1
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Berrocal A, Lammers NC, Garcia HG, Eisen MB. Unified bursting strategies in ectopic and endogenous even-skipped expression patterns. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.02.09.527927. [PMID: 36798351 PMCID: PMC9934701 DOI: 10.1101/2023.02.09.527927] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Transcription often occurs in bursts as gene promoters switch stochastically between active and inactive states. Enhancers can dictate transcriptional activity in animal development through the modulation of burst frequency, duration, or amplitude. Previous studies observed that different enhancers can achieve a wide range of transcriptional outputs through the same strategies of bursting control. For example, despite responding to different transcription factors, all even-skipped enhancers increase transcription by upregulating burst frequency and amplitude while burst duration remains largely constant. These shared bursting strategies suggest that a unified molecular mechanism constraints how enhancers modulate transcriptional output. Alternatively, different enhancers could have converged on the same bursting control strategy because of natural selection favoring one of these particular strategies. To distinguish between these two scenarios, we compared transcriptional bursting between endogenous and ectopic gene expression patterns. Because enhancers act under different regulatory inputs in ectopic patterns, dissimilar bursting control strategies between endogenous and ectopic patterns would suggest that enhancers adapted their bursting strategies to their trans-regulatory environment. Here, we generated ectopic even-skipped transcription patterns in fruit fly embryos and discovered that bursting strategies remain consistent in endogenous and ectopic even-skipped expression. These results provide evidence for a unified molecular mechanism shaping even-skipped bursting strategies and serve as a starting point to uncover the realm of strategies employed by other enhancers.
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Affiliation(s)
- Augusto Berrocal
- Department of Molecular & Cell Biology, University of California at Berkeley, Berkeley, CA, United States
- Current Address: Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, CA, United States
| | - Nicholas C Lammers
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, CA, United States
- Current Address: Department of Genome Sciences, University of Washington, Seattle, WA, United States
| | - Hernan G Garcia
- Department of Molecular & Cell Biology, University of California at Berkeley, Berkeley, CA, United States
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, CA, United States
- Department of Physics, University of California at Berkeley, Berkeley, CA, United States
- California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, United States
- Chan Zuckerberg Biohub–San Francisco, San Francisco, California, CA, United States
| | - Michael B Eisen
- Department of Molecular & Cell Biology, University of California at Berkeley, Berkeley, CA, United States
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, CA, United States
- California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA, United States
- Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA, United States
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2
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Sakaguchi S, Mizuno S, Okochi Y, Tanegashima C, Nishimura O, Uemura T, Kadota M, Naoki H, Kondo T. Single-cell transcriptome atlas of Drosophila gastrula 2.0. Cell Rep 2023:112707. [PMID: 37433294 DOI: 10.1016/j.celrep.2023.112707] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 03/27/2023] [Accepted: 06/13/2023] [Indexed: 07/13/2023] Open
Abstract
During development, positional information directs cells to specific fates, leading them to differentiate with their own transcriptomes and express specific behaviors and functions. However, the mechanisms underlying these processes in a genome-wide view remain ambiguous, partly because the single-cell transcriptomic data of early developing embryos containing accurate spatial and lineage information are still lacking. Here, we report a single-cell transcriptome atlas of Drosophila gastrulae, divided into 77 transcriptomically distinct clusters. We find that the expression profiles of plasma-membrane-related genes, but not those of transcription-factor genes, represent each germ layer, supporting the nonequivalent contribution of each transcription-factor mRNA level to effector gene expression profiles at the transcriptome level. We also reconstruct the spatial expression patterns of all genes at the single-cell stripe level as the smallest unit. This atlas is an important resource for the genome-wide understanding of the mechanisms by which genes cooperatively orchestrate Drosophila gastrulation.
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Affiliation(s)
- Shunta Sakaguchi
- Laboratory of Cell Recognition and Pattern Formation, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Sonoko Mizuno
- Laboratory of Cell Recognition and Pattern Formation, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yasushi Okochi
- Laboratory of Theoretical Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Chiharu Tanegashima
- Laboratory for Phyloinformatics, RIKEN Center for Biosystems Dynamics Research, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Osamu Nishimura
- Laboratory for Phyloinformatics, RIKEN Center for Biosystems Dynamics Research, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Tadashi Uemura
- Laboratory of Cell Recognition and Pattern Formation, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; Center for Living Systems Information Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Mitsutaka Kadota
- Laboratory for Phyloinformatics, RIKEN Center for Biosystems Dynamics Research, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Honda Naoki
- Laboratory of Theoretical Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; Laboratory of Data-driven Biology, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashihiroshima, Hiroshima 739-8511, Japan; Theoretical Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi 444-8585, Japan
| | - Takefumi Kondo
- Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; The Keihanshin Consortium for Fostering the Next Generation of Global Leaders in Research (K-CONNEX), Sakyo-ku, Kyoto 606-8501, Japan.
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3
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Xue Y, Krishnan A, Chahda JS, Schweickart RA, Sousa-Neves R, Mizutani CM. The epithelial polarity genes frazzled and GUK-holder adjust morphogen gradients to coordinate changes in cell position with cell fate specification. PLoS Biol 2023; 21:e3002021. [PMID: 36913435 PMCID: PMC10035841 DOI: 10.1371/journal.pbio.3002021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 03/23/2023] [Accepted: 02/03/2023] [Indexed: 03/14/2023] Open
Abstract
Morphogenetic gradients specify distinct cell populations within tissues. Originally, morphogens were conceived as substances that act on a static field of cells, yet cells usually move during development. Thus, the way cell fates are defined in moving cells remains a significant and largely unsolved problem. Here, we investigated this issue using spatial referencing of cells and 3D spatial statistics in the Drosophila blastoderm to reveal how cell density responds to morphogenetic activity. We show that the morphogen decapentaplegic (DPP) attracts cells towards its peak levels in the dorsal midline, whereas dorsal (DL) stalls them ventrally. We identified frazzled and GUK-holder as the downstream effectors regulated by these morphogens that constrict cells and provide the mechanical force necessary to draw cells dorsally. Surprisingly, GUKH and FRA modulate the DL and DPP gradient levels and this regulation creates a very precise mechanism of coordinating cell movement and fate specification.
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Affiliation(s)
- Yongqiang Xue
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Aravindan Krishnan
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Juan Sebastian Chahda
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Robert Allen Schweickart
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Rui Sousa-Neves
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Claudia Mieko Mizutani
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America
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4
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Clark E, Battistara M, Benton MA. A timer gene network is spatially regulated by the terminal system in the Drosophila embryo. eLife 2022; 11:e78902. [PMID: 36524728 PMCID: PMC10065802 DOI: 10.7554/elife.78902] [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: 03/23/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
In insect embryos, anteroposterior patterning is coordinated by the sequential expression of the 'timer' genes caudal, Dichaete, and odd-paired, whose expression dynamics correlate with the mode of segmentation. In Drosophila, the timer genes are expressed broadly across much of the blastoderm, which segments simultaneously, but their expression is delayed in a small 'tail' region, just anterior to the hindgut, which segments during germband extension. Specification of the tail and the hindgut depends on the terminal gap gene tailless, but beyond this the regulation of the timer genes is poorly understood. We used a combination of multiplexed imaging, mutant analysis, and gene network modelling to resolve the regulation of the timer genes, identifying 11 new regulatory interactions and clarifying the mechanism of posterior terminal patterning. We propose that a dynamic Tailless expression gradient modulates the intrinsic dynamics of a timer gene cross-regulatory module, delineating the tail region and delaying its developmental maturation.
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Affiliation(s)
- Erik Clark
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
- Department of Genetics, University of CambridgeCambridgeUnited Kingdom
| | - Margherita Battistara
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridgeUnited Kingdom
| | - Matthew A Benton
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Developmental Biology Unit, EMBLHeidelbergGermany
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5
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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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6
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Abstract
The function of many biological systems, such as embryos, liver lobules, intestinal villi, and tumors, depends on the spatial organization of their cells. In the past decade, high-throughput technologies have been developed to quantify gene expression in space, and computational methods have been developed that leverage spatial gene expression data to identify genes with spatial patterns and to delineate neighborhoods within tissues. To comprehensively document spatial gene expression technologies and data-analysis methods, we present a curated review of literature on spatial transcriptomics dating back to 1987, along with a thorough analysis of trends in the field, such as usage of experimental techniques, species, tissues studied, and computational approaches used. Our Review places current methods in a historical context, and we derive insights about the field that can guide current research strategies. A companion supplement offers a more detailed look at the technologies and methods analyzed: https://pachterlab.github.io/LP_2021/ .
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7
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Wu X, Kong K, Xiao W, Liu F. Attractive internuclear force drives the collective behavior of nuclear arrays in Drosophila embryos. PLoS Comput Biol 2021; 17:e1009605. [PMID: 34797833 PMCID: PMC8641897 DOI: 10.1371/journal.pcbi.1009605] [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: 01/14/2021] [Revised: 12/03/2021] [Accepted: 10/31/2021] [Indexed: 11/25/2022] Open
Abstract
The collective behavior of the nuclear array in Drosophila embryos during nuclear cycle (NC) 11 to NC14 is crucial in controlling cell size, establishing developmental patterns, and coordinating morphogenesis. After live imaging on Drosophila embryos with light sheet microscopy, we extract the nuclear trajectory, speed, and internuclear distance with an automatic nuclear tracing method. We find that the nuclear speed shows a period of standing waves along the anterior-posterior (AP) axis after each metaphase as the nuclei collectively migrate towards the embryo poles and partially move back. And the maximum nuclear speed dampens by 28-45% in the second half of the standing wave. Moreover, the nuclear density is 22-42% lower in the pole region than the middle of the embryo during the interphase of NC12-14. To find mechanical rules controlling the collective motion and packing patterns of the nuclear array, we use a deep neural network (DNN) to learn the underlying force field from data. We apply the learned spatiotemporal attractive force field in the simulations with a particle-based model. And the simulations recapitulate nearly all the observed characteristic collective behaviors of nuclear arrays in Drosophila embryos.
