Astrocytic ZBTB7A promotes orbitofrontal cortex dysfunction associated with Major Depressive Disorder [MDD]
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ABSTRACT: Overall risk for Major Depressive Disorder (MDD) is determined by complex interactions between genetic and environmental factors that influence epigenetic regulation of neuroplasticity and stress pathways1,2. These mechanisms are specific to the distinct regulatory context within regionally-defined brain cell-types3,4. Here, we employed genome-wide chromatin accessibility profiling of neuronal vs. non-neuronal cells in orbitofrontal cortex (OFC) to capture regulatory signatures of MDD. We mapped genetic risk for MDD to active promoters of non-neuronal cell-types in OFC and identified MDD-specific open chromatin regions, which were differentially accessible exclusively in non-neuronal cells. Characterization of these loci revealed a key role for astrocyte dysfunction, and implicated the chromatin remodeling protein ZBTB7A, which coordinates wide-ranging cellular activation programs, including NF-kB inflammatory transcription5. In mice, astrocyte-specific knockdown of Zbtb7a reversed chromatin remodeling, reactive astrocyte transcription, and behavioral deficits associated with chronic stress. Conversely, ZBTB7A overexpression in OFC astrocytes induced stress-related behavioral deficits, promoted widespread inflammatory gene expression, and drove pathophysiological OFC neuronal hyperactivity in response to a mild subthreshold stressor. Our data highlight a critical role for OFC astrocytes in the bidirectional regulation of stress vulnerability and pinpoint ZBTB7A as a key factor mediating maladaptive astrocyte plasticity and OFC neuronal hyperexcitability in MDD.
Project description:Overall risk for Major Depressive Disorder (MDD) is determined by complex interactions between genetic and environmental factors that influence epigenetic regulation of neuroplasticity and stress pathways1,2. These mechanisms are specific to the distinct regulatory context within regionally-defined brain cell-types3,4. Here, we employed genome-wide chromatin accessibility profiling of neuronal vs. non-neuronal cells in orbitofrontal cortex (OFC) to capture regulatory signatures of MDD. We mapped genetic risk for MDD to active promoters of non-neuronal cell-types in OFC and identified MDD-specific open chromatin regions, which were differentially accessible exclusively in non-neuronal cells. Characterization of these loci revealed a key role for astrocyte dysfunction, and implicated the chromatin remodeling protein ZBTB7A, which coordinates wide-ranging cellular activation programs, including NF-kB inflammatory transcription5. In mice, astrocyte-specific knockdown of Zbtb7a reversed chromatin remodeling, reactive astrocyte transcription, and behavioral deficits associated with chronic stress. Conversely, ZBTB7A overexpression in OFC astrocytes induced stress-related behavioral deficits, promoted widespread inflammatory gene expression, and drove pathophysiological OFC neuronal hyperactivity in response to a mild subthreshold stressor. Our data highlight a critical role for OFC astrocytes in the bidirectional regulation of stress vulnerability and pinpoint ZBTB7A as a key factor mediating maladaptive astrocyte plasticity and OFC neuronal hyperexcitability in MDD.
Project description:Overall risk for Major Depressive Disorder (MDD) is determined by complex interactions between genetic and environmental factors that influence epigenetic regulation of neuroplasticity and stress pathways1,2. These mechanisms are specific to the distinct regulatory context within regionally-defined brain cell-types3,4. Here, we employed genome-wide chromatin accessibility profiling of neuronal vs. non-neuronal cells in orbitofrontal cortex (OFC) to capture regulatory signatures of MDD. We mapped genetic risk for MDD to active promoters of non-neuronal cell-types in OFC and identified MDD-specific open chromatin regions, which were differentially accessible exclusively in non-neuronal cells. Characterization of these loci revealed a key role for astrocyte dysfunction, and implicated the chromatin remodeling protein ZBTB7A, which coordinates wide-ranging cellular activation programs, including NF-kB inflammatory transcription5. In mice, astrocyte-specific knockdown of Zbtb7a reversed chromatin remodeling, reactive astrocyte transcription, and behavioral deficits associated with chronic stress. Conversely, ZBTB7A overexpression in OFC astrocytes induced stress-related behavioral deficits, promoted widespread inflammatory gene expression, and drove pathophysiological OFC neuronal hyperactivity in response to a mild subthreshold stressor. Our data highlight a critical role for OFC astrocytes in the bidirectional regulation of stress vulnerability and pinpoint ZBTB7A as a key factor mediating maladaptive astrocyte plasticity and OFC neuronal hyperexcitability in MDD.
