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From multi-omics data to global association networks: Application to disease module finding and pathway analysis
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0002-7521-8368
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis explores how bioinformatics advances the study of complex diseases by providing system-level models that capture intricate gene-protein interactions. Traditional reductionist methods focusing on isolated genes or proteins fail to explain the broader dysfunctions of complex diseases. The rise of diseases like cancer, cardiovascular and neurological disorders, and autoimmune conditions underscores the need for approaches leveraging high-throughput technologies and network-based models for comprehensive understanding.

Central to this research are functional association networks, which map direct and indirect functional relationships between genes and proteins. These networks integrate genomic, transcriptomic, proteomic, and functional data. Functional association networks are valuable resources in biological and biomedical research, enabling e.g. discovery of interaction partners, pathway enrichment analysis, and disease module identification. This thesis presents the 5th and 6th releases of FunCoup, a comprehensive resource of functional association networks, with upgrades in data integration, network framework, and user access via a redesigned website and Cytoscape app.

FunCoup 5 expanded to 22 species and generated around 70 million interaction links from 11 evidence types. Innovations included directed regulatory links, a SARS-CoV-2 virus-host network, and tissue-specific filtering for context-sensitive research.

FunCoup 6 expanded to all 640 species in InParanoiDB, with over 100 million links for the 23 primary species, including 1 million directed transcription factor-target links. A key improvement is the shift to a bin-free Bayesian training framework, using kernel density estimation of likelihoods of interaction from ten evidence types. New tools like MaxLink and TOPAS were added for disease module and drug target identification, together with built-in KEGG pathway enrichment via ANUBIX and EASE. Rebuilt in Python with a redesigned website, FunCoup 6 offers enhanced flexibility, scalability, and user access.

The FunCoup Cytoscape app uses the RESTful API to integrate FunCoup’s resources into Cytoscape, enabling network visualization and analysis across all 640 species with powerful Cytoscape tools and plugins.

This thesis highlights applications in pathway enrichment analysis (EA) and disease module detection. Network-based EA tools simplify the analysis of differentially expressed genes by linking them to known pathways, providing a systems-level understanding of molecular changes. A new benchmark compared 14 EA methods across 82 datasets from 26 diseases, showing that network-based methods like ANUBIX outperformed traditional approaches, offering more accurate insights and guidance for method selection.

TOPAS, a new approach, uncovers complex molecular interactions using functional association networks and disease-gene association databases. Complex diseases arise from genetic and environmental factors creating clusters of dysfunction within networks. These "disease modules" reveal genetic interactions in disease phenotypes and help identify novel therapeutic targets. By clustering disease-related proteins, this work advances network medicine, showcasing the power of computational techniques in understanding complex diseases.

This thesis contributes to network biology and network medicine, advancing multi-omics data integration into functional association networks, with a focus on FunCoup and network-based applications.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University , 2024. , p. 91
Keywords [en]
Systems Biology; Network Biology; Functional Association Network; Pathway Enrichment Analysis; Network Medicine; Disease Module Detection
National Category
Bioinformatics and Systems Biology
Research subject
Biochemistry towards Bioinformatics
Identifiers
URN: urn:nbn:se:su:diva-235224ISBN: 978-91-8107-022-4 (print)ISBN: 978-91-8107-023-1 (electronic)OAI: oai:DiVA.org:su-235224DiVA, id: diva2:1910329
Public defence
2024-12-20, Solna, Tomtebodavägen 23A and online via Zoom, public link is available at the department website, Solna, 14:00 (English)
Opponent
Supervisors
Available from: 2024-11-27 Created: 2024-11-04 Last updated: 2024-11-19Bibliographically approved
List of papers
1. FunCoup 5: Functional Association Networks in All Domains of Life, Supporting Directed Links and Tissue-Specificity
Open this publication in new window or tab >>FunCoup 5: Functional Association Networks in All Domains of Life, Supporting Directed Links and Tissue-Specificity
Show others...
2021 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 433, article id 166835Article in journal (Refereed) Published
Abstract [en]

