1
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Zülske T, Attou A, Groß L, Hörl D, Harz H, Wedemann G. Nucleosome spacing controls chromatin spatial structure and accessibility. Biophys J 2024; 123:847-857. [PMID: 38419332 PMCID: PMC10995425 DOI: 10.1016/j.bpj.2024.02.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 01/31/2024] [Accepted: 02/26/2024] [Indexed: 03/02/2024] Open
Abstract
Recent research highlights the significance of the three-dimensional structure of chromatin in regulating various cellular processes, particularly transcription. This is achieved through dynamic chromatin structures that facilitate long-range contacts and control spatial accessibility. Chromatin consists of DNA and a variety of proteins, of which histones play an essential structural role by forming nucleosomes. Extensive experimental and theoretical research in recent decades has yielded conflicting results about key factors that regulate the spatial structure of chromatin, which remains enigmatic. By using a computer model that allows us to simulate chromatin volumes containing physiological nucleosome concentrations, we investigated whether nucleosome spacing or nucleosome density is fundamental for three-dimensional chromatin accessibility. Unexpectedly, the regularity of the nucleosome spacing is crucial for determining the accessibility of the chromatin network to diffusive processes, whereas variation in nucleosome concentrations has only minor effects. Using only the basic physical properties of DNA and nucleosomes was sufficient to generate chromatin structures consistent with published electron microscopy data. Contrary to other work, we found that nucleosome density did not substantially alter the properties of chromatin fibers or contact probabilities of genomic loci. No breakup of fiber-like structures was observed at high molar density. These findings challenge previous assumptions and highlight the importance of nucleosome spacing as a key driver of chromatin organization. These results identified changes in nucleosome spacing as a tentative mechanism for altering the spatial chromatin structure and thus genomic functions.
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Affiliation(s)
- Tilo Zülske
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany
| | - Aymen Attou
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany; Human Biology & BioImaging, Faculty of Biology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Laurens Groß
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany
| | - David Hörl
- Human Biology & BioImaging, Faculty of Biology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Hartmann Harz
- Human Biology & BioImaging, Faculty of Biology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Gero Wedemann
- Competence Center Bioinformatics, Institute for Applied Computer Science, Hochschule Stralsund, Stralsund, Germany.
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2
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Rancu A, Chen CX, Price H, Wax A. Multiscale optical phase fluctuations link disorder strength and fractal dimension of cell structure. Biophys J 2023; 122:1390-1399. [PMID: 36872604 PMCID: PMC10111344 DOI: 10.1016/j.bpj.2023.03.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 02/06/2023] [Accepted: 03/02/2023] [Indexed: 03/07/2023] Open
Abstract
Optical methods for examining cellular structure based on endogenous contrast rely on analysis of refractive index changes to discriminate cell phenotype. These changes can be visualized using techniques such as phase contrast microscopy, detected by light scattering, or analyzed numerically using quantitative phase imaging. The statistical variations of refractive index at the nanoscale can be quantified using disorder strength, a metric seen to increase with neoplastic change. In contrast, the spatial organization of these variations is typically characterized using a fractal dimension, which is also seen to increase with cancer progression. Here, we seek to link these two measurements using multiscale measurements of optical phase to calculate disorder strength and in turn to determine the fractal dimension of the structures. First, quantitative phase images are analyzed to show that the disorder strength metric changes with resolution. The trend of disorder strength with length scales is analyzed to determine the fractal dimension of the cellular structures. Comparison of these metrics is presented for different cell lines with varying phenotypes including MCF10A, MCF7, BT474, HT-29, A431, and A549 cell lines, in addition to three cell populations with modified phenotypes. Our results show that disorder strength and fractal dimension can both be obtained with quantitative phase imaging and that these metrics can independently distinguish between different cell lines. Furthermore, their combined use presents a new approach for better understanding cellular restructuring during different pathways.
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Affiliation(s)
- Albert Rancu
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Cindy X Chen
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Hillel Price
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Adam Wax
- Department of Biomedical Engineering, Duke University, Durham, North Carolina.
