Hitching a ride with a retroelement Retroviruses and retroelements have inserted their genetic code into mammalian genomes throughout evolution. Although many of these integrated virus-like sequences pose a threat to genomic integrity, some have been retooled by mammalian cells to perform essential roles in development. Segel et al . found that one of these retroviral-like proteins, PEG10, directly binds to and secretes its own mRNA in extracellular virus–like capsids. These virus-like particles were then pseudotyped with fusogens to deliver functional mRNA cargos to mammalian cells. This potentially provides an endogenous vector for RNA-based gene therapy. —DJ