Genetic variation in the developmental regulation of cortical avpr1a among prairie voles

Transcription and DNA methylation signatures of paternal behavior in hippocampal dentate gyrus of prairie voles

In socially monogamous prairie voles (Microtus ochrogaster), parental behaviors not only occur in mothers and fathers, but also exist in some virgin males. In contrast, the other virgin males display aggressive behaviors towards conspecific pups. However, little is known about the molecular underpinnings of this behavioral dichotomy, such as gene expression changes and their regulatory mechanisms. To address this, we profiled the transcriptome and DNA methylome of hippocampal dentate gyrus of four prairie vole groups, namely attacker virgin males, parental virgin males, fathers, and mothers. While we found a concordant gene expression pattern between parental virgin males and fathers, the attacker virgin males have a more deviated transcriptome. Moreover, numerous DNA methylation changes were found in pair-wise comparisons among the four groups. We found some DNA methylation changes overlapping with transcription differences, across gene-bodies and promoter regions. Furthermore, the gene expression changes and methylome alterations are selectively enriched in certain biological pathways, such as Wnt signaling, which suggest a canonical transcription regulatory role of DNA methylation in paternal behavior. Therefore, our study presents an integrated view of prairie vole dentate gyrus transcriptome and epigenome that provides a DNA epigenetic based molecular insight of paternal behavior.

Individual differences in social attachment: A multi-disciplinary perspective

Social behavior varies across both individuals and species. Research to explain this variation falls under the purview of multiple disciplines, each with its own theoretical and empirical traditions. Integration of these disciplinary traditions is key to developing a holistic perspective. Here, we review research on the biology of social attachment, a phenomena in which individuals develop strong affective connections to one another. We provide a historical overview of research on social attachment from psychological, ethological and neurobiological perspectives. As a case study, we describe work on pair-bonding in prairie voles, a socially monogamous rodent. This specific topic takes advantage of many biological perspectives and techniques to explain social bonds. Lastly, we conclude with an overview of multi-dimensional conceptual frameworks that can be used to explain social phenomena, and we propose a new framework for research on individual variation in attachment behavior. These conceptual frameworks originate from philosophy, physics, ethology, cognitive science and neuroscience. The application and synthesis of such frameworks offers a rich opportunity to advance understanding of social behavior and its mechanisms.

DNA Methylation and Demethylation Underlie the Sex Difference in Estrogen Receptor Alpha in the Arcuate Nucleus

INTRODUCTION

Neurons expressing estrogen receptor (ER) ɑ in the arcuate (ARC) and ventromedial (VMH) nuclei of the hypothalamus sex-specifically control energy homeostasis, sexual behavior, and bone density. Females have more ERɑ neurons in the VMH and ARC than males, and the sex difference in the VMH is eliminated by neonatal treatment with testosterone or a DNA methylation inhibitor.

OBJECTIVE

Here, we tested the roles of testosterone and DNA methylation/demethylation in development of ERɑ in the ARC.

METHODS

ERɑ was examined at birth and weaning in mice that received vehicle or testosterone subcutaneously, and vehicle or DNA methyltransferase inhibitor intracerebroventricularly, as neonates. To examine effects of DNA demethylation on the ERɑ cell number in the ARC, mice were treated neonatally with small interfering RNAs against ten-eleven translocase enzymes. The methylation status of the ERɑ gene (Esr1) was determined in the ARC and VMH using pyrosequencing of bisulfite-converted DNA.

RESULTS

A sex difference in ERɑ in the ARC, favoring females, developed between birth and weaning and was due to programming effects of testosterone. Neonatal inhibition of DNA methylation decreased ERɑ in the ARC of females, and an inhibition of <underline>de</underline>methylation increased ERɑ in the ARC of males. The promoter region of Esr1 exhibited a small sex difference in percent of total methylation in the ARC (females > males) that was opposite to that in the VMH (males > females).

CONCLUSION

DNA methylation and demethylation regulate ERɑ cell number in the ARC, and methylation correlates with activation of Esr1 in this region.

