Chagas Disease Multidisciplinary Research Laboratory, Faculty of Medicine, University of Brasilia, Brasília, Federal District, Brazil.
PLoS One. 2010 Feb 12;5(2):e9181. doi: 10.1371/journal.pone.0009181.
Interspecies DNA transfer is a major biological process leading to the accumulation of mutations inherited by sexual reproduction among eukaryotes. Lateral DNA transfer events and their inheritance has been challenging to document. In this study we modified a thermal asymmetric interlaced PCR by using additional targeted primers, along with Southern blots, fluorescence techniques, and bioinformatics, to identify lateral DNA transfer events from parasite to host. Instances of naturally occurring human infections by Trypanosoma cruzi are documented, where mitochondrial minicircles integrated mainly into retrotransposable LINE-1 of various chromosomes. The founders of five families show minicircle integrations that were transferred vertically to their progeny. Microhomology end-joining of 6 to 22 AC-rich nucleotide repeats in the minicircles and host DNA mediates foreign DNA integration. Heterogeneous minicircle sequences were distributed randomly among families, with diversity increasing due to subsequent rearrangement of inserted fragments. Mosaic recombination and hitchhiking on retrotransposition events to different loci were more prevalent in germ line as compared to somatic cells. Potential new genes, pseudogenes, and knockouts were identified. A pathway of minicircle integration and maintenance in the host genome is suggested. Thus, infection by T. cruzi has the unexpected consequence of increasing human genetic diversity, and Chagas disease may be a fortuitous share of negative selection. This demonstration of contemporary transfer of eukaryotic DNA to the human genome and its subsequent inheritance by descendants introduces a significant change in the scientific concept of evolutionary biology and medicine.
种间 DNA 转移是一种主要的生物学过程，导致真核生物通过有性繁殖积累突变。侧向 DNA 转移事件及其遗传一直是难以证明的。在这项研究中，我们通过使用额外的靶向引物对热不对称交错 PCR 进行了修改，同时结合 Southern 印迹、荧光技术和生物信息学，来鉴定寄生虫到宿主的侧向 DNA 转移事件。记录了人类感染克氏锥虫的自然实例，其中线粒体微小环主要整合到各种染色体的逆转录转座子 LINE-1 中。五个家族的创始人显示出微小环整合，这些整合垂直传递给他们的后代。微小环和宿主 DNA 中的 6 到 22 个富含 AC 的核苷酸重复的微同源末端连接介导了外源 DNA 的整合。异质微小环序列在家族之间随机分布，由于插入片段的后续重排，多样性增加。与体细胞相比，重组酶和转座事件的搭便车在生殖系中更为普遍。鉴定了新的基因、假基因和敲除。提出了微小环在宿主基因组中整合和维持的途径。因此，克氏锥虫感染意外地增加了人类遗传多样性，而恰加斯病可能是负选择的偶然共享。这一证明表明，真核生物 DNA 向人类基因组的当代转移及其随后被后代遗传，给进化生物学和医学的科学概念带来了重大变化。
