Central glutamatergic synapses and the molecular pathways that control them are emerging as common substrates in the pathogenesis of mental disorders. Genetic variation in the contactin associated protein-like 2 (CNTNAP2) gene, including copy number variations, exon deletions, truncations, single nucleotide variants, and polymorphisms have been associated with intellectual disability, epilepsy, schizophrenia, language disorders, and autism. CNTNAP2, encoded by Cntnap2, is required for dendritic spine development and its absence causes disease-related phenotypes in mice. However, the mechanisms whereby CNTNAP2 regulates glutamatergic synapses are not known, and cellular phenotypes have not been investigated in Cntnap2 knockout neurons. Here we show that CNTNAP2 is present in dendritic spines, as well as axons and soma. Structured illumination superresolution microscopy reveals closer proximity to excitatory, rather than inhibitory synaptic markers. CNTNAP2 does not promote the formation of synapses and cultured neurons from Cntnap2 knockout mice do not show early defects in axon and dendrite outgrowth, suggesting that CNTNAP2 is not required at this stage. However, mature neurons from knockout mice show reduced spine density and levels of GluA1 subunits of AMPA receptors in spines. Unexpectedly, knockout neurons show large cytoplasmic aggregates of GluA1. Here we characterize, for the first time to our knowledge, synaptic phenotypes in Cntnap2 knockout neurons and reveal a novel role for CNTNAP2 in GluA1 trafficking. Taken together, our findings provide insight into the biological roles of CNTNAP2 and into the pathogenesis of CNTNAP2-associated neuropsychiatric disorders.A bnormalities in excitatory synapses of cortical pyramidal neurons have emerged as key cellular substrates in the pathogenesis of several psychiatric disorders. Disease-specific disruptions in synaptic morphology or number and glutamate receptors accompany several neuropsychiatric disorders, particularly those that involve deficits in information processing (1). In support of this view, postmortem neuropathological studies found altered dendritic spine density on cortical pyramidal neurons in individuals with intellectual disability (2), autism spectrum disorders (3), and schizophrenia (4). Dendritic spines are the sites of the majority of excitatory glutamatergic synapses in the mammalian brain and represent the postsynaptic compartment of these synapses. Spines are rich in actin, and their morphology changes during development and in various physiological conditions (5). Spines contain glutamate receptors, of which the AMPA subtype are the ones responsible for fast neurotransmission (6). AMPA receptors, like other membrane proteins, are processed in the endoplasmic reticulum and the Golgi complex, then delivered to synapses by forward trafficking mechanisms (7). At the synapse, they undergo constitutive and regulated exo-and endocytosis, known to modulate synapse strength (6). Together, changes in spine number and morphology, along with glutam...
The architecture of dendritic arbors contributes to neuronal connectivity in the brain. Conversely, abnormalities in dendrites have been reported in multiple mental disorders and are thought to contribute to pathogenesis. Rare copy number variations (CNVs) are genetic alterations that are associated with a wide range of mental disorders and are highly penetrant. The 16p11.2 microduplication is one of the CNVs most strongly associated with schizophrenia and autism, spanning multiple genes possibly involved in synaptic neurotransmission. However, disease-relevant cellular phenotypes of 16p11.2 microduplication and the driver gene(s) remain to be identified. We found increased dendritic arborization in isolated cortical pyramidal neurons from a mouse model of 16p11.2 duplication (dp/+). Network analysis identified MAPK3, which encodes ERK1 MAP kinase, as the most topologically important hub in protein-protein interaction networks within the 16p11.2 region and broader gene networks of schizophrenia-associated CNVs. Pharmacological targeting of ERK reversed dendritic alterations associated with dp/+ neurons, outlining a strategy for the analysis and reversal of cellular phenotypes in CNV-related psychiatric disorders.T he architecture of the dendritic arbors defines a pyramidal neuron's dendritic receptive field (1). Moreover, patterns of dendritic arborization are essential to the computational ability of the neuron (1). Generating and maintaining proper dendritic receptive fields is therefore crucial for neural circuit function that underlies complex behaviors. Conversely, alterations in dendrites occur in psychiatric