Dataset Information

Role of mental retardation-associated dystrophin-gene product Dp71 in excitatory synapse organization, synaptic plasticity and behavioral functions.

ABSTRACT:

Background

Duchenne muscular dystrophy (DMD) is caused by deficient expression of the cytoskeletal protein, dystrophin. One third of DMD patients also have mental retardation (MR), likely due to mutations preventing expression of dystrophin and other brain products of the DMD gene expressed from distinct internal promoters. Loss of Dp71, the major DMD-gene product in brain, is thought to contribute to the severity of MR; however, the specific function of Dp71 is poorly understood.

Methodology/principal findings

Complementary approaches were used to explore the role of Dp71 in neuronal function and identify mechanisms by which Dp71 loss may impair neuronal and cognitive functions. Besides the normal expression of Dp71 in a subpopulation of astrocytes, we found that a pool of Dp71 colocalizes with synaptic proteins in cultured neurons and is expressed in synaptic subcellular fractions in adult brains. We report that Dp71-associated protein complexes interact with specialized modular scaffolds of proteins that cluster glutamate receptors and organize signaling in postsynaptic densities. We then undertook the first functional examination of the brain and cognitive alterations in the Dp71-null mice. We found that these mice display abnormal synapse organization and maturation in vitro, altered synapse density in the adult brain, enhanced glutamatergic transmission and reduced synaptic plasticity in CA1 hippocampus. Dp71-null mice show selective behavioral disturbances characterized by reduced exploratory and novelty-seeking behavior, mild retention deficits in inhibitory avoidance, and impairments in spatial learning and memory.

Conclusions/significance

Results suggest that Dp71 expression in neurons play a regulatory role in glutamatergic synapse organization and function, which provides a new mechanism by which inactivation of Dp71 in association with that of other DMD-gene products may lead to increased severity of MR.

SUBMITTER: Daoud F

PROVIDER: S-EPMC2718704 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Publications

Role of mental retardation-associated dystrophin-gene product Dp71 in excitatory synapse organization, synaptic plasticity and behavioral functions.

Daoud Fatma F Candelario-Martínez Aurora A Billard Jean-Marie JM Avital Avi A Khelfaoui Malik M Rozenvald Yael Y Guegan Maryvonne M Mornet Dominique D Jaillard Danielle D Nudel Uri U Chelly Jamel J Martínez-Rojas Dalila D Laroche Serge S Yaffe David D Vaillend Cyrille C

PloS one 20080810 8

<h4>Background</h4>Duchenne muscular dystrophy (DMD) is caused by deficient expression of the cytoskeletal protein, dystrophin. One third of DMD patients also have mental retardation (MR), likely due to mutations preventing expression of dystrophin and other brain products of the DMD gene expressed from distinct internal promoters. Loss of Dp71, the major DMD-gene product in brain, is thought to contribute to the severity of MR; however, the specific function of Dp71 is poorly understood.<h4>Met ...[more]

PMID: 19649270

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Project description:Repeated exposure to cocaine causes sensitized behavioral responses and increased dendritic spines on medium spiny neurons of the nucleus accumbens (NAc). We find that cocaine regulates myocyte enhancer factor 2 (MEF2) transcription factors to control these two processes in vivo. Cocaine suppresses striatal MEF2 activity in part through a novel mechanism involving cAMP, the regulator of calmodulin signaling (RCS), and calcineurin. We show that reducing MEF2 activity in the NAc in vivo is required for the cocaine-induced increases in dendritic spine density. Surprisingly, we find that increasing MEF2 activity in the NAc, which blocks the cocaine-induced increase in dendritic spine density, enhances sensitized behavioral responses to cocaine. Together, our findings implicate MEF2 as a key regulator of structural synapse plasticity and sensitized responses to cocaine, and suggest that reducing MEF2 activity (and increasing spine density) in NAc may be a compensatory mechanism to limit long-lasting maladaptive behavioral responses to cocaine. Mice were treated for 7 days with daily injections of cocaine (20 mg/kg) and sacrificed 24 hrs later. Chromatin from bilateral punches of NAc was immunoprecipitated with an antibody against MEF2A as described previously with minor modifications (Renthal et al., 2007). Chromatin was sonicated to an average of ~500 bp and immunoprepitated with antibody against MEF2A (Santa Cruz, sc-313) or an IgG control (Upstate/Millipore). Antibody-bound chromatin was precipitated using Protein A beads from Upstate (06-157), which were washed with low salt, high salt, and LiCl buffers to remove non-specific DNA binding. Eluted chromatin was reverse-crosslinked at 65oC in the presence of proteinase K and EDTA. DNA was purified by chloroform extraction/ethanol precipitation and the enrichment of specific promoters was amplified by ligation-mediated PCR for genome-wide analysis (Sikder et al., 2006). Amplified DNA was then labeled with Cy3 (input-enriched) or Cy5 (MEF2-enriched) and hybridized to Nimblegen (Madison, WI) MM8 mouse promoter arrays. Bilateral nucleus accumbens from eight mice were pooled for microarray analysis.

Dataset Information

Role of mental retardation-associated dystrophin-gene product Dp71 in excitatory synapse organization, synaptic plasticity and behavioral functions.

Background

Methodology/principal findings

Conclusions/significance

Publications

Role of mental retardation-associated dystrophin-gene product Dp71 in excitatory synapse organization, synaptic plasticity and behavioral functions.

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