FUS Mislocalization Rewires a Cortical Gene Network to Drive Cognitive and Behavioral Impairment in ALS.

Cognitive and behavioral impairment affects up to half of individuals with amyotrophic lateral sclerosis (ALS), but their molecular origin remains unresolved. Here, we identify mislocalization of the RNA-binding protein FUS in cortical neurons as a defining feature in ALS patients with cognitive impairment (ALS-ci). Selective mislocalization of FUS in adult cortical projection neurons in mice is sufficient to trigger ALS-ci- and ALS with behavioral impairment (ALS-bi)-like phenotypes, including deficits in sociability, and neurodegeneration. Single-nucleus transcriptomics reveal a conserved FUS-dependent gene network downregulated in these mice and ALS-ci patients. This regulon is enriched for ALS genetic risk factors and newly implicates in ALS-bi. Carriers of protein-truncating variants display behavioral abnormalities, frontotemporal atrophy, and increased levels of dementia-linked biomarkers. These findings define a neuron-intrinsic mechanism for cognitive and behavioral dysfunction in ALS and nominate FUS mislocalization and its downstream gene network as therapeutic targets.