Genomic and epigenetic evidence for oxytocin receptor deficiency in autism

Oxytocin Receptor Signaling in Vascular Function and Stroke

The oxytocin receptor (OXTR) is a G protein-coupled receptor with a diverse repertoire of intracellular signaling pathways, which are activated in response to binding oxytocin (OXT) and a similar nonapeptide, vasopressin. This review summarizes the cell and molecular biology of the OXTR and its downstream signaling cascades, particularly focusing on the vasoactive functions of OXTR signaling in humans and animal models, as well as the clinical applications of OXTR targeting cerebrovascular accidents.

Mechanisms for the Approach/Avoidance Decision Applied to Autism

As a neurodevelopmental disorder with serious lifelong consequences, autism has received considerable attention from neuroscientists and geneticists. We present a hypothesis of mechanisms plausibly affected during brain development in autism, based on neural pathways that are associated with social behavior and connect the prefrontal cortex (PFC) to the basal ganglia (BG). We consider failure of social approach in autism as a special case of imbalance in the fundamental dichotomy between behavioral approach and avoidance. Differential combinations of genes mutated, differences in the timing of their impact during development, and graded degrees of hormonal influences may help explain the heterogeneity in symptomatology in autism and predominance in boys.

Social Cognition in a Research Domain Criteria Perspective: A Bridge Between Schizophrenia and Autism Spectra Disorders

Schizophrenia and autism spectra disorders are currently conceptualized as distinct clinical categories. However, the relationship between these two nosological entities has been revisited in recent years due to the evidence that they share some important clinical and neurobiological features, putting into question the nature and the extent of their commonalities and differences. In this respect, some core symptoms that are present in both disorders, such as social cognitive deficits, could be a primary target of investigation. This review briefly summarizes the commonalities and overlapping features between schizophrenia and autism spectra disorders in social cognitive functions, considering this construct in a Research Domain Criteria perspective. The clinical manifestation of deficits in social cognition are similar in schizophrenia spectrum disorders and autism spectrum disorders, and brain areas that appear to be altered in relation to these impairments are largely shared; however, the results of various studies suggest that, in some cases, the qualitative nature of these alterations may be different in the two spectra. Moreover, relevant differences could be present at the level of brain networks and connections. More research is required in this field, regarding molecular and genetic aspects of both spectra, to better define the neurobiological mechanisms involved in social cognition deficits, with the objective of developing specific and targeted treatments.

Epigenetic tuning of brain signal entropy in emergent human social behavior

BACKGROUND

How the brain develops accurate models of the external world and generates appropriate behavioral responses is a vital question of widespread multidisciplinary interest. It is increasingly understood that brain signal variability-posited to enhance perception, facilitate flexible cognitive representations, and improve behavioral outcomes-plays an important role in neural and cognitive development. The ability to perceive, interpret, and respond to complex and dynamic social information is particularly critical for the development of adaptive learning and behavior. Social perception relies on oxytocin-regulated neural networks that emerge early in development.

METHODS

We tested the hypothesis that individual differences in the endogenous oxytocinergic system early in life may influence social behavioral outcomes by regulating variability in brain signaling during social perception. In study 1, 55 infants provided a saliva sample at 5 months of age for analysis of individual differences in the oxytocinergic system and underwent electroencephalography (EEG) while listening to human vocalizations at 8 months of age for the assessment of brain signal variability. Infant behavior was assessed via parental report. In study 2, 60 infants provided a saliva sample and underwent EEG while viewing faces and objects and listening to human speech and water sounds at 4 months of age. Infant behavior was assessed via parental report and eye tracking.

RESULTS

We show in two independent infant samples that increased brain signal entropy during social perception is in part explained by an epigenetic modification to the oxytocin receptor gene (OXTR) and accounts for significant individual differences in social behavior in the first year of life. These results are measure-, context-, and modality-specific: entropy, not standard deviation, links OXTR methylation and infant behavior; entropy evoked during social perception specifically explains social behavior only; and only entropy evoked during social auditory perception predicts infant vocalization behavior.

CONCLUSIONS

Demonstrating these associations in infancy is critical for elucidating the neurobiological mechanisms accounting for individual differences in cognition and behavior relevant to neurodevelopmental disorders. Our results suggest that an epigenetic modification to the oxytocin receptor gene and brain signal entropy are useful indicators of social development and may hold potential diagnostic, therapeutic, and prognostic value.

Pathways linking childhood trauma to rural, unmarried, African American father involvement through oxytocin receptor gene methylation

Father involvement contributes uniquely to children's developmental outcomes. The antecedents of father involvement among unmarried, African American fathers from rural areas, however, have been largely overlooked. The present study tested a conceptual model linking retrospective reports of childhood trauma and early adulthood social instability to father involvement among unmarried, African American men living in resource-poor, rural communities in the southeastern United States. We hypothesized these factors would influence father involvement indirectly, via DNA methylation of the oxytocin receptor gene (OXTR). A sample of 192 fathers participated in 3 waves of data collection in early adulthood. Fathers reported on social instability at Wave 1; OXTR methylation was assessed via saliva samples at Wave 2; and measures of father involvement, retrospective childhood trauma, and quality of the fathers' relationships with their children's mothers were collected at Wave 3. Structural equation modeling indicated that childhood trauma was related directly to reduced levels of father involvement and to increased social instability. Social instability was associated with elevated levels of OXTR methylation, which in turn predicted decreased father involvement. The indirect effect from social instability to father involvement via OXTR methylation was significant. These associations did not operate through fathers' relationship with the child's mother and remained significant even accounting for associations between interparental relationship quality and father involvement. Findings suggest that OXTR methylation might be a biological mechanism linking social instability to father involvement among unmarried, African American fathers in vulnerable contexts and underscore the detrimental influence of childhood trauma on father involvement. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Rationale, design, and methods of the Autism Centers of Excellence (ACE) network Study of Oxytocin in Autism to improve Reciprocal Social Behaviors (SOARS-B)

OBJECTIVE

To describe the rationale, design, and methods of the Autism Centers of Excellence (ACE) network Study of Oxytocin in Autism to improve Reciprocal Social Behaviors (SOARS-B).

METHOD

This phase 2 clinical trial was designed to evaluate the use of intranasal oxytocin treatment to improve social difficulties in individuals with autism spectrum disorder (ASD). In total, 290 participants ages 3 to 17 years with a DSM-5 diagnosis of ASD were enrolled to receive 24 weeks of treatment with either oxytocin or a matched placebo at one of seven collaborating sites. Participants were subsequently treated with open-label oxytocin for 24 additional weeks. Post-treatment assessments were done approximately 4 weeks after treatment discontinuation. Plasma oxytocin and oxytocin receptor gene (OXTR) methylation level were measured at baseline, and week 8, 24 and 36 to explore potential relationships between these biomarkers and treatment response.

RESULTS

This report describes the rationale, design, and methods of the SOARS-B clinical trial.