FunCoup (https://funcoup.sbc.su.se) is one of the most comprehensive functional association networks of genes/proteins available. Functional associations are inferred by integrating different types of evidence using a redundancy-weighted naïve Bayesian approach, combined with orthology transfer. FunCoup's high coverage comes from using eleven different types of evidence, and extensive transfer of information between species. Since the latest update of the database, the availability of source data has improved drastically, and user expectations on a tool for functional associations have grown. To meet these requirements, we have made a new release of FunCoup with updated source data and improved functionality. FunCoup 5 now includes 22 species from all domains of life, and the source data for evidences, gold standards, and genomes have been updated to the latest available versions. In this new release, directed regulatory links inferred from transcription factor binding can be visualized in the network viewer for the human interactome. Another new feature is the possibility to filter by genes expressed in a certain tissue in the network viewer. FunCoup 5 further includes the SARS-CoV-2 proteome, allowing users to visualize and analyze interactions between SARS-CoV-2 and human proteins in order to better understand COVID-19. This new release of FunCoup constitutes a major advance for the users, with updated sources, new species and improved functionality for analysis of the networks.

Keywords
Bayesian integration; SARS-CoV-2; functional association network; gene regulatory network; protein network; tissue-specific network.
National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-195046 (URN)10.1016/j.jmb.2021.166835 (DOI)000648520800016 ()
Available from: 2021-08-02 Created: 2021-08-02 Last updated: 2024-11-04Bibliographically approved
2. FunCoup 6: advancing functional association networks across species with directed links and improved user experience
Open this publication in new window or tab >>FunCoup 6: advancing functional association networks across species with directed links and improved user experience
2024 (English)In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962Article in journal (Refereed) Accepted
Abstract [en]

FunCoup 6 (https://funcoup.org) represents a significant advancement in global functional association networks, aiming to provide researchers with a comprehensive view of the functional coupling interactome. This update introduces novel methodologies and integrated tools for improved network inference and analysis. Major new developments in FunCoup 6 include vastly expanding the coverage of gene regulatory links, a new framework for bin-free Bayesian training, and a new website. FunCoup 6 integrates a new tool for disease and drug target module identification using the TOPAS algorithm. To expand the utility of the resource for biomedical research, it incorporates pathway enrichment analysis using the ANUBIX and EASE algorithms. The unique comparative interactomics analysis in FunCoup provides insights of network conservation, now allowing users to align orthologs only or query each species network independently. Bin-free training was applied to 23 primary species, and in addition networks were generated for all remaining 618 species in InParanoiDB 9. Accompanying these advancements, FunCoup 6 features a new redesigned website, together with updated API functionalities, and represents a pivotal step forward in functional genomics research, offering unique capabilities for exploring the complex landscape of protein interactions.

Keywords
Systems Biology; Functional Association Network; Gene Regulatory Network, Bayesian integration; Comparative Interactomics
National Category
Bioinformatics and Systems Biology
Research subject
Biochemistry towards Bioinformatics
Identifiers
urn:nbn:se:su:diva-235256 (URN)10.1093/nar/gkae1021 (DOI)
Funder
Swedish Research Council, 2019-04095
Note

This article has been accepted for publication by Oxford University Press and a DOI has been pre-registered: https://doi.org/10.1093/nar/gkae1021. This persistent identifier can be shared by authors and readers, and will redirect to the published article when available

Available from: 2024-11-04 Created: 2024-11-04 Last updated: 2024-11-11
3. The FunCoup Cytoscape App: multi-species network analysis and visualization
Open this publication in new window or tab >>The FunCoup Cytoscape App: multi-species network analysis and visualization
2024 (English)In: Article in journal (Refereed) Submitted
Abstract [en]

Summary Functional association networks, such as FunCoup, are crucial for analyzing complex gene interactions. To facilitate the analysis and visualization of such genome-wide networks, there is a need for seamless integration with powerful network analysis tools like Cytoscape.

The FunCoup Cytoscape App integrates the FunCoup web service API with Cytoscape, allowing users to visualize and analyze gene interaction networks for 640 species. Users can input gene identifiers and customize search parameters, employing various network expansion algorithms like group or independent gene search, MaxLink, and TOPAS. The app maintains consistent visualizations with the FunCoup website, providing detailed node and link information, including tissue and pathway gene annotations. The integration with Cytoscape plugins, such as ClusterMaker2, enhances the analytical capabilities of FunCoup, as exemplified by the identification of the Myasthenia gravis disease module along with potential new therapeutic targets.

Availability and implementation The FunCoup Cytoscape App is developed using the Java OSGi framework, with UI components implemented in Java Swing and build support from Maven. The App is available as a JAR file at https://bitbucket.org/sonnhammergroup/funcoup_cytoscape/ repo, and can be downloaded from the Cytoscape App store https://apps.cytoscape.org/.

