{"id":{"repo_id":"toronto-retro","oai_identifier":"oai:utoronto.scholaris.ca:1807/149794"},"canonical_url":"https://search.dev.ndltd.org/etd/toronto-retro/oai:utoronto.scholaris.ca:1807/149794","repository":{"repo_id":"toronto-retro","name":"University of Toronto","base_url":"https://utoronto.scholaris.ca/server/oai/request"},"display":{"title":"Investigating the Effects of C9orf72 Haploinsufficiency on TDP-43 Pathology in ALS","abstract":"In amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), transactive response DNA-binding protein 43 (TDP-43), a mainly nuclear DNA/RNA binding protein, is mislocalized to the cytoplasm of diseased neurons, where it forms abnormally phosphorylated and ubiquitinated inclusions, known as TDP-43 proteinopathy. TDP-43 proteinopathy is characteristic of patients with chromosome 9 open reading frame 72 (C9orf72) G4C2 repeat expansions, the most common genetic cause of ALS/FTD. C9orf72 is a differentially expressed in normal and neoplastic cells (DENN) domain containing protein and is reported to have roles in autophagy. The mechanisms in which TDP-43 mislocalizes and how C9orf72 mutations contribute to TDP-43 proteinopathy remain unclear. I hypothesize that loss of C9orf72 could lead to autophagic deficits promoting TDP-43 pathology. To test this, a mouse model of TDP-43 proteinopathy was generated using AAV9-mediated intracerebroventricular (i.c.v) injections of EGFP-tagged pathological isoforms of TDP-43, TDP-35 and TDP-25. TDP-35 and TDP-25 mice exhibited differential expression patterns and behavioral deficits, with TDP-35 mice displaying FTD-like phenotypes and TDP-25 mice showing ALS-like phenotypes with TDP-25 forming neuronal cytoplasmic abnormally phosphorylated and ubiquitinated aggregates, recapitulating central hallmarks of TDP-43 proteinopathy. When expressed in C9orf72 deficient mice, loss of C9orf72 exacerbated neuropathological and motor phenotypes caused by TDP-25 aggregation. Changes in common autophagic markers and accumulation of p62 puncta were found in TDP-25-expressing C9orf72 deficient mice, implicating autophagy as a major pathway for a two-hit system in which TDP-43 proteinopathy synergizes with loss of C9orf72 function in ALS. These results were replicated in a C9orf72 haploinsufficient mutant TDP-43A315T transgenic mouse model. These findings demonstrate a combined effect of EGFP-TDP-25 expression and C9orf72 deficiency that leads to neuronal loss and motor behavioral deficits, suggesting a two-hit model causing neurodegeneration in ALS.","abstract_html":"In amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), transactive response DNA-binding protein 43 (TDP-43), a mainly nuclear DNA/RNA binding protein, is mislocalized to the cytoplasm of diseased neurons, where it forms abnormally phosphorylated and ubiquitinated inclusions, known as TDP-43 proteinopathy. TDP-43 proteinopathy is characteristic of patients with chromosome 9 open reading frame 72 (C9orf72) G4C2 repeat expansions, the most common genetic cause of ALS/FTD. C9orf72 is a differentially expressed in normal and neoplastic cells (DENN) domain containing protein and is reported to have roles in autophagy. The mechanisms in which TDP-43 mislocalizes and how C9orf72 mutations contribute to TDP-43 proteinopathy remain unclear. I hypothesize that loss of C9orf72 could lead to autophagic deficits promoting TDP-43 pathology. To test this, a mouse model of TDP-43 proteinopathy was generated using AAV9-mediated intracerebroventricular (i.c.v) injections of EGFP-tagged pathological isoforms of TDP-43, TDP-35 and TDP-25. TDP-35 and TDP-25 mice exhibited differential expression patterns and behavioral deficits, with TDP-35 mice displaying FTD-like phenotypes and TDP-25 mice showing ALS-like phenotypes with TDP-25 forming neuronal cytoplasmic abnormally phosphorylated and ubiquitinated aggregates, recapitulating central hallmarks of TDP-43 proteinopathy. When expressed in C9orf72 deficient mice, loss of C9orf72 exacerbated neuropathological and motor phenotypes caused by TDP-25 aggregation. Changes in common autophagic markers and accumulation of p62 puncta were found in TDP-25-expressing C9orf72 deficient mice, implicating autophagy as a major pathway for a two-hit system in which TDP-43 proteinopathy synergizes with loss of C9orf72 function in ALS. These results were replicated in a C9orf72 haploinsufficient mutant TDP-43A315T transgenic mouse model. These findings demonstrate a combined effect of EGFP-TDP-25 expression and C9orf72 deficiency that leads to neuronal loss and motor behavioral deficits, suggesting a two-hit model causing neurodegeneration in ALS.","abstract_has_math":false,"creators":["Lin, Lilian Tsai Wei"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Laboratory Medicine and Pathobiology","school":null,"contributors":[],"advisors":["Robertson, Janice"],"committee_chairs":[],"committee_members":[],"year":2023,"date_issued":"2023-11","date_published":"2023-11","updated_at":"2026-07-27T21:28:05Z","subjects":["Amyotrophic Lateral Sclerosis","Autophagy","C9orf72","Mouse Model","Neurodegenerative Diseases","TDP-43"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1807/149794","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Robertson, Janice"]},{"key":"dc:contributor.department","label":"Department","values":["Laboratory Medicine and Pathobiology"]},{"key":"dc:creator","label":"Author","values":["Lin, Lilian