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McNamara HM, Solley SC, Adamson B, Chan MM, Toettcher JE. Recording morphogen signals reveals mechanisms underlying gastruloid symmetry breaking. Nat Cell Biol 2024:10.1038/s41556-024-01521-9. [PMID: 39358450 DOI: 10.1038/s41556-024-01521-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 09/05/2024] [Indexed: 10/04/2024]
Abstract
Aggregates of stem cells can break symmetry and self-organize into embryo-like structures with complex morphologies and gene expression patterns. Mechanisms including reaction-diffusion Turing patterns and cell sorting have been proposed to explain symmetry breaking but distinguishing between these candidate mechanisms of self-organization requires identifying which early asymmetries evolve into subsequent tissue patterns and cell fates. Here we use synthetic 'signal-recording' gene circuits to trace the evolution of signalling patterns in gastruloids, three-dimensional stem cell aggregates that form an anterior-posterior axis and structures resembling the mammalian primitive streak and tailbud. We find that cell sorting rearranges patchy domains of Wnt activity into a single pole that defines the gastruloid anterior-posterior axis. We also trace the emergence of Wnt domains to earlier heterogeneity in Nodal activity even before Wnt activity is detectable. Our study defines a mechanism through which aggregates of stem cells can form a patterning axis even in the absence of external spatial cues.
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Affiliation(s)
- Harold M McNamara
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
| | - Sabrina C Solley
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Britt Adamson
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Michelle M Chan
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Jared E Toettcher
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
- Omenn-Darling Bioengineering Institute, Princeton University, Princeton, NJ, USA.
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2
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Al Asafen H, Beseli A, Chen HY, Hiremath S, Williams CM, Reeves GT. Dynamics of BMP signaling and stable gene expression in the early Drosophila embryo. Biol Open 2024; 13:bio061646. [PMID: 39207258 PMCID: PMC11381920 DOI: 10.1242/bio.061646] [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: 07/19/2024] [Accepted: 07/24/2024] [Indexed: 09/04/2024] Open
Abstract
In developing tissues, morphogen gradients are thought to initialize gene expression patterns. However, the relationship between the dynamics of morphogen-encoded signals and gene expression decisions is largely unknown. Here we examine the dynamics of the Bone Morphogenetic Protein (BMP) pathway in Drosophila blastoderm-stage embryos. In this tissue, the BMP pathway is highly dynamic: it begins as a broad and weak signal on the dorsal half of the embryo, then 20-30 min later refines into a narrow, intense peak centered on the dorsal midline. This dynamical progression of the BMP signal raises questions of how it stably activates target genes. Therefore, we performed live imaging of the BMP signal and found that dorsal-lateral cells experience only a short transient in BMP signaling, after which the signal is lost completely. Moreover, we measured the transcriptional response of the BMP target gene pannier in live embryos and found it to remain activated in dorsal-lateral cells, even after the BMP signal is lost. Our findings may suggest that the BMP pathway activates a memory, or 'ratchet' mechanism that may sustain gene expression.
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Affiliation(s)
- Hadel Al Asafen
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Aydin Beseli
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Hung-Yuan Chen
- Department of Chemical Engineering, Texas A&M University, College Station, TX 77843,USA
| | - Sharva Hiremath
- Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695,USA
- North Carolina Plant Sciences Initiative, North Carolina State University, Raleigh, NC 27695,USA
| | - Cranos M. Williams
- Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695,USA
- North Carolina Plant Sciences Initiative, North Carolina State University, Raleigh, NC 27695,USA
| | - Gregory T. Reeves
- Department of Chemical Engineering, Texas A&M University, College Station, TX 77843,USA
- Interdisciplinary Graduate Program in Genetics, Texas A&M University, College Station, TX 77843,USA
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3
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Zhang L, Hodgins L, Sakib S, Verbeem A, Mahmood A, Perez-Romero C, Marmion RA, Dostatni N, Fradin C. Both the transcriptional activator, Bcd, and repressor, Cic, form small mobile oligomeric clusters. Biophys J 2024:S0006-3495(24)00558-7. [PMID: 39164967 DOI: 10.1016/j.bpj.2024.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 07/11/2024] [Accepted: 08/15/2024] [Indexed: 08/22/2024] Open
Abstract
Transcription factors play an essential role in pattern formation during early embryo development, generating a strikingly fast and precise transcriptional response that results in sharp gene expression boundaries. To characterize the steps leading up to transcription, we performed a side-by-side comparison of the nuclear dynamics of two morphogens, a transcriptional activator, Bicoid (Bcd), and a transcriptional repressor, Capicua (Cic), both involved in body patterning along the anterior-posterior axis of the early Drosophila embryo. We used a combination of fluorescence recovery after photobleaching, fluorescence correlation spectroscopy, and single-particle tracking to access a wide range of dynamical timescales. Despite their opposite effects on gene transcription, we find that Bcd and Cic have very similar nuclear dynamics, characterized by the coexistence of a freely diffusing monomer population with a number of oligomeric clusters, which range from low stoichiometry and high mobility clusters to larger, DNA-bound hubs. Our observations are consistent with the inclusion of both Bcd and Cic into transcriptional hubs or condensates, while putting constraints on the mechanism by which these form. These results fit in with the recent proposal that many transcription factors might share a common search strategy for target gene regulatory regions that makes use of their large unstructured regions, and may eventually help explain how the transcriptional response they elicit can be at the same time so fast and so precise.
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Affiliation(s)
- Lili Zhang
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
| | - Lydia Hodgins
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
| | - Shariful Sakib
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Alexander Verbeem
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
| | - Ahmad Mahmood
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
| | - Carmina Perez-Romero
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Robert A Marmion
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey
| | - Nathalie Dostatni
- Institut Curie, PSL University, CNRS, Sorbonne University, Nuclear Dynamics, Paris, France
| | - Cécile Fradin
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada.
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4
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Liberali P, Schier AF. The evolution of developmental biology through conceptual and technological revolutions. Cell 2024; 187:3461-3495. [PMID: 38906136 DOI: 10.1016/j.cell.2024.05.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 05/28/2024] [Accepted: 05/29/2024] [Indexed: 06/23/2024]
Abstract
Developmental biology-the study of the processes by which cells, tissues, and organisms develop and change over time-has entered a new golden age. After the molecular genetics revolution in the 80s and 90s and the diversification of the field in the early 21st century, we have entered a phase when powerful technologies provide new approaches and open unexplored avenues. Progress in the field has been accelerated by advances in genomics, imaging, engineering, and computational biology and by emerging model systems ranging from tardigrades to organoids. We summarize how revolutionary technologies have led to remarkable progress in understanding animal development. We describe how classic questions in gene regulation, pattern formation, morphogenesis, organogenesis, and stem cell biology are being revisited. We discuss the connections of development with evolution, self-organization, metabolism, time, and ecology. We speculate how developmental biology might evolve in an era of synthetic biology, artificial intelligence, and human engineering.
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Affiliation(s)
- Prisca Liberali
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland; University of Basel, Basel, Switzerland.
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5
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Chen PT, Levo M, Zoller B, Gregor T. Gene activity fully predicts transcriptional bursting dynamics. ARXIV 2024:arXiv:2304.08770v3. [PMID: 37131882 PMCID: PMC10153294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Transcription commonly occurs in bursts, with alternating productive (ON) and quiescent (OFF) periods, governing mRNA production rates. Yet, how transcription is regulated through bursting dynamics remains unresolved. Here, we conduct real-time measurements of endogenous transcriptional bursting with single-mRNA sensitivity. Leveraging the diverse transcriptional activities in early fly embryos, we uncover stringent relationships between bursting parameters. Specifically, we find that the durations of ON and OFF periods are linked. Regardless of the developmental stage or body-axis position, gene activity levels predict individual alleles' average ON and OFF periods. Lowly transcribing alleles predominantly modulate OFF periods (burst frequency), while highly transcribing alleles primarily tune ON periods (burst size). These relationships persist even under perturbations of cis-regulatory elements or trans-factors and account for bursting dynamics measured in other species. Our results suggest a novel mechanistic constraint governing bursting dynamics rather than a modular control of distinct parameters by distinct regulatory processes.
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Affiliation(s)
- Po-Ta Chen
- Joseph Henry Laboratories of Physics & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Michal Levo
- Joseph Henry Laboratories of Physics & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Benjamin Zoller
- Joseph Henry Laboratories of Physics & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Stem Cell and Developmental Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France
| | - Thomas Gregor
- Joseph Henry Laboratories of Physics & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Stem Cell and Developmental Biology, CNRS UMR3738 Paris Cité, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France
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6
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Li XC, Gandara L, Ekelöf M, Richter K, Alexandrov T, Crocker J. Rapid response of fly populations to gene dosage across development and generations. Nat Commun 2024; 15:4551. [PMID: 38811562 PMCID: PMC11137061 DOI: 10.1038/s41467-024-48960-4] [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: 09/06/2023] [Accepted: 05/17/2024] [Indexed: 05/31/2024] Open
Abstract
Although the effects of genetic and environmental perturbations on multicellular organisms are rarely restricted to single phenotypic layers, our current understanding of how developmental programs react to these challenges remains limited. Here, we have examined the phenotypic consequences of disturbing the bicoid regulatory network in early Drosophila embryos. We generated flies with two extra copies of bicoid, which causes a posterior shift of the network's regulatory outputs and a decrease in fitness. We subjected these flies to EMS mutagenesis, followed by experimental evolution. After only 8-15 generations, experimental populations have normalized patterns of gene expression and increased survival. Using a phenomics approach, we find that populations were normalized through rapid increases in embryo size driven by maternal changes in metabolism and ovariole development. We extend our results to additional populations of flies, demonstrating predictability. Together, our results necessitate a broader view of regulatory network evolution at the systems level.
