Astrocytic CREB in nucleus accumbens promotes susceptibility to chronic stress
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ABSTRACT: 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:Despite depression being one of the most prevalent and debilitating disorders worldwide, it has been difficult to understand its pathophysiology and to develop more effective treatments. Maladaptive transcriptional regulation within limbic neural circuits, including reward processing regions such as the nucleus accumbens (NAc), in response to chronic stress is thought to be a major contributor to the development of the syndrome. Epigenetic events?in particular, histone writers and erasers?that alter chromatin structure to regulate programs of gene expression have increasingly been associated with depression-related behavioral abnormalities in animal models and in depressed humans examined postmortem. However, very little is known about the ATP-dependent chromatin remodelers that control nucleosome positioning and the packing state of chromatin. Here we show that the ACF complex, part of the ISWI family of chromatin remodelers, is persistently and selectively upregulated in the NAc of mice that are susceptible to chronic social stress, as well as in the NAc of depressed human. We further establish that ACF induction is both necessary and sufficient for susceptibility to stress-induced depressive-like behaviors. Using ChIP-seq, we demonstrate that altered ACF binding after chronic stress is strongly correlated with altered nucleosome positioning, in particular, around the transcriptional start sites of affected genes. These alterations in ACF binding and nucleosome repositioning are associated with repressed expression of a subset of genes in animals that are susceptible to chronic stress. Together, these findings establish that active ATP-dependent chromatin remodeling by the ACF complex is a key regulator in the repression of genes that mediate susceptibility to social stress, and provide novel candidate targets for improved therapeutics of depression and other stress-related disorders. c57bl/6 mice underwent chronic social defeat stress (CSDS), and social interaction test was used to separate animals into control, susceptible and resilient groups. Nucleus accumbens (NAc) tissue was collected 48 hours after the last defeat session, and then Acf1, SNF2H ChIP-seq or H3 MNase-seq were performed based on the control, susceptible, and resilient groups. Three sequencing replicates were performed on each group.
Project description:Animals susceptible to chronic social defeat stress (CSDS) exhibit depression-related behaviors, and show aberrant transcription across several limbic brain regions. The nucleus accumbens (NAc) in particular shows unique susceptible versus resilient phenotypes at the transcriptional, neuroanatomical, and physiological levels. Early life stress (ELS) promotes susceptibility to CSDS in adulthood, but associated enduring changes in transcriptional control mechanisms in NAc have not yet been investigated. Here, we examined long-lasting changes in histone modifications induced in NAc by ELS and studied their underlying mechanisms in mediating heightened lifelong stress susceptibility in male and female mice. We identify methylation of lysine 79 of histone H3 (H3K79me) and the enzymes that control this modification, selectively in D2-type medium spiny neurons, as crucial for the expression of ELS-induced stress susceptibility, and reveal the transcriptional networks regulated by this mechanism. Finally, we demonstrate the potential clinical viability of this approach by showing that systemic delivery of a small molecule inhibitor of H3K79me reverses ELS-induced behavioral deficits.
Project description:Here we show that ?-catenin mediates pro-resilient and anxiolytic effects in mice in the nucleus accumbens (NAc), a key brain reward region, an effect that is mediated by ?-catenin signaling in D2-type medium spiny neurons (MSNs) specifically. Conversely, blocking ?-catenin function in NAc promotes susceptibility to chronic stress, and we show evidence of robust suppression of ?-catenin transcriptional activity in the NAc both of depressed humans examined postmortem as well as of mice that display a susceptible phenotype after chronic stress, with a converse upregulation in mice that are stress resilient. Using ChIP-seq, we demonstrate a global, genome-wide enrichment of ?-catenin in the NAc of resilient mice, and specifically identify Dicer1—important in small RNA (e.g., microRNA [miRNA]) biogenesis—as a critical ?-catenin target gene involved in mediating a resilient phenotype. Small RNA-seq after excising ?-catenin from the NAc in the context of chronic stress reveals dynamic ?-catenin-dependent miRNA regulation associated with resilience. Control: 2 samples, Resilient: 2 samples, Susceptible: 2 samples; DNA input: 1 sample.
