Neuroscience and Behavior Unit, California National Primate Research Center, University of California, Davis, California, USA.
Department of Psychology, University of California, Davis, California, USA.
Am J Primatol. 2022 Jun;84(6):e23374. doi: 10.1002/ajp.23374. Epub 2022 Mar 24.
Temperament is a construct whose manifestations are quantifiable from an early age, and whose origins have been proposed as "biological." Our goal was to determine whether maternal rank and infant genotype are associated with five measures of temperament in 3- to 4-month old rhesus monkeys (Macaca mulatta), all of whom were born and reared by their mothers in large, outdoor, half-acre cages. Maternal rank was defined as the proportion of animals outranked by each female, and the two genes of interest to us were monoamine oxidase and serotonin transporter, both of which are polymorphic in their promoter regions (MAOA-LPR and 5-HTTLPR, respectively), with one allele of each gene considered a "plasticity" allele, conferring increased sensitivity to environmental events. Our large sample size (n = 2014-3140) enabled us to examine the effects of individual genotypes rather than combining genotypes as is often done. Rank was positively associated with Confident temperament, but only for animals with the 5-repeat allele for MAOA-LPR. Rank had no other effect on temperament. In contrast, genotype had many different effects, with 5-HTTLPR associated with behavioral inhibition, and MAOA-LPR associated with ratings-based measures of temperament. We also examined the joint effect of the two genotypes and found some evidence for a dose-response: animals with the plasticity alleles for both genes were more likely to be behaviorally inhibited. Our results suggest phenotypic differences between animals possessing alleles for MAOA-LPR that show functional equivalence based on in vitro tests, and our data for 5-HTTLPR revealed differences between short/short homozygotes and long/short heterozygotes, strongly suggesting that combining genotypes for statistical analysis should be avoided if possible. Our analysis also provides evidence of sex differences in temperament, and, to our knowledge, the only evidence of differences in temperament based on specific pathogen-free status. We suggest several directions for future research.
气质是一种可以从婴儿早期就进行量化表现的结构，其起源被认为是“生物性的”。我们的目标是确定母猴等级和婴儿基因型是否与 3-4 月龄恒河猴的五种气质测量指标相关，所有这些猴子都是在母亲的户外半英亩大的笼子里出生和长大的。母猴等级的定义是每个雌性动物被其他动物超越的比例，我们感兴趣的两个基因是单胺氧化酶和血清素转运体，它们在启动子区域都存在多态性（分别为 MAOA-LPR 和 5-HTTLPR），每个基因的一个等位基因被认为是“可塑性”等位基因，增加了对环境事件的敏感性。我们的大样本量（n=2014-3140）使我们能够检查个体基因型的影响，而不是像通常那样将基因型组合起来。等级与自信气质呈正相关，但仅适用于 MAOA-LPR 5 重复等位基因的动物。等级对气质没有其他影响。相比之下，基因型有许多不同的影响，5-HTTLPR 与行为抑制有关，MAOA-LPR 与基于评级的气质测量有关。我们还检查了两种基因型的联合效应，发现了一些剂量反应的证据：具有两种基因可塑性等位基因的动物更有可能表现出行为抑制。我们的结果表明，MAOA-LPR 等位基因的动物之间存在表型差异，这些差异基于体外测试显示功能等效性，我们关于 5-HTTLPR 的数据显示短/短纯合子和长/短杂合子之间的差异，强烈表明如果可能的话，应该避免对基因型进行统计分析的组合。我们的分析还提供了气质性别差异的证据，并且据我们所知，这是唯一基于无特定病原体状态的气质差异的证据。我们提出了未来研究的几个方向。
