The role of memory-related gene WWC1 (KIBRA) in lifetime posttraumatic stress disorder: evidence from two independent samples from African conflict regions

Subcutaneous Mycobacterium vaccae ameliorates the effects of early life adversity alone or in combination with chronic stress during adulthood in male and female mice

Chronic psychosocial stress is a burden of modern society and poses a clear risk factor for a plethora of somatic and affective disorders, of which most are associated with an activated immune status and chronic low-grade inflammation. Preclinical and clinical studies further suggest that a failure in immunoregulation promotes an over-reaction of the inflammatory stress response and, thus, predisposes an individual to the development of stress-related disorders. Therefore, all genetic (i.e., sex) and environmental (i.e., early life adversity; ELA) factors facilitating an adult's inflammatory stress response are likely to increase their stress vulnerability. In the present study we investigated whether repeated subcutaneous (s.c.) administrations with a heat-killed preparation of Mycobacterium vaccae (M. vaccae; National Collection of Type Cultures (NCTC) 11659), an abundant soil saprophyte with immunoregulatory properties, are protective against negative behavioral, immunological and physiological consequences of ELA alone or of ELA followed by chronic psychosocial stress during adulthood (CAS) in male and female mice. ELA was induced by the maternal separation (MS) paradigm, CAS was induced by 19 days of chronic subordinate colony housing (CSC) in males and by a 7-week exposure to the social instability paradigm (SIP) in females. Our data indicate that ELA effects in both sexes, although relatively mild, were to a great extent prevented by subsequent s.c. M. vaccae administrations. Moreover, although the use of different paradigms for males and females impedes a direct comparison, male mice seemed to be more susceptible to CAS than females, with only females benefitting slightly from the stress protective effects of s.c. M. vaccae administrations when given prior to CAS alone. Finally, our data support the hypothesis that female mice are more vulnerable to the additive effects of ELA and CAS than male mice and that s.c. M. vaccae administrations subsequent to ELA but prior to CAS are protective in both sexes. Taken together and considering the limitation that CAS in males and females was induced by different paradigms, our findings are consistent with the hypotheses that murine stress vulnerability during different phases of life is strongly sex dependent and that developing immunoregulatory approaches, such as repeated s.c. administrations with immunoregulatory microorganisms, have potential for prevention/treatment of stress-related disorders.

Sex differences in PTSD risk: evidence from post-conflict populations challenges the general assumption of increased vulnerability in females

Background: Next to the dose-dependent effect of trauma load, female sex represents a well-established risk factor for PTSD. Exposure to particularly toxic traumatic event types, different coping styles, and biological risk factors are frequently listed as potential causes for the increased PTSD vulnerability in females. Nevertheless, sex differences have not been consistently observed in all study populations. Objective: To investigate sex differences in PTSD risk in post-conflict populations from different countries while considering trauma load. Method: In civilian post-conflict samples from Northern Uganda (N = 1665), Rwanda (N = 433), Syria (N = 974) and Sri Lanka (N = 165), we investigated sex differences in PTSD risk while taking trauma load into account. PTSD and trauma load were assessed using standardized diagnostic interviews. Potential sex differences in PTSD risk were analysed by logistic regression analyses considering trauma load. Results: Across all samples, males reported more traumatic events than females. Both sexes predominantly reported war-related traumatic events. Without considering trauma load, sex effects in PTSD risk were only detected in the Syrian sample. When taking trauma load into account, evidence for an increased PTSD vulnerability in females was found in the Syrian sample, and, to a much lesser extent, in the Northern Ugandan sample. Conclusion: In contrast to the literature, we did not find evidence for a general increased PTSD vulnerability in females. The dose-response effect of trauma load was a much stronger predictor of PTSD risk than sex across all samples.

Does cumulative exposure to traumatic stressors predict treatment outcome of community-implemented exposure-based therapy for PTSD?

