Neurons depend on a finely tuned transport machinery to keep their cell bodies and extensive processes connected. Increasing evidence suggests that organelle transport is impaired in diseases of motor neurons (MN), where cellular components have to move long distances along axons, and that transport defects may contribute to why MN are specifically affected in amyotrophic lateral sclerosis (ALS). The central hypothesis of this proposal is that impaired mitochondrial dynamics (i.e., transport, fusion, fission) is a primary lesion in ALS MN: when transport is impaired, mitochondria cannot traffic normally to and from crucial sites of energy utilization, such as synaptic terminals, resulting in mitochondrial mislocalization and dysfunction, which in turn causes energy depletion, impaired calcium homeostasis, and ultimately cell degeneration. In this proposal, we will investigate mitochondrial dynamics defects in primary MN from transgenic animal models expressing mutant SOD1, which causes a familial form of ALS. We will use a novel, photo-activatable, fluorescent protein targeted to mitochondria, (mito-Dendra), and live confocal cell imaging. We will investigate the correlations between mitochondrial dynamics defects, mitochondrial structural abnormalities and bioenergetic dysfunction. Our preliminary data strongly suggest that mitochondrial dynamics is abnormal in SOD1 mutant MN and that this abnormality correlates with impaired bioenergetics. First, we will characterize how mutant SOD1 affects mitochondrial transport and determine whether mitochondrial transport defects are specific to MN or if they affect other neural cell types. Furthermore, since ALS involves other cell types besides MN, we will determine whether astrocytes and microglia, which are directly implicated in ALS pathogenesis, play a role in impairing mitochondrial dynamics and function in MN. Second, we will determine how defective mitochondrial dynamics in mutant SOD1 MN affects the interactions with muscle cells at the nuromuscular junction (NMJ), in compartmentalized innervated MN-muscle co-cultures. Third, to verify that mitochondrial dynamics impairment is a primary defect in MN degeneration we will establish the role of mitochondrial transport in maintaining MN and NMJs in normal, wild type, MN, where anterograde mitochondrial transport has been impaired by a genetic approach, independent of mutant SOD1.
Mitochondria are intracellular organelles dedicated to energy metabolism. Mitochondria must be transported along neurons and positioned where energy is needed. Defective mitochondrial transport results in disease. This proposal explores the new field of clinical research using a combination of novel experimental approaches, taking advantage of recently developed fluorescent microscopy techniques. A better understanding of the changes in the dynamics and function of mitochondria in ALS will contribute to identifying avenues of treatment. Furthermore, the system and models that we are developing to study mitochondrial transport defects will be applicable not only to ALS, but also to many other neurodegenerative disorders.
|Palomo, Gloria M; Manfredi, Giovanni (2015) Exploring new pathways of neurodegeneration in ALS: the role of mitochondria quality control. Brain Res 1607:36-46|
|Le Masson, Gwendal; Przedborski, Serge; Abbott, L F (2014) A computational model of motor neuron degeneration. Neuron 83:975-88|
|Kirk, Kathryne; Gennings, Chris; Hupf, Jonathan C et al. (2014) Bioenergetic markers in skin fibroblasts of sporadic amyotrophic lateral sclerosis and progressive lateral sclerosis patients. Ann Neurol 76:620-4|
|Magrane, Jordi; Cortez, Czrina; Gan, Wen-Biao et al. (2014) Abnormal mitochondrial transport and morphology are common pathological denominators in SOD1 and TDP43 ALS mouse models. Hum Mol Genet 23:1413-24|
|Kawamata, Hibiki; Ng, Seng Kah; Diaz, Natalia et al. (2014) Abnormal intracellular calcium signaling and SNARE-dependent exocytosis contributes to SOD1G93A astrocyte-mediated toxicity in amyotrophic lateral sclerosis. J Neurosci 34:2331-48|
|Re, Diane B; Le Verche, Virginia; Yu, Changhao et al. (2014) Necroptosis drives motor neuron death in models of both sporadic and familial ALS. Neuron 81:1001-8|
|Peixoto, Pablo M; Kim, Hyun-Jeong; Sider, Brittany et al. (2013) UCP2 overexpression worsens mitochondrial dysfunction and accelerates disease progression in a mouse model of amyotrophic lateral sclerosis. Mol Cell Neurosci 57:104-10|
|Magrané, Jordi; Sahawneh, Mary Anne; Przedborski, Serge et al. (2012) Mitochondrial dynamics and bioenergetic dysfunction is associated with synaptic alterations in mutant SOD1 motor neurons. J Neurosci 32:229-42|
|Fischer, Lindsey R; Igoudjil, Anissa; Magrane, Jordi et al. (2011) SOD1 targeted to the mitochondrial intermembrane space prevents motor neuropathy in the Sod1 knockout mouse. Brain 134:196-209|
|Igoudjil, Anissa; Magrane, Jordi; Fischer, Lindsey R et al. (2011) In vivo pathogenic role of mutant SOD1 localized in the mitochondrial intermembrane space. J Neurosci 31:15826-37|
Showing the most recent 10 out of 16 publications