Integrative transcriptome-wide association analyses reveal PRKCG-linked GABAergic dysfunction in Fragile X-associated tremor/ataxia syndrome

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by CGG repeat expansions in the FMR1 gene. While CGG repeat toxicity is established, the precise molecular mechanisms driving neurodegeneration remain unclear. Here, we show that a multi-omics strategy combined with TWAS reveals brain-region-specific molecular signatures and striking gene dysregulation in inhibitory neurons. Using conditional mouse models, we demonstrate that selective expression of expanded CGG repeats in GABAergic neurons is sufficient to recapitulate key pathologic hallmarks of FXTAS. We identify PRKCG as a genetic modifier of FXTAS, with cross-species evidence linking its overexpression to disease onset. Many dysregulated mRNAs in GABAergic neurons are targets of hnRNPA2/B1, an RNA-binding protein sequestered by CGG repeat RNA. Functional screening in Drosophila further establishes PRKCG as a potent modulator of CGG-associated neurotoxicity. These findings uncover a critical role of GABAergic neurons in FXTAS pathogenesis and position PRKCG as a promising therapeutic target.