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Affiliation(s)
- Xiaoxuan Wu
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Kakit Kong
- State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China
| | - Wenlei Xiao
- School of Mechanical Engineering and Automation, Beihang University, Beijing, China
| | - Feng Liu
- Center for Quantitative Biology, Peking University, Beijing, China
- State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing, China
- Key Laboratory of Hebei Province for Molecular Biophysics, Institute of Biophysics, School of Health Science & Biomedical Engineering, Hebei University of Technology, Tianjin, China
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8
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Okochi Y, Sakaguchi S, Nakae K, Kondo T, Naoki H. Model-based prediction of spatial gene expression via generative linear mapping. Nat Commun 2021; 12:3731. [PMID: 34140477 PMCID: PMC8211835 DOI: 10.1038/s41467-021-24014-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 05/27/2021] [Indexed: 11/17/2022] Open
Abstract
Decoding spatial transcriptomes from single-cell RNA sequencing (scRNA-seq) data has become a fundamental technique for understanding multicellular systems; however, existing computational methods lack both accuracy and biological interpretability due to their model-free frameworks. Here, we introduce Perler, a model-based method to integrate scRNA-seq data with reference in situ hybridization (ISH) data. To calibrate differences between these datasets, we develop a biologically interpretable model that uses generative linear mapping based on a Gaussian mixture model using the Expectation–Maximization algorithm. Perler accurately predicts the spatial gene expression of Drosophila embryos, zebrafish embryos, mammalian liver, and mouse visual cortex from scRNA-seq data. Furthermore, the reconstructed transcriptomes do not over-fit the ISH data and preserved the timing information of the scRNA-seq data. These results demonstrate the generalizability of Perler for dataset integration, thereby providing a biologically interpretable framework for accurate reconstruction of spatial transcriptomes in any multicellular system. Single cell RNA-seq loses spatial information of gene expression in multicellular systems because tissue must be dissociated. Here, the authors show the spatial gene expression profiles can be both accurately and robustly reconstructed by a new computational method using a generative linear mapping, Perler.
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Affiliation(s)
- Yasushi Okochi
- Laboratory for Theoretical Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.,Faculty of Medicine, Kyoto University, Kyoto, Japan
| | - Shunta Sakaguchi
- Laboratory for Cell Recognition and Pattern Formation, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Ken Nakae
- Graduate School of Informatics, Kyoto Universityo, Kyoto, Japan
| | - Takefumi Kondo
- Laboratory for Cell Recognition and Pattern Formation, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.,The Keihanshin Consortium for Fostering the Next Generation of Global Leaders in Research (K-CONNEX), Kyoto, Japan
| | - Honda Naoki
- Laboratory for Theoretical Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan. .,Laboratory for Data-driven Biology, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan. .,Theoretical Biology Research Group, Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi, Japan.
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9
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Wang GT, Pan HY, Lang WH, Yu YD, Hsieh CH, Kuan YS. Three-dimensional multi-gene expression maps reveal cell fate changes associated with laterality reversal of zebrafish habenula. J Neurosci Res 2021; 99:1632-1645. [PMID: 33638209 DOI: 10.1002/jnr.24806] [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: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 11/09/2022]
Abstract
The conserved bilateral habenular nuclei (HA) in vertebrate diencephalon develop into compartmentalized structures containing neurons derived from different cell lineages. Despite extensive studies demonstrated that zebrafish larval HA display distinct left-right (L-R) asymmetry in gene expression and connectivity, the spatial gene expression domains were mainly obtained from two-dimensional (2D) snapshots of colorimetric RNA in situ hybridization staining which could not properly reflect different HA neuronal lineages constructed in three-dimension (3D). Combing the tyramide-based fluorescent mRNA in situ hybridization, confocal microscopy and customized imaging processing procedures, we have created spatial distribution maps of four genes for 4-day-old zebrafish and in sibling fish whose L-R asymmetry was spontaneously reversed. 3D volumetric analyses showed that ratios of cpd2, lov, ron, and nrp1a expression in L-R reversed HA were reversed according to the parapineal positions. However, the quantitative changes of gene expression in reversed larval brains do not mirror the gene expression level in the obverse larval brains. There were a total 87.78% increase in lov+ nrp1a+ and a total 12.45% decrease in lov+ ron+ double-positive neurons when the L-R asymmetry of HA was reversed. Thus, our volumetric analyses of the 3D maps indicate that changes of HA neuronal cell fates are associated with the reversal of HA laterality. These changes likely account for the behavior changes associated with HA laterality alterations.
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Affiliation(s)
- Guo-Tzau Wang
- National Center for High-Performance Computing, Hsinchu, Taiwan R.O.C
| | - He-Yen Pan
- Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan R.O.C
| | - Wei-Han Lang
- Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan R.O.C
| | - Yuan-Ding Yu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan R.O.C
| | - Chang-Huain Hsieh
- National Center for High-Performance Computing, Hsinchu, Taiwan R.O.C
| | - Yung-Shu Kuan
- Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan R.O.C.,Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan R.O.C.,Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan R.O.C.,Neuroscience Program, Academia Sinica, Taipei, Taiwan R.O.C
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10
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Berrocal A, Lammers NC, Garcia HG, Eisen MB. Kinetic sculpting of the seven stripes of the Drosophila even-skipped gene. eLife 2020; 9:61635. [PMID: 33300492 PMCID: PMC7864633 DOI: 10.7554/elife.61635] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 10/09/2020] [Indexed: 12/14/2022] Open
Abstract
We used live imaging to visualize the transcriptional dynamics of the Drosophila melanogaster even-skipped gene at single-cell and high-temporal resolution as its seven stripe expression pattern forms, and developed tools to characterize and visualize how transcriptional bursting varies over time and space. We find that despite being created by the independent activity of five enhancers, even-skipped stripes are sculpted by the same kinetic phenomena: a coupled increase of burst frequency and amplitude. By tracking the position and activity of individual nuclei, we show that stripe movement is driven by the exchange of bursting nuclei from the posterior to anterior stripe flanks. Our work provides a conceptual, theoretical and computational framework for dissecting pattern formation in space and time, and reveals how the coordinated transcriptional activity of individual nuclei shapes complex developmental patterns.
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Affiliation(s)
- Augusto Berrocal
- Department of Molecular & Cell Biology, University of California at Berkeley, Berkeley, United States
| | - Nicholas C Lammers
- Biophysics Graduate Group, University of California at Berkeley, Berkeley, United States
| | - Hernan G Garcia
- Department of Molecular & Cell Biology, University of California at Berkeley, Berkeley, United States.,Biophysics Graduate Group, University of California at Berkeley, Berkeley, United States.,Department of Physics, University of California at Berkeley, Berkeley, United States.,Institute for Quantitative Biosciences-QB3, University of California at Berkeley, Berkeley, United States
| | - Michael B Eisen
- Department of Molecular & Cell Biology, University of California at Berkeley, Berkeley, United States.,Biophysics Graduate Group, University of California at Berkeley, Berkeley, United States.,Institute for Quantitative Biosciences-QB3, University of California at Berkeley, Berkeley, United States.,Department of Integrative Biology, University of California at Berkeley, Berkeley, United States.,Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, United States
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11
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López-Rivera F, Foster Rhoades OK, Vincent BJ, Pym ECG, Bragdon MDJ, Estrada J, DePace AH, Wunderlich Z. A Mutation in the Drosophila melanogaster eve Stripe 2 Minimal Enhancer Is Buffered by Flanking Sequences. G3 (BETHESDA, MD.) 2020; 10:4473-4482. [PMID: 33037064 PMCID: PMC7718739 DOI: 10.1534/g3.120.401777] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 10/01/2020] [Indexed: 01/18/2023]
Abstract
Enhancers are DNA sequences composed of transcription factor binding sites that drive complex patterns of gene expression in space and time. Until recently, studying enhancers in their genomic context was technically challenging. Therefore, minimal enhancers, the shortest pieces of DNA that can drive an expression pattern that resembles a gene's endogenous pattern, are often used to study features of enhancer function. However, evidence suggests that some enhancers require sequences outside the minimal enhancer to maintain function under environmental perturbations. We hypothesized that these additional sequences also prevent misexpression caused by a transcription factor binding site mutation within a minimal enhancer. Using the Drosophila melanogastereven-skipped stripe 2 enhancer as a case study, we tested the effect of a Giant binding site mutation (gt-2) on the expression patterns driven by minimal and extended enhancer reporter constructs. We found that, in contrast to the misexpression caused by the gt-2 binding site deletion in the minimal enhancer, the same gt-2 binding site deletion in the extended enhancer did not have an effect on expression. The buffering of expression levels, but not expression pattern, is partially explained by an additional Giant binding site outside the minimal enhancer. Deleting the gt-2 binding site in the endogenous locus had no significant effect on stripe 2 expression. Our results indicate that rules derived from mutating enhancer reporter constructs may not represent what occurs in the endogenous context.
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Affiliation(s)
- Francheska López-Rivera
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
- GSAS Research Scholar Initiative, Harvard University, Cambridge, MA 02138
| | | | - Ben J Vincent
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Edward C G Pym
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | | | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
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12
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Zabihihesari A, Hilliker AJ, Rezai P. Fly-on-a-Chip: Microfluidics for Drosophila melanogaster Studies. Integr Biol (Camb) 2020; 11:425-443. [DOI: 10.1093/intbio/zyz037] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 10/21/2019] [Accepted: 10/26/2019] [Indexed: 12/16/2022]
Abstract
Abstract
The fruit fly or Drosophila melanogaster has been used as a promising model organism in genetics, developmental and behavioral studies as well as in the fields of neuroscience, pharmacology, and toxicology. Not only all the developmental stages of Drosophila, including embryonic, larval, and adulthood stages, have been used in experimental in vivo biology, but also the organs, tissues, and cells extracted from this model have found applications in in vitro assays. However, the manual manipulation, cellular investigation and behavioral phenotyping techniques utilized in conventional Drosophila-based in vivo and in vitro assays are mostly time-consuming, labor-intensive, and low in throughput. Moreover, stimulation of the organism with external biological, chemical, or physical signals requires precision in signal delivery, while quantification of neural and behavioral phenotypes necessitates optical and physical accessibility to Drosophila. Recently, microfluidic and lab-on-a-chip devices have emerged as powerful tools to overcome these challenges. This review paper demonstrates the role of microfluidic technology in Drosophila studies with a focus on both in vivo and in vitro investigations. The reviewed microfluidic devices are categorized based on their applications to various stages of Drosophila development. We have emphasized technologies that were utilized for tissue- and behavior-based investigations. Furthermore, the challenges and future directions in Drosophila-on-a-chip research, and its integration with other advanced technologies, will be discussed.