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Affiliation(s)
- Xueying C Li
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
- College of Life Sciences, Beijing Normal University, Beijing, China.
| | - Lautaro Gandara
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Måns Ekelöf
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Kerstin Richter
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Theodore Alexandrov
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
- Molecular Medicine Partnership Unit between EMBL and Heidelberg University, Heidelberg, Germany
- BioInnovation Institute, Copenhagen, Denmark
| | - Justin Crocker
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
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7
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Dawson J, Bryant A, Jordan T, Bhikot S, Macon S, Walton B, Ajamu-Johnson A, Langridge PD, Malmi-Kakkada AN. Contact area and tissue growth dynamics shape synthetic juxtacrine signaling patterns. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.07.12.548752. [PMID: 37503188 PMCID: PMC10370035 DOI: 10.1101/2023.07.12.548752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Cell-cell communication through direct contact, or juxtacrine signaling, is important in development, disease, and many areas of physiology. Synthetic forms of juxtacrine signaling can be precisely controlled and operate orthogonally to native processes, making them a powerful reductionist tool with which to address fundamental questions in cell-cell communication in vivo. Here we investigate how cell-cell contact length and tissue growth dynamics affect juxtacrine signal responses through implementing a custom synthetic gene circuit in Drosophila wing imaginal discs alongside mathematical modeling to determine synthetic Notch (synNotch) activation patterns. We find that the area of contact between cells largely determines the extent of synNotch activation, leading to the prediction that the shape of the interface between signal-sending and signal-receiving cells will impact the magnitude of the synNotch response. Notably, synNotch outputs form a graded spatial profile that extends several cell diameters from the signal source, providing evidence that the response to juxtacrine signals can persist in cells as they proliferate away from source cells, or that cells remain able to communicate directly over several cell diameters. Our model suggests the former mechanism may be sufficient, since it predicts graded outputs without diffusion or long-range cell-cell communication. Overall, we identify that cell-cell contact area together with output synthesis and decay rates likely govern the pattern of synNotch outputs in both space and time during tissue growth, insights that may have broader implications for juxtacrine signaling in general.
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8
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Recouvreux P, Pai P, Dunsing V, Torro R, Ludanyi M, Mélénec P, Boughzala M, Bertrand V, Lenne PF. Transfer of polarity information via diffusion of Wnt ligands in C. elegans embryos. Curr Biol 2024; 34:1853-1865.e6. [PMID: 38604167 DOI: 10.1016/j.cub.2024.03.030] [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: 01/18/2023] [Revised: 10/26/2023] [Accepted: 03/18/2024] [Indexed: 04/13/2024]
Abstract
Different signaling mechanisms concur to ensure robust tissue patterning and cell fate instruction during animal development. Most of these mechanisms rely on signaling proteins that are produced, transported, and detected. The spatiotemporal dynamics of signaling molecules are largely unknown, yet they determine signal activity's spatial range and time frame. Here, we use the Caenorhabditis elegans embryo to study how Wnt ligands, an evolutionarily conserved family of signaling proteins, dynamically organize to establish cell polarity in a developing tissue. We identify how Wnt ligands, produced in the posterior half of the embryos, spread extracellularly to transmit information to distant target cells in the anterior half. With quantitative live imaging and fluorescence correlation spectroscopy, we show that Wnt ligands diffuse through the embryo over a timescale shorter than the cell cycle, in the intercellular space, and outside the tissue below the eggshell. We extracted diffusion coefficients of Wnt ligands and their receptor Frizzled and characterized their co-localization. Integrating our different measurements and observations in a simple computational framework, we show how fast diffusion in the embryo can polarize individual cells through a time integration of the arrival of the ligands at the target cells. The polarity established at the tissue level by a posterior Wnt source can be transferred to the cellular level. Our results support a diffusion-based long-range Wnt signaling, which is consistent with the dynamics of developing processes.
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Affiliation(s)
- Pierre Recouvreux
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France.
| | - Pritha Pai
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Valentin Dunsing
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Rémy Torro
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Monika Ludanyi
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Pauline Mélénec
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Mariem Boughzala
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Vincent Bertrand
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Pierre-François Lenne
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
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9
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Clarke DN, Martin AC. Morphogenesis: Setting the pace of embryo folding. Curr Biol 2024; 34:R286-R288. [PMID: 38593774 DOI: 10.1016/j.cub.2024.02.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Tissue folding is a key process for shape generation during embryonic development. A new study reports how a fold in the Drosophila embryo forms by a propagating trigger wave.
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Affiliation(s)
- D Nathaniel Clarke
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Adam C Martin
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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10
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Tang WH, Sim SR, Aik DYK, Nelanuthala AVS, Athilingam T, Röllin A, Wohland T. Deep learning reduces data requirements and allows real-time measurements in imaging FCS. Biophys J 2024; 123:655-666. [PMID: 38050354 PMCID: PMC10995408 DOI: 10.1016/j.bpj.2023.11.3403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/18/2023] [Accepted: 11/30/2023] [Indexed: 12/06/2023] Open
Abstract
Imaging fluorescence correlation spectroscopy (FCS) is a powerful tool to extract information on molecular mobilities, actions, and interactions in live cells, tissues, and organisms. Nevertheless, several limitations restrict its applicability. First, FCS is data hungry, requiring 50,000 frames at 1-ms time resolution to obtain accurate parameter estimates. Second, the data size makes evaluation slow. Third, as FCS evaluation is model dependent, data evaluation is significantly slowed unless analytic models are available. Here, we introduce two convolutional neural networks-FCSNet and ImFCSNet-for correlation and intensity trace analysis, respectively. FCSNet robustly predicts parameters in 2D and 3D live samples. ImFCSNet reduces the amount of data required for accurate parameter retrieval by at least one order of magnitude and makes correct estimates even in moderately defocused samples. Both convolutional neural networks are trained on simulated data, are model agnostic, and allow autonomous, real-time evaluation of imaging FCS measurements.
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Affiliation(s)
- Wai Hoh Tang
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore; Department of Statistics and Data Science, National University of Singapore, Singapore, Singapore; Institute of Digital Molecular Analytics and Science, National University of Singapore, Singapore, Singapore
| | - Shao Ren Sim
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore
| | - Daniel Ying Kia Aik
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore; Institute of Digital Molecular Analytics and Science, National University of Singapore, Singapore, Singapore; Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Ashwin Venkata Subba Nelanuthala
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore
| | | | - Adrian Röllin
- Department of Statistics and Data Science, National University of Singapore, Singapore, Singapore
| | - Thorsten Wohland
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore; NUS Centre for Bio-Imaging Sciences, National University of Singapore, Singapore, Singapore; Institute of Digital Molecular Analytics and Science, National University of Singapore, Singapore, Singapore; Department of Chemistry, National University of Singapore, Singapore, Singapore.
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11
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Athilingam T, Nelanuthala AVS, Breen C, Karedla N, Fritzsche M, Wohland T, Saunders TE. Long-range formation of the Bicoid gradient requires multiple dynamic modes that spatially vary across the embryo. Development 2024; 151:dev202128. [PMID: 38345326 PMCID: PMC10911119 DOI: 10.1242/dev.202128] [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: 06/26/2023] [Accepted: 01/03/2024] [Indexed: 02/15/2024]
Abstract
Morphogen gradients provide essential positional information to gene networks through their spatially heterogeneous distribution, yet how they form is still hotly contested, with multiple models proposed for different systems. Here, we focus on the transcription factor Bicoid (Bcd), a morphogen that forms an exponential gradient across the anterior-posterior (AP) axis of the early Drosophila embryo. Using fluorescence correlation spectroscopy we find there are spatial differences in Bcd diffusivity along the AP axis, with Bcd diffusing more rapidly in the posterior. We establish that such spatially varying differences in Bcd dynamics are sufficient to explain how Bcd can have a steep exponential gradient in the anterior half of the embryo and yet still have an observable fraction of Bcd near the posterior pole. In the nucleus, we demonstrate that Bcd dynamics are impacted by binding to DNA. Addition of the Bcd homeodomain to eGFP::NLS qualitatively replicates the Bcd concentration profile, suggesting this domain regulates Bcd dynamics. Our results reveal how a long-range gradient can form while retaining a steep profile through much of its range.
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Affiliation(s)
- Thamarailingam Athilingam
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
- Mechanobiology Institute, National University of Singapore, Singapore117411
| | - Ashwin V. S. Nelanuthala
- Department of Biological Sciences and Centre for Bioimaging Sciences, National University of Singapore, Singapore117558
| | | | - Narain Karedla
- Kennedy Institute of Rheumatology, University of Oxford, Oxford, OX3 7LF, UK
| | - Marco Fritzsche
- Kennedy Institute of Rheumatology, University of Oxford, Oxford, OX3 7LF, UK
| | - Thorsten Wohland
- Department of Biological Sciences and Centre for Bioimaging Sciences, National University of Singapore, Singapore117558
- Department of Chemistry, National University of Singapore, Singapore117558
| | - Timothy E. Saunders
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
- Mechanobiology Institute, National University of Singapore, Singapore117411
- Department of Biological Sciences and Centre for Bioimaging Sciences, National University of Singapore, Singapore117558
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12
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Baumgartner S. Revisiting bicoid function: complete inactivation reveals an additional fundamental role in Drosophila egg geometry specification. Hereditas 2024; 161:1. [PMID: 38167241 PMCID: PMC10759373 DOI: 10.1186/s41065-023-00305-9] [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: 11/15/2023] [Accepted: 12/18/2023] [Indexed: 01/05/2024] Open
Abstract
INTRODUCTION The bicoid (bcd) gene in Drosophila has served as a paradigm for a morphogen in textbooks for decades. Discovered in 1986 as a mutation affecting anterior development in the embryo, its expression pattern as a protein gradient later confirmed the prediction from transplantation experiments. These experiments suggested that the protein fulfills the criteria of a true morphogen, with the existence of a homeodomain crucial for activation of genes along the anterior-posterior axis, based on the concentration of the morphogen. The bcd gene undergoes alternative splicing, resulting in, among other isoforms, a small and often neglected isoform with low abundance, which lacks the homeodomain, termed small bicoid (smbcd). Most importantly, all known classical strong bcd alleles used in the past to determine bcd function apparently do not affect the function of this isoform. RESULTS To overcome the uncertainty regarding which isoform regulates what, I removed the bcd locus entirely using CRISPR technology. bcdCRISPR eggs exhibited a short and round appearance. The phenotype could be ascribed to smbcd because all bcd alleles affecting the function of the major transcript, termed large bicoid (lgbcd) showed normally sized eggs. Several patterning genes for the embryo showed expression in the oocyte, and their expression patterns were altered in bcdCRISPR oocytes. In bcdCRISPR embryos, all downstream segmentation genes showed altered expression patterns, consistent with the expression patterns in "classical" alleles; however, due to the altered egg geometry resulting in fewer blastoderm nuclei, additional constraints came into play, further affecting their expression patterns. CONCLUSIONS This study unveils a novel and fundamental role of bcd in shaping the egg's geometry. This discovery demands a comprehensive revision of our understanding of this important patterning gene and prompts a reevaluation of past experiments conducted under the assumption that bcd mutants were bcdnull-mutants.
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Affiliation(s)
- Stefan Baumgartner
- Dept. of Experimental Medical Sciences, Lund University, Lund, S-22184, Sweden.
