Chronic pain due to nerve injury is resistant to current analgesics. Animal models of neuropathic pain show neuronal plasticity and behavioral reflex sensitization in the spinal cord that depend on ...the NMDA receptor 1, 2. We reveal complexes of NMDA receptors with the multivalent adaptor protein PSD-95 3, 4 in the dorsal horn of spinal cord and show that PSD-95 plays a key role in neuropathic reflex sensitization. Using mutant mice expressing a truncated form of the PSD-95 molecule 5, we show their failure to develop the NMDA receptor-dependent hyperalgesia and allodynia seen in the CCI model of neuropathic pain 6, but normal inflammatory nociceptive behavior following the injection of formalin. In wild-type mice following CCI, CaM kinase II inhibitors attenuate sensitization of behavioral reflexes, elevated constitutive (autophosphorylated) activity of CaM kinase II is detected in spinal cord, and increased amounts of phospho-Thr286 CaM kinase II coimmunoprecipitate with NMDA receptor NR2A/B subunits. Each of these changes is prevented in PSD-95 mutant mice although CaM kinase II is present and can be activated. Disruption of CaM kinase II docking to the NMDA receptor and activation may be responsible for the lack of neuropathic behavioral reflex sensitization in PSD-95 mutant mice.
Synapses are found in vast numbers in the brain and contain complex proteomes. We developed genetic labeling and imaging methods to examine synaptic proteins in individual excitatory synapses across ...all regions of the mouse brain. Synapse catalogs were generated from the molecular and morphological features of a billion synapses. Each synapse subtype showed a unique anatomical distribution, and each brain region showed a distinct signature of synapse subtypes. Whole-brain synaptome cartography revealed spatial architecture from dendritic to global systems levels and previously unknown anatomical features. Synaptome mapping of circuits showed correspondence between synapse diversity and structural and functional connectomes. Behaviorally relevant patterns of neuronal activity trigger spatiotemporal postsynaptic responses sensitive to the structure of synaptome maps. Areas controlling higher cognitive function contain the greatest synapse diversity, and mutations causing cognitive disorders reorganized synaptome maps. Synaptome technology and resources have wide-ranging application in studies of the normal and diseased brain.
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•Single-synapse-resolution maps of postsynaptic proteins across the whole mouse brain•Systematic catalogs and anatomical mapping of synapse types and subtypes•Synapse diversity is organized into a synaptome map architecture•Disease-relevant mutations reprogram synaptome maps
Synapse molecular composition and diversity was systematically mapped across the whole mouse brain. A molecular logic orchestrates the spatial architecture of synapse diversity from individual dendrites to the systems level. Synaptome architecture and function is important for cognition and disease.
Schizophrenia is a common disease with a complex aetiology, probably involving multiple and heterogeneous genetic factors. Here, by analysing the exome sequences of 2,536 schizophrenia cases and ...2,543 controls, we demonstrate a polygenic burden primarily arising from rare (less than 1 in 10,000), disruptive mutations distributed across many genes. Particularly enriched gene sets include the voltage-gated calcium ion channel and the signalling complex formed by the activity-regulated cytoskeleton-associated scaffold protein (ARC) of the postsynaptic density, sets previously implicated by genome-wide association and copy-number variation studies. Similar to reports in autism, targets of the fragile X mental retardation protein (FMRP, product of FMR1) are enriched for case mutations. No individual gene-based test achieves significance after correction for multiple testing and we do not detect any alleles of moderately low frequency (approximately 0.5 to 1 per cent) and moderately large effect. Taken together, these data suggest that population-based exome sequencing can discover risk alleles and complements established gene-mapping paradigms in neuropsychiatric disease.