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3
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Grigoriev SV, Iashina EG, Wu B, Pipich V, Lang C, Radulescu A, Bairamukov VY, Filatov MV, Pantina RA, Varfolomeeva EY. Observation of nucleic acid and protein correlation in chromatin of HeLa nuclei using small-angle neutron scattering with D_{2}O-H_{2}O contrast variation. Phys Rev E 2021; 104:044404. [PMID: 34781557 DOI: 10.1103/physreve.104.044404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 08/30/2021] [Indexed: 01/06/2023]
Abstract
The small-angle neutron scattering (SANS) on HeLa nuclei demonstrates the bifractal nature of the chromatin structural organization. The border line between two fractal structures is detected as a crossover point at Q_{c}≈4×10^{-2}nm^{-1} in the momentum transfer dependence Q^{-D}. The use of contrast variation (D_{2}O-H_{2}O) in SANS measurements reveals clear similarity in the large scale structural organizations of nucleic acids (NA) and proteins. Both NA and protein structures have a mass fractal arrangement with the fractal dimension of D≈2.5 at scales smaller than 150 nm down to 20 nm. Both NA and proteins show a logarithmic fractal behavior with D≈3 at scales larger than 150 nm up to 6000 nm. The combined analysis of the SANS and atomic force microscopy data allows one to conclude that chromatin and its constitutes (DNA and proteins) are characterized as soft, densely packed, logarithmic fractals on the large scale and as rigid, loosely packed, mass fractals on the smaller scale. The comparison of the partial cross sections from NA and proteins with one from chromatin as a whole demonstrates spatial correlation of two chromatin's components in the range up to 900 nm. Thus chromatin in HeLa nuclei is built as the unified structure of the NA and proteins entwined through each other. Correlation between two components is lost upon scale increases toward 6000 nm. The structural features at the large scale, probably, provide nuclei with the flexibility and chromatin-free space to build supercorrelations on the distance of 10^{3} nm resembling cycle cell activity, such as an appearance of nucleoli and a DNA replication.
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Affiliation(s)
- S V Grigoriev
- Petersburg Nuclear Physics Institute named by B.P.Konstantinov of NRC Kurchatov Institute, Gatchina, St-Petersburg 188300, Russia.,Saint-Petersburg State University, Ulyanovskaya 1, Saint-Petersburg 198504, Russia
| | - E G Iashina
- Petersburg Nuclear Physics Institute named by B.P.Konstantinov of NRC Kurchatov Institute, Gatchina, St-Petersburg 188300, Russia.,Saint-Petersburg State University, Ulyanovskaya 1, Saint-Petersburg 198504, Russia
| | - B Wu
- Forschungszentrum Juelich, JCNS-4 at MLZ, Lichtenbergstr. 1, 85748 Garching, Germany
| | - V Pipich
- Forschungszentrum Juelich, JCNS-4 at MLZ, Lichtenbergstr. 1, 85748 Garching, Germany
| | - Ch Lang
- Forschungszentrum Juelich, JCNS-4 at MLZ, Lichtenbergstr. 1, 85748 Garching, Germany
| | - A Radulescu
- Forschungszentrum Juelich, JCNS-4 at MLZ, Lichtenbergstr. 1, 85748 Garching, Germany
| | - V Yu Bairamukov
- Petersburg Nuclear Physics Institute named by B.P.Konstantinov of NRC Kurchatov Institute, Gatchina, St-Petersburg 188300, Russia
| | - M V Filatov
- Petersburg Nuclear Physics Institute named by B.P.Konstantinov of NRC Kurchatov Institute, Gatchina, St-Petersburg 188300, Russia
| | - R A Pantina
- Petersburg Nuclear Physics Institute named by B.P.Konstantinov of NRC Kurchatov Institute, Gatchina, St-Petersburg 188300, Russia
| | - E Yu Varfolomeeva
- Petersburg Nuclear Physics Institute named by B.P.Konstantinov of NRC Kurchatov Institute, Gatchina, St-Petersburg 188300, Russia
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4
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Pettinato G, Coughlan MF, Zhang X, Chen L, Khan U, Glyavina M, Sheil CJ, Upputuri PK, Zakharov YN, Vitkin E, D’Assoro AB, Fisher RA, Itzkan I, Zhang L, Qiu L, Perelman LT. Spectroscopic label-free microscopy of changes in live cell chromatin and biochemical composition in transplantable organoids. Sci Adv 2021; 7:7/34/eabj2800. [PMID: 34407934 PMCID: PMC8373132 DOI: 10.1126/sciadv.abj2800] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 06/30/2021] [Indexed: 02/01/2023]
Abstract
Organoids formed from human induced pluripotent stem cells (hiPSCs) could be a limitless source of functional tissue for transplantations in many organs. Unfortunately, fine-tuning differentiation protocols to form large quantities of hiPSC organoids in a controlled, scalable, and reproducible manner is quite difficult and often takes a very long time. Recently, we introduced a new approach of rapid organoid formation from dissociated hiPSCs and endothelial cells using microfabricated cell-repellent microwell arrays. This approach, when combined with real-time label-free Raman spectroscopy of biochemical composition changes and confocal light scattering spectroscopic microscopy of chromatin transition, allows for monitoring live differentiating organoids without the need to sacrifice a sample, substantially shortening the time of protocol fine-tuning. We used this approach to both culture and monitor homogeneous liver organoids that have the main functional features of the human liver and which could be used for cell transplantation liver therapy in humans.
