Biology subjects

Dejanovic, B.

Publications and source records attributed to Dejanovic, B..

8 recordsLinked to original sources

bioRxiv2025

Spatially resolved translational dysregulation in Grin2a+/- mouse model of schizophrenia

Loss-of-function (LoF) mutations of GRIN2A, encoding the GluN2A subunit of N-methyl-D-aspartate receptor (NMDAR), confer a high risk for schizophrenia (SCZ)1-3, yet how they affect diverse brain cell types remains poorly understood. Here, we combined subcellular-resolution spatial omics technologies, STARmap4 and RIBOmap5, to jointly resolve single-cell transcriptomes and translatomes for 3,447 genes in the brains of Grin2a+/- mice and their wild-type littermates across 538,188 cells. Translational dysregulation was markedly more prominent than transcriptional changes in neurons. Across neuronal subtypes, a set of genes including Camk2a, Arc, Egr1, Egr3, Chmp2b, and Pja2 exhibited translational reduction in a Grin2a gene dose-dependent fashion, suggesting a connection between NMDAR hypofunction and reduced protein synthesis of downstream synaptic plasticity effectors. In interneurons (particularly parvalbumin interneurons), a strong reduction of Gad2 translation implies loss of inhibitory function in cortical microcircuits, which has long been hypothesized for SCZ pathophysiology. Non-neuronal cell types including astrocytes, oligodendrocytes, and vascular cells also exhibited region-specific translational changes in neurotransmitter transport, lipid synthesis, myelination, and stress response pathways, some of which co-varied with regional neuron state. Together, our study reveals brain-wide translation dysregulation as a critical mechanism underlying SCZ pathophysiology.

neuroscience↗

bioRxiv2024

Brain-region-specific changes and dysregulation of activity regulated genes in Gria3 mutant mice, a genetic animal model of schizophrenia

Protein-truncating variants in GRIA3 (encoding the GluA3/GluR3 subunit of -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors) are associated with substantially increased risk of schizophrenia (SCZ). Here we characterized Gria3 mutant mice carrying a protein-truncating mutation that mimics a SCZ-associated variant. Transcriptomic analysis revealed that activity-regulated genes are downregulated in cortical regions, while immune and glia-related pathways exhibit brain-region-specific changes. The transcriptomic changes in Gria3 mutant mice are remarkably different from those in Grin2a mutant mice, particularly in the prefrontal cortex, even though both encode glutamate receptors and are associated with SCZ risk. Proteomic analysis further demonstrated that loss-of-function of Gria3 profoundly alters the protein composition of synapses. These findings in a genetic mouse model provide potential insights into the pathophysiological mechanisms underlying SCZ.

neuroscience↗

bioRxiv2024

Elevated synaptic PKA activity and abnormal striatal dopamine signaling in Akap11 mutant mice, a genetic model of schizophrenia and bipolar disorder

AbstractLoss-of-function mutations in AKAP11 (a protein kinase A (PKA)-binding protein) greatly increase the risk of bipolar disorder and schizophrenia. To determine the neurobiological functions of AKAP11, we conduct multi-omic and neurobiological analyses of Akap11 mutant mouse brains. We find that AKAP11 is a key regulator of PKA proteostasis in the brain whose loss leads to dramatically increased levels of PKA subunits and phosphorylated PKA substrates, especially in synapses. Akap11 mutant mice show extensive transcriptomic changes throughout the brain, including prominent decreases in synapse-related genes sets. Gene expression is highly impacted in spiny projection neurons of the striatum, a brain region implicated in motivation, cognition and psychotic disorders. Real-time measurements of PKA activity reveal elevated basal PKA activity in the striatum of Akap11-/- mice, with exaggerated additional response to dopamine receptor antagonists. Behaviorally, Akap11 mutant mice show abnormally prolonged locomotor response to amphetamine, deficits in associative learning and contextual discrimination, as well as depression-like behaviors. Our study connects molecular changes to circuit dysfunction and behavioral disturbance in a genetically valid animal model of psychotic disorder.

neuroscience↗

bioRxiv2022

Brain region-specific changes in neurons and glia and dysregulation of dopamine signaling in Grin2a mutant mice

Schizophrenia disease mechanisms remain poorly understood, in large part due to a lack of valid animal models. Rare heterozygous loss-of-function mutations in GRIN2A, encoding a subunit of the NMDA (N-methyl-d-aspartate) receptor, greatly increase the risk of schizophrenia. By transcriptomic, proteomic, electroencephalogram (EEG) recording and behavioral analysis, we report that heterozygous Grin2a mutant mice show: (i) large-scale gene expression changes across multiple brain regions and in neuronal (excitatory and inhibitory) and non-neuronal cells (astrocytes, oligodendrocytes); (ii) evidence of reduced activity in prefrontal cortex and increased activity in hippocampus and striatum; (iii) elevated dopamine signaling in striatum; (iv) altered cholesterol biosynthesis in astrocytes; (v) reduction of glutamatergic receptor signalin g proteins in the synapse; (iv) heightened gamma oscillation power in EEG; (vi) aberrant locomotor behavioral pattern opposite of that induced by antipsychotic drugs. These findings reveal potential pathophysiologic mechanisms, provide support for both the "hypo-glutamate" and "hyper-dopamine" hypotheses of schizophrenia, and underscore the utility of Grin2a-deficient mice as a new genetic model of schizophrenia.

