The number and morphology of mitochondria within a cell are precisely regulated by the
mitochondrial fission and fusion machinery. The human protein, hFis1, participates in
mitochondrial fission by recruiting the Drp1 into the mitochondria. Using short hairpin RNA,
we reduced the expression levels of hFis1 in mammalian cells. Cells lacking hFis1 showed
sustained elongation of mitochondria and underwent significant cellular morphological
changes, including enlargement, flattening, and increased cellular granularity. In these cells …