Functional characterization of an oxytocin receptor gene variant (rs2268498) previously associated with social cognition by expression analysis in vitro and in human brain biopsy

Association of verbal and non-verbal theory of mind abilities with non-coding variants of OXTR in youth with autism spectrum disorder and typically developing individuals: a case-control study

BACKGROUND

The ability to attribute mental states to others is called theory of mind (ToM) and is a substantial component of social cognition. This ability is abnormally developed in individuals with autism spectrum disorder (ASD). Several studies over the past decade have identified the oxytocin receptor gene (OXTR) and its variants as promising components for explaining the molecular mechanisms underlying Theory of Mind (ToM). The main aim of this study is to examine the association between rs2268498 and rs53576, two functional single nucleotide polymorphisms (SNPs), and verbal and non-verbal ToM in children and adolescents with ASD and a group of typically developing youth.

METHODS

The study involved 44 children and adolescents with high-functioning ASD aged 8 to 18 years old and 44 TD individuals who were matched on age and sex. In all participants, blood samples were collected and rs2268498 and rs53576 were genotyped. Happe's Strange Stories test and the moving shapes paradigm were used to measure verbal and non-verbal ToM in all participants.

RESULTS

The results of permutation tests and logistic regression suggested that in TD group, rs2268498 AA carriers showed significant higher scores in variables representing verbal ToM (ToM stories and appropriateness score) whereas, in ASD group, rs53576 AA carriers exhibited significant better performance in parameters related to non-verbal ToM (ToM general rule and intentionality score). The results of hierarchical clustering in both groups support the findings by distinguishing between language-related and language-independent aspects of ToM.

CONCLUSIONS

In the present study, we examined the association between rs2268498 and rs53576 and social functioning in individuals with ASD and TD group. We found preliminary evidence that rs2268498 and rs53576 are associated with ToM related abilities in healthy individuals as well as in autistic individuals. Accordingly, rs2268498 and rs53576 may play an important role in predicting ToM capabilities. It will be necessary to conduct further research to address the association of genetic variants with a deficit in ToM in individuals with ASD.

Relationship between oxytocin receptor gene polymorphism and hypertension in Turkish population

INTRODUCTION AND OBJECTIVES

Known to play a key role in uterine contraction and milk ejection, the neuropeptide, oxytocin, has cardiovascular effects. To date, the known cardiovascular effects of oxytocin are blood pressure lowering (caused by natriuresis and atrial natriuretic peptide release), negative inotropic and chronotropic effect caused by parasympathetic neuromodulation, anti-stress effect and vasodilation mediated by activation of the nitric oxide pathway. The clinical significance of the rs2268498 polymorphism in oxytocin receptors in these effects is controversial. Based on the known genetic inheritance of hypertension, our research aimed to determine whether the presence of the rs2268498 oxytocin receptor (OXTR) allele C affects hypertension in our region.

METHODS

This article is a case-control study conducted in the Turkish population. About 140 normotensive and 140 isolated hypertensive volunteers included in the research and genotyped with real-time PCR hybridization method via melt curve analysis.

RESULTS

Oxytocin receptor rs2268498 polymorphism was assessed in terms of the risk of hypertension and hypertensive individuals were compared to the control group. OXTR rs2268498 polymorphism was not found to be a significant risk factor for dominant, recessive and additive modeled hypertension (ORdominant: 0.966, 95% CI: 0.57-1.61, p: 0.9; ORrecessive: 1, 95% CI: 0.58-1.71, p: 1.0 and ORoverall: 0.98, chi2=0.01).

CONCLUSION

We concluded that rs2268498 single nucleotide polymorphism is not a risk factor for hypertension in our region.

