Fragile X mental retardation protein levels increase following complex environment exposure in rat brain regions undergoing active synaptogenesis.
Fragile X mental retardation protein (FMRP), which is absent in fragile X syndrome, is synthesized in vitro in response to neurotransmitter activation. Humans and mice lacking FMRP exhibit abnormal dendritic spine development, suggesting that this protein plays an important role in synaptic plasticity. Previously, our laboratory demonstrated increased FMRP immunoreactivity in visual cortex of rats exposed to complex environments (EC) and in motor cortex of rats trained on motor-skill tasks compared with animals reared individually in standard laboratory housing (IC). Here, we use immunohistochemistry to extend those findings by investigating FMRP levels in visual cortex and hippocampal dentate gyrus of animals exposed to EC or IC. Rats exposed to EC for 20 days exhibited increased FMRP immunoreactivity in visual cortex compared with animals housed in standard laboratory caging. In the dentate gyrus, animals exposed to EC for 20 days had higher FMRP levels than animals exposed to EC for 5 or 10 days. In light of possible antibody crossreactivity with closely related proteins FXR1P and FXR2P, FMRP immunoreactivity in the posterior-dorsal one-third of cerebral cortex was also examined by Western blotting following 20 days of EC exposure. FMRP levels were greater in EC animals, whereas levels of FXR1P and FXR2P were unaffected by experience. These results provide further evidence for behaviorally induced alteration of FMRP expression in contrast to its homologues, extend previous findings suggesting regulation of its expression by synaptic activity, and support the theories associating FMRP expression with alteration of synaptic structure both in development and later in the life-cycle.
Irwin
Scott A
SA
Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Christmon
Chariya A
CA
Grossman
Aaron W
AW
Galvez
Roberto
R
Kim
Soong Ho
SH
DeGrush
Brian J
BJ
Weiler
Ivan Jeanne
IJ
Greenough
William T
WT
D000704:Analysis of Variance; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D003337:Corpus Callosum / Q000033:anatomy & histology / Q000378:metabolism; D018891:Dentate Gyrus / Q000033:anatomy & histology / Q000378:metabolism; D004195:Disease Models, Animal; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000378:metabolism; D006799:Housing, Animal; D007150:Immunohistochemistry; D008607:Intellectual Disability / Q000378:metabolism; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D012931:Social Environment; D013569:Synapses / Q000378:metabolism*; D013997:Time Factors; D014793:Visual Cortex / Q000033:anatomy & histology / Q000378:metabolism
D051860:Fragile X Messenger Ribonucleoprotein 1; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; C497685:Fmr1 protein, rat