UNRAVELLING PATHOPHYSIOLOGY OF CHCHD2 IN PARKINSON'S DISEASE USING HUMAN MIDBRAIN-LIKE ORGANOIDS

Abstract

Missense mutations of CHCHD2, encoding a mitochondria intermembrane space protein, have been identified in autosomal-dominant late-onset and sporadic Parkinson’s disease (PD). To study the physiological function and the effect of pathogenic mutation Thr61Ile, we generated human midbrain-like organoids (hMLOs) with tyrosine hydroxylase (TH) – EGFP reporter carrying CHCHD2 deletion or Thr61Ile mutation. Here, we showed that CHCHD2 perturbations cause age-dependent PD pathological phenotypes including loss of midbrain dopaminergic (mDA) neurons, reduced dopamine production and mDA neuron electrophysiology defects. This is associated with age-dependent mitochondria dysfunctions such as reduced ATP production and complex IV level, and increased mitochondria reactive oxygen species (ROS) specifically in mDA neurons. As a result, hMLOs with CHCHD2 perturbations are more prone to rotenone and α-synuclein toxicity. Additionally, Thr61Ile mutation is associated with an age-dependent increase of insoluble CHCHD2, likely contributing to abnormal protein aggregates seen in PD. Overall, we have developed novel CHCHD2 knockout and mutant human organoid models and demonstrated biochemical and electrophysiologic evidence of age-dependent neurodegeneration and mitochondrial dysfunctions, recapitulating features seen in human post-mortem CHCHD2 carriers. Our organoids can be used as tractable models to examine disease progression, identify potential biomarkers and for therapeutic screenings.