Enhanced endogenous oxytocin signaling in the brain modulates neural responses to social misalignment and promotes conformity in humans: A multi-locus genetic profile approach

The neuropeptide oxytocin (OT) is known to promote social conformity. However, the specific neurocognitive mechanisms underlying OT-induced conformity remain unclear. We aimed to address this gap by examining how genetic variation in the oxytocin receptor gene (OXTR) is linked with behavioral conformity and its underlying neural systems. Specifically, we utilized the genotype-tissue expression database (GTEx) to create a novel multi-locus genetic profile score (MPS) that reflects the level of OXTR expression in the human brain. A total of 194 participants (Neuroimaging N = 50, Behavioral N = 144) performed a novel conformity task in which they viewed a series of word pairs depicting various moral values and virtues widely recognized in the United States. In each trial, participants indicated the relative importance of these words and subsequently learned about the majority opinion. Participants later rated the same word pairs a second time. Changes in participants' ratings between the first and second sessions were measured and analyzed with respect to social feedback, blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signals, and OXTR MPS. We found that participants adjusted their ratings in accordance with the majority opinions. Social misalignment between self and others activated brain areas such as the striatum and the posterior medial frontal cortex (pMFC). However, unlike most findings from previous studies, activation in the pMFC during the inconsistent social feedback negatively, rather than positively, predicted behavioral conformity. Notably, those with higher OXTR MPS had reduced pMFC activation in the face of social misalignment, which led to greater conformity. Our findings suggest that OT may promote conformity by dampening the conflict-related signals in the pMFC. They also show that OXTR MPS may be useful for studying the effect of genes on highly complex human social traits, such as conformity.

Functional Polymorphisms in Oxytocin and Dopamine Pathway Genes and the Development of Dispositional Compassion Over Time: The Young Finns Study

Background: We define compassion as an enduring disposition that centers upon empathetic concern for another person's suffering and the motivation to act to alleviate it. The contribution of specific candidate genes to the development of dispositional compassion for others is currently unknown. We examine candidate genes in the oxytocin and dopamine signaling pathways.

Methods: In a 32-year follow-up of the Young Finns Study (N = 2,130, 44.0% men), we examined with multiple indicators latent growth curve modeling the molecular genetic underpinnings of dispositional compassion for others across the life span. We selected five single nucleotide polymorphisms (SNPs) whose functions are known in humans: rs2268498 (OXTR), rs3796863 (CD38) (related to lower oxytocin levels), rs1800497 (ANKK1/DRD2), rs4680 (COMT), and rs1611115 (DBH) (related to higher dopamine levels). Compassion was measured with Cloninger's Temperament and Character Inventory on three repeated observations spanning 15 years (1997–2012). Differences between gender were tested.

Results: We did not find an effect of the five SNPs in oxytocin and dopamine pathway genes on the initial levels of dispositional compassion for others. Individuals who carry one or two copies of the T-allele of DBH rs1611115, however, tend to increase faster in compassion over time than those homozygotes for the C-allele, b = 0.063 (SE = 0.027; p = 0.018). This effect was largely driven by male participants, 0.206 (SE = 0.046; p < 0.001), and was not significant in female participants when analyzed separately.

Conclusions: Men who are known to have, on average, lower compassion than women seem to reduce this difference over time if they carry the T-allele of DBH rs1611115. The direction of the association indicates that dopamine signaling activity rather than overall dopamine levels might drive the development of compassion.

Molecular genetics of neurotransmitters and neuropeptides involved in Internet use disorders including first insights on a potential role of hypothalamus' oxytocin hormone

This chapter covers the phenomenon of Internet use disorders (IUDs) and putative associations with different neurotransmitter and neuropeptide systems. Genes coding for such messengers can be seen as an important starting point in the complicated quest to understand human behavior including new phenomena such as IUDs. Therefore, a special focus of this chapter will lie on individual differences in molecular genetic underpinnings of neurotransmitter and neuropeptide systems and their associations with individual differences in tendencies towards IUDs. By shedding light on these associations, putative predisposing molecular genetic factors for the emergence and maintenance of IUDs can be carved out. Therefore, first an introduction to IUDs and a model that can guide research on putative associations of IUDs with different specific neurotransmitters and neuropeptides will be presented. Subsequently, twin studies on the heritability of IUDs are reviewed. Finally, studies on differences in molecular genetic predispositions and their associations with differences in IUDs will be presented and discussed, including targets related to the dopaminergic and serotonergic system as well as the hypothalamic neuropeptide oxytocin. The chapter closes with a conclusion about what is already known and what needs to be investigated in future studies to gain further insights into putative associations between molecular genetic markers and IUDs.

