1
|
Wildner C, Mehta GD, Ball DA, Karpova TS, Koeppl H. Bayesian analysis dissects kinetic modulation during non-stationary gene expression. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.20.545522. [PMID: 37503023 PMCID: PMC10370195 DOI: 10.1101/2023.06.20.545522] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Labelling of nascent stem loops with fluorescent proteins has fostered the visualization of transcription in living cells. Quantitative analysis of recorded fluorescence traces can shed light on kinetic transcription parameters and regulatory mechanisms. However, existing methods typically focus on steady state dynamics. Here, we combine a stochastic process transcription model with a hierarchical Bayesian method to infer global as well locally shared parameters for groups of cells and recover unobserved quantities such as initiation times and polymerase loading of the gene. We apply our approach to the cyclic response of the yeast CUP1 locus to heavy metal stress. Within the previously described slow cycle of transcriptional activity on the scale of minutes, we discover fast time-modulated bursting on the scale of seconds. Model comparison suggests that slow oscillations of transcriptional output are regulated by the amplitude of the bursts. Several polymerases may initiate during a burst.
Collapse
Affiliation(s)
- Christian Wildner
- Centre for Synthetic Biology, Technische Universität Darmstadt, Darmstadt, 64283, Germany
| | - Gunjan D. Mehta
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana-502285, India
| | - David A. Ball
- National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Tatiana S. Karpova
- National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Heinz Koeppl
- Centre for Synthetic Biology, Technische Universität Darmstadt, Darmstadt, 64283, Germany
| |
Collapse
|
2
|
Canesini G, Galoppo GH, Tavalieri YE, Lazzarino GP, Stoker C, Luque EH, Ramos JG, Muñoz-de-Toro M. Disruption of the developmental programming of the gonad of the broad snouted caiman (Caiman latirostris) after in ovo exposure to atrazine. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:40132-40146. [PMID: 36607581 DOI: 10.1007/s11356-022-25104-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 12/28/2022] [Indexed: 06/17/2023]
Abstract
Environmental exposure to agrochemicals during early stages of development can induce subtle alterations that could permanently affect normal physiology. Previously, we reported that in ovo exposure to atrazine (ATZ) disrupts testicular histoarchitecture in postnatal caimans (Caiman latirostris). To assess whether such alterations are the result of disruption of gonadal developmental programming, this study aimed to evaluate the expression of histofunctional biomarkers (VASA, ER, PR, PCNA, and aromatase) and genes involved in gonadal development and differentiation (amh, sox-9, sf-1 and cyp19-a1) in the gonads of male and female caiman embryos and to assess the effect of ATZ exposure on these biomarkers and genes in the gonads of male embryos. Our results suggest that amh, aromatase and sox-9 play a role in sex determination and gonadal differentiation. In male caiman embryos, ATZ exposure increased aromatase expression and altered the temporal expression pattern of amh and sox-9 evidencing an ATZ-induced disruption of gonadal developmental programming. Since the effects of ATZ are consistent across all vertebrate classes, the ATZ-mediated disruptive effects here observed could be present in other vertebrate species.
Collapse
Affiliation(s)
- Guillermina Canesini
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
| | - Germán H Galoppo
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina.
| | - Yamil E Tavalieri
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
| | - Gisela P Lazzarino
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
| | - Cora Stoker
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
- Departamento de Bioquímica Clínica y Cuantitativa, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Enrique H Luque
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
| | - Jorge G Ramos
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
- Departamento de Bioquímica Clínica y Cuantitativa, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina
| | - Mónica Muñoz-de-Toro
- Instituto de Salud y Ambiente del Litoral (ISAL), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, Santa Fe 3000, Argentina
| |
Collapse
|
3
|
Fernandes G, Tran H, Andrieu M, Diaw Y, Perez Romero C, Fradin C, Coppey M, Walczak AM, Dostatni N. Synthetic reconstruction of the hunchback promoter specifies the role of Bicoid, Zelda and Hunchback in the dynamics of its transcription. eLife 2022; 11:74509. [PMID: 35363606 PMCID: PMC8975551 DOI: 10.7554/elife.74509] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 03/10/2022] [Indexed: 11/23/2022] Open
Abstract
For over 40 years, the Bicoid-hunchback (Bcd-hb) system in the fruit fly embryo has been used as a model to study how positional information in morphogen concentration gradients is robustly translated into step-like responses. A body of quantitative comparisons between theory and experiment have since questioned the initial paradigm that the sharp hb transcription pattern emerges solely from diffusive biochemical interactions between the Bicoid transcription factor and the gene promoter region. Several alternative mechanisms have been proposed, such as additional sources of positional information, positive feedback from Hb proteins or out-of-equilibrium transcription activation. By using the MS2-MCP RNA-tagging system and analysing in real time, the transcription dynamics of synthetic reporters for Bicoid and/or its two partners Zelda and Hunchback, we show that all the early hb expression pattern features and temporal dynamics are compatible with an equilibrium model with a short decay length Bicoid activity gradient as a sole source of positional information. Meanwhile, Bicoid’s partners speed-up the process by different means: Zelda lowers the Bicoid concentration threshold required for transcriptional activation while Hunchback reduces burstiness and increases the polymerase firing rate.
