{"id":{"repo_id":"utswmed","oai_identifier":"oai:utswmed-ir.tdl.org:2152.5/10718"},"canonical_url":"https://search.dev.ndltd.org/etd/utswmed/oai:utswmed-ir.tdl.org:2152.5/10718","repository":{"repo_id":"utswmed","name":"University of Texas Southwestern Medical Center","base_url":"https://utswmed-ir.tdl.org/server/oai/request"},"display":{"title":"Understanding the Role of Loner in Myoblast Fusion","abstract":"The general metadata -- e.g., title, author, abstract, subject headings, etc. -- is publicly available, but access to the submitted files is restricted to UT Southwestern campus access and/or authorized UT Southwestern users.","abstract_html":"The general metadata -- e.g., title, author, abstract, subject headings, etc. -- is publicly available, but access to the submitted files is restricted to UT Southwestern campus access and/or authorized UT Southwestern users.","abstract_has_math":false,"creators":["Gokhale, Amrita Shrikant"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Henne, W. Mike","Buszczak, Michael","Jiang, Jin","Chen, Elizabeth"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-09-08T21:53:34Z","date_published":"2025-09-08T21:53:34Z","updated_at":"2026-07-24T05:52:26Z","subjects":["Cytoskeletal Proteins","Drosophila melanogaster","Drosophila Proteins","Membrane Fusion","Myoblasts","Actins"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["1535537181"],"render_values":[{"text":"1535537181","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/2152.5/10718","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Henne, W. 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During myogenesis, mononucleated myoblasts fuse together to form multinucleated muscle fibers. The fruit fly Drosophila offers a genetically tractable model organism to myoblast fusion. The Drosophila embryonic musculature results from the fusion between two types of cells - muscle founder cells and fusion competent myoblasts (FCMs). Previous studies have revealed an asymmetric "fusogenic synapse", wherein the FCM generates an F-actin-enriched podosome-like structure (PLS) to invade the founder cell to promote cell membrane fusion. Previous work from our lab identified a Sec7 and PH domain-containing guanine nucleotide exchange factor (GEF), Loner, that activates the Arf GTPases in myoblast fusion. However, its precise mechanism of action during myoblast fusion remains poorly understood. Genetic rescue experiments showed that while Loner in required in both founder cells and FCMs, it plays a major role in the FCMs. Consistent with this, Loner is enriched at the fusogenic synapse in the FCMs but not the founder cells. This is likely due to the interaction between Loner and the FCM-specific cell adhesion molecule, Sns, the latter of which recruits Loner into phase-separated condensates. We show that the cytoplasmic domain of Sns involved in recruiting Loner is required for Sns function in myoblast fusion. Interestingly, the N-terminal domain of Loner is involved in phase separation with Sns, but it is dispensable for Loner's function when the C-terminal half of Loner containing Sec7 and PH domains is overexpressed, suggesting that the function of phase separation is to increase the local concentration of Loner at the fusogenic synapse. We found that the F-actin structures at the fusogenic synapses in loner mutant embryos appear diffused and unstable, thus failing to induce cell fusion. Co-immunoprecipitation assays revealed biochemical interactions between Loner (and an Arf GTPase) and the actin nucleation-promoting factors (NPFs) for branched actin polymerization, WASP and Scar. We propose that Loner is enriched at the fusogenic synapse to recruit NPFs and activate Arf, which in turn enhances the activities of the NPFs to promote myoblast fusion."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Understanding the Role of Loner in Myoblast Fusion"]}]}],"canonical_facts":{"dc:contributor":["Henne, W. Mike","Buszczak, Michael","Jiang, Jin","Chen, Elizabeth"],"dc:creator":["Gokhale, Amrita Shrikant"],"dc:date":["2025-09-08T21:53:34Z","2023-08","August 2023"],"dc:description":["The general metadata -- e.g., title, author, abstract, subject headings, etc. -- is publicly available, but access to the submitted files is restricted to UT Southwestern campus access and/or authorized UT Southwestern users.","Cell-cell fusion is a fundamental process in the development and physiology of multicellular organisms. During myogenesis, mononucleated myoblasts fuse together to form multinucleated muscle fibers. The fruit fly Drosophila offers a genetically tractable model organism to myoblast fusion. The Drosophila embryonic musculature results from the fusion between two types of cells - muscle founder cells and fusion competent myoblasts (FCMs). Previous studies have revealed an asymmetric "fusogenic synapse", wherein the FCM generates an F-actin-enriched podosome-like structure (PLS) to invade the founder cell to promote cell membrane fusion. Previous work from our lab identified a Sec7 and PH domain-containing guanine nucleotide exchange factor (GEF), Loner, that activates the Arf GTPases in myoblast fusion. However, its precise mechanism of action during myoblast fusion remains poorly understood. Genetic rescue experiments showed that while Loner in required in both founder cells and FCMs, it plays a major role in the FCMs. Consistent with this, Loner is enriched at the fusogenic synapse in the FCMs but not the founder cells. This is likely due to the interaction between Loner and the FCM-specific cell adhesion molecule, Sns, the latter of which recruits Loner into phase-separated condensates. We show that the cytoplasmic domain of Sns involved in recruiting Loner is required for Sns function in myoblast fusion. Interestingly, the N-terminal domain of Loner is involved in phase separation with Sns, but it is dispensable for Loner's function when the C-terminal half of Loner containing Sec7 and PH domains is overexpressed, suggesting that the function of phase separation is to increase the local concentration of Loner at the fusogenic synapse. We found that the F-actin structures at the fusogenic synapses in loner mutant embryos appear diffused and unstable, thus failing to induce cell fusion. Co-immunoprecipitation assays revealed biochemical interactions between Loner (and an Arf GTPase) and the actin nucleation-promoting factors (NPFs) for branched actin polymerization, WASP and Scar. We propose that Loner is enriched at the fusogenic synapse to recruit NPFs and activate Arf, which in turn enhances the activities of the NPFs to promote myoblast fusion."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2152.5/10718","1535537181"],"dc:language":["en"],"dc:subject":["Cytoskeletal Proteins","Drosophila melanogaster","Drosophila Proteins","Membrane Fusion","Myoblasts","Actins"],"dc:title":["Understanding the Role of Loner in Myoblast Fusion"],"dc:type":["Thesis","text"]},"updated_at":"2026-07-24T05:52:26Z"}