GBA1 and Parkinson disease: While it is not clear whether heterozygous mutations in GBA increase PD risk through accumulation of GlcCer or whether other mechanisms are triggered by mutated enzyme, several studies observed that PD heterozygous mutations in GBA result in α-syn buildup in neurons (Taguchi et al., 2017; Yun et al., 2018), likely because mutant GBA negatively impacts on the degradative capacity of the neuron.