The Fragile X Mental Retardation Protein (FMRP) is hypothesized to be involved in the regulation of mRNA transport and/or translation at synapses. Synaptic dysfunction in fragile x syndrome is believed to result from dysregulation of mRNA in dendrites. However, despite the previous identification of many mRNAs that are bound by FMRP in vitro, it was unknown whether any of the interactions between FMRP and these mRNAs occur in dendrites and at synapses. In the previous funding period, we proposed to test the hypothesis that FMRP is required for the glutamatergic regulation of mRNA transport in dendrites and its translation at synapses. Importantly, we demonstrated distinct roles for FMRP in both the regulation of mRNA transport in dendrites and translation at synapses. An inherent difficulty in studying FMRP function in dendrites was the lack of suitable high-resolution microscopic technology to visualize and quantify mRNA transport and local translation. We have made substantial progress in the refinement of FISH methodology, which led to the discovery that several FMRP associated mRNAs are localized to dendrites in vitro and in vivo. The phosphorylation status of FMRP was shown to provide a means to regulate translation downstream of gp1- mGluR activation. This renewal application will test the hypothesis that FMRP trafficking, posttranslational modification and association with specific miRNAs are involved in the mechanism and regulation of mRNA transport and local protein synthesis.
Aim 1 will investigate whether phosphorylation and/or degradation of FMRP is regulated by gp1 mGluRs to influence FMRP dynamics and mRNA trafficking.
Aim 2 will characterize the molecular mechanism of FMRP-mediated translational regulation in dendrites. We will assess the role of FMRP phosphorylation in miRNA-mediated translational regulation. Lastly, we will further investigate the hypothesis that FMRP directly regulates the local synthesis of proteins involved in neuronal signaling pathways downstream of gp1-mGluR activation.
Aim 3 will focus on the role of FMRP in PI3K mediated signal transduction and regulation of protein synthesis. This research will provide new insight into mechanisms of protein synthesis-dependent synaptic plasticity underlying learning and memory, and may lead to the development of new therapeutic strategies for fragile x and other forms of mental illness.

Public Health Relevance

Fragile X syndrome is the most common form of inherited mental retardation. This project will elucidate a novel function for the fragile x mental retardation protein, FMRP, in the regulation of dendritic protein synthesis through miRNAs, which are important regulators of gene expression in the nervous system. This research is expected to provide new insight into mechanisms of synaptic plasticity underlying learning and memory, and may lead to the development of new therapeutic strategies for fragile x and other forms of mental illness.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Research Project (R01)
Project #
5R01MH085617-08
Application #
8197532
Study Section
Special Emphasis Panel (ZRG1-MDCN-D (02))
Program Officer
Beckel-Mitchener, Andrea C
Project Start
2004-12-15
Project End
2013-11-30
Budget Start
2011-12-01
Budget End
2012-11-30
Support Year
8
Fiscal Year
2012
Total Cost
$383,625
Indirect Cost
$136,125
Name
Emory University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
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Suhl, Joshua A; Chopra, Pankaj; Anderson, Bart R et al. (2014) Analysis of FMRP mRNA target datasets reveals highly associated mRNAs mediated by G-quadruplex structures formed via clustered WGGA sequences. Hum Mol Genet 23:5479-91
Xing, Lei; Bassell, Gary J (2013) mRNA localization: an orchestration of assembly, traffic and synthesis. Traffic 14:2-14
Swanger, Sharon A; He, Yuncen A; Richter, Joel D et al. (2013) Dendritic GluN2A synthesis mediates activity-induced NMDA receptor insertion. J Neurosci 33:8898-908
Jakkamsetti, Vikram; Tsai, Nien-Pei; Gross, Christina et al. (2013) Experience-induced Arc/Arg3.1 primes CA1 pyramidal neurons for metabotropic glutamate receptor-dependent long-term synaptic depression. Neuron 80:72-9
Gross, Christina; Berry-Kravis, Elizabeth M; Bassell, Gary J (2012) Therapeutic strategies in fragile X syndrome: dysregulated mGluR signaling and beyond. Neuropsychopharmacology 37:178-95
Gross, Christina; Bassell, Gary J (2012) Excess protein synthesis in FXS patient lymphoblastoid cells can be rescued with a p110ýý-selective inhibitor. Mol Med 18:336-45
Muddashetty, Ravi S; Nalavadi, Vijayalaxmi C; Gross, Christina et al. (2011) Reversible inhibition of PSD-95 mRNA translation by miR-125a, FMRP phosphorylation, and mGluR signaling. Mol Cell 42:673-88
Gross, Christina; Yao, Xiaodi; Pong, Dan L et al. (2011) Fragile X mental retardation protein regulates protein expression and mRNA translation of the potassium channel Kv4.2. J Neurosci 31:5693-8
Swanger, Sharon A; Bassell, Gary J; Gross, Christina (2011) High-resolution fluorescence in situ hybridization to detect mRNAs in neuronal compartments in vitro and in vivo. Methods Mol Biol 714:103-23

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