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Onuchin AA, Chernizova AV, Lebedev MA, Polovnikov KE. Communities in C. elegans connectome through the prism of non-backtracking walks. Sci Rep 2023; 13:22923. [PMID: 38129512 PMCID: PMC10739864 DOI: 10.1038/s41598-023-49503-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 12/08/2023] [Indexed: 12/23/2023] Open
Abstract
The fundamental relationship between the mesoscopic structure of neuronal circuits and organismic functions they subserve is one of the major challenges in contemporary neuroscience. Formation of structurally connected modules of neurons enacts the conversion from single-cell firing to large-scale behaviour of an organism, highlighting the importance of their accurate profiling in the data. While connectomes are typically characterized by significant sparsity of neuronal connections, recent advances in network theory and machine learning have revealed fundamental limitations of traditionally used community detection approaches in cases where the network is sparse. Here we studied the optimal community structure in the structural connectome of Caenorhabditis elegans, for which we exploited a non-conventional approach that is based on non-backtracking random walks, virtually eliminating the sparsity issue. In full agreement with the previous asymptotic results, we demonstrated that non-backtracking walks resolve the ground truth annotation into clusters on stochastic block models (SBM) with the size and density of the connectome better than the spectral methods related to simple random walks. Based on the cluster detectability threshold, we determined that the optimal number of modules in a recently mapped connectome of C. elegans is 10, which precisely corresponds to the number of isolated eigenvalues in the spectrum of the non-backtracking flow matrix. The discovered communities have a clear interpretation in terms of their functional role, which allows one to discern three structural compartments in the worm: the Worm Brain (WB), the Worm Movement Controller (WMC), and the Worm Information Flow Connector (WIFC). Broadly, our work provides a robust network-based framework to reveal mesoscopic structures in sparse connectomic datasets, paving way to further investigation of connectome mechanisms for different functions.
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Affiliation(s)
- Arsenii A Onuchin
- Skolkovo Institute of Science and Technology, Moscow, Russia, 121205
- Laboratory of Complex Networks, Center for Neurophysics and Neuromorphic Technologies, Moscow, Russia
| | - Alina V Chernizova
- Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences, Moscow, Russia, 117485
| | - Mikhail A Lebedev
- Faculty of Mechanics and Mathematics, Lomonosov Moscow State University, Moscow, Russia, 119991
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russia, 194223
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龚 海, 麻 付, 张 晓. [Advances in methods and applications of single-cell Hi-C data analysis]. SHENG WU YI XUE GONG CHENG XUE ZA ZHI = JOURNAL OF BIOMEDICAL ENGINEERING = SHENGWU YIXUE GONGCHENGXUE ZAZHI 2023; 40:1033-1039. [PMID: 37879935 PMCID: PMC10600426 DOI: 10.7507/1001-5515.202303046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 08/29/2023] [Indexed: 10/27/2023]
Abstract
Chromatin three-dimensional genome structure plays a key role in cell function and gene regulation. Single-cell Hi-C techniques can capture genomic structure information at the cellular level, which provides an opportunity to study changes in genomic structure between different cell types. Recently, some excellent computational methods have been developed for single-cell Hi-C data analysis. In this paper, the available methods for single-cell Hi-C data analysis were first reviewed, including preprocessing of single-cell Hi-C data, multi-scale structure recognition based on single-cell Hi-C data, bulk-like Hi-C contact matrix generation based on single-cell Hi-C data sets, pseudo-time series analysis, and cell classification. Then the application of single-cell Hi-C data in cell differentiation and structural variation was described. Finally, the future development direction of single-cell Hi-C data analysis was also prospected.
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Affiliation(s)
- 海燕 龚
- 北京科技大学 新材料技术研究院 (北京 100083)Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, P. R. China
- 北京科技大学 计算机与通信工程学院(北京 100083)School of Computer and Communication Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
| | - 付强 麻
- 北京科技大学 新材料技术研究院 (北京 100083)Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, P. R. China
| | - 晓彤 张
- 北京科技大学 新材料技术研究院 (北京 100083)Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, P. R. China
- 北京科技大学 计算机与通信工程学院(北京 100083)School of Computer and Communication Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China
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Chi Y, Shi J, Xing D, Tan L. Every gene everywhere all at once: High-precision measurement of 3D chromosome architecture with single-cell Hi-C. Front Mol Biosci 2022; 9:959688. [PMID: 36275628 PMCID: PMC9583135 DOI: 10.3389/fmolb.2022.959688] [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: 06/06/2022] [Accepted: 09/06/2022] [Indexed: 11/13/2022] Open
Abstract
The three-dimensional (3D) structure of chromosomes influences essential biological processes such as gene expression, genome replication, and DNA damage repair and has been implicated in many developmental and degenerative diseases. In the past two centuries, two complementary genres of technology-microscopy, such as fluorescence in situ hybridization (FISH), and biochemistry, such as chromosome conformation capture (3C or Hi-C)-have revealed general principles of chromosome folding in the cell nucleus. However, the extraordinary complexity and cell-to-cell variability of the chromosome structure necessitate new tools with genome-wide coverage and single-cell precision. In the past decade, single-cell Hi-C emerges as a new approach that builds upon yet conceptually differs from bulk Hi-C assays. Instead of measuring population-averaged statistical properties of chromosome folding, single-cell Hi-C works as a proximity-based "biochemical microscope" that measures actual 3D structures of individual genomes, revealing features hidden in bulk Hi-C such as radial organization, multi-way interactions, and chromosome intermingling. Single-cell Hi-C has been used to study highly dynamic processes such as the cell cycle, cell-type-specific chromosome architecture ("structure types"), and structure-expression interplay, deepening our understanding of DNA organization and function.
