Mechanisms of Sex Determination in Zebrafish

斑马鱼性别决定机制

• 批准号: 8517138
• 负责人: JOHN H. POSTLETHWAIT
• 金额: $ 23.93万
• 依托单位: UNIVERSITY OF OREGON
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8517138
• 关键词: Address; Adolescent; Affect; Aromatase; Biological; Cell Count; Cell Death; Cues; DNA Repair; Developed Countries; Development; Disease; Environment; Environmental Risk Factor; Enzymes; Equilibrium; Estrogens; Female; Fishes; Gene Expression Profile; Genes; Genetic; Genotype; Germ Cells; Gonadal structure; Hormones; Human; Individual; Investigation; Learning; Link; Malignant neoplasm of testis; Mammals; Maps; Meiosis; Methodology; Modeling; Molecular Genetics; Mutation; Nature; Oocytes; Organ; Orthologous Gene; Ovary; Pathway interactions; Pattern; Phenotype; Polycystic Ovary Syndrome; Population; Pregnancy; Production; Receptor Gene; Reproductive Health; Role; Sex Bias; Sex Differentiation; Sexual Development; Siblings; Signal Transduction; Somatic Cell; Sterility; Steroid Receptors; Structure of primordial sex cell; Supporting Cell; Syndrome; System; Temperature; Testicular Dysgenesis Syndrome; Testing; Testis; Testosterone; Tretinoin; Uterus; Vertebrates; Woman; Work; Y Chromosome; Zebrafish; gene function; genetic sex determination; genome sequencing; genome-wide; in utero; innovation; insight; male; men; mutant; public health relevance; reproductive; research study; sex; sex determination; social; tool; trait

DESCRIPTION (provided by applicant): Human reproductive health depends on gonad development, which can be adversely affected in utero by unknown genetic and environmental factors. In mammals, the Y-chromosome gene SRY initiates an incompletely understood network that directs the gonad to become a testis rather than an ovary. In nonmammalian vertebrates, other genes in the network determine sex, and in some species, environmental factors such as temperature or social cues can bias sex development. This project's broad objective is to learn how genetic factors, interacting with the environment, can tip the balance towards one sex or another. Work focuses on zebrafish, a genetically tractable vertebrate in which sex determination can be easily tipped in one direction or the other. The zebrafish gonad initially develops as a bipotential organ, with a few primordial germ cells in all juveniles initially developing as oocytes. In some individuals, oocytes die and the gonad becomes a testis; in others, oocytes survive and the gonad becomes an ovary. A key question is, what genetic or environmental signals cause presumptive oocytes to die in some individuals and to survive in others? An important tool to probe this question is a recessive mutation in fancl that causes female-to-male sex reversal. Preliminary experiments show excess cell death in homozygous mutant juvenile gonads and suggest the hypothesis that 1) environmental and genetic factors affect oocyte survival in juveniles, and thereby 2) alter the strength of an oocyte-derived signal that promotes, in surrounding somatic cells, 3) the production of aromatase, the enzyme that 4) converts testosterone to estrogen, which preserves oocytes and biases the gonad toward a female fate; 5) with insufficient quantities of the hypothesized oocyte-derived signal, the gonad becomes a testis. Aim 1 is to identify genetic factors linked to sex phenotype in F2 mapping crosses. Aim 2 is to conduct a genome-wide search for genes expressed sex specifically by comparing transcriptomes of all-male populations of zebrafish and medaka, a species with genetic sex determination, to female-containing sibling populations (Aim 2a) and to investigate expression patterns of candidate sex determination genes, steroid receptor genes, and extracell signaler genes (Aim 2b). Aim 3 is to test additional components of the hypothesis by learning whether blocking the retinoic acid signal for entry into meiosis can cause sex reversal (Aim 3a) and whether primordial germ cell number controls sex development in zebrafish and medaka (Aim 3b). The proposed work has significance for it's potential to identify new genes and new gene functions by comparing a vertebrate with a delicate balance for sex differentiation (zebrafish) to one with a known genetic male determinant (medaka). Results will contribute to a better understanding of the molecular genetic nature of the vertebrate sex-balance mechanism, and thus contribute to our understanding of possible mechanisms for the current increase in human reproductive disease, including testicular dysgenesis syndrome and polycystic ovary syndrome increasingly observed in developed countries. PUBLIC HEALTH RELEVANCE: Understanding the biological mechanisms that tip the balance of sex determination between male and female is essential to understand recent increases in human reproductive disorders originating in the womb, including sterility and testis cancer in men and polycystic ovary syndrome in women. Certain genetic make- ups may be especially prone to disruption. Investigations of vertebrate species with finely balanced sex determination mechanisms may provide insight into how environmental and genetic factors tip the sex determination balance in humans. Although many features of zebrafish gonad development are similar to those in humans, zebrafish sex determination is more labile; furthermore, in zebrafish, genetic tools are available to dissect the mechanisms of sex determination, which should identify new genes and new gene functions relevant for human reproductive health.

