PSEN1 and Alzheimer disease: Whilst established causes of AD include mutations in the nuclear genome such as those in the AβPP (Kalimo et al., 2014), PSEN1 (Kelleher and Shen, 2017), and PSEN2 genes (Jayadev et al., 2010), the mitochondrial genome and nuclear genes related to mitochondrial function have also been linked to AD.