title: Live imaging of mitochondrial dynamics in CNS dopaminergic neurons in vivo demonstrates early reversal of mitochondrial transport following MPP(+) exposure.
abstract: Extensive convergent evidence collectively suggests that mitochondrial dysfunction is central to the pathogenesis of Parkinson's disease (PD). Recently, changes in the dynamic properties of mitochondria have been increasingly implicated as a key proximate mechanism underlying neurodegeneration. However, studies have been limited by the lack of a model in which mitochondria can be imaged directly and dynamically in dopaminergic neurons of the intact vertebrate CNS. We generated transgenic zebrafish in which mitochondria of dopaminergic neurons are labeled with a fluorescent reporter, and optimized methods allowing direct intravital imaging of CNS dopaminergic axons and measurement of mitochondrial transport in vivo. The proportion of mitochondria undergoing axonal transport in dopaminergic neurons decreased overall during development between 2days post-fertilization (dpf) and 5dpf, at which point the major period of growth and synaptogenesis of the relevant axonal projections is complete. Exposure to 0.5-1.0mM MPP(+) between 4 and 5dpf did not compromise zebrafish viability or cause detectable changes in the number or morphology of dopaminergic neurons, motor function or monoaminergic neurochemistry. However, 0.5mM MPP(+) caused a 300% increase in retrograde mitochondrial transport and a 30% decrease in anterograde transport. In contrast, exposure to higher concentrations of MPP(+) caused an overall reduction in mitochondrial transport. This is the first time mitochondrial transport has been observed directly in CNS dopaminergic neurons of a living vertebrate and quantified in a PD model in vivo. Our findings are compatible with a model in which damage at presynaptic dopaminergic terminals causes an early compensatory increase in retrograde transport of compromised mitochondria for degradation in the cell body. These data are important because manipulation of early pathogenic mechanisms might be a valid therapeutic approach to PD. The novel transgenic lines and methods we developed will be useful for future studies on mitochondrial dynamics in health and disease.
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: April A
authors.initials: AA
authors.lastname: Dukes
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Bai
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Victor S
authors.initials: VS
authors.lastname: Van Laar
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA; Tsinghua University Medical School, Beijing, China.
authors.forename: Yangzhong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ilin
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA; MSTP program, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: David
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, IN, USA.
authors.forename: Zeynep S
authors.initials: ZS
authors.lastname: Agim
authors.affiliation: Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Bonkowsky
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, IN, USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Cannon
authors.affiliation: Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, USA; Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Simon C
authors.initials: SC
authors.lastname: Watkins
authors.affiliation: Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Claudette M St
authors.initials: CM
authors.lastname: Croix
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA; Geriatric Research, Education and Clinical Center, Pittsburgh Veterans' Affairs Healthcare System, Pittsburgh, PA, USA. Electronic address: eab25@pitt.edu.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Burton
authors.affiliation: Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA. Electronic address: bermans@upmc.edu.
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Berman
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology*; D000818:Animals; D001370:Axonal Transport / Q000187:drug effects* / Q000502:physiology; D001369:Axons / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D002490:Central Nervous System / Q000187:drug effects* / Q000503:physiopathology; D004298:Dopamine / Q000378:metabolism; D059290:Dopaminergic Neurons / Q000187:drug effects* / Q000378:metabolism; D020267:MPTP Poisoning / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D063154:Mitochondrial Dynamics / Q000187:drug effects / Q000502:physiology; D059906:Neuroimaging; D010300:Parkinson Disease / Q000378:metabolism; D015027:Zebrafish
chemical_list: D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine
keywords: Live imaging; MPP(+); Mitochondrial dynamics; Parkinson's disease; Zebrafish