FMR PRO-DIA-FLOW - Frédéric Ebstein (2026-2028)

Neurodevelopmental proteasomopathies are ultra-rare genetic disorders caused by pathogenic variants in genes encoding 26S proteasome subunits. They are characterized by developmental delay, intellectual disability, behavioral abnormalities, and variable multisystem involvement. Although genome sequencing has accelerated gene discovery, functional interpretation of novel variants, particularly variants of uncertain significance (VUS), remains a major clinical challenge. No rapid and scalable functional assay is currently available. Leveraging our BioTND-UPS biobank (>500 PBMC samples from patients and controls), we identified a robust four-biomarker signature of proteasome dysfunction, including increased protein aggregation, enhanced mitophagy, type I interferon activation, and reduced proteasome activity. We propose to develop a multiplexed flow cytometry assay integrating these biomarkers into a composite dysfunction score for functional variant classification. The assay will first be validated in well-characterized patients and controls, then applied to individuals carrying VUS to assess its ability to improve variant interpretation. By combining cellular phenotyping and computational classification into a rapid, single-day workflow, this approach aims to bridge the gap between genomic diagnosis and functional validation. This tool has the potential to accelerate diagnosis, improve patient stratification, and guide therapeutic strategies in proteasomopathies, while providing a broader framework for other genetic disorders involving disrupted protein homeostasis.