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Bishop TR, Onal P, Xu Z, Zheng M, Gunasinghe H, Nien CY, Small S, Datta RR. Multi-level regulation of even-skipped stripes by the ubiquitous factor Zelda. Development 2023; 150:dev201860. [PMID: 37934130 PMCID: PMC10730019 DOI: 10.1242/dev.201860] [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: 04/08/2023] [Accepted: 10/26/2023] [Indexed: 11/08/2023]
Abstract
The zinc-finger protein Zelda (Zld) is a key activator of zygotic transcription in early Drosophila embryos. Here, we study Zld-dependent regulation of the seven-striped pattern of the pair-rule gene even-skipped (eve). Individual stripes are regulated by discrete enhancers that respond to broadly distributed activators; stripe boundaries are formed by localized repressors encoded by the gap genes. The strongest effects of Zld are on stripes 2, 3 and 7, which are regulated by two enhancers in a 3.8 kb genomic fragment that includes the eve basal promoter. We show that Zld facilitates binding of the activator Bicoid and the gap repressors to this fragment, consistent with its proposed role as a pioneer protein. To test whether the effects of Zld are direct, we mutated all canonical Zld sites in the 3.8 kb fragment, which reduced expression but failed to phenocopy the abolishment of stripes caused by removing Zld in trans. We show that Zld also indirectly regulates the eve stripes by establishing specific gap gene expression boundaries, which provides the embryonic spacing required for proper stripe activation.
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Affiliation(s)
- Timothy R. Bishop
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Pinar Onal
- Department of Molecular Biology and Genetics, Ihsan Dogramaci Bilkent University, Universiteler Mahallesi, 06800 Ankara, Turkey
| | - Zhe Xu
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Michael Zheng
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Himari Gunasinghe
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Chung-Yi Nien
- Department of Life Sciences, National Central University, Taoyuan 32001, Taiwan
| | - Stephen Small
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Rhea R. Datta
- Department of Biology, Hamilton College, 198 College Hill Rd., Clinton, NY 13323, USA
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2
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Brennan KJ, Weilert M, Krueger S, Pampari A, Liu HY, Yang AWH, Morrison JA, Hughes TR, Rushlow CA, Kundaje A, Zeitlinger J. Chromatin accessibility in the Drosophila embryo is determined by transcription factor pioneering and enhancer activation. Dev Cell 2023; 58:1898-1916.e9. [PMID: 37557175 PMCID: PMC10592203 DOI: 10.1016/j.devcel.2023.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 05/09/2023] [Accepted: 07/13/2023] [Indexed: 08/11/2023]
Abstract
Chromatin accessibility is integral to the process by which transcription factors (TFs) read out cis-regulatory DNA sequences, but it is difficult to differentiate between TFs that drive accessibility and those that do not. Deep learning models that learn complex sequence rules provide an unprecedented opportunity to dissect this problem. Using zygotic genome activation in Drosophila as a model, we analyzed high-resolution TF binding and chromatin accessibility data with interpretable deep learning and performed genetic validation experiments. We identify a hierarchical relationship between the pioneer TF Zelda and the TFs involved in axis patterning. Zelda consistently pioneers chromatin accessibility proportional to motif affinity, whereas patterning TFs augment chromatin accessibility in sequence contexts where they mediate enhancer activation. We conclude that chromatin accessibility occurs in two tiers: one through pioneering, which makes enhancers accessible but not necessarily active, and the second when the correct combination of TFs leads to enhancer activation.
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Affiliation(s)
- Kaelan J Brennan
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Melanie Weilert
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Sabrina Krueger
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Anusri Pampari
- Department of Computer Science, Stanford University, Palo Alto, CA 94305, USA
| | - Hsiao-Yun Liu
- Department of Biology, New York University, New York, NY 10003, USA
| | - Ally W H Yang
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Jason A Morrison
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Timothy R Hughes
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | | | - Anshul Kundaje
- Department of Computer Science, Stanford University, Palo Alto, CA 94305, USA; Department of Genetics, Stanford University, Palo Alto, CA 94305, USA
| | - Julia Zeitlinger
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Pathology & Laboratory Medicine, The University of Kansas Medical Center, Kansas City, KS 66160, USA.
