Validation of Metabolic and Immunologic Biomarkers TNF-a, IGF, IL-6, CRP and Hair Cortisol in the Common Marmoset

The common marmoset is a good model for research because they are easy to house and have complex social relationships (French et al., 2019). Marmosets are sensitive to social isolation, and when introduced to a stressor, the HPA axis is activated (Saltzman & Abbott, 2011). The purpose of this experiment is to validate marmosets as a translational model for stress due to social relationships in humans. This is done by validating biomarker concentration levels at baseline, then comparing the concentration when introduced to a stressor. The biomarkers IL-6, CRP, IGF-1 and TNF-a were tested using a serum assay, then running the well plate under a plate reader to determine the concentration. No antibodies were detected in the marmoset samples for the biomarkers IL-6, CRP, IGF-1 and TNF-a. Chronic cortisol concentration was determined using marmoset hair samples. The high stress group for hair cortisol concentration was significantly greater than the control group, providing evidence that hair cortisol is a reliable biomarker for long-term chronic stress. Marmosets can be used as a translational animal model to further understand and study both acute and chronic stress due to social relationships and isolation

Leu8 and Pro8 oxytocin agonism differs across human, macaque, and marmoset vasopressin 1a receptors

Oxytocin (OXT) is an important neuromodulator of social behaviors via activation of both oxytocin receptors (OXTR) and vasopressin (AVP) 1a receptors (AVPR1a). Marmosets are neotropical primates with a modified OXT ligand (Pro8-OXT), and this ligand shows significant coevolution with traits including social monogamy and litter size. Pro8-OXT produces more potent and efficacious responses at primate OXTR and stronger behavioral effects than the consensus mammalian OXT ligand (Leu8-OXT). Here, we tested whether OXT/AVP ligands show differential levels of crosstalk at primate AVPR1a. We measured binding affinities and Ca2+ signaling responses of AVP, Pro8-OXT and Leu8-OXT at human, macaque, and marmoset AVPR1a. We found that AVP binds with higher affinity than OXT across AVPR1a, and marmoset AVPR1a show a 10-fold lower OXT binding affinity compared to human and macaque AVPR1a. Both Leu8-OXT and Pro8-OXT produce a less efficacious response than AVP at human AVPR1a and higher efficacious response than AVP at marmoset AVPR1a. These data suggest that OXT might partially antagonize endogenous human AVPR1a signaling and enhance marmoset AVPR1a signaling. These findings aid in further understanding inconsistencies observed following systemic intranasal administration of OXT and provide important insights into taxon-specific differences in nonapeptide ligand/receptor coevolution and behavior

Natural variation in gestational cortisol is associated with patterns of growth in marmoset monkeys (Callithrix geoffroyi)

High levels of prenatal cortisol have been previously reported to retard fetal growth. Although cortisol plays a pivotal role in prenatal maturation, heightened exposure to cortisol can result in lower body weights at birth, which have been shown to be associated with adult diseases like hypertension and cardiovascular disease. This study examines the relationship between natural variation in gestational cortisol and fetal and postnatal growth in marmoset monkeys. Urinary samples obtained during the mother’s gestation were analyzed for cortisol. Marmoset body mass index (BMI) was measured from birth through 540 days in 30- or 60-day intervals. Multi-level modeling was used to test if marmoset growth over time was predicted by changes in gestational cortisol controlling for time, sex, litter, and litter size. The results show that offspring exposed to intra-uterine environments with elevated levels of cortisol had lower linear BMI rates of change shortly after birth than did offspring exposed to lower levels of cortisol, but exhibited a higher curvilinear growth rate during adolescence. Average daily change in gestational cortisol during the first trimester had a stronger relationship with postnatal growth than change during the third trimester. Higher exposure to cortisol during gestation does alter developmental trajectories, however there appears to be a catch-up period during later post-natal growth. These observations contribute to a larger discussion about the relationship of maternal glucocorticoids on offspring development and the possibility of an earlier vulnerable developmental window

Gene changes may minimize masculinizing and defeminizing influences of exposure to male cotwins in female callitrichine primates

