1
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Cho MJ, Kim CE, Shin YH, Kim JK, Pack CG. Influence of Chemical and Genetic Manipulations on Cellular Organelles Quantified by Label-Free Optical Diffraction Tomography. Anal Chem 2023; 95:13478-13487. [PMID: 37523497 DOI: 10.1021/acs.analchem.3c01349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Label-free optical diffraction tomography provides three-dimensional imaging of cells and organelles, along with their refractive index (RI) and volume. These physical parameters are valuable for quantitative and accurate analysis of the subcellular microenvironment and its connections to intracellular biological properties. In biological and biochemical cell analysis, various invasive cell manipulations are used, such as temperature change, chemical fixation, live cell staining with fluorescent dye, and gene overexpression of exogenous proteins. However, it is not fully understood how these various manipulations affect the physicochemical properties of different organelles. In this study, we investigated the impact of these manipulations on the cellular properties of single HeLa cells. We found that after cell fixation and an increase in temperature, the RI value of organelles, such as the nucleus and cytoplasm, significantly decreased overall. Interestingly, unlike the cell nuclei, cytoplasmic RI values were hardly detected after membrane permeation, indicating that only intracytoplasmic components were largely lost. Additionally, our findings revealed that the expression of GFP and GFP-tagged proteins significantly increased the RI values of organelles in living cells compared to the less effective RI changes observed with chemical fluorescence staining for cell organelles. The result demonstrates that distinct types of invasive manipulations can alter the microenvironment of organelles in different ways. Our study sheds new light on how chemical and genetic manipulations affect organelles.
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Affiliation(s)
- Min Ju Cho
- Department of Medical Science, Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
| | - Chae-Eun Kim
- Department of Medical Science, Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
| | - Yeon Hui Shin
- Department of Medical Science, Asan Medical Institute of Convergence Science and Technology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
| | - Jun Ki Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Republic of Korea
- Department of Biomedical Engineering, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
| | - Chan-Gi Pack
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Republic of Korea
- Department of Biomedical Engineering, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
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2
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Hertzog M, Erdel F. The Material Properties of the Cell Nucleus: A Matter of Scale. Cells 2023; 12:1958. [PMID: 37566037 PMCID: PMC10416959 DOI: 10.3390/cells12151958] [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] [Received: 06/30/2023] [Revised: 07/26/2023] [Accepted: 07/26/2023] [Indexed: 08/12/2023] Open
Abstract
Chromatin regulatory processes physically take place in the environment of the cell nucleus, which is filled with the chromosomes and a plethora of smaller biomolecules. The nucleus contains macromolecular assemblies of different sizes, from nanometer-sized protein complexes to micrometer-sized biomolecular condensates, chromosome territories, and nuclear bodies. This multiscale organization impacts the transport processes within the nuclear interior, the global mechanical properties of the nucleus, and the way the nucleus senses and reacts to mechanical stimuli. Here, we discuss recent work on these aspects, including microrheology and micromanipulation experiments assessing the material properties of the nucleus and its subcomponents. We summarize how the properties of multiscale media depend on the time and length scales probed in the experiment, and we reconcile seemingly contradictory observations made on different scales. We also revisit the concept of liquid-like and solid-like material properties for complex media such as the nucleus. We propose that the nucleus can be considered a multiscale viscoelastic medium composed of three major components with distinct properties: the lamina, the chromatin network, and the nucleoplasmic fluid. This multicomponent organization enables the nucleus to serve its different functions as a reaction medium on the nanoscale and as a mechanosensor and structural scaffold on the microscale.