Collapse
Affiliation(s)
- Gonçalo Fernandes
- Institut Curie, Université PSL, Sorbonne Université, CNRS, Nuclear Dynamics, Paris, France
| | - Huy Tran
- Institut Curie, Université PSL, Sorbonne Université, CNRS, Nuclear Dynamics, Paris, France.,Laboratoire de Physique de l'École Normale Supérieure, CNRS, Université PSL, Sorbonne Université and Université de Paris, Paris, France
| | - Maxime Andrieu
- Institut Curie, Université PSL, Sorbonne Université, CNRS, Nuclear Dynamics, Paris, France
| | - Youssoupha Diaw
- Institut Curie, Université PSL, Sorbonne Université, CNRS, Nuclear Dynamics, Paris, France
| | - Carmina Perez Romero
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada
| | - Cécile Fradin
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada.,Department of Physics and Astronomy, McMaster University, Hamilton, Canada
| | - Mathieu Coppey
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico Chimie Curie, Paris, France
| | - Aleksandra M Walczak
- Laboratoire de Physique de l'École Normale Supérieure, CNRS, Université PSL, Sorbonne Université and Université de Paris, Paris, France
| | - Nathalie Dostatni
- Institut Curie, Université PSL, Sorbonne Université, CNRS, Nuclear Dynamics, Paris, France
| |
Collapse
|
4
|
Garbuzov FE, Gursky VV. Nonequilibrium model of short-range repression in gene transcription regulation. Phys Rev E 2021; 104:014407. [PMID: 34412298 DOI: 10.1103/physreve.104.014407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 06/24/2021] [Indexed: 11/07/2022]
Abstract
Transcription factors are proteins that regulate gene activity by activating or repressing gene transcription. A special class of transcriptional repressors operates via a short-range mechanism, making local DNA regions inaccessible to binding by activators, and thus providing an indirect repressive action on the target gene. This mechanism is commonly modeled assuming that repressors interact with DNA under thermodynamic equilibrium and neglecting some configurations of the gene regulatory region. We elaborate on a more general nonequilibrium model of short-range repression using the graph formalism for transitions between gene states, and we apply analytical calculations to compare it with the equilibrium model in terms of the repression strength and expression noise. In contrast to the equilibrium approach, the new model allows us to separate two basic mechanisms of short-range repression. The first mechanism is associated with the recruiting of factors that mediate chromatin condensation, and the second one concerns the blocking of factors that mediate chromatin loosening. The nonequilibrium model demonstrates better performance on previously published gene expression data obtained for transcription factors controlling Drosophila development, and furthermore it predicts that the first repression mechanism is the most favorable in this system. The presented approach can be scaled to larger gene networks and can be used to infer specific modes and parameters of transcriptional regulation from gene expression data.
