Complex Evolutionary Genetics of Gonadal Differentiation in a Classic Model of Behavior, Astatotilapia burtoni

适当的性腺分化对于有性繁殖物种的适应性是绝对重要的，然而在决定雄性与雌性的机制中，物种之间存在着惊人的多样性。遗传性别决定是一种常见的机制，但人们对新的性别决定基因如何在群体中产生、相互作用和进化知之甚少。从历史上看，基因性别决定的研究主要集中在少数单因素，染色体性别决定系统。最近，基因性别决定在更广泛的物种中被绘制出来，揭示了不同染色体背景下性别决定基因的多样化目录。多基因性决定（Polygenic sex determination， PSD）也在多个分类群中得到证实，在这些分类群中，多种遗传因素直接影响性发育。PSD挑战了关于遗传性别决定系统的传统思维，同时为探索性别决定的进化和发展提供了强有力的策略，包括对具有多种遗传性别决定模式的兄弟姐妹进行比较。换句话说，虽然患有PSD的物种个体发育为雄性或雌性，但可能存在几种雄性和雌性的遗传类型。白托星罗非鱼（Astatotilapia burtoni）利用PSD来确定雄性和雌性的发育，为理解遗传性别决定的进化和发展提供了一个模型。这项工作旨在提供迄今为止最全面的PSD系统分析，使用a . burtoni作为模型系统。该项目将揭示驱动性腺分化和发育的新基因和基因网络，同时产生重要的进化见解。这项研究还将为神经和行为生物学的模型——布氏单胞杆菌提供重要的基因组资源。本科生、研究生和博士后将进行拟议的实验，为他们从事科学事业做准备。此外，通过研究人员和凯南研究员计划的共同指导，K-12教师将获得直接的研究经验，共同开发适用于州教室、地区公共宣传场所和万维网的大规模教育材料。多性别决定位点的分离产生了许多基因型性别，为研究个体内多个性别决定基因的相互作用提供了机会。本研究采用综合的方法，包括基因定位、基因组组装和性染色体注释、比较基因组学和性腺分化过程中的基因网络分析。目的包括多个新的性别决定基因的定位和功能测试，以及追踪新的性别决定等位基因对其所在染色体结构的进化影响，包括连锁基因的功能进化。通过性发育进行基因表达分析将补充这些定位和注释工作，并提供对发育过程中多重基因性开关如何整合的理解。在发育过程中，不同遗传性别之间的基因表达分析也将揭示性腺发育的核心遗传网络，并深入了解遗传网络如何在不负面影响不可或缺的复杂性状的情况下进化。由于burtoni是一个长期存在的行为模型，它为分析第二性特征提供了很好的背景，包括与物种中存在的各种性别决定模式相关的现有行为基因表达数据。

Proper gonadal differentiation is absolutely fundamental to the fitness of sexually reproducing species, yet surprising diversity exists among species in the mechanisms that determines males vs. females. Genetic sex determination is one common mechanism, yet little is known about how novel sex determination genes arise, interact, and evolve in populations. Historically, genetic sex determination research has largely focused on a handful of single-factor, chromosomal sex determination systems. More recently, genetic sex determination has been mapped in a broader set of species, revealing a diverse catalog of sex determination genes in a variety of chromosomal contexts. Polygenic sex determination (PSD) has also been confirmed in multiple taxa, where multiple genetic factors direct sexual development. PSD challenges traditional thinking regarding genetic sex determination systems, while providing powerful strategies to explore the evolution and development of sex determination, including comparisons of siblings with multiple genetic modes of sex determination. In other words, while individuals of species with PSD develop as male or female, several genetic types of males and females may exist. The cichlid fish species Astatotilapia burtoni uses PSD to determine male vs. female development, providing a model to understand the evolution and development of genetic sex determination. This work aims to provide the most comprehensive analysis of a PSD system to date, using A. burtoni as a model system. The project should reveal novel genes and gene networks driving gonadal differentiation and development, while yielding important evolutionary insights. The research will also produce important genome resources for A. burtoni, a model for neural and behavioral biology. Undergraduate and graduate students and postdoctoral fellows will carry out proposed experiments, preparing them for careers in science. Additionally, K-12 teachers will be given direct research experience through co-mentoring by the researchers and the Kenan Fellows Program, together developing educational materials broadly scaled for state classrooms, regional public outreach venues, and the world wide web.Multiple sex determination loci segregate in A. burtoni, producing many genotypic sexes and the opportunity to study the interaction of multiple sex determination genes within individuals. The proposed research uses an integrated approach involving genetic mapping, genome assembly and annotation of sex chromosomes, comparative genomics, and gene network analysis during gonadal differentiation. Aims include mapping and functional testing of multiple novel sex determination genes, and tracing the evolutionary impact of novel sex determination alleles on the structure of chromosomes where they reside, including functional evolution of linked genes. Gene expression analyses through sexual development will supplement these mapping and annotation efforts, and provide understanding of how multiple genetic sex switches are integrated during development. Gene expression analyses among different genetic sexes during development will also reveal core genetic networks underlying gonadal development, and yield insight into how genetic networks evolve without negatively impacting indispensable complex traits. Since A. burtoni is a longstanding behavior model, it provides excellent context for analysis of secondary sexual characteristics, including existing behavioral gene expression data, in relation to the various modes of sex determination present in the species.