Activity-dependent regulation of PGC-1α in PV+ interneurons

PRIMARY OUTCOME

Activity-dependent PGC-1α regulation

EXPECTED OUTCOMES

## Primary Outcomes **PGC-1α Upregulation**: Activity-dependent increase in PGC-1α protein levels by ≥1.8-fold (p < 0.01, Student's t-test) following 7 days of 8 Hz optogenetic stimulation in PV+ neurons. Peak expression at DIV 16. **Mitochondrial Adaptation**: Spare respiratory capacity increases by ≥40% in stimulated PV+ neurons vs. sham controls. Basal OCR elevated by ≥25%. ## Secondary Outcomes **Subtype Specificity**: PGC-1α induction is ≥3× higher in PV+ interneurons vs. neighboring excitatory neurons (vGlut1+) in mixed cultures, confirming cell-type specificity of activity-dependent regulation. **Functional Consequence**: PV+ interneurons showing enhanced PGC-1α expression display improved survival under metabolic stress conditions (glucose deprivation, 48 hours) with ≥30% reduction in TUNEL+ apoptotic cells.

SUCCESS CRITERIA

## Primary Success Criteria **PGC-1α Induction**: Activity-dependent stimulation must produce ≥1.5-fold increase in PGC-1α protein expression (normalized to β-actin) in PV+ neurons, with statistical significance at p < 0.05 (one-way ANOVA with Bonferroni post-hoc test, n ≥ 4 biological replicates). **Mitochondrial Function**: OCR spare capacity in stimulated PV+ neurons significantly exceeds unstimulated controls by ≥30% (p < 0.05). ## Secondary Success Criteria **Cell-Type Specificity**: PV-specific PGC-1α induction confirmed by co-localization analysis (Pearson's coefficient ≥0.7 between PV and PGC-1α immunostaining signal in stimulated cultures). **Dose-Response Relationship**: Incremental frequency stimulation (1 Hz, 4 Hz, 8 Hz, 15 Hz) produces graded PGC-1α response with EC₅₀ centered at 6-10 Hz range, confirming biological plausibility of activity coupling.

PROTOCOL

# Activity-Dependent Regulation of PGC-1α in PV+ Interneurons Protocol ## Phase 1: Primary Cortical Culture Preparation (Days 1-7) **Cell Culture**: Dissect cortex from P14-P18 C57BL/6 mice (both sexes). Dissociate neurons via papain digestion (20 U/mL, 37°C, 30 min). Plate at density 80,000 cells/cm² on poly-D-lysine/laminin-coated 12-well plates. Culture in Neurobasal-A supplemented with B-27, 0.5 mM L-glutamine, and 1× penicillin/streptomycin. Maintain at 37°C, 5% CO₂. **PV+ Interneuron Identification**: At DIV 14, verify PV+ interneuron population via immunocytochemistry: anti-parvalbumin (1:500, Abcam ab114246) and anti-GAD67 (1:200, Millipore MABN60). Count PV+ cells as percentage of DAPI+ nuclei (target: 15-25% PV+). ## Phase 2: Activity Manipulation Paradigm (Days 8-14) **Optogenetic Stimulation**: Transduce neurons at DIV 7 with AAV9-CaMKIIa-ChrimsonR-tdTomato (Addgene #62722) or AAV9-CaMKIIa-eArchT3.0-eYFP (control). Apply 8 Hz light pulses (473 nm, 10 ms pulses, 5 s on/5 s off for 30 min/day) for 7 consecutive days. **Chemogenetic Modulation**: For complementary experiments, apply DREADD hM3Dq (CNO, 5 μM) or hM4Di for 6 hours to modulate network activity. Measure spontaneous excitatory postsynaptic currents (sEPSCs) via patch clamp at DIV 14, 16, and 18. ## Phase 3: PGC-1α Expression Analysis (Days 15-21) **Molecular Analysis**: Extract protein at 4 timepoints (baseline DIV7, post-stimulation DIV14/16/18). Probe with anti-PGC-1α (1:500, Abcam ab191695) and anti-β-actin (1:5000). Quantify via western blot with HRP-conjugated secondary antibodies and chemiluminescent detection (GE ECL). Normalize PGC-1α signal to β-actin loading control. **Mitochondrial Function**: Measure mitochondrial mass via MitoTracker Deep Red FM (100 nM, 30 min, 37°C) and MitoSOX Red (5 μM, 10 min) for superoxide detection. Analyze via flow cytometry (Attune NxT) or high-content imaging (IN Cell 2200). ## Phase 4: Functional Validation (Days 22-28) **Respirometry**: Measure oxygen consumption rate (OCR) via Seahorse XFe96 Analyzer. Sequence: oligomycin (1 μg/mL), FCCP (0.75 μM), rotenone/antimycin A (0.5 μM). Calculate basal respiration, max capacity, and spare respiratory capacity. **ATF4 Target Analysis**: For mechanistic studies, include PGC-1α target gene panel: ATF4, ERR-α, NRF-1, NRF-2, and mitochondrial biogenesis markers (TFAM, COXI, ATP5A). Verify via qRT-PCR (ΔΔCt method).

LINKED HYPOTHESES

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