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Affiliation(s)
| | | | - Pouya Rezai
- Department of Mechanical Engineering, York University, Toronto, ON, Canada
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13
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Barr K, Reinitz J, Radulescu O. An in silico analysis of robust but fragile gene regulation links enhancer length to robustness. PLoS Comput Biol 2019; 15:e1007497. [PMID: 31730659 PMCID: PMC6881076 DOI: 10.1371/journal.pcbi.1007497] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 11/27/2019] [Accepted: 10/22/2019] [Indexed: 12/31/2022] Open
Abstract
Organisms must ensure that expression of genes is directed to the appropriate tissues at the correct times, while simultaneously ensuring that these gene regulatory systems are robust to perturbation. This idea is captured by a mathematical concept called r-robustness, which says that a system is robust to a perturbation in up to r - 1 randomly chosen parameters. r-robustness implies that the biological system has a small number of sensitive parameters and that this number can be used as a robustness measure. In this work we use this idea to investigate the robustness of gene regulation using a sequence level model of the Drosophila melanogaster gene even-skipped. We consider robustness with respect to mutations of the enhancer sequence and with respect to changes of the transcription factor concentrations. We find that gene regulation is r-robust with respect to mutations in the enhancer sequence and identify a number of sensitive nucleotides. In both natural and in silico predicted enhancers, the number of nucleotides that are sensitive to mutation correlates negatively with the length of the sequence, meaning that longer sequences are more robust. The exact degree of robustness obtained is dependent not only on DNA sequence, but also on the local concentration of regulatory factors. We find that gene regulation can be remarkably sensitive to changes in transcription factor concentrations at the boundaries of expression features, while it is robust to perturbation elsewhere.
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Affiliation(s)
- Kenneth Barr
- Department of Genetic Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - John Reinitz
- Departments of Statistics, Ecology & Evolution, Molecular Genetics & Cell Biology, University of Chicago, Chicago, Illinois, United States of America
| | - Ovidiu Radulescu
- LPHI UMR CNRS 5235, University of Montpellier, Montpellier, France
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14
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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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15
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Park J, Estrada J, Johnson G, Vincent BJ, Ricci-Tam C, Bragdon MDJ, Shulgina Y, Cha A, Wunderlich Z, Gunawardena J, DePace AH. Dissecting the sharp response of a canonical developmental enhancer reveals multiple sources of cooperativity. eLife 2019; 8:e41266. [PMID: 31223115 PMCID: PMC6588347 DOI: 10.7554/elife.41266] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 03/04/2019] [Indexed: 12/19/2022] Open
Abstract
Developmental enhancers integrate graded concentrations of transcription factors (TFs) to create sharp gene expression boundaries. Here we examine the hunchback P2 (HbP2) enhancer which drives a sharp expression pattern in the Drosophila blastoderm embryo in response to the transcriptional activator Bicoid (Bcd). We systematically interrogate cis and trans factors that influence the shape and position of expression driven by HbP2, and find that the prevailing model, based on pairwise cooperative binding of Bcd to HbP2 is not adequate. We demonstrate that other proteins, such as pioneer factors, Mediator and histone modifiers influence the shape and position of the HbP2 expression pattern. Comparing our results to theory reveals how higher-order cooperativity and energy expenditure impact boundary location and sharpness. Our results emphasize that the bacterial view of transcription regulation, where pairwise interactions between regulatory proteins dominate, must be reexamined in animals, where multiple molecular mechanisms collaborate to shape the gene regulatory function.
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Affiliation(s)
- Jeehae Park
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Javier Estrada
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Gemma Johnson
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Ben J Vincent
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Chiara Ricci-Tam
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Meghan DJ Bragdon
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | | | - Anna Cha
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Zeba Wunderlich
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | | | - Angela H DePace
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
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16
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Vincent BJ, Staller MV, Lopez-Rivera F, Bragdon MDJ, Pym ECG, Biette KM, Wunderlich Z, Harden TT, Estrada J, DePace AH. Hunchback is counter-repressed to regulate even-skipped stripe 2 expression in Drosophila embryos. PLoS Genet 2018; 14:e1007644. [PMID: 30192762 PMCID: PMC6145585 DOI: 10.1371/journal.pgen.1007644] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 09/19/2018] [Accepted: 08/17/2018] [Indexed: 01/18/2023] Open
Abstract
Hunchback is a bifunctional transcription factor that can activate and repress gene expression in Drosophila development. We investigated the regulatory DNA sequence features that control Hunchback function by perturbing enhancers for one of its target genes, even-skipped (eve). While Hunchback directly represses the eve stripe 3+7 enhancer, we found that in the eve stripe 2+7 enhancer, Hunchback repression is prevented by nearby sequences-this phenomenon is called counter-repression. We also found evidence that Caudal binding sites are responsible for counter-repression, and that this interaction may be a conserved feature of eve stripe 2 enhancers. Our results alter the textbook view of eve stripe 2 regulation wherein Hb is described as a direct activator. Instead, to generate stripe 2, Hunchback repression must be counteracted. We discuss how counter-repression may influence eve stripe 2 regulation and evolution.
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Affiliation(s)
- Ben J. Vincent
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Max V. Staller
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Francheska Lopez-Rivera
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Meghan D. J. Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Edward C. G. Pym
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kelly M. Biette
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Timothy T. Harden
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Angela H. DePace
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
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17
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Samee MAH, Lydiard-Martin T, Biette KM, Vincent BJ, Bragdon MD, Eckenrode KB, Wunderlich Z, Estrada J, Sinha S, DePace AH. Quantitative Measurement and Thermodynamic Modeling of Fused Enhancers Support a Two-Tiered Mechanism for Interpreting Regulatory DNA. Cell Rep 2018; 21:236-245. [PMID: 28978476 DOI: 10.1016/j.celrep.2017.09.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 07/30/2017] [Accepted: 09/08/2017] [Indexed: 02/07/2023] Open
Abstract
Computational models of enhancer function generally assume that transcription factors (TFs) exert their regulatory effects independently, modeling an enhancer as a "bag of sites." These models fail on endogenous loci that harbor multiple enhancers, and a "two-tier" model appears better suited: in each enhancer TFs work independently, and the total expression is a weighted sum of their expression readouts. Here, we test these two opposing views on how cis-regulatory information is integrated. We fused two Drosophila blastoderm enhancers, measured their readouts, and applied the above two models to these data. The two-tier mechanism better fits these readouts, suggesting that these fused enhancers comprise multiple independent modules, despite having sequence characteristics typical of single enhancers. We show that short-range TF-TF interactions are not sufficient to designate such modules, suggesting unknown underlying mechanisms. Our results underscore that mechanisms of how modules are defined and how their outputs are combined remain to be elucidated.
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Affiliation(s)
- Md Abul Hassan Samee
- Gladstone Institutes, University of California San Francisco, San Francisco, CA 94158, USA
| | - Tara Lydiard-Martin
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Kelly M Biette
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ben J Vincent
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Meghan D Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Kelly B Eckenrode
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Zeba Wunderlich
- Department of Developmental and Cell Biology, University of California, Irvine, CA 92697, USA
| | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Saurabh Sinha
- Department of Computer Science, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA; Carl R. Woese Institute of Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
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18
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Cornwell M, Vangala M, Taing L, Herbert Z, Köster J, Li B, Sun H, Li T, Zhang J, Qiu X, Pun M, Jeselsohn R, Brown M, Liu XS, Long HW. VIPER: Visualization Pipeline for RNA-seq, a Snakemake workflow for efficient and complete RNA-seq analysis. BMC Bioinformatics 2018; 19:135. [PMID: 29649993 PMCID: PMC5897949 DOI: 10.1186/s12859-018-2139-9] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 03/26/2018] [Indexed: 02/05/2023] Open
Abstract
Background RNA sequencing has become a ubiquitous technology used throughout life sciences as an effective method of measuring RNA abundance quantitatively in tissues and cells. The increase in use of RNA-seq technology has led to the continuous development of new tools for every step of analysis from alignment to downstream pathway analysis. However, effectively using these analysis tools in a scalable and reproducible way can be challenging, especially for non-experts. Results Using the workflow management system Snakemake we have developed a user friendly, fast, efficient, and comprehensive pipeline for RNA-seq analysis. VIPER (Visualization Pipeline for RNA-seq analysis) is an analysis workflow that combines some of the most popular tools to take RNA-seq analysis from raw sequencing data, through alignment and quality control, into downstream differential expression and pathway analysis. VIPER has been created in a modular fashion to allow for the rapid incorporation of new tools to expand the capabilities. This capacity has already been exploited to include very recently developed tools that explore immune infiltrate and T-cell CDR (Complementarity-Determining Regions) reconstruction abilities. The pipeline has been conveniently packaged such that minimal computational skills are required to download and install the dozens of software packages that VIPER uses. Conclusions VIPER is a comprehensive solution that performs most standard RNA-seq analyses quickly and effectively with a built-in capacity for customization and expansion. Electronic supplementary material The online version of this article (10.1186/s12859-018-2139-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- MacIntosh Cornwell
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Mahesh Vangala
- University of Massachusetts Medical School, Worcester, MA, 01655, USA
| | - Len Taing
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Zachary Herbert
- Molecular Biology Core Facilities, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Johannes Köster
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Institute of Human Genetics, University of Duisburg-Essen, Essen, Germany
| | - Bo Li
- Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute and Harvard School of Public Health, Boston, MA, 02215, USA
| | - Hanfei Sun
- Department of Bioinformatics, School of Life Sciences, Tongji University, Shanghai, 200092, China
| | - Taiwen Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jian Zhang
- Beijing Institute of Basic Medical Sciences, Beijing, China
| | - Xintao Qiu
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Matthew Pun
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Rinath Jeselsohn
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Myles Brown
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - X Shirley Liu
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute and Harvard School of Public Health, Boston, MA, 02215, USA
| | - Henry W Long
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA. .,Center for Functional Cancer Epigenetics, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.