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Affiliation(s)
- Giuseppe Pettinato
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Mark F. Coughlan
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Xuejun Zhang
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Liming Chen
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Umar Khan
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Maria Glyavina
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Conor J. Sheil
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Paul K. Upputuri
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Yuri N. Zakharov
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Edward Vitkin
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | | | - Robert A. Fisher
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Irving Itzkan
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA
| | - Lei Zhang
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA.,Corresponding author. (L.Z.); (L.Q.); (L.T.P.)
| | - Le Qiu
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA.,Corresponding author. (L.Z.); (L.Q.); (L.T.P.)
| | - Lev T. Perelman
- Center for Advanced Biomedical Imaging and Photonics, Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA.,Biological and Biomedical Sciences Program, Harvard University, Cambridge, MA, USA.,Corresponding author. (L.Z.); (L.Q.); (L.T.P.)
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5
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Arifler D, Guillaud M. Assessment of internal refractive index profile of stochastically inhomogeneous nuclear models via analysis of two-dimensional optical scattering patterns. J Biomed Opt 2021; 26:JBO-200345RR. [PMID: 33973424 PMCID: PMC8107832 DOI: 10.1117/1.jbo.26.5.055001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 04/22/2021] [Indexed: 06/12/2023]
Abstract
SIGNIFICANCE Optical scattering signals obtained from tissue constituents contain a wealth of structural information. Conventional intensity features, however, are mostly dictated by the overall morphology and mean refractive index of these constituents, making it very difficult to exclusively sense internal refractive index fluctuations. AIM We perform a systematic analysis to elucidate how changes in internal refractive index profile of cell nuclei can best be detected via optical scattering. APPROACH We construct stochastically inhomogeneous nuclear models and numerically simulate their azimuth-resolved scattering patterns. We then process these two-dimensional patterns with the goal of identifying features that directly point to subnuclear structure. RESULTS Azimuth-dependent intensity variations over the side scattering range provide significant insights into subnuclear refractive index profile. A particular feature we refer to as contrast ratio is observed to be highly sensitive to the length scale and extent of refractive index fluctuations; further, this feature is not susceptible to changes in the overall size and mean refractive index of nuclei, thereby allowing for selective tracking of subnuclear structure that can be linked to chromatin distribution. CONCLUSIONS Our analysis will potentially pave the way for scattering-based assessment of chromatin reorganization that is considered to be a key hallmark of precancer progression.
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Affiliation(s)
- Dizem Arifler
- Middle East Technical University, Northern Cyprus Campus, Physics Group, Kalkanli, Turkey
| | - Martial Guillaud
- British Columbia Cancer Research Center, Department of Integrative Oncology, Imaging Unit, Vancouver BC, Canada
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6
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Dinčić M, Todorović J, Nešović Ostojić J, Kovačević S, Dunđerović D, Lopičić S, Spasić S, Radojević-Škodrić S, Stanisavljević D, Ilić AŽ. The Fractal and GLCM Textural Parameters of Chromatin May Be Potential Biomarkers of Papillary Thyroid Carcinoma in Hashimoto's Thyroiditis Specimens. Microsc Microanal 2020; 26:717-730. [PMID: 32588793 DOI: 10.1017/s1431927620001683] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Occasionally, Hashimoto's thyroiditis (HT) and papillary thyroid carcinoma (PTC) share similar nuclear features. The current study aims to quantify the differences between the investigated specimens of HT-associated PTC versus the HT alone, to reduce the subjective experience of an observer, by the use of fractal parameters as well as gray-level co-occurrence matrix (GLCM) textural parameters. We have analyzed 250 segmented nuclei per group (nn = 25 per patient and np = 10 patients per group) using the ImageJ software (NIH, Bethesda, MD, USA) as well as an in-house written code for the GLCM analysis. The mean values of parameters were calculated for each patient. The results demonstrated that the malignant cells from the HT-associated PTC specimens showed lower chromatin fractal dimension (p = 0.0321) and higher lacunarity (p = 0.0038) compared with the corresponding cells from the HT specimens. Also, there was a statistically significant difference between the investigated specimens, in the contrast, correlation, angular second moment, and homogeneity, of the GLCM corresponding to the visual texture of follicular cell chromatin. The differences in chromatin fractal and GLCM parameters could be integrated with other diagnostic methods for the improved evaluation of distinctive features of the HT-associated PTC versus the HT in cytology and surgical pathology specimens.
