Sex-specific role for SLIT1 in regulating stress susceptibility

Major depressive disorder (MDD) is a pervasive and debilitating syndrome characterized by mood disturbances, anhedonia, and alterations in cognition. While the prevalence of MDD is twice as high for women compared to men, little is known about the molecular mechanisms that drive sex differences in depression susceptibility. We discovered that Slit Guidance Ligand 1 (SLIT1), a secreted protein essential for axonal navigation and molecular guidance in cellular migration, is downregulated in the ventromedial prefrontal cortex (vmPFC) of depressed women compared to healthy controls, but not depressed men. This sex-specific downregulation of Slit1 was also observed in the vmPFC of mice exposed to chronic variable stress. To identify a causal, sex-specific role for SLIT1 in depression-related behavioral abnormalities, we performed knockdown (KD) of Slit1 expression in the vmPFC of male and female mice. When combined with stress exposure, vmPFC Slit1 KD reflected the human condition by inducing a sex-specific increase in anxiety- and depression-like behavioral abnormalities in female mice with no effect seen in male mice. Further, we found that vmPFC Slit1 KD caused a pronounced reduction in dendritic arborization and concomitant alterations to electrophysiological properties of vmPFC pyramidal neurons in females. Additionally, RNA-sequencing analysis of the vmPFC following Slit1 KD in female mice revealed an augmented transcriptional stress signature. Together, our findings establish a crucial role for SLIT1 in regulating neurophysiological and transcriptional responses to stress within the vmPFC, and provide mechanistic insight into novel signaling pathways and molecular factors influencing sex differences in depression susceptibility. Overall design: RNA-sequencing analysis of the vmPFC following Slit1 KD in female mice.

重度抑郁症（Major depressive disorder, MDD）是一类广泛流行且具有致残性的综合征，以心境紊乱、快感缺失及认知功能改变为核心特征。相较于男性，女性的MDD患病率为男性的两倍，但目前学界对介导抑郁易感性性别差异的分子机制仍知之甚少。我们发现，Slit导向配体1（Slit Guidance Ligand 1, SLIT1）——一种在轴突导航及细胞迁移的分子导向过程中发挥关键作用的分泌蛋白——在抑郁女性的腹内侧前额叶皮层（ventromedial prefrontal cortex, vmPFC）中表达下调，而抑郁男性的该脑区SLIT1表达并无此变化。在暴露于慢性不可预知应激的小鼠腹内侧前额叶皮层中，同样观察到Slit1的这种性别特异性下调现象。为明确SLIT1在抑郁相关行为异常中的因果性、性别特异性作用，我们分别对雄性和雌性小鼠的腹内侧前额叶皮层进行了Slit1表达敲低（knockdown, KD）。在伴随应激暴露的情况下，雌性小鼠腹内侧前额叶皮层的Slit1敲低可诱导出性别特异性的类焦虑及抑郁样行为异常，而雄性小鼠未出现此类变化，这一结果与人类中的观察相符。进一步研究发现，在雌性小鼠中，腹内侧前额叶皮层的Slit1敲低会显著减少树突分支，并伴随腹内侧前额叶皮层锥体神经元的电生理特性改变。此外，对Slit1敲低后的雌性小鼠腹内侧前额叶皮层进行RNA测序（RNA-sequencing）分析，结果显示其转录应激特征显著增强。综上，本研究证实SLIT1在腹内侧前额叶皮层调控应激相关的神经生理及转录反应中发挥关键作用，并为解析影响抑郁易感性性别差异的新型信号通路与分子因素提供了机制层面的见解。整体实验设计：对雌性小鼠腹内侧前额叶皮层进行Slit1敲低后的RNA测序分析。