Developmental Continuity Of Individual Differences In Reactivity In Monkeys

与前几年一样，该项目的主要重点是对不同早期社会养育方式的行为和生物学后果进行详细的纵向研究，最值得注意的是比较由其亲生母亲在有成年雄性的围栏中抚养的恒河猴婴儿和其他母亲在其出生后与母亲分离的相同年龄婴儿的头6-7个月（MR）。第一个月在实验室新生儿托儿所人工饲养，然后在接下来的6个月里在同龄同伴的小组中饲养（PR）。在第三种标准抚养环境中，代孕同伴抚养（SPR），婴儿与母亲分开，像PR婴儿一样抚养，但在1个月大的时候，他们被关在单独的笼子里，里面有一个没有生命的代孕母亲，另外，在接下来的6个月里，他们和其他3个同样抚养的同伴一起被放在一个游戏笼子里，每天2小时。在7个月大的时候，MR， PR和SPR婴儿都被转移到一个大围栏里，在那里他们都住在一起直到青春期。因此，差别社会抚养只发生在头6-7个月；此后，MR、PR和SPR都共享相同的物理和社会环境。我们之前的研究表明，PR猴在6个月大的时候比MR猴在短期社会分离期间和之后表现出更大的行为和生物破坏，PR猴在6个月大的时候比MR猴更粘人，玩耍更少，更具攻击性，并且它们也表现出血清素代谢的缺陷（以CSF 5-HIAA的长期低值为指标），SPR猴也是如此。而且他们在大脑许多区域的5-HTT结合水平也明显低于MR受试者。MR猴和PR猴之间的许多差异贯穿了整个童年时期。与NIAAA的同事合作的研究表明，PR和SPR猴子在青少年和青年时期处于欢乐时光的情况下也会消耗更多的酒精。在过去的一年里，我们发表的数据将这些饲养条件的差异扩展到包括BDNF和NGF血浆浓度的发育变化(6)、行为偏侧化(4)、氟尼古丁治疗后的声惊吓反应模式（11）和不同大脑区域的结构差异（15）。最后，我们发现PR猴在第一年的毛发样本中获得的皮质醇水平长期高于MR猴和SPR猴，而在第二年，SPR猴的水平高于其他两个饲养组。

As in previous years, a major focus of this project has been detailed longitudinal study of the behavioral and biological consequences of differential early social rearing, most notably comparing rhesus monkey infants reared by their biological mothers in pens containing adult males and other mothers with same-age infants for their first 6-7 months of life (MR), with monkeys separated from their mothers at birth, hand-reared in the labs neonatal nursery for their first month and then raised in small groups of same-age peers for their next 6 months (PR). In a third standard rearing environment, surrogate-peer rearing (SPR), infants are separated from their mothers and nursery reared just like PR infants, but then at 1 month are housed in individual cages containing an inanimate surrogate mother and additionally are placed in a play cage with 3 other like-reared peers for 2 hours daily for the next are 6 months. At 7 months of age, MR, PR, and SPR infants are all moved into one large pen, where they all live together until puberty. Thus, the differential social rearing occurs only for the first 6-7 months; thereafter MR, PR, and SPR all share the same physical and social environment. We previously demonstrated that PR monkeys cling more, play less, tend to be much more aggressive, and exhibit much greater behavioral and biological disruption during and immediately following short-term social separation at 6 months of age than MR monkeys, and they also exhibit deficits in serotonin metabolism (as indexed by chronically low values of CSF 5-HIAA), as do SPR monkeys, and they also have significantly lower levels of 5-HTT binding throughout many brain regions than do MR subjects. Many of these differences between MR and PR monkeys persist throughout the childhood years. Research in collaboration with colleagues from NIAAA has demonstrated that both PR and SPR monkeys also consume significantly more alcohol when placed in a happy hour situation as adolescents and young adults. This past year we published data extending these rearing condition differences to include developmental changes in plasma concentrations of BDNF and NGF (6), behavioral lateralization (4), acoustic startle response patterns following fluxotine treatment (11), and structural differences in various brain regions (15). Finally, we found that PR monkeys had chronically higher levels of cortisol obtained from hair samples than did MR and SPR monkeys throughout their first year of life, whereas during the second year SPR monkeys had higher levels than the other two rearing groups. During the past year we finished data collection and preliminary analyses for two projects comparing the results of genome-wide scans of blood and tissue samples collected from differentially reared monkeys. First, in collaboration with colleagues from McGill and Wake Forest Universities, we assessed methylation patterns in lymphocyte T cells and pfc obtained from 8 yr-old adult MR and SPR subjects who had been living in the same or comparable physical and social environments since 7 