Alzheimer’s Disease-Associated U1 Snrnp Splicing Dysfunction Causes Neuronal Hyperexcitability and Cognitive Impairment

Recent proteome and transcriptome profiling of Alzheimer’s disease (AD) brains reveals RNA splicing dysfunction and U1 small nuclear ribonucleoprotein (snRNP) pathology containing U1-70K and its N-terminal 40-KDa fragment (N40K). Here we present a causative role of U1 snRNP dysfunction to neurodegeneration in primary neurons and transgenic mice (N40K-Tg), in which N40K expression exerts a dominant-negative effect to downregulate full-length U1-70K. N40K-Tg recapitulates N40K insolubility, erroneous splicing events, neuronal degeneration and cognitive impairment. Specifically, N40K-Tg shows the reduction of GABAergic synapse components (for example, the GABA receptor subunit of GABRA2) and concomitant postsynaptic hyperexcitability that is rescued by a GABA receptor agonist. Crossing of N40K-Tg and the 5xFAD amyloidosis model indicates that the RNA splicing defect synergizes with the amyloid cascade to remodel the brain transcriptome and proteome, deregulate synaptic proteins and accelerate cognitive decline. Thus, our results support the contribution of U1 snRNP-mediated splicing dysfunction to AD pathogenesis. Splicing dysfunction has been observed in Alzheimer’s disease but it remains unclear whether splicing defects have a causal role. Here the authors generate a mouse model with perturbed U1 snRNP activity, recapitulating RNA splicing defects, neuron hyperexcitability, neurodegeneration and synergy with the amyloid cascade when crossed with 5xFAD mice.