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Affiliation(s)
| | - Fabian Erdel
- MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, 169 Avenue Marianne Grunberg-Manago, 31062 Toulouse, France
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3
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Yewdall NA, André AAM, van Haren MHI, Nelissen FHT, Jonker A, Spruijt E. ATP:Mg 2+ shapes material properties of protein-RNA condensates and their partitioning of clients. Biophys J 2022; 121:3962-3974. [PMID: 36004782 PMCID: PMC9674983 DOI: 10.1016/j.bpj.2022.08.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 07/29/2022] [Accepted: 08/19/2022] [Indexed: 11/26/2022] Open
Abstract
Many cellular condensates are heterotypic mixtures of proteins and RNA formed in complex environments. Magnesium ions (Mg2+) and ATP can impact RNA folding, and local intracellular levels of these factors can vary significantly. However, the effect of ATP:Mg2+ on the material properties of protein-RNA condensates is largely unknown. Here, we use an in vitro condensate model of nucleoli, made from nucleophosmin 1 (NPM1) proteins and ribosomal RNA (rRNA), to study the effect of ATP:Mg2+. While NPM1 dynamics remain unchanged at increasing Mg2+ concentrations, the internal RNA dynamics dramatically slowed until a critical point, where gel-like states appeared, suggesting the RNA component alone forms a viscoelastic network that undergoes maturation driven by weak multivalent interactions. ATP reverses this arrest and liquefies the gel-like structures. ATP:Mg2+ also influenced the NPM1-rRNA composition of condensates and enhanced the partitioning of two clients: an arginine-rich peptide and a small nuclear RNA. By contrast, larger ribosome partitioning shows dependence on ATP:Mg2+ and can become reversibly trapped around NPM1-rRNA condensates. Lastly, we show that dissipative enzymatic reactions that deplete ATP can be used to control the shape, composition, and function of condensates. Our results illustrate how intracellular environments may regulate the state and client partitioning of RNA-containing condensates.
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Affiliation(s)
- N Amy Yewdall
- Institute for Molecules and Materials, Radboud University, Nijmegen, the Netherlands.
| | - Alain A M André
- Institute for Molecules and Materials, Radboud University, Nijmegen, the Netherlands
| | - Merlijn H I van Haren
- Institute for Molecules and Materials, Radboud University, Nijmegen, the Netherlands
| | - Frank H T Nelissen
- Institute for Molecules and Materials, Radboud University, Nijmegen, the Netherlands
| | - Aafke Jonker
- Institute for Molecules and Materials, Radboud University, Nijmegen, the Netherlands
| | - Evan Spruijt
- Institute for Molecules and Materials, Radboud University, Nijmegen, the Netherlands.
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4
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Chiu YF, Huang YW, Chen CY, Chen YC, Gong YN, Kuo RL, Huang CG, Shih SR. Visualizing Influenza A Virus vRNA Replication. Front Microbiol 2022; 13:812711. [PMID: 35733972 PMCID: PMC9207383 DOI: 10.3389/fmicb.2022.812711] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 04/05/2022] [Indexed: 11/13/2022] Open
Abstract
Influenza A virus (IAV) has caused recurrent epidemics and severe pandemics. In this study, we adapted an MS2-MCP live-cell imaging system to visualize IAV replication. A reporter plasmid, pHH-PB2-vMSL, was constructed by replacing a part of the PB2-coding sequence in pHH-PB2 with a sequence encoding 24 copies of a stem-loop structure from bacteriophage MS2 (MSL). Binding of MS2 coat protein (MCP) fused to green fluorescent protein (GFP) to MSL enabled the detection of vRNA as fluorescent punctate signals in live-cell imaging. The introduction of pHH-PB2-vMSL into A549 cells transduced to express an MCP-GFP fusion protein lacking the nuclear localization signal (MCP-GFPdN), subsequently allowed tracking of the distribution and replication of PB2-vMSL vRNA after IAV PR8 infection. Spatial and temporal measurements revealed exponential increases in vRNA punctate signal intensity, which was only observed after membrane blebbing in apoptotic cells. Similar signal intensity increases in apoptotic cells were also observed after MDCK cells, transduced to express MCP-GFPdN, were infected with IAV carrying PB2-vMSL vRNA. Notably, PB2-vMSL vRNA replication was observed to occur only in apoptotic cells, at a consistent time after apoptosis initiation. There was a lack of observable PB2-vMSL vRNA replication in non-apoptotic cells, and vRNA replication was suppressed in the presence of apoptosis inhibitors. These findings point to an important role for apoptosis in IAV vRNA replication. The utility of the MS2-imaging system for visualizing time-sensitive processes such as viral replication in live host cells is also demonstrated in this study.
