Interspecies mitochondrial fusion between mouse and human mitochondria is rapid and efficient

A detailed molecular understanding of mitochondrial fusion and fission in mammalian cells is rapidly emerging. In this report, we demonstrate for the first time cross-species mitochondrial fusion between distantly related species using green and red fluorescent proteins targeted to the mitochondrial matrix. We found that mouse mitochondria were able to efficiently fuse to unmodified mitochondria of human cells and that the contents of the mitochondrial matrix were completely mixed in less than 4 h. We also observed that mitochondria from the mtDNA-less (ρ⁰) mouse cells can homogeneously fuse to the mitochondria of human cells. We were, however, unable to maintain human mitochondrial DNA in the mouse cells. These results indicate that mitochondrial fusion proteins in mouse and human cells have enough functional homology to mediate efficient cross-species mitochondrial fusion, but mouse nuclear and human mitochondrial genomes have not retained functional compatibility with one another.