The mechanistic and evolutionary diversity of programmed DNA elimination

Beyond somatic mutations, the genetic makeup of an organism is often assumed to remain constant across all cells or nuclei within individuals. However, some organisms exhibit programmed DNA elimination (PDE), whereby specific cell lineages lose DNA segments or whole chromosomes. Building evidence indicates that PDE occurs in a wide range of eukaryotes and is linked to diverse cellular processes including gene silencing, germline differentiation, genome defence and sex determination. Here we compare PDE across broad phylogenetic groups, highlighting the mechanistic diversity, overlooked plasticity in genome integrity and the considerable gaps in our understanding of why PDE emerged recurrently and is maintained across the Tree of Life.