PARK7 and amyotrophic lateral sclerosis: In the validation study, we analyzed total protein levels of candidate phenotypic biomarkers, PPIA, HSP90, GRP78, ERp57, and DJ-1, by dot blot analysis in PBMC samples from an independent set of ALS patients (n = 85), n = 38 early ALS and n = 47 late ALS, and matched controls (n = 83), n = 35 early controls and n = 48 late controls (Table 2).