Modeling the pathophysiology of Parkinson’s disease in patient-specific neurons
The 30 trillion cells that self-assemble into a human being originate from the pluripotent stem cells in the inner cell mass of a human blastocyst. The discovery of induced pluripotent stem cells (iPSCs) makes it possible to approximate various aspects of this natural developmental process artificially by generating materials that can be used in invasive mechanistic studies of virtually all human conditions. In Parkinson’s disease, instructions computed by the basal ganglia to control voluntary motor functions break down, leading to widespread rhythmic bursting activities in the basal ganglia and beyond. It is thought that these oscillatory neuronal activities, which disrupt aperiodic neurotransmission in a normal brain, may reduce information content in the instructions for motor control. Using midbrain neuronal cultures differentiated from iPSCs of Parkinson’s disease patients with parkin mutations, we find that parkin mutations cause oscillatory neuronal activities when dopamine D1-class receptors are activated. This system makes it possible to study the molecular basis of rhythmic bursting activities in Parkinson’s disease. Further development of stem cell models of Parkinson’s disease will enable better approximation of the situation in the brain of Parkinson’s disease patients. In this review, I will discuss what has been found in the past about the pathophysiology of motor dysfunction in Parkinson’s disease, especially oscillatory neuronal activities and how stem cell technologies may transform our abilities to understand the pathophysiology of Parkinson’s disease. Impact statement Research on the pathophysiology of Parkinson’s disease (PD) has generated effective therapies such as deep brain stimulation. A better understanding of PD pathophysiology calls for patient-specific materials amenable for invasive mechanistic studies. In this minireview, I discuss our recent work on oscillatory neuronal activities in midbrain neurons differentiated from induced pluripotent stem cells (iPSCs) of PD patients with parkin mutations. These patient-specific neurons enable a variety of studies previously not feasible in the human system. Further development in stem cell technologies may generate more realistic models for us to decipher PD pathophysiology. These new developments will transform research and development in Parkinson’s disease.