Objective: To functional characterise and phenotype the genetic Parkinson’s disease (PD) patient with an A30P point mutation in SNCA using midbrain dopaminergic neurons (mDANs) vs non-PD age-matched and gender-matched control.

Background: PD is the most common movement disorder and currently affects over 1.2 million people across Europe with approximately 1000 PD cases in Luxembourg. The annual cost of PD is estimated to be 13.9 billion euros while the number of people with PD is set to double by 2030 with an increasing ageing population. The selective degeneration of A9 mDANs in the substantia nigra and presence of intracytoplasmic Lewy Bodies in the neurons that remain is one of the hallmarks of PD. Point mutations, including duplications and triplications of the SNCA gene that encodes α-synuclein leads to an autosomal dominant form of inheritance, with variability at the SNCA locus being a significant risk factor in idiopathic PD. Misfolding and the oligomerisation of this monomeric alpha synuclein protein as a result of these mutations into toxic aggregates of amyloid-like fibrils is one of the main pathogenic features of alpha-synuclein, with alpha synuclein one of the main constituents of Lewy Bodies.

Methods: The mDANs were derived from induced pluripotent stem cells (iPSCs) via small molecule neuronal precursor cell (smNPC) induction protocol (Reinhardt et al., Plos One 2013). These neurons were directly differentiated up to 90 days before being functionally characterised using multi-electrode arrays and mass spectrometry with phenotype detected using protein immunoblotting, metabolomic tracer experiments and live cell imaging.

Results: The patient-derived SNCA (A30P) mDANs were found to secrete more dopamine upon following depolarisation compared to the non-PD control; display lower electrophysiological activity, a slower TCA cycle and selectively vulnerability to ER stressor Tunicamycin characterised by the loss of the rate-limiting dopamine metabolism enzyme Tyrosine Hydroxylase (TH).

Conclusions: Our data for the first time functionally characterises and phenotypes the specific SNCA (A30P) point mutation in-vitro using patient-derived mDANs. Further work is ongoing on the elucidation of the mechanism with attenuation of phenotype using high-throughput compound screening.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/functional-characterisation-and-the-selective-vulnerability-of-snca-a30p-patient-derived-midbrain-dopaminergic-neurons-to-er-stress/