Damaged DNA Is an Early Event of Neurodegeneration in Induced Pluripotent Stem Cell-Derived Motoneurons with UBQLN2P497H Mutation

Abstract

Ubiquilin-2 (UBQLN2) mutations lead to familial amyotrophic lateral sclerosis (FALS)/and frontotemporal dementia (FTLD) through unknown mechanisms. The combination of iPSC technology and CRISPR-mediated genome editing technology can generate an iPSC-derived motor neuron (iPSC-MN) model with disease-relevant mutations, which results in increased opportunities for disease mechanism research and drug screening. In this study, we introduced a UBQLN2-P497H mutation into a healthy control iPSC line using CRISPR/Cas9, and differentiated into MNs to study the pathology of UBQLN2-related ALS. Our in vitro MN model faithfully recapitulated specific aspects of the disease, including MN apoptosis. Under sodium arsenite (SA) treatment, we found differences in the number and the size of UBQLN2+ inclusions in UBQLN2P497H MNs and wild-type (WT) MNs. We also observed cytoplasmic TAR DNA-binding protein (TARDBP, also known as TDP-43) aggregates in UBQLN2P497H MNs, but not in WT MNs, as well as the recruitment of TDP-43 into stress granules (SGs) upon SA treatment. We noted that UBQLN2-P497H mutation induced MNs DNA damage, which is an early event in UBQLN2-ALS. Additionally, DNA damage led to an increase in compensation for FUS, whereas UBQLN2-P497H mutation impaired this function. Therefore, FUS may be involved in DNA damage repair signaling.

Genetic disruption of mammalian endoplasmic reticulum‐associated protein degradation: Human phenotypes and animal and cellular disease models

“…However, several research studies propose that ubiquilin 2 mutations hinder the trafficking and localization of secretory proteins, ultimately resulting in the accumulation of protein aggregates 303 . Additionally, these mutations may disrupt the process of autophagy 304 and even cause DNA damage 305 …”

“…303 Additionally, these mutations may disrupt the process of autophagy 304 and even cause DNA damage. 305 Similar to various individual ERAD components, ubiquilin-4 is also associated with various cancer subtypes including hepatocellular carcinoma 306 and colorectal cancer. 307 While both Rad23a and Dsk2 mammalian homologs are well studied and investigated, Ddi1 has not been extensively explored.…”