Project description:Major Depressive Disorder (MDD) arises from a complex interaction between genetics and environmental influences such as stress, which leads to persistent changes in frontolimbic gene expression and cellular function. Although relatively understudied in depression, the orbitofrontal cortex (OFC) exhibits significant changes in neuronal activity in MDD, as well as widespread gene expression changes, including consistent upregulation of inflammatory stress pathways. Inflammation signaling in non-neuronal cell-types can disrupt normal neurotransmission, though the molecular mechanisms that regulate this interaction are not well understood. Our laboratory has implemented nuclei-sorting coupled with ATAC-seq in human postmortem OFC to characterize over 200 MDD-specific open chromatin regions (OCRs), which were detected exclusively in the non-neuronal cell population. From this dataset, we identified ZBTB7A, a chromatin remodeling protein with binding motifs significantly overrepresented in these MDD-specific OCRs. ZBTB7A has been shown to orchestrate chromatin accessibility for NF-kB target genes, however, its functional role in psychiatric disease has not yet been explored. In a series of studies utilizing astrocyte-specific viral manipulations, we found that overexpressing this chromatin remodeler in rodent OFC astrocytes was sufficient to induce aberrant expression of inflammatory genes, behavioral deficits, and neuronal hyperactivity in response to a mild stressor, compared to GFP-expressing mice. Together, these findings demonstrate a novel chromatin-based mechanism for increased inflammatory signaling in astrocytes that ultimately impairs neuroadaptive responses to stress with direct implications for OFC dysfunction in MDD pathology.
Project description:Increasing evidence implicates astrocytes in stress and depression in both rodent models and human Major Depressive Disorder (MDD). Despite this, little is known about the transcriptional responses to stress of astrocytes within the nucleus accumbens (NAc), a key brain reward region, and their influence on behavioral outcomes. We found a robust transcriptional response in NAc astrocytes to CSDS in stressed mice, with changes seen in both stress-susceptible and stress-resilient animals. Bioinformatic analysis revealed CREB, a transcription factor widely studied in neurons, as one of the top-predicted upstream regulators of the NAc astrocyte transcriptome, with opposite activation states implicated in resilient vs. susceptible mice. Our data demonstrate that the astrocyte transcriptome responds robustly to CSDS and that transcriptional regulation in astrocytes contributes to depressive-like behaviors. A better understanding of transcriptional regulation in astrocytes may reveal unknown molecular mechanisms underlying neuropsychiatric disorders.
Project description:Major Depression (MDD) is a prevalent psychiatric disorder and exposure to stress is robust risk factor for MDD. Clinical data and rodent models have indicated the negative impact of chronic stress induced hormones like cortisol on brain volume, memory, and cell metabolism. However, the cellular and transcriptomic changes that occur in the brain after prolonged exposure to cortisol are less understood. Furthermore, astrocyte-specific contribution to cortisol-induced neuropathology remains understudied. Here, we have developed an in vitro model of “chronic stress” using human induced pluripotent stem cell-derived astrocytes treated with cortisol for 7 days. Whole transcriptome sequencing reveals differentially expressed genes (DEGs) uniquely regulated in chronic cortisol compared to acute cortisol treatment. Utilizing this paradigm, we examined the stress response transcriptome of astrocytes generated from MDD patient iPSCs. MDD-specific DEGs related to GPCR ligand binding, synaptic signaling, and ion homeostasis. Together, these data highlight the unique role astrocytes play in the central nervous system and present interesting genes for future study into the relationship between chronic stress and MDD.
Project description:Astrocytes and neurons coexist and interact in the CNS1,2. Given that many signaling and pathological events are protein-driven, identifying astrocyte and neuron proteomes is essential for elucidating the complex protein networks that dictate their respective contributions to physiology and disease. Here, we used cell- and subcompartment-specific proximity-dependent biotinylation3 to study the proteomes of striatal astrocytes and medium spiny neurons (MSNs) in vivo. We evaluated cytosolic and plasma membrane compartments for astrocytes and MSNs, revealing how these cells differ at the protein level and in their core signaling machinery. We assessed subcellular compartments of astrocytes including end feet and processes to reveal the molecular basis of essential astrocyte signaling and homeostatic functions. Unexpectedly, SAPAP3 proteins (gene; Dlgap3) associated with obsessive compulsive disorder (OCD) and repetitive behaviors4-11 were detected at equivalent levels in striatal astrocyte and MSN plasma membrane and cytosolic compartments. Astrocytic expression was confirmed by RNA-seq, fluorescence in situ hybridization and immunohistochemistry. Furthermore, genetic rescue experiments combined with behavioral analyses and proteomics in a mouse model4 of OCD lacking SAPAP3 revealed contributions of SAPAP3 in astrocytes and MSNs to repetitive and anxiety-related OCD behaviors. Our data define how astrocytes and neurons differ at the protein level and in their major signaling pathways, how astrocyte proteomes vary between physiological subcompartments, and how specific astrocyte and neuronal molecular mechanisms contribute to a psychiatric disease. Targeting both astrocytes and neurons together is likely to be therapeutically effective in complex CNS disorders.
