.1242/dev.105346] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 04/22/2014] [Indexed: 01/18/2023]
Abstract
A common feature of development in most vertebrate models is the early segregation of the germ line from the soma. For example, in Xenopus and zebrafish embryos primordial germ cells (PGCs) are specified by germ plasm that is inherited from the egg; in mice, Blimp1 expression in the epiblast mediates the commitment of cells to the germ line. How these disparate mechanisms of PGC specification evolved is unknown. Here, in order to identify the ancestral mechanism of PGC specification in vertebrates, we studied PGC specification in embryos from the axolotl (Mexican salamander), a model for the tetrapod ancestor. In the axolotl, PGCs develop within mesoderm, and classic studies have reported their induction from primitive ectoderm (animal cap). We used an axolotl animal cap system to demonstrate that signalling through FGF and BMP4 induces PGCs. The role of FGF was then confirmed in vivo. We also showed PGC induction by Brachyury, in the presence of BMP4. These conditions induced pluripotent mesodermal precursors that give rise to a variety of somatic cell types, in addition to PGCs. Irreversible restriction of the germ line did not occur until the mid-tailbud stage, days after the somatic germ layers are established. Before this, germline potential was maintained by MAP kinase signalling. We propose that this stochastic mechanism of PGC specification, from mesodermal precursors, is conserved in vertebrates.
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Affiliation(s)
- Jodie Chatfield
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
| | - Marie-Anne O'Reilly
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
| | - Rosemary F Bachvarova
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY 10065, USA
| | - Zoltan Ferjentsik
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
| | - Catherine Redwood
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
| | - Maggie Walmsley
- Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, Oxford University, Oxford OX3 9DS, UK
| | - Roger Patient
- Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, Oxford University, Oxford OX3 9DS, UK
| | - Mathew Loose
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
| | - Andrew D Johnson
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
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38
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Kumano G, Negoro N, Nishida H. Transcription factor Tbx6 plays a central role in fate determination between mesenchyme and muscle in embryos of the ascidian,Halocynthia roretzi. Dev Growth Differ 2014; 56:310-22. [DOI: 10.1111/dgd.12133] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 03/09/2014] [Accepted: 03/12/2014] [Indexed: 01/27/2023]
Affiliation(s)
- Gaku Kumano
- Asamushi Research Center for Marine Biology; Graduate School of Life Science; Tohoku University; 9 Sakamoto Asamushi Aomori 039-3501 Japan
| | - Nobue Negoro
- Department of Biological Sciences; Graduate School of Science; Osaka University; 1-1 Machikaneyama-cho Toyonaka Osaka 560-0043 Japan
| | - Hiroki Nishida
- Department of Biological Sciences; Graduate School of Science; Osaka University; 1-1 Machikaneyama-cho Toyonaka Osaka 560-0043 Japan
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39
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Yoshida K, Treen N, Hozumi A, Sakuma T, Yamamoto T, Sasakura Y. Germ cell mutations of the ascidianCiona intestinaliswith TALE nucleases. Genesis 2014; 52:431-9. [DOI: 10.1002/dvg.22770] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Keita Yoshida
- Shimoda Marine Research Center; University of Tsukuba; Shimoda Shizuoka 415-0025 Japan
| | - Nicholas Treen
- Shimoda Marine Research Center; University of Tsukuba; Shimoda Shizuoka 415-0025 Japan
| | - Akiko Hozumi
- Shimoda Marine Research Center; University of Tsukuba; Shimoda Shizuoka 415-0025 Japan
| | - Tetsushi Sakuma
- Department of Mathematical and Life Sciences, Graduate School of Science; Hiroshima University; 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima 739-8526 Japan
| | - Takashi Yamamoto
- Department of Mathematical and Life Sciences, Graduate School of Science; Hiroshima University; 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima 739-8526 Japan
| | - Yasunori Sasakura
- Shimoda Marine Research Center; University of Tsukuba; Shimoda Shizuoka 415-0025 Japan