CONCLUSIONS

There is a tremendous unmet need for safe and effective pharmacological treatment options that target the core symptoms of ASD. Several studies support the hypothesis that intranasal oxytocin could improve social orienting and the salience of social rewards in ASD, thereby enhancing reciprocal social behaviors. However, due to conflicting results from a number of pilot studies on the prosocial effects of exogenous oxytocin, this hypothesis remains controversial and inconclusive. SOARS-B is the best powered study to date to address this hypothesis and promises to improve our understanding of the safety and efficacy of intranasal oxytocin in the treatment of social deficits in children with ASD.

Pathways linking adverse environments to emerging adults' substance abuse and depressive symptoms: A prospective analysis of rural African American men

For African American emerging adult men, developmental challenges are evident in their escalating substance abuse and depressive symptoms; this is particularly true for men from low-resource communities. The present study tests a developmental model linking childhood adversity and contemporaneous contextual stressors to increases in emerging adults' substance use and depressive symptoms, indirectly, via increases in defensive/hostile relational schemas and social developmental risk factors (e.g., risky peers and romantic partners, lack of involvement in school or work). We also advance exploratory hypotheses regarding DNA methylation in the oxytocin receptor gene (OXTR) as a moderator of the effects of stress on relational schemas. Hypotheses were tested with three waves of data from 505 rural African American men aged 19-25 years. Adverse childhood experiences predicted exposure to emerging adult contextual stressors. Contextual stressors forecast increases in defensive/hostile relational schemas, which increased social developmental risk factors. Social developmental risk factors proximally predicted increases in substance abuse and depressive symptoms. OXTR DNA methylation moderated the effects of contextual stressors on defensive/hostile relational schemas. Findings suggest that early exposures to stress carry forward to affect the development of social developmental risk factors in emerging adulthood, which place rural African American men at risk for increased substance abuse and depressive symptoms during the emerging adult years.

Intranasal oxytocin modulates brain responses to voice-identity recognition in typically developing individuals, but not in ASD

Faces and voices are prominent cues for person-identity recognition. Face recognition behavior and associated brain responses can be enhanced by intranasal administration of oxytocin. It is unknown whether oxytocin can also augment voice-identity recognition mechanisms. To find it out is particularly relevant for individuals who have difficulties recognizing voice identity such as individuals diagnosed with autism spectrum disorder (ASD). We conducted a combined behavioral and functional magnetic resonance imaging (fMRI) study to investigate voice-identity recognition following intranasal administration of oxytocin or placebo in a group of adults diagnosed with ASD (full-scale intelligence quotient > 85) and pairwise-matched typically developing (TD) controls. A single dose of 24 IU oxytocin was administered in a randomized, double-blind, placebo-controlled and cross-over design. In the control group, but not in the ASD group, administration of oxytocin compared to placebo increased responses to recognition of voice identity in contrast to speech in the right posterior superior temporal sulcus/gyrus (pSTS/G) - a region implicated in the perceptual analysis of voice-identity information. In the ASD group, the right pSTS/G responses were positively correlated with voice-identity recognition accuracy in the oxytocin condition, but not in the placebo condition. Oxytocin did not improve voice-identity recognition performance at the group level. The ASD compared to the control group had lower right pSTS/G responses to voice-identity recognition. Since ASD is known to have atypical pSTS/G, the results indicate that the potential of intranasal oxytocin to enhance mechanisms for voice-identity recognition might be variable and dependent on the functional integrity of this brain region.

Reduced DNA methylation of the oxytocin receptor gene is associated with obsessive-compulsive disorder

Background

Oxytocin is an important neuromodulator involved in cognition and socio-emotional processing that exerts its central activities via oxytocin receptors. Epigenetic alterations in the oxytocin receptor gene (OXTR) may be a molecular mechanism in the pathogenesis of obsessive-compulsive disorder (OCD). This study investigated the association between OXTR DNA methylation and the OCD status of a Korean population.

Results

Quantitative leukocyte DNA methylation levels of three cytosine-phosphate-guanine (CpG) sites in the 5′ untranslated region (UTR) of OXTR exon 2 and eight CpG sites within OXTR exon 3 were analyzed using the pyrosequencing method in 151 patients with OCD (including 45 drug-naïve patients) and 108 healthy controls. DNA methylation levels were compared between the groups using multiple analyses of covariance separately by sex after controlling for age and educational level. Patients with OCD showed significantly lower methylation levels at CpG1 and CpG2 sites on the UTR of OXTR exon 2 than those of healthy controls for both sexes. In a subset of 45 drug-naïve patients with OCD, the DNA methylation levels also remained significantly lower than those in the controls and their CpG1 methylation levels were significantly negatively associated with the ordering symptom dimension.

Conclusions

Our findings suggest that epigenetic OXTR alterations may affect the pathophysiology of OCD. The potential role of the oxytocin system in OCD development and treatment warrants further investigation.

Epigenetic modification of the oxytocin receptor gene: implications for autism symptom severity and brain functional connectivity

The role of oxytocin in social cognition has attracted tremendous interest in social neuroscience and psychiatry. Some studies have reported improvement in social symptoms following oxytocin treatment in autism spectrum disorders (ASD), while others point to endogenous factors influencing its efficiency and to mixed results in terms of long-term clinical benefits. Epigenetic modification to the oxytocin receptor gene (OXTR) in ASD could be an informative biomarker of treatment efficacy. Yet, little is known about the relationship between OXTR methylation, clinical severity, and brain function in ASD. Here, we investigated the relationship between OXTR methylation, ASD diagnosis (in N = 35 ASD and N = 64 neurotypical group), measures of social responsiveness, and resting-state functional connectivity (rsFC) between areas involved in social cognition and reward processing (in a subset of ASD, N = 30). Adults with ASD showed higher OXTR methylation levels in the intron 1 area compared with neurotypical subjects. This hypermethylation was related to clinical symptoms and to a hypoconnectivity between cortico-cortical areas involved in theory of mind. Methylation at a CpG site in the exon 1 area was positively related to social responsiveness deficits in ASD and to a hyperconnectivity between striatal and cortical brain areas. Taken together, these findings provide initial evidence for OXTR hypermethylation in the intron area as a potential biomarker for adults with ASD with less severe developmental communication deficits, but with impairments in theory of mind and self-awareness. Also, OXTR methylation in the exon 1 area could be a potential biomarker of sociability sensitive to life experiences.

