Transposable element mobilization during spermatogenesis in Drosophila

摘要 转座子是一种可移动的DNA片段，它构成了真核生物基因组的很大比例，包括 大约45%的人类基因组和30%的苍蝇基因组。虽然大多数转座子已经失去了 跳到基因组中的新位置，每个有机体中的几个保持动员的能力。新转座子 如果插入是在生殖系细胞中产生的，那么插入就特别重要。生殖系插入是 随后，它们存在于有机体的每个细胞中，并可遗传给后代。 因此，生殖系细胞使用多层机制来抑制转座子。这些压制机制 是在很大程度上抑制生殖细胞发育成成熟卵子和精子的转座子所必需的 因为转座子的活性可能会导致不育症。由于这些抑制机制，如piRNA 通路使转位事件如此罕见，它们很难被检测到，我们也很难理解它们是如何 在生殖系中动员的转座子仍然不完整。也就是说，转座子用来 产生新的插入，他们在精子成熟期间进行新插入的时间点是 未定义。为了在雄性生殖系中找到潜在的活性转座子，我对来自 果蝇睾丸中的piRNA途径耗尽。干扰转座子允许的piRNA途径 并发现游牧转座子在睾丸中产生的环状DNA最多。环状DNA 是LTR逆转录转座子的转座中间体，它的存在可能预示着 转座子仍然能够进行新的插入。知道Momad是最活跃的转座子 在雄性生殖系中，我建议使用这个转座子来研究转座子如何在生殖系中移动。我 转座子利用ALT-EJ DNA修复途径中的宿主因子实现阶段特异性的假设 精子发生过程中的动员。我将利用循环游牧民DNA作为读数来寻找所需的宿主因子 对于它的制作和换位，记者为游牧民族准确识别出它何时会产生新的插入。

Abstract Transposons are mobile pieces of DNA that comprise significant proportions of eukaryotic genomes, including around 45% of the human genome and 30% of the fly genome. While most transposons have lost the ability to jump into new locations in the genome, several in each organism maintain the ability to mobilize. New transposon insertions are particularly consequential if they are generated in germline cells. Germline insertions are subsequently present in every cell of the organism they develop into and can be passed on to future generations. Thus, germline cells employ multilayered mechanisms to repress transposons. These repressive mechanisms are essential to largely suppress transposon for development of germline cells into mature eggs and sperm because transposon activity can contribute to sterility. Since these repressive mechanisms like the piRNA pathway render transposition events so rare, they are difficult to detect and our understanding of how transposons mobilize in the germline remains incomplete. Namely, the host factors that transposons employ to generate new insertions and the time point when they make new insertions during sperm maturation are undefined. To find potentially active transposons in the male germline, I have sequenced circular DNA from Drosophila testes with the piRNA pathway depleted. Disrupting the piRNA pathway allowed for transposon activation and revealed that the nomad transposon generates the most circular DNA in the testes. Circular DNA is a transposition intermediate of LTR retrotransposons and its presence can indicate the likelihood of a transposon being able to still make new insertions. With the knowledge that nomad is the most active transposon in the male germline, I propose to use this transposon to study how transposons mobilize in the germline. I hypothesize that transposons utilize host factors from the alt-EJ DNA repair pathway to achieve stage specific mobilization during spermatogenesis. I will utilize circular nomad DNA as a readout to find host factors required for its production and transposition reporters for nomad to precisely identify when it generates new insertions.