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40
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Nonomura K, Yamaguchi Y, Hamachi M, Koike M, Uchiyama Y, Nakazato K, Mochizuki A, Sakaue-Sawano A, Miyawaki A, Yoshida H, Kuida K, Miura M. Local Apoptosis Modulates Early Mammalian Brain Development through the Elimination of Morphogen-Producing Cells. Dev Cell 2013; 27:621-34. [DOI: 10.1016/j.devcel.2013.11.015] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 11/05/2013] [Accepted: 11/20/2013] [Indexed: 02/07/2023]
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41
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Dumollard R, Hebras C, Besnardeau L, McDougall A. Beta-catenin patterns the cell cycle during maternal-to-zygotic transition in urochordate embryos. Dev Biol 2013; 384:331-42. [PMID: 24140189 DOI: 10.1016/j.ydbio.2013.10.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/18/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022]
Abstract
During the transition from maternal to zygotic control of development, cell cycle length varies in different lineages, and this is important for their fates and functions. The maternal to zygotic transition (MZT) in metazoan embryos involves a profound remodeling of the cell cycle: S phase length increases then G2 is introduced. Although β-catenin is the master regulator of endomesoderm patterning at MZT in all metazoans, the influence of maternal β-catenin on the cell cycle at MZT remains poorly understood. By studying urochordate embryogenesis we found that cell cycle remodeling during MZT begins with the formation of 3 mitotic domains at the 16-cell stage arising from differential S phase lengthening, when endomesoderm is specified. Then, at the 64-cell stage, a G2 phase is introduced in the endoderm lineage during its specification. Strikingly, these two phases of cell cycle remodeling are patterned by β-catenin-dependent transcription. Functional analysis revealed that, at the 16-cell stage, β-catenin speeds up S phase in the endomesoderm. In contrast, two cell cycles later at gastrulation, nuclear β-catenin induces endoderm fate and delays cell division. Such interphase lengthening in invaginating cells is known to be a requisite for gastrulation movements. Therefore, in basal chordates β-catenin has a dual role to specify germ layers and remodel the cell cycle.
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Affiliation(s)
- Rémi Dumollard
- UMR 7009, UPMC University, Paris 06, France; Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France.
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42
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Matsuoka T, Ikeda T, Fujimaki K, Satou Y. Transcriptome dynamics in early embryos of the ascidian, Ciona intestinalis. Dev Biol 2013; 384:375-85. [PMID: 24120375 DOI: 10.1016/j.ydbio.2013.10.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/20/2013] [Accepted: 10/03/2013] [Indexed: 11/25/2022]
Abstract
Maternally provided mRNAs and proteins direct early development and activate the zygotic genome. Using microarrays, we examined the dynamics of transcriptomes during the early development of a basal chordate, Ciona intestinalis. Microarray analysis of unfertilized eggs, as well as 8-, and 16- and 32-cell embryos revealed that nearly half of the genes encoded in the genome were expressed maternally, and that approximately only one-fourth of these genes were expressed at similar levels among eggs obtained from different individuals. Genes encoding proteins involved in protein phosphorylation were enriched in this latter group. More than 90% of maternal RNAs were not reduced before the 16-cell stage when the zygotic developmental program begins. Additionally we obtained gene expression profiles of individual blastomeres from the 8- and 16-cell embryos. On the basis of these profiles, we concluded that the posterior-most localization, which has been reported for over 20 different transcripts, is the only major localization pattern of maternal transcripts. Our data also showed that maternal factors establish only nine distinct patterns of zygotic gene expression at the 16-cell stage. Therefore, one of the main developmental functions of maternally supplied information is to establish these nine distinct expression patterns in the 16-cell embryo. The dynamics of transcriptomes in early-stage embryos provides a foundation for studying how maternal information starts the zygotic program.
