Retrotransposition in Health and Disease

 描述(由申请人提供) 尽管我们过去认为所有的逆转录转座都发生在人类的生殖系中，但在过去的10年里，体细胞逆转录转座，特别是LINE1(L1s)的逆转座，已经变得明显，至少在大脑和上皮性癌症中是如此。许多研究小组已经在神经前体细胞和成人大脑中显示出逆转位。同样，包括我们自己在内的许多组在胃肠道癌症中显示出显著的逆转位。我们研究的一个关键发现是，大多数胃肠道癌症的L1插入发生在癌症发展的非常早期。事实上，在正常细胞中发现了一些低浓度的插入片段(仅通过套式聚合酶链式反应检测到)，但在癌症中它们基本上变成了克隆(通过传统的聚合酶链式反应检测到)。在这项申请中，我们努力回答该领域的两个大问题。首先，在大脑以外的成人躯体组织中是否发生了显著的逆转位，如果是的话， 频率是多少？在这个目标中，我们将研究肿瘤附近单个正常细胞中的L1插入，以找出正常细胞中已经存在的肿瘤中插入的部分。我们将确定在正常细胞和肿瘤细胞中逆转录转座率哪个更高。我们还将研究单个与癌症无关的正常细胞和来自不同器官的插入频率，以确定是否某些组织类型比其他组织类型有更大的逆转位倾向。第二个大问题是：L1体细胞逆转位在癌症的病因学中有任何重要作用吗？我们需要确定是否可以通过删除在癌症相关基因中发现的体细胞L1插入来将细胞表型转变为正常。

 DESCRIPTION (provided by applicant) Although we used to believe that all retrotransposition occurred in the germ line in humans, over the past 10 years it has become clear that somatic retrotransposition, especially of LINE1s (L1s), is prominent, at least in the brain and in epithelial cancers. A number of groups have shown retrotransposition in neural precursor cells and the adult brain. Likewise, a number of groups including our own have shown significant retrotransposition in gastrointestinal cancers. A key finding of our studies is that most L1 insertions in GI cancers occur very early in cancer development. Indeed, some of the insertions are found in low concentration (detected only by nested PCR) in normal cells, but they become essentially clonal in the cancer (detected by conventional PCR). ln this application, we strive to answer two big questions in the field. First, does significant retrotransposition occur in adult somatic tissues outside of the brain and, if so, at what frequency? In this aim we will study L1 insertions in single normal cells near the tumors to find what fraction of the insertions in the tumor are already present in normal cells. We will determine if retrotransposition rate is greater in normal cells or in tumor cells. We will also stuy the frequency of insertions in single normal cells not associated with cancer and from various organs to determine if some tissue types have a greater propensity for retrotransposition than others. The second big question is: Does L1 somatic retrotransposition have any significant role in the etiology of cancer? We need to determine whether we can alter the cellular phenotype towards normal by deletion of somatic L1 insertions found in cancer-related genes in cancer-derived cell lines.