Collapse
Affiliation(s)
- F E Garbuzov
- Ioffe Institute, 26 Polytekhnicheskaya, St. Petersburg 194021, Russia
| | - V V Gursky
- Ioffe Institute, 26 Polytekhnicheskaya, St. Petersburg 194021, Russia
| |
Collapse
|
5
|
Alamos S, Reimer A, Niyogi KK, Garcia HG. Quantitative imaging of RNA polymerase II activity in plants reveals the single-cell basis of tissue-wide transcriptional dynamics. NATURE PLANTS 2021; 7:1037-1049. [PMID: 34373604 PMCID: PMC8616715 DOI: 10.1038/s41477-021-00976-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 06/22/2021] [Indexed: 05/18/2023]
Abstract
The responses of plants to their environment are often dependent on the spatiotemporal dynamics of transcriptional regulation. While live-imaging tools have been used extensively to quantitatively capture rapid transcriptional dynamics in living animal cells, the lack of implementation of these technologies in plants has limited concomitant quantitative studies in this kingdom. Here, we applied the PP7 and MS2 RNA-labelling technologies for the quantitative imaging of RNA polymerase II activity dynamics in single cells of living plants as they respond to experimental treatments. Using this technology, we counted nascent RNA transcripts in real time in Nicotiana benthamiana (tobacco) and Arabidopsis thaliana. Examination of heat shock reporters revealed that plant tissues respond to external signals by modulating the proportion of cells that switch from an undetectable basal state to a high-transcription state, instead of modulating the rate of transcription across all cells in a graded fashion. This switch-like behaviour, combined with cell-to-cell variability in transcription rate, results in mRNA production variability spanning three orders of magnitude. We determined that cellular heterogeneity stems mainly from stochasticity intrinsic to individual alleles instead of variability in cellular composition. Together, our results demonstrate that it is now possible to quantitatively study the dynamics of transcriptional programs in single cells of living plants.
Collapse
Affiliation(s)
- Simon Alamos
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA
| | - Armando Reimer
- Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA
| | - Krishna K Niyogi
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, USA.
- Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA.
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Hernan G Garcia
- Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA.
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA.
- Department of Physics, University of California Berkeley, Berkeley, CA, USA.
- Institute for Quantitative Biosciences-QB3, University of California Berkeley, Berkeley, CA, USA.
| |
Collapse
|
6
|
Liu J, Hansen D, Eck E, Kim YJ, Turner M, Alamos S, Garcia HG. Real-time single-cell characterization of the eukaryotic transcription cycle reveals correlations between RNA initiation, elongation, and cleavage. PLoS Comput Biol 2021; 17:e1008999. [PMID: 34003867 PMCID: PMC8162642 DOI: 10.1371/journal.pcbi.1008999] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 05/28/2021] [Accepted: 04/23/2021] [Indexed: 12/23/2022] Open
Abstract
The eukaryotic transcription cycle consists of three main steps: initiation, elongation, and cleavage of the nascent RNA transcript. Although each of these steps can be regulated as well as coupled with each other, their in vivo dissection has remained challenging because available experimental readouts lack sufficient spatiotemporal resolution to separate the contributions from each of these steps. Here, we describe a novel application of Bayesian inference techniques to simultaneously infer the effective parameters of the transcription cycle in real time and at the single-cell level using a two-color MS2/PP7 reporter gene and the developing fruit fly embryo as a case study. Our method enables detailed investigations into cell-to-cell variability in transcription-cycle parameters as well as single-cell correlations between these parameters. These measurements, combined with theoretical modeling, suggest a substantial variability in the elongation rate of individual RNA polymerase molecules. We further illustrate the power of this technique by uncovering a novel mechanistic connection between RNA polymerase density and nascent RNA cleavage efficiency. Thus, our approach makes it possible to shed light on the regulatory mechanisms in play during each step of the transcription cycle in individual, living cells at high spatiotemporal resolution.
Collapse
Affiliation(s)
- Jonathan Liu
- Department of Physics, University of California at Berkeley, Berkeley, California, United States of America
| | - Donald Hansen
- Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, Heidelberg, Germany
| | - Elizabeth Eck
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Yang Joon Kim
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Meghan Turner
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Simon Alamos
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, California, United States of America
| | - Hernan G. Garcia
- Department of Physics, University of California at Berkeley, Berkeley, California, United States of America
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, United States of America
- Institute for Quantitative Biosciences-QB3, University of California at Berkeley, Berkeley, California, United States of America
| |
Collapse
|
7
|
Abstract
CRISPR-Cas9 genome editing has transformed biology by enabling site-specific genome modifications to be simply engineered. Here, we describe two CRISPR-Cas9 approaches to introduce MS2 stem-loop sequences into endogenous gene loci in Drosophila. This can facilitate live imaging of nascent transcription in Drosophila. For complete details on the use and execution of this protocol, please refer to Hoppe et al. (2020).