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19
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Barr KA, Martinez C, Moran JR, Kim AR, Ramos AF, Reinitz J. Synthetic enhancer design by in silico compensatory evolution reveals flexibility and constraint in cis-regulation. BMC SYSTEMS BIOLOGY 2017; 11:116. [PMID: 29187214 PMCID: PMC5708098 DOI: 10.1186/s12918-017-0485-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 11/09/2017] [Indexed: 11/12/2022]
Abstract
BACKGROUND Models that incorporate specific chemical mechanisms have been successful in describing the activity of Drosophila developmental enhancers as a function of underlying transcription factor binding motifs. Despite this, the minimum set of mechanisms required to reconstruct an enhancer from its constituent parts is not known. Synthetic biology offers the potential to test the sufficiency of known mechanisms to describe the activity of enhancers, as well as to uncover constraints on the number, order, and spacing of motifs. RESULTS Using a functional model and in silico compensatory evolution, we generated putative synthetic even-skipped stripe 2 enhancers with varying degrees of similarity to the natural enhancer. These elements represent the evolutionary trajectories of the natural stripe 2 enhancer towards two synthetic enhancers designed ab initio. In the first trajectory, spatially regulated expression was maintained, even after more than a third of binding sites were lost. In the second, sequences with high similarity to the natural element did not drive expression, but a highly diverged sequence about half the length of the minimal stripe 2 enhancer drove ten times greater expression. Additionally, homotypic clusters of Zelda or Stat92E motifs, but not Bicoid, drove expression in developing embryos. CONCLUSIONS Here, we present a functional model of gene regulation to test the degree to which the known transcription factors and their interactions explain the activity of the Drosophila even-skipped stripe 2 enhancer. Initial success in the first trajectory showed that the gene regulation model explains much of the function of the stripe 2 enhancer. Cases where expression deviated from prediction indicates that undescribed factors likely act to modulate expression. We also showed that activation driven Bicoid and Hunchback is highly sensitive to spatial organization of binding motifs. In contrast, Zelda and Stat92E drive expression from simple homotypic clusters, suggesting that activation driven by these factors is less constrained. Collectively, the 40 sequences generated in this work provides a powerful training set for building future models of gene regulation.
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Affiliation(s)
- Kenneth A Barr
- Committee on Genetics, Genomics, and Systems Biology, University of Chicago, Zoology 111, 1101 E 57th St, Chicago, 60637, Illinois, USA.
- Department of Ecology and Evolution, The University of Chicago, Chicago, 60637, Illinois, USA.
| | - Carlos Martinez
- Department Biochemistry and Molecular Genetics, Northwestern University, Chicago, 60611, Illinois, USA
| | - Jennifer R Moran
- Department Human Genetics, The University of Chicago, Chicago, 60637, Illinois, USA
- Institute for Genomics & Systems Biology, The University of Chicago, Chicago, 60637, Illinois, USA
| | - Ah-Ram Kim
- School of Life Science, Handong Global University, Pohang, 37554, Gyeongbuk, South Korea
| | - Alexandre F Ramos
- Departamento de Radiologia - Faculdade de Medicina, Universidade de São Paulo & Instituto do Câncer do Estado de São Paulo, São Paulo, SP CEP, 05403-911, Brazil
- Escola de Artes, Ciências e Humanidades & Núcleo de Estudos Interdisciplinares em Sistemas Complexos, Universidade de São Paulo, Av. Arlindo Béttio, São Paulo, 1000 CEP 03828-000, SP, Brazil
| | - John Reinitz
- Committee on Genetics, Genomics, and Systems Biology, University of Chicago, Zoology 111, 1101 E 57th St, Chicago, 60637, Illinois, USA
- Department of Ecology and Evolution, The University of Chicago, Chicago, 60637, Illinois, USA
- Institute for Genomics & Systems Biology, The University of Chicago, Chicago, 60637, Illinois, USA
- Department Statistics, The University of Chicago, 5747 S. Ellis Avenue Jones 312, Chicago, 60637, IL, USA
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20
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Vincent BJ, Estrada J, DePace AH. The appeasement of Doug: a synthetic approach to enhancer biology. Integr Biol (Camb) 2016; 8:475-84. [DOI: 10.1039/c5ib00321k] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ben J. Vincent
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
| | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
| | - Angela H. DePace
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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21
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Hall HC, Fakhrzadeh A, Luengo Hendriks CL, Fischer U. Precision Automation of Cell Type Classification and Sub-Cellular Fluorescence Quantification from Laser Scanning Confocal Images. FRONTIERS IN PLANT SCIENCE 2016; 7:119. [PMID: 26904081 PMCID: PMC4746258 DOI: 10.3389/fpls.2016.00119] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Accepted: 01/22/2016] [Indexed: 05/05/2023]
Abstract
While novel whole-plant phenotyping technologies have been successfully implemented into functional genomics and breeding programs, the potential of automated phenotyping with cellular resolution is largely unexploited. Laser scanning confocal microscopy has the potential to close this gap by providing spatially highly resolved images containing anatomic as well as chemical information on a subcellular basis. However, in the absence of automated methods, the assessment of the spatial patterns and abundance of fluorescent markers with subcellular resolution is still largely qualitative and time-consuming. Recent advances in image acquisition and analysis, coupled with improvements in microprocessor performance, have brought such automated methods within reach, so that information from thousands of cells per image for hundreds of images may be derived in an experimentally convenient time-frame. Here, we present a MATLAB-based analytical pipeline to (1) segment radial plant organs into individual cells, (2) classify cells into cell type categories based upon Random Forest classification, (3) divide each cell into sub-regions, and (4) quantify fluorescence intensity to a subcellular degree of precision for a separate fluorescence channel. In this research advance, we demonstrate the precision of this analytical process for the relatively complex tissues of Arabidopsis hypocotyls at various stages of development. High speed and robustness make our approach suitable for phenotyping of large collections of stem-like material and other tissue types.
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Affiliation(s)
- Hardy C. Hall
- Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural SciencesUmeå, Sweden
- *Correspondence: Hardy C. Hall
| | | | | | - Urs Fischer
- Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural SciencesUmeå, Sweden
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22
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Wunderlich Z, Bragdon MDJ, Vincent BJ, White JA, Estrada J, DePace AH. Krüppel Expression Levels Are Maintained through Compensatory Evolution of Shadow Enhancers. Cell Rep 2015; 12:1740-7. [PMID: 26344774 PMCID: PMC4581983 DOI: 10.1016/j.celrep.2015.08.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 06/24/2015] [Accepted: 08/05/2015] [Indexed: 01/08/2023] Open
Abstract
Many developmental genes are controlled by shadow enhancers—pairs of enhancers that drive overlapping expression patterns. We hypothesized that compensatory evolution can maintain the total expression of a gene, while individual shadow enhancers diverge between species. To test this hypothesis, we analyzed expression driven by orthologous pairs of shadow enhancers from Drosophila melanogaster, Drosophila yakuba, and Drosophila pseudoobscura that control expression of Krüppel, a transcription factor that patterns the anterior-posterior axis of blastoderm embryos. We found that the expression driven by the pair of enhancers is conserved between these three species, but expression levels driven by the individual enhancers are not. Using sequence analysis and experimental perturbation, we show that each shadow enhancer is regulated by different transcription factors. These results support the hypothesis that compensatory evolution can occur between shadow enhancers, which has implications for mechanistic and evolutionary studies of gene regulation.
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Affiliation(s)
- Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Meghan D J Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ben J Vincent
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | | | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
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23
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Shaped singular spectrum analysis for quantifying gene expression, with application to the early Drosophila embryo. BIOMED RESEARCH INTERNATIONAL 2015; 2015:689745. [PMID: 25945341 PMCID: PMC4402483 DOI: 10.1155/2015/689745] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 09/10/2014] [Accepted: 09/10/2014] [Indexed: 11/17/2022]
Abstract
In recent years, with the development of automated microscopy technologies, the volume and complexity of image data on gene expression have increased tremendously. The only way to analyze quantitatively and comprehensively such biological data is by developing and applying new sophisticated mathematical approaches. Here, we present extensions of 2D singular spectrum analysis (2D-SSA) for application to 2D and 3D datasets of embryo images. These extensions, circular and shaped 2D-SSA, are applied to gene expression in the nuclear layer just under the surface of the Drosophila (fruit fly) embryo. We consider the commonly used cylindrical projection of the ellipsoidal Drosophila embryo. We demonstrate how circular and shaped versions of 2D-SSA help to decompose expression data into identifiable components (such as trend and noise), as well as separating signals from different genes. Detection and improvement of under- and overcorrection in multichannel imaging is addressed, as well as the extraction and analysis of 3D features in 3D gene expression patterns.
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24
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Staller MV, Fowlkes CC, Bragdon MDJ, Wunderlich Z, Estrada J, DePace AH. A gene expression atlas of a bicoid-depleted Drosophila embryo reveals early canalization of cell fate. Development 2015; 142:587-96. [PMID: 25605785 PMCID: PMC4302997 DOI: 10.1242/dev.117796] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 12/01/2014] [Indexed: 01/31/2023]
Abstract
In developing embryos, gene regulatory networks drive cells towards discrete terminal fates, a process called canalization. We studied the behavior of the anterior-posterior segmentation network in Drosophila melanogaster embryos by depleting a key maternal input, bicoid (bcd), and measuring gene expression patterns of the network at cellular resolution. This method results in a gene expression atlas containing the levels of mRNA or protein expression of 13 core patterning genes over six time points for every cell of the blastoderm embryo. This is the first cellular resolution dataset of a genetically perturbed Drosophila embryo that captures all cells in 3D. We describe the technical developments required to build this atlas and how the method can be employed and extended by others. We also analyze this novel dataset to characterize the degree and timing of cell fate canalization in the segmentation network. We find that in two layers of this gene regulatory network, following depletion of bcd, individual cells rapidly canalize towards normal cell fates. This result supports the hypothesis that the segmentation network directly canalizes cell fate, rather than an alternative hypothesis whereby cells are initially mis-specified and later eliminated by apoptosis. Our gene expression atlas provides a high resolution picture of a classic perturbation and will enable further computational modeling of canalization and gene regulation in this transcriptional network.
