FIS1 and Alzheimer disease: Moreover, compared to the WT mice, the altered mitochondrial fission / fusion was typified by an increase in COX IV (Fig. S5C, P < 0.001), Tom20 (Fig. S5D, P < 0.001), and FIS1 (Fig. S5E, P < 0.001) expression in the hippocampal tissue of AD mice.