ATF4 and multiple system atrophy: When examining the mRNA expression of the UPR signaling markers (CHOP, ATF4, GRP94, and HSPA5), we were unable to detect any differences between the MSA-P patients and the healthy controls (data not shown), facilitating the assumption that this common mechanism in neurodegeneration does not play a major part yet in the manifestation of MSA pathology in striatal neurons at this stage of maturation and disease progression.