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Affiliation(s)
- Max V Staller
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Charless C Fowlkes
- Department of Computer Science, University of California Irvine, Irvine, CA 92697, USA
| | - Meghan D J Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
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25
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Shadow enhancers enable Hunchback bifunctionality in the Drosophila embryo. Proc Natl Acad Sci U S A 2015; 112:785-90. [PMID: 25564665 DOI: 10.1073/pnas.1413877112] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Hunchback (Hb) is a bifunctional transcription factor that activates and represses distinct enhancers. Here, we investigate the hypothesis that Hb can activate and repress the same enhancer. Computational models predicted that Hb bifunctionally regulates the even-skipped (eve) stripe 3+7 enhancer (eve3+7) in Drosophila blastoderm embryos. We measured and modeled eve expression at cellular resolution under multiple genetic perturbations and found that the eve3+7 enhancer could not explain endogenous eve stripe 7 behavior. Instead, we found that eve stripe 7 is controlled by two enhancers: the canonical eve3+7 and a sequence encompassing the minimal eve stripe 2 enhancer (eve2+7). Hb bifunctionally regulates eve stripe 7, but it executes these two activities on different pieces of regulatory DNA--it activates the eve2+7 enhancer and represses the eve3+7 enhancer. These two "shadow enhancers" use different regulatory logic to create the same pattern.
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26
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Carrell SN, Reeves GT. Imaging the dorsal-ventral axis of live and fixed Drosophila melanogaster embryos. Methods Mol Biol 2015; 1189:63-78. [PMID: 25245687 DOI: 10.1007/978-1-4939-1164-6_5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Optimal imaging conditions are of critical importance in developmental biology, as much of the data in the discipline is acquired through microscopy. However, imaging deep sections of tissue, especially live tissue, can be a technical challenge due to light scattering and difficulties in mounting the sample. In particular, capturing high-quality images of dorsal-ventral cross sections requires "end-on" mounting to orient the anterior-posterior axis vertically. Here we present methods to mount and image dorsal-ventral cross sections of both live and fixed Drosophila melanogaster embryos. Our methods have the advantages of being rapid, allowing deep optical sections, and not requiring expensive, specialized equipment.
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Affiliation(s)
- Sophia N Carrell
- Department of Chemical and Biomolecular Engineering, North Carolina State University, 911 Partners Way, Raleigh, NC, 27695, USA
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27
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Jug F, Pietzsch T, Preibisch S, Tomancak P. Bioimage Informatics in the context of Drosophila research. Methods 2014; 68:60-73. [PMID: 24732429 DOI: 10.1016/j.ymeth.2014.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 04/02/2014] [Accepted: 04/04/2014] [Indexed: 01/05/2023] Open
Abstract
Modern biological research relies heavily on microscopic imaging. The advanced genetic toolkit of Drosophila makes it possible to label molecular and cellular components with unprecedented level of specificity necessitating the application of the most sophisticated imaging technologies. Imaging in Drosophila spans all scales from single molecules to the entire populations of adult organisms, from electron microscopy to live imaging of developmental processes. As the imaging approaches become more complex and ambitious, there is an increasing need for quantitative, computer-mediated image processing and analysis to make sense of the imagery. Bioimage Informatics is an emerging research field that covers all aspects of biological image analysis from data handling, through processing, to quantitative measurements, analysis and data presentation. Some of the most advanced, large scale projects, combining cutting edge imaging with complex bioimage informatics pipelines, are realized in the Drosophila research community. In this review, we discuss the current research in biological image analysis specifically relevant to the type of systems level image datasets that are uniquely available for the Drosophila model system. We focus on how state-of-the-art computer vision algorithms are impacting the ability of Drosophila researchers to analyze biological systems in space and time. We pay particular attention to how these algorithmic advances from computer science are made usable to practicing biologists through open source platforms and how biologists can themselves participate in their further development.
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Affiliation(s)
- Florian Jug
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Tobias Pietzsch
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Stephan Preibisch
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA; Department of Anatomy and Structural Biology, Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Pavel Tomancak
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
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28
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Schmidt T, Pasternak T, Liu K, Blein T, Aubry-Hivet D, Dovzhenko A, Duerr J, Teale W, Ditengou FA, Burkhardt H, Ronneberger O, Palme K. The iRoCS Toolbox--3D analysis of the plant root apical meristem at cellular resolution. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 77:806-14. [PMID: 24417645 DOI: 10.1111/tpj.12429] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 12/16/2013] [Accepted: 12/23/2013] [Indexed: 05/04/2023]
Abstract
To achieve a detailed understanding of processes in biological systems, cellular features must be quantified in the three-dimensional (3D) context of cells and organs. We described use of the intrinsic root coordinate system (iRoCS) as a reference model for the root apical meristem of plants. iRoCS enables direct and quantitative comparison between the root tips of plant populations at single-cell resolution. The iRoCS Toolbox automatically fits standardized coordinates to raw 3D image data. It detects nuclei or segments cells, automatically fits the coordinate system, and groups the nuclei/cells into the root's tissue layers. The division status of each nucleus may also be determined. The only manual step required is to mark the quiescent centre. All intermediate outputs may be refined if necessary. The ability to learn the visual appearance of nuclei by example allows the iRoCS Toolbox to be easily adapted to various phenotypes. The iRoCS Toolbox is provided as an open-source software package, licensed under the GNU General Public License, to make it accessible to a broad community. To demonstrate the power of the technique, we measured subtle changes in cell division patterns caused by modified auxin flux within the Arabidopsis thaliana root apical meristem.
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Affiliation(s)
- Thorsten Schmidt
- Institute for Computer Science, Albert Ludwigs University Freiburg, Georges Köhler Allee, Gebäude 52, D-79110, Freiburg, Germany
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29
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Schmid B, Shah G, Scherf N, Weber M, Thierbach K, Campos CP, Roeder I, Aanstad P, Huisken J. High-speed panoramic light-sheet microscopy reveals global endodermal cell dynamics. Nat Commun 2014; 4:2207. [PMID: 23884240 PMCID: PMC3731668 DOI: 10.1038/ncomms3207] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 06/28/2013] [Indexed: 01/05/2023] Open
Abstract
The ever-increasing speed and resolution of modern microscopes make the storage and post-processing of images challenging and prevent thorough statistical analyses in developmental biology. Here, instead of deploying massive storage and computing power, we exploit the spherical geometry of zebrafish embryos by computing a radial maximum intensity projection in real time with a 240-fold reduction in data rate. In our four-lens selective plane illumination microscope (SPIM) setup the development of multiple embryos is recorded in parallel and a map of all labelled cells is obtained for each embryo in <10 s. In these panoramic projections, cell segmentation and flow analysis reveal characteristic migration patterns and global tissue remodelling in the early endoderm. Merging data from many samples uncover stereotypic patterns that are fundamental to endoderm development in every embryo. We demonstrate that processing and compressing raw image data in real time is not only efficient but indispensable for image-based systems biology. Systematic large-scale analysis of embryonic development requires the processing of large amounts of microscopy data. Here Schmid et al. solve this problem by developing a high-speed imaging system that projects zebrafish embryos onto a ‘world map’ in real time, revealing characteristic migration patterns in the early endoderm.
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Affiliation(s)
- Benjamin Schmid
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
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30
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Wunderlich Z, Bragdon MD, DePace AH. Comparing mRNA levels using in situ hybridization of a target gene and co-stain. Methods 2014; 68:233-41. [PMID: 24434507 DOI: 10.1016/j.ymeth.2014.01.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 01/02/2014] [Indexed: 11/29/2022] Open
Abstract
In situ hybridization is an important technique for measuring the spatial expression patterns of mRNA in cells, tissues, and whole animals. However, mRNA levels cannot be compared across experiments using typical protocols. Here we present a semi-quantitative method to compare mRNA levels of a gene across multiple samples. This method yields an estimate of the error in the measurement to allow statistical comparison. Our method uses a typical in situ hybridization protocol to stain for a target gene and an internal standard, which we refer to as a co-stain. As a proof of concept, we apply this method to multiple lines of transgenic Drosophila embryos, harboring constructs that express reporter genes to different levels. We generated this test set by mutating enhancer sequences to contain different numbers of binding sites for Zelda, a transcriptional activator. We demonstrate that using a co-stain with in situ hybridization is an effective method to compare mRNA levels across samples. This method requires only minor modifications to existing in situ hybridization protocols and uses straightforward analysis techniques. This strategy can be broadly applied to detect quantitative, spatially resolved changes in mRNA levels.
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Affiliation(s)
- Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, 200 Longwood Ave., Boston, MA 02115, USA.
| | - Meghan D Bragdon
- Department of Systems Biology, Harvard Medical School, 200 Longwood Ave., Boston, MA 02115, USA.
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, 200 Longwood Ave., Boston, MA 02115, USA.
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31
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Aerni SJ, Liu X, Do CB, Gross SS, Nguyen A, Guo SD, Long F, Peng H, Kim SS, Batzoglou S. Automated cellular annotation for high-resolution images of adult Caenorhabditis elegans. Bioinformatics 2013; 29:i18-26. [PMID: 23812982 PMCID: PMC3694659 DOI: 10.1093/bioinformatics/btt223] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Motivation: Advances in high-resolution microscopy have recently made possible the analysis of gene expression at the level of individual cells. The fixed lineage of cells in the adult worm Caenorhabditis elegans makes this organism an ideal model for studying complex biological processes like development and aging. However, annotating individual cells in images of adult C.elegans typically requires expertise and significant manual effort. Automation of this task is therefore critical to enabling high-resolution studies of a large number of genes. Results: In this article, we describe an automated method for annotating a subset of 154 cells (including various muscle, intestinal and hypodermal cells) in high-resolution images of adult C.elegans. We formulate the task of labeling cells within an image as a combinatorial optimization problem, where the goal is to minimize a scoring function that compares cells in a test input image with cells from a training atlas of manually annotated worms according to various spatial and morphological characteristics. We propose an approach for solving this problem based on reduction to minimum-cost maximum-flow and apply a cross-entropy–based learning algorithm to tune the weights of our scoring function. We achieve 84% median accuracy across a set of 154 cell labels in this highly variable system. These results demonstrate the feasibility of the automatic annotation of microscopy-based images in adult C.elegans. Contact:saerni@cs.stanford.edu
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Affiliation(s)
- Sarah J Aerni
- Department of Computer Science, Stanford University, 353 Serra Mall, Stanford, CA 94305, USA.
