title: Fmr1 deficiency promotes age-dependent alterations in the cortical synaptic proteome.
abstract: Fragile X syndrome (FXS) is an X-linked neurodevelopmental disorder characterized by severe intellectual disability and other symptoms including autism. Although caused by the silencing of a single gene, Fmr1 (fragile X mental retardation 1), the complexity of FXS pathogenesis is amplified because the encoded protein, FMRP, regulates the activity-dependent translation of numerous mRNAs. Although the mRNAs that associate with FMRP have been extensively studied, little is known regarding the proteins whose expression levels are altered, directly or indirectly, by loss of FMRP during brain development. Here we systematically measured protein expression in neocortical synaptic fractions from Fmr1 knockout (KO) and wild-type (WT) mice at both adolescent and adult stages. Although hundreds of proteins are up-regulated in the absence of FMRP in young mice, this up-regulation is largely diminished in adulthood. Up-regulated proteins included previously unidentified as well as known targets involved in synapse formation and function and brain development and others linked to intellectual disability and autism. Comparison with putative FMRP target mRNAs and autism susceptibility genes revealed substantial overlap, consistent with the idea that the autism endophenotype of FXS is due to a "multiple hit" effect of FMRP loss, particularly within the PSD95 interactome. Through studies of de novo protein synthesis in primary cortical neurons from KO and WT mice, we found that neurons lacking FMRP produce nascent proteins at higher rates, many of which are synaptic proteins and encoded by FMRP target mRNAs. Our results provide a greatly expanded view of protein changes in FXS and identify age-dependent effects of FMRP in shaping the neuronal proteome.
authors: Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, School of Life Sciences, East China Normal University, Shanghai, China 200241; Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, China 200241;
authors: Bin
authors: B
authors: Tang
authors: Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, School of Life Sciences, East China Normal University, Shanghai, China 200241; Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, China 200241;
authors: Tingting
authors: T
authors: Wang
authors: Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, School of Life Sciences, East China Normal University, Shanghai, China 200241; Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, China 200241;
authors: Huida
authors: H
authors: Wan
authors: Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China 200031;
authors: Li
authors: L
authors: Han
authors: Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, School of Life Sciences, East China Normal University, Shanghai, China 200241; Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, China 200241;
authors: Xiaoyan
authors: X
authors: Qin
authors: Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China 200032;
authors: Yaoyang
authors: Y
authors: Zhang
authors: School of Life Sciences, Shanghai University, Shanghai, China 200444;
authors: Jian
authors: J
authors: Wang
authors: Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, School of Life Sciences, East China Normal University, Shanghai, China 200241; Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, China 200241;
authors: Chunlei
authors: C
authors: Yu
authors: Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA 92037;
authors: Fulvia
authors: F
authors: Berton
authors: Department of Molecular and Cellular Neuronscience, The Scripps Research Institute, La Jolla, CA 92037;
authors: Walter
authors: W
authors: Francesconi
authors: Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA 92037;
authors: John R
authors: JR
authors: Yates
authors: Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037.
authors: Peter W
authors: PW
authors: Vanderklish
authors: Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, School of Life Sciences, East China Normal University, Shanghai, China 200241; Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, China 200241; ljliao@bio.ecnu.edu.cn.
authors: Lujian
authors: L
authors: Liao
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D001321:Autistic Disorder / Q000235:genetics; D002540:Cerebral Cortex / Q000378:metabolism*; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D020543:Proteome; D013569:Synapses / Q000378:metabolism*
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; D009419:Nerve Tissue Proteins; D020543:Proteome; C497684:Fmr1 protein, mouse
keywords: autism; fragile X; quantitative mass spectrometry; stable isotope labeling; synaptic protein synthesis