Burnout in university faculty: An interaction between subjective sleep quality and the OXTR rs2268498 polymorphism

BACKGROUND

Job burnout is a stress-related syndrome influenced by both genetic and environmental factors. Poor sleep quality acting as a stressor may lead to job burnout. The oxytocin receptor gene (OXTR) related to stress reactivity may also exert an effect on job burnout. We aimed to explore the effect of sleep quality, a functional OXTR rs2268498 polymorphism, and their interaction on job burnout in the Chinese population, which has not been explored yet.

METHODS

A preliminary study was performed using a cross-sectional design. The Pittsburgh Sleep Quality Index (PSQI) and the Malash Burnout Inventory (MBI) were measured from 575 healthy subjects. The OXTR rs2468498 polymorphism was genotyped in 376 subjects.

RESULTS

There were significant main effects of sleep quality (p<0.05), but not of the OXTR rs2468498 genotype on burnout. Interestingly, the interaction between sleep quality and the rs2468498 genotype was significant (p<0.05). In the poor sleep group, the C allele (C/C and T/C) carriers showed higher Emotional Exhaustion level than T homozygotes, while in the good sleep group, the C allele carrier showed a lower Emotional Exhaustion level.

LIMITATIONS

This study covered subjects from only one university and the sample size for genotyping was relatively small. As we analyzed only the OXTR rs2268498 polymorphism, this study could not reveal the effects of the cerebrospinal oxytocin concentration and the haplotypes.

CONCLUSIONS

Our findings suggest that the OXTR polymorphism modulates the influence of subjective sleep quality on burnout. We conclude that the C allele of the OXTR rs2468498 polymorphism plays a susceptible role in job burnout.

Oxytocin and the stress buffering effect of social company: a genetic study in daily life

Social relationships are a crucial determinant of both mental and physical health. This effect is partly due to social buffering of stress. Animal studies suggest that social buffering is mediated via the oxytocin system, while studies in humans are sparse and limited by the low ecological validity of laboratory settings. In the present study, participants (N = 326) completed smartphone questionnaires four times a day over 4 to 5 days, measuring stressors, negative affect, and social context to assess social buffering. We found that under stress, participants reported a higher need for social company. Further, the impact of prior stressful events on momentary negative affect was attenuated by the perceived pleasantness of current social company. This social buffering effect was moderated by haplotypes of the oxytocin receptor gene, based on two well-described single nucleotide polymorphisms (rs2268498, rs53576). Effects were robust when controlling for gender and age, applying different data quality criteria, and even apparent in genotype-based analyses. Our findings demonstrate that social buffering and its modulation by oxytocin system characteristics have implications for life as lived outside the laboratory.

A genetic profile of oxytocin receptor improves moral acceptability of outcome-maximizing harm in male insurance brokers

