L1 retrotransposition alters the hippocampal genomic landscape enabling memory formation

Somatic LINE-1 (L1) retrotransposition is a source of genomic mosaicism and potential phenotypic diversity among neurons during brain development. In the adult brain, Ll expression can be triggered by different environmental alterations, but its functional role in this context remains unknown. Here we demonstrate a neural activation-dependent increase in the number of Ll retrotransposon insertions in the hippocampus. Using both pharmacologic and genetic approaches in mice, we demonstrate that L1 expression in the adult hippocampus enables long-term memory formation. These results provide experimental evidence that Ll retrotransposition-induced genomic mosaicism is involved in cognitive processes such as memory formation. (C) 2016 Elsevier Inc. All rights reserved.