ARPP21 and Alzheimer disease: ARPP21 encodes a neuronal phosphoprotein enriched in brain regions receiving dopaminergic innervation.27ARPP21 also regulates calmodulin signaling, believed to be associated with AD pathogenesis.28,29 On chromosome 6, rs71567499 is found in a region that is rich in genes (and several GVs in high LD with rs71567499 are located within or close to different genes, making it challenging to nominate a causative gene, Figure 2).