title: Modeling pathogenic mutations of human twinkle in Drosophila suggests an apoptosis role in response to mitochondrial defects.
abstract: The human gene C10orf2 encodes the mitochondrial replicative DNA helicase Twinkle, mutations of which are responsible for a significant fraction of cases of autosomal dominant progressive external ophthalmoplegia (adPEO), a human mitochondrial disease caused by defects in intergenomic communication. We report the analysis of orthologous mutations in the Drosophila melanogaster mitochondrial DNA (mtDNA) helicase gene, d-mtDNA helicase. Increased expression of wild type d-mtDNA helicase using the UAS-GAL4 system leads to an increase in mtDNA copy number throughout adult life without any noteworthy phenotype, whereas overexpression of d-mtDNA helicase containing the K388A mutation in the helicase active site results in a severe depletion of mtDNA and a lethal phenotype. Overexpression of two d-mtDNA helicase variants equivalent to two human adPEO mutations shows differential effects. The A442P mutation exhibits a dominant negative effect similar to that of the active site mutant. In contrast, overexpression of d-mtDNA helicase containing the W441C mutation results in a slight decrease in mtDNA copy number during the third instar larval stage, and a moderate decrease in life span in the adult population. Overexpression of d-mtDNA helicase containing either the K388A or A442P mutations causes a mitochondrial oxidative phosphorylation (OXPHOS) defect that significantly reduces cell proliferation. The mitochondrial impairment caused by these mutations promotes apoptosis, arguing that mitochondria regulate programmed cell death in Drosophila. Our study of d-mtDNA helicase overexpression provides a tractable Drosophila model for understanding the cellular and molecular effects of human adPEO mutations.
authors.affiliation: Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, and Centro de Investigación Biomédica en Red en Enfermedades Raras, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Sanchez-Martinez
authors.forename: Manuel
authors.initials: M
authors.lastname: Calleja
authors.forename: Susana
authors.initials: S
authors.lastname: Peralta
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Matsushima
authors.forename: Rosana
authors.initials: R
authors.lastname: Hernandez-Sierra
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Whitworth
authors.forename: Laurie S
authors.initials: LS
authors.lastname: Kaguni
authors.forename: Rafael
authors.initials: R
authors.lastname: Garesse
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D049109:Cell Proliferation; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics*; D004195:Disease Models, Animal; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008136:Longevity / Q000235:genetics; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D028361:Mitochondrial Diseases / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics*; D009154:Mutation; D009886:Ophthalmoplegia / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D010085:Oxidative Phosphorylation
chemical_list: D024101:Mitochondrial Proteins; D004265:DNA Helicases; C431576:TWNK protein, human