DNA methylation and brain structure and function across the life course: A systematic review

MRI has enhanced our capacity to understand variations in brain structure and function conferred by the genome. We identified 60 studies that report associations between DNA methylation (DNAm) and human brain structure/function. Forty-three studies measured candidate loci DNAm; seventeen measured epigenome-wide DNAm. MRI features included region-of-interest and whole-brain structural, diffusion and functional imaging features. The studies report DNAm-MRI associations for: neurodevelopment and neurodevelopmental disorders; major depression and suicidality; alcohol use disorder; schizophrenia and psychosis; ageing, stroke, ataxia and neurodegeneration; post-traumatic stress disorder; and socio-emotional processing. Consistency between MRI features and differential DNAm is modest. Sources of bias: variable inclusion of comparator groups; different surrogate tissues used; variation in DNAm measurement methods; lack of control for genotype and cell-type composition; and variations in image processing. Knowledge of MRI features associated with differential DNAm may improve understanding of the role of DNAm in brain health and disease, but caution is required because conventions for linking DNAm and MRI data are not established, and clinical and methodological heterogeneity in existing literature is substantial.

The early overgrowth theory of autism spectrum disorder: Insight into convergent mechanisms from valproic acid exposure and translational models

The development of new approaches for the clinical management of autism spectrum disorder (ASD) can only be realized through a better understanding of the neurobiological changes associated with ASD. One strategy for gaining deeper insight into the neurobiological mechanisms associated with ASD is to identify converging pathogenic processes associated with human idiopathic clinicopathology that are conserved in translational models of ASD. In this chapter, we first present the early overgrowth theory of ASD. Second, we introduce valproic acid (VPA), one of the most robust and well-known environmental risk factors associated with ASD, and we summarize the rapidly growing body of animal research literature using VPA as an ASD translational model. Lastly, we will detail the mechanisms of action of VPA and its impact on functional neural systems, as well as discuss future research directions that could have a lasting impact on the field.

Dysregulation of the oxytocin receptor gene in Williams syndrome

Williams syndrome (WS) is caused by a microdeletion of chromosome 7q11.23, and is characterized by various physical and cognitive symptoms. In particular, WS is characterized by hypersocial (overfriendly) behavior; WS has gained attention as aspects of the WS phenotype contrast with those of autism spectrum disorder (ASD). The oxytocin receptor gene (OXTR) contributes to social phenotypes in relation to regulation of oxytocin (OXT) secretion. Additionally, mounting evidence has recently shown that DNA methylation of OXTR is associated with human social behavior. However, the role of OXTR in WS remains unclear. This study investigated the regulation of OXTR in WS. We examined the gene expression levels in blood from WS patients and controls, and then analyzed the methylation levels in two independent cohorts. We showed that OXTR was down-regulated and hypermethylated in WS patients compared to controls. Our findings may provide an insight into OXTR in mediating complex social phenotypes in WS.

Genetic and Epigenetic Etiology Underlying Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder characterized by difficulties in social interaction, language development delays, repeated body movements, and markedly deteriorated activities and interests. Environmental factors, such as viral infection, parental age, and zinc deficiency, can be plausible contributors to ASD susceptibility. As ASD is highly heritable, genetic risk factors involved in neurodevelopment, neural communication, and social interaction provide important clues in explaining the etiology of ASD. Accumulated evidence also shows an important role of epigenetic factors, such as DNA methylation, histone modification, and noncoding RNA, in ASD etiology. In this review, we compiled the research published to date and described the genetic and epigenetic epidemiology together with environmental risk factors underlying the etiology of the different phenotypes of ASD.

Epigenomic Convergence of Neural-Immune Risk Factors in Neurodevelopmental Disorder Cortex

Neurodevelopmental disorders (NDDs) affect 7-14% of all children in developed countries and are one of the leading causes of lifelong disability. Epigenetic modifications are poised at the interface between genes and environment and are predicted to reveal insight into NDD etiology. Whole-genome bisulfite sequencing was used to examine DNA cytosine methylation in 49 human cortex samples from 3 different NDDs (autism spectrum disorder, Rett syndrome, and Dup15q syndrome) and matched controls. Integration of methylation changes across NDDs with relevant genomic and genetic datasets revealed differentially methylated regions (DMRs) unique to each type of NDD but with shared regulatory functions in neurons and microglia. NDD DMRs were enriched within promoter regions and for transcription factor binding sites with identified methylation sensitivity. DMRs from all 3 disorders were enriched for ontologies related to nervous system development and genes with disrupted expression in brain from neurodevelopmental or neuropsychiatric disorders. Genes associated with NDD DMRs showed expression patterns indicating an important role for altered microglial function during brain development. These findings demonstrate an NDD epigenomic signature in human cortex that will aid in defining therapeutic targets and early biomarkers at the interface of genetic and environmental NDD risk factors.

Attenuated relationship between salivary oxytocin levels and attention to social information in adolescents and adults with autism spectrum disorder: a comparative study

BACKGROUND

Previous research studies have assessed the relationship between attention to social information and peripheral (e.g., plasma and salivary) oxytocin (OT) levels in typically developing (TD) children and children with autism spectrum disorder (ASD). A relationship between them was observed in TD children, but not in children with ASD. However, this relationship remains unexamined in other age groups. To clarify whether this lack of association is maintained throughout development in individuals with ASD, we aimed to assess the relationship between salivary OT levels and attention to social information in adolescents and adults with and without ASD.

METHODS

We recruited male adolescents and adults with ASD (n = 17) and TD participants (n = 24). Using the all-in-one eye-tracking system Gazefinder, we measured the percentage fixation time allocated to social information. We also measured the salivary OT levels and Autism Spectrum Quotient (AQ) of participants. Subsequently, we confirmed group differences and conducted a correlation analysis to investigate the relationships between these three measures.

RESULTS

Salivary OT levels did not show any significant difference between the ASD and TD groups and were negatively correlated with the AQ in the whole-group analysis, but not in within-group analysis. Individuals with ASD had significantly lower percentage fixation times than did TD individuals for eye regions in human faces with/without mouth motion, for upright biological motion, and for people regions in the people and geometry movies. The percentage of fixation for geometric shapes in the people and geometry movies was significantly higher in the ASD than in the TD group. In the TD group, salivary OT levels were positively correlated with percentage fixation times for upright biological motion and people and negatively correlated with inverted biological motion and geometry. However, no significant correlations were found in the ASD group.

CONCLUSIONS

Our exploratory results suggest that salivary OT levels in adolescents and adults with ASD are less indicative of attention to social stimuli than they are in TD adolescents and adults. It is suggested that their association is slightly weaker in adolescents and adults with ASD and that this attenuated relationship appears to be maintained throughout development.

FOXP2 and language alterations in psychiatric pathology

Background. From the first reports of the linguist Noam Chomsky it has become clear that the development of language has an important genetic component. Several reports in families have shown the relationship between language disorders and genetic polymorphisms. The FOXP2 gene has been a fundamental piece for the understanding of language development. This gene codes for a transcription factor containing a forkhead domain of DNA binding and participates in the regulation of the expression of a large number of genes involved in the embryonic development of fundamental neuronal structures needed for the development of speech and language. Objective. To present an updated view of the relationship between FOXP2 and language alterations in psychiatric pathology. Method. Narrative review of information reported in databases on the recent advances supporting genetic participation in language disorders of psychiatric illness. Results. Update of content related to FOXP2 and its participation in language alterations in psychiatric diseases. Discussion and conclusion. Advances in the genetic study of language disorders in psychiatric pathology open up new avenues of investigation that allow us to explore how language emerged and how it evolved, as well as to carry out comparative studies on the structure and functioning of genes to approach the understanding of this complex characteristic that makes us human.

