Format

Send to

Choose Destination
Proc Natl Acad Sci U S A. 2015 Aug 25;112(34):E4697-706. doi: 10.1073/pnas.1502258112. Epub 2015 Aug 11.

Fmr1 deficiency promotes age-dependent alterations in the cortical synaptic proteome.

Author information

1
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;
2
Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China 200031;
3
Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, China 200032;
4
School of Life Sciences, Shanghai University, Shanghai, China 200444;
5
Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA 92037;
6
Department of Molecular and Cellular Neuronscience, The Scripps Research Institute, La Jolla, CA 92037;
7
Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037.
8
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.

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.

KEYWORDS:

autism; fragile X; quantitative mass spectrometry; stable isotope labeling; synaptic protein synthesis

PMID:
26307763
PMCID:
PMC4553823
DOI:
10.1073/pnas.1502258112
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center