GENETIC AND ENVIRONMENTAL DETERMINANTS OF PRIMATE BIOBEHAVIORAL DEVELOPMENT
, Head, Section on Comparative Behavioral Genetics
Matthew F.X. Novak, PhD, Senior Postdoctoral Researcher
Kathlyn L. Robbins, PhD, Research Psychologist
Craig Abbott, PhD, Statistician
Peggy O’Neill Wagner, MA, Senior Research Assistant
Consuel S. Ionica, PhD, Visiting Fellow
Annika Paukner, PhD, Visiting Fellow
Angela Ruggiero, BS, BioScience Laboratory Technician
Amanda Dettmer, MS, Predoctoral Fellow
Khalisa Herman, MS, Predoctoral Fellow
Mary Huntsberry, MS, Predoctoral Fellow
Marja Knappe, MS, Visiting Predoctoral Fellow
Lisa Darcey, BS, Postbaccalaureate Fellow
Elizabeth Kerschner, BS, Technician-in-Training
Michelle L. Miller, BS, Technician-in-Training
Sarah J. Ubehagen, BS, Technician-in-Training
Our research involves broad-based investigation of primate biological and behavioral development through comparative longitudinal studies of rhesus monkeys and other primates. Our primary goals are to characterize distinctive biobehavioral phenotypes in our rhesus monkey colony, to determine how genetic and environmental factors interact to shape the developmental trajectories of each phenotype, and to assess the long-term behavioral and biological consequences for monkeys from different genetic backgrounds when they are reared in different physical and social environments. A second major program of research investigates how rhesus monkeys and other nonhuman primate species born and raised under different laboratory conditions adapt to placement in environments that model specific features of their natural habitat.
Developmental continuity of individual differences in rhesus monkey biobehavioral development
This past year, we expanded our efforts to characterize developmental changes in peripheral measures of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in rhesus monkeys with different early social rearing backgrounds; we assayed plasma for NGF and BDNF collected longitudinally from monkeys reared from birth either by their biological mother (MR) or in the neonatal nursery with subsequent continuous access to peers (PR). We replicated our previous findings that plasma NGF levels increase sharply from 2 weeks to 1 year of age for both MR and PR subjects (essentially achieving adult levels at that point) and exhibit a significant age-by-rearing-condition interaction: MR and PR infants initially have equivalent NGF levels, but, as they grow older, PR infants undergo a greater increase in NGF levels than do their MR counterparts. We found the opposite developmental pattern for BDNF: plasma levels for both sets of infants are highest at 2 weeks of age and thereafter decline dramatically with age. MR subjects have much higher 2-week levels than PR infants, but the difference is reversed by 60 days, with MR subjects’ levels dropping more precipitously than those of PR infants. In addition, female infants consistently exhibit higher plasma BDNF levels than do males. Among PR (but not MR) infants, plasma NGF and cortisol levels are significantly correlated. Finally, within each rearing group, individual differences in both plasma NGF and BDNF values remain largely stable throughout development, suggesting possible genetic influences. One potential candidate gene is the BDNF gene, for which functional polymorphisms have been characterized in both human and rodent samples. In the coming year, we plan to test whether the same or functionally similar polymorphisms are present in rhesus monkeys and whether any polymorphic differences in the rhesus monkey BDNF gene are associated with individual differences in plasma BDNF values throughout development.
We initiated two collaborative projects comparing MR and PR rhesus monkeys on additional measures of biological functioning. The first study involved researchers from University of California San Francisco (UCSF) who have demonstrated differences in telomere length in adult humans as a function of differences in social status and cumulative social stress; differences in telomere length are thought to be a marker of relative cellular age. The researchers hypothesized that these differences may have their origin in differential experiences with social stress during the childhood years, a period when telomere length shortens rapidly. Accordingly we have been providing our colleagues with DNA extracted from whole blood samples collected from both MR and PR monkeys throughout their first two years of life, a developmental period for which we have demonstrated major differences between MR and PR monkeys in behavioral and biological responses to social stress. Our UCSF colleagues are currently analyzing the DNA with respect to telomere length. The second study involves a collaboration with colleagues from McGill University; in an elegant series of studies, they demonstrated that differential rates of maternal licking and grooming of rat pups during their second week of life result in different patterns of expression in the glucocorticoid receptor gene in hippocampal brain regions as a consequence of differential methylation; the expression patterns in turn are associated with different patterns of behavioral and neuroendocrine response to social stress not only throughout the lifetime of the pups but also in the pups’ own progeny. With our colleagues, we are currently assessing methylation patterns in hippocampal glucocorticoid receptor genes and in buccal samples and lymphocytes obtained from MR and PR monkeys throughout development.
