Alpha-synuclein induces the unfolded protein response in Parkinson’s disease SNCA triplication iPSC-derived neurons

Abstract

The recent generation of induced pluripotent stem cells (iPSCs) from a patient with Parkinson's disease (PD) resulting from triplication of the α-synuclein (SNCA) gene locus allows unprecedented opportunities to explore its contribution to the molecular pathogenesis of PD. We used the double-nicking CRISPR/Cas9 system to conduct site-specific mutagenesis of SNCA in these cells, generating an isogenic iPSC line with normalized SNCA gene dosage. Comparative gene expression analysis of neuronal derivatives from these iPSCs revealed an ER stress phenotype, marked by induction of the IRE1α/XBP1 axis of the unfolded protein response (UPR) and culminating in terminal UPR activation. Neuropathological analysis of post-mortem brain tissue demonstrated that pIRE1α is expressed in PD brains within neurons containing elevated levels of α-synuclein or Lewy bodies. Having used this pair of isogenic iPSCs to define this phenotype, these cells can be further applied in UPR-targeted drug discovery towards the development of disease-modifying therapeutics.

Axonal pathology in hPSC-based models of Parkinson’s disease results from loss of Nrf2 transcriptional activity at the Map1b gene locus

“…We find this loss of function to correlate highly with accumulation of α-syn into insoluble aggregates. As such, we would predict that other synucleinopathy-related genome alterations such as SNCA-A30P, SNCA-E46K, and gene duplication or triplication would also result in loss of Nrf2 activity, as those mutations similarly promote synuclein deposition into insoluble aggregates (38,39).…”

Fatty acid chemical mediator provides insights into the pathology and treatment of Parkinson’s disease

“…The observation that stem cells derived from PD animals and patients display increased sEH levels and closely accompany dopamine degeneration further supports the intimate role of sEH in PD pathology (7). The use of PD patient-derived stem cells as a model to recapitulate the disease has paved the way for research and development of novel treatments (19,20). In Ren et al's paper (7), the utilization of small and large animal models, including primates-which closely resemble human PD-further probes the pathological contribution of sEH across species.…”

Modeling Cell-Cell Interactions in Parkinson’s Disease Using Human Stem Cell-Based Models

“…α-Syn accumulation has been demonstrated in iPSC derived PD neurons of SNCA duplication (Prots et al, 2018), SNCA triplication (Byers et al, 2011;Devine et al, 2011;Flierl et al, 2014;Oliveira et al, 2015;Reyes et al, 2015;Heman-Ackah et al, 2017;Vasquez et al, 2017) and point mutations in SNCA A53T (Ryan et al, 2014;Kouroupi et al, 2017), LRKK2 G2019S (Nguyen et al, 2011;Reinhardt et al, 2013b), PARK2 V324A (Imaizumi et al, 2012;Chung et al, 2016), PINK1 Q456X (Chung et al, 2016) and GBA N370S (Woodard et al, 2014;Kim et al, 2018). A study introducing a PD-associated risk variant in an isogenic iPSC line using CRISPR technology was able to determine an enhancer element that regulates α-Syn expression (Soldner et al, 2016).…”

“…Despite these drawbacks, such neuronal cultures are especially valuable when investigating early transcriptomic and proteomic pathological changes, which may ultimately lead to activation of apoptotic pathways. Transcriptomic analysis of SNCA triplication in cortical neurons suggest that endoplasmatic reticulum stress followed by activation of the IRE1a/XBP arm of the unfolded protein response might be responsible for cell death in PD (Heman-Ackah et al, 2017). Microarray analysis of DA neurons derived from two patients with A53T mutation in SNCA was associated with S-nitrosylation of the anti-apoptotic transcription factor MEF2C contributing to mitochondrial dysfunction (Ryan et al, 2013).…”