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3
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Albright AR, Angeles-Albores D, Marshall W. Genome-wide analysis of anterior-posterior mRNA localization in Stentor coeruleus reveals a role for the microtubule cytoskeleton. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.09.523364. [PMID: 36711710 PMCID: PMC9882060 DOI: 10.1101/2023.01.09.523364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Cells have complex and beautiful structures that are important for their function, but understanding the molecular mechanisms that produce these structures is a challenging problem due to the gap in size scales between molecular interactions and cellular structures. The giant ciliate Stentor coeruleus is a unicellular model organism whose large size, reproducible structure, and ability to heal wounds and regenerate has historically allowed the formation of structure in a single cell to be addressed using methods of experimental embryology. Such studies have shown that specific cellular structures, such as the oral apparatus, always form in specific regions of the cell, which raises the question: what is the source of positional information within this organism? By analogy with embryonic development, in which localized mRNA is often used to mark position, we asked whether position along the anterior-posterior axis of Stentor might be marked by specific regionalized mRNAs. By physically bisecting cells and conducting half-cell RNA sequencing, we were able to identify sets of messages enriched in either the anterior or posterior half. We repeated this analysis in cells in which a set of longitudinal microtubule bundles running down the whole length of the cell, known as KM-fibers, were disrupted by RNAi of b-tubulin. We found that many messages either lost their regionalized distribution or switched to an opposite distribution, such that anterior-enriched messages in control became posterior-enriched in the RNAi cells, or vice versa. This study indicates that mRNA can be regionalized within a single giant cell and that microtubules may play a role, possibly by serving as tracks for the movement of the messages.
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Affiliation(s)
- Ashley R. Albright
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Center for Cellular Construction, University of California, San Francisco, San Francisco, CA, USA
| | | | - Wallace Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Center for Cellular Construction, University of California, San Francisco, San Francisco, CA, USA
- Twitter: @WallaceUCSF
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4
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Zhu H, Shen W, Luo C, Liu F. An integrated microfluidic device for multiplexed imaging of spatial gene expression patterns of Drosophila embryos. LAB ON A CHIP 2022; 22:4081-4092. [PMID: 36165088 DOI: 10.1039/d2lc00514j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
To reveal the underlying mechanism of the biological function of multicellular systems, it is important to obtain comprehensive spatial gene expression profiles. Among the emerging single-cell spatial-omics techniques, immunofluorescence (IF)-based iterative multiplexed imaging is a promising approach. However, the conventional method is usually costly, time-consuming, labor-intensive, and has low throughput. Moreover, it has yet to be demonstrated in intact multicellular organisms. Here, we developed an integrated microfluidic system to overcome these challenges for quantitatively measuring multiple protein profiles sequentially in situ in the same Drosophila embryo. We designed an array of hydrodynamic trapping sites to automatically capture over ten Drosophila embryos with orientation selectivity at more than 90% trapping rates. We also optimized the geometry of confinement and the on-chip IF protocol to achieve the same high signal-to-noise ratio as the off-chip traditional IF experiments. Moreover, we developed an efficient de-staining protocol by combining on-chip antibody stripping and fluorophore bleaching. Using the same secondary antibody to sequentially stain different genes, we confirmed that the de-stained genes have no detectable interference with the subsequently stained genes, and the gene expression profiles are preserved after multiple cycles of staining and de-staining processes. This preliminary test shows that our newly developed integrated microfluidic system can be a powerful tool for multiplexed imaging of Drosophila embryos. Our work opens a new avenue to design microfluidic chips for multicellular organisms and single-cell spatial-omics techniques.
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Affiliation(s)
- Hongcun Zhu
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China.
| | - Wenting Shen
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.
| | - Chunxiong Luo
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China.
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.
- Wenzhou Institute University of Chinese Academy of Sciences, Wenzhou, Zhejiang, China
| | - Feng Liu
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.
