SNCA and early-onset autosomal dominant Alzheimer disease: Although α-synuclein has been originally found to be accumulated in the Lewy bodies (LBs) and Lewy neurites (LNs), which are specific pathological hallmarks in PD cases, later misbehavior of this protein has also been linked to multiple other neurodegenerative diseases, such as Alzheimer’s disease, Down’s syndrome [1], and many other synucleinopathies [17,18,19,20,21,22,23].