Why do GRN and C9orf72 mutations show heterogeneous tau/TDP-43 distributions unlike MAPT?

MAPT mutations produced consistent [18F]AV-1451 binding patterns while GRN and C9orf72 mutations showed heterogeneous distributions. This unexplained difference could reveal distinct pathogenic mechanisms across familial FTD subtypes.

Gap type: unexplained_observation Source paper: In vivo PET imaging of neuroinflammation in familial frontotemporal dementia. (2021, Journal of neurology, neurosurgery, and psychiatry, PMID:33122395)

{“resolution_pipeline”: “scidex.atlas.gap_closure_pipeline”, “task_id”: “f4f7b129-0f43-4c84-abd8-20d4e701842d”, “evaluated_at”: “2026-04-28T19:10:42.165696+00:00”, “resolution_summary”: “Resolved by hypothesis h-72c719461c: C9orf72 ASO Treatment Reverses TDP-43 Pathology in ALS/FTD. Supporting evidence includes debate sess_SDA-2026-04-07-gap-pubmed-20260406-062202-094b44bf_task_9aae8fc5.”, “match_counts”: {“hypothesis_matches”: 2, “debate_matches”: 5, “paper_matches”: 0}, “hypothesis_matches”: [{“id”: “h-72c719461c”, “title”: “C9orf72 ASO Treatment Reverses TDP-43 Pathology in ALS/FTD”, “score”: 0.357, “reason”: “5 token overlaps; entity overlap: ftd, tdp-43”, “analysis_id”: “test-hypothesis-fixtures-v1”, “target_gene”: “C9orf72”, “target_pathway”: null, “disease”: “neurodegeneration”, “composite_score”: 0.72, “confidence_score”: 0.88, “status”: “proposed”, “pubmed_evidence_ids”: [“21944792”, “28960178”, “29460270”, “39605053”, “40520109”]}, {“id”: “h-var-a0933e666d”, “title”: “Microglial AIM2 Inflammasome as the Primary Driver of TDP-43 Proteinopathy Neuroinflammation in ALS/FTD”, “score”: 0.302, “reason”: “11 token overlaps; entity overlap: ftd, tdp-43”, “analysis_id”: “SDA-2026-04-01-gap-20260401-225149”, “target_gene”: “AIM2, CASP1, IL1B, PYCARD, TARDBP”, “target_pathway”: “Microglial AIM2 inflammasome activation via phagocytosed neuron-derived mtDNA in TDP-43 proteinopathy”, “disease”: “neurodegeneration”, “composite_score”: 0.8240000000000001, “confidence_score”: 0.76, “status”: “proposed”, “pubmed_evidence_ids”: [“27519954”, “28506519”, “29263430”, “29643512”, “30610225”]}], “debate_matches”: [{“id”: “sess_SDA-2026-04-07-gap-pubmed-20260406-062202-094b44bf_task_9aae8fc5”, “title”: “TDP-43 inclusions occur in AD, ALS, and FTLD but the pathogenic mechanisms leading to TDP-43 pathology may differ between diseases. Understanding disease-specific drivers could reveal why TDP-43 shows limbic distribution in AD versus other patterns in ALS/FTLD.\n\nGap type: unexplained_observation\nSource paper: TDP-43 Pathology in Alzheimer’s Disease. (2021, Mol Neurodegener, PMID:34930382)”, “score”: 0.523, “reason”: “9 token overlaps; entity overlap: pmid, tdp-43”, “analysis_id”: “SDA-2026-04-07-gap-pubmed-20260406-062202-094b44bf”, “quality_score”: 0.697, “status”: “completed”, “target_artifact_id”: null, “target_artifact_type”: null}, {“id”: “sess_SDA-2026-04-07-gap-pubmed-20260406-062202-c8c5a9a1_task_9aae8fc5”, “title”: “The abstract identifies APOE4 association with increased TDP-43 pathology but the mechanistic link is unexplained. This connection could reveal novel therapeutic targets since APOE4 is the strongest genetic risk factor for AD.\n\nGap type: unexplained_observation\nSource paper: TDP-43 Pathology in Alzheimer’s Disease. (2021, Mol Neurodegener, PMID:34930382)”, “score”: 0.512, “reason”: “9 token overlaps; entity overlap: pmid, tdp-43”, “analysis_id”: “SDA-2026-04-07-gap-pubmed-20260406-062202-c8c5a9a1”, “quality_score”: 0.61, “status”: “completed”, “target_artifact_id”: null, “target_artifact_type”: null}, {“id”: “sess_SDA-2026-04-08-gap-pubmed-20260406-062202-5c32c50a_task_9aae8fc5”, “title”: “AD patients with TDP-43 pathology show worse cognitive impairment, but how TDP-43 mechanistically contributes to this severity is unknown. Understanding this could identify TDP-43 as a therapeutic target for cognitive preservation in AD.\n\nGap type: unexplained_observation\nSource paper: TDP-43 Pathology in Alzheimer’s Disease. (2021, Mol Neurodegener, PMID:34930382)”, “score”: 0.507, “reason”: “8 token overlaps; entity overlap: pmid, tdp-43”, “analysis_id”: “SDA-2026-04-08-gap-pubmed-20260406-062202-5c32c50a”, “quality_score”: 0.734, “status”: “completed”, “target_artifact_id”: null, “target_artifact_type”: null}, {“id”: “sess_SDA-2026-04-08-gap-pubmed-20260406-062141-739c7f1c_task_9aae8fc5”, “title”: “While the study demonstrates TDP-43 triggers mPTP-mediated mtDNA release, the molecular mechanism by which TDP-43 pathology leads to mPTP opening is not explained. Identifying this upstream trigger could reveal more proximal therapeutic targets than downstream cGAS/STING inhibition.\n\nGap type: unexplained_observation\nSource paper: TDP-43 Triggers Mitochondrial DNA Release via mPTP to Activate cGAS/STING in ALS. (2020, Cell, PMID:33031745)”, “score”: 0.463, “reason”: “8 token overlaps; entity overlap: pmid, tdp-43”, “analysis_id”: “SDA-2026-04-08-gap-pubmed-20260406-062141-739c7f1c”, “quality_score”: 0.772, “status”: “completed”, “target_artifact_id”: null, “target_artifact_type”: null}, {“id”: “sess_SDA-2026-04-08-gap-pubmed-20260406-062207-5a703c17”, “title”: “While the abstract establishes that intercellular transmission occurs for various proteins (tau, α-synuclein, TDP-43), the mechanisms governing transmission selectivity and efficiency remain poorly understood. This gap impedes development of transmission-blocking therapeutics.\n\nGap type: unexplained_observation\nSource paper: Protein transmission in neurodegenerative disease. (2020, Nat Rev Neurol, PMID:32203399)”, “score”: 0.46, “reason”: “7 token overlaps; entity overlap: pmid, tdp-43”, “analysis_id”: “SDA-2026-04-08-gap-pubmed-20260406-062207-5a703c17”, “quality_score”: 0.95, “status”: “completed”, “target_artifact_id”: null, “target_artifact_type”: null}], “paper_matches”: []}