Knockout (KO) of CypD stabilized mitochondrial function (Du et al., 2008, 2011, 2014; Gainutdinov et al., 2015; Gordan et al., 2016; Sun and Jacobs, 2016), decreased threshold of mPTP formation, and improved cognitive function in old AD transgenic mice (Du et al., 2008, 2011, 2014). The gene discussed is PPIF; the disease is Alzheimer disease.