Astrocytic ZBTB7A promotes orbitofrontal cortex dysfunction associated with Major Depressive Disorder [bulk RNA-Seq]

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. Comparative gene expression profiling analysis of RNA-seq data of mouse orbitofrontal cortex bulk tissue.For Zbtb7a knockdown experiments: following bilateral intra-OFC injection of either the AAV6-GFAP-Zbtb7a-KD-mir virus or the AAV6-GFAP-mirNeg control virus to knockdown Zbtb7a expression specifically in OFC astrocytes, mice were randomly assigned to either the control group, or chronic stress group (10 days of chronic social defeat stress). For ZBTB7A-OE experiments: following bilateral intra-OFC injection of either the AAV6-GFAP-ZBTB7A OE virus or the AAV6-GFAP-GFP empty vector control virus to overexpress ZBTB7A specifically in OFC astrocytes and put through acute stress (1 day of social defeat stress).

重度抑郁症（Major Depressive Disorder, MDD）的整体患病风险由遗传与环境因素间的复杂相互作用决定，此类因素可调控神经可塑性与应激通路的表观遗传调控过程[1,2]。这类调控机制具有细胞类型特异性，依赖于脑区限定的不同细胞类型内独特的调控环境[3,4]。本研究对眶额叶皮层（orbitofrontal cortex, OFC）内的神经元与非神经元细胞开展全基因组染色质开放谱分析（genome-wide chromatin accessibility profiling），以捕捉MDD的调控特征。我们将MDD的遗传风险位点定位至OFC中非神经元细胞的活性启动子区域，并鉴定出仅在非神经元细胞中呈现差异开放的MDD特异性开放染色质区域。对这些基因座的表征揭示了星形胶质细胞功能异常的关键作用，同时关联到染色质重塑蛋白ZBTB7A——该蛋白可协调包括核因子κB（NF-κB）炎性转录在内的广泛细胞激活程序[5]。在小鼠模型中，OFC星形胶质细胞特异性敲低Zbtb7a可逆转染色质重塑、反应性星形胶质细胞转录特征，并改善慢性应激诱导的行为缺陷。反之，在OFC星形胶质细胞中过表达ZBTB7A则会诱发应激相关行为缺陷，促进广泛的炎性基因表达，并在轻度亚阈值应激刺激下导致OFC神经元的病理性过度激活。本研究数据凸显了OFC星形胶质细胞在双向调控应激易感性中的关键作用，并明确ZBTB7A是介导MDD中适应性不良的星形胶质细胞可塑性与OFC神经元过度兴奋的核心因子。本研究还对小鼠OFC整体组织的RNA测序（RNA-seq）数据开展了比较基因表达谱分析。针对Zbtb7a敲低实验：通过双侧OFC内注射AAV6-GFAP-Zbtb7a-KD-mir病毒或AAV6-GFAP-mirNeg对照病毒，特异性敲低OFC星形胶质细胞中的Zbtb7a表达后，将小鼠随机分配至对照组或慢性应激组（接受10天慢性社会挫败应激）。针对ZBTB7A过表达实验：通过双侧OFC内注射AAV6-GFAP-ZBTB7A过表达病毒或AAV6-GFAP-GFP空载体对照病毒，特异性在OFC星形胶质细胞中过表达ZBTB7A，随后对小鼠施加急性应激（1天社会挫败应激）。