The eQTL mapping also found converging evidence and implicated BACE2. The gene BACE2 encodes for a β-secretase homologue that is capable of cleaving amyloid β precursor protein resulting in the formation of amyloid-β protein, a major component in the pathogenesis of Alzheimer disease.54,55,56 Interestingly, a postmortem study has found increased levels of insoluble and soluble amyloid-β protein in the cerebellar and parietal cortex of patients with ET compared with control individuals and patients with PD.57 The gene discussed is BACE2; the disease is essential thrombocythemia.