SNCA and Alzheimer disease: Later studies in amyloid plaques from an Alzheimer’s disease (AD) brain discovered two unknown peptides, in addition to the major amyloid beta fragment, which were named NAC (non-A beta component of AD amyloid) peptide and its precursor, NACP (Ueda et al., 1993) and identified two proteins of 140 and 134 aa, which were highly expressed in the human brain (Jakes et al., 1994).