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32
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Knowles DW, Biggin MD. Building quantitative, three-dimensional atlases of gene expression and morphology at cellular resolution. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2013; 2:767-79. [PMID: 24123936 PMCID: PMC3819199 DOI: 10.1002/wdev.107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Animals comprise dynamic three-dimensional arrays of cells that express gene products in intricate spatial and temporal patterns that determine cellular differentiation and morphogenesis. A rigorous understanding of these developmental processes requires automated methods that quantitatively record and analyze complex morphologies and their associated patterns of gene expression at cellular resolution. Here we summarize light microscopy-based approaches to establish permanent, quantitative datasets-atlases-that record this information. We focus on experiments that capture data for whole embryos or large areas of tissue in three dimensions, often at multiple time points. We compare and contrast the advantages and limitations of different methods and highlight some of the discoveries made. We emphasize the need for interdisciplinary collaborations and integrated experimental pipelines that link sample preparation, image acquisition, image analysis, database design, visualization, and quantitative analysis.
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Affiliation(s)
- David W. Knowles
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 84-171, Berkeley, CA 97720
| | - Mark D. Biggin
- Genomics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 84-171, Berkeley, CA 94720
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33
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Rizzi B, Peyrieras N. Towards 3D in silico modeling of the sea urchin embryonic development. J Chem Biol 2013; 7:17-28. [PMID: 24386014 PMCID: PMC3877407 DOI: 10.1007/s12154-013-0101-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 07/22/2013] [Indexed: 11/29/2022] Open
Abstract
Embryogenesis is a dynamic process with an intrinsic variability whose understanding requires the integration of molecular, genetic, and cellular dynamics. Biological circuits function over time at the level of single cells and require a precise analysis of the topology, temporality, and probability of events. Integrative developmental biology is currently looking for the appropriate strategies to capture the intrinsic properties of biological systems. The "-omic" approaches require disruption of the function of the biological circuit; they provide static information, with low temporal resolution and usually with population averaging that masks fast or variable features at the cellular scale and in a single individual. This data should be correlated with cell behavior as cells are the integrators of biological activity. Cellular dynamics are captured by the in vivo microscopy observation of live organisms. This can be used to reconstruct the 3D + time cell lineage tree to serve as the basis for modeling the organism's multiscale dynamics. We discuss here the progress that has been made in this direction, starting with the reconstruction over time of three-dimensional digital embryos from in toto time-lapse imaging. Digital specimens provide the means for a quantitative description of the development of model organisms that can be stored, shared, and compared. They open the way to in silico experimentation and to a more theoretical approach to biological processes. We show, with some unpublished results, how the proposed methodology can be applied to sea urchin species that have been model organisms in the field of classical embryology and modern developmental biology for over a century.
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Affiliation(s)
- Barbara Rizzi
- CNRS-MDAM, UPR 3294 and BioEmergences-IBiSA, Institut de Neurobiologie Alfred Fessard, CNRS, Gif-sur-Yvette, France
- Institut des Systèmes Complexes, 57-59 rue Lhomond, Paris, France
| | - Nadine Peyrieras
- CNRS-MDAM, UPR 3294 and BioEmergences-IBiSA, Institut de Neurobiologie Alfred Fessard, CNRS, Gif-sur-Yvette, France
- Institut des Systèmes Complexes, 57-59 rue Lhomond, Paris, France
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34
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Paris M, Kaplan T, Li XY, Villalta JE, Lott SE, Eisen MB. Extensive divergence of transcription factor binding in Drosophila embryos with highly conserved gene expression. PLoS Genet 2013; 9:e1003748. [PMID: 24068946 PMCID: PMC3772039 DOI: 10.1371/journal.pgen.1003748] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 07/10/2013] [Indexed: 11/19/2022] Open
Abstract
To better characterize how variation in regulatory sequences drives divergence in gene expression, we undertook a systematic study of transcription factor binding and gene expression in blastoderm embryos of four species, which sample much of the diversity in the 40 million-year old genus Drosophila: D. melanogaster, D. yakuba, D. pseudoobscura and D. virilis. We compared gene expression, measured by mRNA-seq, to the genome-wide binding, measured by ChIP-seq, of four transcription factors involved in early anterior-posterior patterning. We found that mRNA levels are much better conserved than individual transcription factor binding events, and that changes in a gene's expression were poorly explained by changes in adjacent transcription factor binding. However, highly bound sites, sites in regions bound by multiple factors and sites near genes are conserved more frequently than other binding, suggesting that a considerable amount of transcription factor binding is weakly or non-functional and not subject to purifying selection.
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Affiliation(s)
- Mathilde Paris
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Tommy Kaplan
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- School of Computer Science and Engineering, The Hebrew University, Jerusalem, Israel
| | - Xiao Yong Li
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- Howard Hughes Medical Institute, University of California Berkeley, Berkeley, California, United States of America
| | | | - Susan E. Lott
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- Department of Evolution and Ecology, University of California, Davis, California, United States of America
| | - Michael B. Eisen
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, United States of America
- School of Computer Science and Engineering, The Hebrew University, Jerusalem, Israel
- Howard Hughes Medical Institute, University of California Berkeley, Berkeley, California, United States of America
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35
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Ilsley GR, Fisher J, Apweiler R, DePace AH, Luscombe NM. Cellular resolution models for even skipped regulation in the entire Drosophila embryo. eLife 2013; 2:e00522. [PMID: 23930223 PMCID: PMC3736529 DOI: 10.7554/elife.00522] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 06/17/2013] [Indexed: 12/14/2022] Open
Abstract
Transcriptional control ensures genes are expressed in the right amounts at the correct times and locations. Understanding quantitatively how regulatory systems convert input signals to appropriate outputs remains a challenge. For the first time, we successfully model even skipped (eve) stripes 2 and 3+7 across the entire fly embryo at cellular resolution. A straightforward statistical relationship explains how transcription factor (TF) concentrations define eve's complex spatial expression, without the need for pairwise interactions or cross-regulatory dynamics. Simulating thousands of TF combinations, we recover known regulators and suggest new candidates. Finally, we accurately predict the intricate effects of perturbations including TF mutations and misexpression. Our approach imposes minimal assumptions about regulatory function; instead we infer underlying mechanisms from models that best fit the data, like the lack of TF-specific thresholds and the positional value of homotypic interactions. Our study provides a general and quantitative method for elucidating the regulation of diverse biological systems. DOI:http://dx.doi.org/10.7554/eLife.00522.001.
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Affiliation(s)
- Garth R Ilsley
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Jasmin Fisher
- Microsoft Research Cambridge, Cambridge, United Kingdom
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Rolf Apweiler
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - Nicholas M Luscombe
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- UCL Genetics Institute, Department of Genetics, Evolution, and Environment, University College London, London, United Kingdom
- London Research Institute, Cancer Research UK, London, United Kingdom
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36
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Mace DL, Weisdepp P, Gevirtzman L, Boyle T, Waterston RH. A high-fidelity cell lineage tracing method for obtaining systematic spatiotemporal gene expression patterns in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2013; 3:851-63. [PMID: 23550142 PMCID: PMC3656732 DOI: 10.1534/g3.113.005918] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 03/16/2013] [Indexed: 12/17/2022]
Abstract
Advances in microscopy and fluorescent reporters have allowed us to detect the onset of gene expression on a cell-by-cell basis in a systemic fashion. This information, however, is often encoded in large repositories of images, and developing ways to extract this spatiotemporal expression data is a difficult problem that often uses complex domain-specific methods for each individual data set. We present a more unified approach that incorporates general previous information into a hierarchical probabilistic model to extract spatiotemporal gene expression from 4D confocal microscopy images of developing Caenorhabditis elegans embryos. This approach reduces the overall error rate of our automated lineage tracing pipeline by 3.8-fold, allowing us to routinely follow the C. elegans lineage to later stages of development, where individual neuronal subspecification becomes apparent. Unlike previous methods that often use custom approaches that are organism specific, our method uses generalized linear models and extensions of standard reversible jump Markov chain Monte Carlo methods that can be readily extended to other organisms for a variety of biological inference problems relating to cell fate specification. This modeling approach is flexible and provides tractable avenues for incorporating additional previous information into the model for similar difficult high-fidelity/low error tolerance image analysis problems for systematically applied genomic experiments.
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Affiliation(s)
- Daniel L Mace
- Department of Genome Sciences, University of Washington, Seattle, Washington 98103, USA.
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37
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Samee AH, Sinha S. Evaluating thermodynamic models of enhancer activity on cellular resolution gene expression data. Methods 2013; 62:79-90. [PMID: 23624421 DOI: 10.1016/j.ymeth.2013.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 03/04/2013] [Indexed: 11/18/2022] Open
Abstract
With the advent of high throughput sequencing and high resolution transcriptomic technologies, there exists today an unprecedented opportunity to understand gene regulation at a quantitative level. State of the art models of the relationship between regulatory sequence and gene expression have shown great promise, but also suffer from some major shortcomings. In this paper, we identify and address methodological challenges pertaining to quantitative modeling of gene expression from sequence, and test our models on the anterior-posterior patterning system in the Drosophila embryo. We first develop a framework to process cellular resolution three-dimensional gene expression data from the Drosophila embryo and create data sets on which quantitative models can be trained. Next we propose a new score, called 'weighted pattern generating potential' (w-PGP), to evaluate model predictions, and show its advantages over the two most common scoring schemes in use today. The model building exercise uses w-PGP as the evaluation score and adopts a systematic strategy to increase a model's complexity while guarding against over-fitting. Our model identifies three transcription factors--ZELDA, SLOPPY-PAIRED, and NUBBIN--that have not been previously incorporated in quantitative models of this system, as having significant regulatory influence. Finally, we show how fitting quantitative models on data sets comprising a handful of enhancers, as reported in earlier work, may lead to unreliable models.
