Developmental disruption and restoration of brain synaptome architecture in the murine Pax6 neurodevelopmental disease model.

Neurodevelopmental disorders of genetic origin delay the acquisition of normal abilities and cause disabling phenotypes. Nevertheless, spontaneous attenuation and even complete amelioration of symptoms in early childhood and adolescence can occur in many disorders, suggesting that brain circuits possess an intrinsic capacity to overcome the deficits arising from some germline mutations. We examined the molecular composition of almost a trillion excitatory synapses on a brain-wide scale between birth and adulthood in mice carrying a mutation in the homeobox transcription factor Pax6, a neurodevelopmental disorder model.

Learning and reaction times in mouse touchscreen tests are differentially impacted by mutations in genes encoding postsynaptic interacting proteins SYNGAP1, NLGN3, DLGAP1, DLGAP2 and SHANK2.

The postsynaptic terminal of vertebrate excitatory synapses contains a highly conserved multiprotein complex that comprises neurotransmitter receptors, cell-adhesion molecules, scaffold proteins and enzymes, which are essential for brain signalling and plasticity underlying behaviour. Increasingly, mutations in genes that encode postsynaptic proteins belonging to the PSD-95 protein complex, continue to be identified in neurodevelopmental disorders (NDDs) such as autism spectrum disorder, intellectual disability and epilepsy. These disorders are highly heterogeneous, sharing genetic aetiology and comorbid cognitive and behavioural symptoms.

A brainwide atlas of synapses across the mouse life span.

Synapses connect neurons together to form the circuits of the brain, and their molecular composition controls innate and learned behavior. We analyzed the molecular and morphological diversity of 5 billion excitatory synapses at single-synapse resolution across the mouse brain from birth to old age. A continuum of changes alters synapse composition in all brain regions across the life span.

Comprehensive behavioral analysis of heterozygous Syngap1 knockout mice.

Aims: Synaptic Ras GTPase-activating protein 1 (SYNGAP1) regulates synaptic plasticity through AMPA receptor trafficking. SYNGAP1 mutations have been found in human patients with intellectual disability (ID) and autism spectrum disorder (ASD). Almost every individual with SYNGAP1-related ID develops epilepsy, and approximately 50% have ASD.

Computational geometry analysis of dendritic spines by structured illumination microscopy.

Dendritic spines are the postsynaptic sites that receive most of the excitatory synaptic inputs, and thus provide the structural basis for synaptic function. Here, we describe an accurate method for measurement and analysis of spine morphology based on structured illumination microscopy (SIM) and computational geometry in cultured neurons. Surface mesh data converted from SIM images were comparable to data reconstructed from electron microscopic images.

The Developmental Shift of NMDA Receptor Composition Proceeds Independently of GluN2 Subunit-Specific GluN2 C-Terminal Sequences.

The GluN2 subtype (2A versus 2B) determines biophysical properties and signaling of forebrain NMDA receptors (NMDARs). During development, GluN2A becomes incorporated into previously GluN2B-dominated NMDARs. This "switch" is proposed to be driven by distinct features of GluN2 cytoplasmic C-terminal domains (CTDs), including a unique CaMKII interaction site in GluN2B that drives removal from the synapse.

Architecture of the Mouse Brain Synaptome.

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.

Chronic treatment with a MEK inhibitor reverses enhanced excitatory field potentials in Syngap1 mice.

Background: Synaptic Ras-GTPase-activating protein 1 (SYNGAP1) is an abundant brain-specific protein localized at the postsynaptic density of mammalian excitatory synapses. SYNGAP1 functions as a crucial regulator of downstream intracellular signaling triggered by N-methyl-d-aspartate receptor activation. One of the most important signaling pathways regulated by SYNGAP1 is the Ras-Raf-MEK-ERK pathway.

Enhanced cognition and dysregulated hippocampal synaptic physiology in mice with a heterozygous deletion of PSD-95.

