Modelling synucleinopathies with human neurons derived from embryonic stem cells over-expressing α-Synuclein
α-Synuclein (αSyn) is a small intrinsically disordered protein that drives the progression of a group of neurological disorders known of synucleinopathies, including Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. Increased expression of αSyn due to gene duplication or triplication causes familial forms of these diseases, of which the severity is positively correlated with the gene copy number. Despite extensive efforts using various models, the precise mechanisms of αSyn toxicity in neurons have not been elucidated. This could be partly due to biological differences between the models and authentic human neurons. In an attempt to model synucleinopathies with human neurons, I have established a collection of transgenic human embryonic stem cell (hESC) lines over-expressing αSyn. I first showed that elevated αSyn expression does not affect hESC proliferation and their differentiation potential towards neurons. Then I identified transgenic hESC lines that maintained high αSyn expression in differentiated neurons and compared the rate of reactive oxygen species (ROS) production in high versus normal αSyn expressing cortical neuronal cultures. I observed a significantly elevated level of ROS production in αSyn over-expressing neurons in less mature neurons; however, there was no difference observed in more mature neurons. The possible reasons that lead to this difference are discussed. This is the first report of stable αSyn overexpressing hESC lines, which can provide an unlimited source of human neurons for studying the mechanism underlying neuronal cell death in synucleinopathies, which in turn could lead to the development of potential therapeutics.