Large-scale RNA interference screening in mammalian cells identifies novel regulators of mutant huntingtin aggregation.
In polyglutamine (polyQ) diseases including Huntington's disease (HD), mutant proteins containing expanded polyQ stretch form aggregates in neurons. Genetic or RNAi screenings in yeast, C. elegans or Drosophila have identified multiple genes modifying polyQ aggregation, a few of which are confirmed effective in mammals. However, the overall molecular mechanism underlying polyQ protein aggregation in mammalian cells still remains obscure. We here perform RNAi screening in mouse neuro2a cells to identify mammalian modifiers for aggregation of mutant huntingtin, a causative protein of HD. By systematic cell transfection and automated cell image analysis, we screen ∼ 12000 shRNA clones and identify 111 shRNAs that either suppress or enhance mutant huntingtin aggregation, without altering its gene expression. Classification of the shRNA-targets suggests that genes with various cellular functions such as gene transcription and protein phosphorylation are involved in modifying the aggregation. Subsequent analysis suggests that, in addition to the aggregation-modifiers sensitive to proteasome inhibition, some of them, such as a transcription factor Tcf20, and kinases Csnk1d and Pik3c2a, are insensitive to it. As for Tcf20, which contains polyQ stretches at N-terminus, its binding to mutant huntingtin aggregates is observed in neuro2a cells and in HD model mouse neurons. Notably, except Pik3c2a, the rest of the modifiers identified here are novel. Thus, our first large-scale RNAi screening in mammalian system identifies previously undescribed genetic players that regulate mutant huntingtin aggregation by several, possibly mammalian-specific mechanisms.
Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan; Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan; Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan; CREST (Core Research for Evolutionary Science and Technology), JST, Tokyo, Japan.
Tomoyuki
T
Yamanaka
Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan; Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Harvard Institutes of Medicine, Boston, Massachusetts, United States of America.
Hon Kit
HK
Wong
Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan.
Asako
A
Tosaki
Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan.
Peter O
PO
Bauer
Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan.
Koji
K
Wada
Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan; Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan; Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan; CREST (Core Research for Evolutionary Science and Technology), JST, Tokyo, Japan.
Masaru
M
Kurosawa
Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan.
Tomomi
T
Shimogori
Department of Neurology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
Nobutaka
N
Hattori
Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan; Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan; Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan; CREST (Core Research for Evolutionary Science and Technology), JST, Tokyo, Japan.
Nobuyuki
N
Nukina
D000818:Animals; D057166:High-Throughput Screening Assays; D000071058:Huntingtin Protein; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D066263:Protein Aggregation, Pathological / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C000594109:Tcf20 protein, mouse; D014157:Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; C546635:Pik3c2a protein, mouse