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AltFUS interactome from mitochondrial extracts

ABSTRACT: Novel functional coding sequences (altORFs) are camouflaged within annotated ones (CDS) in a different reading frame. We discovered an altORF nested in the FUS CDS encoding a conserved 170 amino acid protein, altFUS. AltFUS is endogenously expressed in human tissues, notably in the motor cortex and motor neurons. Overexpression of wild-type FUS and/or amyotrophic lateral sclerosis-linked FUS mutants is known to trigger toxic mechanisms in different models. These include an inhibition of autophagy, loss of mitochondrial potential, and accumulation of cytoplasmic aggregates. We show here that altFUS, not FUS, is responsible for the inhibition of autophagy. AltFUS is also pivotal in the mechanisms leading to the mitochondrial potential loss and accumulation of cytoplasmic aggregates. Suppression of altFUS expression in a Drosophila model of FUS-related toxicity protects against neurodegeneration. Some mutations found in ALS patients are overlooked because of their synonymous effect on the FUS protein. Yet we showed they exert a deleterious effect via their missense consequence on the overlapping altFUS protein. These findings demonstrate that FUS is a bicistronic gene and suggest that both proteins, FUS and altFUS, cooperate in toxic mechanisms.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Marie A Brunet

LAB HEAD: Roucou Xavier

PROVIDER: PXD021320 | Pride | 2020-10-12

REPOSITORIES: Pride

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Project description:FUS is an RNA-binding protein involved in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Cytoplasmic FUS-containing aggregates are often associated with concomitant loss of nuclear FUS. Whether loss of nuclear FUS function, gain of a cytoplasmic function, or a combination of both lead to neurodegeneration remains elusive. To address this question, we generated knock-in mice expressing mislocalized cytoplasmic FUS and complete FUS knock-out mice. Both mouse models display similar perinatal lethality with respiratory insufficiency, reduced body weight and length, and largely similar alterations in gene expression and mRNA splicing patterns, indicating that mislocalized FUS results in loss of its normal function. However, FUS knock-in mice, but not FUS knock-out mice, display reduced motor neuron numbers at birth, associated with enhanced motor neuron apoptosis, which can be rescued by cell-specific CRE-mediated expression of wild-type FUS within motor neurons. Together, our findings indicate that cytoplasmic FUS mislocalization not only leads to nuclear loss of function, but also triggers motor neuron death through a toxic gain of function within motor neurons. Total RNA from brains of E18.5 knock-in (FusÎNLS/ÎNLS), and knock-out (Fus-/-) mice and their control littermates were extracted with Trizol and libraries were prepared for RNA sequencing and RNA-mediated oligonucleotide Annealing, Selection, and Ligation with Next-Generation sequencing (RASL-seq) (Li et al. 2012; Zhou et al. 2012). For the RNA-seq experiment, biological replicates were used with n=4-5 knock-in animals per group (4 wild-type and 5 homozygous FusÎNLS) and n=5 knock-out animals per group (5 wild-type and 5 homozygous Fus-/-). For the RASL-seq analysis, biological replicates were used with n=4 knock-in animals per group (4 wild-type, 4 heterozygous and 4 homozygous FusÎNLS) and n=5 animals per group (5 wild-type and 5 homozygous Fus-/- knock-out).

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AltFUS interactome from mitochondrial extracts

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