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Global Patterns of Gene Expression Associated with Vulnerability and Resilience to Social Defeat

ABSTRACT: While stressful life events are an important cause of psychopathology such as Post-Traumatic Stress Disorder (PTSD) and Major Depressive Disorder (MDD), most individuals exposed to chronic stress remain psychologically unperturbed. The molecular mechanisms such variations in stress resilience remain to be explored. Utilizing a mouse social defeat paradigm as a model for chronic social stress exposure, we segregated socially defeated c57bl/6J mice into Susceptible and Unsusceptible groups based on scores of social avoidance, and these groups differ along multiple behavioral and physiological domains. To explore neuroplastic changes within the mesolimbic dopamine circuit that may explain variations in susceptibility, we examined global patterns of gene expression within the VTA (ventral tegmental area) and the NAc (nucleus accumbens). Tissue punches of NAc and VTA were obtained from either non-defeated control, Susceptible and Unsusceptible mice approximately 48 hours after the cessation of social defeat stress. Data from Illumina sentrix gene expression microarrays revealed three main findings: (1) the total number of genes significantly up or downregulated was considerably higher within the NAc, (2) the Unsusceptible phenotype was associated with the regulation of a much higher number of genes, and (3) as compared to the NAc, the VTA displayed far fewer genes that were identically regulated in both Susceptible and Unsusceptible groups. Taken together, these data strongly suggest that the VTA is an important substrate for transcriptional changes that can be correlated with variations in Susceptibility. In addition, they suggest that changes in anxiety (found in both Susceptible and Unsusceptible groups) versus changes in reward behavior (found only in Susceptilbe mice) can be explained by gene expression changes within the mesolimbic dopamine circuit. Keywords: neural stress response

ORGANISM(S): Mus musculus

PROVIDER: GSE8870 | GEO | 2007/09/01

SECONDARY ACCESSION(S): PRJNA102237

REPOSITORIES: GEO

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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.

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Global Patterns of Gene Expression Associated with Vulnerability and Resilience to Social Defeat

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