In recent years, conflicting findings have been reported in the scientific literature about the influence of dopaminergic, serotonergic and oxytocinergic gene variants on moral behavior. Here, we utilized a moral judgment paradigm to test the potential effects on moral choices of three polymorphisms of the Oxytocin receptor (OXTR): rs53576, rs2268498 and rs1042770. We analyzed the influence of each single polymorphism and of genetic profiles obtained by different combinations of their genotypes in a sample of male insurance brokers (n = 129), as compared to control males (n = 109). Insurance brokers resulted significantly more oriented to maximize outcomes than control males, thus they expressed more than controls the utilitarian attitude phenotype. When analyzed individually, none of the selected variants influenced the responses to moral dilemmas. In contrast, a composite genetic profile that potentially increases OXTR activity was associated with higher moral acceptability in brokers. We hypothesize that this genetic profile promotes outcome-maximizing behavior in brokers by focusing their attention on what represents a greater good, that is, saving the highest number of people, even though at the cost of sacrificing one individual. Our data suggest that investigations in a sample that most expresses the phenotype of interest, combined with the analysis of composite genetic profiles rather than individual variants, represent a promising strategy to find out weak genetic influences on complex phenotypes, such as moral behavior.

An epistasis between dopaminergic and oxytocinergic systems confers risk of post-traumatic stress disorder in a traumatized Chinese cohort

Post-traumatic stress disorder (PTSD) is a psychiatric syndrome that occurs after trauma exposure. Neurotransmitters such as dopamine and oxytocin have been reported to be involved in neuropathology of PTSD. Previous studies indicated that the dopamine–oxytocin interaction may contribute to behavioral disorders. Thus, exploring the epistasis (gene–gene interaction) between oxytocinergic and dopaminergic systems might be useful to reveal the genetic basis of PTSD. In this study, we analyzed two functional single nucleotide polymorphisms (SNPs), rs2268498 for oxytocinergic gene OXTR and rs1801028 for dopaminergic gene DRD2 based on putative oxytocin receptor–dopamine receptor D2 (OTR–DR2) heterocomplex in a Chinese cohort exposed to the 2008 Wenchuan earthquake (156 PTSD cases and 978 controls). Statistical analyses did not find any single variant or gene–environment interaction (SNP × earthquake-related trauma exposure) associated with provisional PTSD diagnosis or symptoms. An OXTR–DRD2 interaction (rs2268498 × rs1801028) was identified to confer risk of provisional PTSD diagnosis (OR = 9.18, 95% CI = 3.07–27.46 and P = 7.37e-05) and further subset analysis indicated that rs2268498 genotypes controlled the association directions of rs1801028 and rs1801028 genotypes also controlled the association directions of rs2268498. Rs2268498 × rs1801028 is also associated with PTSD symptoms (P = 0.043). Our study uncovered a genetic and putative function-based contribution of dopaminergic–oxytocinergic system interaction to PTSD.

Affective Language, Interpretation Bias and Its Molecular Genetic Variations: Exploring the Relationship Between Genetic Variations of the OXTR Gene (rs53576 and rs2268498) and the Emotional Evaluation of Words Related to the Self or the Other

Several studies have demonstrated links between oxytocin and socio-emotional information processing. Regarding the frequently studied single nucleotide polymorphism (SNP) rs53576 and the less studied, functional polymorphism rs2268498 of the oxytocin receptor (OXTR) gene, previous research suggested that their variants might be associated with different proficiency in the processing of social information. Differences between the genotype variants are not restricted to non-verbal stimulus processing but have also been reported in the verbal domain. Moreover, there is evidence that oxytocin expression influences empathic communication and language development during childhood, indicating that language-based theory-of-mind abilities may be affected by interindividual differences in OXTR genotypes as well. The present study therefore investigates whether two prominent SNPs of the OXTR gene (rs53576 GG vs. A+; rs2268498 TT vs. C+) also play a role in the affective evaluation of verbal stimuli varying in emotional valence and in self-other reference. Participants (N = 149 Caucasian participants, 104 females; A+: n = 80, GG: n = 69; C+: n = 98, TT: n = 51) were presented a series of written, self-, other-, and unreferenced words of positive, negative, and neutral valence and asked to affectively evaluate each word pair as positive, negative, or neutral by button press. In line with previous research, reaction times and accuracy (number of valence-congruent responses) showed a self-positivity bias (i.e., preferential processing of self-related positive words), which, however, was unaffected by participants' genotype. Regarding affective evaluation of neutral words (interpretation bias), A+ carriers displayed a weaker positive interpretation bias compared to GG carriers in the other- and unreferenced stimulus categories. C+ carriers showed a weaker positive interpretation bias than TT carriers in the self-reference condition and in the other-reference condition. These effects were independent from participants' gender. The present results suggest that the OXTR genotype and hence participants' genetic oxytocin sensitivity may cause an interpretation bias in the spontaneous appraisal of neutral words.