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Affiliation(s)
- Terumi Matsuoka
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
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43
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Ishii H, Kunihiro S, Tanaka M, Hatano K, Nishikata T. Cytosolic subunits of ATP synthase are localized to the cortical endoplasmic reticulum-rich domain of the ascidian egg myoplasm. Dev Growth Differ 2013; 54:753-66. [PMID: 23067137 DOI: 10.1111/dgd.12003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Previously, we revealed that p58, one of the ascidian maternal factors, is identical to the alpha-subunit of F1-ATP synthase (ATPα), a protein complex of the inner mitochondrial membrane. In the current study, we used immunological probes for ascidian mitochondria components to show that the ascidian ATPα is ectopically localized to the cytosol. Virtually all mitochondrial components were localized to the mitochondria-rich myoplasm. However, in detail, ATP synthase subunits and the matrix proteins showed different localization patterns. At least at the crescent stage, transmission electron microscopy (TEM) distinguished the mitochondria-less, endoplasmic reticulum (ER)-rich cortical region and the mitochondria-rich internal region. ATPα was enriched in the cortical region and MnSOD was limited to the internal region. Using subcellular fractionation, although all of the mitochondria components were highly enriched in the mitochondria-enriched fraction, a considerable amount of ATPα and F1-ATP synthase beta-subunit (ATPβ) were recovered in the insoluble cytoplasmic fraction. Even under these conditions, F1-ATP synthase gamma-subunit (ATPγ) and F0-ATP synthase subunit b (ATPb) were not recovered in the insoluble cytoplasmic fraction. This result strongly supports the exomitochondrial localization of both ATPα and ATPβ. In addition, the detergent extraction of eggs supports the idea that these cytosolic ATP synthase subunits are associated with the egg cytoskeleton. These results suggest that the subunits of ATP synthase might play dual roles at different subcellular compartments during early development.
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Affiliation(s)
- Hirokazu Ishii
- Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, Kobe, Hyogo, 650-0047, Japan.
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44
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β-Catenin-Driven Binary Fate Specification Segregates Germ Layers in Ascidian Embryos. Curr Biol 2013; 23:491-5. [DOI: 10.1016/j.cub.2013.02.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 01/18/2013] [Accepted: 02/01/2013] [Indexed: 11/18/2022]
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Wang JT, Seydoux G. Germ cell specification. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 757:17-39. [PMID: 22872473 DOI: 10.1007/978-1-4614-4015-4_2] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The germline of Caenorhabditis elegans derives from a single founder cell, the germline blastomere P(4). P(4) is the product of four asymmetric cleavages that divide the zygote into distinct somatic and germline (P) lineages. P(4) inherits a specialized cytoplasm ("germ plasm") containing maternally encoded proteins and RNAs. The germ plasm has been hypothesized to specify germ cell fate, but the mechanisms involved remain unclear. Three processes stand out: (1) inhibition of mRNA transcription to prevent activation of somatic development, (2) translational regulation of the nanos homolog nos-2 and of other germ plasm mRNAs, and (3) establishment of a unique, partially repressive chromatin. Together, these processes ensure that the daughters of P(4), the primordial germ cells Z2 and Z3, gastrulate inside the embryo, associate with the somatic gonad, initiate the germline transcriptional program, and proliferate during larval development to generate ∼2,000 germ cells by adulthood.
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Affiliation(s)
- Jennifer T Wang
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
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46
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Brown FD, Swalla BJ. Evolution and development of budding by stem cells: Ascidian coloniality as a case study. Dev Biol 2012; 369:151-62. [DOI: 10.1016/j.ydbio.2012.05.038] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Revised: 05/27/2012] [Accepted: 05/28/2012] [Indexed: 01/15/2023]
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Chihara D, Nance J. An E-cadherin-mediated hitchhiking mechanism for C. elegans germ cell internalization during gastrulation. Development 2012; 139:2547-56. [PMID: 22675206 DOI: 10.1242/dev.079863] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Gastrulation movements place endodermal precursors, mesodermal precursors and primordial germ cells (PGCs) into the interior of the embryo. Somatic cell gastrulation movements are regulated by transcription factors that also control cell fate, coupling cell identity and position. By contrast, PGCs in many species are transcriptionally quiescent, suggesting that they might use alternative gastrulation strategies. Here, we show that C. elegans PGCs internalize by attaching to internal endodermal cells, which undergo morphogenetic movements that pull the PGCs into the embryo. We show that PGCs enrich HMR-1/E-cadherin at their surfaces to stick to endoderm. HMR-1 expression in PGCs is necessary and sufficient to ensure internalization, suggesting that HMR-1 can promote PGC-endoderm adhesion through a mechanism other than homotypic trans interactions between the two cell groups. Finally, we demonstrate that the hmr-1 3' untranslated region promotes increased HMR-1 translation in PGCs. Our findings reveal that quiescent PGCs employ a post-transcriptionally regulated hitchhiking mechanism to internalize during gastrulation, and demonstrate a morphogenetic role for the conserved association of PGCs with the endoderm.