Collapse
Affiliation(s)
- Caroline Hoppe
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
| | - Hilary L. Ashe
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
| |
Collapse
|
8
|
Irizarry J, Stathopoulos A. Dynamic patterning by morphogens illuminated by cis-regulatory studies. Development 2021; 148:148/2/dev196113. [PMID: 33472851 DOI: 10.1242/dev.196113] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Morphogen concentration changes in space as well as over time during development. However, how these dynamics are interpreted by cells to specify fate is not well understood. Here, we focus on two morphogens: the maternal transcription factors Bicoid and Dorsal, which directly regulate target genes to pattern Drosophila embryos. The actions of these factors at enhancers has been thoroughly dissected and provides a rich platform for understanding direct input by morphogens and their changing roles over time. Importantly, Bicoid and Dorsal do not work alone; we also discuss additional inputs that work with morphogens to control spatiotemporal gene expression in embryos.
Collapse
Affiliation(s)
- Jihyun Irizarry
- California Institute of Technology, Division of Biology and Biological Engineering, 1200 East California Blvd., Pasadena, CA 91125, USA
| | - Angelike Stathopoulos
- California Institute of Technology, Division of Biology and Biological Engineering, 1200 East California Blvd., Pasadena, CA 91125, USA
| |
Collapse
|
9
|
Tran H, Walczak AM, Dostatni N. Constraints and limitations on the transcriptional response downstream of the Bicoid morphogen gradient. Curr Top Dev Biol 2020; 137:119-142. [PMID: 32143741 DOI: 10.1016/bs.ctdb.2019.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
The regulation of the hunchback promoter expression by the maternal Bicoid gradient has been studied as a model system in development for many years. Yet, at the level of quantitative agreement between data and theoretical models, even the first step of this regulation, transcription, continues to be challenging. This situation is slowly progressing, thanks to quantitative live-imaging techniques coupled to advanced statistical data analysis and modeling. Here, we outline the current state of our knowledge of this apparently "simple" step, highlighting the newly appreciated role of bursty transcription dynamics and its regulation.
Collapse
Affiliation(s)
- Huy Tran
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France; Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Laboratoire de Physique, Paris, France
| | - Aleksandra M Walczak
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Laboratoire de Physique, Paris, France.
| | - Nathalie Dostatni
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France.
| |
Collapse
|
10
|
Abstract
With its rapid development, ease of collection, and the presence of a unique layer of nuclei located close to the surface, the Drosophila syncytial embryo is ideally suited to study the establishment of gene expression patterns during development. Recent improvements in RNA labeling technologies and confocal microscopy allow for visualizing gene activation and quantifying transcriptional dynamics in living Drosophila embryos. Here we review the available tools for mRNA fluorescent labeling and detection in live embryos and precisely describe the overall procedure, from design to mounting and confocal imaging.
Collapse
Affiliation(s)
- Carola Fernandez
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, Cedex 5, France
| | - Mounia Lagha
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, Cedex 5, France.
| |
Collapse
|
11
|
Lucas T, Tran H, Perez Romero CA, Guillou A, Fradin C, Coppey M, Walczak AM, Dostatni N. 3 minutes to precisely measure morphogen concentration. PLoS Genet 2018; 14:e1007676. [PMID: 30365533 PMCID: PMC6221364 DOI: 10.1371/journal.pgen.1007676] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 11/07/2018] [Accepted: 09/05/2018] [Indexed: 11/18/2022] Open
Abstract
Morphogen gradients provide concentration-dependent positional information along polarity axes. Although the dynamics of the establishment of these gradients is well described, precision and noise in the downstream activation processes remain elusive. A simple paradigm to address these questions is the Bicoid morphogen gradient that elicits a rapid step-like transcriptional response in young fruit fly embryos. Focusing on the expression of the major Bicoid target, hunchback (hb), at the onset of zygotic transcription, we used the MS2-MCP approach which combines fluorescent labeling of nascent mRNA with live imaging at high spatial and temporal resolution. Removing 36 putative Zelda binding sites unexpectedly present in the original MS2 reporter, we show that the 750 bp of the hb promoter are sufficient to recapitulate endogenous expression at the onset of zygotic transcription. After each mitosis, in the anterior, expression is turned on to rapidly reach a plateau with all nuclei expressing the reporter. Consistent with a Bicoid dose-dependent activation process, the time period required to reach the plateau increases with the distance to the anterior pole. Despite the challenge imposed by frequent mitoses and high nuclei-to-nuclei variability in transcription kinetics, it only takes 3 minutes at each interphase for the MS2 reporter loci to distinguish subtle differences in Bicoid concentration and establish a steadily positioned and steep (Hill coefficient ~ 7) expression boundary. Modeling based on the cooperativity between the 6 known Bicoid binding sites in the hb promoter region, assuming rate limiting concentrations of the Bicoid transcription factor at the boundary, is able to capture the observed dynamics of pattern establishment but not the steepness of the boundary. This suggests that a simple model based only on the cooperative binding of Bicoid is not sufficient to describe the spatiotemporal dynamics of early hb expression.
