A 3 ' untranslated region variant in FMR1 eliminates neuronal activity-dependent translation of FMRP by disrupting binding of the RNA-binding protein HuR

• Type of Material: Article
• Authors: Joshua A. Suhl, Emory University; Ravi S. Muddashetty, Emory University; Bart R. Anderson, Emory University; Marius Ifrim, Emory University; Jeannie Visootsak, Emory University; Gary Bassell, Emory University; Stephen Warren, Emory University
• Language: English
• Date: 2015-11-24
• Publisher: NATL ACAD SCIENCES
• Publication Version: Final Published Version
• Copyright Statement: PNAS
• Final Published Version (URL): http://dx.doi.org/10.1073/pnas.1514260112
• Title of Journal or Parent Work: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• Volume: 112
• Issue: 47
• Start Page: E6553
• End Page: E6561
• Grant/Funding Information: This work was supported by NIH Award NS091859 from the National Institute of Neurological Disorders and Stroke; Eunice Kennedy Shriver National Institute of Child Health and Human Development in support of the Emory National Fragile X Research Center (S.T.W.); NIH Award 1R21NS091038 (to G.J.B.); and a FRAXA Research Foundation fellowship (to J.A.S.).
• Keywords: WIDE ANALYSIS; X MENTAL-RETARDATION; MOUSE MODEL; TARGET RNA; autism; LONG-TERM DEPRESSION; MISSENSE MUTATION; FMRP; FMR1; Science & Technology; MESSENGER-RNA; SYNAPTIC PLASTICITY; HuR; Multidisciplinary Sciences; FRAGILE; CGG-REPEAT; Science & Technology - Other Topics; fragile X syndrome
• Research Categories: Psychology, Cognitive; Psychology, Clinical; Biology, Neuroscience; Biology, Genetics

Abstract

Fragile X syndrome is a common cause of intellectual disability and autism spectrum disorder. The gene underlying the disorder, fragile X mental retardation 1 (FMR1), is silenced in most cases by a CGGrepeat expansion mutation in the 5? untranslated region (UTR). Recently, we identified a variant located in the 3?UTR of FMR1 enriched among developmentally delayed males with normal repeat lengths. A patient-derived cell line revealed reduced levels of endogenous fragile X mental retardation protein (FMRP), and a reporter containing a patient 3?UTR caused a decrease in expression. A control reporter expressed in cultured mouse cortical neurons showed an expected increase following synaptic stimulation that was absent when expressing the patient reporter, suggesting an impaired response to neuronal activity. Mobility-shift assays using a control RNA detected an RNA-protein interaction that is lost with the patient RNA, and HuR was subsequently identified as an associated protein. Cross-linking immunoprecipitation experiments identified the locus as an in vivo target of HuR, supporting our in vitro findings. These data suggest that the disrupted interaction of HuR impairs activity-dependent translation of FMRP, which may hinder synaptic plasticity in a clinically significant fashion.