Natural mutagenesis of human genomes by endogenous retrotransposons

描述(由申请人提供)： 可转座基因元件(TES)占人类基因组的44%。人类TE，如L1元素，当它们“跳入”基因时会导致疾病，已有数十个导致疾病的TE插入人类被记录在案。人们普遍认为TE动员主要发生在人类生殖系。然而，最近的几条证据表明，人类的L1元件也在体细胞中转座。至少在两种类型的人类肿瘤中观察到了体细胞L1插入，这表明这种插入可能会导致疾病状态，包括癌症。在这项提案中，我们将研究人类生殖系L1动员与体细胞L1动员的相对水平。在目标1中，我们将使用我们最近开发的转座子序列技术来检查从健康美国人那里获得的纸巾面板中的L1插入。通过研究来自同一个体的多个组织中L1的动员，我们将建立健康美国人种系L1插入与体细胞L1插入的相对丰度。我们还将寻找L1动员的RNA携带机制的证据，该机制在小鼠中产生镶嵌体细胞插入，在人类中也可能产生这样的插入。在目标2中，我们将检查正常/肿瘤组织对，以确定生殖系和体细胞L1插入是否有助于推动人类肿瘤的形成。我们的实验室最近发现，L1在人类肺癌中被高频动员，我们怀疑一些新的L1插入促进了肿瘤的发生。我们将在目标2中直接验证这一假设。我们还将确定其他类型的肿瘤是否存在体细胞L1动员。在目标3中，我们将研究在人类中产生新的L1插入的源元素。我们将确定来源元素拷贝数是否影响人类的L1突变和癌症风险。最后，我们将检验人类肺癌中来源元素受甲基化控制的假设。总之，这些研究将极大地扩展我们对人类L1突变的知识，并将为L1突变如何影响人类健康提供重要的新见解。

DESCRIPTION (provided by applicant): Project Summary Transposable genetic elements (TEs) occupy 44% of the human genome. Human TEs such as the L1 element can cause diseases when they "jump" into genes, and several dozen disease-causing TE insertions have been documented in humans. It has been widely assumed that TE mobilization occurs primarily in the human germline. However, several recent lines of evidence indicate that the human L1 element also transposes in somatic cells. Somatic L1 insertions have been observed in at least two types of human tumors, suggesting that such insertions may produce disease states, including cancers. In this proposal, we will examine the relative levels of germline vs. somatic L1 mobilization in humans. In Aim 1, we will use our recently developed transposon-seq technologies to examine L1 insertions in a tissue panel obtained from healthy Americans. By studying L1 mobilization in multiple tissues from the same individuals, we will establish the relative abundances of germline vs. somatic L1 insertions in healthy Americans. We also will seek evidence for the RNA carryover mechanism of L1 mobilization, which produces mosaic somatic insertions in mice and may also produce such insertions in humans. In Aim 2, we will examine normal/tumor tissue pairs to determine whether germline and somatic L1 insertions help to drive tumor formation in humans. Our laboratory recently found that L1 is mobilized at high frequencies in human lung tumors, and we suspect that some of the new L1 insertions fuel tumorigenesis. We will directly test this hypothesis in Aim 2. We also will determine whether somatic L1 mobilization occurs in other tumor types. In Aim 3, we will study source elements that produce new L1 insertions in humans. We will determine whether source element copy number influences L1 mutagenesis and cancer risk in humans. Finally, we will test the hypothesis that source elements are controlled by methylation in human lung cancers. Together, these studies will greatly expand our knowledge of L1 mutagenesis in humans and will provide major new insights on how L1 mutagenesis impacts human health.