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van Staalduinen J, van Staveren T, Grosveld F, Wendt KS. Live-cell imaging of chromatin contacts opens a new window into chromatin dynamics. Epigenetics Chromatin 2023; 16:27. [PMID: 37349773 PMCID: PMC10288748 DOI: 10.1186/s13072-023-00503-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 06/15/2023] [Indexed: 06/24/2023] Open
Abstract
Our understanding of the organization of the chromatin fiber within the cell nucleus has made great progress in the last few years. High-resolution techniques based on next-generation sequencing as well as optical imaging that can investigate chromatin conformations down to the single cell level have revealed that chromatin structure is highly heterogeneous at the level of the individual allele. While TAD boundaries and enhancer-promoter pairs emerge as hotspots of 3D proximity, the spatiotemporal dynamics of these different types of chromatin contacts remain largely unexplored. Investigation of chromatin contacts in live single cells is necessary to close this knowledge gap and further enhance the current models of 3D genome organization and enhancer-promoter communication. In this review, we first discuss the potential of single locus labeling to study architectural and enhancer-promoter contacts and provide an overview of the available single locus labeling techniques such as FROS, TALE, CRISPR-dCas9 and ANCHOR, and discuss the latest developments and applications of these systems.
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Affiliation(s)
- Jente van Staalduinen
- Department of Cell Biology, Erasmus MC, Dr. Molewaterplein 50, 3015 GE, Rotterdam, The Netherlands
| | - Thomas van Staveren
- Department of Cell Biology, Erasmus MC, Dr. Molewaterplein 50, 3015 GE, Rotterdam, The Netherlands
| | - Frank Grosveld
- Department of Cell Biology, Erasmus MC, Dr. Molewaterplein 50, 3015 GE, Rotterdam, The Netherlands
| | - Kerstin S Wendt
- Department of Cell Biology, Erasmus MC, Dr. Molewaterplein 50, 3015 GE, Rotterdam, The Netherlands.
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Lu S, Hou Y, Zhang XE, Gao Y. Live cell imaging of DNA and RNA with fluorescent signal amplification and background reduction techniques. Front Cell Dev Biol 2023; 11:1216232. [PMID: 37342234 PMCID: PMC10277805 DOI: 10.3389/fcell.2023.1216232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 05/24/2023] [Indexed: 06/22/2023] Open
Abstract
Illuminating DNA and RNA dynamics in live cell can elucidate their life cycle and related biochemical activities. Various protocols have been developed for labeling the regions of interest in DNA and RNA molecules with different types of fluorescent probes. For example, CRISPR-based techniques have been extensively used for imaging genomic loci. However, some DNA and RNA molecules can still be difficult to tag and observe dynamically, such as genomic loci in non-repetitive regions. In this review, we will discuss the toolbox of techniques and methodologies that have been developed for imaging DNA and RNA. We will also introduce optimized systems that provide enhanced signal intensity or low background fluorescence for those difficult-to-tag molecules. These strategies can provide new insights for researchers when designing and using techniques to visualize DNA or RNA molecules.
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Affiliation(s)
- Song Lu
- Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
| | - Yu Hou
- Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Xian-En Zhang
- Faculty of Synthetic Biology, Shenzhen Institute of Advanced Technology, Shenzhen, China
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yunhua Gao
- Center for Advanced Measurement Science, National Institute of Metrology, Beijing, China
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Hou Y, Wang D, Lu S, Guo D, Li M, Cui M, Zhang XE. Optogenetic Control of Background Fluorescence Reduction for CRISPR-Based Genome Imaging. Anal Chem 2022; 94:8724-8731. [PMID: 35666940 DOI: 10.1021/acs.analchem.2c01113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The CRISPR/dCas9 system has become an essential tool for live-cell imaging of genomic loci, but it has limited applications in imaging low-/non-repetitive genomic loci due to the strong nuclear background noise emerging from many untargeted fluorescent modules. Here, we propose an optogenetically controlled background fluorescence reduction strategy that combines the CRISPR-SunTag system with a light-inducible nuclear export tag (LEXY). Utilizing the SunTag system, multiple copies of LEXY-tagged sfGFP were recruited to the C-terminal dCas9, recognizing the target genomic loci. As the nuclear export sequence at the C-terminal LEXY could be exposed to pulsed blue light irradiation, the untargeted nuclear labeling modules were light controllably transferred to the cytoplasm. Consequently, genomic loci containing as few as nine copies of repeats were clearly visualized, and a significant increase in the signal-to-noise ratio was achieved. This simple and controllable method is expected to have a wide range of applications in cell biology.
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Affiliation(s)
- Yu Hou
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dianbing Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Song Lu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Dongge Guo
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Min Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Mengmeng Cui
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Xian-En Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
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Zhang M, Yang C, Tasan I, Zhao H. Expanding the Potential of Mammalian Genome Engineering via Targeted DNA Integration. ACS Synth Biol 2021; 10:429-446. [PMID: 33596056 DOI: 10.1021/acssynbio.0c00576] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inserting custom designed DNA sequences into the mammalian genome plays an essential role in synthetic biology. In particular, the ability to introduce foreign DNA in a site-specific manner offers numerous advantages over random DNA integration. In this review, we focus on two mechanistically distinct systems that have been widely adopted for targeted DNA insertion in mammalian cells, the CRISPR/Cas9 system and site-specific recombinases. The CRISPR/Cas9 system has revolutionized the genome engineering field thanks to its high programmability and ease of use. However, due to its dependence on linearized DNA donor and endogenous cellular pathways to repair the induced double-strand break, CRISPR/Cas9-mediated DNA insertion still faces limitations such as small insert size, and undesired editing outcomes via error-prone repair pathways. In contrast, site-specific recombinases, in particular the Serine integrases, demonstrate large-cargo capability and no dependence on cellular repair pathways for DNA integration. Here we first describe recent advances in improving the overall efficacy of CRISPR/Cas9-based methods for DNA insertion. Moreover, we highlight the advantages of site-specific recombinases over CRISPR/Cas9 in the context of targeted DNA integration, with a special focus on the recent development of programmable recombinases. We conclude by discussing the importance of protein engineering to further expand the current toolkit for targeted DNA insertion in mammalian cells.
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Affiliation(s)
- Meng Zhang
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Che Yang
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ipek Tasan
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Huimin Zhao
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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