- Key Laboratory of Hebei Province for Molecular Biophysics, Institute of Biophysics, School of Health Science & Biomedical Engineering, Hebei University of Technology, Tianjin, 300130, China
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Single-nucleus RNA-sequencing in pre-cellularization Drosophila melanogaster embryos. PLoS One 2022; 17:e0270471. [PMID: 35749552 PMCID: PMC9232161 DOI: 10.1371/journal.pone.0270471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 06/10/2022] [Indexed: 12/13/2022] Open
Abstract
Our current understanding of the regulation of gene expression in the early Drosophila melanogaster embryo comes from observations of a few genes at a time, as with in situ hybridizations, or observation of gene expression levels without regards to patterning, as with RNA-sequencing. Single-nucleus RNA-sequencing however, has the potential to provide new insights into the regulation of gene expression for many genes at once while simultaneously retaining information regarding the position of each nucleus prior to dissociation based on patterned gene expression. In order to establish the use of single-nucleus RNA sequencing in Drosophila embryos prior to cellularization, here we look at gene expression in control and insulator protein, dCTCF, maternal null embryos during zygotic genome activation at nuclear cycle 14. We find that early embryonic nuclei can be grouped into distinct clusters according to gene expression. From both virtual and published in situ hybridizations, we also find that these clusters correspond to spatial regions of the embryo. Lastly, we provide a resource of candidate differentially expressed genes that might show local changes in gene expression between control and maternal dCTCF null nuclei with no detectable differential expression in bulk. These results highlight the potential for single-nucleus RNA-sequencing to reveal new insights into the regulation of gene expression in the early Drosophila melanogaster embryo.
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6
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Taliaferro JM. Transcriptome-scale methods for uncovering subcellular RNA localization mechanisms. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119202. [PMID: 34998919 PMCID: PMC9035289 DOI: 10.1016/j.bbamcr.2021.119202] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 12/03/2021] [Accepted: 12/17/2021] [Indexed: 12/21/2022]
Abstract
Across a variety of systems, thousands of RNAs are localized to specific subcellular locations. However, for the vast majority of these RNAs, the mechanisms that underlie their transport are unknown. Historically, these mechanisms were uncovered for a single transcript at a time by laboriously testing the ability of RNA fragments to direct transcript localization. Recently developed methods profile the content of subcellular transcriptomes using high-throughput sequencing, allowing the analysis of the localization of thousands of transcripts at once. By identifying commonalities shared among multiple localized transcripts, these methods have the potential to rapidly expand our understanding of RNA localization mechanisms.
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Affiliation(s)
- J Matthew Taliaferro
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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7
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Mayeur H, Lanoizelet M, Quillien A, Menuet A, Michel L, Martin KJ, Dejean S, Blader P, Mazan S, Lagadec R. When Bigger Is Better: 3D RNA Profiling of the Developing Head in the Catshark Scyliorhinus canicula. Front Cell Dev Biol 2021; 9:744982. [PMID: 34746140 PMCID: PMC8569936 DOI: 10.3389/fcell.2021.744982] [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: 07/21/2021] [Accepted: 09/28/2021] [Indexed: 11/13/2022] Open
Abstract
We report the adaptation of RNA tomography, a technique allowing spatially resolved, genome-wide expression profiling, to a species occupying a key phylogenetic position in gnathostomes, the catshark Scyliorhinus canicula. We focused analysis on head explants at an embryonic stage, shortly following neural tube closure and of interest for a number of developmental processes, including early brain patterning, placode specification or the establishment of epithalamic asymmetry. As described in the zebrafish, we have sequenced RNAs extracted from serial sections along transverse, horizontal and sagittal planes, mapped the data onto a gene reference taking advantage of the high continuity genome recently released in the catshark, and projected read counts onto a digital model of the head obtained by confocal microscopy. This results in the generation of a genome-wide 3D atlas, containing expression data for most protein-coding genes in a digital model of the embryonic head. The digital profiles obtained for candidate forebrain regional markers along antero-posterior, dorso-ventral and left-right axes reproduce those obtained by in situ hybridization (ISH), with expected relative organizations. We also use spatial autocorrelation and correlation as measures to analyze these data and show that they provide adequate statistical tools to extract novel expression information from the model. These data and tools allow exhaustive searches of genes exhibiting any predefined expression characteristic, such a restriction to a territory of interest, thus providing a reference for comparative analyses across gnathostomes. This methodology appears best suited to species endowed with large embryo or organ sizes and opens novel perspectives to a wide range of evo-devo model organisms, traditionally counter-selected on size criterion.
