Increased expression, but not insertion of L1 retrotransposons in aged neural stem and progenitor cells

Abstract: Retrotransposons are mobile elements that build up an extensive part of our genome, and can create genomic instability through new insertions. LINE1 is a subtype of transposons that are still active in human and mice, and can both copy themselves, and assist other retroelements to new insertions, but are strongly regulated by different enzymes. Neural stem and progenitor cells (NSPCs) are present in the developing and adult brain and ensure neurogenesis throughout life but declines with advancing age. So far, very little is known about retrotransposon activity during aging and nothing about their expression or function in aging NSPCs. Here we have compared retrotransposon expression and integration in NSPCs from adult and aged subventricular zone in mice. We show that L1 retroevents take place in adult NSPCs, and that expression of L1 and its regulator APOBEC3 are substantially increased in aged compared to adult NSPCs but without any evidence for accumulation of new genomic insertions.