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Affiliation(s)
- Abul Hassan Samee
- Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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38
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He F, Ma J. A spatial point pattern analysis in Drosophila blastoderm embryos evaluating the potential inheritance of transcriptional states. PLoS One 2013; 8:e60876. [PMID: 23593336 PMCID: PMC3621909 DOI: 10.1371/journal.pone.0060876] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 03/04/2013] [Indexed: 01/10/2023] Open
Abstract
The Drosophila blastoderm embryo undergoes rapid cycles of nuclear division. This poses a challenge to genes that need to reliably sense the concentrations of morphogen molecules to form desired expression patterns. Here we investigate whether the transcriptional state of hunchback (hb), a target gene directly activated by the morphogenetic protein Bicoid (Bcd), exhibits properties indicative of inheritance between mitotic cycles. To achieve this, we build a dataset of hb transcriptional states at the resolution of individual nuclei in embryos at early cycle 14. We perform a spatial point pattern (SPP) analysis to evaluate the spatial relationships among the nuclei that have distinct numbers of hb gene copies undergoing active transcription in snapshots of embryos. Our statistical tests and simulation studies reveal properties of dispersed clustering for nuclei with both or neither copies of hb undergoing active transcription. Modeling of nuclear lineages from cycle 11 to cycle 14 suggests that these two types of nuclei can achieve spatial clustering when, and only when, the transcriptional states are allowed to propagate between mitotic cycles. Our results are consistent with the possibility where the positional information encoded by the Bcd morphogen gradient may not need to be decoded de novo at all mitotic cycles in the Drosophila blastoderm embryo.
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Affiliation(s)
- Feng He
- Division of Biomedical Informatics, Cincinnati Children's Research Foundation, Cincinnati, Ohio, United States of America
| | - Jun Ma
- Division of Biomedical Informatics, Cincinnati Children's Research Foundation, Cincinnati, Ohio, United States of America
- Division of Developmental Biology, Cincinnati Children's Research Foundation, Cincinnati, Ohio, United States of America
- * E-mail:
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39
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Cai X, Wang H, Huang H, Ding C. Joint stage recognition and anatomical annotation of Drosophila gene expression patterns. Bioinformatics 2013; 28:i16-24. [PMID: 22689756 PMCID: PMC3371852 DOI: 10.1093/bioinformatics/bts220] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Motivation: Staining the mRNA of a gene via in situ hybridization (ISH) during the development of a Drosophila melanogaster embryo delivers the detailed spatio-temporal patterns of the gene expression. Many related biological problems such as the detection of co-expressed genes, co-regulated genes and transcription factor binding motifs rely heavily on the analysis of these image patterns. To provide the text-based pattern searching for facilitating related biological studies, the images in the Berkeley Drosophila Genome Project (BDGP) study are annotated with developmental stage term and anatomical ontology terms manually by domain experts. Due to the rapid increase in the number of such images and the inevitable bias annotations by human curators, it is necessary to develop an automatic method to recognize the developmental stage and annotate anatomical terms. Results: In this article, we propose a novel computational model for jointly stage classification and anatomical terms annotation of Drosophila gene expression patterns. We propose a novel Tri-Relational Graph (TG) model that comprises the data graph, anatomical term graph, developmental stage term graph, and connect them by two additional graphs induced from stage or annotation label assignments. Upon the TG model, we introduce a Preferential Random Walk (PRW) method to jointly recognize developmental stage and annotate anatomical terms by utilizing the interrelations between two tasks. The experimental results on two refined BDGP datasets demonstrate that our joint learning method can achieve superior prediction results on both tasks than the state-of-the-art methods. Availability:http://ranger.uta.edu/%7eheng/Drosophila/ Contact:heng@uta.edu
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Affiliation(s)
- Xiao Cai
- Department of Computer Science and Engineering, University of Texas at Arlington, Arlington, TX 76019, USA
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40
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Wunderlich Z, Bragdon MD, Eckenrode KB, Lydiard-Martin T, Pearl-Waserman S, DePace AH. Dissecting sources of quantitative gene expression pattern divergence between Drosophila species. Mol Syst Biol 2013; 8:604. [PMID: 22893002 PMCID: PMC3435502 DOI: 10.1038/msb.2012.35] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 07/12/2012] [Indexed: 12/21/2022] Open
Abstract
Gene expression patterns can diverge between species due to changes in a gene's regulatory DNA or changes in the proteins, e.g., transcription factors (TFs), that regulate the gene. We developed a modeling framework to uncover the sources of expression differences in blastoderm embryos of three Drosophila species, focusing on the regulatory circuit controlling expression of the hunchback (hb) posterior stripe. Using this framework and cellular-resolution expression measurements of hb and its regulating TFs, we found that changes in the expression patterns of hb's TFs account for much of the expression divergence. We confirmed our predictions using transgenic D. melanogaster lines, which demonstrate that this set of orthologous cis-regulatory elements (CREs) direct similar, but not identical, expression patterns. We related expression pattern differences to sequence changes in the CRE using a calculation of the CRE's TF binding site content. By applying this calculation in both the transgenic and endogenous contexts, we found that changes in binding site content affect sensitivity to regulating TFs and that compensatory evolution may occur in circuit components other than the CRE.
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Affiliation(s)
- Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
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The importance of geometry in mathematical models of developing systems. Curr Opin Genet Dev 2012; 22:547-52. [PMID: 23107453 DOI: 10.1016/j.gde.2012.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 09/20/2012] [Accepted: 09/25/2012] [Indexed: 11/21/2022]
Abstract
Understanding the interaction between the spatial variation of extracellular signals and the interpretation of such signals in embryonic development is difficult without a mathematical model, but the inherent limitations of a model can have a profound impact on its utility. A central issue is the level of abstraction needed, and here we focus on the role of geometry in models and how the choice of the spatial dimension can influence the conclusions reached. A widely studied system in which the proper choice of geometry is critical is embryonic development of Drosophila melanogaster, and we discuss recent work in which 3D embryo-scale modeling is used to identify key modes of transport, analyze gap gene expression, and test BMP-mediated positive feedback mechanisms.
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Depleting gene activities in early Drosophila embryos with the "maternal-Gal4-shRNA" system. Genetics 2012; 193:51-61. [PMID: 23105012 DOI: 10.1534/genetics.112.144915] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In a developing Drosophila melanogaster embryo, mRNAs have a maternal origin, a zygotic origin, or both. During the maternal-zygotic transition, maternal products are degraded and gene expression comes under the control of the zygotic genome. To interrogate the function of mRNAs that are both maternally and zygotically expressed, it is common to examine the embryonic phenotypes derived from female germline mosaics. Recently, the development of RNAi vectors based on short hairpin RNAs (shRNAs) effective during oogenesis has provided an alternative to producing germline clones. Here, we evaluate the efficacies of: (1) maternally loaded shRNAs to knockdown zygotic transcripts and (2) maternally loaded Gal4 protein to drive zygotic shRNA expression. We show that, while Gal4-driven shRNAs in the female germline very effectively generate phenotypes for genes expressed maternally, maternally loaded shRNAs are not very effective at generating phenotypes for early zygotic genes. However, maternally loaded Gal4 protein is very efficient at generating phenotypes for zygotic genes expressed during mid-embryogenesis. We apply this powerful and simple method to unravel the embryonic functions of a number of pleiotropic genes.
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Trisnadi N, Altinok A, Stathopoulos A, Reeves GT. Image analysis and empirical modeling of gene and protein expression. Methods 2012; 62:68-78. [PMID: 23104159 DOI: 10.1016/j.ymeth.2012.09.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 09/01/2012] [Accepted: 09/05/2012] [Indexed: 11/26/2022] Open
Abstract
Protein gradients and gene expression patterns are major determinants in the differentiation and fate map of the developing embryo. Here we discuss computational methods to quantitatively measure the positions of gene expression domains and the gradients of protein expression along the dorsal-ventral axis in the Drosophila embryo. Our methodology involves three layers of data. The first layer, or the primary data, consists of z-stack confocal images of embryos processed by in situ hybridization and/or antibody stainings. The secondary data are relationships between location, usually an x-axis coordinate, and fluorescent intensity of gene or protein detection. Tertiary data comprise the optimal parameters that arise from fits of the secondary data to empirical models. The tertiary data are useful to distill large datasets of imaged embryos down to a tractable number of conceptually useful parameters. This analysis allows us to detect subtle phenotypes and is adaptable to any set of genes or proteins with a canonical pattern. For example, we show how insights into the Dorsal transcription factor protein gradient and its target gene ventral-neuroblasts defective (vnd) were obtained using such quantitative approaches.
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Affiliation(s)
- Nathanie Trisnadi
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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Botman D, Kaandorp JA. Spatial gene expression quantification: a tool for analysis of in situ hybridizations in sea anemone Nematostella vectensis. BMC Res Notes 2012; 5:555. [PMID: 23039089 PMCID: PMC3532226 DOI: 10.1186/1756-0500-5-555] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 09/26/2012] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Spatial gene expression quantification is required for modeling gene regulation in developing organisms. The fruit fly Drosophila melanogaster is the model system most widely applied for spatial gene expression analysis due to its unique embryonic properties: the shape does not change significantly during its early cleavage cycles and most genes are differentially expressed along a straight axis. This system of development is quite exceptional in the animal kingdom.In the sea anemone Nematostella vectensis the embryo changes its shape during early development; there are cell divisions and cell movement, like in most other metazoans. Nematostella is an attractive case study for spatial gene expression since its transparent body wall makes it accessible to various imaging techniques. FINDINGS Our new quantification method produces standardized gene expression profiles from raw or annotated Nematostella in situ hybridizations by measuring the expression intensity along its cell layer. The procedure is based on digital morphologies derived from high-resolution fluorescence pictures. Additionally, complete descriptions of nonsymmetric expression patterns have been constructed by transforming the gene expression images into a three-dimensional representation. CONCLUSIONS We created a standard format for gene expression data, which enables quantitative analysis of in situ hybridizations from embryos with various shapes in different developmental stages. The obtained expression profiles are suitable as input for optimization of gene regulatory network models, and for correlation analysis of genes from dissimilar Nematostella morphologies. This approach is potentially applicable to many other metazoan model organisms and may also be suitable for processing data from three-dimensional imaging techniques.