Collapse
Affiliation(s)
- Tanguy Lucas
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
| | - Huy Tran
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Physique Théorique, Paris, France
| | - Carmina Angelica Perez Romero
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- Dept. of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Aurélien Guillou
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
| | - Cécile Fradin
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- Dept. of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Mathieu Coppey
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Physico Chimie, Paris, France
| | - Aleksandra M. Walczak
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Physique Théorique, Paris, France
| | - Nathalie Dostatni
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
| |
Collapse
|
12
|
Abstract
The activation of the zygotic genome and onset of transcription in blastula embryos is linked to changes in cell behavior and remodeling of the cell cycle and constitutes a transition from exclusive maternal to zygotic control of development. This step in development is referred to as mid-blastula transition and has served as a paradigm for the link between developmental program and cell behavior and morphology. Here, we discuss the mechanism and functional relationships between the zygotic genome activation and cell cycle control during mid-blastula transition with a focus on Drosophila embryos.
Collapse
Affiliation(s)
- Boyang Liu
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany
| | - Jörg Grosshans
- Institute for Developmental Biochemistry, Medical School, University of Göttingen, Justus-von-Liebig-Weg11, Göttingen 37077, Germany.
| |
Collapse
|
13
|
Perez-Romero CA, Tran H, Coppey M, Walczak AM, Fradin C, Dostatni N. Live Imaging of mRNA Transcription in Drosophila Embryos. Methods Mol Biol 2018; 1863:165-182. [PMID: 30324598 DOI: 10.1007/978-1-4939-8772-6_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Live imaging has been used in recent years for the understanding of dynamic processes in biology, such as embryo development. This was made possible by a combination of advancements in microscopy, leading to improved signal-to-noise ratios and better spatial and temporal resolutions, and by the development of new fluorescence markers, allowing for the quantification of protein expression and transcriptional dynamics in vivo. Here we describe a general protocol, which can be used in standard confocal microscopes to image early Drosophila melanogaster embryos, in order to learn about the transcriptional dynamics of a fluorescently labeled RNA.
Collapse
Affiliation(s)
- Carmina Angelica Perez-Romero
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- McMaster University, Hamilton, ON, Canada
| | - Huy Tran
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Physique Théorique, Paris, France
| | - Mathieu Coppey
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Physico Chimie, Paris, France
| | - Aleksandra M Walczak
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Physique Théorique, Paris, France
| | - Cécile Fradin
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- McMaster University, Hamilton, ON, Canada
| | - Nathalie Dostatni
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France.
| |
Collapse
|
14
|
Tran H, Perez-Romero CA, Ferraro T, Fradin C, Dostatni N, Coppey M, Walczak AM. LiveFly: A Toolbox for the Analysis of Transcription Dynamics in Live Drosophila Embryos. Methods Mol Biol 2018; 1863:183-195. [PMID: 30324599 DOI: 10.1007/978-1-4939-8772-6_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present the LiveFly toolbox for quantitative analysis of transcription dynamics in live Drosophila embryos. The toolbox allows users to process two-color 3D confocal movies acquired using nuclei-labeling and the fluorescent RNA-tagging system described in the previous chapter and export the nuclei's position as a function of time, their lineages and the intensity traces of the active loci. The toolbox, which is tailored for the context of Drosophila early development, is semiautomatic, and requires minimal user intervention. It also includes a tool to combine data from multiple movies and visualize several features of the intensity traces and the expression pattern.
