Clinical characterization of GABRA1/GABRG2 microdeletion patient

PRIMARY OUTCOME

clinical phenotype characterization

EXPECTED OUTCOMES

1. **aCGH reveals exact breakpoints:** Microdeletion spans 142-158kb on chromosome 5q34, encompassing GABRA1 (ENST00000406563) and GABRG2 (ENST00000329208) with no other RefSeq genes disrupted 2. **GABRA1/GABRG2 mRNA levels reduced to 23% ± 4% of control** (mean ± SD, n=3 technical replicates, p<0.001, two-tailed t-test) as measured by RT-qPCR 3. **Western blot quantification:** GABRA1 protein at 31% ± 7% of control; GABRG2 at 28% ± 5% of control (densitometry, ImageJ normalization to β-actin) 4. **EEG shows:** Interictal epileptiform discharges at 2.3 ± 0.8 Hz frequency, predominantly in bilateral occipital regions, with global background slowing to theta range (4-7 Hz) 5. **OCT-RNFL thickness reduced to 68 ± 5 μm** (patient) vs 94 ± 6 μm (age-matched controls, n=15), representing ~28% thinning (p<0.001) 6. **MEG spike source localization:** Maximum current density in calcarine cortex (MNI coordinates: x=±7, y=-90, z=3), consistent with visual cortex hyperexcitability 7. **iPSC neurons show GABA-A receptor current amplitude reduction to 42% ± 9% of control** (pA: patient 28.4 ± 6.2 pA vs control 67.8 ± 8.3 pA, n=12 cells, p<0.0001, Mann-Whitney U test) ---

SUCCESS CRITERIA

- **Molecular confirmation:** aCGH identifies microdeletion encompassing GABRA1/GABRG2 with breakpoint precision ±5kb, confirmed by orthogonal methods (ddPCR or MLPA) - **Protein reduction threshold:** GABA-A receptor subunit proteins reduced to <40% of age-matched control levels on ≥2 independent Western blot experiments (p<0.01, effect size Cohen's d >1.5) - **Clinical phenotype documentation:** Complete neurological, ophthalmological, and neuropsychological assessment performed per protocol with <5% missing data - **Seizure characterization:** Capture ≥3 spontaneous seizures on video-EEG to classify epilepsy type per ILAE criteria; interictal discharge frequency reproducibly quantified - **Statistical power for primary endpoint:** If total n=1 case study, ≥80% power to detect large effect (Cohen's d >1.0) against historical controls using single-case statistical methods (Crawford's Modified t-test) - **Longitudinal tracking:** ≥80% follow-up compliance at Month 12 endpoint; OCT-RNFL and plasma NFL measured at ≥3 timepoints to enable trend analysis - **Functional validation:** iPSC-derived neurons demonstrate ≥50% reduction in GABA-A mediated current amplitude vs isogenic control line (p<0.05, Bonferroni-corrected for multiple comparisons)

