UCLA

Dysfunction of the neuronal RNA binding protein RBFOX1 has been linked to epilepsy and autism spectrum disorders. Rbfox1 loss in mice leads to neuronal hyperexcitability and seizures, but the physiological basis for this is unknown. We identify the vSNARE protein Vamp1 as a major Rbfox1 target using high throughput RNA-seq and CLIP-seq in adult mouse brain. Vamp1 is strongly downregulated in Rbfox1 Nes-cKO mice due to loss of 3’ UTR binding byRbfox1. Using viral induction by AAVs and reporter assays in primary cultured neurons, we show that cytoplasmic Rbfox1 stimulates Vamp1 expression in part by blocking microRNA-9. We find that Vamp1 is specifically expressed in inhibitory neurons in vivo and in cultured neurons using immunofluorescence. Electrophysiological analyses in acute hippocampal slices show that both Vamp1 knockdown and Rbfox1 loss lead to decreased inhibitory synaptic transmission and E/I imbalance. To assay whether the inhibitory defects in the Rbfox1 cKO are due to Vamp1 loss, we then use stereotaxic injection of AAVs to re- express Vamp1 selectively within Rbfox1 cKO interneurons. Remarkably, re-expression of Vamp1 rescues the electrophysiological changes in the Rbfox1 cKO, indicating that Vamp1 loss is a major contributor to the Rbfox1 Nes-cKO phenotype. The regulation of interneuron-specific Vamp1 by Rbfox1 provides a paradigm for broadly expressed RNA- binding proteins performing specialized functions in defined neuronal subtypes.