Medial prefrontal cortex transcriptome of mice susceptible or resilient to chronic stress

Stressful circumstances are significant contributors to mental illnesses, such as major depressive disorder. Anhedonia, which is the loss of the ability to enjoy pleasure, including rewarding activities or social contexts, is considered a key symptom of depression. Although stress-induced depression is associated with anhedonia in humans and animals, the underlying molecular mechanisms of anhedonic responses remain poorly understood. In this study, we conducted RNA sequencing to profile the medial prefrontal cortex which was substantially associated with the CUS-induced anhedonic behavioral phenotypes. Employing chronic unpredictable stress (CUS), we determined two subpopulations based on sucrose preference, which was highly correlated with social reward: susceptible (SUS, anhedonic) vs. resilient (RES, non-anhedonic) groups. We identified Syt4 as a hub gene in a gene network unique to anhedonia by conducting a weighted gene co-expression network analysis of the RNA sequencing data from the mPFC of SUS and RES mice. We also confirmed that Syt4 overexpression in the mPFC was pro-susceptible, while the Syt4 knockdown was pro-resilient; the pro-susceptible effects of SYT4 were mediated through the reduction of brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling in the mPFC. These findings suggested that SYT4-BDNF interactions in the mPFC could be a crucial regulatory mechanism of anhedonic susceptibility to chronic stress.