The levels of phosphorylated eIF2α vs total eIF2α and ER homeostasis in dystonia patients with the TOR1A ΔGAG mutation

Abstract

DYT1 dystonia is an early onset isolated severe movement disorder, caused by an in-frame GAG deletion in the TOR1A gene. The TOR1A gene codes for a Torsin- family-1-member-A protein (torsinA), and its activity is associated mostly in the endoplasmic reticulum (ER) and nuclear envelope (NE) homeostasis. The ER stress is linked with many neurodegenerative disorders, and it triggers the unfolded protein response (UPR) which has three main pathways that play a role in its activation: protein kinase R-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6) (Hetz and Saxena, 2017). Previous studies have published the eIF2α dysregulation (PERK pathway) in DYT1 mouse models of dystonia (Beauvais et al., 2018). We hypothesised that iPSC-derived cortical neurons from dystonia patients would have a dysregulated homeostasis in the UPR. The aim of this study is to investigate the PERK, eIF2α and ATF4 pathways in cortical neurons from DYT1 patients and healthy controls. Three DYT1 and three control human iPSC- derived cortical neuronal precursors were used in this study. The results revealed that cortical neurons derived from iPSC DYT1 patients had overexpression of total and phosphorylated eIF2α compared to controls. Additionally, the results showed that there was a slight decrease in the levels of total PERK expression in the patient group compared to the control group. These findings align with previous findings on animal models regarding eIF2α and UPR dyshomeostases in dystonia and confirm that this dysregulation can be seen in the human cell model of DYT1. Furthermore, no results were obtained for phosphorylated PERK and ATF4 proteins. This research project represents a progression in our understanding of the mechanisms of the UPR in human cell models of DYT1 dystonia.