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Affiliation(s)
- Hélène Mayeur
- CNRS, Sorbonne Université, UMR 7232-Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls sur Mer, France
| | - Maxence Lanoizelet
- CNRS, Sorbonne Université, UMR 7232-Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls sur Mer, France
| | - Aurélie Quillien
- Molecular, Cellular and Developmental Biology (MCD UMR 5077), Centre de Biologie Intégrative (CBI, FR 3743), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Arnaud Menuet
- UMR 7355, Experimental and Molecular Immunology and Neurogenetics, CNRS and University of Orléans, Orléans, France
| | - Léo Michel
- CNRS, Sorbonne Université, UMR 7232-Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls sur Mer, France
| | - Kyle John Martin
- United Kingdom Research and Innovation, Biotechnology and Biological Sciences Research Council, Swindon, United Kingdom
| | - Sébastien Dejean
- Institut de Mathématiques de Toulouse, Université de Toulouse, CNRS, UPS, UMR 5219, Toulouse, France
| | - Patrick Blader
- Molecular, Cellular and Developmental Biology (MCD UMR 5077), Centre de Biologie Intégrative (CBI, FR 3743), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Sylvie Mazan
- CNRS, Sorbonne Université, UMR 7232-Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls sur Mer, France
| | - Ronan Lagadec
- CNRS, Sorbonne Université, UMR 7232-Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, Banyuls sur Mer, France
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8
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Liu J, Hansen D, Eck E, Kim YJ, Turner M, Alamos S, Garcia HG. Real-time single-cell characterization of the eukaryotic transcription cycle reveals correlations between RNA initiation, elongation, and cleavage. PLoS Comput Biol 2021; 17:e1008999. [PMID: 34003867 PMCID: PMC8162642 DOI: 10.1371/journal.pcbi.1008999] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 05/28/2021] [Accepted: 04/23/2021] [Indexed: 12/23/2022] Open
Abstract
The eukaryotic transcription cycle consists of three main steps: initiation, elongation, and cleavage of the nascent RNA transcript. Although each of these steps can be regulated as well as coupled with each other, their in vivo dissection has remained challenging because available experimental readouts lack sufficient spatiotemporal resolution to separate the contributions from each of these steps. Here, we describe a novel application of Bayesian inference techniques to simultaneously infer the effective parameters of the transcription cycle in real time and at the single-cell level using a two-color MS2/PP7 reporter gene and the developing fruit fly embryo as a case study. Our method enables detailed investigations into cell-to-cell variability in transcription-cycle parameters as well as single-cell correlations between these parameters. These measurements, combined with theoretical modeling, suggest a substantial variability in the elongation rate of individual RNA polymerase molecules. We further illustrate the power of this technique by uncovering a novel mechanistic connection between RNA polymerase density and nascent RNA cleavage efficiency. Thus, our approach makes it possible to shed light on the regulatory mechanisms in play during each step of the transcription cycle in individual, living cells at high spatiotemporal resolution.
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Affiliation(s)
- Jonathan Liu
- Department of Physics, University of California at Berkeley, Berkeley, California, United States of America
| | - Donald Hansen
- Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, Heidelberg, Germany
| | - Elizabeth Eck
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Yang Joon Kim
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Meghan Turner
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
| | - Simon Alamos
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, California, United States of America
| | - Hernan G. Garcia
- Department of Physics, University of California at Berkeley, Berkeley, California, United States of America
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, United States of America
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, United States of America
- Institute for Quantitative Biosciences-QB3, University of California at Berkeley, Berkeley, California, United States of America
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9
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Waylen LN, Nim HT, Martelotto LG, Ramialison M. From whole-mount to single-cell spatial assessment of gene expression in 3D. Commun Biol 2020; 3:602. [PMID: 33097816 PMCID: PMC7584572 DOI: 10.1038/s42003-020-01341-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 09/10/2020] [Indexed: 12/31/2022] Open
Abstract
Unravelling spatio-temporal patterns of gene expression is crucial to understanding core biological principles from embryogenesis to disease. Here we review emerging technologies, providing automated, high-throughput, spatially resolved quantitative gene expression data. Novel techniques expand on current benchmark protocols, expediting their incorporation into ongoing research. These approaches digitally reconstruct patterns of embryonic expression in three dimensions, and have successfully identified novel domains of expression, cell types, and tissue features. Such technologies pave the way for unbiased and exhaustive recapitulation of gene expression levels in spatial and quantitative terms, promoting understanding of the molecular origin of developmental defects, and improving medical diagnostics.