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Affiliation(s)
- Yi Chi
- Biomedical Pioneering Innovation Center, Peking University, Beijing, China,Innovation Center for Genomics, Peking University, Beijing, China
| | - Jenny Shi
- Department of Neurobiology, Stanford University, Stanford, CA, United States,Department of Chemistry, Stanford University, Stanford, CA, United States,Department of Bioengineering, Stanford University, Stanford, CA, United States
| | - Dong Xing
- Biomedical Pioneering Innovation Center, Peking University, Beijing, China,Innovation Center for Genomics, Peking University, Beijing, China,*Correspondence: Longzhi Tan, ; Dong Xing,
| | - Longzhi Tan
- Department of Neurobiology, Stanford University, Stanford, CA, United States,Department of Bioengineering, Stanford University, Stanford, CA, United States,*Correspondence: Longzhi Tan, ; Dong Xing,
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Galitsyna AA, Gelfand MS. Single-cell Hi-C data analysis: safety in numbers. Brief Bioinform 2021; 22:bbab316. [PMID: 34406348 PMCID: PMC8575028 DOI: 10.1093/bib/bbab316] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/09/2021] [Accepted: 07/21/2021] [Indexed: 02/06/2023] Open
Abstract
Over the past decade, genome-wide assays for chromatin interactions in single cells have enabled the study of individual nuclei at unprecedented resolution and throughput. Current chromosome conformation capture techniques survey contacts for up to tens of thousands of individual cells, improving our understanding of genome function in 3D. However, these methods recover a small fraction of all contacts in single cells, requiring specialised processing of sparse interactome data. In this review, we highlight recent advances in methods for the interpretation of single-cell genomic contacts. After discussing the strengths and limitations of these methods, we outline frontiers for future development in this rapidly moving field.
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Affiliation(s)
- Aleksandra A Galitsyna
- Skolkovo Institute of Science and Technology, Skolkovo, Russia
- Institute for Information Transmission Problems, RAS, Moscow, Russia
- Institute of Gene Biology, RAS, Moscow, Russia
| | - Mikhail S Gelfand
- Skolkovo Institute of Science and Technology, Skolkovo, Russia
- Institute for Information Transmission Problems, RAS, Moscow, Russia
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Ulianov SV, Razin SV. The two waves in single-cell 3D genomics. Semin Cell Dev Biol 2021; 121:143-152. [PMID: 34030950 DOI: 10.1016/j.semcdb.2021.05.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 05/11/2021] [Accepted: 05/16/2021] [Indexed: 02/07/2023]
Abstract
For decades, biochemical methods for the analysis of genome structure and function provided cell-population-averaged data that allowed general principles and tendencies to be disclosed. Microscopy-based studies, which immanently involve single-cell analysis, did not provide sufficient spatial resolution to investigate the particularly small details of 3D genome folding. Nevertheless, these studies demonstrated that mutual positions of chromosome territories within cell nuclei and individual genomic loci within chromosomal territories can vary significantly in individual cells. The development of new technologies in biochemistry and the advent of super-resolution microscopy in the last decade have made possible the full-scale study of 3D genome organization in individual cells. Maps of the 3D genome build based on C-data and super-resolution microscopy are highly consistent and, therefore, biologically relevant. The internal structures of individual chromosomes, loci, and topologically associating domains (TADs) are resolved as well as cell-cycle dynamics. 3D modeling allows one to investigate the physical mechanisms underlying genome folding. Finally, joint profiling of genome topology and epigenetic features will allow 3D genomics to handle complex cell-to-cell heterogeneity. In this review, we summarize the present state of studies into 3D genome organization in individual cells, analyze the technical problems of single-cell studies, and outline perspectives of 3D genomics.
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Affiliation(s)
- Sergey V Ulianov
- Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; Faculty of Biology, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia.
| | - Sergey V Razin
- Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; Faculty of Biology, M.V. Lomonosov Moscow State University, 119234 Moscow, Russia.
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Order and stochasticity in the folding of individual Drosophila genomes. Nat Commun 2021; 12:41. [PMID: 33397980 PMCID: PMC7782554 DOI: 10.1038/s41467-020-20292-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 11/23/2020] [Indexed: 02/06/2023] Open
Abstract
Mammalian and Drosophila genomes are partitioned into topologically associating domains (TADs). Although this partitioning has been reported to be functionally relevant, it is unclear whether TADs represent true physical units located at the same genomic positions in each cell nucleus or emerge as an average of numerous alternative chromatin folding patterns in a cell population. Here, we use a single-nucleus Hi-C technique to construct high-resolution Hi-C maps in individual Drosophila genomes. These maps demonstrate chromatin compartmentalization at the megabase scale and partitioning of the genome into non-hierarchical TADs at the scale of 100 kb, which closely resembles the TAD profile in the bulk in situ Hi-C data. Over 40% of TAD boundaries are conserved between individual nuclei and possess a high level of active epigenetic marks. Polymer simulations demonstrate that chromatin folding is best described by the random walk model within TADs and is most suitably approximated by a crumpled globule build of Gaussian blobs at longer distances. We observe prominent cell-to-cell variability in the long-range contacts between either active genome loci or between Polycomb-bound regions, suggesting an important contribution of stochastic processes to the formation of the Drosophila 3D genome. Genomes are partitioned into topologically associating domains (TADs). Here the authors present single-nucleus Hi-C maps in Drosophila at 10 kb resolution, demonstrating the presence of chromatin compartments in individual nuclei, and partitioning of the genome into non-hierarchical TADs at the scale of 100 kb, which resembles population TAD profiles.
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