SNCA and Parkinson disease: In the neurons derived from PD patient iPSCs carrying α-synuclein A53T mutation, Chung et al. found that the hallmark of ER stress, PDI increased, but the marker of ER stress-induced cell death, CHOP, did not have the change (Chung et al., 2013), revealing that these mutant neurons are still at an early pathologic stage.