title: Gene-specific mitochondria dysfunctions in human TARDBP and C9ORF72 fibroblasts.
abstract: Dysregulation of RNA metabolism represents an important pathogenetic mechanism in both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) due to the involvement of the DNA/RNA-binding proteins TDP-43 and FUS and, more recently, of C9ORF72. A potential link between dysregulation of RNA metabolism and mitochondrial dysfunction is recently emerged in TDP-43 disease models. To further investigate the possible relationship between these two pathogenetic mechanisms in ALS/FTD, we studied mitochondria functionality in human mutant TARDBP(p.A382T) and C9ORF72 fibroblasts grown in galactose medium to induce a switch from a glycolytic to an oxidative metabolism. In this condition we observed significant changes in mitochondria morphology and ultrastructure in both mutant cells with a fragmented mitochondria network particularly evident in TARDBP(p.A382T) fibroblasts. From analysis of the mitochondrial functionality, a decrease of mitochondria membrane potential with no alterations in oxygen consumption rate emerged in TARDBP fibroblasts. Conversely, an increased oxygen consumption and mitochondria hyperpolarization were observed in C9ORF72 fibroblasts in association to increased ROS and ATP content. We found evidence of autophagy/mitophagy in dynamic equilibrium with the biogenesis of novel mitochondria, particularly in mutant C9ORF72 fibroblasts where an increase of mitochondrial DNA content and mass, and of PGC1-α protein was observed. Our imaging and biochemical data show that wild-type and mutant TDP-43 proteins do not localize at mitochondria so that the molecular mechanisms responsible for such mitochondria impairment remain to be further elucidated. For the first time our findings assess a link between C9ORF72 and mitochondria dysfunction and indicate that mitochondria functionality is affected in TARDBP and C9ORF72 fibroblasts with gene-specific features in oxidative conditions. As in neuronal metabolism mitochondria are actively used for ATP production, we speculate that TARDBP and C9ORF72 mutations might trigger cell death by impairing not only RNA metabolism, but also mitochondria activity in ALS/FTD neurons.
authors.affiliation: Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, Cusano Milanino, 20095, MI, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Onesto
authors.affiliation: Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, Cusano Milanino, 20095, MI, Italy.|Department of Pathophysiology and Transplantation, 'Dino Ferrari' Center - Università degli Studi di Milano, Milan, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Colombrita
authors.affiliation: Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, Cusano Milanino, 20095, MI, Italy.|Department of Pathophysiology and Transplantation, 'Dino Ferrari' Center - Università degli Studi di Milano, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Gumina
authors.affiliation: Laboratory of Immunorheumatology, IRCCS Istituto Auxologico Italiano, Milan, Italy.|Department of Clinical Sciences and Community Health, Università degli Studi di Milano, Milan, Italy.
authors.forename: Maria Orietta
authors.initials: MO
authors.lastname: Borghi
authors.affiliation: Molecular Neurogenetics Unit, Foundation IRCCS-Neurological Institute "Carlo Besta", Milan, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Dusi
authors.affiliation: Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, Cusano Milanino, 20095, MI, Italy.|Department of Pathophysiology and Transplantation, 'Dino Ferrari' Center - Università degli Studi di Milano, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Doretti
authors.affiliation: Neuromuscular and Rare Disease Unit, Department of Neuroscience, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy.
authors.forename: Gigliola
authors.initials: G
authors.lastname: Fagiolari
authors.affiliation: Molecular Neurogenetics Unit, Foundation IRCCS-Neurological Institute "Carlo Besta", Milan, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Invernizzi
authors.affiliation: Neuromuscular and Rare Disease Unit, Department of Neuroscience, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Moggio
authors.affiliation: Molecular Neurogenetics Unit, Foundation IRCCS-Neurological Institute "Carlo Besta", Milan, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Tiranti
authors.affiliation: Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, Cusano Milanino, 20095, MI, Italy.|Department of Pathophysiology and Transplantation, 'Dino Ferrari' Center - Università degli Studi di Milano, Milan, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Silani
authors.affiliation: Department of Neurology and Laboratory of Neuroscience, IRCCS Istituto Auxologico Italiano, Via Zucchi, 18, Cusano Milanino, 20095, MI, Italy. antonia.ratti@unimi.it.|Department of Pathophysiology and Transplantation, 'Dino Ferrari' Center - Università degli Studi di Milano, Milan, Italy. antonia.ratti@unimi.it.
authors.forename: Antonia
authors.initials: A
authors.lastname: Ratti
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017209:Apoptosis / Q000502:physiology; D000073885:C9orf72 Protein; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure; D057174:Frontotemporal Lobar Degeneration / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure*; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D004268:DNA-Binding Proteins; D011506:Proteins; D017382:Reactive Oxygen Species; C000598624:TARDBP protein, human; D000255:Adenosine Triphosphate; D010100:Oxygen
keywords: ALS; C9ORF72; FTD; Fibroblast; Mitochondria dysfunction; TDP-43