To explore the functional consequences of ZBTB7A Overexpression in rodent OFC astrocytes in the context of a mild stressor

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. To explore the functional consequences of ZBTB7A Overexpression in rodent OFC astrocytes in the context of a mild stressor, we used an AAV6-GFAP-ZBTB7A vector that overexpresses ZBTB7A vs. GFP. This AAV6 serotype AAV vector has previously been shown to preferentially express transgenes in adult rodent astrocytes. We delivered this AAV6-GFAP-ZBTB7A vector into rodent OFC vs. GFP empty vector controls in order to evaluate the impact of overexpressing ZBTB7A in this region during a mild stressor. Mice were infected intra-OFC with one of the two viruses (on day 0), and give 3 weeks for the transgene to reach maximal expression, followed by either a 1d Subthreshold Social defeat stressor paradigm or control paradigm. Twenty-four hours after the stressor, mice were subjected to three behavioral tests (social interaction, sucrose preference, and forced swim) over a period of 7d, and then mice were sacrificed, and virally infected tissues were microdissected and processed for RNA-seq.