PSEN1 and early-onset autosomal dominant Alzheimer disease: In 1995, the PSEN1 gene, which encodes the protein presenilin 1 required for γ‐secretase to produce amyloid‐beta (Aβ) from APP, was cloned for the first time and was identified as one of pathogenic genes for the EOFAD (Perez‐Tur et al., 1995).