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Affiliation(s)
- Marko Dinčić
- Institute of Pathological Physiology, Faculty of Medicine, University of Belgrade, Dr Subotica 9, Belgrade11000, Serbia
| | - Jasna Todorović
- Institute of Pathological Physiology, Faculty of Medicine, University of Belgrade, Dr Subotica 9, Belgrade11000, Serbia
| | - Jelena Nešović Ostojić
- Institute of Pathological Physiology, Faculty of Medicine, University of Belgrade, Dr Subotica 9, Belgrade11000, Serbia
| | - Sanjin Kovačević
- Institute of Pathological Physiology, Faculty of Medicine, University of Belgrade, Dr Subotica 9, Belgrade11000, Serbia
| | - Duško Dunđerović
- Institute of Pathology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Srđan Lopičić
- Institute of Pathological Physiology, Faculty of Medicine, University of Belgrade, Dr Subotica 9, Belgrade11000, Serbia
| | - Svetolik Spasić
- Institute of Pathological Physiology, Faculty of Medicine, University of Belgrade, Dr Subotica 9, Belgrade11000, Serbia
| | | | - Dejana Stanisavljević
- Institute of Medical Statistics and Informatics, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Andjelija Ž Ilić
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080Zemun-Belgrade, Serbia
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7
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Song W, Matlock A, Fu S, Qin X, Feng H, Gabel CV, Tian L, YI J. LED array reflectance microscopy for scattering-based multi-contrast imaging. Opt Lett 2020; 45:1647-1650. [PMID: 32235964 PMCID: PMC7278208 DOI: 10.1364/ol.387434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 02/01/2020] [Indexed: 05/24/2023]
Abstract
LED array microscopy is an emerging platform for computational imaging with significant utility for biological imaging. Existing LED array systems often exploit transmission imaging geometries of standard brightfield microscopes that leave the rich backscattered field undetected. This backscattered signal contains high-resolution sample information with superb sensitivity to subtle structural features that make it ideal for biological sensing and detection. Here, we develop an LED array reflectance microscope capturing the sample's backscattered signal. In particular, we demonstrate multimodal brightfield, darkfield, and differential phase contrast imaging on fixed and living biological specimens including Caenorhabditis elegans (C. elegans), zebrafish embryos, and live cell cultures. Video-rate multimodal imaging at 20 Hz records real time features of freely moving C. elegans and the fast beating heart of zebrafish embryos. Our new reflectance mode is a valuable addition to the LED array microscopic toolbox.
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Affiliation(s)
- Weiye Song
- Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, Massachusetts 02118, USA
| | - Alex Matlock
- Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215, USA
| | - Sipei Fu
- Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, Massachusetts 02118, USA
| | - Xiaodan Qin
- Departments of Pharmacology and Medicine, Section of Hematology and Medical Oncology, Cancer Research Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Hui Feng
- Departments of Pharmacology and Medicine, Section of Hematology and Medical Oncology, Cancer Research Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Christopher V. Gabel
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Lei Tian
- Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215, USA
| | - Ji YI
- Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, Massachusetts 02118, USA
- Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215, USA
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, USA
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8
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Matlock A, Sentenac A, Chaumet PC, Yi J, Tian L. Inverse scattering for reflection intensity phase microscopy. Biomed Opt Express 2020; 11:911-926. [PMID: 32206398 PMCID: PMC7041473 DOI: 10.1364/boe.380845] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/07/2020] [Accepted: 01/07/2020] [Indexed: 05/05/2023]
Abstract
Reflection phase imaging provides label-free, high-resolution characterization of biological samples, typically using interferometric-based techniques. Here, we investigate reflection phase microscopy from intensity-only measurements under diverse illumination. We evaluate the forward and inverse scattering model based on the first Born approximation for imaging scattering objects above a glass slide. Under this design, the measured field combines linear forward-scattering and height-dependent nonlinear back-scattering from the object that complicates object phase recovery. Using only the forward-scattering, we derive a linear inverse scattering model and evaluate this model's validity range in simulation and experiment using a standard reflection microscope modified with a programmable light source. Our method provides enhanced contrast of thin, weakly scattering samples that complement transmission techniques. This model provides a promising development for creating simplified intensity-based reflection quantitative phase imaging systems easily adoptable for biological research.