Multi-Level Effects Driving Cognitive and Behavioral Variability among Prairie Voles: Insights into Reproductive Decision-Making from Biological Levels of Organization

Behavioral phenotypes play an active role in maximizing fitness and shaping the evolutionary trajectory of species by offsetting the ecological and social environmental factors individuals experience. How these phenotypes evolve and how they are expressed is still a major question in ethology today. In recent years, an increased focus on the mechanisms that regulate the interactions between an individual and its environment has offered novel insights into the expression of alternative phenotypes. In this review, we explore the proximate mechanisms driving the expression of alternative reproductive phenotypes in the male prairie vole (Microtus ochrogaster) as one example of how the interaction of an individual's social context and internal milieu has the potential to alter behavior, cognition, and reproductive decision-making. Ultimately, integrating the physiological and psychological mechanisms of behavior advances understanding into how variation in behavior arises. We take a "levels of biological organization" approach, with prime focus placed on the level of the organism to discuss how cognitive processes emerge as traits, and how they can be studied as important mechanisms driving the expression of behavior.

Role of Oxytocin and Vasopressin in Neuropsychiatric Disorders: Therapeutic Potential of Agonists and Antagonists

Oxytocin (OT) and vasopressin (AVP) are hypothalamic neuropeptides classically associated with their regulatory role in reproduction, water homeostasis, and social behaviors. Interestingly, this role has expanded in recent years and has positioned these neuropeptides as therapeutic targets for various neuropsychiatric diseases such as autism, addiction, schizophrenia, depression, and anxiety disorders. Due to the chemical-physical characteristics of these neuropeptides including short half-life, poor blood-brain barrier penetration, promiscuity for AVP and OT receptors (AVP-R, OT-R), novel ligands have been developed in recent decades. This review summarizes the role of OT and AVP in neuropsychiatric conditions, as well as the findings of different OT-R and AVP-R agonists and antagonists, used both at the preclinical and clinical level. Furthermore, we discuss their possible therapeutic potential for central nervous system (CNS) disorders.

Is Oxytocin "Nature's Medicine"?

Oxytocin is a pleiotropic, peptide hormone with broad implications for general health, adaptation, development, reproduction, and social behavior. Endogenous oxytocin and stimulation of the oxytocin receptor support patterns of growth, resilience, and healing. Oxytocin can function as a stress-coping molecule, an anti-inflammatory, and an antioxidant, with protective effects especially in the face of adversity or trauma. Oxytocin influences the autonomic nervous system and the immune system. These properties of oxytocin may help explain the benefits of positive social experiences and have drawn attention to this molecule as a possible therapeutic in a host of disorders. However, as detailed here, the unique chemical properties of oxytocin, including active disulfide bonds, and its capacity to shift chemical forms and bind to other molecules make this molecule difficult to work with and to measure. The effects of oxytocin also are context-dependent, sexually dimorphic, and altered by experience. In part, this is because many of the actions of oxytocin rely on its capacity to interact with the more ancient peptide molecule, vasopressin, and the vasopressin receptors. In addition, oxytocin receptor(s) are epigenetically tuned by experience, especially in early life. Stimulation of G-protein–coupled receptors triggers subcellular cascades allowing these neuropeptides to have multiple functions. The adaptive properties of oxytocin make this ancient molecule of special importance to human evolution as well as modern medicine and health; these same characteristics also present challenges to the use of oxytocin-like molecules as drugs that are only now being recognized.

Inside the supergene of the bird with four sexes

The white-throated sparrow (Zonotrichia albicollis) offers unique opportunities to understand the adaptive value of supergenes, particularly their role in alternative phenotypes. In this species, alternative plumage morphs segregate with a nonrecombining segment of chromosome 2, which has been called a 'supergene'. The species mates disassortatively with respect to the supergene; that is, each breeding pair consists of one individual with it and one without it. This species has therefore been called the "bird with four sexes". The supergene segregates with a behavioral phenotype; birds with it are more aggressive and less parental than birds without it. Here, we review our efforts to identify the genes inside the supergene that are responsible for the behavioral polymorphism. The gene ESR1, which encodes estrogen receptor α, differs between the morphs and predicts both territorial and parental behavior. Variation in the regulatory regions of ESR1 causes an imbalance in expression of the two alleles, and the degree to which this imbalance favors the supergene allele predicts territorial singing. In heterozygotes, knockdown of ESR1 causes a phenotypic switch, from more aggressive to less aggressive. We recently showed that another gene important for social behavior, vasoactive intestinal peptide (VIP), is differentially expressed between the morphs and predicts territorial singing. We hypothesize that ESR1 and VIP contribute to behavior in a coordinated way and could represent co-adapted alleles. Because the supergene contains more than 1000 individual genes, this species provides rich possibilities for discovering alleles that work together to mediate life-history trade-offs and maximize the fitness of alternative complex phenotypes.