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Affiliation(s)
- Lisa N Waylen
- Australian Regenerative Medicine Institute and Systems Biology Institute, Monash University, Clayton, VIC, Australia
| | - Hieu T Nim
- Australian Regenerative Medicine Institute and Systems Biology Institute, Monash University, Clayton, VIC, Australia
- Transcriptomics and Bioinformatics Group, Murdoch Children's Research Institute, Parkville, VIC, Australia
| | - Luciano G Martelotto
- Single Cell Core Laboratory, Harvard Medical School, Department of System Biology, Boston, MA, USA
| | - Mirana Ramialison
- Australian Regenerative Medicine Institute and Systems Biology Institute, Monash University, Clayton, VIC, Australia.
- Transcriptomics and Bioinformatics Group, Murdoch Children's Research Institute, Parkville, VIC, Australia.
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10
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Cai X, Fahmy K, Baumgartner S. bicoid RNA localization requires the trans-Golgi network. Hereditas 2019; 156:30. [PMID: 31528161 PMCID: PMC6737670 DOI: 10.1186/s41065-019-0106-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 08/26/2019] [Indexed: 11/10/2022] Open
Abstract
Background The formation of the bicoid (bcd) mRNA gradient is a crucial step for Bcd protein gradient formation in Drosophila. In the past, a microtubule (MT)-based cortical network had been shown to be indispensable for bcd mRNA transport to the posterior. Results We report the identification of a MT-binding protein CLASP/Chb as the first component associated with this cortical MT network. Since CLASPs in vertebrates were shown to serve as an acentriolar microtubule organization center (aMTOC) in concert with trans-Golgi proteins, we examined the effect of the Drosophila trans-Golgins on bcd localization and gradient formation. Using a genetic approach, we demonstrate that the Drosophila trans-Golgins dGCC88, dGolgin97 and dGCC185 indeed affect bcd mRNA localization during oocyte development. Consequently, the bcd mRNA is already mislocalized before the egg is fertilized. The expression domains of genes downstream of the hierarchy of bcd, e.g. of the gap gene empty spiracles or of the pair-rule gene even-skipped are changed, indicating an altered segmental anlagen, due to a faulty bcd gradient. Thus, at the end of embryogenesis, trans-Golgin mutants show bcd-like cuticle phenotypes. Conclusions Our data provides evidence that the Golgi as a cellular member of the secretory pathway exerts control on bcd localization which indicates that bcd gradient formation is probably more intricate than previously presumed.
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Affiliation(s)
- Xiaoli Cai
- 1Department of Experimental Medical Sciences, Lund University, BMC D10, S-22184 Lund, Sweden
| | - Khalid Fahmy
- 2Present Address: Department of Genetics, Ain Shams University, Cairo, Egypt
| | - Stefan Baumgartner
- 1Department of Experimental Medical Sciences, Lund University, BMC D10, S-22184 Lund, Sweden.,3Department of Biology, University of Konstanz, D-78457 Constance, Germany
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11
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Wunderlich Z, Fowlkes CC, Eckenrode KB, Bragdon MDJ, Abiri A, DePace AH. Quantitative Comparison of the Anterior-Posterior Patterning System in the Embryos of Five Drosophila Species. G3 (BETHESDA, MD.) 2019; 9:2171-2182. [PMID: 31048401 PMCID: PMC6643877 DOI: 10.1534/g3.118.200953] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 05/01/2019] [Indexed: 11/18/2022]
Abstract
Complex spatiotemporal gene expression patterns direct the development of the fertilized egg into an adult animal. Comparisons across species show that, in spite of changes in the underlying regulatory DNA sequence, developmental programs can be maintained across millions of years of evolution. Reciprocally, changes in gene expression can be used to generate morphological novelty. Distinguishing between changes in regulatory DNA that lead to changes in gene expression and those that do not is therefore a central goal of evolutionary developmental biology. Quantitative, spatially-resolved measurements of developmental gene expression patterns play a crucial role in this goal, enabling the detection of subtle phenotypic differences between species and the development of computations models that link the sequence of regulatory DNA to expression patterns. Here we report the generation of two atlases of cellular resolution gene expression measurements for the primary anterior-posterior patterning genes in Drosophila simulans and Drosophila virilis By combining these data sets with existing atlases for three other Drosophila species, we detect subtle differences in the gene expression patterns and dynamics driving the highly conserved axis patterning system and delineate inter-species differences in the embryonic morphology. These data sets will be a resource for future modeling studies of the evolution of developmental gene regulatory networks.