months of age. Over 4,000 genes, i.e. almost 1/5 of the entire genome, showed significant differences in methylation as a function of early experience in both T cells and pfc, with approximately half of the affected genes significantly more methylated in MR-derived samples and the remaining half significantly more methylated in SPR-derived samples. Additionally, there was considerable overlap among the specific genes in T cell and pfc that were differentially methylated: about 30% of the genes showed the same pattern of significant rearing condition differences in both T cells and pfc, whereas approximately 25% of the genes showed exactly the opposite pattern in T cells vs. pfc. Furthermore, there were a substantial number of genes in specific known pathways (e.g., various IL, monoamine transporter, and CRH pathways) that were differentially methylated as a function of differential early experience again in both T cells and pfc. The second project utilizing genome-wide scans of samples obtained from differentially reared monkeys, a collaboration with colleagues from UCLA and the University of Chicago, involved microarray scanning of leukocyte samples obtained from MR, PR, and SPR infants at 7 months of age to determine possible differences in gene expression. As in the afore-mentioned case of differential methylation patters, significant differences in gene expression as a function of differential early experience were found throughout the entire genome. Relative to those of MR infants, genes upregulated in leukocytes from PR infants included the pro-inflammatory cytokine IL8, a diverse array of transcription factors, regulators of cell proliferation, and multiple T cell-associated transcripts. Genes notably suppressed in leukocytes from PR infants included those involved in Type 1 Interferon mediated antiviral responses, several immunoglobulin-encoding genes involved in B cell antibody production, several hematopoietic growth regulators, monocyte-associated gene products, and a variety of memory T cell-related markers. Analyses of gene expression patterns in SPR infants yielded results qualitatively similar to those of PR monkeys, but with differences with MR subject generally quantitatively less pronounced than those of PR subjects, albeit with a number of exceptions. Taken together, these two sets of genome-wide analyses demonstrate that the consequences of differential early experience for monkeys clearly extend to the level of gene methylation patterns and actual expression. Another major focus of recent research for this project has involved characterizing interactions between differential early social rearing and polymorphisms in several candidate genes (G X E interactions), most notably the 5-HTT-LPR gene and the MAO-A gene, for a variety of measures of behavioral and biological functioning throughout development in MR and PR rhesus monkeys. This past year we identified significant G x E interactions involving the 5-HTT-LPR polymorphism among MR infants whose mothers differed significantly in their care-giving patterns. Infants whose mothers exhibited low levels of ventral contact and grooming vocalized and explored less and were more passive in an open field test but only if they carried the "short" 5-HTT-LPR allele. In addition, in collaboration with colleagues from NIAAA and the University of Wurzburg, we identified additional functional polymorphisms in the corticotrophin releasing factor (CRH)2A gene (1), the mu opioid receptor gene (3) , the NPY gene (10), the DRD1 5UTR gene (12), the BDNF gene, and the NOS-1 gene. We were also able to characterized specific G x E interactions with respect to behavioral responses to social separation by juvenile rhesus monkeys for the 5-HTT-LPR and NPY polymorphisms, as well as in several measures of alcohol preference and consumption among young adult monkeys for the CRH, NPY, and DRD1 5UTR polymorphisms (1, 10, 12).