Chronic Pharmacological mGlu5 Inhibition Corrects Fragile X in Adult Mice

Michalon, Aubin; Sidorov, Michael S.; Ballard, Theresa M.; Ozmen, Laurence; Spooren, Will; Wettstein, Joseph G.; Jaeschke, Georg; Bear, Mark F.; Lindemann, Lothar

doi:10.1016/j.neuron.2012.03.009

Cited by 440 publications

(450 citation statements)

References 36 publications

Supporting

Mentioning

432

Contrasting

Unclassified

Order By: Relevance

“…The role of group I mGluRs in LFU-induced large spine shrinkage raised an exciting question about the extent of mGluR signaling activity in different sizes of spines. To examine mGluR activity in individual spines, we used an electrophysiological readout of group I mGluR activation (26): reduced amplitude of AMPA receptor (AMPAR)-uEPSCs after DHPG application (Fig. 4D).…”

Section: D-f)mentioning

confidence: 99%

Synapse-specific and size-dependent mechanisms of spine structural plasticity accompanying synaptic weakening

Hill

Zito

2012

Proc. Natl. Acad. Sci. U.S.A.

141

142

View full text Add to dashboard Cite

Refinement of neural circuits in the mammalian cerebral cortex shapes brain function during development and in the adult. However, the signaling mechanisms underlying the synapse-specific shrinkage and loss of spiny synapses when neural circuits are remodeled remain poorly defined. Here, we show that low-frequency glutamatergic activity at individual dendritic spines leads to synapse-specific synaptic weakening and spine shrinkage on CA1 neurons in the hippocampus. We found that shrinkage of individual spines in response to lowfrequency glutamate uncaging is saturable, reversible, and requires NMDA receptor activation. Notably, shrinkage of large spines additionally requires signaling through metabotropic glutamate receptors (mGluRs) and inositol 1,4,5-trisphosphate receptors (IP 3 Rs), supported by higher levels of mGluR signaling activity in large spines. Our results support a model in which signaling through both NMDA receptors and mGluRs is required to drive activity-dependent synaptic weakening and spine shrinkage at large, mature dendritic spines when neural circuits undergo experience-dependent modification.two-photon microscopy | long-term depression | synaptic plasticity | spine dynamics S tructural plasticity of neurons, such as the growth and retraction of dendritic spines, is thought to contribute to the experience-dependent changes in brain circuitry that mediate learning and memory (1, 2). In particular, the destabilization and loss of spiny synapses plays a critical role in the refinement of neural circuits during development and during learning. Indeed, spine elimination occurs more frequently than does spine formation in young rodents between the first and the third month of age (3-5), a period when experience-dependent refinement of neural circuitry is in its peak. Furthermore, several in vivo studies demonstrate that manipulations leading to experience-dependent circuit plasticity also increase the rate of spine shrinkage and loss (6-9). However, it remains unclear how neural activity drives the selective shrinkage and loss of individual dendritic spines in response to sensory experience.Dendritic spines occur in a wide variety of shapes and sizes (10, 11), and their stability is strongly correlated with spine size (3, 12, 13). Small spines are in general more motile and thought to serve as substrates for plasticity, or "learning" spines; large spines are more stable and thought to serve as components of functioning neural circuits, or "memory" spines (12,14). It is the selective shrinkage and loss of individual circuit-incorporated, persistent spines that underlies experience-dependent circuit refinement (6, 9, 15). Thus, experience-dependent circuit remodeling requires an activity-dependent mechanism that selectively induces shrinkage and retraction of those specific individual dendritic spines that are no longer useful for circuit function.Previous studies have established that low-frequency glutamatergic stimulation (LFS), which causes long-term depression (LTD) of synaptic transmission in...

show abstract

Section: D-f)mentioning

confidence: 99%

Synapse-specific and size-dependent mechanisms of spine structural plasticity accompanying synaptic weakening

Hill

Zito

2012

Proc. Natl. Acad. Sci. U.S.A.

141

142

View full text Add to dashboard Cite

show abstract

“…Treatment by CTEP was performed as described previously (Lindemann et al, 2011;Michalon et al, 2012). CTEP was formulated as a microsuspension in vehicle (0.9% NaCl, 0.3% Tween-80).…”