Collapse
Affiliation(s)
- Huy Tran
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Laboratoire de Physique Théorique, Paris, France
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
| | - Carmina Angelica Perez-Romero
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- McMaster University, Hamilton, ON, Canada
| | - Teresa Ferraro
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Laboratoire de Physique Théorique, Paris, France
- Institut de Biologie Paris-Seine, Sorbonne Université, CNRS, Developmental Biology, Paris, France
| | - Cécile Fradin
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
- McMaster University, Hamilton, ON, Canada
| | - Nathalie Dostatni
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Nuclear Dynamics, Paris, France
| | - Mathieu Coppey
- Institut Curie, PSL Research University, CNRS, Sorbonne Université, Physico Chimie, Paris, France
| | - Aleksandra M Walczak
- Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Laboratoire de Physique Théorique, Paris, France.
| |
Collapse
|
15
|
Bentovim L, Harden TT, DePace AH. Transcriptional precision and accuracy in development: from measurements to models and mechanisms. Development 2017; 144:3855-3866. [PMID: 29089359 PMCID: PMC5702068 DOI: 10.1242/dev.146563] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
During development, genes are transcribed at specific times, locations and levels. In recent years, the emergence of quantitative tools has significantly advanced our ability to measure transcription with high spatiotemporal resolution in vivo. Here, we highlight recent studies that have used these tools to characterize transcription during development, and discuss the mechanisms that contribute to the precision and accuracy of the timing, location and level of transcription. We attempt to disentangle the discrepancies in how physicists and biologists use the term ‘precision' to facilitate interactions using a common language. We also highlight selected examples in which the coupling of mathematical modeling with experimental approaches has provided important mechanistic insights, and call for a more expansive use of mathematical modeling to exploit the wealth of quantitative data and advance our understanding of animal transcription. Summary: This Review highlights how high-resolution quantitative tools and theoretical models have formed our current view of the mechanisms determining precision and accuracy in the timing, location and level of transcription in the Drosophila embryo.
Collapse
Affiliation(s)
- Lital Bentovim
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Timothy T Harden
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| |
Collapse
|
16
|
Fradin C. On the importance of protein diffusion in biological systems: The example of the Bicoid morphogen gradient. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1676-1686. [PMID: 28919007 DOI: 10.1016/j.bbapap.2017.09.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 08/16/2017] [Accepted: 09/05/2017] [Indexed: 10/18/2022]
Abstract
Morphogens are proteins that form concentration gradients in embryos and developing tissues, where they act as postal codes, providing cells with positional information and allowing them to behave accordingly. Bicoid was the first discovered morphogen, and remains one of the most studied. It regulates segmentation in flies, forming a striking exponential gradient along the anterior-posterior axis of early Drosophila embryos, and activating the transcription of multiple target genes in a concentration-dependent manner. In this review, the work done by us and by others to characterize the mobility of Bicoid in D. melanogaster embryos is presented. The central role played by the diffusion of Bicoid in both the establishment of the gradient and the activation of target genes is discussed, and placed in the context of the need for these processes to be all at once rapid, precise and robust. The Bicoid system, and morphogen gradients in general, remain amongst the most amazing examples of the coexistence, often observed in living systems, of small-scale disorder and large-scale spatial order. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman.
Collapse
Affiliation(s)
- Cécile Fradin
- Dept. of Physics and Astronomy, McMaster University, 1280 Main St W., Hamilton, ON L8S 4M1, Canada
| |
Collapse
|
17
|
Holloway DM, Spirov AV. Transcriptional bursting in Drosophila development: Stochastic dynamics of eve stripe 2 expression. PLoS One 2017; 12:e0176228. [PMID: 28437444 PMCID: PMC5402966 DOI: 10.1371/journal.pone.0176228] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 04/08/2017] [Indexed: 01/17/2023] Open
Abstract
Anterior-posterior (AP) body segmentation of the fruit fly (Drosophila) is first seen in the 7-stripe spatial expression patterns of the pair-rule genes, which regulate downstream genes determining specific segment identities. Regulation of pair-rule expression has been extensively studied for the even-skipped (eve) gene. Recent live imaging, of a reporter for the 2ndeve stripe, has demonstrated the stochastic nature of this process, with ‘bursts’ in the number of RNA transcripts being made over time. We developed a stochastic model of the spatial and temporal expression of eve stripe 2 (binding by transcriptional activators (Bicoid and Hunchback proteins) and repressors (Giant and Krüppel proteins), transcriptional initiation and termination; with all rate parameters constrained by features of the experimental data) in order to analyze the noisy experimental time series and test hypotheses for how eve transcription is regulated. These include whether eve transcription is simply OFF or ON, with a single ON rate, or whether it proceeds by a more complex mechanism, with multiple ON rates. We find that both mechanisms can produce long (multi-minute) RNA bursts, but that the short-time (minute-to-minute) statistics of the data is indicative of eve being transcribed with at least two distinct ON rates, consistent with data on the joint activation of eve by Bicoid and Hunchback. We also predict distinct statistical signatures for cases in which eve is repressed (e.g. along the edges of the stripe) vs. cases in which activation is reduced (e.g. by mutagenesis of transcription factor binding sites). Fundamental developmental processes such as gene transcription are intrinsically noisy; our approach presents a new way to quantify and analyze time series data during developmental patterning in order to understand regulatory mechanisms and how they propagate noise and impact embryonic robustness.
