M6A reduction relieves FUS-associated ALS granules

Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease due to gradual motoneurons (MN) degeneration. Among the processes associated to ALS pathogenesis, there is the formation of cytoplasmic inclusions produced by aggregation of mutant proteins, among which the RNA binding protein FUS. Here we show that, in neuronal cells and in iPSC-derived MN expressing mutant FUS, such inclusions are significantly reduced in number and dissolve faster when the RNA m⁶A content is diminished. Interestingly, stress granules formed in ALS conditions showed a distinctive transcriptome with respect to control cells, which reverted to similar to control after m⁶A downregulation. Notably, cells expressing mutant FUS were characterized by higher m⁶A levels suggesting a possible link between m⁶A homeostasis and pathological aggregates. Finally, we show that FUS inclusions are reduced also in patient-derived fibroblasts treated with STM-2457, an inhibitor of METTL3 activity, paving the way for its possible use for counteracting aggregate formation in ALS.

In Amyotrophic Lateral Sclerosis (ALS), formation of cytoplasmic inclusions by mutant protein aggregation is observed. Here the authors show that these inclusions dissolve faster when m⁶A RNA modification is inhibited in ALS cellular models.