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Affiliation(s)
- Zeba Wunderlich
- Department of Developmental and Cell Biology, University of California, Irvine, CA, 92697
| | - Charless C Fowlkes
- Department of Computer Science, University of California, Irvine, CA, 92697
| | - Kelly B Eckenrode
- Department of Systems Biology, Harvard Medical School, Boston, MA, 20115
| | - Meghan D J Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, MA, 20115
| | - Arash Abiri
- Department of Developmental and Cell Biology, University of California, Irvine, CA, 92697
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA, 20115
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12
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Mir M, Stadler MR, Ortiz SA, Hannon CE, Harrison MM, Darzacq X, Eisen MB. Dynamic multifactor hubs interact transiently with sites of active transcription in Drosophila embryos. eLife 2018; 7:e40497. [PMID: 30589412 PMCID: PMC6307861 DOI: 10.7554/elife.40497] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/30/2018] [Indexed: 12/12/2022] Open
Abstract
The regulation of transcription requires the coordination of numerous activities on DNA, yet how transcription factors mediate these activities remains poorly understood. Here, we use lattice light-sheet microscopy to integrate single-molecule and high-speed 4D imaging in developing Drosophila embryos to study the nuclear organization and interactions of the key transcription factors Zelda and Bicoid. In contrast to previous studies suggesting stable, cooperative binding, we show that both factors interact with DNA with surprisingly high off-rates. We find that both factors form dynamic subnuclear hubs, and that Bicoid binding is enriched within Zelda hubs. Remarkably, these hubs are both short lived and interact only transiently with sites of active Bicoid-dependent transcription. Based on our observations, we hypothesize that, beyond simply forming bridges between DNA and the transcription machinery, transcription factors can organize other proteins into hubs that transiently drive multiple activities at their gene targets. Editorial note This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Mustafa Mir
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Michael R Stadler
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
- Howard Hughes Medical Institute, University of California, BerkeleyBerkeleyUnited States
| | - Stephan A Ortiz
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Colleen E Hannon
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Melissa M Harrison
- Department of Biomolecular ChemistryUniversity of Wisconsin–MadisonMadisonUnited States
| | - Xavier Darzacq
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Michael B Eisen
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
- Howard Hughes Medical Institute, University of California, BerkeleyBerkeleyUnited States
- Department of Integrative BiologyUniversity of California, BerkeleyBerkeleyUnited States
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Combs PA, Fraser HB. Spatially varying cis-regulatory divergence in Drosophila embryos elucidates cis-regulatory logic. PLoS Genet 2018; 14:e1007631. [PMID: 30383747 PMCID: PMC6211617 DOI: 10.1371/journal.pgen.1007631] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 08/14/2018] [Indexed: 12/30/2022] Open
Abstract
Spatial patterning of gene expression is a key process in development, yet how it evolves is still poorly understood. Both cis- and trans-acting changes could participate in complex interactions, so to isolate the cis-regulatory component of patterning evolution, we measured allele-specific spatial gene expression patterns in D. melanogaster × simulans hybrid embryos. RNA-seq of cryo-sectioned slices revealed 66 genes with strong spatially varying allele-specific expression. We found that hunchback, a major regulator of developmental patterning, had reduced expression of the D. simulans allele specifically in the anterior tip of hybrid embryos. Mathematical modeling of hunchback cis-regulation suggested a candidate transcription factor binding site variant, which we verified as causal using CRISPR-Cas9 genome editing. In sum, even comparing morphologically near-identical species we identified surprisingly extensive spatial variation in gene expression, suggesting not only that development is robust to many such changes, but also that natural selection may have ample raw material for evolving new body plans via changes in spatial patterning.
