Journal Article

G‐quadruplex‐binding small molecules ameliorate C9orf72 FTD/ALS pathology in vitro and in vivo

Farahat, Abdelbasset A, Gilbert‐Jaramillo, Javier, Clayton, Emma L, Wilson, Katherine M, Wray, Selina, Neidle, Stephen, Patani, Rickie, Clarke, Mica, Stephens, Chad E, Fratta, Pietro, Partridge, Linda, Balendra, Rubika, Nicoll, Andrew J, Zetterberg, Henrik, Woodling, Nathan S, Niccoli, Teresa, Heslegrave, Amanda, Calvo, Andrea, Vo, Tam, Parkinson, Gary, Isaacs, Adrian M, Abdelkarim, Samir, Ismail, Mohamed A, Konrad, Marie‐Therese, Houlden, Henry, Preza, Elisavet, Simone, Roberto, Polke, James M, Moens, Thomas G, Mitchell, Jamie S, Chio, Adriano, Wilson, W David, Boykin, David W

2018

Overview

Intronic GGGGCC repeat expansions in C9orf72 are the most common known cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), which are characterised by degeneration of cortical and motor neurons, respectively. Repeat expansions have been proposed to cause disease by both the repeat RNA forming foci that sequester RNA‐binding proteins and through toxic dipeptide repeat proteins generated by repeat‐associated non‐ATG translation. GGGGCC repeat RNA folds into a G‐quadruplex secondary structure, and we investigated whether targeting this structure is a potential therapeutic strategy. We performed a screen that identified three structurally related small molecules that specifically stabilise GGGGCC repeat G‐quadruplex RNA. We investigated their effect in C9orf72 patient iPSC‐derived motor and cortical neurons and show that they significantly reduce RNA foci burden and the levels of dipeptide repeat proteins. Furthermore, they also reduce dipeptide repeat proteins and improve survival in vivo , in GGGGCC repeat‐expressing Drosophila . Therefore, small molecules that target GGGGCC repeat G‐quadruplexes can ameliorate the two key pathologies associated with C9orf72 FTD/ALS. These data provide proof of principle that targeting GGGGCC repeat G‐quadruplexes has therapeutic potential. Synopsis Small molecules targeting G‐quadruplex GGGGCC repeat RNA are effective at ameliorating disease phenotypes in C9orf72 patient neurons, and in vivo phenotypes in C9orf72 flies. Therefore, targeting expanded GGGGCC RNA could be an effective therapeutic strategy for C9orf72 ALS and FTD. FRET based screen identifies small molecules that specifically bind to C9orf72 repeat RNA G‐quadruplexes. Small molecules reduce RNA foci and dipeptide repeat proteins (DPRs) in C9orf72 patient neurons. G‐quadruplex GGGGCC binding small molecule improves survival and reduces levels of the toxic DPR poly‐GR in C9orf72 flies. Provides proof of principle for targeting GGGGCC RNA G‐quadruplexes in C9orf72 FTD/ALS. Graphical Abstract Small molecules targeting G‐quadruplex GGGGCC repeat RNA are effective at ameliorating disease phenotypes in C9orf72 patient neurons, and in vivo phenotypes in C9orf72 flies. Therefore, targeting expanded GGGGCC RNA could be an effective therapeutic strategy for C9orf72 ALS and FTD.

• Publisher: Nature Publishing Group UK,EMBO Press,John Wiley and Sons Inc,Springer Nature
• Subject: Amyotrophic lateral sclerosis / Amyotrophic Lateral Sclerosis - drug therapy / Amyotrophic Lateral Sclerosis - genetics / Animals / C9orf72 / C9orf72 Protein - genetics / Degeneration / Dementia disorders / Drosophila / Drug Discovery / EMBO27 / EMBO28 / Fluorescence resonance energy transfer / Frontotemporal dementia / Frontotemporal Dementia - drug therapy / Frontotemporal Dementia - genetics / G-Quadruplexes - drug effects / G‐quadruplex / Humans / Motor neurons / Protein structure / Proteins / Repetitive Sequences, Nucleic Acid - drug effects / Ribonucleic acid / RNA / RNA - chemistry / RNA - genetics / RNA-binding protein / Secondary structure / Small Molecule Libraries - chemistry / Small Molecule Libraries - pharmacology / Small Molecule Libraries - therapeutic use