描述（由申请人提供）：人类生殖健康取决于性腺发育，性腺发育可能会在子宫内受到未知遗传和环境因素的不利影响。在哺乳动物中，Y 染色体基因 SRY 启动了一个不完全理解的网络，指导性腺变成睾丸而不是卵巢。在非哺乳动物脊椎动物中，网络中的其他基因决定性别，而在某些物种中，温度或社会线索等环境因素可能会影响性别发育。该项目的总体目标是了解遗传因素如何与环境相互作用，使平衡向一种性别倾斜。工作重点是斑马鱼，这是一种基因上易于驯化的脊椎动物，其性别决定可以很容易地向一个方向或另一个方向倾斜。斑马鱼性腺最初发育为双能器官，所有幼鱼中的一些原始生殖细胞最初发育为卵母细胞。在某些个体中，卵母细胞死亡，性腺变成睾丸；在另一些情况下，卵母细胞存活下来，性腺变成卵巢。一个关键问题是，哪些遗传或环境信号导致某些个体的卵母细胞死亡，而另一些个体的卵母细胞却存活下来？探究这个问题的一个重要工具是 fancl 中的隐性突变，它会导致女性向男性的性别逆转。初步实验显示纯合突变幼年性腺中细胞死亡过多，并提出以下假设：1) 环境和遗传因素影响幼年卵母细胞的存活，从而 2) 改变卵母细胞衍生信号的强度，促进周围体细胞的生长，3) 芳香酶的产生，这种酶 4) 将睾酮转化为雌激素，从而保护卵母细胞 并使性腺偏向女性命运； 5）如果假设的卵母细胞衍生信号数量不足，性腺就会变成睾丸。目标 1 是在 F2 作图杂交中鉴定与性别表型相关的遗传因素。目标 2 是通过将斑马鱼和青鳉（一种具有遗传性别决定的物种）的全雄性种群的转录组与包含雌性的兄弟种群的转录组进行比较，对表达性别的基因进行全基因组搜索（目标 2a），并研究候选性别决定基因、类固醇受体基因和细胞外信号基因的表达模式（目标 2b）。目标 3 是通过了解阻断进入减数分裂的视黄酸信号是否会导致性逆转（目标 3a）以及原始生殖细胞数量是否控制斑马鱼和青鳉的性别发育（目标 3b）来测试该假设的其他组成部分。这项拟议的工作具有重要意义，因为通过将性别分化具有微妙平衡的脊椎动物（斑马鱼）与具有已知遗传雄性决定因素的脊椎动物（青鳉鱼）进行比较，有可能识别新基因和新基因功能。研究结果将有助于更好地了解脊椎动物性别平衡机制的分子遗传性质，从而有助于我们了解当前人类生殖疾病增加的可能机制，包括在发达国家越来越多地观察到的睾丸发育不全综合征和多囊卵巢综合征。 公共卫生相关性：了解平衡男性和女性性别决定平衡的生物学机制对于了解起源于子宫的人类生殖疾病（包括男性不育症和睾丸癌以及女性多囊卵巢综合症）的近期增加至关重要。某些基因组成可能特别容易受到破坏。对具有精细平衡的性别决定机制的脊椎动物物种的研究可能有助于了解环境和遗传因素如何影响人类的性别决定平衡。尽管斑马鱼性腺发育的许多特征与人类相似，但斑马鱼的性别决定更加不稳定。此外，在斑马鱼中，遗传工具可用于剖析性别决定机制，从而识别与人类生殖健康相关的新基因和新基因功能。