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Cell-lineage analysis in human #brain using endogenous retroelements http://www.cell.com/neuron/abstract/S0896-6273(14)01137-4 Tracing L1 insertions w/ #singlecell sequencing

Using single cell WGS of 16 neuronal cells the authors investigated two somatic insertions of L1Hs elements in an adult human brain. Using these results the authors infer that L1 somatic insertions are infrequent and ALUs and SVAs somatic retrotransposition are extremely rare. Assessing two L1Hs insertions in 32 samples across different regions of this same adult brain, they found that while one insertion was spatially restricted (2x1cm region), the other was found across all samples of the adult brain (but not found in other tissues such as Heart, Lung, etc.). The more restricted one (L1Hs#1) is inferred to have happened during the Fetal stage (first trimester) while the broader one happened earlier, approximately 2 weeks
post-fertilization. Overall the paper is clear, concise, and simple. It answers an interesting biological question: Can retrotransposition be used as a marker of cell clonal expansion? It does, although the retrotransposition frequency is very small and SNVs might support better results for the same analysis due to their higher frequency..