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Affiliation(s)
- Ya-Fang Chiu
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan.,Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan.,Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Yi-Wen Huang
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
| | - Chi-Yuan Chen
- Department of Microbiology and Immunology, Chang Gung University, Taoyuan, Taiwan
| | - Yu-Chia Chen
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan
| | - Yu-Nong Gong
- Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan.,Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Rei-Lin Kuo
- Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan
| | - Chung-Guei Huang
- Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Shin-Ru Shih
- Research Center for Emerging Viral Infections, Chang Gung University, Taoyuan, Taiwan
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5
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Pack CG. Application of quantitative cell imaging using label-free optical diffraction tomography. Biophys Physicobiol 2021; 18:244-253. [PMID: 34745809 PMCID: PMC8550874 DOI: 10.2142/biophysico.bppb-v18.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 10/11/2021] [Indexed: 12/01/2022] Open
Abstract
The cell is three-dimensionally and dynamically organized into cellular compartments, including the endoplasmic reticulum, mitochondria, vesicles, and nucleus, which have high relative molecular density. The structure and functions of these compartments and organelles may be deduced from the diffusion and interaction of related biomolecules. Among these cellular components, various protein molecules can freely access the nucleolus or mitotic chromosome through Brownian diffusion, even though they have a densely packed structure. However, physicochemical properties of the nucleolus and chromosomes, such as molecular density and volume, are not yet fully understood under changing cellular conditions. Many studies have been conducted based on high-resolution imaging and analysis techniques using fluorescence. However, there are limitations in imaging only fluorescently labeled molecules, and cytotoxicity occurs during three-dimensional imaging. Alternatively, the recently developed label-free three-dimensional optical diffraction tomography (ODT) imaging technique can divide various organelles in cells into volumes and analyze them by refractive index, although specific molecules cannot be observed. A previous study established an analytical method that provides comprehensive insights into the physical properties of the nucleolus and mitotic chromosome by utilizing the advantages of ODT and fluorescence techniques, such as fluorescence correlation spectroscopy and confocal laser scanning microscopy. This review article summarizes a recent study and discusses the future aspects of the ODT for cellular compartments.
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Affiliation(s)
- Chan-Gi Pack
- Convergence Medicine Research Center (CREDIT), Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Republic of Korea.,Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
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6
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Mobility of Nucleostemin in Live Cells Is Specifically Related to Transcription Inhibition by Actinomycin D and GTP-Binding Motif. Int J Mol Sci 2021; 22:ijms22158293. [PMID: 34361059 PMCID: PMC8347349 DOI: 10.3390/ijms22158293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 07/24/2021] [Accepted: 07/29/2021] [Indexed: 12/04/2022] Open
Abstract
In vertebrates, nucleostemin (NS) is an important marker of proliferation in several types of stem and cancer cells, and it can also interact with the tumor-suppressing transcription factor p53. In the present study, the intra-nuclear diffusional dynamics of native NS tagged with GFP and two GFP-tagged NS mutants with deleted guanosine triphosphate (GTP)-binding domains were analyzed by fluorescence correlation spectroscopy. Free and slow binding diffusion coefficients were evaluated, either under normal culture conditions or under treatment with specific cellular proliferation inhibitors actinomycin D (ActD), 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), or trichostatin A (TSA). When treated with ActD, the fractional ratio of the slow diffusion was significantly decreased in the nucleoplasm. The decrease was proportional to ActD treatment duration. In contrast, DRB or TSA treatment did not affect NS diffusion. Interestingly, it was also found that the rate of diffusion of two NS mutants increased significantly even under normal conditions. These results suggest that the mobility of NS in the nucleoplasm is related to the initiation of DNA or RNA replication, and that the GTP-binding motif is also related to the large change of mobility.