Background: Posttraumatic Stress Disorder (PTSD) is associated with high levels of functional impairments such as difficulties in academic or occupational performance and in social relationships. With an increasing number of traumatic event types experienced (trauma load), PTSD risk increases in a dose-dependent manner. Accordingly, high rates of PTSD can impair the reconstruction process in post-conflict societies. In order to meet these high needs for mental health services in societies with little access to professional care, task shifting approaches and community-based interventions have been suggested. Narrative Exposure Therapy (NET) has been developed as a short and pragmatic exposure-based PTSD treatment that can be easily trained to lay personnel. Yet, it remains unclear whether NET can be effectively provided by trained lay counsellors even at high levels of trauma load. Objective: To investigate whether trauma load influences the treatment effectiveness of NET provided by trained and supervised local lay counsellors. Method: Linear mixed models were calculated to investigate the influence of trauma load on treatment effectiveness in a sample of N = 323 rebel war survivors from Northern Uganda with PTSD. Results: We found a strong reduction of PTSD symptoms following NET, which was not influenced by trauma load. However, individuals with higher levels of trauma load reported higher PTSD symptoms before therapy as well as 4 and 10 months following treatment completion compared to individuals with lower trauma load. Conclusions: Treatment with NET by lay counsellors is effective independent of trauma load. However, individuals with higher trauma load have a higher probability to show residual symptoms, which might require additional time, sessions or treatment modules.

de Quervain D, Elbert T, Kolassa S, Kolassa IT. Genetic variation is associated with PTSD risk and aversive memory: Evidence from two trauma-Exposed African samples and one healthy European sample

The probability to develop posttraumatic stress disorder (PTSD), characterized by vivid, intrusive emotional memories of the encountered traumatic events, depends - among other factors - on the number of previous traumatic experiences (traumatic load) and individual genetic vulnerability. So far, our knowledge regarding the biological underpinnings of PTSD is relatively sparse. Genome-wide association studies (GWAS) followed by independent replication might help to discover novel, so far unknown biological mechanisms associated with the development of traumatic memories. Here, a GWAS was conducted in N = 924 Northern Ugandan rebel war survivors and identified seven suggestively significant single nucleotide polymorphisms (SNPs; p ≤ 1 × 10^-5) for lifetime PTSD risk. Of these seven SNPs, the association of rs3852144 on chromosome 5 was replicated in an independent sample of Rwandan genocide survivors (N = 370, p < .01). While PTSD risk increased with accumulating traumatic experiences, the vulnerability was reduced in carriers of the minor G-allele in an additive manner. Correspondingly, memory for aversive pictures decreased with higher number of the minor G-allele in a sample of N = 2698 healthy Swiss individuals. Finally, investigations on N = 90 PTSD patients treated with Narrative Exposure Therapy indicated an additive effect of genotype on PTSD symptom change from pre-treatment to four months after treatment, but not between pre-treatment and the 10-months follow-up. In conclusion, emotional memory formation seems to decline with increasing number of rs3852144 G-alleles, rendering individuals more resilient to PTSD development. However, the impact on therapy outcome remains preliminary and further research is needed to determine how this intronic marker may affect memory processes in detail.

Integrated genetic, epigenetic, and gene set enrichment analyses identify NOTCH as a potential mediator for PTSD risk after trauma: Results from two independent African cohorts