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13
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Nikolić M, Antonetti V, Liu F, Muhaxheri G, Petkova MD, Scheeler M, Smith EM, Bialek W, Gregor T. Scale invariance in early embryonic development. ARXIV 2023:arXiv:2312.17684v1. [PMID: 38235065 PMCID: PMC10793483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
The body plan of the fruit fly is determined by the expression of just a handful of genes. We show that the spatial patterns of expression for several of these genes scale precisely with the size of the embryo. Concretely, discrete positional markers such as the peaks in striped patterns have absolute positions along the anterior-posterior axis that are proportional to embryo length, with better than 1% accuracy. Further, the information (in bits) that graded patterns of expression provide about position can be decomposed into information about fractional or scaled position and information about absolute position or embryo length; all of the available information is about scaled position, again with ~ 1% accuracy. These observations suggest that the underlying genetic network exhibits scale invariance in a deeper mathematical sense. Taking this mathematical statement seriously requires that the network dynamics have a zero mode, which connects to many other observations on this system.
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Affiliation(s)
- Miloš Nikolić
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
| | - Victoria Antonetti
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Center for Quantitative Biology and School of Physics, Peking University, Beijing 100871 China
| | - Feng Liu
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
- Center for Quantitative Biology and School of Physics, Peking University, Beijing 100871 China
| | - Gentian Muhaxheri
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Department of Physics, Lehman College, City University of New York, Bronx, NY 10468 USA
| | | | - Martin Scheeler
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
| | - Eric M Smith
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
| | - William Bialek
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
- Initiative for the Theoretical Sciences, The Graduate Center, City University of New York, 365 Fifth Ave., New York, NY 10016 USA
| | - Thomas Gregor
- Joseph Henry Laboratories of Physics and Princeton University, Princeton NJ 08544 USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
- Department of Developmental and Stem Cell Biology UMR3738, Institut Pasteur, 75015 Paris, France
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14
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Zhu H, O’Shaughnessy B. Actomyosin pulsing rescues embryonic tissue folding from disruption by myosin fluctuations. RESEARCH SQUARE 2023:rs.3.rs-2948564. [PMID: 37886516 PMCID: PMC10602173 DOI: 10.21203/rs.3.rs-2948564/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
During early development, myosin II mechanically reshapes and folds embryo tissue. A muchstudied example is ventral furrow formation in Drosophila, marking the onset of gastrulation. Furrowing is driven by contraction of actomyosin networks on apical cell surfaces, but how the myosin patterning encodes tissue shape is unclear, and elastic models failed to reproduce essential features of experimental cell contraction profiles. The myosin patterning exhibits substantial cell-to-cell fluctuations with pulsatile time-dependence, a striking but unexplained feature of morphogenesis in many organisms. Here, using biophysical modeling we find viscous forces offer the principal resistance to actomyosin-driven apical constriction. In consequence, tissue shape is encoded in the direction-dependent curvature of the myosin patterning which orients an anterior-posterior furrow. Tissue contraction is highly sensitive to cell-to-cell myosin fluctuations, explaining furrowing failure in genetically perturbed embryos whose fluctuations are temporally persistent. In wild-type embryos this disastrous outcome is averted by pulsatile myosin time-dependence, which rescues furrowing by eliminating high frequencies in the fluctuation power spectrum. This low pass filter mechanism may underlie the usage of actomyosin pulsing in diverse morphogenetic processes across many organisms.
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Affiliation(s)
- Hongkang Zhu
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Ben O’Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
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15
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Zhu H, Oâ Shaughnessy B. Actomyosin pulsing rescues embryonic tissue folding from disruption by myosin fluctuations. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.16.533016. [PMID: 36993262 PMCID: PMC10055118 DOI: 10.1101/2023.03.16.533016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
During early development, myosin II mechanically reshapes and folds embryo tissue. A much-studied example is ventral furrow formation in Drosophila , marking the onset of gastrulation. Furrowing is driven by contraction of actomyosin networks on apical cell surfaces, but how the myosin patterning encodes tissue shape is unclear, and elastic models failed to reproduce essential features of experimental cell contraction profiles. The myosin patterning exhibits substantial cell-to-cell fluctuations with pulsatile time-dependence, a striking but unexplained feature of morphogenesis in many organisms. Here, using biophysical modeling we find viscous forces offer the principle resistance to actomyosin-driven apical constriction. In consequence, tissue shape is encoded in the direction-dependent curvature of the myosin patterning which orients an anterior-posterior furrow. Tissue contraction is highly sensitive to cell-to-cell myosin fluctuations, explaining furrowing failure in genetically perturbed embryos whose fluctuations are temporally persistent. In wild-type embryos, this catastrophic outcome is averted by pulsatile myosin time-dependence, a time-averaging effect that rescues furrowing. This low pass filter mechanism may underlie the usage of actomyosin pulsing in diverse morphogenetic processes across many organisms.
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16
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Iyer KS, Prabhakara C, Mayor S, Rao M. Cellular compartmentalisation and receptor promiscuity as a strategy for accurate and robust inference of position during morphogenesis. eLife 2023; 12:e79257. [PMID: 36877545 PMCID: PMC9988261 DOI: 10.7554/elife.79257] [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: 04/05/2022] [Accepted: 01/14/2023] [Indexed: 03/07/2023] Open
Abstract
Precise spatial patterning of cell fate during morphogenesis requires accurate inference of cellular position. In making such inferences from morphogen profiles, cells must contend with inherent stochasticity in morphogen production, transport, sensing and signalling. Motivated by the multitude of signalling mechanisms in various developmental contexts, we show how cells may utilise multiple tiers of processing (compartmentalisation) and parallel branches (multiple receptor types), together with feedback control, to bring about fidelity in morphogenetic decoding of their positions within a developing tissue. By simultaneously deploying specific and nonspecific receptors, cells achieve a more accurate and robust inference. We explore these ideas in the patterning of Drosophila melanogaster wing imaginal disc by Wingless morphogen signalling, where multiple endocytic pathways participate in decoding the morphogen gradient. The geometry of the inference landscape in the high dimensional space of parameters provides a measure for robustness and delineates stiff and sloppy directions. This distributed information processing at the scale of the cell highlights how local cell autonomous control facilitates global tissue scale design.
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Affiliation(s)
- Krishnan S Iyer
- Simons Center for the Study of Living Machines, National Center for Biological Sciences - TIFRBangaloreIndia
| | | | - Satyajit Mayor
- National Center for Biological Sciences - TIFRBangaloreIndia
| | - Madan Rao
- Simons Center for the Study of Living Machines, National Center for Biological Sciences - TIFRBangaloreIndia
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17
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Majka M, Ho RDJG, Zagorski M. Stability of Pattern Formation in Systems with Dynamic Source Regions. PHYSICAL REVIEW LETTERS 2023; 130:098402. [PMID: 36930916 DOI: 10.1103/physrevlett.130.098402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
We explain the principles of gene expression pattern stabilization in systems of interacting, diffusible morphogens, with dynamically established source regions. Using a reaction-diffusion model with a step-function production term, we identify the phase transition between low-precision indeterminate patterning and the phase in which a traveling, well-defined contact zone between two domains is formed. Our model analytically explains single- and two-gene domain dynamics and provides pattern stability conditions for all possible two-gene regulatory network motifs.
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Affiliation(s)
- M Majka
- Institute of Theoretical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland
| | - R D J G Ho
- Institute of Theoretical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland
| | - M Zagorski
- Institute of Theoretical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland
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18
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Espina JA, Cordeiro MH, Barriga EH. Tissue interplay during morphogenesis. Semin Cell Dev Biol 2023; 147:12-23. [PMID: 37002130 DOI: 10.1016/j.semcdb.2023.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/25/2023] [Accepted: 03/25/2023] [Indexed: 03/31/2023]
Abstract
The process by which biological systems such as cells, tissues and organisms acquire shape has been named as morphogenesis and it is central to a plethora of biological contexts including embryo development, wound healing, or even cancer. Morphogenesis relies in both self-organising properties of the system and in environmental inputs (biochemical and biophysical). The classical view of morphogenesis is based on the study of external biochemical molecules, such as morphogens. However, recent studies are establishing that the mechanical environment is also used by cells to communicate within tissues, suggesting that this mechanical crosstalk is essential to synchronise morphogenetic transitions and self-organisation. In this article we discuss how tissue interaction drive robust morphogenesis, starting from a classical biochemical view, to finalise with more recent advances on how the biophysical properties of a tissue feedback with their surroundings to allow form acquisition. We also comment on how in silico models aid to integrate and predict changes in cell and tissue behaviour. Finally, considering recent advances from the developmental biomechanics field showing that mechanical inputs work as cues that promote morphogenesis, we invite to revisit the concept of morphogen.
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Affiliation(s)
- Jaime A Espina
- Mechanisms of Morphogenesis Lab, Gulbenkian Institute of Science (IGC), Oeiras, Portugal
| | - Marilia H Cordeiro
- Mechanisms of Morphogenesis Lab, Gulbenkian Institute of Science (IGC), Oeiras, Portugal
| | - Elias H Barriga
- Mechanisms of Morphogenesis Lab, Gulbenkian Institute of Science (IGC), Oeiras, Portugal.
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19
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Kuhn T, Landge AN, Mörsdorf D, Coßmann J, Gerstenecker J, Čapek D, Müller P, Gebhardt JCM. Single-molecule tracking of Nodal and Lefty in live zebrafish embryos supports hindered diffusion model. Nat Commun 2022; 13:6101. [PMID: 36243734 PMCID: PMC9569377 DOI: 10.1038/s41467-022-33704-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 09/28/2022] [Indexed: 12/24/2022] Open
Abstract
The hindered diffusion model postulates that the movement of a signaling molecule through an embryo is affected by tissue geometry and binding-mediated hindrance, but these effects have not been directly demonstrated in vivo. Here, we visualize extracellular movement and binding of individual molecules of the activator-inhibitor signaling pair Nodal and Lefty in live developing zebrafish embryos using reflected light-sheet microscopy. We observe that diffusion coefficients of molecules are high in extracellular cavities, whereas mobility is reduced and bound fractions are high within cell-cell interfaces. Counterintuitively, molecules nevertheless accumulate in cavities, which we attribute to the geometry of the extracellular space by agent-based simulations. We further find that Nodal has a larger bound fraction than Lefty and shows a binding time of tens of seconds. Together, our measurements and simulations provide direct support for the hindered diffusion model and yield insights into the nanometer-to-micrometer-scale mechanisms that lead to macroscopic signal dispersal.
