L1 retrotransposition in neurons is modulated by MeCP2. Nature 468

Long interspersed nuclear elements-1 (LINE-1 or L1s) are abundant retrotransposons that comprise approximately 20 % of mammalian genomes1–3. Active L1 retrotransposons can impact the genome in a variety of ways, creating insertions, deletions, new splice sites or gene expression fine-tuning4–6. We have previously shown that L1 retrotransposons are capable of mobilization in neuronal progenitor cells from rodents and humans and evidence of massive L1 insertions was observed in adult brain tissues but not in other somatic tissues7,8. In addition, L1 mobility in the adult hippocampus can also be influenced by the environment9. The neuronal specificity of somatic L1 retrotransposition in neural progenitors is partially due to the transition of a Sox2/HDAC1 repressor complex to a Wnt-mediated TCF/LEF transcriptional activation7,10. The transcriptional switch accompanies chromatin remodeling during neuronal differentiation, allowing a transient stimulation of L1 transcription7. The activity of L1 retrotransposons during brain development can impact gene expression and neuronal function, thereby increasing brain-specific genetic mosaicism11,12. Further understanding of the molecular mechanisms that regulate L1 expression should provide new insights into the role of L1 retrotransposition during brai