PSD-95 is one of the most abundant proteins of the postsynaptic density of excitatory synapses. It functions as the backbone of protein supercomplexes that mediate signalling between membrane glutamate receptors and intracellular pathways. Homozygous deletion of the Dlg4 gene encoding PSD-95 was previously found to cause a profound impairment in operant and Pavlovian conditioning in Dlg4 mice studied in touch screen chambers that precluded evaluation of PSD-95's role in shaping more subtle forms of learning and memory.

Arc Requires PSD95 for Assembly into Postsynaptic Complexes Involved with Neural Dysfunction and Intelligence.

Arc is an activity-regulated neuronal protein, but little is known about its interactions, assembly into multiprotein complexes, and role in human disease and cognition. We applied an integrated proteomic and genetic strategy by targeting a tandem affinity purification (TAP) tag and Venus fluorescent protein into the endogenous Arc gene in mice. This allowed biochemical and proteomic characterization of native complexes in wild-type and knockout mice.

Pro-death NMDA receptor signaling is promoted by the GluN2B C-terminus independently of Dapk1.

Aberrant NMDA receptor (NMDAR) activity contributes to several neurological disorders, but direct antagonism is poorly tolerated therapeutically. The GluN2B cytoplasmic C-terminal domain (CTD) represents an alternative therapeutic target since it potentiates excitotoxic signaling. The key GluN2B CTD-centred event in excitotoxicity is proposed to involve its phosphorylation at Ser-1303 by Dapk1, that is blocked by a neuroprotective cell-permeable peptide mimetic of the region.

Hierarchical organization and genetically separable subfamilies of PSD95 postsynaptic supercomplexes.

PSD95 is an abundant postsynaptic scaffold protein in glutamatergic synapses that assembles into supercomplexes composed of over 80 proteins including neurotransmitter receptors, ion channels and adhesion proteins. How these diverse constituents are organized into PSD95 supercomplexes in vivo is poorly understood. Here, we dissected the supercomplexes in mice combining endogenous gene-tagging, targeted mutations and quantitative biochemical assays.

NMDA receptors are selectively partitioned into complexes and supercomplexes during synapse maturation.

How neuronal proteomes self-organize is poorly understood because of their inherent molecular and cellular complexity. Here, focusing on mammalian synapses we use blue-native PAGE and 'gene-tagging' of GluN1 to report the first biochemical purification of endogenous NMDA receptors (NMDARs) directly from adult mouse brain. We show that NMDARs partition between two discrete populations of receptor complexes and ∼1.

PSD95 nanoclusters are postsynaptic building blocks in hippocampus circuits.

The molecular features of synapses in the hippocampus underpin current models of learning and cognition. Although synapse ultra-structural diversity has been described in the canonical hippocampal circuitry, our knowledge of sub-synaptic organisation of synaptic molecules remains largely unknown. To address this, mice were engineered to express Post Synaptic Density 95 protein (PSD95) fused to either eGFP or mEos2 and imaged with two orthogonal super-resolution methods: gated stimulated emission depletion (g-STED) microscopy and photoactivated localisation microscopy (PALM).

Canalization of genetic and pharmacological perturbations in developing primary neuronal activity patterns.

The function of the nervous system depends on the integrity of synapses and the patterning of electrical activity in brain circuits. The rapid advances in genome sequencing reveal a large number of mutations disrupting synaptic proteins, which potentially result in diseases known as synaptopathies. However, it is also evident that every normal individual carries hundreds of potentially damaging mutations.

A polygenic burden of rare disruptive mutations in schizophrenia.

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.

CYFIP1 coordinates mRNA translation and cytoskeleton remodeling to ensure proper dendritic spine formation.

The CYFIP1/SRA1 gene is located in a chromosomal region linked to various neurological disorders, including intellectual disability, autism, and schizophrenia. CYFIP1 plays a dual role in two apparently unrelated processes, inhibiting local protein synthesis and favoring actin remodeling. Here, we show that brain-derived neurotrophic factor (BDNF)-driven synaptic signaling releases CYFIP1 from the translational inhibitory complex, triggering translation of target mRNAs and shifting CYFIP1 into the WAVE regulatory complex.