GBA1 and Parkinson disease: Interestingly, while there was no difference in mitochondrial density in the soma (Fig. 6a, b and Supplementary Fig. 3k), we found that axonal mitochondrial density was significantly decreased in mutant GBA1 neurons compared to axons of isogenic control neurons (Fig. 6a, c), suggesting that mutant GBA1 preferentially disrupts axonal mitochondrial distribution in Parkinson’s patient neurons.