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. RNA-sequencing analysis of the vmPFC following Slit1 KD in female mice.