GBA1 and Parkinson disease: Unlike previous studies where isogenic lines were generated either by introducing variants into an iPSC line derived from a healthy individual50, or by correcting GBA1 variants in heterozygote lines, we elected to begin from a Parkinson patient iPSC line homozygous for the mild N370S GBA1 variant to allow for bidirectional modulation of GCase levels and lipid accumulation in a “GD/PD-permissive” genetic background.