Molecular Genetic Mechanisms of Gonad Development in Zebrafish

该项目的长期目标是了解控制脊椎动物性腺发育的遗传机制。性腺发育的一般形态和内分泌学在脊椎动物中保存得很好，但决定性腺是变成卵巢还是睾丸的遗传途径在任何脊椎动物中都不是很清楚。由于环境污染物，如一些多氯联苯(PCbs)，可能会干扰鱼类、鸟类和哺乳动物(包括人类)的性腺发育和内分泌功能，因此了解调控性腺生长和分化的机制变得越来越重要。由此产生的对生殖生理的影响对保护野生动物种群和人类生殖健康具有重要意义。虽然性腺发育的基本途径可能在脊椎动物之间是相同的，但不同的脊椎动物谱系有不同的方式将途径转向卵巢或睾丸。一些物种有很强的性别决定基因，比如哺乳动物，Y染色体上一种名为SRY的特定基因决定性腺发育。其他物种有很强的环境性别决定，例如一些海龟，胚胎孵化的温度调节性腺的性别。对斑马鱼的研究表明，假设多种基因类型因素，在受环境影响较小的情况下，导致个体的性腺表达雄激素合成酶和雄激素受体基因，或者表达雌激素合成酶基因和雌激素受体基因；然后，这些内分泌因素可能控制性腺的性别、初级生殖细胞和次级性征。这一假设将通过三种方式进行验证：特定目标1。拟议的实验将调查该模型预测的在斑马鱼性腺早期发育中发挥作用的基因的表达模式。具体目标2：拟议的实验将使用性类固醇及其抑制剂和各种突变扰乱性腺发育，并调查基因表达模式是否按照模型预测的方式发生变化。具体目标3：拟议的实验将确定与斑马鱼性别分化相关的数量性状基因座(QTL)。图谱位置将与在特定目标1中分离的基因以及与哺乳动物基因组进行比较，以建议斑马鱼性腺分化的候选基因。实现特定的目标将导致对斑马鱼性腺发育的控制机制有更深入的了解，并将指向影响该物种性别决定的遗传位点。由此产生的对斑马鱼性别决定的基本性质的更坚定的理解将使未来设计突变方案来分离对脊椎动物性别决定重要的新基因。

The long-term objective of this project is to understand the genetic mechanisms that control gonad development in animals with backbones. The general morphology and endocrinology of gonad development are well conserved among vertebrates, but the genetic pathway that determines whether a gonad becomes an ovary or a testis is not well understood in any vertebrate. Understanding the mechanisms that regulate gonad growth and differentiation takes on increasing significance as environmental pollutants, such as some polychlorinated biphenyls (PCBs), may disturb gonad development and endocrine function in fish, birds, and mammals, including humans. The resulting effects on the physiology of reproduction are significant for the preservation of wildlife populations and for human reproductive health. Although the underlying pathway of gonad development may be shared among vertebrates, different vertebrate lineages have different ways of diverting the pathway towards an ovary or a testis. Some species have strong genotypic sex determination, such as mammals in which a specific gene called SRY on the Y-chromosome specifies gonad development. Other species have strong environmental sex determination, such as some turtles in which the temperature of embryo incubation regulates gonad sex. Investigations on zebrafish suggest the hypothesis that multiple genotypic factors, with a minor influence from the environment, cause an individual's gonads to express either genes for androgen synthesizing enzymes and androgen receptor, or express genes for estrogen synthesizing enzymes and estrogen receptor; these endocrine factors may then control the sex of the gonad, primary germ cells, and secondary sex characteristics. This hypothesis will be tested in three ways: Specific Aim 1. The proposed experiments will investigate the expression patterns of genes predicted by the model to play a role in early gonadal development of the zebrafish. Specific Aim 2: The proposed experiments will perturb gonad development using sex steroids and their inhibitors, and various mutations, and investigate whether gene expression patterns change in ways predicted by the model. Specific Aim 3: The proposed experiments will identify quantitative trait loci (QTLs) associated with sex differentiation in zebrafish. Map locations will be compared to those of genes isolated in Specific Aim 1 and with mammalian genomes to suggest candidate genes for gonad differentiation in zebrafish. Achieving the specific aims will result in a more robust understanding of the control mechanisms of gonad development in zebrafish, and will point to genetic loci that influence sex determination in this species. The resulting firmer understanding of the basic nature of sex determination in zebrafish will permit the future design of mutagenesis protocols to isolate novel genes important for vertebrate sex determination.