neuroscience↗

bioRxiv2022

Neuronal pentraxin Nptx2 regulates complement activity in the brain

Complement overactivation mediates microglial synapse elimination in neurological diseases like Alzheimers disease and frontotemporal dementia (FTD), but how complement activity is regulated in the brain remains largely unknown. We identified that the secreted neuronal pentraxin Nptx2 binds complement C1q and thereby regulates its activity in the brain. Nptx2-deficient mice show increased complement activity and C1q-dependent microglial synapse engulfment and loss of excitatory synapses. In a neuroinflammation culture model and in aged TauP301S mice, AAV-mediated neuronal overexpression of Nptx2 was sufficient to restrain complement activity and ameliorate microglia-mediated synapse loss. Analysis of human CSF samples from a genetic FTD cohort revealed significantly reduced levels of Nptx2 and Nptx2-C1q protein complexes in symptomatic patients, which correlated with elevated C1q and activated C3. Together, these results show that Nptx2 regulates complement activity and microglial synapse elimination in the healthy and diseased brain and that diminished Nptx2 levels might exacerbate complement-mediated neurodegeneration in FTD patients.

neuroscience↗

bioRxiv2022

Deep proteomics identifies shared molecular pathway alterations in synapses of schizophrenia and bipolar disorder patients and mouse model

Synaptic dysfunction is implicated in the pathophysiology of schizophrenia (SCZ) and bipolar disorder (BP). We used quantitative mass-spectrometry to carry out deep and unbiased profiling of the proteome of synapses purified from the dorsolateral prefrontal cortex of 35 cases of SCZ, 35 cases of BP, and 35 controls. Compared to controls, SCZ and BP synapses showed substantial and similar proteomic alterations. Network and gene set enrichment analyses revealed upregulation of proteins associated with autophagy and certain vesicle transport pathways, and downregulation of proteins related to synaptic, mitochondrial, and ribosomal function in the synapses of individuals with SCZ or BP. Some of the same pathways (e.g., upregulation of vesicle transport, downregulation of mitochondrial and ribosomal proteins) were similarly dysregulated in the synaptic proteome of mutant mice deficient in Akap11, a recently discovered shared risk gene for SCZ and BP. Our work provides novel biological insights into molecular dysfunction at the synapse in SCZ and BP and serves as a resource for understanding the pathophysiology of these debilitating neuropsychiatric disorders.

neuroscience↗

bioRxiv2022

Integrative in situ mapping of single-cell transcriptional states and tissue histopathology in an Alzheimer's disease model

Amyloid-{beta} plaques and neurofibrillary tau tangles are the neuropathologic hallmarks of Alzheimers disease (AD), but the spatiotemporal cellular responses and molecular mechanisms underlying AD pathophysiology remain poorly understood. Here we introduce STARmap PLUS to simultaneously map single-cell transcriptional states and disease marker proteins in brain tissues of AD mouse models at subcellular resolution (200 nm). This high-resolution spatial transcriptomics map revealed a core-shell structure where disease-associated microglia (DAM) closely contact amyloid-{beta} plaques, whereas disease-associated astrocytes (DAA) and oligodendrocyte precursor cells (OPC) are enriched in the outer shells surrounding the plaque- DAM complex. Hyperphosphorylated tau emerged mainly in excitatory neurons in the CA1 region accompanied by the infiltration of oligodendrocyte subtypes into the axon bundles of hippocampal alveus. The integrative STARmap PLUS method bridges single-cell gene expression profiles with tissue histopathology at subcellular resolution, providing an unprecedented roadmap to pinpoint the molecular and cellular mechanisms of AD pathology and neurodegeneration.

genomics↗

bioRxiv2021

Novel antibodies for the simple and efficient enrichment of native O-GlcNAc modified peptides

Antibodies against post-translational modifications (PTMs) such as lysine acetylation, ubiquitin remnants, or phosphotyrosine have resulted in significant advances in our understanding of the fundamental roles of PTMs in biology. However, the roles of a number of PTMs remain largely unexplored due to the lack of robust enrichment reagents. The addition of N-acetylglucosamine to serine and threonine residues (O-GlcNAc) by the O-GlcNAc transferase (OGT) is a PTM implicated in numerous biological processes and disease states but with limited techniques for its study. Here, we evaluate a new mixture of anti-O-GlcNAc monoclonal antibodies for the immunoprecipitation of native O-GlcNAcylated peptides from cells and tissues. The anti-O-GlcNAc antibodies display good sensitivity and high specificity toward O-GlcNAc-modified peptides, and do not recognize O-GalNAc or GlcNAc in extended glycans. Applying this antibody-based enrichment strategy to synaptosomes from mouse brain tissue samples, we identified over 1,300 unique O-GlcNAc-modified peptides and over 1,000 sites using just a fraction of sample preparation and instrument time required in other landmark investigations of O-GlcNAcylation. Our rapid and robust method greatly simplifies the analysis of O-GlcNAc signaling and will help to elucidate the role of this challenging PTM in health and disease.

biochemistry↗