The risk of developing posttraumatic stress disorder (PTSD) increases with the number of traumatic event types experienced (trauma load) in interaction with other psychobiological risk factors. The NOTCH (neurogenic locus notch homolog proteins) signaling pathway, consisting of four different trans‐membrane receptor proteins (NOTCH1–4), constitutes an evolutionarily well‐conserved intercellular communication pathway (involved, e.g., in cell–cell interaction, inflammatory signaling, and learning processes). Its association with fear memory consolidation makes it an interesting candidate for PTSD research. We tested for significant associations of common genetic variants of NOTCH1–4 (investigated by microarray) and genomic methylation of saliva‐derived DNA with lifetime PTSD risk in independent cohorts from Northern Uganda (N₁ = 924) and Rwanda (N₂ = 371), and investigated whether NOTCH‐related gene sets were enriched for associations with lifetime PTSD risk. We found associations of lifetime PTSD risk with single nucleotide polymorphism (SNP) rs2074621 (NOTCH3) (p_uncorrected = 0.04) in both cohorts, and with methylation of CpG site cg17519949 (NOTCH3) (p_uncorrected = 0.05) in Rwandans. Yet, none of the (epi‐)genetic associations survived multiple testing correction. Gene set enrichment analyses revealed enrichment for associations of two NOTCH pathways with lifetime PTSD risk in Ugandans: NOTCH binding (p_corrected = 0.003) and NOTCH receptor processing (p_corrected = 0.01). The environmental factor trauma load was significant in all analyses (all p < 0.001). Our integrated methodological approach suggests NOTCH as a possible mediator of PTSD risk after trauma. The results require replication, and the precise underlying pathophysiological mechanisms should be illuminated in future studies.

Integrating genetic, epigenetic, and gene set enrichment analyses, while accounting for the environmental factor traumatic load, we identified stress‐ and memory‐associated neurogenic locus notch homolog protein (NOTCH) genes and related gene sets as potential risk mediators for the development of posttraumatic stress disorder (PTSD) after trauma. Thus, our results strengthen the presumed role of memory‐ and inflammation‐associated genes in PTSD development, and revealed a promising target for future treatment studies. Furthermore, we demonstrated the importance of traumatic load in PTSD etiology, and of an integrated approach in order to obtain a more comprehensive understanding of the functionality of PTSD‐associated markers.

The role of KIBRA in reconstructive episodic memory

BACKGROUND

In order to retrieve episodic past events, the missing information needs to be reconstructed using information stored in semantic memory. Failures in these reconstructive processes are expressed as false memories. KIBRA single nucleotide polymorphism (rs17070145) has been linked to episodic memory performance as well as an increased risk of Alzheimer's disease and post-traumatic stress disorder (PTSD).

METHODS

Here, the role of KIBRA rs17070145 polymorphism (male and female CC vs. CT/TT carriers) in reconstructive episodic memory in the Deese-Roediger-McDermott (DRM) paradigm was investigated in N = 219 healthy individuals.

RESULTS

Female participants outperformed males in the free recall condition. Furthermore, a trend towards a gender x genotype interaction was found for false recognition rates. Female CT/TT carriers exhibited a lower proportion of false recognition rates for associated critical lures as compared to male CT/TT. Additionally, an association between KIBRA rs17070145 genotype, familiarity and recollection based recognition performance was found. In trials with correct recognition of listed items CT/TT carriers showed more "remember", but fewer "know" responses as compared to CC carriers.

DISCUSSION AND CONCLUSION

Our findings suggest that the T-allele of KIBRA rs17070145 supports recollection based episodic memory retrieval and contributes to memory accuracy in a gender dependent manner. Findings are discussed in the context of the specific contribution of KIBRA related SNPs to reconstructive episodic memory and its implications for cognitive and emotional symptoms in dementia and PTSD.

Stigmatization Is Associated With Increased PTSD Risk After Traumatic Stress and Diminished Likelihood of Spontaneous Remission-A Study With East-African Conflict Survivors