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7
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Yoshizawa R, Umeki N, Yamamoto A, Murata M, Sako Y. Biphasic spatiotemporal regulation of GRB2 dynamics by p52SHC for transient RAS activation. Biophys Physicobiol 2021; 18:1-12. [PMID: 33665062 PMCID: PMC7902154 DOI: 10.2142/biophysico.bppb-v18.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/05/2021] [Indexed: 12/14/2022] Open
Abstract
RTK-RAS-MAPK systems are major signaling pathways for cell fate decisions. Among the several RTK species, it is known that the transient activation of ERK (MAPK) stimulates cell proliferation, whereas its sustained activation induces cell differentiation. In both instances however, RAS activation is transient, suggesting that the strict temporal regulation of its activity is critical in normal cells. RAS on the cytoplasmic side of the plasma membrane is activated by SOS through the recruitment of GRB2/SOS complex to the RTKs that are phosphorylated after stimulation with growth factors. The adaptor protein GRB2 recognizes phospho-RTKs both directly and indirectly via another adaptor protein, SHC. We here studied the regulation of GRB2 recruitment under the SHC pathway using single-molecule imaging and fluorescence correlation spectroscopy in living cells. We stimulated MCF7 cells with a differentiation factor, heregulin, and observed the translocation, complex formation, and phosphorylation of cell signaling molecules including GRB2 and SHC. Our results suggest a biphasic regulation of the GRB2/SOS-RAS pathway by SHC: At the early stage (<10 min) of stimulation, SHC increased the amplitude of RAS activity by increasing the association sites for the GRB2/SOS complex on the plasma membrane. At the later stage however, SHC suppressed RAS activation and sequestered GRB2 molecules from the membrane through the complex formation in the cytoplasm. The latter mechanism functions additively to other mechanisms of negative feedback regulation of RAS from MEK and/or ERK to complete the transient activation dynamics of RAS.
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Affiliation(s)
- Ryo Yoshizawa
- Cellular Informatics Lab, RIKEN, Wako, Saitama 351-0198, Japan.,Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Nobuhisa Umeki
- Cellular Informatics Lab, RIKEN, Wako, Saitama 351-0198, Japan
| | | | - Masayuki Murata
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Yasushi Sako
- Cellular Informatics Lab, RIKEN, Wako, Saitama 351-0198, Japan
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8
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Confocal Laser Scanning Microscopy and Fluorescence Correlation Methods for the Evaluation of Molecular Interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1310:1-30. [PMID: 33834430 DOI: 10.1007/978-981-33-6064-8_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Confocal laser scanning microscopy (CLSM) and related microscopic techniques allow a unique and versatile approach to image and analyze living cells due to their specificity and high sensitivity. Among confocal related techniques, fluorescence correlation methods, such as fluorescence correlation spectroscopy (FCS) and dual-color fluorescence cross-correlation spectroscopy (FCCS), are highly sensitive biophysical methods for analyzing the complex dynamic events of molecular diffusion and interaction change in live cells as well as in solution by exploiting the characteristics of fluorescence signals. Analytical and quantitative information from FCS and FCCS coupled with fluorescence images obtained from CLSM can now be applied in convergence science such as drug delivery and nanomedicine, as well as in basic cell biology. In this chapter, a brief introduction into the physical parameters that can be obtained from FCS and FCCS is first provided. Secondly, experimental examples of the methods for evaluating the parameters is presented. Finally, two potential FCS and FCCS applications for convergence science are introduced in more detail.
