A native function for RAN translation and CGG repeats in regulating fragile X protein synthesis

• Type of Material: Article
• Authors: Caitlin M. Rodriguez, University of Michigan; Shannon E. Wright, University of Michigan; Michael G. Kearse, University of Michigan; Jill M. Haenfler, University of Michigan; Brittany N. Flores, University of Michigan; Yu Liu, University of Michigan; Marius Ifrim, Emory University; Mary R. Glineburg, University of Michigan; Amy Krans, University of Michigan; Paymaan Jafar-Nejad, Ionis Pharmaceuticals; Michael A. Sutton, University of Michigan; Gary Bassell, Emory University; Jack M. Parent, University of Michigan; Frank Rigo, Ionis Pharmaceuticals; Sami J. Barmada, University of Michigan; Peter K. Todd, University of Michigan
• Language: English
• Date: 2020-02-17
• Publisher: NATURE PUBLISHING GROUP
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research
• License: Creative Commons Attribution-NonCommercial 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1038/s41593-020-0590-1
• Title of Journal or Parent Work: NATURE NEUROSCIENCE
• Volume: 23
• Issue: 3
• Start Page: 386
• End Page: +
• Grant/Funding Information: This work was funded by NIH (R01NS099280 and R01NS086810), and philanthropic donations to P.K.T. C.M.R was supported by NINDS F31 NS090883-03. M.G.K was supported by F32NS089124 and is now supported by K99GM126064. J.M.H. was funded by T32NS007222 and a post-doctoral fellowship from FRAXA. S.J.B. and B.N.F. were supported by the NIH (R01-NS097542, 1P30AG053760). S.E.W. was supported by NIH T-32-NS076401. M.I. and G.B. were supported by NINDS 5P30NS05507708. M.R.G. was supported by NIH T32NS007222. M.A.S. was supported by the Michigan Discovery Fund. F.R. and P.J.-N. were supported by Ionis Pharmaceuticals, who also funded reagent generation. IPSC work was supported by the University of Michigan Human Stem Cell and Genome Editing Core.
• Keywords: FMRP; TREMOR/ATAXIA SYNDROME; DIFFERENTIATION; Neurosciences & Neurology; Science & Technology; IN-VIVO; SMALL-MOLECULE; MOUSE MODEL; STEM-CELLS; MENTAL-RETARDATION PROTEIN; SYNAPTIC FUNCTION; Life Sciences & Biomedicine; Neurosciences; MESSENGER-RNAS
• Research Categories: Psychology, Cognitive; Biology, Cell; Biology, Neuroscience

Abstract

Repeat-associated non-AUG-initiated translation of expanded CGG repeats (CGG RAN) from the FMR1 5′-leader produces toxic proteins that contribute to neurodegeneration in fragile X-associated tremor/ataxia syndrome. Here we describe how unexpanded CGG repeats and their translation play conserved roles in regulating fragile X protein (FMRP) synthesis. In neurons, CGG RAN acts as an inhibitory upstream open reading frame to suppress basal FMRP production. Activation of mGluR5 receptors enhances FMRP synthesis. This enhancement requires both the CGG repeat and CGG RAN initiation sites. Using non-cleaving antisense oligonucleotides (ASOs), we selectively blocked CGG RAN. This ASO blockade enhanced endogenous FMRP expression in human neurons. In human and rodent neurons, CGG RAN-blocking ASOs suppressed repeat toxicity and prolonged survival. These findings delineate a native function for CGG repeats and RAN translation in regulating basal and activity-dependent FMRP synthesis, and they demonstrate the therapeutic potential of modulating CGG RAN translation in fragile X-associated disorders.