Project description:Paternal stress can induce long-lasting changes in germ cells potentially propagating heritable changes across generations. To date, no studies have investigated differences in transmission patterns between stress-resilient and -susceptible mice. We tested the hypothesis that transcriptional alterations in sperm during chronic social defeat stress (CSDS) transmit increased susceptibility to stress phenotypes to the next generation. We demonstrate differences in offspring from stressed fathers that depend upon paternal category (resilient vs susceptible) and offspring sex. Importantly, artificial insemination reveals that sperm mediates some of the behavioral phenotypes seen in offspring. Using RNA-sequencing we report substantial and distinct changes in the transcriptomic profiles of sperm following CSDS in susceptible vs resilient fathers, with alterations in long noncoding RNAs (lncRNAs) predominating especially in susceptibility. Correlation analysis revealed that these alterations were accompanied by a loss of regulation of protein-coding genes by lncRNAs in sperm of susceptible males. We also identify several co-expression gene modules that are enriched in differentially expressed genes in sperm from either resilient or susceptible fathers. Taken together, these studies advance our understanding of intergenerational epigenetic transmission of behavioral experience.
Project description:Here we show that ?-catenin mediates pro-resilient and anxiolytic effects in mice in the nucleus accumbens (NAc), a key brain reward region, an effect that is mediated by ?-catenin signaling in D2-type medium spiny neurons (MSNs) specifically. Conversely, blocking ?-catenin function in NAc promotes susceptibility to chronic stress, and we show evidence of robust suppression of ?-catenin transcriptional activity in the NAc both of depressed humans examined postmortem as well as of mice that display a susceptible phenotype after chronic stress, with a converse upregulation in mice that are stress resilient. Using ChIP-seq, we demonstrate a global, genome-wide enrichment of ?-catenin in the NAc of resilient mice, and specifically identify Dicer1—important in small RNA (e.g., microRNA [miRNA]) biogenesis—as a critical ?-catenin target gene involved in mediating a resilient phenotype. Small RNA-seq after excising ?-catenin from the NAc in the context of chronic stress reveals dynamic ?-catenin-dependent miRNA regulation associated with resilience. GFP_Control: 12 samples, GFP_Resilient: 12 samples, GFP_Susceptible: 4 samples; CRE_Control: 12 samples, CRE_Susceptible: 8 samples.
Project description:Depression is a complex and heterogeneous disorder and a leading contributor to the global burden of of disease. Most previous research has focused on individual brain regions and individual genes that contribute to depression. However, emerging evidence in both humans and animal models suggests that dysregulated circuit function and gene expression across multiple brain regions drive depressive phenotypes. Here we use a bioinformatics approach intersecting differential expression analysis with weighted gene co-expression network analysis to identify transcriptional networks that regulate susceptibility to depressive-like symptoms in mice. We performed RNA-sequencing on multiple brain regions from control animals and those either susceptible or resilient to chronic social defeat stress (CSDS) at multiple time points after defeat. We bioinformatically identified several transcriptional networks that regulate depression susceptibility, and in vivo manipulations of these networks confirmed their functional significance at the levels of gene transcription, synaptic regulation, and behavior. Our findings reveal novel transcriptional networks that control stress susceptibility and offer fundamentally new leads for antidepressant drug discovery.
Project description:Here we show that β-catenin mediates pro-resilient and anxiolytic effects in mice in the nucleus accumbens (NAc), a key brain reward region, an effect that is mediated by β-catenin signaling in D2-type medium spiny neurons (MSNs) specifically. Conversely, blocking β-catenin function in NAc promotes susceptibility to chronic stress, and we show evidence of robust suppression of β-catenin transcriptional activity in the NAc both of depressed humans examined postmortem as well as of mice that display a susceptible phenotype after chronic stress, with a converse upregulation in mice that are stress resilient. Using ChIP-seq, we demonstrate a global, genome-wide enrichment of β-catenin in the NAc of resilient mice, and specifically identify Dicer1—important in small RNA (e.g., microRNA [miRNA]) biogenesis—as a critical β-catenin target gene involved in mediating a resilient phenotype. Small RNA-seq after excising β-catenin from the NAc in the context of chronic stress reveals dynamic β-catenin-dependent miRNA regulation associated with resilience.
Project description:Here we show that β-catenin mediates pro-resilient and anxiolytic effects in mice in the nucleus accumbens (NAc), a key brain reward region, an effect that is mediated by β-catenin signaling in D2-type medium spiny neurons (MSNs) specifically. Conversely, blocking β-catenin function in NAc promotes susceptibility to chronic stress, and we show evidence of robust suppression of β-catenin transcriptional activity in the NAc both of depressed humans examined postmortem as well as of mice that display a susceptible phenotype after chronic stress, with a converse upregulation in mice that are stress resilient. Using ChIP-seq, we demonstrate a global, genome-wide enrichment of β-catenin in the NAc of resilient mice, and specifically identify Dicer1—important in small RNA (e.g., microRNA [miRNA]) biogenesis—as a critical β-catenin target gene involved in mediating a resilient phenotype. Small RNA-seq after excising β-catenin from the NAc in the context of chronic stress reveals dynamic β-catenin-dependent miRNA regulation associated with resilience.
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.