Human Molecular Genetics Advance Access originally published online on July 9, 2008
Human Molecular Genetics 2008 17(19):2997-3009; 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 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
* To whom correspondence should be addressed at: Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo Bunkyoku, Tokyo 113-0033, Japan. Tel: +81 358414877; Fax: +81 358414708; Email: iwatsubo{at}mol.f.u-tokyo.ac.jp
Received May 6, 2008; Accepted July 8, 2008
Mutations or multiplications in 
-synuclein gene cause familial forms of Parkinson disease or dementia with Lewy bodies (LB), and the deposition of wild-type -synuclein as LB 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 10 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.