Defective synaptic connectivity and axonal neuropathology in a human iPSC-based model of familial Parkinson’s disease

Abstract

α-Synuclein (αSyn) is the major gene linked to sporadic Parkinson's disease (PD), whereas the G209A (p.A53T) αSyn mutation causes a familial form of PD characterized by early onset and a generally severe phenotype, including nonmotor manifestations. Here we generated de novo induced pluripotent stem cells (iPSCs) from patients harboring the p.A53T mutation and developed a robust model that captures PD pathogenic processes under basal conditions. iPSC-derived mutant neurons displayed novel disease-relevant phenotypes, including protein aggregation, compromised neuritic outgrowth, and contorted or fragmented axons with swollen varicosities containing αSyn and Tau. The identified neuropathological features closely resembled those in brains of p.A53T patients. Small molecules targeting αSyn reverted the degenerative phenotype under both basal and induced stress conditions, indicating a treatment strategy for PD and other synucleinopathies. Furthermore, mutant neurons showed disrupted synaptic connectivity and widespread transcriptional alterations in genes involved in synaptic signaling, a number of which have been previously linked to mental disorders, raising intriguing implications for potentially converging disease mechanisms.

Induced pluripotent stem cell‐based modeling of mutant LRRK2‐associated Parkinson's disease

“…Importantly, accumulation of α‐syn does not represent a LRRK2‐specific pathophenotype as similar data have been generated for various different models of familial PD, including iPSC models for triplication of the SNCA gene (SNCA trp ) (Byers et al., ; Flierl et al., ; Mazzulli, Zunke, Isacson, Studer, & Krainc, ), the SNCA A53T point mutation (Kouroupi et al., ; Mazzulli, Zunke, Tsunemi et al., ; Ryan et al., ), mutations in GBA (Woodard et al., ), PRKN (Chang et al., ; Chung et al., ; Shaltouki et al., ) and PINK1 (Chung et al., ), in homozygous DJ‐1 mutant cells and in DJ‐1 knock‐out neurons (Burbulla et al., ) as well as in iPSC‐derived neurons from an idiopathic PD (iPD) patient (Mazzulli, Zunke, Isacson et al., ).…”

“…Interestingly, reduced neurite length appears to be specific for only a subset of PD risk genes. While this phenotype was repeatedly demonstrated for LRRK2 and also for SNCA trp (Lin et al., ), A53T mut (Kouroupi et al., ) and iPD (Sanchez‐Danes et al., ), conflicting or inconclusive data have been presented for PRKN and PINK1 (Lin et al., ; Miller et al., ; Ren et al., ). In addition, a model for GBA1 N370S did not show clear evidence for reduced neurite length (Woodard et al., ).…”

“…In this context, it is important to note that, aside from LRRK2, several models for familial PD show evidence for increased sensitivity toward various forms of cellular stress, e.g. PRKN (Chang et al, 2016;Chung et al, 2016;Imaizumi et al, 2012;Suzuki et al, 2017), SNCA trp (Flierl et al, 2014), A53T mut (Kouroupi et al, 2017), PINK1 (Chung et al, 2016;Cooper et al, 2012) and GBA (Schöndorf et al, 2014).…”

Modeling Parkinson's disease with induced pluripotent stem cells harboring α‐synuclein mutations

“…Numerous studies on iPSCs harboring the A53T SNCA mutation or triplication of the wild-type SNCA gene are now published (5,9,11,13,23,27,32,45). The over-expression of SNCA mRNA and a-synuclein protein is a common observation across multiple studies on triplication SNCA iPSCs, as well as increased sensitivity of oxidative stress, which may be indicative of mitochondrial dysfunction.…”

“…They also identified Thioflavin S-positive aggregates, a-synuclein-positive structures within inclusion bodies and reduction of neurite quantity and length. Treatment of A53T SNCA iPSC-derived neurons with NPT100-18A significantly rescued the neurite defects and reduced the sensitivity of the neurons to oxidative stress (23). In the absence of isogenic control iPSC lines, they used small molecule modulators of a-synuclein aggregation, such as NPT100-18A.…”