Abstract

Transposons are abundant in most genomes and constitute about 50% of the human genome. They are usually considered as genomic parasites, the mobilisation of which can cause harmful genetic mutations. Various mechanisms have evolved throughout the tree of life to defend genomes from the deleterious effects of transposition. Curiously, the past couple of years have brought about seminal discoveries showing that transposons also have functions essential to their host. For example, they play key roles in mammalian development, neurogenesis, and immune response. These novel findings suggest that transposons have widespread vital functions and call for thorough investigation in all genomes and organisms.