A Model of Behavioral Evolution from Genotype to Phenotype

行为的进化依赖于基因组水平的变化，但很少有脊椎动物的行为可以直接追溯到特定的基因序列。在这个项目中，研究小组将使用自然产生的动物模型——白喉麻雀，以具体的方式将行为与基因序列联系起来。在这个物种中，50%的鸟有一条不寻常的染色体，这使它们更具攻击性。因此，染色体是了解基因表达的个体差异如何导致行为差异的绝佳工具。该研究小组最近发现，具有不寻常染色体的动物在大脑的某些区域有更高的类固醇受体表达。在这里，研究小组确定了遗传机制，在分子水平上，导致一些鸟类比其他鸟类表达更多的这些受体。通过这样做，研究小组证明了对类固醇激素的反应是如何在基因组中编码的。这项工作本身很适合教育和推广，因为它说明了一个普通的后院鸟的基本生物学概念。因此，它以一种学生易于理解的方式整合了典型生物学课程的多个单元。高中教师被招募来参与这项研究，并制定有关遗传学、激素、大脑解剖学和社会行为的课程计划。PI还在实验室指导高中生、本科生和研究生。在埃默里大学，超过75%的PI学员是代表性不足的少数民族或女性。行为的进化依赖于基因组水平的变化，但很少有脊椎动物的行为可以直接追溯到基因序列。在白喉雀（斑鸠）中，染色体倒置分离具有攻击性行为表型，这为以具体方式将基因和行为联系起来提供了难得的机会。这种倒置捕获了编码雌激素受体α (erα)的基因ESR1。研究小组最近发现，erα在大脑中的局部表达取决于是否存在反转，erα表达的变化预测了基因型对领土攻击的影响。该研究小组使用体外报告基因测定、亚硫酸盐测序和等位基因特异性定量PCR来鉴定导致erα表达变异的遗传和表观遗传机制。选择性erα配体对每种基因型动物攻击行为的影响被用来确定erα表达和功能的变化是否导致领土攻击的变化。由于研究小组使用的组织来自于具有行为特征的自由生活动物，因此同一动物的分子和行为水平被整合在一起，从而形成新的联系。结果提供了一个跨学科的，综合模型遗传变化如何导致表型变化。这项工作本身很适合教育和推广，因为它说明了一个普通的后院鸟的基本生物学概念。

The evolution of behavior relies on changes at the level of the genome, yet few vertebrate behaviors can be traced directly to specific gene sequences. In this project, the research team will use a naturally-occurring animal model, the white-throated sparrow, to connect behavior with gene sequence in a concrete way. In this species, 50% of the birds have an unusual chromosome that makes them more aggressive. The chromosome is therefore an excellent tool for understanding how individual variation in gene expression contributes to variation in behavior. The team recently showed that animals with the unusual chromosome have higher expression of a type of steroid receptor in some areas of the brain. Here, the research group determines the genetic mechanisms, at the molecular level, that cause some birds to express more of these receptors than others. In so doing, the team demonstrates how responsiveness to steroid hormones is encoded in the genome. The work lends itself well to education and outreach because it illustrates basic biological concepts in a common backyard bird. Thus, it serves to integrate multiple units of a typical biology course in a way that is accessible to students. High school teachers are recruited to participate in the research and to develop lesson plans about genetics, hormones, brain anatomy, and social behavior. The PI also mentors high school students, undergraduates, and graduate students in the lab. More than 75% of the PI's mentees at Emory have been underrepresented minorities or women. The evolution of behavior relies on changes at the level of the genome, yet few vertebrate behaviors can be traced directly to genetic sequences. In the white-throated sparrow (Zonotrichia albicollis), a chromosomal inversion segregates with an aggressive behavioral phenotype, offering a rare opportunity to connect genes and behavior in a concrete way. The inversion has captured the gene ESR1, which encodes estrogen receptor alpha (ERalpha). The research team recently showed that the local expression of ERalpha in the brain depends on the presence or absence of the inversion and that variation in ERalpha expression predicts the effect of genotype on territorial aggression. The research group uses in vitro reporter assays, bisulfite sequencing, and allele-specific quantitative PCR to identify the genetic and epigenetic mechanisms that contribute to variation in expression of ERalpha. The effects of selective ERalpha ligands on aggressive behavior in animals of each genotype is used to determine whether variation in ERalpha expression and function is causal for variation in territorial aggression. Because the team uses tissue from behaviorally characterized, free-living animals, the molecular and behavioral levels are integrated in the same animals to allow novel connections. The results provide an interdisciplinary, integrated model of how genetic change leads to phenotypic change. The work lends itself well to education and outreach because it illustrates basic biological concepts in a common backyard bird.