Human Molecular Genetics Advance Access published online on July 9, 2008
Human Molecular Genetics, doi:10.1093/hmg/ddn198
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A Systematic RNAi Screen Reveals Involvement of Endocytic Pathway in Neuronal Dysfunction in 
-Synuclein Transgenic C. elegans
1 Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan 2 Department of Neuropathology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan 3 Department of Neurology, Hematology, Metabolism, Endocrinology and Diabetology, Faculty of Medicine, Yamagata University, Yamagata, Japan 4 Department of Physiology, School of Medicine, Tokyo Women's Medical University, Tokyo, Japan
* Address Correspondence to Dr. Takeshi Iwatsubo, Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo Bunkyoku Tokyo, 113-0033 Japan Phone: 81-3-5841-4877 Fax: 81-3-5841-4708 Email: iwatsubo{at}mol.f.u-tokyo.ac.jp
Received May 6, 2008; Revised July 8, 2008; Accepted July 8, 2008
Mutations or multiplications in 
-synuclein gene cause familial forms of Parkinson disease or dementia with Lewy bodies, and the deposition of wild-type -synuclein as Lewy bodies occurs as a hallmark lesion of these disorders, collectively referred to as synucleinopathies, implicating -synuclein in the pathogenesis of synucleinopathy. To identify modifier genes of -synuclein-induced neurotoxicity, we conducted an RNAi screen in transgenic C. elegans (Tg worms) that overexpress human -synuclein in a pan-neuronal manner. To enhance the RNAi effect in neurons, we crossed -synuclein Tg worms with an RNAi-enhanced mutant eri-1 strain. We tested RNAi of 1673 genes related to nervous system or synaptic functions, and identified ten genes that, upon knockdown, caused severe growth/motor abnormalities selectively in -synuclein Tg worms. Among these were four genes (i.e., apa-2, aps-2, eps-8 and rab-7) related to the endocytic pathway, including two subunits of AP-2 complex. Consistent with the results by RNAi, crossing -synuclein Tg worms with an aps-2 mutant resulted in severe growth arrest and motor dysfunction.?-Synuclein Tg worms displayed a decreased touch sensitivity upon RNAi of genes involved in synaptic vesicle endocytosis, and they also showed impaired neuromuscular transmission, suggesting that overexpression of -synuclein caused a failure in uptake or recycling of synaptic vesicles. Furthermore, knockdown of apa-2, an AP-2 subunit, caused an accumulation of phosphorylated -synuclein in neuronal cell bodies, mimicking synucleinopathy. Collectively, these findings raise a novel pathogenic link between endocytic pathway and -synuclein-induced neurotoxicity in synucleinopathy.