MAPK8 and Parkinson disease: The amounts of phosphorylated ERK1/2 and phosphorylated JNK, normalized by ERK1/2 and JNK, respectively, were shown to be significantly higher in PD patient-derived cortical neurons compared to those from control-derived cortical neurons on day 8 (Fig. 4A–D, Additional file 1: Fig. S3A–F).