A Druggable Genome Screen Identifies Modifiers of alpha-Synuclein Levels via a Tiered Cross-Species Validation Approach

Accumulation of alpha-Synuclein (alpha-Syn) causes Parkinson's disease (PD) as well as other synucleopathies. alpha-Syn is the major component of Lewy bodies and Lewy neurites, the proteinaceous aggregates that are a hallmark of sporadic PD. In familial forms of PD, mutations or copy number variations in SNCA (the alpha-Syn gene) result in a net increase of its protein levels. Furthermore, common risk variants tied to PD are associated with small increases of wild-type alpha-Syn levels. These findings are further bolstered by animal studies which show that overexpression of alpha-Syn is sufficient to cause PD-like features. Thus, increased alpha-Syn levels are intrinsically tied to PD pathogenesis and underscore the importance of identifying the factors that regulate its levels. In this study, we establish a pooled RNAi screening approach and validation pipeline to probe the druggable genome for modifiers of alpha-Syn levels and identify 60 promising targets. Using a cross-species, tiered validation approach, we validate six strong candidates that modulate alpha-Syn levels and toxicity in cell lines, Drosophila, human neurons, and mouse brain of both sexes. More broadly, this genetic strategy and validation pipeline can be applied for the identification of therapeutic targets for disorders driven by dosage-sensitive proteins.