Localization of FMRP-associated mRNA granules and requirement of microtubules for activity-dependent trafficking in hippocampal neurons.
Fragile X syndrome is caused by the absence of the fragile X mental-retardation protein (FMRP), an mRNA-binding protein, which may play important roles in the regulation of dendritic mRNA localization and/or synaptic protein synthesis. We have recently applied high-resolution fluorescence imaging methods to document the presence, motility and activity-dependent regulation of FMRP granule trafficking in dendrites and spines of cultured hippocampal neurons. In this study, we show that FMRP granules distribute to F-actin-rich compartments, including filopodia, spines and growth cones during the staged development of hippocampal neurons in culture. Fragile X mental-retardation protein granules were shown to colocalize with ribosomes, ribosomal RNA and MAP1B mRNA, a known FMRP target, which encodes a protein important for microtubule and actin stabilization. The levels of FMRP within dendrites were reduced by disruption of microtubule dynamics, but not by disruption of F-actin. Direct measurements of FMRP transport kinetics using fluorescence recovery after photobleaching in living neurons showed that microtubules were required to induce the mGluR-dependent translocation into dendrites. This study provides further characterization of the composition and regulated trafficking of FMRP granules in dendrites of hippocampal neurons.
Antar
L N
LN
Department of Neuroscience, Rose F. Kennedy Center for Mental Retardation, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Dictenberg
J B
JB
Plociniak
M
M
Afroz
R
R
Bassell
G J
GJ
D000199:Actins / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D049229:Dendritic Spines / Q000378:metabolism / Q000648:ultrastructure; D036681:Fluorescence Recovery After Photobleaching; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D020439:Growth Cones / Q000378:metabolism / Q000648:ultrastructure; D006624:Hippocampus / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000502:physiology; D011554:Pseudopodia / Q000378:metabolism / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism
D000199:Actins; D051860:Fragile X Messenger Ribonucleoprotein 1; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C497685:Fmr1 protein, rat; C085284:microtubule-associated protein 1B