BACKGROUND There is increasing evidence that the transpositional activity of retroelements (REs) is not limited to germ line cells, but often occurs in tumor and normal somatic cells. Somatic transpositions were found in several human tissues and are especially typical for the brain. Several computational and experimental approaches for detection of somatic retroelement insertions was developed in the past few years. These approaches were successfully applied to detect somatic insertions in clonally expanded tumor cells. At the same time, identification of somatic insertions presented in small proportion of cells, such as neurons, remains a considerable challenge. RESULTS In this study, we developed a normalization procedure for library enrichment by DNA sequences corresponding to rare somatic RE insertions. Two rounds of normalization increased the number of fragments adjacent to somatic REs in the sequenced sample by more than 26-fold, and the number of identified somatic REs was increased by 8-fold. CONCLUSIONS The developed technique can be used in combination with vast majority of modern RE identification approaches and can dramatically increase their capacity to detect rare somatic RE insertions in different types of cells.

中文翻译：

---

一种用于罕见体细胞逆转录插入测序的先进富集方法。

背景越来越多的证据表明，逆转录元件（REs）的转座活性不仅限于生殖系细胞，而且经常发生在肿瘤和正常体细胞中。在几种人体组织中发现了体细胞转座，并且在大脑中尤为典型。在过去的几年中，开发了几种用于检测体细胞逆转录插入的计算和实验方法。这些方法成功地应用于检测克隆扩增的肿瘤细胞中的体细胞插入。同时，识别在小部分细胞（如神经元）中存在的体细胞插入仍然是一个相当大的挑战。结果 在这项研究中，我们开发了一种标准化程序，用于通过对应于罕见的体细胞 RE 插入的 DNA 序列来富集文库。两轮归一化使测序样本中与体细胞 RE 相邻的片段数量增加了 26 倍以上，鉴定出的体细胞 RE 的数量增加了 8 倍。结论 开发的技术可以与绝大多数现代 RE 识别方法结合使用，并且可以显着提高它们检测不同类型细胞中罕见的体细胞 RE 插入的能力。