Project description:Diverse subpopulations of astrocytes tile different brain regions to accommodate local requirements of neurons and associated neuronal circuits. Nevertheless, molecular mechanisms governing astrocyte diversity remain mostly unknown. We explored the role of a zinc finger transcription factor Yin Yang 1 (YY1) that is expressed in astrocytes. We found that specific deletion of YY1 from astrocytes causes severe motor deficits in mice, induces Bergmann gliosis, and results in simultaneous loss of GFAP expression in velate and fibrous cerebellar astrocytes. Single cell RNA-seq analysis showed that YY1 exerts specific effects on gene expression in subpopulations of cerebellar astrocytes. We found that although YY1 is dispensable for the initial stages of astrocyte development, it regulates subtype-specific gene expression during astrocyte maturation. Moreover, YY1 is continuously needed to maintain astrocyte identity in the adult cerebellum. Our findings suggest that YY1 plays critical roles regulating cerebellar astrocyte maturation during development and maintaining a mature phenotype of astrocytes in the adult cerebellum.
Project description:Astrocytes can support neuronal survival through a range of secreted signals that protect against neurotoxicity, oxidative stress, and apoptotic cascades. To identify proteins contributing to protective intracellular neuronal signalling originating from astrocytes, endogenous PI3K was immunoprecipitated from Ht22 cells exposed to primary astrocyte conditioned media (ACM) or cell free media (CFM), followed by iTRAQ-based quantitative proteomic analysis.
Project description:Early life stress such as childhood abues and childhood neglect has been frequently implicated in evoking mental disorders later in life. However, it is not well understood what is the underlying mechanism between early life stress and mental disorders. Our in vitro, in vivo and brain organoid experiments revealed that stress hormones increase Mertk expression in astrocytes through glucocorticoid receptor (GR). Furthermore, early life stress (ESD) exposure significantly incrased astrocyte-mediated synapse phagocytosis via GR/MERTK pathway in various brain regions including somatosensory cortex and orbitofrontal cortex. In those brain regions, the excitatory postsynaptic density was remarkably decreased with an increase in astrocytic phagocytosis of excitatory postsynapses. Importantly, ablating GR or MERTK in astrocytes prevented ESD-induced loss of excitatory snapses, abnormal neural activities and behavioral deficits. Taken together, this study revelas a new role of astrocytic GR/MERTK pathway in evoking stress-induced abnormal behaviors in mice, suggesting astrocytic GR/MERTK signaling could be a potential therapeutic target for stress-induced mental disorders.
Project description:Isolation of glia from Alzheimer's mice reveals inflammation and dysfunction. Reactive astrocytes and microglia are associated with amyloid plaques in Alzheimer's disease (AD). Yet, not much is known about the molecular alterations underlying this reactive phenotype. To get an insight into the molecular changes underlying AD induced astrocyte and microglia reactivity, we performed a transcriptional analysis on acutely isolated astrocytes and microglia from the cortex of aged controls and APPswe/PS1dE9 AD mice. As expected, both cell types acquired a proinflammatory phenotype, which confirms the validity of our approach. Interestingly, we observed that the immune alteration in astrocytes was relatively more pronounced than in microglia. Concurrently, our data reveal that astrocytes display a reduced expression of neuronal support genes and genes involved in neuronal communication. The microglia showed a reduced expression of phagocytosis and/or endocytosis genes. Co-expression analysis of a human AD expression data set and the astrocyte and microglia data sets revealed that the inflammatory changes in astrocytes were remarkably comparable in mouse and human AD, whereas the microglia changes showed less similarity. Based on these findings we argue that chronically proinflammatory astrocyte and microglia phenotypes, showing a reduction of genes involved in neuronal support and neuronal signaling, are likely to contribute to the neuronal dysfunction and cognitive decline in AD. 2 cell types from 2 conditions: cortical microglia and cortical astrocytes from 15-18 month old APPswe/PS1dE9 mice compared to wildtype littermates. Biological replicates: microglia from APPswe/PS1dE9, N=7, microglia from WT, N=7, astrocytes from APPswe/PS1dE9, N=4, microglia from WT, N=4