Pre-Cambrian origin of envelope-carrying retrotransposons in metazoans.

Envelope-carrying retrotransposons in metazoans originated before the split of bilaterian and non-bilaterian animals in the Pre-Cambrian era, over 541 million years ago.

• Why it matters: Understanding the ancient origins of these elements sheds light on the evolution of viral and host genome interactions, filling a gap in knowledge about retrotransposon history across diverse animal lineages.
• What they did: Researchers systematically searched invertebrate genomes for intact envelope-containing ERVs homologous to Ty3/gypsy elements, analyzing their distribution, structure, and phylogenetic relationships across taxa including cnidarians, ctenophores, and tunicates.
• The result: They found widespread, ancient envelope genes that have diverged over time, indicating an early, shared viral association that predates major animal lineage splits, enabling insights into retrotransposon evolution and host-virus co-evolution.