Mathematical Models for Possible Roles of Oxytocin and Oxytocin Receptors in Autism

This paper develops mathematical models examining possible roles of oxytocin and oxytocin receptors in the development of autism. This is done by demonstrating that mathematical operations on normalized data from the Stanford study, which establishes a correspondence between severity of autism in children and their oxytocin blood levels, generate a graph that is the same as the graph of mathematical operations on a normalized theoretical model for the severity of autism. This procedure establishes the validity of the theoretical model and the significance of oxytocin receptors in autism. A steady-state model follows, explaining the constant baseline concentrations of oxytocin observed in the cerebral spinal fluid and blood in terms of the neuromodulation by oxytocin of oxytocin receptors on the magnocellular neurons that produce oxytocin in nuclei in the hypothalamus. The implications of these models for possible roles of oxytocin and oxytocin receptors in autism are considered for several unrelated conditions that may be associated with autism. These are oxytocin receptor desensitization and downregulation as factors during labor in offspring autism development; reductions in the oxytocin receptor numbers in the fixed oxytocin receptor expression that occurs before birth; MAST Immune System disease; and the excess number of dendritic spines from lack of pruning observed in brains of autistic people. Research into the feasibility of generating magnocellular neurons and other neurons from adult stem cells is suggested as a way of doing in vitro studies of oxytocin and oxytocin receptors to assess the validity of theories presented in this paper.

Methylation of the OXTR gene in women with anorexia nervosa: Relationship to social behavior

DNA methylation allows for the environmental regulation of gene expression and is believed to link environmental stressors to psychiatric disorder phenotypes, such as anorexia nervosa (AN). The oxytocin receptor (OXTR) gene is epigenetically regulated, and studies have shown associations between OXTR and social behaviours in various samples, including women with AN. The present study examined differential levels of methylation at various CG sites of the OXTR gene in 69 women with active AN (AN-Active), 21 in whom AN was in remission (AN-Rem) and 35 with no eating disorder (NED). Within each group, we explored the correlation between methylation and measures of social behaviour such as insecure attachment and social avoidance. Hypermethylation of a number of CG sites was seen in AN-Active participants as compared with AN-Rem and NED participants. In the AN-Rem sample, methylation at CG27501759 was significantly positively correlated with insecure attachment (r = .614, p = .003, permutation Q = 0.008) and social avoidance (r = .588, p = .005, permutation Q = 0.0184). Our results highlight differential methylation of the OXTR gene among women with AN, those in remission from AN, and those who never had AN and provide some evidence of associations between OXTR methylation and social behaviour in women remitted from AN.

DNA Methylation and Susceptibility to Autism Spectrum Disorder

The prevalence of autism spectrum disorder (ASD) has been increasing steadily over the last 20 years; however, the molecular basis for the majority of ASD cases remains unknown. Recent advances in next-generation sequencing and detection of DNA modifications have made methylation-dependent regulation of transcription an attractive hypothesis for being a causative factor in ASD etiology. Evidence for abnormal DNA methylation in ASD can be seen on multiple levels, from genetic mutations in epigenetic machinery to loci-specific and genome-wide changes in DNA methylation. Epimutations in DNA methylation can be acquired throughout life, as global DNA methylation reprogramming is dynamic during embryonic development and the early postnatal period that corresponds to the peak time of synaptogenesis. However, technical advances and causative evidence still need to be established before abnormal DNA methylation and ASD can be confidently associated.

Oxytocin receptor DNA methylation and alterations of brain volumes in maltreated children

Although oxytocin (OXT) plays an important role in secure attachment formation with a primary caregiver, which is impaired in many children with childhood maltreatment (CM), epigenetic regulation in response to CM is a key factor in brain development during childhood. To address this issue, we first investigated differences in salivary DNA methylation of the oxytocin receptor (OXTR) between CM and Non-CM groups of Japanese children (CM: n = 44; Non-CM: n = 41) and its impact on brain structures in subgroup analysis using brain imaging and full clinical data (CM: n = 24; Non-CM: n = 31). As a result, we observed that the CM group showed higher CpG 5,6 methylation than did the Non-CM group and confirmed negative correlations of gray matter volume (GMV) in the left orbitofrontal cortex (OFC) with CpG 5,6 methylation. In addition, the CM group showed significantly lower GMV in the left OFC than did the Non-CM group. Furthermore, as a result of examining the relationship between GMV in the left OFC and psychiatric symptoms in CM, we observed a negative association with insecure attachment style and also confirmed the mediation effect of left-OFC GMV reduction on the relationship between OXTR methylation and insecure attachment style. These results suggest that any modulation of the oxytocin signaling pathway induced by OXTR hypermethylation at CpG 5,6 leads to atypical development of the left OFC, resulting in distorted attachment formation in children with CM.

Reduced DNA Methylation of the Oxytocin Receptor Gene Is Associated With Anhedonia-Asociality in Women With Recent-Onset Schizophrenia and Ultra-high Risk for Psychosis

Negative symptoms are recognized as a fundamental feature of schizophrenia throughout the disease course. Epigenetic alterations in the oxytocin receptor gene (OXTR) may be a key mechanism involved in social-emotional disturbances of schizophrenia. Here, we investigated OXTR methylation and its association with clinical and brain network connectivity phenotypes of negative symptoms, particularly anhedonia-asociality, in individuals with recent-onset schizophrenia (ROS) and at ultrahigh risk (UHR) for psychosis. Sixty-four ROS (39 women), 46 UHR (19 women), and 98 healthy individuals (52 women) participated in this study. OXTR methylation was quantified using the pyrosequencing method. A subset of participants (16 ROS, 23 UHR, and 33 healthy controls [HCs]) underwent a 5.5-minute resting-state functional magnetic resonance imaging to determine the relationship between OXTR methylation and the striatal-amygdala network functional connectivity (FC) underlying anhedonia-asociality. Both men and women with ROS and UHR showed significantly decreased OXTR methylation compared to HCs. In women with ROS and UHR, decreased OXTR methylation showed a significant correlation with increased anhedonia-asociality. FC of the striatal-amygdala network, positively associated with the severity of anhedonia-asociality, showed an inverse correlation with OXTR methylation. This study suggests that epigenetic alterations of OXTR, which can be detected before the development of full-blown psychosis, confer susceptibility to schizophrenia and play a crucial role in the manifestation of anhedonia-asociality, particularly in women.