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Affiliation(s)
- Timo Kuhn
- grid.6582.90000 0004 1936 9748Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Amit N. Landge
- grid.9811.10000 0001 0658 7699University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - David Mörsdorf
- grid.418026.90000 0004 0492 0357Friedrich Miescher Laboratory of the Max Planck Society, Max-Planck-Ring 9, 72076 Tübingen, Germany ,grid.10420.370000 0001 2286 1424University of Vienna, Department of Neurosciences and Developmental Biology, Djerassiplatz 1, 1030 Vienna, Austria
| | - Jonas Coßmann
- grid.6582.90000 0004 1936 9748Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Johanna Gerstenecker
- grid.6582.90000 0004 1936 9748Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Daniel Čapek
- grid.9811.10000 0001 0658 7699University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Patrick Müller
- grid.9811.10000 0001 0658 7699University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany ,grid.418026.90000 0004 0492 0357Friedrich Miescher Laboratory of the Max Planck Society, Max-Planck-Ring 9, 72076 Tübingen, Germany
| | - J. Christof M. Gebhardt
- grid.6582.90000 0004 1936 9748Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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20
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Baltruk LJ, Lavezzo GM, Machado-Lima A, Digiampietri LA, Andrioli LP. An additive repression mechanism sets the anterior limits of anterior pair-rule stripes 1. Cells Dev 2022; 171:203802. [PMID: 35934285 DOI: 10.1016/j.cdev.2022.203802] [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: 02/22/2022] [Revised: 07/28/2022] [Accepted: 07/29/2022] [Indexed: 01/25/2023]
Abstract
Segments are repeated anatomical units forming the body of insects. In Drosophila, the specification of the body takes place during the blastoderm through the segmentation cascade. Pair-rule genes such as hairy (h), even-skipped (eve), runt (run), and fushi-tarazu (ftz) are of the intermediate level of the cascade and each pair-rule gene is expressed in seven transversal stripes along the antero-posterior axis of the embryo. Stripes are formed by independent cis-regulatory modules (CRMs) under the regulation of transcription factors of maternal source and of gap proteins of the first level of the cascade. The initial blastoderm of Drosophila is a syncytium and it also coincides with the mid-blastula transition when thousands of zygotic genes are transcribed and their products are able to diffuse in the cytoplasm. Thus, we anticipated a complex regulation of the CRMs of the pair-rule stripes. The CRMs of h 1, eve 1, run 1, ftz 1 are able to be activated by bicoid (bcd) throughout the anterior blastoderm and several lines of evidence indicate that they are repressed by the anterior gap genes slp1 (sloppy-paired 1), tll (tailless) and hkb (huckebein). The modest activity of these repressors led to the premise of a combinatorial mechanism regulating the expression of the CRMs of h 1, eve 1, run 1, ftz 1 in more anterior regions of the embryo. We tested this possibility by progressively removing the repression activities of slp1, tll and hkb. In doing so, we were able to expose a mechanism of additive repression limiting the anterior borders of stripes 1. Stripes 1 respond depending on their distance from the anterior end and repressors operating at different levels.
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Affiliation(s)
| | - Guilherme Miura Lavezzo
- Program on Bioinformatics, Institute of Mathematics and Statistics, University of São Paulo, São Paulo, Brazil
| | - Ariane Machado-Lima
- Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, São Paulo, SP, Brazil; Program on Bioinformatics, Institute of Mathematics and Statistics, University of São Paulo, São Paulo, Brazil
| | | | - Luiz Paulo Andrioli
- Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, São Paulo, SP, Brazil.
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21
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Dickmann JEM, Rink JC, Jülicher F. Long-range morphogen gradient formation by cell-to-cell signal propagation. Phys Biol 2022; 19. [PMID: 35921820 DOI: 10.1088/1478-3975/ac86b4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 08/03/2022] [Indexed: 11/12/2022]
Abstract
Morphogen gradients are a central concept in developmental biology. Their formation often involves the secretion of morphogens from a local source, that spread by diffusion in the cell field, where molecules eventually get degraded. This implies limits to both the time and length scales over which morphogen gradients can form which are set by diffusion coefficients and degradation rates. Towards the goal of identifying plausible mechanisms capable of extending the gradient range, we here use theory to explore properties of a cell-to-cell signaling relay. Inspired by the millimeter-scale Wnt-expression and signaling gradients in flatworms, we consider morphogen-mediated morphogen production in the cell field. We show that such a relay can generate stable morphogen and signaling gradients that are oriented by a local, morphogen-independent source of morphogen at a boundary. This gradient formation can be related to an effective diffusion and an effective degradation that result from morphogen production due to signaling relay. If the secretion of morphogen produced in response to the relay is polarized, it further gives rise to an effective drift. We find that signaling relay can generate long-ranged gradients in relevant times without relying on extreme choices of diffusion coefficients or degradation rates, thus exceeding the limits set by physiological diffusion coefficients and degradation rates. A signaling relay is hence an attractive principle to conceptualize long-range gradient formation by slowly diffusing morphogens that are relevant for patterning in adult contexts such as regeneration and tissue turn-over.
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Affiliation(s)
- Johanna E M Dickmann
- Max-Planck-Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, Dresden, Sachsen, 01187, GERMANY
| | - Jochen C Rink
- Max Planck Institute for Multidisciplinary Sciences, Am Faßberg 11, Gottingen, Niedersachsen, 37077, GERMANY
| | - Frank Jülicher
- Max-Planck-Institut fuer Physik komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Dresden, 01187, GERMANY
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22
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Shen J, Liu F, Tang C. Scaling dictates the decoder structure. Sci Bull (Beijing) 2022; 67:1486-1495. [PMID: 36546192 DOI: 10.1016/j.scib.2022.06.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 05/06/2022] [Accepted: 06/13/2022] [Indexed: 01/07/2023]
Abstract
Despite fluctuations in embryo size within a species, the spatial gene expression pattern and hence the embryonic structure can nonetheless maintain the correct proportion to the embryo size. This is known as the scaling phenomenon. For morphogen-induced patterning of gene expression, the positional information encoded in the local morphogen concentrations is decoded by the downstream genetic network (the decoder). In this paper, we show that the requirement of scaling sets severe constraints on the geometric structure of such a local decoder, which in turn enables deduction of mutants' behavior and extraction of regulation information without going into any molecular details. We demonstrate that the Drosophila gap gene system achieves scaling in the way consistent with our theory-the decoder geometry required by scaling correctly accounts for the observed gap gene expression pattern in nearly all maternal morphogen mutants. Furthermore, the regulation logic and the coding/decoding strategy of the gap gene system can also be revealed from the decoder geometry. Our work provides a general theoretical framework for a large class of problems where scaling output is achieved by non-scaling inputs and a local decoder, as well as a unified understanding of scaling, mutants' behavior, and gene regulation for the Drosophila gap gene system.
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Affiliation(s)
- Jingxiang Shen
- Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Feng Liu
- Center for Quantitative Biology, Peking University, Beijing 100871, China; School of Physics, Peking University, Beijing 100871, China
| | - Chao Tang
- Center for Quantitative Biology, Peking University, Beijing 100871, China; School of Physics, Peking University, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China.
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23
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Lee HC, Hastings C, Oliveira NMM, Pérez-Carrasco R, Page KM, Wolpert L, Stern CD. 'Neighbourhood watch' model: embryonic epiblast cells assess positional information in relation to their neighbours. Development 2022; 149:275390. [PMID: 35438131 PMCID: PMC9188750 DOI: 10.1242/dev.200295] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 04/11/2022] [Indexed: 12/21/2022]
Abstract
In many developing and regenerating systems, tissue pattern is established through gradients of informative morphogens, but we know little about how cells interpret these. Using experimental manipulation of early chick embryos, including misexpression of an inducer (VG1 or ACTIVIN) and an inhibitor (BMP4), we test two alternative models for their ability to explain how the site of primitive streak formation is positioned relative to the rest of the embryo. In one model, cells read morphogen concentrations cell-autonomously. In the other, cells sense changes in morphogen status relative to their neighbourhood. We find that only the latter model can account for the experimental results, including some counter-intuitive predictions. This mechanism (which we name the ‘neighbourhood watch’ model) illuminates the classic ‘French Flag Problem’ and how positional information is interpreted by a sheet of cells in a large developing system. Summary: In a large developing system, the chick embryo before gastrulation, cells may interpret gradients of positional signals relative to their neighbours to position the primitive streak, establishing bilateral symmetry.
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Affiliation(s)
- Hyung Chul Lee
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Cato Hastings
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Nidia M M Oliveira
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Rubén Pérez-Carrasco
- Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Karen M Page
- Department of Mathematics, University College London, Gower Street, London WC1E 6BT, UK
| | - Lewis Wolpert
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Claudio D Stern
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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24
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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.
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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
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25
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Schmidt-Ott U, Yoon Y. Evolution and loss of ß-catenin and TCF-dependent axis specification in insects. CURRENT OPINION IN INSECT SCIENCE 2022; 50:100877. [PMID: 35104659 PMCID: PMC9133022 DOI: 10.1016/j.cois.2022.100877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/06/2022] [Accepted: 01/11/2022] [Indexed: 06/14/2023]
Abstract
Mechanisms and evolution of primary axis specification in insects are discussed in the context of the roles of ß-catenin and TCF in polarizing metazoan embryos. Three hypotheses are presented. First, insects with sequential segmentation and posterior growth use cell-autonomous mechanisms for establishing embryo polarity via the nuclear ratio of ß-catenin and TCF. Second, TCF homologs establish competence for anterior specification. Third, the evolution of simultaneous segmentation mechanisms, also known as long-germ development, resulted in primary axis specification mechanisms that are independent of ß-catenin but reliant on TCF, a condition that preceded the frequent replacement of anterior determinants in long germ insects.
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Affiliation(s)
- Urs Schmidt-Ott
- University of Chicago, Dept. of Organismal Biology and Anatomy, 1027 East 57th Street, Chicago, IL 60637, USA.
| | - Yoseop Yoon
- University of California, Irvine, Dept. of Microbiology and Molecular Genetics, School of Medicine, 811 Health Sciences Rd., Med Sci B262, CA 92617, USA
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26
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Datta A, Ghosh S, Kondev J. How to assemble a scale-invariant gradient. eLife 2022; 11:71365. [PMID: 35311649 PMCID: PMC8986316 DOI: 10.7554/elife.71365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 03/20/2022] [Indexed: 11/17/2022] Open
Abstract
Intracellular protein gradients serve a variety of functions, such as the establishment of cell polarity or to provide positional information for gene expression in developing embryos. Given that cell size in a population can vary considerably, for the protein gradients to work properly they often have to be scaled to the size of the cell. Here, we examine a model of protein gradient formation within a cell that relies on cytoplasmic diffusion and cortical transport of proteins toward a cell pole. We show that the shape of the protein gradient is determined solely by the cell geometry. Furthermore, we show that the length scale over which the protein concentration in the gradient varies is determined by the linear dimensions of the cell, independent of the diffusion constant or the transport speed. This gradient provides scale-invariant positional information within a cell, which can be used for assembly of intracellular structures whose size is scaled to the linear dimensions of the cell, such as the cytokinetic ring and actin cables in budding yeast cells.