disorders, including schizophrenia and autism spectrum disorder (ASD) (2).Psychiatric disorders have complex genetic architecture that is partly explained by rare variants with high penetrance (3, 4). Though incidences of these rare mutations are low (4-7), the accrued burden of rare variants on disease risk may account for a significant proportion of cases in linked disorders (8). The most well-characterized forms of rare variations are large genomic regional duplications or deletions known as copy number variations (CNVs). CNVs represent large genomic alterations, often encompassing multiple genes, which confer significant risk (odds ratio = 3-30) (9). The increased rare CNV burden is associated with numerous neurodevelopmental psychiatric conditions, including schizophrenia, ASD, and intellectual disability (5, 7, 10, 11). However, due to the large number of genes within CNVs, understanding the relationship between genotype and phenotypes and the rational identification of potential targets for reversing pathologically relevant phenotypes in CNV disorders has been challenging.Recently, much attention has been paid to recurrent microduplication or deletion at the 16p11.2 locus. The ∼600-kb 16p11.2 CNV region encompasses 29 known protein-coding genes and is a hot spot for chromosomal rearrangement (3); 16p11.2 CNVs have been linked to multiple disorders and phenotypes; CNVs of this region are associa...
Postsynaptic trafficking plays a key role in regulating synapse structure and function. While spiny excitatory synapses can be stable throughout adult life, their morphology and function is impaired in Alzheimer’s disease (AD). However, little is known about how AD risk genes impact synaptic function. Here we used structured superresolution illumination microscopy (SIM) to study the late-onset Alzheimer’s disease (LOAD) risk factor BIN1, and show that this protein is abundant in postsynaptic compartments, including spines. While postsynaptic Bin1 shows colocalization with clathrin, a major endocytic protein, it also colocalizes with the small GTPases Rab11 and Arf6, components of the exocytic pathway. Bin1 participates in protein complexes with Arf6 and GluA1, and manipulations of Bin1 lead to changes in spine morphology, AMPA receptor surface expression and trafficking, and AMPA receptor-mediated synaptic transmission. Our data provide new insights into the mesoscale architecture of postsynaptic trafficking compartments and their regulation by a major LOAD risk factor.
Bisphenol A (BPA) is commonly used in the manufacturing of a wide range of consumer products, including polycarbonate plastics, epoxy resin that lines beverage and food cans, and some dental sealants. Consumption of food and beverages containing BPA represents the primary route of human BPA exposure, which is virtually ubiquitous. An increasing number of studies have evaluated the effects of BPA on immune responses in laboratory animals that have reported a variety of effects some of which have been contradictory. To address the divergent findings surrounding BPA exposure, a comprehensive chronic treatment study of BPA was conducted in Sprague-Dawley rats, termed the Consortium Linking Academic and Regulatory Insights on Toxicity of BPA (CLARITY-BPA). As a participant in the CLARITY-BPA project, our studies evaluated the effects of BPA on a broad range of immune function endpoints using spleen cells isolated from BPA or vehicle treated rats. This comprehensive assessment included measurements of lymphoproliferation in response to mitogenic stimuli, immunoglobulin production by B cells, and cellular activation of T cells, NK cells, monocytes, granulocytes, macrophages and dendritic cells. In total, 630 different measurements in BPA treated rats were performed of which 35 measurements were statistically different from vehicle controls. The most substantive alteration associated with BPA treatment was the augmentation of lymphoproliferation in response to pokeweed mitogen stimulations in 1 year old male rats, which was also observed in the reference estrogen ethinyl estradiol treated groups. With the exception of the aforementioned, the statistically significant changes associated with BPA treatment were mostly sporadic and not dose-dependent with only one out of five BPA dose groups showing a statistical difference. In addition, the observed BPA-associated alterations were mostly moderate in magnitude and showed no persistent trend over the one-year time period. Based on these findings, we conclude that the observed BPA-mediated changes observed in this study are unlikely to alter immune competence in adult rats.
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