SUMMARY
Intercalated disks (ICDs) connect the termini of adjacent cardiomyocytes (CMs) physically, electrically, and
chemically. The structural role of ICDs to preserve CM integrity in the face of billions of cycles of forceful con-
traction and relaxation is well appreciated; however, the function of ICDs as essential CM signaling hubs is
only now emerging. Arrhythmogenic cardiomyopathy (ACM) provides a unique window into the function of
ICDs and specifically desmosomes. ACM is a potentially lethal disorder characterized by high arrhythmia bur-
den, loss of contractile myocardium, and replacement by fibro-fatty tissue. Mutations of desmosome genes
(PKP2, DSG2, DSC2, DSP, JUP) occur in approximately half of ACM patients. Despite growing knowledge
about ACM disease pathogenesis, the mechanistic links between desmosome mutations and arrhythmias, my-
ocardial dysfunction, and fibrofatty replacement remain poorly understood.
The overall goal of this proposal is to gain insights into the mechanisms by which desmosome mutations
cause arrhythmia and myocardial dysfunction; Our overarching hypothesis is that desmosomes are inte-
gral for maintaining normal cardiomyocyte homeostasis through both their structural and signaling
activities. ACM mutations disrupt these activities to cause both loss of structural integrity and aberrant
signaling. We will test these hypotheses through four parallel but complementary Specific Aims: (1) We will
examine cell composition and gene regulation of human ACM myocardium, using concurrent single nucleus
RNA-seq and ATAC-seq, and spatial transcriptomics (snMulti-seq) with massively parallel single molecule fluo-
rescent in situ hybridization (MERFISH); (2) We will use mosaic, adult, cardiomyocyte specific inactivation of
Dsp to probe the cell autonomous functions of desmosomes. This model will be studied using snMulti-seq and
MERFISH, followed by interrogation of key predicted regulators using in vivo gain- and loss-of-function ap-
proaches; (3) Using proximity proteomics of ICD component N-cadherin, we identified novel ICD components
and ICD components that are altered by Dsp ablation. We will use in vivo gain- and loss-of-function ap-
proaches to study the function of selected candidates identified by this screen; (4) Define the contributions of
WNT and GSK3 signaling to ACM phenotypes in DSP mutant hiPSC-CMs. Using genetic approaches in bioen-
gineered hiPSC-CMs, we will dissect the involvement of GSK3 and WNT signaling to ACM pathogenesis.
Impact: This proposal will advance our understanding of the function of desmosomes and ICDs in CM
homeostasis and the molecular pathogenesis of ACM. This knowledge will accelerate efforts to develop
targeted ACM therapies.