Keywords
Systems Biology; Functional Association Network; Bayesian integration; Cytoscape; Clustermaker
National Category
Bioinformatics and Systems Biology
Research subject
Biochemistry towards Bioinformatics
Identifiers
urn:nbn:se:su:diva-235220 (URN)
Funder
Swedish Research Council, 2019-04095
Available from: 2024-11-01 Created: 2024-11-01 Last updated: 2024-11-11
4. Benchmarking enrichment analysis methods with the disease pathway network
Open this publication in new window or tab >>Benchmarking enrichment analysis methods with the disease pathway network
2024 (English)In: Briefings in Bioinformatics, ISSN 1467-5463, E-ISSN 1477-4054, Vol. 25, no 2, article id bbae069Article in journal (Refereed) Published
Abstract [en]

Enrichment analysis (EA) is a common approach to gain functional insights from genome-scale experiments. As a consequence, a large number of EA methods have been developed, yet it is unclear from previous studies which method is the best for a given dataset. The main issues with previous benchmarks include the complexity of correctly assigning true pathways to a test dataset, and lack of generality of the evaluation metrics, for which the rank of a single target pathway is commonly used. We here provide a generalized EA benchmark and apply it to the most widely used EA methods, representing all four categories of current approaches. The benchmark employs a new set of 82 curated gene expression datasets from DNA microarray and RNA-Seq experiments for 26 diseases, of which only 13 are cancers. In order to address the shortcomings of the single target pathway approach and to enhance the sensitivity evaluation, we present the Disease Pathway Network, in which related Kyoto Encyclopedia of Genes and Genomes pathways are linked. We introduce a novel approach to evaluate pathway EA by combining sensitivity and specificity to provide a balanced evaluation of EA methods. This approach identifies Network Enrichment Analysis methods as the overall top performers compared with overlap-based methods. By using randomized gene expression datasets, we explore the null hypothesis bias of each method, revealing that most of them produce skewed P-values.

Keywords
disease pathway network, functional enrichment, gene expression data, gene set enrichment analysis, pathway enrichment analysis, systems biology
National Category
Bioinformatics and Systems Biology
Identifiers
urn:nbn:se:su:diva-235218 (URN)10.1093/bib/bbae069 (DOI)001281650100007 ()2-s2.0-85186679428 (Scopus ID)
Funder
Swedish Research Council, 2022-06725Swedish Research Council, 2018-05973Swedish Research Council, 2019-04095Stockholm University
Available from: 2024-11-01 Created: 2024-11-01 Last updated: 2024-11-11Bibliographically approved
5. TOPAS, a network-based approach to detect disease modules in a top-down fashion 
Open this publication in new window or tab >>TOPAS, a network-based approach to detect disease modules in a top-down fashion 
2022 (English)In: NAR Genomics and Bioinformatics, E-ISSN 2631-9268, Vol. 4, no 4, article id lqac093Article in journal (Refereed) Published
Abstract [en]

A vast scenario of potential disease mechanisms and remedies is yet to be discovered. The field of Network Medicine has grown thanks to the massive amount of high-throughput data and the emerging evidence that disease-related proteins form ‘disease modules’. Relying on prior disease knowledge, network-based disease module detection algorithms aim at connecting the list of known disease associated genes by exploiting interaction networks. Most existing methods extend disease modules by iteratively adding connector genes in a bottom-up fashion, while top-down approaches remain largely unexplored. We have created TOPAS, an iterative approach that aims at connecting the largest number of seed nodes in a top-down fashion through connectors that guarantee the highest flow of a Random Walk with Restart in a network of functional associations. We used a corpus of 382 manually selected functional gene sets to benchmark our algorithm against SCA, DIAMOnD, MaxLink and ROBUST across four interactomes. We demonstrate that TOPAS outperforms competing methods in terms of Seed Recovery Rate, Seed to Connector Ratio and consistency during module detection. We also show that TOPAS achieves competitive performance in terms of biological relevance of detected modules and scalability. 

National Category
Biological Sciences Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:su:diva-213374 (URN)10.1093/nargab/lqac093 (DOI)000892515400002 ()36458021 (PubMedID)
Available from: 2023-01-09 Created: 2023-01-09 Last updated: 2024-11-04Bibliographically approved

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