Much of our recent research has focused on characterizing interactions between differential early social rearing and polymorphisms in several “candidate” genes (G × E interactions), most notably the serotonin transporter gene (5-HTT) and MAO-A gene. We have characterized, throughout rhesus monkey development, the relationship between these polymorphisms and a variety of measures of behavioral and biological functioning, including physical aggression, hypothalamic-pitutary-adrenal axis reactivity, and central serotonin metabolism. With colleagues from the NIAAA, we characterized additional functional polymorphisms in the neuropeptide Y (NPY) promoter gene, the corticotrophin-releasing factor (CRH) 2A gene, and the mu opoid receptor gene. We demonstrated specific G × E interactions with respect to juvenile rhesus monkeys’ behavioral responses to social separation and several measures of alcohol preference and consumption among young adult monkeys.
As mentioned, rhesus macaques (and humans) have functional polymorphisms in the 5-HTT and MAO-A genes. In both species, interactions of these polymorphisms with differential early experiences have been linked to developmentally stable individual differences in aggressiveness. Last year, we published data characterizing the 5-HTT and MAO-A genes in six other macaque species: Barbary (M. sylvanis), crab-eating (M. fasicularis), pigtail (M. nemestrina), stumptail (M. arctoides), Tibetan (M. thibetanna), and Tonkenan (M. tonkeana). Unlike the case for rhesus monkeys, we found no functional polymorphisms for the two genes in any of these other macaque species. Moreover, for the 5-HTT gene, we observed an apparent inverse relationship between the relative length of the promoter region and the relative level of aggressiveness reported from field observations of each species. This year, we collected behavioral data and obtained cerebrospinal fluid (CSF) samples from the Barbary, crab-eating, and Tonkenan macaque subjects that we had previously genotyped for the 5-HTT gene. Our aim was to determine (1) whether the strong inverse relationship between CSF 5-HIAA concentrations and levels of aggressive behavior previously demonstrated for humans and for rhesus and pigtail macaques holds for these other macaque species and (2) whether species differences in these measures parallel the species differences in promoter-region length of the 5-HTT gene.
Barr CS, Schwandt ML, Chen SA, Goldman D, Suomi SJ, Higley JD, Heilig M. Association of a functional polymorphism in the Mu-opoid receptor gene (OPMRIC77G) with alcohol response and consumption in rhesus monkeys. Arch Gen Psychiat 2007;64:369-76.
Roma PG, Ruggiero AM, Schwandt ML, Higley JD, Suomi SJ. The kids are allright: maternal behavioral interactions and stress reactivity in infants of differentially reared mothers. J Dev Process 2007;1:103-22.
Schwandt ML, Barr CS, Suomi SJ, Higley JD. Age-dependent variation in behavior following acute alcohol administration in male and female adolescent rhesus macaque monkeys (Macaca mulatta). Alcohol Clin Exp Res 2007;31:228-39.
Spinelli S, Schwandt ML, Lindell SG, Newman TK, Heilig M, Higley DH, Suomi SJ, Goldman D, Barr CS. Association between the rh-5httLPR polymorphism and behavior in rhesus macaques during social separation stress. Develop Psychopathol 2007;19:977-87.
Suomi SJ. Risk, resilience, and gene × environment interactions in rhesus monkeys. Ann NY Acad Sci 2006;1094:52-62.
Adaptation of laboratory-reared monkeys to field environments
We assess adaptation by examining behavioral repertoires and monitoring a variety of physiological systems in monkeys throughout the lifespan, yielding broad-based indices of relative physical and psychological well-being. We also assess the responses of subjects to experimental manipulations of selected features of their respective environments. Whenever possible, we collect field data for appropriate comparisons. In addition, we investigate the cognitive, behavioral, and social processes involved in adaptation to new settings and circumstances.