Epigenomics and gene regulation in mammalian social systems

Social epigenomics is a new field of research that studies how the social environment shapes the epigenome and how in turn the epigenome modulates behavior. We focus on describing known gene–environment interactions (GEIs) and epigenetic mechanisms in different mammalian social systems. To illustrate how epigenetic mechanisms integrate GEIs, we highlight examples where epigenetic mechanisms are associated with social behaviors and with their maintenance through neuroendocrine, locomotor, and metabolic responses. We discuss future research trajectories and open questions for the emerging field of social epigenomics in nonmodel and naturally occurring social systems. Finally, we outline the technological advances that aid the study of epigenetic mechanisms in the establishment of GEIs and vice versa.

Hyper-methylation of AVPR1A and PKCΒ gene associated with insensitivity to arginine vasopressin in human pre-eclamptic placental vasculature

Background

Pre-eclampsia is a leading cause of maternal mortality and morbidity. Although the exact mechanisms that cause pre-eclampsia remain unclear, it is undeniable that abnormal placental function and circulation are a center for initiation pre-eclampsia. As a potent vasoconstrictor, arginine vasopressin (AVP) has long been implicated in controlling placental vascular tone and circulation; its secretion is grossly elevated in pre-eclamptic circulation. However, little is known about the reactivity of AVP in pre-eclamptic placental vasculature.

Methods

To reveal the special features of placental vascular regulations with placental pathophysiological changes, as well as the corresponding molecular mechanisms under pre-eclamptic conditions, vascular function and molecular assays were conducted with placental vessel samples from normal and pre-eclamptic pregnancies.

Findings

The present study found that vasoconstriction responses of placental vessels to AVP were attenuated in pre-eclampsia as compared to in normal pregnancy. The insensitivity of AVP was correlated with the down-regulated AVP receptor 1a (AVPR1A, AVPR1A gene) and protein kinase C isoform β (PKCβ, PKCΒ gene), particularly the hyper-methylation-mediated AVPR1A and PKCΒ gene down-regulation, respectively.

Interpretation

The findings collectively revealed that aberrant DNA methylation-mediated gene expressions are correlated with vascular dysfunction in pre-eclamptic placental circulation.

Fund

This work was supported by National Nature & Science Foundation of China. “333 Project”, “Six one project”, “Shuang Chuang Tuan Dui” and Key Discipline “Fetal medicine” of Jiangsu Province, and the Suzhou city “Wei Sheng Ren Cai” program.

Promoter methylation changes and vascular dysfunction in pre-eclamptic umbilical vein

Background

Hypertension is one of primary clinical presentations of pre-eclampsia. The occurrence and progress of hypertension are closely related to vascular dysfunction. However, information is limited regarding the pathological changes of vascular functions in pre-eclamptic fetuses. Human umbilical cord vein was used to investigate the influence of pre-eclampsia on fetal blood vessels in this study.

Results

The present study found that the vasoconstriction responses to arginine vasopressin (AVP) and oxytocin (OXT) were attenuated in the pre-eclamptic umbilical vein as compared to in normal pregnancy, which was related to the downregulated AVP receptor 1a (AVPR1a), OXT receptor (OXTR), and protein kinase C isoform β (PKCβ), owing to the deactivated gene transcription, respectively. The deactivated AVPR1a, OXTR, and PKCB gene transcription were respectively linked with an increased DNA methylation within the gene promoter.

Conclusions

To the best of our knowledge, this study first revealed that a hyper-methylation in gene promoter, leading to relatively reduced patterns of AVPR1a, OXTR, and PKCB expressions, which was responsible for the decreased sensitivity to AVP and OXT in the umbilical vein under conditions of pre-eclampsia. The data offered new and important information for further understanding the pathological features caused by pre-eclampsia in the fetal vascular system, as well as roles of epigenetic-mediated gene expression in umbilical vascular dysfunction.

Behavioral and epigenetic consequences of oxytocin treatment at birth

Oxytocin is used in approximately half of all births in the United States during labor induction and/or augmentation. However, the effects of maternal oxytocin administration on offspring development have not been fully characterized. Here, we used the socially monogamous prairie vole to examine the hypothesis that oxytocin exposure at birth can have long-term developmental consequences. Maternally administered oxytocin increased methylation of the oxytocin receptor (Oxtr) in the fetal brain. As adults, oxytocin-exposed voles were more gregarious, with increased alloparental caregiving toward pups and increased close social contact with other adults. Cross-fostering indicated that these effects were the result of direct action on the offspring, rather than indirect effects via postnatal changes in maternal behavior. Male oxytocin-exposed offspring had increased oxytocin receptor density and expression in the brain as adults. These results show that long-term effects of perinatal oxytocin may be mediated by an epigenetic mechanism.