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Affiliation(s)
- Arnab Datta
- Department of Physics, Brandeis University, Waltham, United States
| | - Sagnik Ghosh
- Department of Physics, Brandeis University, Waltham, United States
| | - Jane Kondev
- Department of Physics, Brandeis University, Waltham, United States
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27
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Ceccarelli AS, Borges A, Chara O. Size matters: tissue size as a marker for a transition between reaction-diffusion regimes in spatio-temporal distribution of morphogens. ROYAL SOCIETY OPEN SCIENCE 2022; 9:211112. [PMID: 35116146 PMCID: PMC8790355 DOI: 10.1098/rsos.211112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Abstract
The reaction-diffusion model constitutes one of the most influential mathematical models to study distribution of morphogens in tissues. Despite its widespread use, the effect of finite tissue size on model-predicted spatio-temporal morphogen distributions has not been completely elucidated. In this study, we analytically investigated the spatio-temporal distributions of morphogens predicted by a reaction-diffusion model in a finite one-dimensional domain, as a proxy for a biological tissue, and compared it with the solution of the infinite-domain model. We explored the reduced parameter, the tissue length in units of a characteristic reaction-diffusion length, and identified two reaction-diffusion regimes separated by a crossover tissue size estimated in approximately three characteristic reaction-diffusion lengths. While above this crossover the infinite-domain model constitutes a good approximation, it breaks below this crossover, whereas the finite-domain model faithfully describes the entire parameter space. We evaluated whether the infinite-domain model renders accurate estimations of diffusion coefficients when fitted to finite spatial profiles, a procedure typically followed in fluorescence recovery after photobleaching (FRAP) experiments. We found that the infinite-domain model overestimates diffusion coefficients when the domain is smaller than the crossover tissue size. Thus, the crossover tissue size may be instrumental in selecting the suitable reaction-diffusion model to study tissue morphogenesis.
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Affiliation(s)
- Alberto S. Ceccarelli
- Systems Biology Group (SysBio), Institute of Physics of Liquids and Biological Systems (IFLySIB), National Scientific and Technical Research Council (CONICET), University of La Plata, La Plata, Argentina
| | - Augusto Borges
- Systems Biology Group (SysBio), Institute of Physics of Liquids and Biological Systems (IFLySIB), National Scientific and Technical Research Council (CONICET), University of La Plata, La Plata, Argentina
- Research Unit of Sensory Biology & Organogenesis, Helmholtz Zentrum München, Munich, Germany
- Graduate School of Quantitative Biosciences (QBM), Munich, Germany
| | - Osvaldo Chara
- Systems Biology Group (SysBio), Institute of Physics of Liquids and Biological Systems (IFLySIB), National Scientific and Technical Research Council (CONICET), University of La Plata, La Plata, Argentina
- Center for Information Services and High Performance Computing (ZIH), Technische Universität Dresden, Dresden, Germany
- Instituto de Tecnología, Universidad Argentina de la Empresa (UADE), Buenos Aires, Argentina
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28
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Veerman F, Mercker M, Marciniak-Czochra A. Beyond Turing: far-from-equilibrium patterns and mechano-chemical feedback. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20200278. [PMID: 34743599 DOI: 10.1098/rsta.2020.0278] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Turing patterns are commonly understood as specific instabilities of a spatially homogeneous steady state, resulting from activator-inhibitor interaction destabilized by diffusion. We argue that this view is restrictive and its agreement with biological observations is problematic. We present two alternatives to the classical Turing analysis of patterns. First, we employ the abstract framework of evolution equations to enable the study of far-from-equilibrium patterns. Second, we introduce a mechano-chemical model, with the surface on which the pattern forms being dynamic and playing an active role in the pattern formation, effectively replacing the inhibitor. We highlight the advantages of these two alternatives vis-à-vis the classical Turing analysis, and give an overview of recent results and future challenges for both approaches. This article is part of the theme issue 'Recent progress and open frontiers in Turing's theory of morphogenesis'.
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Affiliation(s)
- Frits Veerman
- University of Leiden, Mathematical Institute, Niels Bohrweg 1, Leiden 2333 CA, The Netherlands
| | - Moritz Mercker
- Institute for Applied Mathematics and Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Im Neuenheimer Feld 205, Heidelberg 69120, Germany
| | - Anna Marciniak-Czochra
- Institute for Applied Mathematics and Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Im Neuenheimer Feld 205, Heidelberg 69120, Germany
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29
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Zhang L, Perez-Romero C, Dostatni N, Fradin C. Using FCS to accurately measure protein concentration in the presence of noise and photobleaching. Biophys J 2021; 120:4230-4241. [PMID: 34242593 PMCID: PMC8516637 DOI: 10.1016/j.bpj.2021.06.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 06/02/2021] [Accepted: 06/28/2021] [Indexed: 11/24/2022] Open
Abstract
Quantitative cell biology requires precise and accurate concentration measurements, resolved both in space and time. Fluorescence correlation spectroscopy (FCS) has been held as a promising technique to perform such measurements because the fluorescence fluctuations it relies on are directly dependent on the absolute number of fluorophores in the detection volume. However, the most interesting applications are in cells, where autofluorescence and confinement result in strong background noise and important levels of photobleaching. Both noise and photobleaching introduce systematic bias in FCS concentration measurements and need to be corrected for. Here, we propose to make use of the photobleaching inevitably occurring in confined environments to perform series of FCS measurements at different fluorophore concentration, which we show allows a precise in situ measurement of both background noise and molecular brightness. Such a measurement can then be used as a calibration to transform confocal intensity images into concentration maps. The power of this approach is first illustrated with in vitro measurements using different dye solutions, then its applicability for in vivo measurements is demonstrated in Drosophila embryos for a model nuclear protein and for two morphogens, Bicoid and Capicua.
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Affiliation(s)
- Lili Zhang
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Carmina Perez-Romero
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada; Institut Curie, PSL University, CNRS, Paris, France; Nuclear Dynamics, Sorbonne University, Paris, France
| | - Nathalie Dostatni
- Institut Curie, PSL University, CNRS, Paris, France; Nuclear Dynamics, Sorbonne University, Paris, France
| | - Cécile Fradin
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
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30
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Shlemov A, Alexandrov T, Golyandina N, Holloway D, Baumgartner S, Spirov AV. Quantification reveals early dynamics in Drosophila maternal gradients. PLoS One 2021; 16:e0244701. [PMID: 34411119 PMCID: PMC8376041 DOI: 10.1371/journal.pone.0244701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 07/16/2021] [Indexed: 11/18/2022] Open
Abstract
The Bicoid (Bcd) protein is a primary determinant of early anterior-posterior (AP) axis specification in Drosophila embryogenesis. This morphogen is spatially distributed in an anterior-high gradient, and affects particular AP cell fates in a concentration-dependent manner. The early distribution and dynamics of the bicoid (bcd) mRNA, the source for the Bcd protein gradient, is not well understood, leaving a number of open questions for how Bcd positional information develops and is regulated. Confocal microscope images of whole early embryos, stained for bcd mRNA or the Staufen (Stau) protein involved in its transport, were processed to extract quantitative AP intensity profiles at two depths (apical-under the embryo surface but above the nuclear layer; and basal-below the nuclei). Each profile was quantified by a two- (or three-) exponential equation. The parameters of these equations were used to analyze the early developmental dynamics of bcd. Analysis of 1D profiles was compared with 2D intensity surfaces from the same images. This approach reveals strong early changes in bcd and Stau, which appear to be coordinated. We can unambiguously discriminate three stages in early development using the exponential parameters: pre-blastoderm (1-9 cleavage cycle, cc), syncytial blastoderm (10-13 cc) and cellularization (from 14A cc). Key features which differ in this period are how fast the first exponential (anterior component) of the apical profile drops with distance and whether it is higher or lower than the basal first exponential. We can further discriminate early and late embryos within the pre-blastoderm stage, depending on how quickly the anterior exponential drops. This relates to the posterior-wards spread of bcd in the first hour of development. Both bcd and Stau show several redistributions in the head cytoplasm, quite probably related to nuclear activity: first shifting inwards towards the core plasm, forming either protrusions (early pre-blastoderm) or round aggregations (early nuclear cleavage cycles, cc, 13 and 14), then moving to the embryo surface and spreading posteriorly. These movements are seen both with the 2D surface study and the 1D profile analysis. The continued spreading of bcd can be tracked from the time of nuclear layer formation (later pre-blastoderm) to the later syncytial blastoderm stages by the progressive loss of steepness of the apical anterior exponential (for both bcd and Stau). Finally, at the beginning of cc14 (cellularization stage) we see a distinctive flip from the basal anterior gradient being higher to the apical gradient being higher (for both bcd and Stau). Quantitative analysis reveals substantial (and correlated) bcd and Stau redistributions during early development, supporting that the distribution and dynamics of bcd mRNA are key factors in the formation and maintenance of the Bcd protein morphogenetic gradient. This analysis reveals the complex and dynamic nature of bcd redistribution, particularly in the head cytoplasm. These resemble observations in oogenesis; their role and significance have yet to be clarified. The observed co-localization during redistribution of bcd and Stau may indicate the involvement of active transport.