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Affiliation(s)
- Alex Matlock
- Department of Electrical and Computer Engineering, Boston University, Boston, MA 02215, USA
| | - Anne Sentenac
- Institut Fresnel, Aix Marseille Univ., CNRS, Centrale Marseille, Marseille, France
| | - Patrick C. Chaumet
- Institut Fresnel, Aix Marseille Univ., CNRS, Centrale Marseille, Marseille, France
| | - Ji Yi
- Department of Medicine, Boston University School of Medicine, Boston, MA 02215, USA
| | - Lei Tian
- Department of Electrical and Computer Engineering, Boston University, Boston, MA 02215, USA
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9
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Spicer GLC, Eid A, Wangpraseurt D, Swain TD, Winkelmann JA, Yi J, Kühl M, Marcelino LA, Backman V. Measuring light scattering and absorption in corals with Inverse Spectroscopic Optical Coherence Tomography (ISOCT): a new tool for non-invasive monitoring. Sci Rep 2019; 9:14148. [PMID: 31578438 DOI: 10.1038/s41598-019-50658-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 09/17/2019] [Indexed: 12/12/2022] Open
Abstract
The success of reef-building corals for >200 million years has been dependent on the mutualistic interaction between the coral host and its photosynthetic endosymbiont dinoflagellates (family Symbiodiniaceae) that supply the coral host with nutrients and energy for growth and calcification. While multiple light scattering in coral tissue and skeleton significantly enhance the light microenvironment for Symbiodiniaceae, the mechanisms of light propagation in tissue and skeleton remain largely unknown due to a lack of technologies to measure the intrinsic optical properties of both compartments in live corals. Here we introduce ISOCT (inverse spectroscopic optical coherence tomography), a non-invasive approach to measure optical properties and three-dimensional morphology of living corals at micron- and nano-length scales, respectively, which are involved in the control of light propagation. ISOCT enables measurements of optical properties in the visible range and thus allows for characterization of the density of light harvesting pigments in coral. We used ISOCT to characterize the optical scattering coefficient (μs) of the coral skeleton and chlorophyll a concentration of live coral tissue. ISOCT further characterized the overall micro- and nano-morphology of live tissue by measuring differences in the sub-micron spatial mass density distribution (D) that vary throughout the tissue and skeleton and give rise to light scattering, and this enabled estimates of the spatial directionality of light scattering, i.e., the anisotropy coefficient, g. Thus, ISOCT enables imaging of coral nanoscale structures and allows for quantifying light scattering and pigment absorption in live corals. ISOCT could thus be developed into an important tool for rapid, non-invasive monitoring of coral health, growth and photophysiology with unprecedented spatial resolution.
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10
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Iashina EG, Filatov MV, Pantina RA, Varfolomeeva EY, Bouwman WG, Duif CP, Honecker D, Pipich V, Grigoriev SV. Small-angle neutron scattering (SANS) and spin-echo SANS measurements reveal the logarithmic fractal structure of the large-scale chromatin organization in HeLa nuclei. J Appl Crystallogr 2019. [DOI: 10.1107/s160057671900921x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
This paper reports on the two-scale fractal structure of chromatin organization in the nucleus of the HeLa cell. Two neutron scattering methods, small-angle neutron scattering (SANS) and spin-echo SANS, are used to unambiguously identify the large-scale structure as being a logarithmic fractal with the correlation function γ(r) ∼ ln(r/ξ). The smaller-scale structural level is shown to be a volume fractal with dimension D
F = 2.41. By definition, the volume fractal is self-similar at different scales, while the logarithmic fractal is hierarchically changed upon scaling. As a result, the logarithmic fractal is more compact than the volume fractal but still has a rather high surface area, which provides accessibility at all length scales. Apparently such bi-fractal chromatin organization is the result of an evolutionary process of optimizing the compactness and accessibility of gene packing. As they are in a water solution, the HeLa nuclei tend to agglomerate over time. The large-scale logarithmic fractal structure of chromatin provides the HeLa nucleus with the possibility of penetrating deeply into the adjacent nucleus during the agglomeration process. The interpenetration phenomenon of the HeLa nuclei shows that the chromatin-free space of one nucleus is not negligible but is as large as the volume occupied by chromatin itself. It is speculated that it is the logarithmic fractal architecture of chromatin that provides a comfortable compartment for this most important function of the cell.