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9
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Cho HW, Kim H, Sung BJ, Kim JS. Tracer Diffusion in Tightly-Meshed Homogeneous Polymer Networks: A Brownian Dynamics Simulation Study. Polymers (Basel) 2020; 12:E2067. [PMID: 32932910 PMCID: PMC7569880 DOI: 10.3390/polym12092067] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/07/2020] [Accepted: 09/09/2020] [Indexed: 12/02/2022] Open
Abstract
We report Brownian dynamics simulations of tracer diffusion in regularly crosslinked polymer networks in order to elucidate the transport of a tracer particle in polymer networks. The average mesh size of homogeneous polymer networks is varied by assuming different degrees of crosslinking or swelling, and the size of a tracer particle is comparable to the average mesh size. Simulation results show subdiffusion of a tracer particle at intermediate time scales and normal diffusion at long times. In particular, the duration of subdiffusion is significantly prolonged as the average mesh size decreases with increasing degree of crosslinking, for which long-time diffusion occurs via the hopping processes of a tracer particle after undergoing rattling motions within a cage of the network mesh for an extended period of time. On the other hand, the cage dynamics and hopping process are less pronounced as the mesh size decreases with increasing polymer volume fractions. The interpretation is provided in terms of fluctuations in network mesh size: at higher polymer volume fractions, the network fluctuations are large enough to allow for collective, structural changes of network meshes, so that a tracer particle can escape from the cage, whereas, at lower volume fractions, the fluctuations are so small that a tracer particle remains trapped within the cage for a significant period of time before making infrequent jumps out of the cage. This work suggests that fluctuation in mesh size, as well as average mesh size itself, plays an important role in determining the dynamics of molecules and nanoparticles that are embedded in tightly meshed polymer networks.
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Affiliation(s)
- Hyun Woo Cho
- Department of Chemistry, Sogang University, Seoul 04107, Korea;
| | - Haein Kim
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Korea;
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Korea;
| | - Jun Soo Kim
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Korea;
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10
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Frank L, Rippe K. Repetitive RNAs as Regulators of Chromatin-Associated Subcompartment Formation by Phase Separation. J Mol Biol 2020; 432:4270-4286. [DOI: 10.1016/j.jmb.2020.04.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 04/14/2020] [Accepted: 04/14/2020] [Indexed: 12/21/2022]
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11
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Kim TK, Lee BW, Fujii F, Lee KH, Lee S, Park Y, Kim JK, Lee SW, Pack CG. Mitotic Chromosomes in Live Cells Characterized Using High-Speed and Label-Free Optical Diffraction Tomography. Cells 2019; 8:cells8111368. [PMID: 31683735 PMCID: PMC6912651 DOI: 10.3390/cells8111368] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/21/2019] [Accepted: 10/30/2019] [Indexed: 12/16/2022] Open
Abstract
The cell nucleus is a three-dimensional, dynamic organelle organized into subnuclear compartments such as chromatin and nucleoli. The structure and function of these compartments are maintained by diffusion and interactions between related factors as well as by dynamic and structural changes. Recent studies using fluorescent microscopic techniques suggest that protein factors can access and are freely mobile in heterochromatin and in mitotic chromosomes, despite their densely packed structure. However, the physicochemical properties of the chromosome during cell division are not fully understood. In the present study, characteristic properties such as the refractive index (RI), volume of the mitotic chromosomes, and diffusion coefficient (D) of fluorescent probes inside the chromosome were quantified using an approach combining label-free optical diffraction tomography with complementary confocal laser-scanning microscopy and fluorescence correlation spectroscopy. Variations in these parameters correlated with osmotic conditions, suggesting that changes in RI are consistent with those of the diffusion coefficient for mitotic chromosomes and cytosol. Serial RI tomography images of chromosomes in live cells during mitosis were compared with three-dimensional confocal micrographs to demonstrate that compaction and decompaction of chromosomes induced by osmotic change were characterized by linked changes in chromosome RI, volume, and the mobilities of fluorescent proteins.
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Affiliation(s)
- Tae-Keun Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
| | - Byong-Wook Lee
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
| | - Fumihiko Fujii
- Division of Physical Pharmacy, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Kobe 650-8586, Japan.
| | | | - Sanghwa Lee
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
| | - YongKeun Park
- Tomocube Inc., Daejeon 34051, Korea.