We followed up on our initial study of rhesus monkey infants’ capacity to imitate specific facial expressions directed toward them by a human model in their first days of life. It is thought that mirror neurons mediate the early imitative capabilities reported for human neonates; mirror neurons are a recently characterized class of visual motor neurons found in ventral premotor and parietal cortex. We found that some (but not all) tested newborns were able to mimic specific facial expressions involving differential mouth and tongue movements, but not until the second or third day of life. Follow-up behavioral observations revealed that, from four months onward, infants that had exhibited imitative behavior during the first week of life subsequently exhibited significantly higher levels of social play during peer interaction sessions than did infants that failed to imitate during their first week. Moreover, when the monkeys were subsequently moved permanently into large groups of same-age peers, those that had failed to imitate during the first days of life exhibited much higher levels of self-directed behaviors than those who did imitate and displayed repeated bouts of autistic-like repetitive stereotypic behavior, something that we never observed in monkeys that demonstrated imitative capabilities as neonates. This past year, in collaboration with colleagues from the University of Maryland, we developed a procedure to monitor EEG activity in the monkey infants throughout the imitative test sessions as well as during appropriate non-imitative control periods. Initial analyses have revealed (1) that it is possible to obtain EEG data reliably and relatively unobtrusively from newborn rhesus infants in an imitative test setting and (2) that specific patterns of slow-wave EEG activity coincide with imitative behavior seemingly consistent with the slow-wave EEG activity previously found to accompany mirror neuron activity in adult macaques but not seen in infants that fail to imitate in the same setting.
We published the results of a prospective longitudinal study examining the relationship between CSF 5-HIAA concentrations and life-history outcomes in male rhesus monkeys living in a free-ranging environment on Morgan Island, South Carolina. Previous work with this field population had demonstrated a significant inverse relationship between CSF 5-HIAA concentrations and levels of aggression during the juvenile and adolescent years, replicating findings obtained in laboratory studies. Previous studies also demonstrated a positive relationship between 5-HIAA concentrations and both age of male natal troop emigration and likelihood of survival with increasing age. Results of the present analyses extended some previous findings and qualified others. First, as in earlier studies, individual differences in CSF 5-HIAA concentrations were exceedingly stable from pre-adolescence into the adult years; males with relatively high 5-HIAA concentrations at age 2 to 3 three years continued to exhibit high levels at 10 years of age and beyond; males with low 5-HIAA concentrations as juveniles continued to exhibit low levels in subsequent years. Second, as previously reported, low CSF 5-HIAA concentrations early in life were associated with early mortality—but only for males that emigrated from their natal troop before puberty. A few males with low CSF 5-HIAA concentrations as juveniles stayed in their natal troop well past puberty before eventually emigrating, and their post-emigration mortality rate was relatively low. Interestingly, virtually all late-emigrating low–5-HIAA males were offspring of females from socially dominant families within the natal troop. Thus, it appears that, in natural settings, high family social status may represent a powerful protective factor for rhesus monkey males whose patterns of aggressive behavior and serotonin metabolism would otherwise put them at high risk for early mortality.
We also tested the efficacy of a new design for a fleece-covered surrogate “mother” for our nursery-reared rhesus monkey infants. Unlike traditional surrogates that are spring-mounted from a base resting on the floor of the infant’s cage, the new surrogates hang from the top of the cage, not only affording greater movement in more dimensions than the traditional model but also giving the infant greater control of the surrogate’s movements. We found that, compared with infants reared on traditional surrogates, infants reared on the hanging surrogates exhibited a stronger grasping response, greater motor coordination, earlier spontaneous crawling, and better balance during their first month; more exploratory behavior in their home cage; and more time away from their surrogate and lower salivary cortisol levels when placed in a novel setting. As a result of these findings, we are now replacing the standard surrogates with the hanging model in our nursery. In addition, we demonstrated the efficacy of a retractable perch for more effective utilization of cage space in both individually and group-housed monkeys of different ages.
In collaboration with colleagues from the University of Massachusetts, we collected several samples of hair from monkeys of different ages, rearing backgrounds, current housing conditions, and social status to be assayed for cortisol levels as a potential index of chronic stress. We compared those values with cortisol levels repeatedly obtained from saliva during the extended periods between concomitant hair sampling of the same monkeys and behavioral observations. Our initial analyses indicate that cortisol values hold considerable promise as a reliable index of individual differences in chronic stress, at least in monkeys sampled to date.
