Given the link between mitochondrial fission and mitophagy it is interesting that several studies have recently suggested a role for ERK1/2 signalling in the control of mitochondrial fission and implicated this in pathological mitochondrial morphology in Alzheimer's disease (AD), in the promotion of tumour growth and even reprograming of induced pluripotent stem cells (iPSCs). The gene discussed is MAPK3; the disease is Alzheimer disease.