Polyploidization, gene dosage, and the evolution of hormonal phenotypes

类固醇激素(肾上腺糖皮质激素和性腺类固醇)已经在生态学和行为学的背景下得到了广泛的研究，因为这些激素在调节对生存和繁殖至关重要的表型变化方面发挥着不可或缺的作用。从这类研究中出现的最引人注目的发现之一是，关于这些激素的调节存在多样性。例如，这些激素的循环水平和糖皮质激素升高抑制性腺类固醇产生的程度在脊椎动物物种中都是高度不同的。这项研究检测了二倍体-多倍体树蛙物种复合体中的肾上腺糖皮质激素和性腺类固醇，以了解多倍化(基因组复制)是如何导致这种变异的。多倍化有望推动激素调节的改变，因为基因拷贝数的相关变化可以引入新的基因表达模式和/或增加突变率，从而改变控制激素水平和激素相互作用的基因产物的表达。这项拟议的研究与理解激素调节的广泛变异模式有关，因为多倍体是脊椎动物的历史特征，也是现存脊椎动物基因拷贝数变异的主要来源。这项研究将与赞助机构的暑期研究计划相结合，从STEM领域服务不足的群体中招募至少8名高中生参与该项目。该项目还包括培训本科生和研究生以及一名博士后助理，他们将与高中生和主要调查人员密切合作，通过同行指导进行交叉培养培训和职业发展。肾上腺糖皮质激素和性腺类固醇的循环水平，以及这些激素之间的相互作用，在不同脊椎动物之间存在显著差异，但导致这种差异的遗传基础却鲜为人知。这项研究考察了多倍体的内分泌调节，以了解基因拷贝数(即基因剂量)的相关变化如何促成这种非凡的多样性。多倍化和相关的基因剂量变化可以通过改变基因表达模式和/或增加基因突变率来显著影响表型的进化，但多倍化如何影响激素调节的修饰在很大程度上仍未得到研究。这项拟议的工作研究了三个自然四倍体灰树蛙血统及其二倍体祖先中肾上腺糖皮质激素和性腺类固醇的调节，以了解多倍化如何影响内分泌控制。通过研究激素水平和下丘脑-垂体-肾上腺/肾间轴和下丘脑-垂体-性腺轴之间的相互作用，比较类固醇受体和结合蛋白的表达水平和序列，以及检测二倍体和四倍体树蛙中类固醇结合蛋白的水平和动力学，本研究将阐明多倍化过程中基因剂量的变化如何影响激素调节。这项研究的更广泛的影响包括不同的学生参与内分泌学、遗传学和神经科学的现场和基于实验室的跨学科研究。农村高中生将在夏季被招募参与研究，他们的经历的影响将被评估。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Steroid hormones (adrenal glucocorticoids and gonadal steroids) have been extensively studied in the context of ecology and behavior because of the integral roles these hormones play in mediating phenotypic changes that are crucial for survival and reproduction. One of the most striking findings emerging from such studies is the diversity that exists with respect to regulation of these hormones. For example, circulating levels of these hormones and the extent to which elevated glucocorticoids suppress the production of gonadal steroids are both highly variable across vertebrate species. This study examines adrenal glucocorticoids and gonadal steroids in a diploid-polyploid treefrog species complex to understand how polyploidization (duplication of the genome) contributes to this variation. Polyploidization is expected to drive modifications in hormonal regulation because associated changes in gene copy number can introduce novel gene expression patterns and/or increase rates of mutation that alter the expression of gene products governing hormone levels and hormonal interactions. The proposed study is relevant to understanding broad patterns of variation in hormonal regulation because polyploidy is a historical feature of vertebrates and a major source of variation in gene copy number in living vertebrates. This research will be integrated with summer research programs at the sponsoring institution to recruit at least eight high-school students from groups underserved in STEM fields to participate in the project. The project also involves training of undergraduate and graduate students and one post-doctoral associate, who will work closely with one another, high- school students, and the principal investigators, to cross-foster training and career development through peer mentoring. Circulating levels of adrenal glucocorticoids and gonadal steroids, and interactions between these hormones, are remarkably variable across vertebrates, but the genetic underpinnings giving rise to this diversity are poorly understood. This study examines endocrine regulation in polyploids to understand how associated changes in gene copy number (i.e., gene dosage) contribute to this extraordinary diversity. Polyploidization and associated changes in gene dosage can dramatically influence the evolution of the phenotype by altering gene expression patterns and/or by increasing gene mutation rates, but how polyploidization contributes to modifications in hormonal regulation remains largely unstudied. The proposed work examines regulation of adrenal glucocorticoids and gonadal steroids in three natural tetraploid gray treefrog lineages and their diploid ancestor to understand how polyploidization impacts endocrine control. By characterizing hormone levels and interactions between the hypothalamic-pituitary-adrenal/interrenal and hypothalamic-pituitary-gonadal axes, comparing steroid receptor and binding protein mRNA expression levels and sequences, and examining steroid binding protein levels and kinetics in diploid and tetraploid treefrogs, this study will elucidate how changes in gene dosage through polyploidization impact hormonal regulation. The broader impacts of this research include diverse student involvement in field and lab-based interdisciplinary research in endocrinology, genetics, and neuroscience. Rural high-school students will be recruited to participate in the research during summers and the impact of their experiences will be assessed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.