Tsai Wei"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2023-11"]},{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-11-13T05:22:08Z"]},{"key":"dc:date.issued","label":"Date","values":["2023-11"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Amyotrophic Lateral Sclerosis","Autophagy","C9orf72","Mouse Model","Neurodegenerative Diseases","TDP-43"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/1807/149794"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), transactive response DNA-binding protein 43 (TDP-43), a mainly nuclear DNA/RNA binding protein, is mislocalized to the cytoplasm of diseased neurons, where it forms abnormally phosphorylated and ubiquitinated inclusions, known as TDP-43 proteinopathy. TDP-43 proteinopathy is characteristic of patients with chromosome 9 open reading frame 72 (C9orf72) G4C2 repeat expansions, the most common genetic cause of ALS/FTD. C9orf72 is a differentially expressed in normal and neoplastic cells (DENN) domain containing protein and is reported to have roles in autophagy. The mechanisms in which TDP-43 mislocalizes and how C9orf72 mutations contribute to TDP-43 proteinopathy remain unclear. I hypothesize that loss of C9orf72 could lead to autophagic deficits promoting TDP-43 pathology. To test this, a mouse model of TDP-43 proteinopathy was generated using AAV9-mediated intracerebroventricular (i.c.v) injections of EGFP-tagged pathological isoforms of TDP-43, TDP-35 and TDP-25. TDP-35 and TDP-25 mice exhibited differential expression patterns and behavioral deficits, with TDP-35 mice displaying FTD-like phenotypes and TDP-25 mice showing ALS-like phenotypes with TDP-25 forming neuronal cytoplasmic abnormally phosphorylated and ubiquitinated aggregates, recapitulating central hallmarks of TDP-43 proteinopathy. When expressed in C9orf72 deficient mice, loss of C9orf72 exacerbated neuropathological and motor phenotypes caused by TDP-25 aggregation. Changes in common autophagic markers and accumulation of p62 puncta were found in TDP-25-expressing C9orf72 deficient mice, implicating autophagy as a major pathway for a two-hit system in which TDP-43 proteinopathy synergizes with loss of C9orf72 function in ALS. These results were replicated in a C9orf72 haploinsufficient mutant TDP-43A315T transgenic mouse model. These findings demonstrate a combined effect of EGFP-TDP-25 expression and C9orf72 deficiency that leads to neuronal loss and motor behavioral deficits, suggesting a two-hit model causing neurodegeneration in ALS."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Investigating the Effects of C9orf72 Haploinsufficiency on TDP-43 Pathology in ALS"]}]}],"canonical_facts":{"dc:contributor.advisor":["Robertson, Janice"],"dc:contributor.department":["Laboratory Medicine and Pathobiology"],"dc:creator":["Lin, Lilian Tsai Wei"],"dc:date":["2023-11"],"dc:date.accessioned":["2025-11-13T05:22:08Z"],"dc:date.issued":["2023-11"],"dc:description.abstract":["In amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), transactive response DNA-binding protein 43 (TDP-43), a mainly nuclear DNA/RNA binding protein, is mislocalized to the cytoplasm of diseased neurons, where it forms abnormally phosphorylated and ubiquitinated inclusions, known as TDP-43 proteinopathy. TDP-43 proteinopathy is characteristic of patients with chromosome 9 open reading frame 72 (C9orf72) G4C2 repeat expansions, the most common genetic cause of ALS/FTD. C9orf72 is a differentially expressed in normal and neoplastic cells (DENN) domain containing protein and is reported to have roles in autophagy. The mechanisms in which TDP-43 mislocalizes and how C9orf72 mutations contribute to TDP-43 proteinopathy remain unclear. I hypothesize that loss of C9orf72 could lead to autophagic deficits promoting TDP-43 pathology. To test this, a mouse model of TDP-43 proteinopathy was generated using AAV9-mediated intracerebroventricular (i.c.v) injections of EGFP-tagged pathological isoforms of TDP-43, TDP-35 and TDP-25. TDP-35 and TDP-25 mice exhibited differential expression patterns and behavioral deficits, with TDP-35 mice displaying FTD-like phenotypes and TDP-25 mice showing ALS-like phenotypes with TDP-25 forming neuronal cytoplasmic abnormally phosphorylated and ubiquitinated aggregates, recapitulating central hallmarks of TDP-43 proteinopathy. When expressed in C9orf72 deficient mice, loss of C9orf72 exacerbated neuropathological and motor phenotypes caused by TDP-25 aggregation. Changes in common autophagic markers and accumulation of p62 puncta were found in TDP-25-expressing C9orf72 deficient mice, implicating autophagy as a major pathway for a two-hit system in which TDP-43 proteinopathy synergizes with loss of C9orf72 function in ALS. These results were replicated in a C9orf72 haploinsufficient mutant TDP-43A315T transgenic mouse model. These findings demonstrate a combined effect of EGFP-TDP-25 expression and C9orf72 deficiency that leads to neuronal loss and motor behavioral deficits, suggesting a two-hit model causing neurodegeneration in ALS."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["https://hdl.handle.net/1807/149794"],"dc:subject":["Amyotrophic Lateral Sclerosis","Autophagy","C9orf72","Mouse Model","Neurodegenerative Diseases","TDP-43"],"dc:title":["Investigating the Effects of C9orf72 Haploinsufficiency on TDP-43 Pathology in ALS"],"dc:type":["Thesis"]},"updated_at":"2026-07-27T21:28:05Z"}