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Affiliation(s)
- Alex Shlemov
- Laboratory for Algorithmic Biology, St. Petersburg State University, St. Petersburg, Russia
| | - Theodore Alexandrov
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Nina Golyandina
- Faculty of Mathematics and Mechanics, St. Petersburg State University, St. Petersburg, Russia
| | - David Holloway
- Mathematics Department, British Columbia Institute of Technology, Burnaby, British Columbia, Canada
| | - Stefan Baumgartner
- Department of Experimental Medical Sciences, Lund University, Lund, Sweden
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Alexander V. Spirov
- Computer Science and CEWIT, SUNY Stony Brook, Stony Brook, New York, United States of America
- Lab Modelling Evolution, The I.M. Sechenov Institute of Evolutionary Physiology & Biochemistry, St. Petersburg, Russia
- * E-mail:
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31
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Cai X, Rondeel I, Baumgartner S. Modulating the bicoid gradient in space and time. Hereditas 2021; 158:29. [PMID: 34404481 PMCID: PMC8371787 DOI: 10.1186/s41065-021-00192-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 07/19/2021] [Indexed: 11/15/2022] Open
Abstract
Background The formation of the Bicoid (Bcd) gradient in the early Drosophila is one of the most fascinating observations in biology and serves as a paradigm for gradient formation, yet its mechanism is still not fully understood. Two distinct models were proposed in the past, the SDD and the ARTS model. Results We define novel cis- and trans-acting factors that are indispensable for gradient formation. The first one is the poly A tail length of the bcd mRNA where we demonstrate that it changes not only in time, but also in space. We show that posterior bcd mRNAs possess a longer poly tail than anterior ones and this elongation is likely mediated by wispy (wisp), a poly A polymerase. Consequently, modulating the activity of Wisp results in changes of the Bcd gradient, in controlling downstream targets such as the gap and pair-rule genes, and also in influencing the cuticular pattern. Attempts to modulate the Bcd gradient by subjecting the egg to an extra nuclear cycle, i.e. a 15th nuclear cycle by means of the maternal haploid (mh) mutation showed no effect, neither on the appearance of the gradient nor on the control of downstream target. This suggests that the segmental anlagen are determined during the first 14 nuclear cycles. Finally, we identify the Cyclin B (CycB) gene as a trans-acting factor that modulates the movement of Bcd such that Bcd movement is allowed to move through the interior of the egg. Conclusions Our analysis demonstrates that Bcd gradient formation is far more complex than previously thought requiring a revision of the models of how the gradient is formed.
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Affiliation(s)
- Xiaoli Cai
- Departmentof Experimental Medical Sciences, Lund University, BMC D10, 22184, Lund, Sweden
| | - Inge Rondeel
- Departmentof Experimental Medical Sciences, Lund University, BMC D10, 22184, Lund, Sweden.,Present address: Hubrecht Institute, 3584 CT, Utrecht, The Netherlands
| | - Stefan Baumgartner
- Departmentof Experimental Medical Sciences, Lund University, BMC D10, 22184, Lund, Sweden. .,Department of Biology, University of Konstanz, 78457, Konstanz, Germany.
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32
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Dutta S, Patel AL, Keenan SE, Shvartsman SY. From complex datasets to predictive models of embryonic development. NATURE COMPUTATIONAL SCIENCE 2021; 1:516-520. [PMID: 38217248 DOI: 10.1038/s43588-021-00110-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 07/12/2021] [Indexed: 01/15/2024]
Abstract
Modern studies of embryogenesis are increasingly quantitative, powered by rapid advances in imaging, sequencing and genome manipulation technologies. Deriving mechanistic insights from the complex datasets generated by these new tools requires systematic approaches for data-driven analysis of the underlying developmental processes. Here, we use data from our work on signal-dependent gene repression in the Drosophila embryo to illustrate how computational models can compactly summarize quantitative results of live imaging, chromatin immunoprecipitation and optogenetic perturbation experiments. The presented computational approach is ideally suited for integrating rapidly accumulating quantitative data and for guiding future studies of embryogenesis.
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Affiliation(s)
- Sayantan Dutta
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
- Lewis Sigler Institute of Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Aleena L Patel
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
- Lewis Sigler Institute of Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Shannon E Keenan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
- Lewis Sigler Institute of Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Stanislav Y Shvartsman
- Lewis Sigler Institute of Integrative Genomics, Princeton University, Princeton, NJ, USA.
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
- Center of Computational Biology, Flatiron Institute, New York, NY, USA.
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33
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The early Drosophila embryo as a model system for quantitative biology. Cells Dev 2021; 168:203722. [PMID: 34298230 DOI: 10.1016/j.cdev.2021.203722] [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: 03/05/2021] [Revised: 06/03/2021] [Accepted: 07/13/2021] [Indexed: 11/20/2022]
Abstract
With the rise of new tools, from controlled genetic manipulations and optogenetics to improved microscopy, it is now possible to make clear, quantitative and reproducible measurements of biological processes. The humble fruit fly Drosophila melanogaster, with its ease of genetic manipulation combined with excellent imaging accessibility, has become a major model system for performing quantitative in vivo measurements. Such measurements are driving a new wave of interest from physicists and engineers, who are developing a range of testable dynamic models of active systems to understand fundamental biological processes. The reproducibility of the early Drosophila embryo has been crucial for understanding how biological systems are robust to unavoidable noise during development. Insights from quantitative in vivo experiments in the Drosophila embryo are having an impact on our understanding of critical biological processes, such as how cells make decisions and how complex tissue shape emerges. Here, to highlight the power of using Drosophila embryogenesis for quantitative biology, I focus on three main areas: (1) formation and robustness of morphogen gradients; (2) how gene regulatory networks ensure precise boundary formation; and (3) how mechanical interactions drive packing and tissue folding. I further discuss how such data has driven advances in modelling.
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34
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Myasnikova EM, Sabirov MA, Spirov AV. Quantitative Analysis of the Dynamics of Maternal Gradients in the Early Drosophila Embryo. J Comput Biol 2021; 28:747-757. [PMID: 34152850 DOI: 10.1089/cmb.2020.0571] [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: 11/13/2022] Open
Abstract
Predetermination, formation, and maintenance of the primary morphogenetic gradient (bicoid, bcd) of the early Drosophila embryo involves many interrelated processes. Here we focus on the biological systems analysis of the bcd mRNA redistribution in an early embryo. The results of the quantitative analysis of experimental data, together with the results of their dynamic modeling, substantiate the role of active transport in the redistribution of the bcd mRNA. The role of the nonlinearity of degradation mechanisms in the mRNA pattern robustness is discussed.
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Affiliation(s)
- Ekaterina M Myasnikova
- Lab Modeling Evolution, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St-Petersburg, Russia.,Center for Advanced Studies, Peter the Great St. Petersburg Polytechnical University, St-Petersburg, Russia
| | - Marat A Sabirov
- Lab Modeling Evolution, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St-Petersburg, Russia
| | - Alexander V Spirov
- Lab Modeling Evolution, I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St-Petersburg, Russia
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35
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Modeling the role for nuclear import dynamics in the early embryonic cell cycle. Biophys J 2021; 120:4277-4286. [PMID: 34022240 DOI: 10.1016/j.bpj.2021.05.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 04/22/2021] [Accepted: 05/06/2021] [Indexed: 11/21/2022] Open
Abstract
Nuclear composition determines nuclear function. The early embryos of many species begin life with large pools of maternally provided components that become rapidly imported into an increasing number of nuclei as the cells undergo repeated cleavage divisions. Because early cell cycles are too fast for nuclei to achieve steady-state nucleocytoplasmic partitioning, the composition of cleavage stage nuclei is likely dominated by nuclear import. The end of the rapid cleavage stage and onset of major zygotic transcription, known as the mid-blastula transition (MBT), is controlled by the ratio of nuclei/cytoplasm, indicating that changes in nuclear composition likely mediate MBT timing. Here, we explore how different nuclear import regimes can affect protein accumulation in the nucleus in the early Drosophila embryo. We find that nuclear import differs dramatically for a general nuclear cargo (NLS (nuclear localization signal)-mRFP) and a proposed MBT regulator (histone H3). We show that nuclear import rates of NLS-mRFP in a given nucleus remain relatively unchanged throughout the cleavage cycles, whereas those of H3 halve with each cycle. We model these two distinct modes of nuclear import as "nucleus-limited" and "import-limited" and examine how the two different modes can contribute to different protein accumulation dynamics. Finally, we incorporate these distinct modes of nuclear import into a model for cell-cycle regulation at the MBT and find that the import-limited H3 dynamics contribute to increased robustness and allow for stepwise cell-cycle slowing at the MBT.
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36
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Abstract
Embryonic development is controlled by dynamic signaling systems that are translated into patterns of gene expression. Optogenetics has now been used to rescue genetic loss of Drosophila terminal patterning, bringing us a step closer to reconstruct morphogenesis synthetically.
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Affiliation(s)
- Stefano De Renzis
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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37
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Lenne PF, Munro E, Heemskerk I, Warmflash A, Bocanegra-Moreno L, Kishi K, Kicheva A, Long Y, Fruleux A, Boudaoud A, Saunders TE, Caldarelli P, Michaut A, Gros J, Maroudas-Sacks Y, Keren K, Hannezo E, Gartner ZJ, Stormo B, Gladfelter A, Rodrigues A, Shyer A, Minc N, Maître JL, Di Talia S, Khamaisi B, Sprinzak D, Tlili S. Roadmap for the multiscale coupling of biochemical and mechanical signals during development. Phys Biol 2021; 18. [PMID: 33276350 PMCID: PMC8380410 DOI: 10.1088/1478-3975/abd0db] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 12/04/2020] [Indexed: 12/12/2022]
Abstract
The way in which interactions between mechanics and biochemistry lead to the emergence of complex cell and tissue organization is an old question that has recently attracted renewed interest from biologists, physicists, mathematicians and computer scientists. Rapid advances in optical physics, microscopy and computational image analysis have greatly enhanced our ability to observe and quantify spatiotemporal patterns of signalling, force generation, deformation, and flow in living cells and tissues. Powerful new tools for genetic, biophysical and optogenetic manipulation are allowing us to perturb the underlying machinery that generates these patterns in increasingly sophisticated ways. Rapid advances in theory and computing have made it possible to construct predictive models that describe how cell and tissue organization and dynamics emerge from the local coupling of biochemistry and mechanics. Together, these advances have opened up a wealth of new opportunities to explore how mechanochemical patterning shapes organismal development. In this roadmap, we present a series of forward-looking case studies on mechanochemical patterning in development, written by scientists working at the interface between the physical and biological sciences, and covering a wide range of spatial and temporal scales, organisms, and modes of development. Together, these contributions highlight the many ways in which the dynamic coupling of mechanics and biochemistry shapes biological dynamics: from mechanoenzymes that sense force to tune their activity and motor output, to collectives of cells in tissues that flow and redistribute biochemical signals during development.
