Nature-nurture interplay: genetically informative designs contribute to understanding the effects of trauma and interpersonal violence

Oxytocin receptor gene, post-traumatic stress disorder and dissociation in a community sample of European American women

The aims of this study were: (a) to examine associations of oxytocin receptor gene (OXTR) single nucleotide polymorphisms (SNPs) with post-traumatic stress disorder (PTSD) and dissociative symptoms and (b) to investigate gene-environment (G × E) interaction with childhood maltreatment. Salivary DNA samples from 228 women of European ancestry were analysed. Two SNPs, rs237895 and rs237897, were associated with dissociative symptoms but not PTSD diagnosis. Another SNP (rs2254298) was associated with dissociation when interacting with history of childhood maltreatment. These results contribute to theorising and evidence suggesting that the oxytocin system and its genetics may be associated with risk for dissociation among European American women, including those with maltreatment history. Replication with larger patient samples, including men and other ancestry groups, is needed.

The Molecular Genetics of Dissociative Symptomatology: A Transdiagnostic Literature Review

Dissociative disorders are a common and frequently undiagnosed group of psychiatric disorders, characterized by disruptions in the normal integration of awareness, personality, emotion and behavior. The available evidence suggests that these disorders arise from an interaction between genetic vulnerability and stress, particularly traumatic stress, but the attention paid to the underlying genetic diatheses has been sparse. In this paper, the existing literature on the molecular genetics of dissociative disorders, as well as of clinically significant dissociative symptoms not reaching the threshold of a disorder, is reviewed comprehensively across clinical and non-clinical samples. Association studies suggest a link between dissociative symptoms and genes related to serotonergic, dopaminergic and peptidergic transmission, neural plasticity and cortisol receptor sensitivity, particularly following exposure to childhood trauma. Genome-wide association studies have identified loci of interest related to second messenger signaling and synaptic integration. Though these findings are inconsistent, they suggest biologically plausible mechanisms through which traumatic stress can lead to pathological dissociation. However, methodological concerns related to phenotype definition, study power, and correction for the confounding factors limit the value of these findings, and they require replication and extension in studies with better design.

Genetic association of FKBP5 with PTSD in US service members deployed to Iraq and Afghanistan

Post-traumatic stress disorder (PTSD) is a debilitating mental disorder with a prevalence of more than 7% in the US population and 12% in the military. An interaction of childhood trauma with FKBP5 (a glucocorticoid-regulated immunophilin) has been reported to be associated with PTSD in the general population. However, there are few reports on the association of FKBP5 with PTSD, particularly in important high-risk population such as the military. Here, we examined the association between four single-nucleotide polymorphisms (SNPs; rs3800373, rs9296158, rs1360780, rs9470080) covering the FKBP5 gene and probable PTSD in US service members deployed to Iraq and Afghanistan, a high-risk military population (n = 3890) (Hines et al., 2014). We found that probable PTSD subjects were significantly more likely to carry the A-allele of rs3800373, G-allele of rs9296158, C-allele of rs1360780, and C-allele of rs9470080. Furthermore, the four SNPs were in one block of strong pairwise linkage disequilibrium (r = 0.91-0.96). Within the block there were two major haplotypes of CATT and AGCC (rs3800373-rs9296158-rs1360780-rs9470080) that account for 99% of haplotype diversity. The distribution of the AGCC haplotype was significantly higher in probable PTSD subjects compared to non-PTSD (p<.05). The diplotype-based analysis indicated that the AGCC carriers tended to be probable PTSD. In this study, we demonstrated the association between FKBP5 and probable PTSD in US service members deployed to Iraq and Afghanistan, indicating that FKBP5 might be a risk factor for PTSD.

LUMAN/CREB3 is a key regulator of glucocorticoid-mediated stress responses

Altered glucocorticoid sensitivity is believed to contribute to a number of human diseases, including inflammatory and autoimmune conditions as well as disorders characterized by abnormal hypothalamic-pituitary-adrenal axis (HPA) function. LUMAN (or CREB3), originally identified through its interaction with a cell cycle regulator HCFC1, is an endoplasmic reticulum membrane-bound transcription factor that is involved in the unfolded protein response. Here we demonstrate that LUMAN changes the glucocorticoid response by modulating the expression of the glucocorticoid receptor leading to an overall increase in GR activity. Luman-deficient mice exhibited a blunted stress response characterized by low levels of both anxiety and depressive-like behaviour in addition to low circulating corticosterone levels. These mice also have reduced dendritic branching in the CA3 region of the hippocampus, consistent with increased GR responses. These findings are consistent with the notion that elevated GR activities are the primary cause of the observed phenotype in these LUMAN-deficient mice. We thus postulate that LUMAN is a key regulator of GR-mediated signaling and modulates HPA axis reactivity.

Long-term programming of enhanced aggression by peripuberty stress in female rats

Human literature has linked adverse early life experiences with an increased risk to develop violent behaviors in both boys and girls. We have previously shown that male rats submitted to stress during the peripuberty period display as adults abnormal aggressive behavior against both male intruders and female partners. In the present study, we examined whether the same stress protocol would affect the development of aggressive behaviors in female rats. We evaluated the behavior of these peripuberty stressed female rats when confronted, at adulthood, with either female or male intruders, and during their cohabitation with male partners. Given that estrus cycle influences mood and aggressive behaviors, female aggressive behavior was assessed at different estrus cycle phases: estrus and diestrus, and during pregnancy and lactancy. Additionally, we evaluated postpartum plasma levels of vasopressin, oxytocin and corticosterone, hormones associated with aggression and the regulation of social behavior. Compared to control females, females submitted to stressful events during puberty exhibited higher and more sustained rates of aggression during adulthood independently on the estrus cycle or the sex of the intruder, and they had higher levels of plasma vasopressin. Significant correlations between plasma levels of vasopressin and corticosterone and aggressive behavior were also found. Strikingly, our results showed opposite intragroup correlations suggesting a different role of these hormones on aggression depending on life experiences. We provide here an animal model, devoid of cultural influences strongly supporting a role for biological factors in the development of aggressive behaviors following exposure to stressful events at puberty in females.