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Hockenberry MA, Daugird TA, Legant WR. Cell dynamics revealed by microscopy advances. Curr Opin Cell Biol 2024; 90:102418. [PMID: 39159598 DOI: 10.1016/j.ceb.2024.102418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 07/23/2024] [Accepted: 07/24/2024] [Indexed: 08/21/2024]
Abstract
Cell biology emerges from spatiotemporally coordinated molecular processes. Recent advances in live-cell microscopy, fueled by a surge in optical, molecular, and computational technologies, have enabled dynamic observations from single molecules to whole organisms. Despite technological leaps, there is still an untapped opportunity to fully leverage their capabilities toward biological insight. We highlight how single-molecule imaging has transformed our understanding of biological processes, with a focus on chromatin organization and transcription in the nucleus. We describe how this was enabled by the close integration of new imaging techniques with analysis tools and discuss the challenges to make a comparable impact at larger scales from organelles to organisms. By highlighting recent successful examples, we describe an outlook of ever-increasing data and the need for seamless integration between dataset visualization and quantification to realize the full potential warranted by advances in new imaging technologies.
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Affiliation(s)
- Max A Hockenberry
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, Chapel Hill, NC, USA
| | - Timothy A Daugird
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Wesley R Legant
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Joint Department of Biomedical Engineering, North Carolina State University, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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2
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Moores AN, Uphoff S. Robust Quantification of Live-Cell Single-Molecule Tracking Data for Fluorophores with Different Photophysical Properties. J Phys Chem B 2024; 128:7291-7303. [PMID: 38859654 PMCID: PMC11301680 DOI: 10.1021/acs.jpcb.4c01454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2024]
Abstract
High-speed single-molecule tracking in live cells is becoming an increasingly popular method for quantifying the spatiotemporal behavior of proteins in vivo. The method provides a wealth of quantitative information, but users need to be aware of biases that can skew estimates of molecular mobilities. The range of suitable fluorophores for live-cell single-molecule imaging has grown substantially over the past few years, but it remains unclear to what extent differences in photophysical properties introduce biases. Here, we tested two fluorophores with entirely different photophysical properties, one that photoswitches frequently between bright and dark states (TMR) and one that shows exceptional photostability without photoswitching (JFX650). We used a fusion of the Escherichia coli DNA repair enzyme MutS to the HaloTag and optimized sample preparation and imaging conditions for both types of fluorophore. We then assessed the reliability of two common data analysis algorithms, mean-square displacement (MSD) analysis and Hidden Markov Modeling (HMM), to estimate the diffusion coefficients and fractions of MutS molecules in different states of motion. We introduce a simple approach that removes discrepancies in the data analyses and show that both algorithms yield consistent results, regardless of the fluorophore used. Nevertheless, each dye has its own strengths and weaknesses, with TMR being more suitable for sampling the diffusive behavior of many molecules, while JFX650 enables prolonged observation of only a few molecules per cell. These characterizations and recommendations should help to standardize measurements for increased reproducibility and comparability across studies.
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Affiliation(s)
- Amy N Moores
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, U.K
| | - Stephan Uphoff
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, U.K
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3
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Presman DM, Benítez B, Lafuente AL, Vázquez Lareu A. Chromatin structure and dynamics: one nucleosome at a time. Histochem Cell Biol 2024; 162:79-90. [PMID: 38607419 DOI: 10.1007/s00418-024-02281-1] [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] [Accepted: 03/19/2024] [Indexed: 04/13/2024]
Abstract
Eukaryotic genomes store information on many levels, including their linear DNA sequence, the posttranslational modifications of its constituents (epigenetic modifications), and its three-dimensional folding. Understanding how this information is stored and read requires multidisciplinary collaborations from many branches of science beyond biology, including physics, chemistry, and computer science. Concurrent recent developments in all these areas have enabled researchers to image the genome with unprecedented spatial and temporal resolution. In this review, we focus on what single-molecule imaging and tracking of individual proteins in live cells have taught us about chromatin structure and dynamics. Starting with the basics of single-molecule tracking (SMT), we describe some advantages over in situ imaging techniques and its current limitations. Next, we focus on single-nucleosome studies and what they have added to our current understanding of the relationship between chromatin dynamics and transcription. In celebration of Robert Feulgen's ground-breaking discovery that allowed us to start seeing the genome, we discuss current models of chromatin structure and future challenges ahead.
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Affiliation(s)
- Diego M Presman
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Facultad de Ciencias Exactas y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina.
