title: ALS-associated mutations in FUS disrupt the axonal distribution and function of SMN.
abstract: Mutations in the RNA binding protein fused in sarcoma/translated in liposarcoma (FUS/TLS) cause amyotrophic lateral sclerosis (ALS). Although ALS-linked mutations in FUS often lead to a cytosolic mislocalization of the protein, the pathogenic mechanisms underlying these mutations remain poorly understood. To gain insight into these mechanisms, we examined the biochemical, cell biological and functional properties of mutant FUS in neurons. Expression of different FUS mutants (R521C, R521H, P525L) in neurons caused axonal defects. A protein interaction screen performed to explain these phenotypes identified numerous FUS interactors including the spinal muscular atrophy (SMA) causing protein survival motor neuron (SMN). Biochemical experiments showed that FUS and SMN interact directly and endogenously, and that this interaction can be regulated by FUS mutations. Immunostaining revealed co-localization of mutant FUS aggregates and SMN in primary neurons. This redistribution of SMN to cytosolic FUS accumulations led to a decrease in axonal SMN. Finally, cell biological experiments showed that overexpression of SMN rescued the axonal defects induced by mutant FUS, suggesting that FUS mutations cause axonal defects through SMN. This study shows that neuronal aggregates formed by mutant FUS protein may aberrantly sequester SMN and concomitantly cause a reduction of SMN levels in the axon, leading to axonal defects. These data provide a functional link between ALS-linked FUS mutations, SMN and neuronal connectivity and support the idea that different motor neuron disorders such as SMA and ALS may be caused, in part, by defects in shared molecular pathways.
authors.affiliation: Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Ewout J N
authors.initials: EJ
authors.lastname: Groen
authors.forename: Katsumi
authors.initials: K
authors.lastname: Fumoto
authors.forename: Anna M
authors.initials: AM
authors.lastname: Blokhuis
authors.forename: Jooyeon
authors.initials: J
authors.lastname: Engelen-Lee
authors.forename: Yeping
authors.initials: Y
authors.lastname: Zhou
authors.forename: Dianne M A
authors.initials: DM
authors.lastname: van den Heuvel
authors.forename: Max
authors.initials: M
authors.lastname: Koppers
authors.forename: Femke
authors.initials: F
authors.lastname: van Diggelen
authors.forename: Jessica
authors.initials: J
authors.lastname: van Heest
authors.forename: Jeroen A A
authors.initials: JA
authors.lastname: Demmers
authors.forename: Janine
authors.initials: J
authors.lastname: Kirby
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Shaw
authors.forename: Eleonora
authors.initials: E
authors.lastname: Aronica
authors.forename: Wim G M
authors.initials: WG
authors.lastname: Spliet
authors.forename: Jan H
authors.initials: JH
authors.lastname: Veldink
authors.forename: Leonard H
authors.initials: LH
authors.lastname: van den Berg
authors.forename: R Jeroen
authors.initials: RJ
authors.lastname: Pasterkamp
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D045744:Cell Line, Tumor; D015870:Gene Expression; D020439:Growth Cones / Q000648:ultrastructure; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009046:Motor Neurons / Q000378:metabolism* / Q000648:ultrastructure; D009154:Mutation; D010641:Phenotype; D034702:RNA-Binding Protein FUS / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D055533:Survival of Motor Neuron 1 Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection
chemical_list: D034702:RNA-Binding Protein FUS; C526472:Smn1 protein, mouse; D055533:Survival of Motor Neuron 1 Protein