ACP2 and progressive supranuclear palsy: Lysosomal acid phosphatase 2 (Acp2) is a key enzyme in cerebellar development [1,2,3], and it is implicated in a variety of neurological disorders including progressive supranuclear palsy [4] and juvenile neuronal ceroid lipofuscinosis, also known as Batten disease (a disease induced by mutations in the lysosomal protein ceroid-lipofuscinosis neuronal 3 (CLN3)) [5].