Author(s): VARANAUSKATE, B., STONALL, C., BALLESTREM, C., Institution: MANCHESTER UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 1580

INTRODUCTION:
Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disease characterized by fibro-fatty replacement of the myocardium, ventricular arrhythmias, and a high risk of sudden cardiac death, particularly in young individuals and competitive athletes. The disease is primarily caused by mutations in desmosome genes. Desmosomes are intercellular junctions that couple epithelial cells and cardiomyocytes to provide resistance to mechanical stresses and support electrical conduction. Among desmosome proteins, plakophilin (PKP) plays a critical role in maintaining desmosome integrity and overall cardiac tissue cohesion with only isoform 2 (PKP2) expressed in the heart. Pathogenic PKP2 variants are found in up to 50% of ACM patients. To bridge the current gap in understanding why PKP2 mutations leave the heart vulnerable to exertion, this study investigates how differential PKP2 expression supports desmosome function.
METHODS:
MDCK epithelial cells were used as an established cell model to study desmosomes. Knockout (KO) experiments were carried out using CRISPR-Cas9 system, whereas overexpression studies were done using transient expression of recombinant PKP proteins tagged with fluorophores. Data were quantified by staining desmosome marker desmoplakin using microscopy. The effect of PKP2 KO and overexpression on desmosome numbers was quantified with Student’s t-test with alpha set to 0.05.
RESULTS:
Knockout of PKP2 lead to a significant reduction in desmosome number, whereas PKP2 overexpression significantly increased desmosome formation. Notably, total KO of PKPs in this cell line (PKP2,3) completely abolished desmosome formation, highlighting the critical roles of plakophilins in desmosome integrity. Since cardiomyocytes only express PKP2, the total PKP-KO model in MDCK cells effectively mimics the loss of plakophilin function in the heart. Interestingly, PKP2 overexpression significantly enhanced desmosome assembly by increasing total desmosome numbers by 30.15%.
CONCLUSION:
Our findings highlight the crucial role of PKP2 in regulating desmosome expression and maintaining cardiac cell adhesion integrity. Our results provide mechanistic insight into how PKP2 haploinsufficiency, a characteristic of ACM, contributes to the pathological remodelling of the myocardium and the progressive deterioration of cardiac performance. Our data suggest that modulating PKP2 expression could be a promising therapeutic strategy for enhancing desmosome number and stability, thereby supporting the potential development of gene therapy approaches in ACM. As current treatment strategies rely mainly on preventing sudden cardiac arrest rather than addressing disease progression, PKP2-focused therapies could offer a novel approach to managing ACM.