Mitochondrial loss, dysfunction and altered dynamics in Huntington's disease.
Although a direct causative pathway from the gene mutation to the selective neostriatal neurodegeneration remains unclear in Huntington's disease (HD), one putative pathological mechanism reported to play a prominent role in the pathogenesis of this neurological disorder is mitochondrial dysfunction. We examined mitochondria in preferentially vulnerable striatal calbindin-positive neurons in moderate-to-severe grade HD patients, using antisera against mitochondrial markers of COX2, SOD2 and cytochrome c. Combined calbindin and mitochondrial marker immunofluorescence showed a significant and progressive grade-dependent reduction in the number of mitochondria in spiny striatal neurons, with marked alteration in size. Consistent with mitochondrial loss, there was a reduction in COX2 protein levels using western analysis that corresponded with disease severity. In addition, both mitochondrial transcription factor A, a regulator of mtDNA, and peroxisome proliferator-activated receptor-co-activator gamma-1 alpha, a key transcriptional regulator of energy metabolism and mitochondrial biogenesis, were also significantly reduced with increasing disease severity. Abnormalities in mitochondrial dynamics were observed, showing a significant increase in the fission protein Drp1 and a reduction in the expression of the fusion protein mitofusin 1. Lastly, mitochondrial PCR array profiling in HD caudate nucleus specimens showed increased mRNA expression of proteins involved in mitochondrial localization, membrane translocation and polarization and transport that paralleled mitochondrial derangement. These findings reveal that there are both mitochondrial loss and altered mitochondrial morphogenesis with increased mitochondrial fission and reduced fusion in HD. These findings provide further evidence that mitochondrial dysfunction plays a critical role in the pathogenesis of HD.
Kim
Jinho
J
Geriatric Research Education Clinical Center, New England Veterans Administration VISN 1, Bedford, MA 01730, USA.
Moody
Jennifer P
JP
Edgerly
Christina K
CK
Bordiuk
Olivia L
OL
Cormier
Kerry
K
Smith
Karen
K
Beal
M Flint
MF
Ferrante
Robert J
RJ
D064026:Calbindins; D045304:Cytochromes c / Q000032:analysis / Q000276:immunology; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D034281:Dynamins; D003576:Electron Transport Complex IV / Q000032:analysis; D004734:Energy Metabolism; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D053078:Membrane Potential, Mitochondrial; D026901:Membrane Transport Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism; D017072:Neostriatum / Q000378:metabolism* / Q000648:ultrastructure*; D009419:Nerve Tissue Proteins / Q000235:genetics; D009474:Neurons / Q000737:chemistry / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism; D016133:Polymerase Chain Reaction; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D013482:Superoxide Dismutase / Q000032:analysis / Q000276:immunology; D014157:Transcription Factors / Q000378:metabolism; D000099156:Superoxide Dismutase 2
D064026:Calbindins; D045304:Cytochromes c; D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D034281:Dynamins; D003576:Electron Transport Complex IV; D020558:GTP Phosphohydrolases; D000071058:Huntingtin Protein; D026901:Membrane Transport Proteins; D008869:Microtubule-Associated Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D047492:Peroxisome Proliferator-Activated Receptors; D064030:S100 Calcium Binding Protein G; D013482:Superoxide Dismutase; D014157:Transcription Factors; D000099156:Superoxide Dismutase 2; C086055:HTT protein, human; C422562:mitochondrial transcription factor A; C117108:cytochrome C oxidase subunit II; C470017:Mfn1 protein, human; C110768:DNM1L protein, human