Mitochondrial DNA editing inches closer to reality

Abstract

Over a billion years ago, a single-celled archaean engulfed an overachieving bacterium. The bacterium didn’t perish but instead struck an agreement with its host. For shelter, the bacterium would pay rent by doing what it did best—churn out energy molecules to power both itself and the host cell. This pivotal event in Earth’s history, according to the endosymbiosis theory, allowed the nested cells to harvest energy from the environment like never before, thus starting the march toward complex life. From such simple prokaryotic life forms came nucleus-toting eukaryotes and then their multicellular counterparts, eventually giving rise to the organismic richness across the planet today. With a few exceptions, most modern eukaryotic cells harbor these once-free-roaming bacteria. We call them mitochondria. Over the eons, mitochondria coevolved with their hosts as organelles, but the former bacteria never fully jettisoned their genes. In a last-ditch streak of independence, mitochondria retained 37 genes to