APP and early-onset autosomal dominant Alzheimer disease: Sortilin is also emerging as a gene of interest in neurodegenerative diseases, with genetic studies linking SORT1 variants to altered Alzheimer’s disease (AD) risk (5, 6), and functional evidence showing its role in regulating key AD-related processes, including the trafficking of β-secretase 1 and amyloid precursor protein (APP) (7, 8, 9), as well as facilitating amyloid-β clearance through binding to apolipoprotein E (10).