Evolution of piRNAs and germline transposon control in Drosophila

描述(申请人提供)：转座元件(TES)是自私的遗传实体，可以迅速横扫种群，在真核基因组中达到高拷贝数。50多种人类遗传病与TE插入有关，即TE介导的染色体重排，在人类群体中反复发生。此外，TES的错误调节与肿瘤的发生和发展有关，这表明TES抑制在癌症耐药中起着关键作用。TE活性产生的有害突变对宿主的抑制具有很强的选择性。最近对Piwi相互作用RNA(PiRNA)途径的研究激增，发现这些蛋白质与TE衍生的小RNA(PiRNAs)协同作用，使雄性和雌性生殖系中的TE沉默。PiRNA途径在后生动物中具有保守的功能，但令人惊讶的是，许多piRNA蛋白是正选择的直接靶标。利用模型系统果蝇，我提出的研究将阐明蛋白质和RNA在piRNA介导的TE抑制的进化变化中的贡献。具体地说，我将：1)检测黑腹盘藻和模拟盘藻种间杂交中的piRNA途径功能。在种间杂交中观察到的异常表型经常表明潜在生物学过程或途径的快速进化成分。通过比较种间杂交种和纯物种之间的piRNA蛋白定位、piRNA池和生殖系TE表达，我将揭示在功能上存在分歧的piRNA途径的某些方面。2)研究黑腹葡萄球菌和拟青霉之间的适应性差异，Aubergine是一个关键的piRNA途径蛋白。我将使用异源转基因来区分PiRNA蛋白Aubergine的特定功能，这些功能一直是正向选择的目标。这种对茄子碱的定向分析将有助于阐明选择性力量(S)，这是整个piRNA途径中适应性蛋白质进化的基础。这项拟议的研究将加深我们对自私的转座元件是如何被宿主控制的理解。由于这些元素的活性直接导致了几种人类遗传病的发生、发病或发展，因此这一知识对于产生更有效的治疗和预防至关重要。

DESCRIPTION (provided by applicant): Transposable elements (TEs) are selfish genetic entities that can rapidly sweep through populations, reaching high copy-number in eukaryotic genomes. More than 50 human genetic diseases are associated with TE insertions, or TE-mediated chromosomal rearrangements that occur recurrently in human populations. Misregulation of TEs, furthermore, is associated with tumorigenesis and tumor progression, suggesting a critical role for TE suppression in cancer resistance. The deleterious mutations that arise from TE activity exert strong selection for suppression by the host. A recent explosion of research on the Piwi- interacting RNA (piRNA) pathway has made the exciting discovery that these proteins act in concert with TE-derived small RNAs (piRNAs) to silence TEs in male and female germlines. The piRNA pathway has a conserved function across metazoa, yet surprisingly many piRNA proteins are the direct targets of positive selection. Using the model system Drosophila, my proposed research will elucidate both the protein and RNA contributions to evolutionary changes in piRNA mediated TE suppression. Specifically, I will: 1) Examine piRNA pathway function in D. melanogaster and D. simulans interspecific hybrids. Aberrant phenotypes observed in interspecific hybrids frequently indicate rapidly evolving components of the underlying biological process or pathway. By comparing piRNA protein localization, piRNA pools, and germline TE expression between interspecific hybrids and pure species, I will reveal aspects of the piRNA pathway that have diverged functionally. 2) Examine adaptive divergence of Aubergine, a critical piRNA pathway protein, between D. melanogaster and D. simulans. I will employ heterologous transgenics to distinguish specific functions of the piRNA protein Aubergine that have been targets of positive selection. This directed analysis of aubergine will help elucidate the selective force(s) that underlie adaptive protein evolution throughout the piRNA pathway. The proposed research will enhance our understanding of how selfish transposable elements are controlled by their hosts. Because activity of these elements contribute directly to the origin, onset, or progression of several human genetic diseases, this knowledge is critical to generating more effective treatment and prevention