SNCA and early-onset autosomal dominant Alzheimer disease: We choose dosage-sensitive genes known to be involved in different neurological disorders, including APP (gene duplication, Alzheimer’s disease, AD), SNCA (gene duplication/triplication, Parkinson’s disease, PD) [17], and PMP22, which has been associated with Charcot-Marie-Tooth 1A (gene duplication) and several other CNS disorders [18, 19].