Evolutionary diversity as a catalyst for biological discovery

The tremendous diversity of animal behaviors has inspired generations of scientists from an array of biological disciplines. To complement investigations of ecological and evolutionary factors contributing to behavioral evolution, modern sequencing, gene editing, computational and neuroscience tools now provide a means to discover the proximate mechanisms upon which natural selection acts to generate behavioral diversity. Social behaviors are motivated behaviors that can differ tremendously between closely related species, suggesting phylogenetic plasticity in their underlying biological mechanisms. In addition, convergent evolution has repeatedly given rise to similar forms of social behavior and mating systems in distantly related species. Social behavioral divergence and convergence provides an entry point for understanding the neurogenetic mechanisms contributing to behavioral diversity. We argue that the greatest strides in discovering mechanisms contributing to social behavioral diversity will be achieved through integration of interdisciplinary comparative approaches with modern tools in diverse species systems. We review recent advances and future potential for discovering mechanisms underlying social behavioral variation; highlighting patterns of social behavioral evolution, oxytocin and vasopressin neuropeptide systems, genetic/transcriptional "toolkits," modern experimental tools, and alternative species systems, with particular emphasis on Microtine rodents and Lake Malawi cichlid fishes.

Feasibility of Linking Molecular Genetic Markers to Real-World Social Network Size Tracked on Smartphones

The study of individual differences in human social behavior has a long tradition in (personality) psychology focusing on traits such as extraversion linked to vividness and assertiveness. The study of molecular genetic underpinnings of individual differences in social behavior produced many genetic association studies with only few genetic variants, robustly associated with individual differences in personality. One possible reason for non-replication of findings might be the different inventories used to assess human social traits. Moreover, self-report methods to assess personality and social behavior might be problematic due to their susceptibility to different biases such as social desirability or poor abilities in self-reflection. We stress the importance of including recorded behavior to understand the molecular genetic basis of individual differences in personality and linked social traits. We present preliminary data linking oxytocin genetics to individual differences in social network size derived from smartphones. Here, the genetic variation rs2268498, located in the adjacent area of the promoter of the gene coding for the oxytocin receptor (OXTR), was linked to the number of active contacts and incoming calls, tracked on the smartphone for 12 days (note that these results became a bit weaker when age was controlled for). Although the present empirical findings should only be seen as a proof of concept study, this work demonstrates the feasibility to combine molecular genetic variables with real world behavior. If this approach keeps its promises, the field of personality research might experience a boost in psychometric quality in the near future.

The Oxytocin Receptor: From Intracellular Signaling to Behavior

The many facets of the oxytocin (OXT) system of the brain and periphery elicited nearly 25,000 publications since 1930 (see FIGURE 1 , as listed in PubMed), which revealed central roles for OXT and its receptor (OXTR) in reproduction, and social and emotional behaviors in animal and human studies focusing on mental and physical health and disease. In this review, we discuss the mechanisms of OXT expression and release, expression and binding of the OXTR in brain and periphery, OXTR-coupled signaling cascades, and their involvement in behavioral outcomes to assemble a comprehensive picture of the central and peripheral OXT system. Traditionally known for its role in milk let-down and uterine contraction during labor, OXT also has implications in physiological, and also behavioral, aspects of reproduction, such as sexual and maternal behaviors and pair bonding, but also anxiety, trust, sociability, food intake, or even drug abuse. The many facets of OXT are, on a molecular basis, brought about by a single receptor. The OXTR, a 7-transmembrane G protein-coupled receptor capable of binding to either Gαior Gαqproteins, activates a set of signaling cascades, such as the MAPK, PKC, PLC, or CaMK pathways, which converge on transcription factors like CREB or MEF-2. The cellular response to OXT includes regulation of neurite outgrowth, cellular viability, and increased survival. OXTergic projections in the brain represent anxiety and stress-regulating circuits connecting the paraventricular nucleus of the hypothalamus, amygdala, bed nucleus of the stria terminalis, or the medial prefrontal cortex. Which OXT-induced patterns finally alter the behavior of an animal or a human being is still poorly understood, and studying those OXTR-coupled signaling cascades is one initial step toward a better understanding of the molecular background of those behavioral effects.

