Wild-type FUS corrects ALS-like disease induced by cytoplasmic mutant FUS through autoregulation

Abstract

Mutations in FUS, an RNA-binding protein involved in multiple steps of RNA metabolism, are associated with the most severe forms of amyotrophic lateral sclerosis (ALS). Accumulation of cytoplasmic FUS is likely to be a major culprit in the toxicity of FUS mutations. Thus, preventing cytoplasmic mislocalization of the FUS protein may represent a valuable therapeutic strategy. FUS binds to its own pre-mRNA creating an autoregulatory loop efficiently buffering FUS excess through multiple proposed mechanisms including retention of introns 6 and/or 7. Here, we introduced a wild-type FUS gene allele, retaining all intronic sequences, in mice whose heterozygous or homozygous expression of a cytoplasmically retained FUS protein (Fus∆NLS) was previously shown to provoke ALS-like disease or postnatal lethality, respectively. Wild-type FUS completely rescued the early lethality caused by the two Fus∆NLS alleles, and improved the age-dependent motor deficits and reduced lifespan caused by heterozygous expression of mutant FUS∆NLS. Mechanistically, wild-type FUS decreased the load of cytoplasmic FUS, increased retention of introns 6 and 7 in the endogenous mouse Fus mRNA, and decreased expression of the mutant mRNA. Thus, the wild-type FUS allele activates the homeostatic autoregulatory loop, maintaining constant FUS levels and decreasing the mutant protein in the cytoplasm. These results provide proof of concept that an autoregulatory competent wild-type FUS expression could protect against this devastating, currently intractable, neurodegenerative disease.

Disruption of MAM integrity in mutant FUS oligodendroglial progenitors from hiPSCs

“…The homeostasis of FUS protein levels is controlled by autoregulatory mechanisms involving the retention of intron 6 and 7 [ 33 , 81 ]. Furthermore, mutations in the NLS domain lead to the reduction of FUS exon 6 and 6 repression, contributing to FUS abnormal cytoplasmic accumulation [ 33 , 81 ]. Using RT-PCR, we calculated the percentage of intron 6/7 retention in mutant FUS OPCs and their isogenic controls.…”

“…We demonstrated that FUS mislocalizes in the cytoplasm of mutant OPCs, consistent with previous reports on oligodendrocytes in FUS mouse model and FUS -ALS patients [ 58 , 82 , 90 ]. Recent studies found that mutant FUS autoregulatory mechanisms are altered and contribute to its cytoplasmic accumulation [ 33 , 81 ]. Consistent with the immunofluorescence data, a significant decrease in intron 6 and 7 retention was identified in OPCs with FUS NLS mutations.…”

FUS-mediated HypEVs: Neuroprotective effects against ischemic stroke

“…RBPs, including FUS, can selectively bind to specific RNAs and transport them into sEVs [ 16 , 19 ]. FUS, a highly conserved protein, was initially identified as a fusion oncogene in human liposarcomas [ 37 ] and has been shown to play a critical role in normal central nervous system development and neuron survival [ 38 , 39 ]. FUS mutations have been linked to neurodegenerative disorders, such as ALS and frontotemporal dementia (FTD) [ 40 , 41 ], making FUS a key target for therapeutic intervention.…”

Functional consequences of familial ALS‐associated SOD1L84F in neuronal and muscle cells

“…Primer sequences are provided in Table S2. For FUS autoregulation, primer sequences were used as described previously 27 …”