Sex-specific difference on anxiety- and depressive-like behavior in neuronal growth regulator 1-knockout mice

Sex differences are evident in anxiety and depression, and women more frequently present with comorbid anxiety and depression alongside gastrointestinal disturbances. This pattern suggests contributions from sex-specific biological mechanisms and gut-brain communication. Negr1, a molecule regulating neuronal growth and connectivity, has been linked to depression-relevant behaviors in animal models. However, its mechanisms and potential sex-specific effects remain unclear.

Behavioral tests were used to assess phenotypes related to depression, anxiety, and learning in male and female wild-type (WT) and Negr1^-/- mice, and molecular assays were performed to evaluate endoplasmic reticulum (ER) stress and apoptosis in the brain, liver, and colon. Behavioral test data were analyzed using a three-way mixed repeated-measures analysis of variance (RM-ANOVA), and molecular data were analyzed using two-way or three-way ANOVA.

Negr1^-/- mice exhibited sex-dependent phenotypes in both central and peripheral systems. Baseline analyses revealed increased intestinal permeability in Negr1^-/- mice and sex-specific patterns of brain-derived neurotrophic factor (Bdnf) mRNA expression across multiple time points. Behaviorally, Negr1^-/- mice showed increased anxiety-like behavior, decreased social interaction, and impaired spatial learning in the Morris water maze, regardless of sex. Female Negr1^-/- mice displayed impaired fear learning and increased depression-like behavior, while male Negr1^-/- mice exhibited heightened anxiety-like responses. At the molecular level, ER stress marker spliced X-box binding protein 1 (Xbp1s) mRNA was upregulated in peripheral tissues of males but downregulated in females. Apoptosis analysis revealed enhanced caspase-3 activation in peripheral tissues of female Negr1^-/- mice, while males showed no significant changes. Brain tissue showed no significant apoptotic alterations in either sex.

This study demonstrates that, in Negr1^-/- mice, both sexes show general behavioral alterations. However, female Negr1^-/- mice exhibit greater vulnerability to fear learning impairments and depression-like behavior, whereas males Negr1^-/- mice show heightened anxiety responses. These behavioral differences were associated with opposing ER stress responses and differential apoptotic signaling between the sexes in peripheral tissues. Our findings highlight the importance of considering sex as a biological variable in depression research and suggest that Negr1 plays a crucial role in the sex-specific pathophysiology of psychiatric disorders through complex mechanisms spanning central and peripheral systems.