The retrotransposon LINE-1 (long interspersed element 1, L1) is a transposable element that has extensively colonized the mammalian germline. L1 retrotransposition can also occur in somatic cells, causing genomic mosaicism, as well as in cancer. However, the extent of L1-driven mosaicism arising during ontogenesis is unclear. We discuss here recent experimental data which, at a minimum, fully substantiate L1 mosaicism in early embryonic development and neural cells, including post-mitotic neurons. We also consider the possible biological impact of somatic L1 insertions in neurons, the existence of donor L1s that are highly active (‘hot’) in specific spatiotemporal niches, and the evolutionary selection of donor L1s driving neuronal mosaicism.

逆转座子LINE-1（长穿插元件1，L1）是已广泛定殖于哺乳动物种系的可转座元件。L1逆转座也可能发生在体细胞中，导致基因组镶​​嵌和癌症。但是，尚不清楚在本体形成过程中由L1驱动的镶嵌的程度。我们在这里讨论最近的实验数据，这些数据至少可以充分证实早期胚胎发育和神经细胞（包括有丝分裂后神经元）中的L1镶嵌。我们还考虑了在神经元中体细胞L1插入的可能的生物学影响，在特定的时空利基中高度活跃（“热”）的供体L1s的存在以及驱动神经元镶嵌的供体L1s的进化选择。