Studies in conflict population have repeatedly documented that the number of traumatic event types experienced (trauma load) increases the risk to develop posttraumatic stress disorder (PTSD) in a dose-dependent manner. Misconceptions about survivors' experiences and actions during the war, as well as mental health symptoms frequently lead to stigmatization by their own families and the community, which might render them even more vulnerable for PTSD development and prevent successful recovery. We therefore investigated whether stigmatization affects trauma-related psychopathology beyond the well-known effect of trauma load. The study sample comprised N = 1131 survivors of the rebel war led by the Lord's Resistance Army (LRA) in Northern Uganda, including a large proportion of formerly abducted individuals and child soldiers. We investigated how the experience of stigmatization affects PTSD risk and the likelihood of spontaneous remission, taking trauma load into account. Further, the association of stigmatization with treatment outcome was determined in a subsample of N = 284 individuals with PTSD who received trauma-focused psychotherapy. More than one third of the total sample, and almost two-thirds of the therapy subsample, reported experiences of stigmatization. The main reasons for stigmatization were related to an association with a rebel group (e.g., being called a rebel), followed by mental health problems/PTSD symptoms and HIV/AIDS. Stigmatization was strongly associated with a higher prevalence of lifetime and current PTSD, a diminished probability of spontaneous remission and higher PTSD symptoms before and after trauma-focused psychotherapy, beyond the effect of trauma load. In sum, our results support the assumption that stigmatization aggravates trauma-related psychopathology and impede symptom improvement. In post-conflict regions, community and family interventions which aim at reducing stigmatization and discrimination might therefore complement individual psychotherapy in order to allow survivors to recover and reintegrate into society.

Hippo Signaling: Emerging Pathway in Stress-Related Psychiatric Disorders?

Discovery of the Hippo pathway and its core components has made a significant impact on our progress in the understanding of organ development, tissue homeostasis, and regeneration. Upon diverse extracellular and intracellular stimuli, Hippo signaling regulates stemness, cell proliferation and apoptosis by a well-conserved signaling cascade, and disruption of these systems has been implicated in cancer as well as metabolic and neurodegenerative diseases. The central role of Hippo signaling in cell biology also results in prominent links to stress-regulated pathways. Genetic variations, epigenetically provoked upregulation of Hippo pathway members and dysregulation of cellular processes implicated in learning and memory, are linked to an increased risk of stress-related psychiatric disorders (SRPDs). In this review, we summarize recent findings, supporting the role of Hippo signaling in SRPDs by canonical and non-canonical Hippo pathway interactions.

Serum KIBRA mRNA and Protein Expression and Cognitive Functions in Depression

BACKGROUND

Genes participating in synaptic signalling or plasticity in brain regions such as the prefrontal cortex (PFC) and the hippocampus have been implicated in cognition. Recently, a new gene (KIBRA, WWC1) has been added to this group due to its impact on memory performance. Recurrent depressive disorder (rDD) is a multifactorial disease, that one of the typical features is cognitive impairment. The main objective of this study was to perform an analysis of the KIBRA gene on both mRNA and protein levels in patients suffering from rDD and to investigate the relationship between KIBRA expression and cognitive performance.

MATERIAL/METHODS

The study comprised 236 subjects: patients with rDD (n=131) and healthy subjects (n=105, HS). Cognitive function assessment was based on: Trail Making Test, The Stroop Test, Verbal Fluency Test and Auditory Verbal Learning Test.

RESULTS

Both mRNA and protein expression levels of KIBRA gene were significantly higher in healthy subjects when compared to rDD. The presented relationship is clear even after taking age, education and sex of the examined subjects into consideration. No statistically significant relationship was found in the experiments between any of the conducted tests and KIBRA gene expression on mRNA level for both the rDD and HS groups. The presented study has limitations related to the fact that patients were being treated with antidepressant. This is relevant due to the fact that some antidepressants may affect mRNA expression. Number of patients and healthy subjects may result in the lack of statistical significance in some cases.

CONCLUSIONS

1. The results of our study show decreased expression of the KIBRA gene on both mRNA and protein levels in depression. 2. We did not find any significant relationship between KIBRA gene expression and cognitive functions in case of both the healthy subjects and the patients affected by rDD.