A small number of rare, recurrent genomic copy number variants (CNVs) are known to substantially increase susceptibility to schizophrenia. As a consequence of the low fecundity in people with ...schizophrenia and other neurodevelopmental phenotypes to which these CNVs contribute, CNVs with large effects on risk are likely to be rapidly removed from the population by natural selection. Accordingly, such CNVs must frequently occur as recurrent de novo mutations. In a sample of 662 schizophrenia proband-parent trios, we found that rare de novo CNV mutations were significantly more frequent in cases (5.1% all cases, 5.5% family history negative) compared with 2.2% among 2623 controls, confirming the involvement of de novo CNVs in the pathogenesis of schizophrenia. Eight de novo CNVs occurred at four known schizophrenia loci (3q29, 15q11.2, 15q13.3 and 16p11.2). De novo CNVs of known pathogenic significance in other genomic disorders were also observed, including deletion at the TAR (thrombocytopenia absent radius) region on 1q21.1 and duplication at the WBS (Williams-Beuren syndrome) region at 7q11.23. Multiple de novos spanned genes encoding members of the DLG (discs large) family of membrane-associated guanylate kinases (MAGUKs) that are components of the postsynaptic density (PSD). Two de novos also affected EHMT1, a histone methyl transferase known to directly regulate DLG family members. Using a systems biology approach and merging novel CNV and proteomics data sets, systematic analysis of synaptic protein complexes showed that, compared with control CNVs, case de novos were significantly enriched for the PSD proteome (P=1.72 × 10⁻⁶. This was largely explained by enrichment for members of the N-methyl-D-aspartate receptor (NMDAR) (P=4.24 × 10⁻⁶) and neuronal activity-regulated cytoskeleton-associated protein (ARC) (P=3.78 × 10⁻⁸) postsynaptic signalling complexes. In an analysis of 18 492 subjects (7907 cases and 10 585 controls), case CNVs were enriched for members of the NMDAR complex (P=0.0015) but not ARC (P=0.14). Our data indicate that defects in NMDAR postsynaptic signalling and, possibly, ARC complexes, which are known to be important in synaptic plasticity and cognition, play a significant role in the pathogenesis of schizophrenia.
The postsynaptic proteome of excitatory synapses comprises ~1,000 highly conserved proteins that control the behavioral repertoire, and mutations disrupting their function cause >130 brain diseases. ...Here, we document the composition of postsynaptic proteomes in human neocortical regions and integrate it with genetic, functional and structural magnetic resonance imaging, positron emission tomography imaging, and behavioral data. Neocortical regions show signatures of expression of individual proteins, protein complexes, biochemical and metabolic pathways. We characterized the compositional signatures in brain regions involved with language, emotion and memory functions. Integrating large-scale GWAS with regional proteome data identifies the same cortical region for smoking behavior as found with fMRI data. The neocortical postsynaptic proteome data resource can be used to link genetics to brain imaging and behavior, and to study the role of postsynaptic proteins in localization of brain functions.
The genetic mechanisms regulating the brain and behaviour across the lifespan are poorly understood. We found that lifespan transcriptome trajectories describe a calendar of gene regulatory events in ...the brain of humans and mice. Transcriptome trajectories defined a sequence of gene expression changes in neuronal, glial and endothelial cell-types, which enabled prediction of age from tissue samples. A major lifespan landmark was the peak change in trajectories occurring in humans at 26 years and in mice at 5 months of age. This species-conserved peak was delayed in females and marked a reorganization of expression of synaptic and schizophrenia-susceptibility genes. The lifespan calendar predicted the characteristic age of onset in young adults and sex differences in schizophrenia. We propose a genomic program generates a lifespan calendar of gene regulation that times age-dependent molecular organization of the brain and mutations that interrupt the program in young adults cause schizophrenia.
Characterization of the composition of the postsynaptic proteome (PSP) provides a framework for understanding the overall organization and function of the synapse in normal and pathological ...conditions. We have identified 698 proteins from the postsynaptic terminal of mouse CNS synapses using a series of purification strategies and analysis by liquid chromatography tandem mass spectrometry and large‐scale immunoblotting. Some 620 proteins were found in purified postsynaptic densities (PSDs), nine in AMPA‐receptor immuno‐purifications, 100 in isolates using an antibody against the NMDA receptor subunit NR1, and 170 by peptide‐affinity purification of complexes with the C‐terminus of NR2B. Together, the NR1 and NR2B complexes contain 186 proteins, collectively referred to as membrane‐associated guanylate kinase‐associated signalling complexes. We extracted data from six other synapse proteome experiments and combined these with our data to provide a consensus on the composition of the PSP. In total, 1124 proteins are present in the PSP, of which 466 were validated by their detection in two or more studies, forming what we have designated the Consensus PSD. These synapse proteome data sets offer a basis for future research in synaptic biology and will provide useful information in brain disease and mental disorder studies.