Emotion recognition associated with polymorphism in oxytocinergic pathway gene ARNT2

The ability to correctly understand the emotional expression of another person is essential for social relationships and appears to be a partly inherited trait. The neuropeptides oxytocin and vasopressin have been shown to influence this ability as well as face processing in humans. Here, recognition of the emotional content of faces and voices, separately and combined, was investigated in 492 subjects, genotyped for 25 single nucleotide polymorphisms (SNPs) in eight genes encoding proteins important for oxytocin and vasopressin neurotransmission. The SNP rs4778599 in the gene encoding aryl hydrocarbon receptor nuclear translocator 2 (ARNT2), a transcription factor that participates in the development of hypothalamic oxytocin and vasopressin neurons, showed an association that survived correction for multiple testing with emotion recognition of audio-visual stimuli in women (n = 309). This study demonstrates evidence for an association that further expands previous findings of oxytocin and vasopressin involvement in emotion recognition.

Oxytocin and vasopressin neural networks: Implications for social behavioral diversity and translational neuroscience

Oxytocin- and vasopressin-related systems are present in invertebrate and vertebrate bilaterian animals, including humans, and exhibit conserved neuroanatomical and functional properties. In vertebrates, these systems innervate conserved neural networks that regulate social learning and behavior, including conspecific recognition, social attachment, and parental behavior. Individual and species-level variation in central organization of oxytocin and vasopressin systems has been linked to individual and species variation in social learning and behavior. In humans, genetic polymorphisms in the genes encoding oxytocin and vasopressin peptides and/or their respective target receptors have been associated with individual variation in social recognition, social attachment phenotypes, parental behavior, and psychiatric phenotypes such as autism. Here we describe both conserved and variable features of central oxytocin and vasopressin systems in the context of social behavioral diversity, with a particular focus on neural networks that modulate social learning, behavior, and salience of sociosensory stimuli during species-typical social contexts.

How Oxytocin Receptor (OXTR) Single Nucleotide Polymorphisms Act on Prosociality: The Mediation Role of Moral Evaluation

Prosociality is related to numerous positive outcomes, and mechanisms underlying individual differences in prosociality have been widely discussed. Recently, research has found converging evidence on the influence of the oxytocin receptor (OXTR) gene on prosociality. Meanwhile, moral reasoning, a key precursor for social behavior, has also been associated with variability in OXTR gene, thus the relationship between OXTR and prosociality is assumed to be mediated by moral evaluation. The current study examines the relationship in question, and includes gender as a potential moderator. Self-reported prosociality on Prosocial Tendencies Measure and evaluation on the moral acceptability of behaviors in stories from 790 Chinese adolescents (32.4% boys) were analyzed for the influence of their OXTR single nucleotide polymorphisms (SNPs). Results showed that SNP at site rs2254298 was indirectly associated with prosocial behaviors via moral evaluation of behaviors, and this effect was moderated by gender. Our findings suggest an indirect association between genetic variations in OXTR and prosociality through moral evaluation, indicating the potential pathway from genetic variability to prosociality through level of moral development. We also provide some evidence that the role of oxytocin system may to some extent depend on gender. These findings may promote our understanding of the genetic and biological roots of prosociality and morality.