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11
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Lee HJ, Zhang L, Zhang S, Yi J. Detection of Malignancy in Ocular Surface Lesions by Inverse Spectroscopic Optical Coherence Tomography and Two-Photon Autofluorescence. Transl Vis Sci Technol 2019; 8:16. [PMID: 31114716 PMCID: PMC6506202 DOI: 10.1167/tvst.8.3.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 02/11/2019] [Indexed: 11/24/2022] Open
Abstract
Purpose Advanced imaging is increasingly important in the diagnosis of ocular surface malignancy. Inverse spectroscopic optical coherence tomography (ISOCT) and two-photon autofluorescence microscopy (2P-AF) are emerging techniques capable of quantifying ultrastructural and metabolic changes, respectively. We aimed to detect malignancy in ocular surface lesions using ISOCT and 2P-AF. Methods Portions of excised specimens from patients undergoing conjunctival biopsy at Boston Medical Center were imaged by ISOCT and/or 2P-AF, and submitted for histologic diagnosis. Lesions were categorized as malignant, premalignant (with dysplasia) or benign. ISOCT and 2P-AF findings were compared between categories. Results Fourteen specimens from 13 patients were collected. The IS-OCT marker D was 2.2-fold higher in combined malignant and premalignant (4.27 ± 0.28, n = 3) versus benign (1.92 ± 0.26, n = 11) lesions (P = 9 × 10−4). ISOCT markers μs and μb were not significantly different. By 2P-AF, the redox ratio was 0.24-fold lower in premalignant (0.11 ± 0.004, n = 2) versus benign (0.45 ± 0.04, n = 9) lesions (P = 1.08 × 10−5). Conclusions Conjunctival lesions with higher malignant potential had higher D and lower redox ratios. Higher D can correlate with ultrastructural changes associated with malignancy, similar to what has been seen in cancers of the gut mucosa. Lower redox ratios can suggest the presence of the Warburg effect, which is associated with tumorigenesis. Translational Relevance IS-OCT and 2P-AF can potentially be applied to the detection of malignancy or malignant potential in ocular surface lesions. ISOCT allows for the detection of nanoscale ultrastructural changes that are not resolvable by conventional OCT.
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Affiliation(s)
- Hyunjoo Jean Lee
- Department of Ophthalmology, Boston Medical Center, Boston University School of Medicine, Boston, MA, USA
| | - Lei Zhang
- Department of Medicine, Gastroenterology Section, Boston Medical Center, Boston University School of Medicine, Boston, MA, USA
| | - Sui Zhang
- Dana Faber Cancer Institute, Boston, MA, USA
| | - Ji Yi
- Department of Medicine, Gastroenterology Section, Boston Medical Center, Boston University School of Medicine, Boston, MA, USA
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Metze K, Adam R, Florindo JB. The fractal dimension of chromatin - a potential molecular marker for carcinogenesis, tumor progression and prognosis. Expert Rev Mol Diagn 2019; 19:299-312. [DOI: 10.1080/14737159.2019.1597707] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Konradin Metze
- Department of Pathology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, Brazil
| | - Randall Adam
- Department of Pathology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, Brazil
| | - João Batista Florindo
- Department of Applied Mathematics, Institute of Mathematics, Statistics and Scientific Computing, State University of Campinas, Campinas, Brazil
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Yi J, Puyang Z, Feng L, Duan L, Liang P, Backman V, Liu X, Zhang HF. Optical Detection of Early Damage in Retinal Ganglion Cells in a Mouse Model of Partial Optic Nerve Crush Injury. Invest Ophthalmol Vis Sci 2017; 57:5665-5671. [PMID: 27784071 PMCID: PMC5089219 DOI: 10.1167/iovs.16-19955] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Elastic light backscattering spectroscopy (ELBS) has exquisite sensitivity to the ultrastructural properties of tissue and thus has been applied to detect various diseases associated with ultrastructural alterations in their early stages. This study aims to test whether ELBS can detect early damage in retinal ganglion cells (RGCs). Methods We used a mouse model of partial optic nerve crush (pONC) to induce rapid RGC death. We confirmed RGC loss by axon counting and characterized the changes in retinal morphology by optical coherence tomography (OCT) and in retinal function by full-field electroretinogram (ERG), respectively. To quantify the ultrastructural properties, elastic