Thomas Charles A, Muotri Alysson R
Department of Pediatrics, Rady Children's Hospital San Diego and Department of Cellular and Molecular Medicine, University of California, San Diego School of Medicine, La Jolla, CA 92093, USA.
Front Biosci (Elite Ed). 2012 Jan 1;4(5):1663-8. doi: 10.2741/e488.
Long interspersed nucleotide element 1 (L1) is a family of non-LTR retrotransposons that can replicate and reintegrate into the host genome. L1s have considerably influenced mammalian genome evolution by retrotransposing during germ cell development or early embryogenesis, leading to massive genome expansion. In humans, over 30 % of the genome can be attributed to L1-mediated retrotransposition. Historically, L1s were thought to only retrotranspose during gametogenesis and in neoplastic processes, but recent studies have shown that L1s are extremely active in the mouse, rat, and human neuronal progenitor cells (NPCs). In fact, it is estimated that the hippocampus and other regions of the brain may have multiple insertions per cell. These insertions can dramatically impact neuronal transcriptional expression, creating unique transcriptomes of individual neurons. Furthermore, transcriptional activation of L1 elements mimics the transcription activation of the NeuroD1 gene, suggesting a prominent role of L1 expression during neurogenesis.
长散在核元件1（L1）是一类非长末端重复序列逆转录转座子，能够复制并重新整合到宿主基因组中。L1通过在生殖细胞发育或早期胚胎发生过程中逆转录转座，对哺乳动物基因组进化产生了重大影响，导致基因组大量扩张。在人类中，超过30%的基因组可归因于L1介导的逆转录转座。从历史上看，L1被认为仅在配子发生和肿瘤形成过程中进行逆转录转座，但最近的研究表明，L1在小鼠、大鼠和人类神经元祖细胞（NPC）中极其活跃。事实上，据估计，大脑的海马体和其他区域每个细胞可能有多个插入。这些插入可显著影响神经元转录表达，产生单个神经元独特的转录组。此外，L1元件的转录激活模拟了NeuroD1基因的转录激活，表明L1表达在神经发生过程中起着重要作用。