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea.
| | - Jun Ki Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
- Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Korea.
| | - Sang-Wook Lee
- Department of Radiation Oncology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 05505, Korea.
| | - Chan-Gi Pack
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
- Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Korea.
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12
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Kim TK, Lee BW, Fujii F, Kim JK, Pack CG. Physicochemical Properties of Nucleoli in Live Cells Analyzed by Label-Free Optical Diffraction Tomography. Cells 2019; 8:cells8070699. [PMID: 31295945 PMCID: PMC6679011 DOI: 10.3390/cells8070699] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/27/2019] [Accepted: 07/09/2019] [Indexed: 12/15/2022] Open
Abstract
The cell nucleus is three-dimensionally and dynamically organized by nuclear components with high molecular density, such as chromatin and nuclear bodies. The structure and functions of these components are represented by the diffusion and interaction of related factors. Recent studies suggest that the nucleolus can be assessed using various protein probes, as the probes are highly mobile in this organelle, although it is known that they have a densely packed structure. However, physicochemical properties of the nucleolus itself, such as molecular density and volume when cellular conditions are changed, are not yet fully understood. In this study, physical parameters such as the refractive index (RI) and volume of the nucleoli in addition to the diffusion coefficient (D) of fluorescent probe protein inside the nucleolus are quantified and compared by combining label-free optical diffraction tomography (ODT) with confocal laser scanning microscopy (CLSM)-based fluorescence correlation spectroscopy (FCS). 3D evaluation of RI values and corresponding RI images of nucleoli in live HeLa cells successfully demonstrated varying various physiological conditions. Our complimentary method suggests that physical property of the nucleolus in live cell is sensitive to ATP depletion and transcriptional inhibition, while it is insensitive to hyper osmotic pressure when compared with the cytoplasm and nucleoplasm. The result demonstrates that the nucleolus has unique physicochemical properties when compared with other cellular components.
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Affiliation(s)
- Tae-Keun Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea
| | - Byong-Wook Lee
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea
| | - Fumihiko Fujii
- Division of Physical Pharmacy, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Kobe 650-8586, Japan
| | - Jun Ki Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
- Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Korea.
| | - Chan-Gi Pack
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
- Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Korea.
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13
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Di Bona M, Mancini MA, Mazza D, Vicidomini G, Diaspro A, Lanzanò L. Measuring Mobility in Chromatin by Intensity-Sorted FCS. Biophys J 2019; 116:987-999. [PMID: 30819566 PMCID: PMC6428914 DOI: 10.1016/j.bpj.2019.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/14/2019] [Accepted: 02/08/2019] [Indexed: 12/12/2022] Open
Abstract
The architectural organization of chromatin can play an important role in genome regulation by affecting the mobility of molecules within its surroundings via binding interactions and molecular crowding. The diffusion of molecules at specific locations in the nucleus can be studied by fluorescence correlation spectroscopy (FCS), a well-established technique based on the analysis of fluorescence intensity fluctuations detected in a confocal observation volume. However, detecting subtle variations of mobility between different chromatin regions remains challenging with currently available FCS methods. Here, we introduce a method that samples multiple positions by slowly scanning the FCS observation volume across the nucleus. Analyzing the data in short time segments, we preserve the high temporal resolution of single-point FCS while probing different nuclear regions in the same cell. Using the intensity level of the probe (or a DNA marker) as a reference, we efficiently sort the FCS segments into different populations and obtain average correlation functions that are associated to different chromatin regions. This sorting and averaging strategy renders the method statistically robust while preserving the observation of intranuclear variations of mobility. Using this approach, we quantified diffusion of monomeric GFP in high versus low chromatin density regions. We found that GFP mobility was reduced in heterochromatin, especially within perinucleolar heterochromatin. Moreover, we found that modulation of chromatin compaction by ATP depletion, or treatment with solutions of different osmolarity, differentially affected the ratio of diffusion in both regions. Then, we used the approach to probe the mobility of estrogen receptor-α in the vicinity of an integrated multicopy prolactin gene array. Finally, we discussed the coupling of this method with stimulated emission depletion FCS for performing FCS at subdiffraction spatial scales.