We published several studies reporting on our colony of tufted capuchin monkeys. One study revealed that preferences for specific food items in restricted-choice situations appear to be motivated more by the experience of frustration than by aversion resulting from perceived social inequality. A second study showed that capuchin monkeys, even when trained to touch visible marks on their body, are not able to use a mirror to touch such marks not visible without the mirror, a standard test of self-recognition in human infants and several other primate species. A third study documented that urine washing was not influenced by relative temperature and humidity and hence seems unlikely to have a thermoregulatory function, as has been the consensus hypothesis to date; rather, urine washing appears to have specific social functions for individuals of different gender and social status.
Ferrari P, Visalberghi E, Paukner A, Fogassi L, Ruggiero A, Suomi SJ. Neonatal imitation in rhesus macaques. PLoS Biol 2006;4:1501-8.
Howell S, Westergaard GC, Hoos B, Chavanne TJ, Schoaf SE, Cleveland A, Snoy PJ, Suomi SJ, Higley JD. Serotonergic influences on life-history outcomes in free-ranging male rhesus macaques. Am J Primatol 2007;69:851-65.
Miller KE, Laszlo K, Suomi SJ. Why do captive capuchins (Cebus apella) urine-wash? Am J Primatol 2007 [E-pub ahead of print].
Novak MF, Kenny C, Suomi SJ, Ruppenthal GC. Use of animal operated foldable perch by rhesus macaques (Macacca mulatta). J Am Assoc Lab Anim Sci 2007;46:35-43.
Roma PG, Silverberg A, Huntsberry ME, Christensen CJ, Ruggiero AM, Suomi SJ. Mark test for mirror self-recognition in capuchin monkeys (Cebus apella) trained to touch marks. Am J Primatol 2007;69:989-1000.
COLLABORATOR
Nancy Adler, PhD, University of California San Francisco, San Francisco, CA
Enrico Alleva, MD, Istituto Superiore di Sanitá, Rome, Italy
Christina Barr, PhD, DVM, Laboratory of Clinical and Translational Studies, NIAAA, Poolesville, MD
Allyson J. Bennett, PhD, Wake Forest University School of Medicine, Winston-Salem, NC
Gayle D. Byrne, PhD, University of Maryland, College Park, MD
Maribeth Champoux, PhD, Center for Scientific Review, NIH, Bethesda, MD
Francesca Cirulli, PhD, Istituto Superiore di Sanità,Rome, Italy
Elissa Epel, PhD, University of California San Francisco, San Francisco, CA
Pier F. Ferrari, PhD, Universitá di Parma, Parma, Italy
Melissa Gerald, PhD, Caribbean Primate Research Center, Punta Santiago, PR
David A. Goldman, MD, Laboratory of Neurogenetics, NIAAA, Bethesda, MD
Markus Heilig, MD, Laboratory of Clinical Studies, NIAAA, Bethesda, MD
J. D. Higley, PhD, Brigham Young University, Provo, UT
Robert Innis, MD, Molecular Imaging Branch, NIMH, Bethesda, MD
Mark L. Laudenslager, PhD, University of Colorado Health Sciences Center, Denver, CO
K. Peter Lesch, MD, Universität Würzburg, Würzburg, Germany
Michael J. Meaney, PhD, McGill University, Montreal, Canada
Eric Nelson, PhD, Emotional Development and Affective Neuroscience Branch, NIMH, Bethesda, MD
Melinda A. Novak, PhD, University of Massachusetts, Amherst, MA
Melanie L. Schwandt, PhD, Laboratory of Clinical and Translational Studies, NIAAA, Poolesville, MD
Susan E. Shoaf, PhD, Laboratory of Clinical and Translational Studies, NIAAA, Poolesville, MD
Alan Silberberg, PhD, American University, Washington, DC
Simona Spinelli, PhD, Laboratory of Clinical and Translational Studies, NIAAA, Poolesville, MD
Moshe Szyf, PhD, McGill University, Montreal, Canada
Bernard Thierry, PhD, Centre d’Ecologie, Physiologie et Ethologie, CNRS, Strasbourg, France
Angelika Timme, PhD, Freie Universität Berlin, Berlin, Germany
Elisabetta Visalberghi, PhD, Istituto de Scienze e Technologie della Cognizione, CNR, Rome, Italy
Jens Wendland, PhD, Laboratory of Clinical Science, NIMH, Bethesda, MD
James T. Winslow, PhD, Non-Human Primate Core, NIMH, Bethesda, MD
For further information, contactsuomis@mail.nih.gov.