•N-methyl-D-aspartate receptor (NMDAR) targeting drugs may be efficacious for treating mood disorders.•NMDAR, AMPAR and glutamate receptor interacting molecules, including PSD-95, are implicated in ...antidepressant-related behaviors.•Global GluA1 or PSD-95 knockout, or systemic GluN2B antagonist (Ro 25-6981) in C57BL/6J, reduced FST immobility.•GluN2B antagonism reduced FST immobility in GluA1 or interneuronal GluN1 knockouts, but not GluN2A or PSD-95 knockouts.•GluN2B antagonist microinfusion into medial prefrontal cortex, not basolateral amygdala, reduced FST immobility in C57BL/6J.
Drugs targeting the glutamate N-methyl-d-aspartate receptor (NMDAR) may be efficacious for treating mood disorders, as exemplified by the rapid antidepressant effects produced by single administration of the NMDAR antagonist ketamine. Though the precise mechanisms underlying the antidepressant-related effects of NMDAR antagonism remain unclear, recent studies implicate specific NMDAR subunits, including GluN2A and GluN2B, as well as the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) subunit glutamate receptor interacting molecule, PSD-95. Here, integrating mutant and pharmacological in mice, we investigated the contribution of these subunits and molecules to antidepressant-related behaviors and the antidepressant-related effects of the GluN2B blocker, Ro 25-6981. We found that global deletion of GluA1 or PSD-95 reduced forced swim test (FST) immobility, mimicking the antidepressant-related effect produced by systemically administered Ro 25-6981 in C57BL/6J mice. Moreover, the FST antidepressant-like effects of systemic Ro 25-6981 were intact in mutants with global GluA1 deletion or GluN1 deletion in forebrain interneurons, but were absent in mutants constitutively lacking GluN2A or PSD-95. Next, we found that microinfusing Ro 25-6981 into the medial prefrontal cortex (mPFC), but not basolateral amygdala, of C57BL/6J mice was sufficient to produce an antidepressant-like effect. Together, these findings extend and refine current understanding of the mechanisms mediating antidepressant-like effects produced by NMDAR-GluN2B antagonists, and may inform the development of a novel class of medications for treating depression that target the GluN2B subtype of NMDAR.
Proteomics is complementary to genomic approaches anchored in DNA and RNA. Global characterization of proteins is providing new insights into general biological structures as well as synapses, ...receptor complexes and other neuronal and glial features. Current challenges for proteomics of the nervous system include problems relating to sample preparation, brain complexity, limited databases and informatics tools. The combination of proteomics with other global functional genomic approaches at the levels of genome and transcriptome, together with network biology, will provide important bridges between genes, physiology and pathology.
In the nervous system, protein phosphorylation is an essential feature of synaptic function. Although protein phosphorylation is known to be important for many synaptic processes and in disease, ...little is known about global phosphorylation of synaptic proteins. Heterogeneity and low abundance make protein phosphorylation analysis difficult, particularly for mammalian tissue samples. Using a new approach, combining both protein and peptide immobilized metal affinity chromatography and mass spectrometry data acquisition strategies, we have produced the first large scale map of the mouse synapse phosphoproteome. We report over 650 phosphorylation events corresponding to 331 sites (289 have been unambiguously assigned), 92% of which are novel. These represent 79 proteins, half of which are novel phosphoproteins, and include several highly phosphorylated proteins such as MAP1B (33 sites) and Bassoon (30 sites). An additional 149 candidate phosphoproteins were identified by profiling the composition of the protein immobilized metal affinity chromatography enrichment. All major synaptic protein classes were observed, including components of important pre- and postsynaptic complexes as well as low abundance signaling proteins. Bioinformatic and in vitro phosphorylation assays of peptide arrays suggest that a small number of kinases phosphorylate many proteins and that each substrate is phosphorylated by many kinases. These data substantially increase existing knowledge of synapse protein phosphorylation and support a model where the synapse phosphoproteome is functionally organized into a highly interconnected signaling network.
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