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Affiliation(s)
- Pierre-François Lenne
- Aix-Marseille University, CNRS, IBDM, Turing Center for Living Systems, Marseille, France
| | - Edwin Munro
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, United States of America
| | - Idse Heemskerk
- Department of Cell & Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, United States of America
| | - Aryeh Warmflash
- Department of Biosciences and Bioengineering, Rice University, Houston, TX, 77005, United States of America
| | | | - Kasumi Kishi
- IST Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Anna Kicheva
- IST Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Yuchen Long
- Reproduction et Dévelopement des Plantes, Université de Lyon, École normale supérieure de Lyon, Université Claude Bernard Lyon 1, INRAe, CNRS, 69364 Lyon Cedex 07, France
| | - Antoine Fruleux
- Reproduction et Dévelopement des Plantes, Université de Lyon, École normale supérieure de Lyon, Université Claude Bernard Lyon 1, INRAe, CNRS, 69364 Lyon Cedex 07, France.,LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Arezki Boudaoud
- Reproduction et Dévelopement des Plantes, Université de Lyon, École normale supérieure de Lyon, Université Claude Bernard Lyon 1, INRAe, CNRS, 69364 Lyon Cedex 07, France.,LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Timothy E Saunders
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Paolo Caldarelli
- Cellule Pasteur UPMC, Sorbonne Université, rue du Dr Roux, 75015 Paris, France.,Department of Developmental and Stem Cell Biology Institut Pasteur, 75724 Paris, Cedex 15, France.,CNRS UMR3738, 75015 Paris, France
| | - Arthur Michaut
- Department of Developmental and Stem Cell Biology Institut Pasteur, 75724 Paris, Cedex 15, France.,CNRS UMR3738, 75015 Paris, France
| | - Jerome Gros
- Department of Developmental and Stem Cell Biology Institut Pasteur, 75724 Paris, Cedex 15, France.,CNRS UMR3738, 75015 Paris, France
| | - Yonit Maroudas-Sacks
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Kinneret Keren
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel.,Network Biology Research Laboratories and The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Edouard Hannezo
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Zev J Gartner
- Department of Pharmaceutical Chemistry, University of California, San Francisco, 600 16th St. Box 2280, San Francisco, CA 94158, United States of America
| | - Benjamin Stormo
- Department of Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 United States of America
| | - Amy Gladfelter
- Department of Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 United States of America
| | - Alan Rodrigues
- Laboratory of Morphogenesis, The Rockefeller University, 1230 York Avenue, New York, NY 10065, United States of America
| | - Amy Shyer
- Laboratory of Morphogenesis, The Rockefeller University, 1230 York Avenue, New York, NY 10065, United States of America
| | - Nicolas Minc
- Institut Jacques Monod, Université de Paris, CNRS UMR7592, 15 rue Hélène Brion, 75205 Paris Cedex 13, France
| | - Jean-Léon Maître
- Institut Curie, PSL Research University, Sorbonne Université, CNRS UMR3215, INSERM U934, Paris, France
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham NC 27710, United States of America
| | - Bassma Khamaisi
- School of Neurobiology, Biochemistry and Biophysics, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - David Sprinzak
- School of Neurobiology, Biochemistry and Biophysics, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Sham Tlili
- Aix-Marseille University, CNRS, IBDM, Turing Center for Living Systems, Marseille, France
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38
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Stapornwongkul KS, Vincent JP. Generation of extracellular morphogen gradients: the case for diffusion. Nat Rev Genet 2021; 22:393-411. [PMID: 33767424 DOI: 10.1038/s41576-021-00342-y] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2021] [Indexed: 02/07/2023]
Abstract
Cells within developing tissues rely on morphogens to assess positional information. Passive diffusion is the most parsimonious transport model for long-range morphogen gradient formation but does not, on its own, readily explain scaling, robustness and planar transport. Here, we argue that diffusion is sufficient to ensure robust morphogen gradient formation in a variety of tissues if the interactions between morphogens and their extracellular binders are considered. A current challenge is to assess how the affinity for extracellular binders, as well as other biophysical and cell biological parameters, determines gradient dynamics and shape in a diffusion-based transport system. Technological advances in genome editing, tissue engineering, live imaging and in vivo biophysics are now facilitating measurement of these parameters, paving the way for mathematical modelling and a quantitative understanding of morphogen gradient formation and modulation.
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39
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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.
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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
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40
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Johnson ME, Chen A, Faeder JR, Henning P, Moraru II, Meier-Schellersheim M, Murphy RF, Prüstel T, Theriot JA, Uhrmacher AM. Quantifying the roles of space and stochasticity in computer simulations for cell biology and cellular biochemistry. Mol Biol Cell 2021; 32:186-210. [PMID: 33237849 PMCID: PMC8120688 DOI: 10.1091/mbc.e20-08-0530] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/13/2020] [Accepted: 11/17/2020] [Indexed: 12/29/2022] Open
Abstract
Most of the fascinating phenomena studied in cell biology emerge from interactions among highly organized multimolecular structures embedded into complex and frequently dynamic cellular morphologies. For the exploration of such systems, computer simulation has proved to be an invaluable tool, and many researchers in this field have developed sophisticated computational models for application to specific cell biological questions. However, it is often difficult to reconcile conflicting computational results that use different approaches to describe the same phenomenon. To address this issue systematically, we have defined a series of computational test cases ranging from very simple to moderately complex, varying key features of dimensionality, reaction type, reaction speed, crowding, and cell size. We then quantified how explicit spatial and/or stochastic implementations alter outcomes, even when all methods use the same reaction network, rates, and concentrations. For simple cases, we generally find minor differences in solutions of the same problem. However, we observe increasing discordance as the effects of localization, dimensionality reduction, and irreversible enzymatic reactions are combined. We discuss the strengths and limitations of commonly used computational approaches for exploring cell biological questions and provide a framework for decision making by researchers developing new models. As computational power and speed continue to increase at a remarkable rate, the dream of a fully comprehensive computational model of a living cell may be drawing closer to reality, but our analysis demonstrates that it will be crucial to evaluate the accuracy of such models critically and systematically.
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Affiliation(s)
- M. E. Johnson
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD, 21218
| | - A. Chen
- Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD, 21218
| | - J. R. Faeder
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15260
| | - P. Henning
- Institute for Visual and Analytic Computing, University of Rostock, 18055 Rostock, Germany
| | - I. I. Moraru
- Department of Cell Biology, Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030
| | - M. Meier-Schellersheim
- Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - R. F. Murphy
- Computational Biology Department, Department of Biological Sciences, Department of Biomedical Engineering, Machine Learning Department, Carnegie Mellon University, Pittsburgh, PA 15289
| | - T. Prüstel
- Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - J. A. Theriot
- Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195
| | - A. M. Uhrmacher
- Institute for Visual and Analytic Computing, University of Rostock, 18055 Rostock, Germany
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41
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Mirth CK, Saunders TE, Amourda C. Growing Up in a Changing World: Environmental Regulation of Development in Insects. ANNUAL REVIEW OF ENTOMOLOGY 2021; 66:81-99. [PMID: 32822557 DOI: 10.1146/annurev-ento-041620-083838] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
All organisms are exposed to changes in their environment throughout their life cycle. When confronted with these changes, they adjust their development and physiology to ensure that they can produce the functional structures necessary for survival and reproduction. While some traits are remarkably invariant, or robust, across environmental conditions, others show high degrees of variation, known as plasticity. Generally, developmental processes that establish cell identity are thought to be robust to environmental perturbation, while those relating to body and organ growth show greater degrees of plasticity. However, examples of plastic patterning and robust organ growth demonstrate that this is not a hard-and-fast rule.In this review, we explore how the developmental context and the gene regulatory mechanisms underlying trait formation determine the impacts of the environment on development in insects. Furthermore, we outline future issues that need to be resolved to understand how the structure of signaling networks defines whether a trait displays plasticity or robustness.
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Affiliation(s)
- Christen K Mirth
- School of Biological Sciences, Monash University, Melbourne 3800, Victoria, Australia;
| | - Timothy E Saunders
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore
- Department of Biological Sciences, National University of Singapore, Singapore 117588, Republic of Singapore
- Institute of Molecular and Cell Biology, A*Star, Proteos, Singapore 138673, Republic of Singapore
| | - Christopher Amourda
- MRC London Institute of Medical Sciences, Imperial College London, London W12 0NN, United Kingdom
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42
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Scaling a Dpp Morphogen Gradient through Feedback Control of Receptors and Co-receptors. Dev Cell 2021; 53:724-739.e14. [PMID: 32574592 DOI: 10.1016/j.devcel.2020.05.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 03/23/2020] [Accepted: 05/26/2020] [Indexed: 11/21/2022]
Abstract
Gradients of decapentaplegic (Dpp) pattern Drosophila wing imaginal discs, establishing gene expression boundaries at specific locations. As discs grow, Dpp gradients expand, keeping relative boundary positions approximately stationary. Such scaling fails in mutants for Pentagone (pent), a gene repressed by Dpp that encodes a diffusible protein that expands Dpp gradients. Although these properties fit a recent mathematical model of automatic gradient scaling, that model requires an expander that spreads with minimal loss throughout a morphogen field. Here, we show that Pent's actions are confined to within just a few cell diameters of its site of synthesis and can be phenocopied by manipulating non-diffusible Pent targets strictly within the Pent expression domain. Using genetics and mathematical modeling, we develop an alternative model of scaling driven by feedback downregulation of Dpp receptors and co-receptors. Among the model's predictions is a size beyond which scaling fails-something we observe directly in wing discs.
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43
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Dawes ML, Soeller C, Scholpp S. Studying molecular interactions in the intact organism: fluorescence correlation spectroscopy in the living zebrafish embryo. Histochem Cell Biol 2020; 154:507-519. [PMID: 33067656 PMCID: PMC7609432 DOI: 10.1007/s00418-020-01930-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2020] [Indexed: 02/07/2023]
Abstract
Cell behaviour and function is determined through the interactions of a multitude of molecules working in concert. To observe these molecular dynamics, biophysical studies have been developed that track single interactions. Fluorescence correlation spectroscopy (FCS) is an optical biophysical technique that non-invasively resolves single molecules through recording the signal intensity at the femtolitre scale. However, recording the behaviour of these biomolecules using in vitro-based assays often fails to recapitulate the full range of variables in vivo that directly confer dynamics. Therefore, there has been an increasing interest in observing the state of these biomolecules within living organisms such as the zebrafish Danio rerio. In this review, we explore the advancements of FCS within the zebrafish and compare and contrast these findings to those found in vitro.
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Affiliation(s)
- Michael L Dawes
- Living Systems Institute, School of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QD, UK
| | - Christian Soeller
- Living Systems Institute, College of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QD, UK
| | - Steffen Scholpp
- Living Systems Institute, School of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QD, UK.
