SUMMARY
# FTD Microglia Role: Protective vs Destructive Mechanism Study
## Background and Rationale
Validation experiment to determine whether microglia play a predominantly protective or destructive role in frontotemporal dementia (FTD), using conditional microglial depletion and repopulation in progranulin-deficient (GRN-/-) mice.
**Protocol**: GRN-/- mice (FTD model) at 6 months (pre-symptomatic) and 12 months (symptomatic), n=20 per group: (1) PLX5622 (CSF1R inhibitor) diet for microglial depletion
METHODOLOGY NOTES
1. **Subject Selection**: Breed GRN-/- mice and wild-type littermates. At 6 months (pre-symptomatic, n=80) and 12 months (symptomatic, n=80), randomly assign to four treatment groups (n=20 each): PLX5622 depletion/repopulation, TREM2 antibody activation, vehicle control, and wild-type control. 2. **Baseline Assessment**: Conduct behavioral battery including marble burying test (30 marbles, 30min), social interaction chamber (10min sessions), and Morris water maze (5 days acquisition, 24h probe trial). Collect baseline CSF via cisterna magna puncture for neurofilament light chain quantification by ELISA. 3. **Treatment Phase**: Group 1 receives PLX5622-formulated chow (1200mg/kg) for 14 days to achieve >95% microglial depletion (confirmed by Iba1 immunostaining), followed by normal chow for 14 days repopulation. Group 2 receives TREM2-activating antibody (AL002c, 30mg/kg i.p., twice weekly for 4 weeks). Groups 3-4 receive respective vehicle controls. 4. **Interventional Monitoring**: We