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Extensive sex differences in depression-linked variants functionally assayed in mouse brain [Hippocampus]

ABSTRACT: Here, we selected >1000 variants from over 30 depression-associated loci using brain epigenomic data, and functionally assayed them using in vivo functional assays in the mouse brain to examine sex-by-genotype interactions. We identify extensive sex-by-allele effects in mature hippocampus, suggesting genetic risk and thus disease mechanisms may be distinct between the sexes. Unbiased informatics approaches indicated a role for nuclear hormone receptors, which was supported by . Further, comparative analysis of allelic function in the neonatal mouse brain, during a key between developmental neonates during the masculinizing testosterone surge, and in the adult hippocampus—a region of interest in depression pathology—but not at 10 days old, a older hormonally quiescent developmental stage juveniles. Our study provides novel insights into depression genetics as influenced by age, biological sex, and cell type, and provides a framework for in vivo parallel assays at a scale not previously shown possible to functionally define interactions between sex and disease variation.

ORGANISM(S): Mus musculus Adeno-associated virus 9

PROVIDER: GSE186346 | GEO | 2023/02/10

REPOSITORIES: GEO

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Project description:Brain structure and function are sexually dimorphic. As neuroscience research has largely focused on the male brain and behavior, the female brain and, in particular, its inherent dynamics have been left underexplored. During the mammalian reproductive period, the female brain is exposed to fluctuating hormone levels over the cycles known as menstrual (in humans) or estrous (in rodents). Variation in estradiol levels has been shown to affect synaptic plasticity in the female brain, including changes in dendritic spine density systematically across the estrous cycle. Female emotionality and cognitive function vary with physiologically fluctuating sex hormone levels. However, the molecular mechanisms underlying the dynamic nature of the female brain structure and function are currently unknown. Here we show that neuronal chromatin organization in the female ventral hippocampus of mouse is dynamic and fluctuates across the estrous cycle. We find changes in chromatin organization associated with the transcriptional activity of nearby genes important for neuronal function, neurotransmission, synapse formation, and behavior. We also link these chromatin dynamics to variation in anxiety-like behavior and to fluctuations in dendritic spine and synaptic density in the ventral hippocampus. In terms of chromatin structure, within-female and between-sex variation are of similar magnitudes, emphasizing the importance of accounting for fluctuating sex-hormone levels in females in the studies of the brain epigenome and behavior. These results provide critical insights into the mechanisms underlying sex-hormone and sex-dependent variation in adult brain structure and function. The study also has implications for better understanding of sex-biased disorders such as depression and anxiety which are strongly associated with sex-hormone status in females and are twice as prevalent in women than in men. This study establishes a foundation for the development of sex-specific approaches to treat sex-biased neuropsychiatric disorders including depression and anxiety disorders.

Project description:Background: Examining transcriptional regulation by existing antidepressants in key neural circuits implicated in depression, and understanding the relationship to transcriptional mechanisms of susceptibility and natural resilience, may help in the search for new therapeutics. Further, given the heterogeneity of treatment response in human populations, examining both treatment response and non-response is critical. Methods: We compared the effects of a conventional monoamine-based tricyclic antidepressant, imipramine (14 daily injections), and a rapidly acting, experimental, non-monoamine-based antidepressant, ketamine (single injection), in mice subjected to chronic social defeat stress, a validated model of depression, and used RNA-sequencing to analyze transcriptional profiles associated with susceptibility, resilience and antidepressant response and non-response in prefrontal cortex (PFC), nucleus accumbens, hippocampus, and amygdala. Results: We identified approximately equal numbers of responder and non-responder mice following ketamine or imipramine treatment. Ketamine induced more expression changes in hippocampus than other brain regions; imipramine induced more expression changes in nucleus accumbens and amygdala. Transcriptional profiles in ketamine and imipramine responders were most similar in PFC, where the least transcriptional regulation occurred for each drug. Non-response reflected both the lack of response-associated gene expression changes and unique gene regulation. In responders, both drugs reversed susceptible associated transcriptional changes as well as induced resilient associated transcription in PFC, with effects varying by drug and brain region studied. Conclusions: We generated a uniquely large resource of gene expression data in four inter-connected limbic brain regions implicated in depression and its treatment with imipramine or ketamine. Our analyses highlight the PFC as a key site of common transcriptional regulation by both antidepressant drugs and in both reversing susceptibility and inducing resilience associated molecular adaptations. In addition, we found region-specific effects of each drug suggesting both common and unique effects of imipramine versus ketamine. mRNA profiles of susceptibility to chronic social defeat stress as well as treatment response were generated across 4 separate brain regions, with a sample size of 3-5 per group.

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Extensive sex differences in depression-linked variants functionally assayed in mouse brain [Hippocampus]

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