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Affiliation(s)
- Melody Di Bona
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, Italy; Department of Physics, University of Genoa, Genoa, Italy
| | - Michael A Mancini
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas
| | - Davide Mazza
- Experimental Imaging Center Ospedale San Raffaele, Milano, Italy; The European Center for Nanomedicine, Milano, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Alberto Diaspro
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, Italy; Department of Physics, University of Genoa, Genoa, Italy.
| | - Luca Lanzanò
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, Italy.
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14
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Scipioni L, Lanzanó L, Diaspro A, Gratton E. Comprehensive correlation analysis for super-resolution dynamic fingerprinting of cellular compartments using the Zeiss Airyscan detector. Nat Commun 2018; 9:5120. [PMID: 30504919 PMCID: PMC6269422 DOI: 10.1038/s41467-018-07513-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/29/2018] [Indexed: 11/08/2022] Open
Abstract
The availability of the Airyscan detector in the Zeiss LSM 880 has made possible the development of a new concept in fluctuation correlation spectroscopy using super-resolution. The Airyscan unit acquires data simultaneously on 32 detectors arranged in a hexagonal array. This detector opens up the possibility to use fluctuation methods based on time correlation at single points or at a number of points simultaneously, as well as methods based on spatial correlation in the area covered by the detector. Given the frame rate of this detector, millions of frames can be acquired in seconds, providing a robust statistical basis for fluctuation data. We apply the comprehensive analysis to the molecular fluctuations of free GFP diffusing in live cells at different subcellular compartments to show that at the nanoscale different cell environments can be distinguished by the comprehensive fluctuation analysis.
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Affiliation(s)
- L Scipioni
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, 92697, CA, USA
| | - L Lanzanó
- Nanoscopy, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - A Diaspro
- Nanoscopy, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
- Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - E Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, 92697, CA, USA.
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Scipioni L, Di Bona M, Vicidomini G, Diaspro A, Lanzanò L. Local raster image correlation spectroscopy generates high-resolution intracellular diffusion maps. Commun Biol 2018; 1:10. [PMID: 30271897 PMCID: PMC6053083 DOI: 10.1038/s42003-017-0010-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 12/15/2017] [Indexed: 01/01/2023] Open
Abstract
Raster image correlation spectroscopy (RICS) is a powerful method for measuring molecular diffusion in live cells directly from images acquired on a laser scanning microscope. However, RICS only provides single average diffusion coefficients from regions with a lateral size on the order of few micrometers, which means that its spatial resolution is mainly limited to the cellular level. Here we introduce the local RICS (L-RICS), an easy-to-use tool that generates high resolution maps of diffusion coefficients from images acquired on a laser scanning microscope. As an application we show diffusion maps of a green fluorescent protein (GFP) within the nucleus and within the nucleolus of live cells at an effective spatial resolution of 500 nm. We find not only that diffusion in the nucleolus is slowed down compared to diffusion in the nucleoplasm, but also that diffusion in the nucleolus is highly heterogeneous. Lorenzo Scipioni et al. present Local Raster Image Correlation Spectroscopy (L-RICS), a method for generating sub-micrometer diffusion maps. They apply L-RICS to GFP in live cells and find that diffusion coefficients differ between the nucleus and nucleolus and are highly heterogeneous within compartments.
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Affiliation(s)
- Lorenzo Scipioni
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.,Department of Informatics, Bioengineering, Robotics and Systems Engineering, University of Genoa, Via All'Opera Pia, 13, 16145, Genoa, Italy
| | - Melody Di Bona
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.,Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Alberto Diaspro
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.,Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy.,Nikon Imaging Center, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Luca Lanzanò
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.
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