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina.
| | - Belén Benítez
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Facultad de Ciencias Exactas y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
- Instituto de Química Biológica (IQUIBICEN), Facultad de Ciencias Exactas y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
| | - Agustina L Lafuente
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Facultad de Ciencias Exactas y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
| | - Alejo Vázquez Lareu
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Facultad de Ciencias Exactas y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
- Instituto de Química Biológica (IQUIBICEN), Facultad de Ciencias Exactas y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
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Hwang DW, Maekiniemi A, Singer RH, Sato H. Real-time single-molecule imaging of transcriptional regulatory networks in living cells. Nat Rev Genet 2024; 25:272-285. [PMID: 38195868 DOI: 10.1038/s41576-023-00684-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2023] [Indexed: 01/11/2024]
Abstract
Gene regulatory networks drive the specific transcriptional programmes responsible for the diversification of cell types during the development of multicellular organisms. Although our knowledge of the genes involved in these dynamic networks has expanded rapidly, our understanding of how transcription is spatiotemporally regulated at the molecular level over a wide range of timescales in the small volume of the nucleus remains limited. Over the past few decades, advances in the field of single-molecule fluorescence imaging have enabled real-time behaviours of individual transcriptional components to be measured in living cells and organisms. These efforts are now shedding light on the dynamic mechanisms of transcription, revealing not only the temporal rules but also the spatial coordination of underlying molecular interactions during various biological events.
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Affiliation(s)
- Dong-Woo Hwang
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, USA
| | - Anna Maekiniemi
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, USA
| | - Robert H Singer
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, USA
| | - Hanae Sato
- Department of Cell Biology, Albert Einstein College of Medicine, New York, NY, USA.
- Nano Life Science Institute (WPI-Nano LSI), Kanazawa University, Kakuma-machi, Kanazawa, Japan.
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Dahal L, Graham TGW, Dailey GM, Heckert A, Tjian R, Darzacq X. Surprising Features of Nuclear Receptor Interaction Networks Revealed by Live Cell Single Molecule Imaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.16.558083. [PMID: 37745337 PMCID: PMC10516011 DOI: 10.1101/2023.09.16.558083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Type 2 Nuclear Receptors (T2NRs) require heterodimerization with a common partner, the Retinoid X Receptor (RXR), to bind cognate DNA recognition sites in chromatin. Based on previous biochemical and over-expression studies, binding of T2NRs to chromatin is proposed to be regulated by competition for a limiting pool of the core RXR subunit. However, this mechanism has not yet been tested for endogenous proteins in live cells. Using single molecule tracking (SMT) and proximity-assisted photoactivation (PAPA), we monitored interactions between endogenously tagged retinoid X receptor (RXR) and retinoic acid receptor (RAR) in live cells. Unexpectedly, we find that higher expression of RAR, but not RXR increases heterodimerization and chromatin binding in U2OS cells. This surprising finding indicates the limiting factor is not RXR but likely its cadre of obligate dimer binding partners. SMT and PAPA thus provide a direct way to probe which components are functionally limiting within a complex TF interaction network providing new insights into mechanisms of gene regulation in vivo with implications for drug development targeting nuclear receptors.
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Affiliation(s)
- Liza Dahal
- Department of Molecular and Cell Biology, University of California, Berkeley, United States
- Howard Hughes Medical Institute, University of California, Berkeley, United States
| | - Thomas GW Graham
- Department of Molecular and Cell Biology, University of California, Berkeley, United States
- Howard Hughes Medical Institute, University of California, Berkeley, United States
| | - Gina M Dailey
- Department of Molecular and Cell Biology, University of California, Berkeley, United States
| | - Alec Heckert
- Eikon Therapeutics Inc., Hayward, California, United States
| | - Robert Tjian
- Department of Molecular and Cell Biology, University of California, Berkeley, United States
- Howard Hughes Medical Institute, University of California, Berkeley, United States
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, United States
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West AE. Imaging the binding of MECP2 to DNA. Genes Dev 2023; 37:863-864. [PMID: 37914350 PMCID: PMC10691463 DOI: 10.1101/gad.351285.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Mutations in the methyl-DNA binding domain of MECP2 cause Rett syndrome; however, distinct mutations are associated with different severity of the disease. Live-cell imaging and single-molecule tracking are sensitive methods to quantify the DNA binding affinity and diffusion dynamics of nuclear proteins. In this issue of Genes & Development, Zhou and colleagues (pp. 883-900) used these imaging methods to quantitatively describe the partial loss of DNA binding resulting from a novel pathological MECP2 mutation with intermediate disease severity. These data demonstrate how single-molecule tracking can advance understanding of the molecular mechanisms connecting MECP2 mutations with Rett syndrome pathophysiology.
