Higher Vulnerability and Stress Sensitivity of Neuronal Precursor Cells Carrying an Alpha-Synuclein Gene Triplication

Abstract

Parkinson disease (PD) is a multi-factorial neurodegenerative disorder with loss of dopaminergic neurons in the substantia nigra and characteristic intracellular inclusions, called Lewy bodies. Genetic predisposition, such as point mutations and copy number variants of the SNCA gene locus can cause very similar PD-like neurodegeneration. The impact of altered α-synuclein protein expression on integrity and developmental potential of neuronal stem cells is largely unexplored, but may have wide ranging implications for PD manifestation and disease progression. Here, we investigated if induced pluripotent stem cell-derived neuronal precursor cells (NPCs) from a patient with Parkinson’s disease carrying a genomic triplication of the SNCA gene (SNCA-Tri). Our goal was to determine if these cells these neuronal precursor cells already display pathological changes and impaired cellular function that would likely predispose them when differentiated to neurodegeneration. To achieve this aim, we assessed viability and cellular physiology in human SNCA-Tri NPCs both under normal and environmentally stressed conditions to model in vitro gene-environment interactions which may play a role in the initiation and progression of PD. Human SNCA-Tri NPCs displayed overall normal cellular and mitochondrial morphology, but showed substantial changes in growth, viability, cellular energy metabolism and stress resistance especially when challenged by starvation or toxicant challenge. Knockdown of α-synuclein in the SNCA-Tri NPCs by stably expressed short hairpin RNA (shRNA) resulted in reversal of the observed phenotypic changes. These data show for the first time that genetic alterations such as the SNCA gene triplication set the stage for decreased developmental fitness, accelerated aging, and increased neuronal cell loss. The observation of this “stem cell pathology” could have a great impact on both quality and quantity of neuronal networks and could provide a powerful new tool for development of neuroprotective strategies for PD.

Chromatin-Bound Oxidized α-Synuclein Causes Strand Breaks in Neuronal Genomes in in vitro Models of Parkinson’s Disease

“…7C) and mRNA quantitation by RT-PCR (Fig. 7D), consistent with previous studies [51]. DNA damage analysis by LAPCR showed presence of significantly higher number of DNA strand breaks in SNCA-tri NPC cells compared to control NPC cells (Fig.…”

β2-Adrenoreceptor is a regulator of the α-synuclein gene driving risk of Parkinson’s disease

“…Increased levels of wild-type α-synuclein cause mitochondrial impairment and an increase in superoxide and other reactive oxygen species (28, 29), possibly because of interference with mitochondrial protein import (30). We tested whether clenbuterol may be helpful in normalizing SNCA expression levels in human iPSC derived neuronal cells of a patient carrying the SNCA triplication.…”

“…Furthermore, PD patient–derived neuronal precursor cells carrying the pathogenic SNCA locus triplication show increased mitochondria associated superoxide production and reduced viability under exposure to the environmental mitochondrial complex I toxin rotenone (28). Clenbuterol treatment ameliorated this increased mitochondria-associated superoxide production (Fig.…”

The genetic architecture of mitochondrial dysfunction in Parkinson’s disease

“…3c). Indeed, increased cellular stress and ROS levels have been observed in stem cell-derived neuronal precursor cells of a PD patient carrying a SNCA triplication (Flierl et al 2014). Pukaß and colleagues showed that the application of mitochondrial stressors induced a decrease of autophagic clearance of alpha-synuclein, which causes alpha-synuclein accumulation (Pukaß et al 2015).…”