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Affiliation(s)
- Daniel Botman
- Section Computational Science, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Jaap A Kaandorp
- Section Computational Science, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
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Medium-throughput processing of whole mount in situ hybridisation experiments into gene expression domains. PLoS One 2012; 7:e46658. [PMID: 23029561 PMCID: PMC3460907 DOI: 10.1371/journal.pone.0046658] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 09/05/2012] [Indexed: 11/19/2022] Open
Abstract
Understanding the function and evolution of developmental regulatory networks requires the characterisation and quantification of spatio-temporal gene expression patterns across a range of systems and species. However, most high-throughput methods to measure the dynamics of gene expression do not preserve the detailed spatial information needed in this context. For this reason, quantification methods based on image bioinformatics have become increasingly important over the past few years. Most available approaches in this field either focus on the detailed and accurate quantification of a small set of gene expression patterns, or attempt high-throughput analysis of spatial expression through binary pattern extraction and large-scale analysis of the resulting datasets. Here we present a robust, “medium-throughput” pipeline to process in situ hybridisation patterns from embryos of different species of flies. It bridges the gap between high-resolution, and high-throughput image processing methods, enabling us to quantify graded expression patterns along the antero-posterior axis of the embryo in an efficient and straightforward manner. Our method is based on a robust enzymatic (colorimetric) in situ hybridisation protocol and rapid data acquisition through wide-field microscopy. Data processing consists of image segmentation, profile extraction, and determination of expression domain boundary positions using a spline approximation. It results in sets of measured boundaries sorted by gene and developmental time point, which are analysed in terms of expression variability or spatio-temporal dynamics. Our method yields integrated time series of spatial gene expression, which can be used to reverse-engineer developmental gene regulatory networks across species. It is easily adaptable to other processes and species, enabling the in silico reconstitution of gene regulatory networks in a wide range of developmental contexts.
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Yuan L, Woodard A, Ji S, Jiang Y, Zhou ZH, Kumar S, Ye J. Learning sparse representations for fruit-fly gene expression pattern image annotation and retrieval. BMC Bioinformatics 2012; 13:107. [PMID: 22621237 PMCID: PMC3434040 DOI: 10.1186/1471-2105-13-107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 05/23/2012] [Indexed: 11/10/2022] Open
Abstract
Background Fruit fly embryogenesis is one of the best understood animal development systems, and the spatiotemporal gene expression dynamics in this process are captured by digital images. Analysis of these high-throughput images will provide novel insights into the functions, interactions, and networks of animal genes governing development. To facilitate comparative analysis, web-based interfaces have been developed to conduct image retrieval based on body part keywords and images. Currently, the keyword annotation of spatiotemporal gene expression patterns is conducted manually. However, this manual practice does not scale with the continuously expanding collection of images. In addition, existing image retrieval systems based on the expression patterns may be made more accurate using keywords. Results In this article, we adapt advanced data mining and computer vision techniques to address the key challenges in annotating and retrieving fruit fly gene expression pattern images. To boost the performance of image annotation and retrieval, we propose representations integrating spatial information and sparse features, overcoming the limitations of prior schemes. Conclusions We perform systematic experimental studies to evaluate the proposed schemes in comparison with current methods. Experimental results indicate that the integration of spatial information and sparse features lead to consistent performance improvement in image annotation, while for the task of retrieval, sparse features alone yields better results.
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Affiliation(s)
- Lei Yuan
- Center for Evolutionary Medicine and Informatics, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
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Knowles DW. Three-dimensional morphology and gene expression mapping for the Drosophila blastoderm. Cold Spring Harb Protoc 2012; 2012:150-61. [PMID: 22301653 DOI: 10.1101/pdb.top067843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
To properly understand the transcriptional network of animals, we must have full quantitative comprehension of the spatial and temporal expression patterns of transcription factors and their targets. Visual inspection of embryos stained to reveal the patterns of genes shows levels of expression that change from cell to cell in a complex manner. With our current wealth of knowledge regarding the basic biology of animal genomes and the components of their transcriptional regulatory networks, combined with current technologies in optical microscopy, computing, and image and vision analysis, we should be able to capture quantitative, three-dimensional (3D) information about the transcriptional network (all factors and targets) for an entire animal at cellular resolution. It should also be possible to assemble these data into a single computationally analyzable database--an atlas--that could be the basis for uncovering new biology governing regulatory gene networks. This article describes progress toward realizing these goals, with the focus on Drosophila melanogaster. It describes a suite of high-throughput methods that have been used to create the first quantitative 3D description of gene expression and morphology at cellular resolution in a whole animal, and it presents some of the new biology that has been revealed by this quantitative atlas.
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Hengenius JB, Gribskov M, Rundell AE, Fowlkes CC, Umulis DM. Analysis of gap gene regulation in a 3D organism-scale model of the Drosophila melanogaster embryo. PLoS One 2011; 6:e26797. [PMID: 22110594 PMCID: PMC3217930 DOI: 10.1371/journal.pone.0026797] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 10/04/2011] [Indexed: 01/30/2023] Open
Abstract
The axial bodyplan of Drosophila melanogaster is determined during a process called morphogenesis. Shortly after fertilization, maternal bicoid mRNA is translated into Bicoid (Bcd). This protein establishes a spatially graded morphogen distribution along the anterior-posterior (AP) axis of the embryo. Bcd initiates AP axis determination by triggering expression of gap genes that subsequently regulate each other's expression to form a precisely controlled spatial distribution of gene products. Reaction-diffusion models of gap gene expression on a 1D domain have previously been used to infer complex genetic regulatory network (GRN) interactions by optimizing model parameters with respect to 1D gap gene expression data. Here we construct a finite element reaction-diffusion model with a realistic 3D geometry fit to full 3D gap gene expression data. Though gap gene products exhibit dorsal-ventral asymmetries, we discover that previously inferred gap GRNs yield qualitatively correct AP distributions on the 3D domain only when DV-symmetric initial conditions are employed. Model patterning loses qualitative agreement with experimental data when we incorporate a realistic DV-asymmetric distribution of Bcd. Further, we find that geometry alone is insufficient to account for DV-asymmetries in the final gap gene distribution. Additional GRN optimization confirms that the 3D model remains sensitive to GRN parameter perturbations. Finally, we find that incorporation of 3D data in simulation and optimization does not constrain the search space or improve optimization results.
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Affiliation(s)
- James B. Hengenius
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Michael Gribskov
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Ann E. Rundell
- Department of Biomedical Engineering, Purdue University, West Lafayette, Indiana, United States of America
| | - Charless C. Fowlkes
- Department of Computer Science, University of California Irvine, Irvine, California, United States of America
| | - David M. Umulis
- Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
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A conserved developmental patterning network produces quantitatively different output in multiple species of Drosophila. PLoS Genet 2011; 7:e1002346. [PMID: 22046143 PMCID: PMC3203197 DOI: 10.1371/journal.pgen.1002346] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Accepted: 08/27/2011] [Indexed: 11/18/2022] Open
Abstract
Differences in the level, timing, or location of gene expression can contribute to alternative phenotypes at the molecular and organismal level. Understanding the origins of expression differences is complicated by the fact that organismal morphology and gene regulatory networks could potentially vary even between closely related species. To assess the scope of such changes, we used high-resolution imaging methods to measure mRNA expression in blastoderm embryos of Drosophila yakuba and Drosophila pseudoobscura and assembled these data into cellular resolution atlases, where expression levels for 13 genes in the segmentation network are averaged into species-specific, cellular resolution morphological frameworks. We demonstrate that the blastoderm embryos of these species differ in their morphology in terms of size, shape, and number of nuclei. We present an approach to compare cellular gene expression patterns between species, while accounting for varying embryo morphology, and apply it to our data and an equivalent dataset for Drosophila melanogaster. Our analysis reveals that all individual genes differ quantitatively in their spatio-temporal expression patterns between these species, primarily in terms of their relative position and dynamics. Despite many small quantitative differences, cellular gene expression profiles for the whole set of genes examined are largely similar. This suggests that cell types at this stage of development are conserved, though they can differ in their relative position by up to 3–4 cell widths and in their relative proportion between species by as much as 5-fold. Quantitative differences in the dynamics and relative level of a subset of genes between corresponding cell types may reflect altered regulatory functions between species. Our results emphasize that transcriptional networks can diverge over short evolutionary timescales and that even small changes can lead to distinct output in terms of the placement and number of equivalent cells. For a gene to function properly, it must be active in the right place, at the right time, and in the right amount. Changes in any of these features can lead to observable differences between individuals and species and in some cases can lead to disease. We do not currently understand how the position, timing, and amount of gene expression is encoded in DNA sequence. One approach to this problem is to compare how gene expression differs between species and to try to relate changes in DNA sequence to changes in gene expression. Here, we take the first step by comparing gene expression patterns at high spatial and temporal resolution between embryos of three species of fruit flies. We develop methods for comparing gene expression in individual cells, which allow us to control for variation in the size, shape, and number of nuclei between embryos. We find measurable quantitative differences in the patterns for all individual genes that we have examined. However, by considering all genes in our dataset at once, we show that many genes are changing together, leading to largely equivalent types of cells in these three species.
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Image analysis for understanding embryo development: a bridge from microscopy to biological insights. Curr Opin Genet Dev 2011; 21:630-7. [DOI: 10.1016/j.gde.2011.08.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/01/2011] [Accepted: 08/10/2011] [Indexed: 11/22/2022]
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