C9orf72 poly GA RAN-translated protein plays a key role in amyotrophic lateral sclerosis via aggregation and toxicity
Authors: Boris Rogelj
Alan Stepto
Christopher E Shaw
Jorge Gomez-Deza
Leonard Petrucelli
Sarah Guthrie
Han-Jou Chen
Jean-Marc Gallo
Frank Hirth
Pranetha Baskaran
Claire Troakes
Agnes L Nishimura
Youn-Bok Lee
Yoshitsugu Adachi
Bradley N Smith
Journal: Human Molecular Genetics (2017)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: GGGGCC; C9orf72; ALS; FTD; RAN translation
Affiliations: United Kingdom Dementia Research Institute Centre, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, Camberwell, London SE5 9NU, UK, Department of Developmental Neurobiology, King’s College London, Guy’s Campus, London SE1 1UL, UK, Department of Neuroscience, Mayo Clinic Florida, Jacksonville, FL 32224, USA, Department of Biotechnology, Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia, School of Life Sciences, University of Sussex, JMS Building, Falmer Campus, Brighton, BN7 9QG UK

Abstract:  An intronic GGGGCC (G4C2) hexanucleotide repeat expansion inC9orf72 is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD). Repeat-associated non-AUG (RAN) translation of G4C2 RNA can result in five different dipeptide repeat proteins (DPR: poly GA, poly GP, poly GR, poly PA, and poly PR), which aggregate into neuronal cytoplasmic and nuclear inclusions in affected patients, however their contribution to disease pathogenesis remains controversial. We show that among the DPR proteins, expression of poly GA in a cell culture model activates programmed cell death and TDP-43 cleavage in a dose-dependent manner. Dual expression of poly GA together with other DPRs revealed that poly GP and poly PA are sequestered by poly GA, whereas poly GR and poly PR are rarely co-localised with poly GA. Dual expression of poly GA and poly PA ameliorated poly GA toxicity by inhibiting poly GA aggregation both in vitro and in vivo in the chick embryonic spinal cord. Expression of alternative codon-derived DPRs in chick embryonic spinal cord confirmed in vitro data, revealing that each of the dipeptides caused toxicity, with poly GA being the most toxic. Further, in vivo expression of G4C2 repeats of varying length caused apoptotic cell death, but failed to generate DPRs. Together, these data demonstrate that C9-related toxicity can be mediated by either RNA or DPRs. Moreover, our findings provide evidence that poly GA is a key mediator of cytotoxicity and that cross-talk between DPR proteins likely modifies their pathogenic status in C9ALS/FTD. 

Retracted: No

PubPeer comments:
 Figure 6A. https: imgur.com 43q3gWK , 
 2021 correction. https: academic.oup.com hmg article 30 3-4 318 5901521 This is a correction to: Human Molecular Genetics, Volume 26, Issue 24, 15 December 2017, Pages 4765u20134777, https: doi.org 10.1093 hmg ddx350 Since this article was originally published, the authors discovered errors in Figures 3H and 6A. In Figure 3H the last lane GAPDH was excluded, while in Figure 6A, the western-blot shows 6 lanes for PARP and TDP-43 but 7 lanes have been included for GAPDH. The correct figures are included here. ,