backscattering spectroscopic analysis was implemented in the wavelength-dependent images recorded by reflectance confocal microscopy. Results At 3 days post-pONC injury, no significant change was found in the thickness of the RGC layer or in the mean amplitude of the oscillatory potentials measured by OCT and ERG, respectively; however, we did observe a significantly decreased number of axons compared with the controls. At 3 days post-pONC, we used ELBS to calculate the ultrastructural marker (D), the shape factor quantifying the shape of the local mass density correlation functions. It was significantly reduced in the crushed eyes compared with the controls, indicating the ultrastructural fragmentation in the crushed eyes. Conclusions Elastic light backscattering spectroscopy detected ultrastructural neuronal damage in RGCs following the pONC injury when OCT and ERG tests appeared normal. Our study suggests a potential clinical method for detecting early neuronal damage prior to anatomical alterations in the nerve fiber and ganglion cell layers.
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Affiliation(s)
- Ji Yi
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States
| | - Zhen Puyang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China 3Department of Ophthalmology, Northwestern University, Chicago, Illinois, United States
| | - Liang Feng
- Department of Ophthalmology, Northwestern University, Chicago, Illinois, United States
| | - Lian Duan
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States
| | - Peiji Liang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States
| | - Xiaorong Liu
- Department of Ophthalmology, Northwestern University, Chicago, Illinois, United States 4Department of Neurobiology, Northwestern University, Evanston, Illinois, United States
| | - Hao F Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, United States 3Department of Ophthalmology, Northwestern University, Chicago, Illinois, United States
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Higgins GA, Allyn-Feuer A, Georgoff P, Nikolian V, Alam HB, Athey BD. Mining the topography and dynamics of the 4D Nucleome to identify novel CNS drug pathways. Methods 2017; 123:102-118. [PMID: 28385536 DOI: 10.1016/j.ymeth.2017.03.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 03/10/2017] [Indexed: 12/16/2022] Open
Abstract
The pharmacoepigenome can be defined as the active, noncoding province of the genome including canonical spatial and temporal regulatory mechanisms of gene regulation that respond to xenobiotic stimuli. Many psychotropic drugs that have been in clinical use for decades have ill-defined mechanisms of action that are beginning to be resolved as we understand the transcriptional hierarchy and dynamics of the nucleus. In this review, we describe spatial, temporal and biomechanical mechanisms mediated by psychotropic medications. Focus is placed on a bioinformatics pipeline that can be used both for detection of pharmacoepigenomic variants that discretize drug response and adverse events to improve pharmacogenomic testing, and for the discovery of novel CNS therapeutics. This approach integrates the functional topology and dynamics of the transcriptional hierarchy of the pharmacoepigenome, gene variant-driven identification of pharmacogenomic regulatory domains, and mesoscale mapping for the discovery of novel CNS pharmacodynamic pathways in human brain. Examples of the application of this pipeline are provided, including the discovery of valproic acid (VPA) mediated transcriptional reprogramming of neuronal cell fate following injury, and mapping of a CNS pathway glutamatergic pathway for the mood stabilizer lithium. These examples in regulatory pharmacoepigenomics illustrate how ongoing research using the 4D nucleome provides a foundation to further insight into previously unrecognized psychotropic drug pharmacodynamic pathways in the human CNS.
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Affiliation(s)
- Gerald A Higgins
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, USA
| | - Ari Allyn-Feuer
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, USA
| | - Patrick Georgoff
- Department of Surgery, University of Michigan Medical School, USA
| | - Vahagn Nikolian
- Department of Surgery, University of Michigan Medical School, USA
| | - Hasan B Alam
- Department of Surgery, University of Michigan Medical School, USA
| | - Brian D Athey
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, USA; Michigan Institute for Data Science (MIDAS), USA.