Genetic Association Between KIBRA Polymorphism and Alzheimer's Disease with in a Japanese Population

KIBRA plays an important role in synaptic plasticity in human hippocampus related to cognitive function. Functional studies suggest that KIBRA is a potential candidate gene for memory and Alzheimer's disease (AD) risk. A single nucleotide polymorphism, Rs17070145 C allele affects the onset of AD in an age-dependent manner comparing with T/T genotypes and is also associated with risk of substance abuse and relapse. The aim of this case-control study was to investigate whether the rs17070145 polymorphism affected the onset of AD in an age-dependent manner in a Japanese population. We analysed KIBRA and APOE genotypes in 237 young AD cases, 154 age-matched control cases and 160 old AD cases. The analyses were performed by stratifying alcohol consumption and the APOE status. We used single photon emission computed tomography (SPECT) to analyse patients with AD with the rs17070145 polymorphism. The genotypic and allelic frequencies of the young AD group differed significantly from those of control and old AD groups. There was a significant association among high alcohol consumption (HAC-AD group) and the genotypic and allelic frequencies of the rs17070145 polymorphism. Logistic regression analyses demonstrate synergism between the APOE genotype and the rs17070145 C allele to increase the risk of AD in the young group; this was confirmed in the HAC-AD group. The SPECT study revealed hyperperfusion in the C allele carrier group was detected in the right inferior frontal gyrus compared with the T/T group. KIBRA rs17070145 affects specific phenotypes of patients with AD.

Genomic predictors of combat stress vulnerability and resilience in U.S. Marines: A genome-wide association study across multiple ancestries implicates PRTFDC1 as a potential PTSD gene

BACKGROUND

Research on the etiology of post-traumatic stress disorder (PTSD) has rapidly matured, moving from candidate gene studies to interrogation of the entire human genome in genome-wide association studies (GWAS). Here we present the results of a GWAS performed on samples from combat-exposed U.S. Marines and Sailors from the Marine Resiliency Study (MRS) scheduled for deployment to Iraq and/or Afghanistan. The MRS is a large, prospective study with longitudinal follow-up designed to identify risk and resiliency factors for combat-induced stress-related symptoms. Previously implicated PTSD risk loci from the literature and polygenic risk scores across psychiatric disorders were also evaluated in the MRS cohort.

METHODS

Participants (N=3494) were assessed using the Clinician-Administered PTSD Scale and diagnosed using the DSM-IV diagnostic criterion. Subjects with partial and/or full PTSD diagnosis were called cases, all other subjects were designated controls, and study-wide maximum CAPS scores were used for longitudinal assessments. Genomic DNA was genotyped on the Illumina HumanOmniExpressExome array. Individual genetic ancestry was determined by supervised cluster analysis for subjects of European, African, Hispanic/Native American, and other descent. To test for association of SNPs with PTSD, logistic regressions were performed within each ancestry group and results were combined in meta-analyses. Measures of childhood and adult trauma were included to test for gene-by-environment (GxE) interactions. Polygenic risk scores from the Psychiatric Genomic Consortium were used for major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SCZ).

RESULTS

The array produced >800K directly genotyped and >21M imputed markers in 3494 unrelated, trauma-exposed males, of which 940 were diagnosed with partial or full PTSD. The GWAS meta-analysis identified the phosphoribosyl transferase domain containing 1 gene (PRTFDC1) as a genome-wide significant PTSD locus (rs6482463; OR=1.47, SE=0.06, p=2.04×10(-9)), with a similar effect across ancestry groups. Association of PRTFDC1 with PTSD in an independent military cohort showed some evidence for replication. Loci with suggestive evidence of association (n=25 genes, p<5×10(-6)) further implicated genes related to immune response and the ubiquitin system, but these findings remain to be replicated in larger GWASs. A replication analysis of 25 putative PTSD genes from the literature found nominally significant SNPs for the majority of these genes, but associations did not remain significant after correction for multiple comparison. A cross-disorder analysis of polygenic risk scores from GWASs of BPD, MDD, and SCZ found that PTSD diagnosis was associated with risk sores of BPD, but not with MDD or SCZ.

CONCLUSIONS

This first multi-ethnic/racial GWAS of PTSD highlights the potential to increase power through meta-analyses across ancestry groups. We found evidence for PRTFDC1 as a potential novel PTSD gene, a finding that awaits further replication. Our findings indicate that the genetic architecture of PTSD may be determined by many SNPs with small effects, and overlap with other neuropsychiatric disorders, consistent with current findings from large GWAS of other psychiatric disorders.