Epigenetic dynamics in infancy and the impact of maternal engagement

The contribution of nature versus nurture to the development of human behavior has been debated for centuries. Here, we offer a piece to this complex puzzle by identifying the human endogenous oxytocin system-known for its critical role in mammalian sociality-as a system sensitive to its early environment and subject to epigenetic change. Recent animal work suggests that early parental care is associated with changes in DNA methylation of conserved regulatory sites within the oxytocin receptor gene (OXTRm). Through dyadic modeling of behavior and OXTRm status across the first year and a half of life, we translated these findings to 101 human mother-infant dyads. We show that OXTRm is dynamic in infancy and its change is predicted by maternal engagement and reflective of behavioral temperament. We provide evidence for an early window of environmental epigenetic regulation of the oxytocin system, facilitating the emergence of individual differences in human behavior.

Interaction between polymorphisms of the oxytocinergic system genes and emotion perception in inpatients with anorexia nervosa

OBJECTIVE

The empirical literature describes the role of the oxytocinergic system in emotion perception (EP). Variants in the oxytocin (OXT) and oxytocin receptor genes have been associated with mental disorders, including anorexia nervosa (AN), that are characterized by difficulties in socioemotional functioning. Our study aimed to examine whether variability within the genes related to OXT pathways may play a role in facial EP in inpatients with AN.

METHOD

Single nucleotide polymorphisms (SNPs) of the following genes: oxytocin receptor (rs2254298, rs53576), OXT (rs6133010), OXT-arginine-vasopressin (rs2740204), CD38 (rs6449197, rs3796863), and human leucyl/cystinylaminopeptidase (rs4869317) were genotyped in 60 AN female inpatients and 60 healthy control females (HCs). Associations between genetic polymorphisms and EP as well as clinical symptoms were examined.

RESULTS

The AN group showed decreased EP abilities compared with HCs. SNPs of rs2740204, rs6133010, and rs53576 were associated with differences in EP in women with AN and in HCs. The SNP of rs4869317 was associated with the level of eating disorders symptoms in HCs.

CONCLUSIONS

The OXT system may be involved in EP difficulties in AN. SNPs within genes related to OXT pathways may influence EP abilities. The leucyl/cystinylaminopeptidase rs4869317 SNP may be involved in the development of eating disorders psychopathology.

Association of oxytocin levels and oxytocin receptor gene polymorphism (rs2254298) with cardiovascular risk factors in Brazilian elderly from Primary Health Care

BACKGROUND

Morbidity and mortality from cardiovascular disease is a typical phenomenon in the elderly, and are related to unfavorable genetic, hormonal and environmental (lifestyle) interactions. In this context, oxytocin (OT) seems plays a key role in the development of CVD by performing important actions in metabolism energy and hemodynamic variables.

OBJECTIVE

To verify if there is an association between (OT) levels and the oxytocin receptor gene (OXTR) polymorphism (rs2254298) with cardiovascular risk factors (CRF) in the elderly.

METHODS

This was a cross-sectional study in community-dwelling elderly attending primary health care. The genotyping was done using the polymerase chain reaction technique. The CRF factors investigated included hypertension, diabetes mellitus, dyslipidemia, sedentary lifestyle, and obesity. Levels of triglycerides (TGC) postprandial and glucose were measured in capillary blood. OT and cortisol levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The sample comprised 177 elderly individuals. OT levels showed a significant negative correlation with postprandial triglycerides (p = 0.030) and BMI (p = 0.019). OT levels were also associated with leanness (p = 0.005). On Poisson regression analysis, OT remained a predictor for leanness (p = 0.010). No significant associations were observed between the OXTR polymorphism and CRF.

CONCLUSION

The results suggest that Postprandial TGC levels are increased, while OT levels are decreased, and this hormone was significantly elevated in lean elderly. Future studies are needed to confirm these findings, and the role of OT in metabolic parameters.

Vasopressin in the Amelioration of Social Functioning in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a developmental disability described by diagnostic criteria that comprise deficits in social communication and the existence of repetitive, restricted patterns of behavior, interests, or activities that can last throughout life. Many preclinical studies show the importance of arginine vasopressin (AVP) physiology in social functioning in several mammalian species. Currently, there is a trend to investigate more specific pharmacological agents to improve social functioning in patients with ASD. Neurobiological systems that are crucial for social functioning are the most encouraging conceivable signaling pathways for ASD therapeutic discovery. The AVP signaling pathway is one of the most promising. The purpose of this commentary is to detail the evidence on the use of AVP as an agent that can improve social functioning. The pharmacologic aspects of the drug as well as its potential to ameliorate social functioning characteristics in human and animal studies are described in this manuscript. AVP, especially in its inhaled form, seems to be safe and beneficial in improving social functioning including in children with autism. Larger randomized studies are required to implement a long awaited safe and feasible treatment in people with a deficiency in social functioning.

Childhood Adversity, Socioeconomic Instability, Oxytocin-Receptor-Gene Methylation, and Romantic-Relationship Support Among Young African American Men

Men's emerging adult romantic relationships forecast downstream relationship behavior, including commitment and quality. Accumulating evidence implicates methylation of the oxytocin-receptor-gene (OXTR) system in regulating relationship behavior. We tested hypotheses regarding the links between (a) childhood adversity and (b) socioeconomic instability in emerging adulthood on supportive romantic relationships via their associations with OXTR methylation. Hypotheses were tested using path analysis with data from 309 participants in the African American Men's Project. Consistent with our hypotheses, results showed that OXTR methylation proximally predicted changes in relationship support during a 1.5-year period. Childhood adversity was not directly associated with OXTR methylation but, rather, with contemporaneous socioeconomic instability, which in turn predicted elevated OXTR methylation. Findings suggest that early adversity is indirectly associated with OXTR methylation by links with downstream socioeconomic instability. Findings must be considered provisional, however, because preregistered replications are needed to establish more firmly the relations among these variables.

A Mathematical Model Relating Pitocin Use during Labor with Offspring Autism Development in terms of Oxytocin Receptor Desensitization in the Fetal Brain

This paper develops a mathematical model describing the potential buildup of high oxytocin concentrations in the maternal circulation during labor in terms of continuous Pitocin infusion rate, half-life, and maternal weight. Oxytocin override of the degradation of oxytocin by placental oxytocinase is introduced to model the potential transfer of oxytocin from the maternal circulation across the placenta into the fetal circulation and from there into the brain of the fetus. The desensitization unit D equal to 1.8E6 (pg·min)/ml is employed to establish a desensitization threshold and by extension, a downregulation threshold as a function of oxytocin override concentration and continuous Pitocin infusion time, that could be a factor in the subsequent development of autism among offspring. Epidemiological studies by Duke University [1], Yale University [2], and Harvard University [3] are discussed regarding Pitocin use and offspring autism development for an explanation of the weak correlations they identified. The findings of the Harvard epidemiological study are reinterpreted regarding Pitocin use and its conclusion questioned. Further evaluations of the findings of these three epidemiological studies are called for to incorporate medical information on quantity of Pitocin used, continuous Pitocin infusion rate, length of labor, and maternal weight to determine if a correlation can be established with offspring autism development above an empirically determined desensitization threshold for Pitocin use. Suggestions for research are discussed, including an alternative to continuous Pitocin infusion, pulsatile infusion of Pitocin during labor induction, which may mitigate possible offspring autism development.