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Abstract
Most histones are assembled into nucleosomes behind the replication fork to package newly synthesized DNA. By contrast, histone variants, which are encoded by separate genes, are typically incorporated throughout the cell cycle. Histone variants can profoundly change chromatin properties, which in turn affect DNA replication and repair, transcription, and chromosome packaging and segregation. Recent advances in the study of histone replacement have elucidated the dynamic processes by which particular histone variants become substrates of histone chaperones, ATP-dependent chromatin remodellers and histone-modifying enzymes. Here, we review histone variant dynamics and the effects of replacing DNA synthesis-coupled histones with their replication-independent variants on the chromatin landscape.
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Affiliation(s)
- Paul B Talbert
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, Washington 98109-1024, USA
| | - Steven Henikoff
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, Washington 98109-1024, USA
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Shinkai S, Nozaki T, Maeshima K, Togashi Y. Dynamic Nucleosome Movement Provides Structural Information of Topological Chromatin Domains in Living Human Cells. PLoS Comput Biol 2016; 12:e1005136. [PMID: 27764097 DOI: 10.1371/journal.pcbi.1005136] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/10/2016] [Indexed: 01/15/2023] Open
Abstract
The mammalian genome is organized into submegabase-sized chromatin domains (CDs) including topologically associating domains, which have been identified using chromosome conformation capture-based methods. Single-nucleosome imaging in living mammalian cells has revealed subdiffusively dynamic nucleosome movement. It is unclear how single nucleosomes within CDs fluctuate and how the CD structure reflects the nucleosome movement. Here, we present a polymer model wherein CDs are characterized by fractal dimensions and the nucleosome fibers fluctuate in a viscoelastic medium with memory. We analytically show that the mean-squared displacement (MSD) of nucleosome fluctuations within CDs is subdiffusive. The diffusion coefficient and the subdiffusive exponent depend on the structural information of CDs. This analytical result enabled us to extract information from the single-nucleosome imaging data for HeLa cells. Our observation that the MSD is lower at the nuclear periphery region than the interior region indicates that CDs in the heterochromatin-rich nuclear periphery region are more compact than those in the euchromatin-rich interior region with respect to the fractal dimensions as well as the size. Finally, we evaluated that the average size of CDs is in the range of 100–500 nm and that the relaxation time of nucleosome movement within CDs is a few seconds. Our results provide physical and dynamic insights into the genome architecture in living cells. The mammalian genome is partitioned into topological chromatin domains (CDs) in the living cell nuclei. Gene expression is highly regulated within CDs according to their structure, whereas chromatin itself is highly dynamic. This raises the following question: how is the CD structure in such dynamic chromatin? We developed a conceptual framework that unifies chromatin dynamics and structure. Using a polymer model with a fractal domain structure in a viscoelastic medium, we analytically show that nucleosome movement is subdiffusive and depends on CD structure. Hence, structural information can be extracted based on nucleosome movement in living cells with single-particle tracking experiments. This framework provides physical insights into the relationship between dynamic genome organization and gene expression.
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Spicer GLC, Azarin SM, Yi J, Young ST, Ellis R, Bauer GM, Shea LD, Backman V. Detection of extracellular matrix modification in cancer models with inverse spectroscopic optical coherence tomography. Phys Med Biol 2016; 61:6892-6904. [PMID: 27618507 DOI: 10.1088/0031-9155/61/19/6892] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In cancer biology, there has been a recent effort to understand tumor formation in the context of the tissue microenvironment. In particular, recent progress has explored the mechanisms behind how changes in the cell-extracellular matrix ensemble influence progression of the disease. The extensive use of in vitro tissue culture models in simulant matrix has proven effective at studying such interactions, but modalities for non-invasively quantifying aspects of these systems are scant. We present the novel application of an imaging technique, Inverse Spectroscopic Optical Coherence Tomography, for the non-destructive measurement of in vitro biological samples during matrix remodeling. Our findings indicate that the nanoscale-sensitive mass density correlation shape factor D of cancer cells increases in response to a more crosslinked matrix. We present a facile technique for the non-invasive, quantitative study of the micro- and nano-scale structure of the extracellular matrix and its host cells.
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Affiliation(s)
- Graham L C Spicer
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA
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