Oxytocin and excitation/inhibition balance in social recognition

Social recognition is the sensitive domains of complex behavior critical for identification, interpretation and storage of socially meaningful information. Social recognition develops throughout childhood and adolescent, and is affected in a wide variety of psychiatric disorders. Recently, new data appeared on the molecular mechanisms of these processes, particularly, the excitatory-inhibitory (E/I) ratio which is modified during development, and then E/I balance is established in the adult brain. While E/I imbalance has been proposed as a mechanism for schizophrenia, it also seems to be the common mechanism in autism spectrum disorder (ASD). In addition, there is a strong suggestion that the oxytocinergic system is related to GABA-mediated E/I control in the context of brain socialization. In this review, we attempt to summarize the underpinning molecular mechanisms of E/I balance and its imbalance, and related biomarkers in the brain in healthiness and pathology. In addition, because there are increasing interest on oxytocin in the social neuroscience field, we will pay intensive attention to the role of oxytocin in maintaining E/I balance from the viewpoint of its effects on improving social impairment in psychiatric diseases, especially in ASD.

Individual Differences in Social Behavior and Cortical Vasopressin Receptor: Genetics, Epigenetics, and Evolution

Social behavior is among the most complex and variable of traits. Despite its diversity, we know little about how genetic and developmental factors interact to shape natural variation in social behavior. This review surveys recent work on individual differences in the expression of the vasopressin 1a receptor (V1aR), a major regulator of social behavior, in the neocortex of the socially monogamous prairie vole. V1aR exhibits profound variation in the retrosplenial cortex (RSC), a region critical to spatial and contextual memory. RSC-V1aR abundance is associated with patterns of male space-use and sexual fidelity in the field: males with high RSC-V1aR show high spatial and sexual fidelity to partners, while low RSC-V1aR males are significantly more likely to mate outside the pair-bond. Individual differences in RSC-V1aR are predicted by a set of linked single nucleotide polymorphisms within the avpr1a locus. These alternative alleles have been actively maintained by selection, suggesting that the brain differences represent a balanced polymorphism. Lastly, the alleles occur within regulatory sequences, and result in differential sensitivity to environmental perturbation. Together the data provide insight into how genetic, epigenetic and evolutionary forces interact to shape the social brain.

The Oxytocin-Vasopressin Pathway in the Context of Love and Fear

Vasopressin (VP) and oxytocin (OT) are distinct molecules; these peptides and their receptors [OT receptor (OTR) and V1a receptor (V1aR)] also are evolved components of an integrated and adaptive system, here described as the OT-VP pathway. The more ancient peptide, VP, and the V1aRs support individual survival and play a role in defensive behaviors, including mobilization and aggression. OT and OTRs have been associated with positive social behaviors and may function as a biological metaphor for social attachment or "love." However, complex behavioral functions, including selective sexual behaviors, social bonds, and parenting require combined activities of OT and VP. The behavioral effects of OT and VP vary depending on perceived emotional context and the history of the individual. Paradoxical or contextual actions of OT also may reflect differential interactions with the OTR and V1aR. Adding to the complexity of this pathway is the fact that OT and VP receptors are variable, across species, individuals, and brain region, and these receptors are capable of being epigenetically tuned. This variation may help to explain experience-related individual and sex differences in behaviors that are regulated by these peptides, including the capacity to form social attachments and the emotional consequences of these attachments.

Vasopressinergic Neurocircuitry Regulating Social Attachment in a Monogamous Species

The prairie vole (Microtus ochrogaster) is a socially monogamous rodent species that forms a lasting connection between mates, known as a pair bond. The pair bond is primarily characterized by three distinct behaviors: partner preference, selective aggression, and biparental care of the young. The presence of these behaviors in the prairie vole and their absence in closely related non-monogamous species makes the prairie vole an important model of social relationships and facilitates the study of the neurobiological mechanisms of social affiliation and attachment. The nona-peptide arginine-vasopressin (AVP) is an important neuromodulator of social behavior and has been implicated in the regulation of the pair bond-related behaviors of the prairie vole, through activation of the AVP receptor subtype 1a (AVPR1a). Modulation of AVPR1a activity in different regions of the prairie vole brain impacts pair bond behavior, suggesting a role of AVP in neurocircuitry responsible for the regulation of social attachment. This review will discuss findings that have suggested the role of AVP in regulation of the pair bond-related behaviors of the prairie vole and the specific brain regions through which AVP acts to impact these unique behaviors.