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Affiliation(s)
- Daisuke Chihara
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY 10016, USA
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Makabe KW, Nishida H. Cytoplasmic localization and reorganization in ascidian eggs: role of postplasmic/PEM RNAs in axis formation and fate determination. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 1:501-18. [PMID: 23801532 DOI: 10.1002/wdev.54] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Localization of maternal molecules in eggs and embryos and cytoplasmic movements to relocalize them are fundamental for the orderly cellular and genetic processes during early embryogenesis. Ascidian embryos have been known as 'mosaic eggs' because of their autonomous differentiation abilities based on localized cell fate determinants. This review gives a historical overview of the concept of cytoplasmic localization, and then explains the key features such as ooplasmic movements and cell lineages that are essential to grasp the process of ascidian development mediated by localized determinant activities. These activities are partly executed by localized molecules named postplasmic/PEM RNAs, originating from approximately 50 genes, of which the muscle determinant, macho-1, is an example. The cortical domain containing these RNAs is relocalized to the posterior-vegetal region of the egg by cytoskeletal movements after fertilization, and plays crucial roles in axis formation and cell fate determination. The cortical domain contains endoplasmic reticulum and characteristic granules, and gives rise to a subcellular structure called the centrosome-attracting body (CAB), in which postplasmic/PEM RNAs are highly concentrated. The CAB is responsible for a series of unequal partitionings of the posterior-vegetal cytoplasmic domain and the postplasmic/PEM RNAs at the posterior pole during cleavage. Some components of this domain, which is rich in granules, are eventually inherited by prospective germline cells with particular postplasmic/PEM RNAs such as vasa. The postplasmic/PEM RNAs are classified into two groups according to their final cellular destinations and localization pathways. Localization of these RNAs is regulated by specific nucleotide sequences in the 3' untranslated regions (3'UTRs).
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Affiliation(s)
- Kazuhiro W Makabe
- Institute of Socio-Arts and Sciences, University of Tokushima, Tokushima, Japan
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Cell-Cycle Control in Oocytes and During Early Embryonic Cleavage Cycles in Ascidians. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 297:235-64. [DOI: 10.1016/b978-0-12-394308-8.00006-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Abstract
The study of cis-regulatory DNAs that control developmental gene expression is integral to the modeling of comprehensive genomic regulatory networks for embryogenesis. Ascidian embryos provide a unique opportunity for the analysis of cis-regulatory DNAs with cellular resolution in the context of a simple but typical chordate body plan. Here, we review landmark studies that have laid the foundations for the study of transcriptional enhancers, among other cis-regulatory DNAs, and their roles in ascidian development. The studies using ascidians of the Ciona genus have capitalized on a unique electroporation technique that permits the simultaneous transfection of hundreds of fertilized eggs, which develop rapidly and express transgenes with little mosaicism. Current studies using the ascidian embryo benefit from extensively annotated genomic resources to characterize transcript models in silico. The search for functional noncoding sequences can be guided by bioinformatic analyses combining evolutionary conservation, gene coexpression, and combinations of overrepresented short-sequence motifs. The power of the transient transfection assays has allowed thorough dissection of numerous cis-regulatory modules, which provided insights into the functional constraints that shape enhancer architecture and diversification. Future studies will benefit from pioneering stable transgenic lines and the analysis of chromatin states. Whole genome expression, functional and DNA binding data are being integrated into comprehensive genomic regulatory network models of early ascidian cell specification with a single-cell resolution that is unique among chordate model systems.
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