title: Human SOD1 ALS Mutations in a Drosophila Knock-In Model Cause Severe Phenotypes and Reveal Dosage-Sensitive Gain- and Loss-of-Function Components.
abstract: Amyotrophic Lateral Sclerosis (ALS) is the most common adult-onset motor neuron disease and familial forms can be caused by numerous dominant mutations of the copper-zinc superoxide dismutase 1 (SOD1) gene. Substantial efforts have been invested in studying SOD1-ALS transgenic animal models; yet, the molecular mechanisms by which ALS-mutant SOD1 protein acquires toxicity are not well understood. ALS-like phenotypes in animal models are highly dependent on transgene dosage. Thus, issues of whether the ALS-like phenotypes of these models stem from overexpression of mutant alleles or from aspects of the SOD1 mutation itself are not easily deconvolved. To address concerns about levels of mutant SOD1 in disease pathogenesis, we have genetically engineered four human ALS-causing SOD1 point mutations (G37R, H48R, H71Y, and G85R) into the endogenous locus of Drosophila SOD1 (dsod) via ends-out homologous recombination and analyzed the resulting molecular, biochemical, and behavioral phenotypes. Contrary to previous transgenic models, we have recapitulated ALS-like phenotypes without overexpression of the mutant protein. Drosophila carrying homozygous mutations rendering SOD1 protein enzymatically inactive (G85R, H48R, and H71Y) exhibited neurodegeneration, locomotor deficits, and shortened life span. The mutation retaining enzymatic activity (G37R) was phenotypically indistinguishable from controls. While the observed mutant dsod phenotypes were recessive, a gain-of-function component was uncovered through dosage studies and comparisons with age-matched dsod null animals, which failed to show severe locomotor defects or nerve degeneration. We conclude that the Drosophila knock-in model captures important aspects of human SOD1-based ALS and provides a powerful and useful tool for further genetic studies.
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912.
authors.forename: Aslı
authors.initials: A
authors.lastname: Şahin
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912.
authors.forename: Aaron
authors.initials: A
authors.lastname: Held
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Bredvik
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912.
authors.forename: Paxton
authors.initials: P
authors.lastname: Major
authors.affiliation: Department of Biology, Rhode Island College, Providence, Rhode Island 02908.
authors.forename: Toni-Marie
authors.initials: TM
authors.lastname: Achilli
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912.
authors.forename: Abigail G
authors.initials: AG
authors.lastname: Kerson
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912.
authors.forename: Kristi
authors.initials: K
authors.lastname: Wharton
authors.affiliation: Department of Biology, Rhode Island College, Providence, Rhode Island 02908.
authors.forename: Geoff
authors.initials: G
authors.lastname: Stilwell
authors.affiliation: Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912 robert_reenan@brown.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Reenan
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics*; D000818:Animals; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D055879:Gene Knock-In Techniques; D006801:Humans; D008124:Locomotion; D008136:Longevity; D009046:Motor Neurons / Q000378:metabolism / Q000502:physiology; D010641:Phenotype; D000072105:Superoxide Dismutase-1 / Q000235:genetics*
chemical_list: D000072105:Superoxide Dismutase-1
keywords: ALS; Drosophila; SOD1; motor neuron