Sex-biased single-cell genetic landscape in mice hippocampus with sub-chronic variable stress

Behavioral phenotyping (sucrose preference, novelty-suppressed feeding) assessed anhedonia. Hippocampal single-cell RNA sequencing (scRNA-seq; 10x Genomics Chromium) was performed on four cohorts: Male-Control, Male-SCVS, Female-Control, Female-SCVS. Sex-stratified differential gene expression, pathway enrichment (GO, KEGG), and mitochondrial gene analysis were conducted. Results: Female mice displayed significantly exacerbated anhedonia (reduced sucrose preference and novelty-suppressed feeding) and selective depletion of plasma serotonin (5-HT) following SCVS exposure, contrasting with minimal behavioral changes in males. Single-cell RNA sequencing of 31,256 hippocampal cells revealed profound sex-dimorphic transcriptional reprogramming: females exhibited a 3-fold greater number of differentially expressed genes (DEGs) than males with minimal overlap (9 shared DEGs). Key mechanistic findings included: (1) Female-biased dysregulation of maternally inherited mitochondrial genes (mt-Atp6 and mt-Co3 upregulated) specifically within oligodendrocytes, linking heightened oxidative stress susceptibility to female vulnerability; (2) Pan-cellular upregulation of the transcription factor Mef2c in females, contrasting with male-specific signatures (NRG-1 upregulated in astrocytes/cholinergic neurons; Slc6a11 downregulated in astrocytes). (3) Divergent pathway alterations, including suppressed oxytocin signaling (social reward) in females versus dysregulated kinase/phosphatase activity (synaptic plasticity) in males, with females further exhibiting coordinated suppression of glutamatergic transmission, astrocytic K⁺ buffering, and cell adhesion; (4) Stress-induced depletion of a baseline oligodendrocyte predominance in females, potentially disrupting hippocampal network synchronization underlying anhedonic behaviors. Conclusion: This study provides the first single-cell atlas of hippocampal sexual dimorphism in stress response. It identifies oligodendrocyte mitochondrial dysfunction, pan-cellular Mef2c upregulation, and oxytocin signaling suppression as central mechanisms underlying female-specific vulnerability to depression-like phenotypes. These findings reveal fundamentally distinct adaptive strategies between sexes and highlight novel, sex-stratified therapeutic targets for MDD.