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Affiliation(s)
- Peter A. Combs
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Hunter B. Fraser
- Department of Biology, Stanford University, Stanford, California, United States of America
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14
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Veitia RA. Dosage effects in morphogenetic gradients of transcription factors: insights from a simple mathematical model. J Genet 2018; 97:365-370. [PMID: 29932055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The classical Hill equation is the simplest way to model sharp transcriptional responses (TR) to changing concentrations of a regulator. Such steep sigmoidal transitions of the TR are often involved in the creation of boundaries or domains during development. Here, I use the Hill function to explore the response of a promoter to a gradient of a transcription factor (TF). Specifically, I examine how various sources of nonlinearity (such as that imposed by the number of TF-binding sites) and the nonlinearity of the gradient itself influence TR and modulate its robustness to variations in the dosage of morphogen. This qualitative analysis underscores how nonlinearities can modulate the robustness of TR and is a convenient way to convey concepts in a teaching setting.
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Affiliation(s)
- Reiner A Veitia
- Institut Jacques Monod, Université Paris-Diderot, 75013 Paris, France.
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15
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Veitia RA. Dosage effects in morphogenetic gradients of transcription factors: insights from a simple mathematical model. J Genet 2018. [DOI: 10.1007/s12041-018-0920-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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16
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Haines JE, Eisen MB. Patterns of chromatin accessibility along the anterior-posterior axis in the early Drosophila embryo. PLoS Genet 2018; 14:e1007367. [PMID: 29727464 PMCID: PMC5955596 DOI: 10.1371/journal.pgen.1007367] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 05/16/2018] [Accepted: 04/17/2018] [Indexed: 12/20/2022] Open
Abstract
As the Drosophila embryo transitions from the use of maternal RNAs to zygotic transcription, domains of open chromatin, with relatively low nucleosome density and specific histone marks, are established at promoters and enhancers involved in patterned embryonic transcription. However it remains unclear how regions of activity are established during early embryogenesis, and if they are the product of spatially restricted or ubiquitous processes. To shed light on this question, we probed chromatin accessibility across the anterior-posterior axis (A-P) of early Drosophila melanogaster embryos by applying a transposon based assay for chromatin accessibility (ATAC-seq) to anterior and posterior halves of hand-dissected, cellular blastoderm embryos. We find that genome-wide chromatin accessibility is highly similar between the two halves, with regions that manifest significant accessibility in one half of the embryo almost always accessible in the other half, even for promoters that are active in exclusively one half of the embryo. These data support previous studies that show that chromatin accessibility is not a direct result of activity, and point to a role for ubiquitous factors or processes in establishing chromatin accessibility at promoters in the early embryo. However, in concordance with similar works, we find that at enhancers active exclusively in one half of the embryo, we observe a significant skew towards greater accessibility in the region of their activity, highlighting the role of patterning factors such as Bicoid in this process.
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Affiliation(s)
- Jenna E. Haines
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States of America
| | - Michael B. Eisen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States of America
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States of America
- Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States of America
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17
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Mir M, Reimer A, Haines JE, Li XY, Stadler M, Garcia H, Eisen MB, Darzacq X. Dense Bicoid hubs accentuate binding along the morphogen gradient. Genes Dev 2017; 31:1784-1794. [PMID: 28982761 PMCID: PMC5666676 DOI: 10.1101/gad.305078.117] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Accepted: 09/06/2017] [Indexed: 11/24/2022]
Abstract
Morphogen gradients direct the spatial patterning of developing embryos; however, the mechanisms by which these gradients are interpreted remain elusive. Here we used lattice light-sheet microscopy to perform in vivo single-molecule imaging in early Drosophila melanogaster embryos of the transcription factor Bicoid that forms a gradient and initiates patterning along the anteroposterior axis. In contrast to canonical models, we observed that Bicoid binds to DNA with a rapid off rate throughout the embryo such that its average occupancy at target loci is on-rate-dependent. We further observed Bicoid forming transient "hubs" of locally high density that facilitate binding as factor levels drop, including in the posterior, where we observed Bicoid binding despite vanishingly low protein levels. We propose that localized modulation of transcription factor on rates via clustering provides a general mechanism to facilitate binding to low-affinity targets and that this may be a prevalent feature of other developmental transcription factors.
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Affiliation(s)
- Mustafa Mir
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Armando Reimer
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Jenna E Haines
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Xiao-Yong Li
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Michael Stadler
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Hernan Garcia
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, 94720, USA
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, 94720, USA
- Department of Physics, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Michael B Eisen
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, 94720, USA
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, California, 94720, USA
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, California, 94720, USA
- Department of Integrative Biology, University of California at Berkeley, Berkeley, California, 94720, USA
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, 94720, USA
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