Antisense oligonucleotide silencing of FUS expression as a therapeutic approach in amyotrophic lateral sclerosis

Abstract

Fused in sarcoma (FUS) is an RNA-binding protein that is genetically and pathologically associated with rare and aggressive forms of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). To explore the mechanisms by which mutant FUS causes neurodegeneration in ALS-FTD, we generated a series of FUS knock-in mouse lines that express the equivalent of ALS-associated mutant FUSP525L and FUSΔEX14 protein. In FUS mutant mice, we show progressive, age-dependent motor neuron loss as a consequence of a dose-dependent gain of toxic function, associated with the insolubility of FUS and related RNA-binding proteins. In this disease-relevant mouse model of ALS-FUS, we show that ION363, a non-allele-specific FUS antisense oligonucleotide, efficiently silences Fus and reduces postnatal levels of FUS protein in the brain and spinal cord, delaying motor neuron degeneration. In a patient with ALS with a FUSP525L mutation, we provide preliminary evidence that repeated intrathecal infusions of ION363 lower wild-type and mutant FUS levels in the central nervous system, resulting in a marked reduction in the burden of FUS aggregates that are a pathological hallmark of disease. In mouse genetic and human clinical studies, we provide evidence in support of FUS silencing as a therapeutic strategy in FUS-dependent ALS and FTD.

Upregulation of β-catenin due to loss of miR-139 contributes to motor neuron death in amyotrophic lateral sclerosis

“…Depletion of FUS in healthy MN progenitors for 3 days failed to produce any change in miR-139 levels ( Figure 5 B). This suggested that miR-139 downregulation was not due to a loss of function of FUS, supporting recent work indicating that FUS-associated ALS is due to toxic gain of function ( Korobeynikov et al., 2022 ; Sharma et al., 2016 ). As FUS has been shown to regulate RNA polymerase II (RNAPII)-mediated transcription ( Schwartz et al., 2012 ), we hypothesized that mutant FUS may affect miR-139 at the transcriptional level.…”

Loss of Stathmin-2, a hallmark of TDP-43-associated ALS, causes motor neuropathy

“…The extensor digitorum longus (EDL) is a fast twitch muscle located on the lateral side of the lower leg. The soleus muscle, which primarily consists of slow twitch muscle fibers, is located on the posterior portion of the lower leg at roughly the same distal position as the EDL and is relatively spared in many mouse models of ALS ( Frey et al, 2000 ; Sharma et al, 2016 ; Spiller et al, 2016 ; Ebstein et al, 2019 ; Korobeynikov et al, 2022 ). Neither of these muscles showed endplate fragmentation, so we were able to quantify individual NMJs.…”

“…The EDL, a predominantly fast twitch muscle, displays extensive denervation, while the slow-twitch soleus muscle shows no denervation. The selective vulnerability of FF motor units is seen both in patients with ALS ( Dengler et al, 1990 ) and in mouse ALS models carrying pathogenic mutations in FUS ( Sharma et al, 2016 ; Korobeynikov et al, 2022 ), SOD1 ( Frey et al, 2000 ), and TDP-43 ( Spiller et al, 2016 ; Ebstein et al, 2019 ). Finally, the Stmn2 KO mice display sensory defects.…”

Loss of Stathmin-2, a hallmark of TDP-43-associated ALS, causes motor neuropathy

“…The EDL, a predominantly fast twitch muscle, displays extensive denervation, while the slow-twitch soleus muscle shows no denervation. The selective vulnerability of fast-fatigable motor units is seen both in patients with ALS (Dengler et al, 1990) and in mouse ALS models carrying pathogenic mutations in FUS (Sharma & Lyashchenko et al, 2016;Korobeynikov et al, 2022), SOD1 (Frey et al, 2000), and TDP-43 (Spiller et al, 2016, Ebstein et al, 2019. Finally, the Stmn2 KO mice display sensory defects.…”