Progress towards understanding the genetics of posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a complex syndrome that occurs following exposure to a potentially life threatening traumatic event. This review summarises the literature on the genetics of PTSD including gene-environment interactions (GxE), epigenetics and genetics of treatment response. Numerous genes have been shown to be associated with PTSD using candidate gene approaches. Genome-wide association studies have been limited due to the large sample size required to reach statistical power. Studies have shown that GxE interactions are important for PTSD susceptibility. Epigenetics plays an important role in PTSD susceptibility and some of the most promising studies show stress and child abuse trigger epigenetic changes. Much of the molecular genetics of PTSD remains to be elucidated. However, it is clear that identifying genetic markers and environmental triggers has the potential to advance early PTSD diagnosis and therapeutic interventions and ultimately ease the personal and financial burden of this debilitating disorder.

Epigenetic modification of the glucocorticoid receptor gene is linked to traumatic memory and post-traumatic stress disorder risk in genocide survivors

Recent evidence suggests that altered expression and epigenetic modification of the glucocorticoid receptor gene (NR3C1) are related to the risk of post-traumatic stress disorder (PTSD). The underlying mechanisms, however, remain unknown. Because glucocorticoid receptor signaling is known to regulate emotional memory processes, particularly in men, epigenetic modifications of NR3C1 might affect the strength of traumatic memories. Here, we found that increased DNA methylation at the NGFI-A (nerve growth factor-induced protein A) binding site of the NR3C1 promoter was associated with less intrusive memory of the traumatic event and reduced PTSD risk in male, but not female survivors of the Rwandan genocide. NR3C1 methylation was not significantly related to hyperarousal or avoidance symptoms. We further investigated the relationship between NR3C1 methylation and memory functions in a neuroimaging study in healthy subjects. Increased NR3C1 methylation-which was associated with lower NR3C1 expression-was related to reduced picture recognition in male, but not female subjects. Furthermore, we found methylation-dependent differences in recognition memory-related brain activity in men. Together, these findings indicate that an epigenetic modification of the glucocorticoid receptor gene promoter is linked to interindividual and gender-specific differences in memory functions and PTSD risk.

The role of FKBP5 genotype in moderating long-term effectiveness of exposure-based psychotherapy for posttraumatic stress disorder

Exposure-based therapies are considered the state-of-the-art treatment for Posttraumatic Stress Disorder (PTSD). Yet, a substantial number of PTSD patients do not recover after therapy. In the light of the well-known gene × environment interactions on the risk for PTSD, research on individual genetic factors that influence treatment success is warranted. The gene encoding FK506-binding protein 51 (FKBP5), a co-chaperone of the glucocorticoid receptor (GR), has been associated with stress reactivity and PTSD risk. As FKBP5 single-nucleotide polymorphism rs1360780 has a putative functional role in the regulation of FKBP5 expression and GR sensitivity, we hypothesized that this polymorphism influences PTSD treatment success. We investigated the effects of FKBP5 rs1360780 genotype on Narrative Exposure Therapy (NET) outcome, an exposure-based short-term therapy, in a sample of 43 survivors of the rebel war in Northern Uganda. PTSD symptom severity was assessed before and 4 and 10 months after treatment completion. At the 4-month follow-up, there were no genotype-dependent differences in therapy outcome. However, the FKBP5 genotype significantly moderated the long-term effectiveness of exposure-based psychotherapy. At the 10-month follow-up, carriers of the rs1360780 risk (T) allele were at increased risk of symptom relapse, whereas non-carriers showed continuous symptom reduction. This effect was reflected in a weaker treatment effect size (Cohen's D=1.23) in risk allele carriers compared with non-carriers (Cohen's D=3.72). Genetic factors involved in stress response regulation seem to not only influence PTSD risk but also responsiveness to psychotherapy and could hence represent valuable targets for accompanying medication.