PROTOCOL

### Phase 1: Initial Clinical Assessment (Day 0) **Objective:** Establish baseline phenotype and confirm molecular diagnosis - **Neurological examination:** Complete motor, sensory, reflex, cranial nerve assessment - **Ophthalmological evaluation:** Visual acuity (Snellen), fundoscopy, OCT retinal nerve fiber layer (RNFL) thickness, visual field perimetry (Humphrey 24-2) - **EEG:** 32-channel EEG (International 10-20 system), 60-minute recording including sleep - **MRI Brain:** 3T MRI with T1-weighted MPRAGE, T2-FLAIR, diffusion tensor imaging (DTI), susceptibility-weighted imaging (SWI), optimized for optic nerve visualization **Reagents/Equipment:** - MRI: Siemens Prisma 3T - EEG: Nihon Kohden JE-120 amplifier - OCT: Spectralis HRA+OCT (Heidelberg Engineering) **Controls:** Age/sex-matched historical control EEG/MRI data from literature --- ### Phase 2: Molecular Characterization (Days 1-7) **Objective:** Confirm microdeletion breakpoints and characterize transcriptional consequences - **DNA extraction:** Peripheral blood mononuclear cells (PBMCs) using QIAamp DNA Blood Mini Kit (Qiagen) - **aCGH (Array Comparative Genomic Hybridization):** Agilent 180K oligonucleotide array for precise breakpoint mapping - **WES (Whole Exome Sequencing):** Illumina NovaSeq 6000, 150bp paired-end, 100x coverage minimum - **cDNA analysis:** RNA extracted from patient-derived lymphoblastoid cell lines (transformed with EBV), subject to: - RT-qPCR for GABRA1 and GABRG2 expression: TaqMan assays (Thermo Fisher Hs00161575_m1, Hs00181333_m1) - Western blot: Primary antibodies anti-GABRA1 (Abcam ab1545, 1:500), anti-GABRG2 (Abcam ab157436, 1:500), anti-β-actin (Sigma A5441, 1:5000) as loading control - Secondary: HRP-conjugated anti-rabbit IgG (Cell Signaling 7074, 1:5000) - ECL detection: SuperSignal West Femto (Thermo Fisher 34096) **Controls:** - Patient baseline (pre-symptom if available) - Age-matched healthy donor PBMCs - Public expression data: GTEx database for matched tissue comparisons --- ### Phase 3: Neurophysiological Profiling (Days 8-14) **Objective:** Define seizure characteristics and establish electrophysiological biomarkers - **Long-term video-EEG monitoring:** 72-hour continuous monitoring to capture ≥3 spontaneous seizures - **MEG (Magnetoencephalography):** 306-channel MEG ( Elekta Neuromag TRIUX) for interictal spike localization - **Evoked potentials:** Visual evoked potentials (VEP) using pattern-reversal checkerboard (1° check, 2 Hz reversal), pattern electroretinography (PERG) - **Transcranial magnetic stimulation (TMS):** Single and paired-pulse TMS for cortical excitability assessment (Magstim Rapid2) **Equipment:** - EEG: Nihon Kohden EEG-1200 - MEG: Elekta Neuromag TRIUX - TMS: Magstim Rapid2 with figure-of-eight coil **Controls:** Historical cohort data from 20 age/sex-matched epilepsy patients with focal seizures --- ### Phase 4: Advanced Imaging (Days 15-21) **Objective:** Quantify structural and functional brain alterations - **7T MRI:** Ultra-high field MRI for subcortical structure visualization - T2*-weighted imaging for iron deposition in basal ganglia - MR spectroscopy: TE=30ms, PRESS sequence, voxels placed in occipital cortex and thalamus - Quantitative susceptibility mapping (QSM) for optic nerve iron quantification - **FDG-PET:** 18F-fluorodeoxyglucose PET/CT for regional glucose metabolism - **OCT-Angiography:** Quantify retinal microvasculature and ganglion cell complex (GCC) thickness **Controls:** Published normative 7T MRI values from age-matched controls (n≥30) --- ### Phase 5: Longitudinal Monitoring (Months 1, 3, 6, 12) **Objective:** Track disease progression and treatment response - **Monthly assessments:** Seizure diary review, adverse event recording, Vineland Adaptive Behavior Scales (VABS-III) - **Quarterly:** OCT-RNFL measurement, video-EEG (24hr), plasma biomarker panel (NFL, tau, GFAP via Simoa analyzer) - **Annual:** Comprehensive neuropsychological battery (WAIS-IV, WMS-IV, Trails A/B, Stroop) **Biomarker assays:** - Neurofilament light (NFL): NFL Simoa assay (UBio 102-153) - Total tau: Tau kit (Fujirebio HK-Tau) - GFAP: GFAP kit (LU-HSF10) **Controls:** Published normative values for age-matched population; historical data from Dravet syndrome cohort (closest genetic epilepsy comparator) --- ### Phase 6: Functional Validation (Months 1-6, parallel to Phase 5) **Objective:** Establish cellular phenotype of patient mutation - **Patient-derived iPSCs:** Reprogramming of PBMCs using CytoTune-iPS 2.0 Sendai kit (Thermo Fisher) - **Neuronal differentiation:** Dual-SMAD inhibition protocol, 35-day differentiation to cortical excitatory neurons - **Electrophysiology:** - Whole-cell patch clamp: Record GABA-A receptor currents (EPC-10 amplifier, HEKA) - Drug responses: Picrotoxin (100 μM), Diazepam (1 μM), THIP (10 μM) application - Miniature excitatory postsynaptic currents (mEPSCs): Recorded at -70mV, filtered at 2kHz **Controls:** - Isogenic correction line (CRISPR-Cas9) - Age/sex-matched control iPSC line - Scrambled siRNA (Qiagen SI00154213) for knockdown validation ---

LINKED HYPOTHESES

Prediction Markets (1 direct, 0 via hypothesis — 1 total)

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[Clinical characterization of GABRA1/GABRG2 microdeletion patient](http://scidex.ai/artifact/exp-fc5a2ff3-d66b-4050-82ee-2235b47956fb)

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