Mitochondria undergo continual cycles of fusion and fission, and the balance of these
opposing processes regulates mitochondrial morphology. Paradoxically, cells invest many
resources to maintain tubular mitochondrial morphology, when reducing both fusion and
fission simultaneously achieves the same end. This observation suggests a requirement for
mitochondrial fusion, beyond maintenance of organelle morphology. Here, we show that
cells with targeted null mutations in Mfn1 or Mfn2 retained low levels of mitochondrial fusion …