FIS1 and Huntington disease: Although one paper has suggested that both fusion and fission markers are increased in AD,96 others report that mitochondrial fusion is decreased but mitochondrial fission is increased in AD, which as in HD and PD causes fragmentation of the mitochondria.97, 98 It has also been suggested that rather than drp1 causing mitochondrial fragmentation, the OMM receptor Fis1 levels were increased.98 These results do suggest that any imbalance in the mitochondrial dynamics may have a disastrous effect on mitochondrial function.