Distinct molecular mechanisms of stress habituation in the mouse hippocampus [snRNA-seq]. Distinct molecular mechanisms of stress habituation in the mouse hippocampus [snRNA-seq]

We explore how the tightly regulated molecular response triggered by acute restraint stress becomes altered after repeated restraint exposure. Transcriptomic sampling of the mouse hippocampus at multiple time points revealed that repeated stress leads to widespread habituation, damping stress-induced gene expression of all stress-responsive genes. However, we find no evidence for the emergence of new response profiles or alterations in baseline gene expression. Using single-cell multi-omics, we show that these findings hold true across cell types, and we reveal cell type specific patterns of habituation. Transcriptomic and chromatin accessibility profiles identify two distinct mechanisms that contribute to the observed habituation patterns: an early cAMP-associated mechanism that is related to blunted transcription after chronic stress, and a late corticosterone-dependent mechanism that is linked to a shortened transcriptional response. Overall design: Restraint stress involves placing the mice in a 50 ml Falcon tube with a large air hole for 1h30. Chronically stressed animals were subjected to daily restraint for 10 consecutive days at varying time of day before the final (acute) stress exposure, while handling animals were handled gently (lifting the animals by the tail, simulating the handling method used before restraint stress). Following this treatment, animals were single-housed 24 hours before being subjected once again to the same restraint stress, and the samples were collected at various timepoints (see ‘ARS timepoint’ column) following stress initiation. All stress exposures were carried out between 10:00 and 17:00 in the animals’ active phase (i.e. reverse light cycle).

本研究探讨了急性束缚应激（acute restraint stress）触发的严格调控分子应答，在反复束缚暴露后所发生的改变。研究团队于多个时间点对小鼠海马体开展转录组采样（transcriptomic sampling），结果显示反复应激可引发广泛的习惯化效应，抑制所有应激响应基因的应激诱导基因表达。然而，本研究未发现新应答模式出现或基线基因表达发生改变的证据。
借助单细胞多组学（single-cell multi-omics）技术，我们证实上述结论在各类细胞类型中均成立，并揭示了细胞类型特异性的习惯化模式。转录组与染色质开放谱（chromatin accessibility profiles）分析鉴定出两种介导所观察到的习惯化模式的不同机制：其一为早期环磷酸腺苷（cAMP）相关机制，该机制与慢性应激后的转录钝化密切相关；其二为晚期皮质酮（corticosterone）依赖型机制，该机制与转录应答过程的缩短存在关联。
实验整体设计：束缚应激实验是将小鼠置于带有大通气孔的50 ml Falcon管中，束缚时长为1.5小时。慢性应激组动物在接受最终急性应激暴露前，连续10天每日于不同时段接受束缚应激；常规处理对照组动物仅接受轻柔抓取（通过提拉尾部，模拟束缚应激前的常规操作手法）。上述处理完成后，所有动物均单笼饲养，24小时后再次接受相同的束缚应激，并于应激启动后的多个时间点采集样本（详见"ARS timepoint"列）。所有应激操作均于动物活动期（即反向光周期）的10:00至17:00之间开展。