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44
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Eck E, Liu J, Kazemzadeh-Atoufi M, Ghoreishi S, Blythe SA, Garcia HG. Quantitative dissection of transcription in development yields evidence for transcription-factor-driven chromatin accessibility. eLife 2020; 9:e56429. [PMID: 33074101 PMCID: PMC7738189 DOI: 10.7554/elife.56429] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 10/16/2020] [Indexed: 12/28/2022] Open
Abstract
Thermodynamic models of gene regulation can predict transcriptional regulation in bacteria, but in eukaryotes, chromatin accessibility and energy expenditure may call for a different framework. Here, we systematically tested the predictive power of models of DNA accessibility based on the Monod-Wyman-Changeux (MWC) model of allostery, which posits that chromatin fluctuates between accessible and inaccessible states. We dissected the regulatory dynamics of hunchback by the activator Bicoid and the pioneer-like transcription factor Zelda in living Drosophila embryos and showed that no thermodynamic or non-equilibrium MWC model can recapitulate hunchback transcription. Therefore, we explored a model where DNA accessibility is not the result of thermal fluctuations but is catalyzed by Bicoid and Zelda, possibly through histone acetylation, and found that this model can predict hunchback dynamics. Thus, our theory-experiment dialogue uncovered potential molecular mechanisms of transcriptional regulatory dynamics, a key step toward reaching a predictive understanding of developmental decision-making.
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Affiliation(s)
- Elizabeth Eck
- Biophysics Graduate Group, University of California at BerkeleyBerkeleyUnited States
| | - Jonathan Liu
- Department of Physics, University of California at BerkeleyBerkeleyUnited States
| | | | - Sydney Ghoreishi
- Department of Molecular and Cell Biology, University of California at BerkeleyBerkeleyUnited States
| | - Shelby A Blythe
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States
| | - Hernan G Garcia
- Biophysics Graduate Group, University of California at BerkeleyBerkeleyUnited States
- Department of Physics, University of California at BerkeleyBerkeleyUnited States
- Department of Molecular and Cell Biology, University of California at BerkeleyBerkeleyUnited States
- Institute for Quantitative Biosciences-QB3, University of California at BerkeleyBerkeleyUnited States
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45
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Fancher S, Mugler A. Diffusion vs. direct transport in the precision of morphogen readout. eLife 2020; 9:58981. [PMID: 33051001 PMCID: PMC7641583 DOI: 10.7554/elife.58981] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 10/13/2020] [Indexed: 01/14/2023] Open
Abstract
Morphogen profiles allow cells to determine their position within a developing organism, but not all morphogen profiles form by the same mechanism. Here, we derive fundamental limits to the precision of morphogen concentration sensing for two canonical mechanisms: the diffusion of morphogen through extracellular space and the direct transport of morphogen from source cell to target cell, for example, via cytonemes. We find that direct transport establishes a morphogen profile without adding noise in the process. Despite this advantage, we find that for sufficiently large values of profile length, the diffusion mechanism is many times more precise due to a higher refresh rate of morphogen molecules. We predict a profile lengthscale below which direct transport is more precise, and above which diffusion is more precise. This prediction is supported by data from a wide variety of morphogens in developing Drosophila and zebrafish.
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Affiliation(s)
- Sean Fancher
- Department of Physics and Astronomy, Purdue University, West Lafayette, United States.,Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, United States
| | - Andrew Mugler
- Department of Physics and Astronomy, Purdue University, West Lafayette, United States.,Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, United States
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46
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Zhu H, Cui Y, Luo C, Liu F. Quantifying Temperature Compensation of Bicoid Gradients with a Fast T-Tunable Microfluidic Device. Biophys J 2020; 119:1193-1203. [PMID: 32853562 PMCID: PMC7499060 DOI: 10.1016/j.bpj.2020.08.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 08/02/2020] [Accepted: 08/04/2020] [Indexed: 10/23/2022] Open
Abstract
As a reaction-diffusion system strongly affected by temperature, early fly embryos surprisingly show highly reproducible and accurate developmental patterns during embryogenesis under temperature perturbations. To reveal the underlying temperature compensation mechanism, it is important to overcome the challenge in quantitative imaging on fly embryos under temperature perturbations. Inspired by microfluidics generating temperature steps on fly embryos, here we design a microfluidic device capable of ensuring the normal development of multiple fly embryos as well as achieving real-time temperature control and fast temperature switches for quantitative live imaging with a home-built two-photon microscope. We apply this system to quantify the temperature compensation of the morphogen Bicoid (Bcd) gradient in fly embryos. The length constant of the exponential Bcd gradient reaches the maximum at 25°C within the measured temperatures of 18-29°C and gradually adapts to the corresponding value at new temperatures upon a fast temperature switch. The relaxation time of such an adaptation becomes longer if the temperature is switched in a later developmental stage. This age-dependent temperature compensation could be explained if the traditional synthesis-diffusion-degradation model is extended to incorporate the dynamic change of the parameters controlling the formation of Bcd gradients.
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Affiliation(s)
- Hongcun Zhu
- State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China
| | - Yeping Cui
- State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China
| | - Chunxiong Luo
- Center for Quantitative Biology, Peking University, Beijing, China; The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing, China
| | - Feng Liu
- State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China; Center for Quantitative Biology, Peking University, Beijing, China.
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47
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Desponds J, Vergassola M, Walczak AM. A mechanism for hunchback promoters to readout morphogenetic positional information in less than a minute. eLife 2020; 9:49758. [PMID: 32723476 PMCID: PMC7428309 DOI: 10.7554/elife.49758] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 07/29/2020] [Indexed: 12/14/2022] Open
Abstract
Cell fate decisions in the fly embryo are rapid: hunchback genes decide in minutes whether nuclei follow the anterior/posterior developmental blueprint by reading out positional information in the Bicoid morphogen. This developmental system is a prototype of regulatory decision processes that combine speed and accuracy. Traditional arguments based on fixed-time sampling of Bicoid concentration indicate that an accurate readout is impossible within the experimental times. This raises the general issue of how speed-accuracy tradeoffs are achieved. Here, we compare fixed-time to on-the-fly decisions, based on comparing the likelihoods of anterior/posterior locations. We found that these more efficient schemes complete reliable cell fate decisions within the short embryological timescales. We discuss the influence of promoter architectures on decision times and error rates, present concrete examples that rapidly readout the morphogen, and predictions for new experiments. Lastly, we suggest a simple mechanism for RNA production and degradation that approximates the log-likelihood function.
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Affiliation(s)
- Jonathan Desponds
- Physics Department, University of California, San Diego, La Jolla, United States
| | - Massimo Vergassola
- Physics Department, University of California, San Diego, La Jolla, United States
| | - Aleksandra M Walczak
- Laboratoire de Physique, Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Paris, France
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48
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Zechner C, Nerli E, Norden C. Stochasticity and determinism in cell fate decisions. Development 2020; 147:147/14/dev181495. [PMID: 32669276 DOI: 10.1242/dev.181495] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
During development, cells need to make decisions about their fate in order to ensure that the correct numbers and types of cells are established at the correct time and place in the embryo. Such cell fate decisions are often classified as deterministic or stochastic. However, although these terms are clearly defined in a mathematical sense, they are sometimes used ambiguously in biological contexts. Here, we provide some suggestions on how to clarify the definitions and usage of the terms stochastic and deterministic in biological experiments. We discuss the frameworks within which such clear definitions make sense and highlight when certain ambiguity prevails. As an example, we examine how these terms are used in studies of neuronal cell fate decisions and point out areas in which definitions and interpretations have changed and matured over time. We hope that this Review will provide some clarification and inspire discussion on the use of terminology in relation to fate decisions.
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Affiliation(s)
- Christoph Zechner
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany .,Max Planck Center for Systems Biology, Pfotenhauerstraße 108, 01307 Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, 01062 Dresden, Germany
| | - Elisa Nerli
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Caren Norden
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany .,Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
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49
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Lasko P. Patterning the Drosophila embryo: A paradigm for RNA-based developmental genetic regulation. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 11:e1610. [PMID: 32543002 PMCID: PMC7583483 DOI: 10.1002/wrna.1610] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/13/2020] [Accepted: 05/17/2020] [Indexed: 12/16/2022]
Abstract
Embryonic anterior–posterior patterning is established in Drosophila melanogaster by maternally expressed genes. The mRNAs of several of these genes accumulate at either the anterior or posterior pole of the oocyte via a number of mechanisms. Many of these mRNAs are also under elaborate translational regulation. Asymmetric RNA localization coupled with spatially restricted translation ensures that their proteins are restricted to the position necessary for the developmental process that they drive. Bicoid (Bcd), the anterior determinant, and Oskar (Osk), the determinant for primordial germ cells and posterior patterning, have been studied particularly closely. In early embryos an anterior–posterior gradient of Bcd is established, activating transcription of different sets of zygotic genes depending on local Bcd concentration. At the posterior pole, Osk seeds formation of polar granules, ribonucleoprotein complexes that accumulate further mRNAs and proteins involved in posterior patterning and germ cell specification. After fertilization, polar granules associate with posterior nuclei and mature into nuclear germ granules. Osk accumulates in these granules, and either by itself or as part of the granules, stimulates germ cell division. This article is categorized under:RNA Export and Localization > RNA Localization Translation > Translation Regulation RNA in Disease and Development > RNA in Development
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Affiliation(s)
- Paul Lasko
- Department of Biology, McGill University, Montréal, Québec, Canada.,Department of Human Genetics, Radboudumc, Nijmegen, Netherlands
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50
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Yang Z, Zhu H, Kong K, Wu X, Chen J, Li P, Jiang J, Zhao J, Cui B, Liu F. The dynamic transmission of positional information in stau- mutants during Drosophila embryogenesis. eLife 2020; 9:e54276. [PMID: 32511091 PMCID: PMC7332292 DOI: 10.7554/elife.54276] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 06/06/2020] [Indexed: 01/04/2023] Open
Abstract
It has been suggested that Staufen (Stau) is key in controlling the variability of the posterior boundary of the Hb anterior domain (xHb). However, the mechanism that underlies this control is elusive. Here, we quantified the dynamic 3D expression of segmentation genes in Drosophila embryos. With improved control of measurement errors, we show that the xHb of stau- mutants reproducibly moves posteriorly by 10% of the embryo length (EL) to the wild type (WT) position in the nuclear cycle (nc) 14, and that its variability over short time windows is comparable to that of the WT. Moreover, for stau- mutants, the upstream Bicoid (Bcd) gradients show equivalent relative intensity noise to that of the WT in nc12-nc14, and the downstream Even-skipped (Eve) and cephalic furrow (CF) show the same positional errors as these factors in WT. Our results indicate that threshold-dependent activation and self-organized filtering are not mutually exclusive and could both be implemented in early Drosophila embryogenesis.
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Affiliation(s)
- Zhe Yang
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
- China National Center for Biotechnology DevelopmentBeijingChina
| | - Hongcun Zhu
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Kakit Kong
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Xiaoxuan Wu
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Jiayi Chen
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Peiyao Li
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Jialong Jiang
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Jinchao Zhao
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Bofei Cui
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
| | - Feng Liu
- State Key Laboratory of Nuclear Physics and Technology & Center for Quantitative Biology, Peking UniversityBeijingChina
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