Background: Sexual differentiation in female mammals can be altered by the proximity of male littermates in utero, a phenomenon known as the intrauterine position effect (IUP). Among simian primates, callitrichines (marmosets and tamarins) are likely candidates for IUP, since they exhibit obligate dizygotic twinning and fetuses share extensive vascularization in utero. In this paper, we determined whether female reproductive parameters are altered by gestating with a male twin and evaluated changes in genes associated with anti-Müllerian and steroid hormones in twinning callitrichine primates. Methods: We assessed the impact of gestation with male cotwins on reproductive performance and survivorship in female marmosets (Callithrix) and lion tamarins (Leontopithecus), contrasting measures for females gestated with one or more littermates (M+) or no male littermates (0M). We compared targeted coding regions for genes involved in steroidal and anti-Müllerian hormone mediation of sexual differentiation for representatives of twinning callitrichines (Callithrix, Saguinus, and Leontopithecus) with closely related New World primates that produce single births (Saimiri and Callimico). Results: IUP effects in females were absent in female callitrichine primates: age at first ovulation, average litter size, and the proportion of stillborn infants, and lifetime survivorship did not differ between M+ and 0M females. We documented multiple nonsynonymous substitutions in genes associated with steroid synthesis, transport, and cellular action (SRD5A2, CYP19A1, SHBG, and AR) and with anti-Müllerian hormone (AMH and AMHR2) in callitrichines. In the only callitrichine to produce single infants (Callimico), two genes contained nonsynonymous substitutions relative to twinning callitrichines (CYP19A1 and AMRHR2); these substitutions were identical with nontwinning Saimiri and humans, suggesting a reversion to an ancestral sequence.Conclusions: In spite of a shared placental vasculature with opposite-sex twins throughout embryonic and fetal development, female callitrichine primates gestated with a male cotwin exhibit no decrement in reproductive performance relative to females gestated with female cotwins. Hence, IUP effects on female reproduction in callitrichines are modest. We have identified mutations in candidate genes relevant for steroid hormone signaling and metabolism, and especially in AMH-related genes, that are likely to alter protein structure and function in the callitrichines. These mutations may confer protection for females from the masculinizing and defeminizing influences of gestating with a male cotwin

Marmosets’ response to inequity following manipulation of the oxytocin system

One of the foremost properties of human cooperation is the egalitarian sharing of resources when, for example, one prefers to share resources in a way that provides neither an advantageous nor a disadvantageous outcome to themselves or others. This preference is known as inequity aversion. Recent attention has focused on the extent and context for which nonhuman primates respond to inequitable outcomes. Because primates exhibit diverse social structures and cognitive abilities, studying responses to inequity across many species will help elucidate functions and contexts for which inequity aversion may have evolved. Potential neuroendocrine mechanisms for inequity aversion in nonhuman primates have also yet to be explored. Across mammals, oxytocin is an important neuropeptide in the regulation and monitoring of social affiliation, social cognition, and interpretation of social signals. Consequently, oxytocin emerges as a leading candidate for a central neuroendocrine mechanism underlying cooperative behaviors like inequity aversion. In this study, we examined how oxytocin agonists and antagonists influence food sharing and social behavior in opposite-sex marmoset dyads. Experiments assessed marmoset’s social behavior and provisioning of food in equitable and inequitable outcomes to themselves, their long-term partner, or opposite-sex strangers, and by administering oxytocin agonists, antagonists, and controls, we were able to examine whether oxytocin would influence the propensity to share food with others in cases of both equity and inequity. The results suggest that marmosets are not sensitive to inequity aversion in general, but food sharing and social behavior are influenced by social context (partner type and presence) and oxytocin treatment

Exploring the Presence of the Catechol-O-Methyltransferase (COMT) Polymorphism in Marmosets and its Potential Influence on Prosocial Behavior

The Catechol-O-Methyltransferase gene (COMT) is an important gene involved in the enzymatic breakdown of the neurotransmitter dopamine. In humans, there is a functional single-nucleotide polymorphism (SNP) (rs4680) where a Valine (GTG) is substituted for a Methionine (ATG) resulting in lower COMT enzyme activity in the catabolism of dopamine. This leads to increased biologically-available dopamine in brain synapses. However, no information is currently available as to whether this functional COMT SNP is present in the Platyrrhini parvorder or more specifically the Cebidae family including marmosets and tamarins. Using nested polymerase-chain-reaction (PCR) we amplified extracted DNA from four species of marmosets (Callithrix sp.) and one species of tamarin (Leontopithecus rosalia), sequenced the DNA for the presence of the rs4680 SNP, and aligned the sequence data to reference primates. We found no evidence of the rs4680 SNP in marmosets and tamarins, which likely indicates very low or absent allelic variation in the rs4680 SNP. We did find the presence of a novel SNP located in AA position 369 in the COMT gene. This nucleotide substitution from T to C leads to a synonymous protein product likely suggesting no functional impact. The allelic frequency of this SNP in the sampled population is TT = 14.3%, TC = 17.9%, and CC = 67.9%. More sampling of Platyrrhini (New-World monkeys) and other mammals is required, but these data, as they currently stand, suggest the rs4680 mutation likely occurred after the emergence of Catarrhini (Old-World monkeys, Great Apes, human lineages) which occurred approximately 20-38 million years ago

