Disrupted Autophagy and Neuronal Dysfunction in C. elegans Knock-in Models of FUS Amyotrophic Lateral Sclerosis

Abstract

It remains unclear how mutations in FUS, a ribonucleoprotein, lead to neuronal dysfunction in Amyotrophic Lateral Sclerosis (ALS) patients. To examine mechanisms underlying ALS FUS dysfunction, we generated the first C. elegans knock-in models using CRISPR/Cas9mediated genome editing, creating R524S and P525L ALS FUS models. Although FUS inclusions were not detected, ALS FUS animals showed defective neuromuscular function, as well as stressinduced locomotion defects. Unlike C. elegans lacking the endogenous FUS ortholog, ALS FUS animals had impaired neuronal autophagy and increased SQST-1 accumulation in ALS FUS motor neurons. Loss of sqst-1, the C. elegans ortholog for ALS-linked, autophagy adaptor protein SQSTM1/p62, suppressed both neuromuscular and stress-induced locomotion defects in ALS FUS animals, but did not suppress neuronal autophagy defects. Therefore, autophagy dysfunction is upstream of, and not dependent on, SQSTM1 function in ALS FUS pathogenesis.Combined, our findings demonstrate that autophagy dysfunction likely contributes to protein homeostasis and neuromuscular defects in ALS FUS knock-in animals.

Lipid droplets modulate proteostasis, SQST-1/SQSTM1 dynamics, and lifespan in C. elegans

“…Accordingly, SQST-1 over-expression may over-sensitize the animals to unstable, ubiquitination-prone proteins, posing an additional challenge to the autophagic machinery. This is exemplified by recent evidence that reducing SQST-1 specifically in the neurons of a nematode model of ALS is protective 61 , possibly since mutant fused in sarcoma (FUS) expression promotes SQST-1 accumulation, which exacerbates proteotoxicity and neurodegeneration. Notably, SQSTM1 can phase separate when interacting with ubiquitinated cargoes 62 , but the impact of the formation of these condensates on overall proteostasis is unclear.…”

Caenorhabditis elegans as a model system to evaluate neuroprotective potential of nano formulations

“…Likewise TDP-43, the mutation in the DNA/RNA-binding proteins, FUS, also aggregates protein to induce mortality impairment, and its overexpression alters synaptic functions (Ling et al, 2019). Several transgenic C. elegans models with mutated and overexpressed FUS gene has been developed (Vaccaro et al, 2012b;Murakami et al, 2012;Vérièpe et al, 2015;Ma et al, 2018;Markert et al, 2020;Labarre et al, 2021;Baskoylu et al, 2022). R524S and P525L mutated FUS transgenic ALS models for C. elegans have been created with impaired neuromuscular function and locomotion (Baskoylu et al, 2022).…”

“…Several transgenic C. elegans models with mutated and overexpressed FUS gene has been developed (Vaccaro et al, 2012b;Murakami et al, 2012;Vérièpe et al, 2015;Ma et al, 2018;Markert et al, 2020;Labarre et al, 2021;Baskoylu et al, 2022). R524S and P525L mutated FUS transgenic ALS models for C. elegans have been created with impaired neuromuscular function and locomotion (Baskoylu et al, 2022). With the advancement in genetic manipulation, Labarre et al (2021) recently developed a single copy FUS mutant transgenic strain of C. elegans, exhibiting similar ALS phenotypes, including GABAergic neurodegeneration with progressive paralysis.…”

Drug discovery: Insights from the invertebrate Caenorhabditis elegans

“…The first C. elegans model of a human ND was built 25 years ago, 178 and, since then, an extensive list of animal models for most of the NDs have been generated ( Table 3) (Table 3). [180][181][182] Since C. elegans has no orthologous gene for β-amyloid (Aβ), αsynuclein, or huntingtin, models of NDs have been essentially produced by transgenic overexpression of the disease causing-protein in either body-wall muscle cells, in all neurons or in a specific subset of neurons. 82,83,150,158,178,195,197,201 In most cases, the protein is tagged with GFP, which permits monitoring protein aggregation in whole live animals.…”

“…CRISP/Cas9 technology has been fortunately established in C. elegans 179 and recent single‐copy knock‐in models of some NDs have been developed (Table 3). 180–182 …”