Oxytocin alleviates cellular senescence through oxytocin receptor-mediated extracellular signal-regulated kinase/Nrf2 signalling

BACKGROUND

Oxytocin (OT) is a neuropeptide hormone that has many beneficial biological effects, including protection against age-related disorders. However, less is known about its role in intrinsic skin ageing, which is accelerated by an increase in senescent cell fraction in skin tissue.

OBJECTIVES

To investigate the novel function and the underlying mechanism of OT in preventing cellular senescence in normal human dermal fibroblasts (NHDFs) isolated from the skin of female donors of different ages.

METHODS

NHDFs from young and old donors were exposed to conditioned medium from senescent or control NHDFs in the presence or absence of 10 nmol L^-1 OT for 3 days, and were continuously subcultured for 12 days. Subsequently, various age-associated signs of senescence including decreased proliferation rate, elevated p16 and p21 levels, and positivity for senescence-associated β-galactosidase expression were examined.

RESULTS

We found that OT suppressed senescence-associated secretory phenotype-induced senescence in NHDFs, and its effect depended on the age of the donor's NHDFs. The inhibitory effects of OT required signalling by OT receptor-mediated extracellular signal-regulated kinase/Nrf2 (nuclear factor erythroid 2-related factor 2). The age-dependent antisenescence effects of OT are closely related to hypermethylation of the OT receptor gene (OXTR).

CONCLUSIONS

Our findings bring to light the role of OT in the prevention of skin ageing, which might allow development of new clinical strategies. What's already known about this topic? Senescent keratinocytes and fibroblasts accumulate with age in the skin and contribute to the loss of skin function and integrity during ageing. Senescent cells secrete senescence-associated secretory phenotype (SASP), which includes the release of proinflammatory cytokines such as interleukin (IL)-6 and IL-1, chemokines, extracellular matrix-remodelling proteases and growth factors. The neuropeptide oxytocin (OT) and its receptor (OXTR) have protective effects against various age-related disorders. What does this study add? OT suppressed SASP-induced cellular senescence in normal human dermal fibroblasts (NHDFs), depending on the age of the NHDFs' donor. The inhibitory effects of OT on cellular senescence required OXTR-mediated phosphorylation of extracellular signal-regulated kinase, which enhanced nuclear localization of Nrf2, a vital factor in the antioxidant defence system. The age-specific antisenescent effects of OT were closely related to hypermethylation of OXTR. What is the translational message? Our results suggest that OT and OXTR agonists could be clinically promising agents for the improvement of age-associated skin ageing, especially in women.

Toward a transdiagnostic model of common and unique processes leading to the major disorders of childhood: The REAL model of attention, responsiveness and learning

There is a growing recognition of the importance of identifying both trans-diagnostic risk factors across the major disorders that onset early in childhood, as well as precise vulnerabilities that differentiate among specific disorders. In this paper, we propose a model to explain individual differences in the development of the major forms of mental health problems that can be identified early in life through excesses and deficits in emotional attention, responsiveness and learning (i.e., the REAL model). The model leads to a number of specific hypotheses relating to trans-diagnostic (common to all disorders) and specific risk to the major mental disorders of childhood. Like earlier models of temperament, the REAL constructs are defined in terms of how the child responds to environmental conditions. Our proposal is that the development of psychopathology is in part based on how adverse environmental conditions trigger, inhibit, and interact with these specific biological vulnerabilities at sensitive periods in the developing human. To illustrate this interplay of biology and experience, we summarize key findings from the growing field of epigenetics and child mental health, arguing that epigenetic processes might mediate the relationship between environmental adversity and the major neurodevelopmental systems of REAL. Finally, we argued that the REAL model highlights important avenues for early intervention based on common and unique factors across childhood disorders.

Epigenetic Regulation of the Social Brain

Social behavior, a highly adaptive and crucial component of mammalian life, is regulated by particularly sensitive regulatory brain mechanisms. Substantial evidence implicates classical epigenetic mechanisms including histone modifications, DNA methylation, and nucleosome remodeling as well as nonclassical mechanisms mediated by noncoding RNA in the regulation of social behavior. These mechanisms collectively form the 'epigenetic network' that orchestrates genomic integration of salient and transient social experiences. Consequently, its dysregulation has been linked to behavioral deficits and psychopathologies. This review focuses on the role of the epigenetic network in regulating the enduring effects of social experiences during early-life, adolescence, and adulthood. We discuss research in animal models, primarily rodents, and associations between dysregulation of epigenetic mechanisms and human psychopathologies, specifically autism spectrum disorder (ASD) and schizophrenia.

A randomized placebo-controlled pilot trial shows that intranasal vasopressin improves social deficits in children with autism

The social impairments of autism spectrum disorder (ASD) have a major impact on quality of life, yet there are no medications that effectively treat these core social behavior deficits. Preclinical research suggests that arginine vasopressin (AVP), a neuropeptide involved in promoting mammalian social behaviors, may be a possible treatment for ASD. Using a double-blind, randomized, placebo-controlled, parallel study design, we tested the efficacy and tolerability of a 4-week intranasal AVP daily treatment in 30 children with ASD. AVP-treated participants aged 6 to 9.5 years received the maximum daily target dose of 24 International Units (IU); participants aged 9.6 to 12.9 years received the maximum daily target dose of 32 IU. Intranasal AVP treatment compared to placebo enhanced social abilities as assessed by change from baseline in this phase 2 trial's primary outcome measure, the Social Responsiveness Scale, 2nd Edition total score (SRS-2 T score; F _1,20 = 9.853; P = 0.0052; η_p ² = 33.0%; Cohen's d = 1.40). AVP treatment also diminished anxiety symptoms and some repetitive behaviors. Most of these findings were more pronounced when we accounted for pretreatment AVP concentrations in blood. AVP was well tolerated with minimal side effects. No AVP-treated participants dropped out of the trial, and there were no differences in the rate of adverse events reported between treatment conditions. Last, no changes from baseline were observed in vital signs, electrocardiogram tracings, height and body weight, or clinical chemistry measurements after 4 weeks of AVP treatment. These preliminary findings suggest that AVP has potential for treating social impairments in children with ASD.

