Most heart conditions leading to sudden death or impaired cardiac pumping functions in the young people (<35 years old) are the results of genetic mutations inherited from parents. It is very difficult to find curative therapy for these inherited heart diseases due to late diagnosis and lack of understanding in how genetic mutations cause these diseases. One of these inherited heart diseases is named arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). The signature features of sick ARVD/C hearts are progressive heart muscle loss and their replacement by fat and scare tissues, which can lead to lethal irregular heart rhythms and/or heart failure. We have made a significant breakthrough and successfully modeled the sick ARVD/C heart muscles within two months in cell cultures using versatile stem cells derived from ARVD/C patients’ skin cells with genetic mutations in one of the desmosomal (a specific type of cell-cell junctions in hearts) proteins, named plakophilin-2. These disease-specific stem cells can give rise to heart cells, which allow us to discover specific abnormalities in heart energy consumption of ARVD/C heart muscles that causes dysfunction and death of these diseased heart cells. In the Year 1 of this grant support, we have made and characterized additional stem cells lines from ARVD/C patients with different desmosomal mutations. We are in the process to determine if heart muscles derived from these new ARVD/C patient-specific stem cells have common disease-causing mechanisms as we had published. We found two proposed therapeutic agents are ineffective in suppressing ARVD/C disease in culture but we have identified one potential drug that suppressed the loss of ARVD/C heart cells in culture. We also started to establish a known ARVD/C mouse model for future preclinical drug testing.