Care to share? Exploring the relationship between altruism and oxytocin in marmosets

Both human and nonhuman primates show the capacity to demonstrate other-regarding preferences, i.e., an understanding for the existence, benefit, and welfare of other individuals. However, the motivation or capacity to demonstrate other-regarding preferences, or to behave altruistically, depends on the social, cognitive, and neuroendocrine context. Oxytocin (OT) moderates the salience of social cues and affiliation toward others, but the extent to which OT facilitates altruistic behavior such as other-regarding preferences in nonhuman primates is currently unknown. Thus, the aim of this study was to use a Prosocial Choice Task (PCT) to evaluate whether 6 marmoset donors will altruistically provision food to familiar and unfamiliar partners. Additionally, I explored whether the manipulation of OT would influence the provisioning of food to familiar and unfamiliar partners. I found that marmosets preferentially rewarded unfamiliar partners but not familiar partners, which reveals marmosets’ capacity for other-regarding preferences. However, OT did not influence the proportion of altruistic tray pulling in the PCT or homecage grooming and proximity. These results suggest that marmosets are more sensitive to the payoffs of unfamiliar partners over familiar partners, but this effect occurred independent of OT manipulation. These findings highlight the importance of social context in understanding the motivation and demonstration for other-regarding preferences. However, more work is needed to uncover mechanisms and motivations for the marmosets’ stronger preference to reward unfamiliar partners more frequently than familiar partners

The Impact of Social Isolation on Cognitive Performance in Marmoset Monkeys

Disruption of social relationships is among the biggest factors contributing to poor health and well-being. One of the major neuroregulatory pathways associated with physiological and behavioral responses to stressors is the hypothalamic-pituitary-adrenal (HPA) axis. In response to a stressor, the hypothalamus secretes corticotrophin- releasing hormone (CRH), which mediates the release of adrenocorticotropic hormone into the bloodstream. This leads to the release of glucocorticoids (e.g., cortisol), which is a key component in the physiological stress response . One specific area of health outcomes that has received less attention is the association between stress and age-related changes in cognitive function. Marmosets are a well-suited model to address this question because individuals form strong social pair bonds, exhibit complex cognition, and as a result exhibit similar impaired physiological and behavioral functioning as humans do in response to induced periods of social isolation. The goal is to address the link between social stress and cognition in three keyways. 1) Investigate how marmosets perform on a standard cognitive learning task in response to a social isolation stressor in marmosets. 2) Examine the role of the HPA axis in mediating this effect by blocking the CRH hormone that is released in response to stressors. 3) examine whether these effects are consistent or divergent across different age groups of marmosets including middle and old-aged marmosets. The overarching goal of this project is to investigate the extent to which chronic social isolation effects the learning ability of adult and old-aged common marmoset monkeys utilizing a standardized reversal learning task while manipulating HPA function via treatments with a CRH antagonist (blocks CRH function). Chronic social isolation reflects prolonged stressors which more appropriately models stress-induced deficits in cognition seen in mental health compared to an acute stressor

Genetic Diversity in Oxytocin Ligands and Receptors in New World Monkeys

Oxytocin (OXT) is an important neurohypophyseal hormone that influences wide spectrum of reproductive and social processes. Eutherian mammals possess a highly conserved sequence of OXT (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly). However, in this study, we sequenced the coding region for OXT in 22 species covering all New World monkeys (NWM) genera and clades, and characterize five OXT variants, including consensus mammalian Leu8-OXT, major variant Pro8-OXT, and three previously unreported variants: Ala8-OXT, Thr8-OXT, and Phe2-OXT. Pro8-OXT shows clear structural and physicochemical differences from Leu8-OXT. We report multiple predicted amino acid substitutions in the G protein- coupled OXT receptor (OXTR), especially in the critical N-terminus, which is crucial for OXT recognition and binding. Genera with same Pro8-OXT tend to cluster together on a phylogenetic tree based on OXTR sequence, and we demonstrate significant coevolution between OXT and OXTR. NWM species are characterized by high incidence of social monogamy, and we document an association between OXTR phylogeny and social monogamy. Our results demonstrate remarkable genetic diversity in the NWM OXT/OXTR system, which can provide a foundation for molecular, pharmacological, and behavioral studies of the role of OXT signaling in regulating complex social phenotypes

Will You Still Like Me Tomorrow?: Long term Changes in Sociosexual Relationships in Marmosets (Callithrix jacchus)

This abstract has been removed to protect the intellectual property of the project