title: Selective mitochondrial depletion, apoptosis resistance, and increased mitophagy in human Charcot-Marie-Tooth 2A motor neurons.
abstract: Charcot-Marie-Tooth 2A (CMT2A) is an inherited peripheral neuropathy caused by mutations in MFN2, which encodes a mitochondrial membrane protein involved in mitochondrial network homeostasis. Because MFN2 is expressed ubiquitously, the reason for selective motor neuron (MN) involvement in CMT2A is unclear. To address this question, we generated MNs from induced pluripotent stem cells (iPSCs) obtained from the patients with CMT2A as an in vitro disease model. CMT2A iPSC-derived MNs (CMT2A-MNs) exhibited a global reduction in mitochondrial content and altered mitochondrial positioning without significant differences in survival and axon elongation. RNA sequencing profiles and protein studies of key components of the apoptotic executioner program (i.e. p53, BAX, caspase 8, cleaved caspase 3, and the anti-apoptotic marker Bcl2) demonstrated that CMT2A-MNs are more resistant to apoptosis than wild-type MNs. Exploring the balance between mitochondrial biogenesis and the regulation of autophagy-lysosome transcription, we observed an increased autophagic flux in CMT2A-MNs that was associated with increased expression of PINK1, PARK2, BNIP3, and a splice variant of BECN1 that was recently demonstrated to be a trigger for mitochondrial autophagic removal. Taken together, these data suggest that the striking reduction in mitochondria in MNs expressing mutant MFN2 is not the result of impaired biogenesis, but more likely the consequence of enhanced mitophagy. Thus, these pathways represent possible novel molecular therapeutic targets for the development of an effective cure for this disease.
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Federica
authors: F
authors: Rizzo
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Dario
authors: D
authors: Ronchi
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Sabrina
authors: S
authors: Salani
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Monica
authors: M
authors: Nizzardo
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Francesco
authors: F
authors: Fortunato
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Andreina
authors: A
authors: Bordoni
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Giulia
authors: G
authors: Stuppia
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Roberto
authors: R
authors: Del Bo
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Daniela
authors: D
authors: Piga
authors: Department of Pharmacy and Biotecnology (FaBiT), University of Bologna, Bologna, Italy.
authors: Romana
authors: R
authors: Fato
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Nereo
authors: N
authors: Bresolin
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors: Giacomo P
authors: GP
authors: Comi
authors: Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy stefania.corti@unimi.it.
authors: Stefania
authors: S
authors: Corti
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D001343:Autophagy / Q000235:genetics; D000071186:Beclin-1 / Q000235:genetics; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020558:GTP Phosphohydrolases / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000235:genetics*; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology; D011494:Protein Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D000099202:PTEN-Induced Putative Kinase
chemical_list: D000071186:Beclin-1; D020558:GTP Phosphohydrolases; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011494:Protein Kinases; D011518:Proto-Oncogene Proteins; D044767:Ubiquitin-Protein Ligases; D000099202:PTEN-Induced Putative Kinase; C491997:BECN1 protein, human; C090121:BNIP3 protein, human; C111567:parkin protein; C470018:MFN2 protein, human