SUMMARY
# Mechanism: Progranulin Loss and TDP-43 Pathology in FTD
## Background and Rationale
Frontotemporal dementia (FTD) represents the second most common early-onset dementia, with heterozygous mutations in the progranulin gene (GRN) accounting for 5-25% of familial cases. GRN haploinsufficiency leads to reduced progranulin protein levels, triggering a pathogenic cascade culminating in abnormal TDP-43 protein aggregation and neuronal dysfunction. This validation study employs human post-mortem brain
METHODOLOGY NOTES
Phase 1: Post-mortem tissue analysis (Weeks 1-8). Collect frozen frontal/temporal cortex samples from GRN mutation carriers (n=20), sporadic FTD cases (n=20), and age-matched controls (n=15). Perform immunohistochemistry using anti-progranulin (1:500, R&D Systems) and phospho-TDP-43 antibodies (1:1000, CosmoBio). Quantify progranulin levels via sandwich ELISA and assess TDP-43 aggregation burden using stereological counting methods. Phase 2: iPSC neuronal modeling (Weeks 9-20). Culture patient-derived iPSCs from GRN carriers (n=8) and healthy controls (n=6). Differentiate to cortical neurons using dual SMAD inhibition protocol over 35 days. Treat with lysosomal stressors (chloroquine 10μM, bafilomycin 100nM) to accelerate pathology. Monitor TDP-43 subcellular localization via immunofluorescence microscopy at days 21, 35, and 49. Assess neuronal viability using MTT assays and measure progranulin secretion in conditioned media. Phase 3: CSF biomarker validation (Weeks 21-24). Analyze cer