title: Characterization of two novel SETX mutations in AOA2 patients reveals aspects of the pathophysiological role of senataxin.
abstract: Ataxia with oculomotor apraxia (AOA) type 2 (AOA2 MIM 606002) is a recessive subtype of AOA characterized by cerebellar atrophy, oculomotor apraxia, early loss of reflexes, and peripheral neuropathy. Various mutations either in homozygous or compound heterozygous condition were so far identified in the associated gene SETX (MIM 608465). SETX encodes a large protein called senataxin with a DNA-RNA helicase domain and a putative N-terminus protein interaction domain. Here, we report the identification of two novel homozygous mutations in SETX gene, c.340_342delCTT (p.L114Del) and c.1669C > T (p.R557X), in two AOA2 families. The characterization of the mutant lymphoblastoid cell lines for sensitivity to oxidative DNA-damaging agents indicates that the p.L114Del deletion confers an increased sensitivity to H2O2, camptothecin, and mitomycin C, previously found to induce death in lymphoblasts harbouring other SETX mutations; the cells carrying the nonsense mutation display instead values within the normal range. Further analysis of a neuronal cell model SKNBE, transfected with the mutant senataxin proteins, reveals increased sensitivity also to staurosporine and excitotoxicity associated with the p.L114Del mutant only. We also demonstrate that the sensitizing effect of p.L114Del on apoptosis can be reversed by senataxin silencing. The ability of a single amino acid deletion to sensitize cells to death by different agents, compared to the lack of effect of a whole protein deletion, seems to exclude a protective role played by the native protein while suggesting that a specific mutation confers to the protein the ability to enhance the toxic effect of various cell damaging agents.
authors: Laboratory of Molecular Biology, E. Medea Scientific Institute, Via d. L. Monza 20, 23842, Bosisio Parini, Lecco, Italy.
authors: Giovanni
authors: G
authors: Airoldi
authors: Andrea
authors: A
authors: Guidarelli
authors: Orazio
authors: O
authors: Cantoni
authors: Chris
authors: C
authors: Panzeri
authors: Chiara
authors: C
authors: Vantaggiato
authors: Sara
authors: S
authors: Bonato
authors: Maria
authors: M
authors: Grazia D'Angelo
authors: Sestina
authors: S
authors: Falcone
authors: Clara
authors: C
authors: De Palma
authors: Alessandra
authors: A
authors: Tonelli
authors: Claudia
authors: C
authors: Crimella
authors: Sara
authors: S
authors: Bondioni
authors: Nereo
authors: N
authors: Bresolin
authors: Emilio
authors: E
authors: Clementi
authors: Maria Teresa
authors: MT
authors: Bassi
mesh_terms: D000328:Adult; D017209:Apoptosis; D020240:Apraxia, Ideomotor / Q000235:genetics*; D001259:Ataxia / Q000235:genetics*; D002166:Camptothecin / Q000494:pharmacology; D004249:DNA Damage; D004265:DNA Helicases; D005128:Eye Diseases / Q000235:genetics*; D005260:Female; D006720:Homozygote; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D016685:Mitomycin / Q000494:pharmacology; D064251:Multifunctional Enzymes; D009154:Mutation; D010375:Pedigree; D020365:RNA Helicases / Q000235:genetics*
chemical_list: D064251:Multifunctional Enzymes; D016685:Mitomycin; D006861:Hydrogen Peroxide; C484368:SETX protein, human; D004265:DNA Helicases; D020365:RNA Helicases; D002166:Camptothecin