The interaction between oxytocin receptor gene methylation and maternal behavior on children's early theory of mind abilities

Theory of mind, the ability to represent the mental states of others, is an important social cognitive process, which contributes to the development of social competence. Recent research suggests that interactions between gene and environmental factors, such as oxytocin receptor gene (OXTR) polymorphisms and maternal parenting behavior, may underlie individual differences in children's theory of mind. However, the potential influence of DNA methylation of OXTR remains unclear. The current study investigated the roles of OXTR methylation, maternal behavior, and their statistical interaction on toddlers' early emerging theory of mind abilities. Participants included a community sample of 189 dyads of mothers and their 2- to 3-year-old children, whose salivary DNA was analyzed. Results indicated that more maternal structuring behavior was associated with better performance, on a battery of three theory of mind tasks, while higher OXTR methylation within exon 3 was associated with poorer performance. A significant interaction also emerged, such that OXTR methylation was related to theory of mind among children whose mothers displayed less structuring, when controlling for children's age, sex, ethnicity, number of child-aged siblings, verbal ability, and maternal education. Maternal structuring behavior may buffer the potential negative impact of hypermethylation on OXTR gene expression and function.

Epigenetic modification of the oxytocin receptor gene is associated with emotion processing in the infant brain

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First developmental neuroimaging epigenetics study with human infants.

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Oxytocin receptor gene methylation (OXTRm) assessed in a large sample of infants.

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OXTRm predicts inferior frontal brain responses to emotional faces using fNIRS.

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Higher OXTRm linked to enhanced brain responses to angry and fearful faces.

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OXTRm contributes to variability in social brain function early in ontogeny.

The neural capacity to discriminate between emotions emerges early in development, though little is known about specific factors that contribute to variability in this vital skill during infancy. In adults, DNA methylation of the oxytocin receptor gene (OXTRm) is an epigenetic modification that is variable, predictive of gene expression, and has been linked to autism spectrum disorder and the neural response to social cues. It is unknown whether OXTRm is variable in infants, and whether it is predictive of early social function. Implementing a developmental neuroimaging epigenetics approach in a large sample of infants (N = 98), we examined whether OXTRm is associated with neural responses to emotional expressions. OXTRm was assessed at 5 months of age. At 7 months of age, infants viewed happy, angry, and fearful faces while functional near-infrared spectroscopy was recorded. We observed that OXTRm shows considerable variability among infants. Critically, infants with higher OXTRm show enhanced responses to anger and fear and attenuated responses to happiness in right inferior frontal cortex, a region implicated in emotion processing through action-perception coupling. Findings support models emphasizing oxytocin’s role in modulating neural response to emotion and identify OXTRm as an epigenetic mark contributing to early brain function.

DNA methylation of OXTR is associated with parasympathetic nervous system activity and amygdala morphology

Oxytocin has anxiolytic properties whose mechanisms of action are still being identified. DNA methylation in the promoter region of the oxytocin receptor gene (OXTR), an epigenetic modification that putatively reflects a downtuning of the oxytocin system, has previously been implicated in the regulation of fear-related responses through the amygdala. In this study, we attempted to characterize the relationship between methylation of OXTR and anxiogenesis using two distinct endophenotypes: autonomic nervous system activity and subcortical brain structure. In 79 participants, we found that increased OXTR methylation is associated with attenuated resting parasympathetic tone, measured using high-frequency heart rate variability. Further, we found that this relationship is mediated by brain morphology, such that OXTR methylation is associated with increased gray matter of the central amygdala which is, in turn, associated with decreased parasympathetic tone. These results further our understanding of epigenetic regulation of the human oxytocin system and its role in anxiogenesis.

Assessing risk of neurodevelopmental disorders after birth with oxytocin: a systematic review and meta-analysis

Experts have raised concerns that oxytocin for labor induction and augmentation may have detrimental effects on the neurodevelopment of children. To investigate whether there is the reason for concern, we reviewed and evaluated the available evidence by searching databases with no language or date restrictions up to 9 September 2018. We included English-language studies reporting results on the association between perinatal oxytocin exposure and any cognitive impairment, psychiatric symptoms or disorders in childhood. We assessed the quality of studies using the Newcastle-Ottawa Quality Assessment Scales. Independent risk estimates were pooled using random-effects meta-analyses when at least two independent datasets provided data on the same symptom or disorder. Otherwise, we provided narrative summaries. Two studies examined cognitive impairment, one examined problem behavior, three examined attention-deficit/hyperactivity disorder (ADHD) and seven focused on autism spectrum disorders (ASD). We provided narrative summaries of the studies on cognitive impairment. For ADHD, the pooled risk estimate was 1.17; 95% confidence interval (CI) 0.77-1.78, based on a pooled sample size of 5 47 278 offspring. For ASD, the pooled risk estimate was 1.10; 95% CI 1.04-1.17, based on 8 87 470 offspring. Conclusions that perinatal oxytocin increases the risks of neurodevelopmental problems are premature. Observational studies of low to high quality comprise the evidence-base, and confounding, especially by the genetic or environmental vulnerability, remains an issue. Current evidence is insufficient to justify modifying obstetric guidelines for the use of oxytocin, which state that it should only be used when clinically indicated.

The oxytocin receptor gene predicts brain activity during an emotion recognition task in autism

Background

Autism is a highly varied and heritable neurodevelopmental condition, and common variants explain approximately 50% of the genetic variance of autism. One of the genes implicated in autism is the oxytocin receptor (OXTR). The current study combined genetic and brain imaging (fMRI) data to examine the moderating effect of genotype on the association between diagnosis and brain activity in response to a test of cognitive empathy.

Methods

Participants were adolescents (mean age = 14.7 ± 1.7) who were genotyped for single nucleotide polymorphisms (SNPs) within the OXTR and underwent functional brain imaging while completing the adolescent version of the 'Reading the Mind in the Eyes' Test (Eyes Test).

Results

Two (rs2254298, rs53576) of the five OXTR SNPs examined were significantly associated with brain activity during the Eyes Test, and three of the SNPs (rs2254298, rs53576, rs2268491) interacted with diagnostic status to predict brain activity. All of the effects localized to the right supramarginal gyrus (rSMG) and an overlap analysis revealed a large overlap of the effects. An exploratory analysis showed that activity within an anatomically defined rSMG and genotype can predict diagnostic status with reasonable accuracy.

Conclusions

This is one of the first studies to investigate OXTR and brain function in autism. The findings suggest a neurogenetic mechanism by which OXTR-dependent activity within the rSMG is related to the aetiology of autism.

The late positive potential and subjective arousal ratings evoked by negative images vary as a function of oxytocin receptor genotype SNP rs53576

In the central nervous system the neuropeptide oxytocin mediates a range of behaviors related primarily to emotionality. One factor that influences oxytocinergic communication in the human brain and correlates with emotional behaviors is the single nucleotide polymorphism rs53576 on the oxytocin receptor gene (OXTR). For example, variations in this OXTR genotype are related to parental, altruistic, and other prosocial behaviors. Electroencephalographic waveforms of visually evoked response potentials recorded at the midline parietal electrode site display a prominent component putatively involved with attention allocation called the late positive potential. The magnitude of the late positive potential was found to be significantly higher in homozygous G allele individuals compared with A allele carriers when viewing negative emotionally charged images. Inversely, A allele carriers rated these negative images as more arousing, when measured by the Self-Assessment Manikin rating scale. These data suggest that OXTR functioning contributes to visual processing and subjective experience of negative stimuli.