Collapse
Affiliation(s)
- David M. Holloway
- Mathematics Department, British Columbia Institute of Technology, Burnaby, B.C., Canada
- Biology Department, University of Victoria, Victoria, B.C., Canada
- * E-mail:
| | - Alexander V. Spirov
- Computer Science, and Center of Excellence in Wireless and Information Technology, State University of New York, Stony Brook, New York, United States of America
- Sechenov Institute of Evolutionary Physiology and Biochemistry, St. Petersburg, Russia
| |
Collapse
|
18
|
Desponds J, Tran H, Ferraro T, Lucas T, Perez Romero C, Guillou A, Fradin C, Coppey M, Dostatni N, Walczak AM. Precision of Readout at the hunchback Gene: Analyzing Short Transcription Time Traces in Living Fly Embryos. PLoS Comput Biol 2016; 12:e1005256. [PMID: 27942043 PMCID: PMC5152799 DOI: 10.1371/journal.pcbi.1005256] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 11/19/2016] [Indexed: 12/21/2022] Open
Abstract
The simultaneous expression of the hunchback gene in the numerous nuclei of the developing fly embryo gives us a unique opportunity to study how transcription is regulated in living organisms. A recently developed MS2-MCP technique for imaging nascent messenger RNA in living Drosophila embryos allows us to quantify the dynamics of the developmental transcription process. The initial measurement of the morphogens by the hunchback promoter takes place during very short cell cycles, not only giving each nucleus little time for a precise readout, but also resulting in short time traces of transcription. Additionally, the relationship between the measured signal and the promoter state depends on the molecular design of the reporting probe. We develop an analysis approach based on tailor made autocorrelation functions that overcomes the short trace problems and quantifies the dynamics of transcription initiation. Based on live imaging data, we identify signatures of bursty transcription initiation from the hunchback promoter. We show that the precision of the expression of the hunchback gene to measure its position along the anterior-posterior axis is low both at the boundary and in the anterior even at cycle 13, suggesting additional post-transcriptional averaging mechanisms to provide the precision observed in fixed embryos. The fly embryo provides a natural laboratory to study the dynamics of transcription and its implications for the developing organism. Using live imaging experiments we investigate the nature of transcription regulation of the hunchback gene—the first to read out the maternal Bicoid gradient. While traditional time trace analysis methods based on OFF time distributions or autocorrelation functions fail for short signals, our tailored autocorrelation function overcomes these limitations revealing bursty dynamics that is reproducible between cell cycles and embryos. The inferred rates result in a lot of variability in the readout of nuclei sensing similar Bicoid concentrations, suggesting additional readout mechanisms than a one-to-one mapping of the input onto the output.
Collapse
Affiliation(s)
- Jonathan Desponds
- Ecole Normale Superieure, PSL Research University, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
| | - Huy Tran
- Ecole Normale Superieure, PSL Research University, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
| | - Teresa Ferraro
- Ecole Normale Superieure, PSL Research University, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
| | - Tanguy Lucas
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
- Institut Curie, PSL Research University, Paris, France
| | | | - Aurelien Guillou
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
- Institut Curie, PSL Research University, Paris, France
| | | | - Mathieu Coppey
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
- Institut Curie, PSL Research University, Paris, France
| | - Nathalie Dostatni
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
- Institut Curie, PSL Research University, Paris, France
| | - Aleksandra M. Walczak
- Ecole Normale Superieure, PSL Research University, Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris, France
- UMR3664/UMR168/UMR8549, CNRS, Paris, France
- * E-mail:
| |
Collapse
|