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Affiliation(s)
- Anne E West
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina 27710, USA
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Oses C, De Rossi MC, Bruno L, Verneri P, Diaz MC, Benítez B, Guberman A, Levi V. From the membrane to the nucleus: mechanical signals and transcription regulation. Biophys Rev 2023; 15:671-683. [PMID: 37681098 PMCID: PMC10480138 DOI: 10.1007/s12551-023-01103-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 07/20/2023] [Indexed: 09/09/2023] Open
Abstract
Mechanical forces drive and modulate a wide variety of processes in eukaryotic cells including those occurring in the nucleus. Relevantly, forces are fundamental during development since they guide lineage specifications of embryonic stem cells. A sophisticated macromolecular machinery transduces mechanical stimuli received at the cell surface into a biochemical output; a key component in this mechanical communication is the cytoskeleton, a complex network of biofilaments in constant remodeling that links the cell membrane to the nuclear envelope. Recent evidence highlights that forces transmitted through the cytoskeleton directly affect the organization of chromatin and the accessibility of transcription-related molecules to their targets in the DNA. Consequently, mechanical forces can directly modulate transcription and change gene expression programs. Here, we will revise the biophysical toolbox involved in the mechanical communication with the cell nucleus and discuss how mechanical forces impact on the organization of this organelle and more specifically, on transcription. We will also discuss how live-cell fluorescence imaging is producing exquisite information to understand the mechanical response of cells and to quantify the landscape of interactions of transcription factors with chromatin in embryonic stem cells. These studies are building new biophysical insights that could be fundamental to achieve the goal of manipulating forces to guide cell differentiation in culture systems.
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Affiliation(s)
- Camila Oses
- Instituto de Química Biológica de La Facultad de Ciencias Exactas Y Naturales (IQUIBICEN), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - María Cecilia De Rossi
- Instituto de Química Biológica de La Facultad de Ciencias Exactas Y Naturales (IQUIBICEN), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - Luciana Bruno
- Facultad de Ciencias Exactas Y Naturales, Instituto de Cálculo (IC), CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - Paula Verneri
- Instituto de Química Biológica de La Facultad de Ciencias Exactas Y Naturales (IQUIBICEN), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - María Candelaria Diaz
- Instituto de Química Biológica de La Facultad de Ciencias Exactas Y Naturales (IQUIBICEN), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - Belén Benítez
- Instituto de Fisiología, Biología Molecular Y Neurociencias (IFIBYNE), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
| | - Alejandra Guberman
- Instituto de Química Biológica de La Facultad de Ciencias Exactas Y Naturales (IQUIBICEN), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
- Facultad de Ciencias Exactas Y Naturales, Departamento de Fisiología, Universidad de Buenos Aires, Biología Molecular Y Celular, C1428EGA Buenos Aires, Argentina
| | - Valeria Levi
- Instituto de Química Biológica de La Facultad de Ciencias Exactas Y Naturales (IQUIBICEN), Facultad de Ciencias Exactas Y Naturales, CONICET-Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
- Facultad de Ciencias Exactas Y Naturales, Departamento de Química Biológica, Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina
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Disatham J, Brennan L, Cvekl A, Kantorow M. Multiomics Analysis Reveals Novel Genetic Determinants for Lens Differentiation, Structure, and Transparency. Biomolecules 2023; 13:693. [PMID: 37189439 PMCID: PMC10136076 DOI: 10.3390/biom13040693] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/13/2023] [Accepted: 04/16/2023] [Indexed: 05/17/2023] Open
Abstract
Recent advances in next-generation sequencing and data analysis have provided new gateways for identification of novel genome-wide genetic determinants governing tissue development and disease. These advances have revolutionized our understanding of cellular differentiation, homeostasis, and specialized function in multiple tissues. Bioinformatic and functional analysis of these genetic determinants and the pathways they regulate have provided a novel basis for the design of functional experiments to answer a wide range of long-sought biological questions. A well-characterized model for the application of these emerging technologies is the development and differentiation of the ocular lens and how individual pathways regulate lens morphogenesis, gene expression, transparency, and refraction. Recent applications of next-generation sequencing analysis on well-characterized chicken and mouse lens differentiation models using a variety of omics techniques including RNA-seq, ATAC-seq, whole-genome bisulfite sequencing (WGBS), chip-seq, and CUT&RUN have revealed a wide range of essential biological pathways and chromatin features governing lens structure and function. Multiomics integration of these data has established new gene functions and cellular processes essential for lens formation, homeostasis, and transparency including the identification of novel transcription control pathways, autophagy remodeling pathways, and signal transduction pathways, among others. This review summarizes recent omics technologies applied to the lens, methods for integrating multiomics data, and how these recent technologies have advanced our understanding ocular biology and function. The approach and analysis are relevant to identifying the features and functional requirements of more complex tissues and disease states.
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Affiliation(s)
- Joshua Disatham
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL 33431, USA; (J.D.); (L.B.)
| | - Lisa Brennan
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL 33431, USA; (J.D.); (L.B.)
| | - Ales Cvekl
- Departments of Ophthalmology and Visual Sciences and Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA;
| | - Marc Kantorow
- Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL 33431, USA; (J.D.); (L.B.)
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