Genetic association of DNMT variants can play a critical role in defining the methylation patterns in autism

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with impairments in social communication, restricted, repetitive and stereotyped behaviors. Both genetic and environmental factors are known to contribute toward pathophysiology of Autism. Environmental influences on gene expression can be mediated by methylation patterns which are established and maintained by DNA methyltransferases. Several studies in the past have investigated the role of global methylations in Autism. The present study is aimed to investigate the role of genetic variations in the DNA methyltransferase which might be critical in defining the threshold for environmental factors toward susceptibility to autism. Polymorphisms in DNA methyltransferases, DNMT1, DNMT3A, DNMT3B, and DNMT3L were screened for association with ASD in 180 autistic patients and 260 healthy controls from a south Indian population. DNMT1 rs10418707 and rs10423341, and DNMT3A rs2289195 were found to be significantly associated at genotypic and allelic level with ASD. Functional prediction indicates that these SNPs have a role in transcriptional regulation and increased expression, indicating that hypermethylation might be induced by its genotype status. The study might reflect the role of genetics variants in DNMTs in defining the threshold of environmental impact in influencing the disease or phenotype variations in ASD. © 2019 IUBMB Life, 2019.

Genetic and epigenetic regulatory mechanisms of the oxytocin receptor gene (OXTR) and the (clinical) implications for social behavior

Oxytocin and the oxytocin receptor (OXTR) play an important role in a large variety of social behaviors. The oxytocinergic system interacts with environmental cues and is highly dependent on interindividual factors. Deficits in this system have been linked to mental disorders associated with social impairments, such as autism spectrum disorder (ASD). This review focuses on the modulation of social behavior by alterations in two domains of the oxytocinergic system. We discuss genetic and epigenetic regulatory mechanisms and alterations in these mechanisms that were found to have clinical implications for ASD. We propose possible explanations how these alterations affect the biological pathways underlying the aberrant social behavior and point out avenues for future research. We advocate the need for integration studies that combine multiple measures covering a broad range of social behaviors and link these to genetic and epigenetic profiles.

Maternal High Fat Diet-Induced Obesity Modifies Histone Binding and Expression of Oxtr in Offspring Hippocampus in a Sex-Specific Manner

Maternal obesity during pregnancy increases risk for neurodevelopmental disorders in offspring, although the underlying mechanisms remain unclear. Epigenetic deregulation associates with many neurodevelopmental disorders, and recent evidence indicates that maternal nutritional status can alter chromatin marks in the offspring brain. Thus, maternal obesity may disrupt epigenetic regulation of gene expression during offspring neurodevelopment. Using a C57BL/6 mouse model, we investigated whether maternal high fat diet (mHFD)-induced obesity alters the expression of genes previously implicated in the etiology of neurodevelopmental disorders within the Gestational Day 17.5 (GD 17.5) offspring hippocampus. We found significant two-fold upregulation of oxytocin receptor (Oxtr) mRNA in the hippocampus of male, but not female, GD 17.5 offspring from mHFD-induced obese dams (p < 0.05). To determine whether altered histone binding at the Oxtr gene promoter may underpin these transcriptional changes, we then performed chromatin immunoprecipitation (ChIP). Consistent with the Oxtr transcriptional changes, we observed increased binding of active histone mark H3K9Ac at the Oxtr transcriptional start site (TSS) in the hippocampus of mHFD male (p < 0.05), but not female, offspring. Together, these data indicate an increased vulnerability of male offspring to maternal obesity-induced changes in chromatin remodeling processes that regulate gene expression in the developing hippocampus, and contributes to our understanding of how early life nutrition affects the offspring brain epigenome.

DNA Methylation and Hydroxymethylation and Behavior

Environmentally sensitive molecular mechanisms in the brain, such as DNA methylation, have become a significant focus of neuroscience research because of mounting evidence indicating that they are critical in response to social situations, stress, threats, and behavior. The recent identification of 5-hydroxymethylcytosine (5hmC), which is enriched in the brain (tenfold over peripheral tissues), raises new questions as to the role of this base in mediating epigenetic effects in the brain. The development of genome-wide methods capable of distinguishing 5-methylcytosine (5mC) from 5hmC has revealed that a growing number of behaviors are linked to independent disruptions of 5mC and 5hmC levels, further emphasizing the unique importance of both of these modifications in the brain. Here, we review the recent links that indicate DNA methylation (both 5mC and 5hmC) is highly dynamic and that perturbations in this modification may contribute to behaviors related to psychiatric disorders and hold clinical relevance.

Oxytocin receptor gene methylation in male and female PTSD patients and trauma-exposed controls

Oxytocin receptor gene (OXTR) DNA-methylation levels have been associated with trauma-exposure, mood- and anxiety disorders, and social processes relevant to posttraumatic stress disorder (PTSD). We hypothesized that OXTR methylation may play a role in the neurobiological underpinnings of PTSD. In the current study, we compared OXTR methylation between PTSD patients (n = 31, 14 females) and trauma-exposed controls (n = 36, 19 females). Additionally, the association between OXTR methylation and PTSD symptom severity and amygdala reactivity to an emotional faces task was assessed, as a neural hallmark of PTSD. DNA-methylation was investigated in the CpG island located at exon 3 of the OXTR, previously associated with OXTR expression. We observed a significant interaction between PTSD-status, sex and CpG-position on methylation levels. Post-hoc testing revealed that methylation levels at two specific CpG-sites were significantly higher in PTSD females compared to female trauma-exposed controls and PTSD males (CpGs Chr3:8809437, Chr3:8809413). No significant differences in methylation were observed between male PTSD patients and controls. Furthermore, within PTSD females, methylation in these CpG-sites was positively associated with anhedonia symptoms and with left amygdala responses to negative emotional faces, although this was no longer significant after stringent correction for multiple-comparisons. Though the modest size of the current sample is an important limitation, we are the first to report on OXTR methylation in PTSD, replicating previously observed (sex-specific) associations of OXTR methylation with other psychiatric disorders.

Early nurture epigenetically tunes the oxytocin receptor

Mammalian sociality is regulated in part by the neuropeptide oxytocin. In prairie voles, subtle variation in early life experience changes oxytocin receptor-mediated social behaviors. We report that low levels of early care in voles leads to de novo DNA methylation at specific regulatory sites in the oxytocin receptor gene (Oxtr), impacting gene expression and protein distribution in the nucleus accumbens. DNA methylation state of the blood predicts expression in the brain indicating the utility of the blood as a biomarker for the transcription state of the brain. These experience-sensitive CpG sites are conserved in humans, are related to gene expression in the brain, and have been associated with psychiatric disorders and individual differences in neural response to social stimuli. These results identify a mechanism by which early care regulates later displays of typical prairie vole social behavior and suggest the potential for nurture driven epigenetic tuning of OXTR in humans.