Section: Drug Treatmentmentioning

confidence: 99%

Homer1/mGluR5 Activity Moderates Vulnerability to Chronic Social Stress

Wagner

Hartmann

Labermaier

et al. 2014

Neuropsychopharmacol

Self Cite

View full text Add to dashboard Cite

Stress-induced psychiatric disorders, such as depression, have recently been linked to changes in glutamate transmission in the central nervous system. Glutamate signaling is mediated by a range of receptors, including metabotropic glutamate receptors (mGluRs). In particular, mGluR subtype 5 (mGluR5) is highly implicated in stress-induced psychopathology. The major scaffold protein Homer1 critically interacts with mGluR5 and has also been linked to several psychopathologies. Yet, the specific role of Homer1 in this context remains poorly understood. We used chronic social defeat stress as an established animal model of depression and investigated changes in transcription of Homer1a and Homer1b/c isoforms and functional coupling of Homer1 to mGluR5. Next, we investigated the consequences of Homer1 deletion, overexpression of Homer1a, and chronic administration of the mGluR5 inverse agonist CTEP (2-chloro-4-((2,5-dimethyl-1-(4-(trifluoromethoxy)phenyl)-1H-imidazol-4-yl)ethynyl)pyridine) on the effects of chronic stress. In mice exposed to chronic stress, Homer1b/c, but not Homer1a, mRNA was upregulated and, accordingly, Homer1/mGluR5 coupling was disrupted. We found a marked hyperactivity behavior as well as a dysregulated hypothalamic-pituitary-adrenal axis activity in chronically stressed Homer1 knockout (KO) mice. Chronic administration of the selective and orally bioavailable mGluR5 inverse agonist, CTEP, was able to recover behavioral alterations induced by chronic stress, whereas overexpression of Homer1a in the hippocampus led to an increased vulnerability to chronic stress, reflected in an increased physiological response to stress as well as enhanced depression-like behavior. Overall, our results implicate the glutamatergic system in the emergence of stress-induced psychiatric disorders, and support the Homer1/mGluR5 complex as a target for the development of novel antidepressant agents.

show abstract

“…The FMR1 knockout (KO) mouse (Fmr1 −/y ) replicates phenotypes similar to human symptoms-including autistic-like behaviors, cognitive deficits, and hyperactivity-as well as abnormal dendritic spine morphology (3). FMR1 encodes Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein associated to polyribosomes and involved in the translational control of mRNAs important for synaptic plasticity (4).…”

mentioning

confidence: 99%

Fragile X Mental Retardation Protein (FMRP) controls diacylglycerol kinase activity in neurons

Tabet

Moutin

Becker

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

102

View full text Add to dashboard Cite

Fragile X syndrome (FXS) is caused by the absence of the Fragile X Mental Retardation Protein (FMRP) in neurons. In the mouse, the lack of FMRP is associated with an excessive translation of hundreds of neuronal proteins, notably including postsynaptic proteins. This local protein synthesis deregulation is proposed to underlie the observed defects of glutamatergic synapse maturation and function and to affect preferentially the hundreds of mRNA species that were reported to bind to FMRP. How FMRP impacts synaptic protein translation and which mRNAs are most important for the pathology remain unclear. Here we show by cross-linking immunoprecipitation in cortical neurons that FMRP is mostly associated with one unique mRNA: diacylglycerol kinase kappa (Dgkκ), a master regulator that controls the switch between diacylglycerol and phosphatidic acid signaling pathways. The absence of FMRP in neurons abolishes group 1 metabotropic glutamate receptor-dependent DGK activity combined with a loss of Dgkκ expression. The reduction of Dgkκ in neurons is sufficient to cause dendritic spine abnormalities, synaptic plasticity alterations, and behavior disorders similar to those observed in the FXS mouse model. Overexpression of Dgkκ in neurons is able to rescue the dendritic spine defects of the Fragile X Mental Retardation 1 gene KO neurons. Together, these data suggest that Dgkκ deregulation contributes to FXS pathology and support a model where FMRP, by controlling the translation of Dgkκ, indirectly controls synaptic proteins translation and membrane properties by impacting lipid signaling in dendritic spine.F ragile X syndrome (FXS), the most common cause of inherited intellectual disability and autism, is due to the transcriptional inactivation of the Fragile X Mental Retardation 1 gene (FMR1) (1, 2). The FMR1 knockout (KO) mouse (Fmr1 −/y ) replicates phenotypes similar to human symptoms-including autistic-like behaviors, cognitive deficits, and hyperactivity-as well as abnormal dendritic spine morphology (3). FMR1 encodes Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein associated to polyribosomes and involved in the translational control of mRNAs important for synaptic plasticity (4). Consistent with a posttranscriptional function, the absence of FMRP in Fmr1 −/y mouse causes abnormal signaling of group 1 metabotropic glutamate receptors (mGluRI), leading to several forms of abnormal synaptic plasticity that rely on protein translation (5, 6). Protein expression analyses confirmed a role of FMRP in neuronal translational control (7), but the extent of this control remains unclear. Although several studies focusing on individual mRNA targets (e.g., Fmr1, Map1b, Psd95, App, etc.) suggest specific control by FMRP (2), studies of global translation, including in vivo labeling in the Fmr1 −/y mouse (8), showed thousands of neuronal proteins deregulated in the absence of FMRP, pointing toward a general translational derepression. Studies seeking to identify the transcripts controlled by FMRP identified can...

show abstract

Chronic Pharmacological mGlu5 Inhibition Corrects Fragile X in Adult Mice

Cited by 440 publications

References 36 publications

Synapse-specific and size-dependent mechanisms of spine structural plasticity accompanying synaptic weakening

Synapse-specific and size-dependent mechanisms of spine structural plasticity accompanying synaptic weakening

Homer1/mGluR5 Activity Moderates Vulnerability to Chronic Social Stress

Fragile X Mental Retardation Protein (FMRP) controls diacylglycerol kinase activity in neurons

Contact Info

Product

Resources

About