Disease modeling of desmosome-related cardiomyopathy using induced pluripotent stem cell-derived cardiomyocytes

Cardiomyopathy is a pathological condition characterized by cardiac pump failure due to myocardial dysfunction and the major cause of advanced heart failure requiring heart transplantation.Although optimized medical therapies have been developed for heart failure during the last few decades,some patients with cardiomyopathy exhibit advanced heart failure and are refractory to medical therapies.Desmosome,which is a dynamic cell-to-cell junctional component,maintains the structural integrity of heart tissues.Genetic mutations in desmo-somal genes cause arrhythmogenic cardiomyopathy(AC),a rare inheritable disease,and predispose patients to sudden cardiac death and heart failure.Recent advances in sequencing technologies have elucidated the genetic basis of cardiomyopathies and revealed that desmosome-related cardiomyopathy is concealed in broad cardiomyopathies.Among desmosomal genes,mutations in PKP2(which encodes PKP2)are most frequently identified in patients with AC.PKP2 deficiency causes various pathological cardiac phenotypes.Human cardiomyocytes differentiated from patient-derived induced pluripotent stem cells(iPSCs)in combination with genome editing,which allows the precise arrangement of the targeted genome,are powerful experimental tools for studying disease.This review summarizes the current issues associated with practical medicine for advanced heart failure and the recent advances in disease modeling using iPSC-derived cardiomyocytes targeting desmosome-related cardiomyopathy caused by PKP2 deficiency.

The role of YAP in the control of the metastatic potential of oral cancer

The Yes-associated protein(YAP)is a downstream effector of the Hippo pathway and acts as a key transcription co-factor to regulate cell migration,proliferation,and survival.The Hippo pathway is evolutionarily conserved and controls tissue growth and organ size.Dysregulation and heterogeneity of this pathway are found in cancers,including oral squamous cell carcinoma(OSCC),leading to overexpression of YAP and its regulated proliferation machinery.The activity of YAP is associated with its nuclear expression and is negatively regulated by the Hippo kinase-mediated phosphorylation resulting in an induction of its cytoplasmic translocation.This review focuses on the role of YAP in OSCC in the context of cancer metastatic potential and highlights the latestfindings about the heterogeneity of YAP expression and its nuclear transcription activity in oral cancer cell lines.The review also discusses the potential target of YAP in oral cancer therapy and the recentfinding of the unprecedented role of the desmosomal cadherin desmoglein-3(DSG3)in regulating Hippo-YAP signaling.

Alterations in cell adhesion proteins and cardiomyopathy

Cell adhesive junction is specialized intercellular struc-ture composed of cell adhesion proteins. They are essential to connect adjacent heart muscle cell and make heart contraction effectively and properly. Clini-cal and genetic studies have revealed close relationship between cell adhesive proteins and the occurrence of various cardiomyopathies. Here we will review recent development on the disease phenotype, potential cel-lular and molecular mechanism related to cell adhesion molecules, with particular disease pathogenesis learned from genetic manipulated murine models.

Reactivation of PPARαalleviates myocardial lipid accumulation and cardiac dysfunction by improving fatty acidβ-oxidation in Dsg2-deficient arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy(ACM),a fatal heart disease characterized by fibroadipocytic replacement of cardiac myocytes,accounts for 20%of sudden cardiac death and lacks effective treatment.It is often caused by mutations in desmosome proteins,with Desmoglein-2(DSG2)mutations as a common etiology.However,the mechanism underlying the accumulation of fibrofatty in ACM remains unknown,which impedes the development of curative treatment.Here we investigated the fat accumulation and the underlying mechanism in a mouse model of ACM induced by cardiac-specific knockout of Dsg2(CS-Dsg2^(-/-)).Heart failure and cardiac lipid accumulation were observed in CSDsg2^(-/-)mice.We demonstrated that these phenotypes were caused by decline of fatty acid(FA)β-oxidation resulted from impaired mammalian target of rapamycin(m TOR)signaling.Rapamycin worsened while overexpression of m TOR and 4EBP1 rescued the FAβ-oxidation pathway in CS-Dsg2^(-/-)mice.Reactivation of PPARa by fenofibrate or AAV9-Ppara significantly alleviated the lipid accumulation and restored cardiac function.Our results suggest that impaired m TOR-4EBP1-PPARa-dependent FAβ-oxidation contributes to myocardial lipid accumulation in ACM and PPARa may be a potential target for curative treatment of ACM.

Desmoplakin and clinical manifestations of desmoplakin cardiomyopathy

Desmoplakin(DSP),encoded by the DSP gene,is the main desmosome component and is abundant in the myocardial tissue.There are three DSP isoforms that assume the role of supporting structural stability through intercellular adhesion.It has been found that DSP regulates the transcription of adipogenic and fibrogenic genes,and maintains appropriate electrical conductivity by regulating gap junctions and ion channels.DSP is essential for normal myocardial development and the maintenance of its structural functions.Studies have suggested that DSP gene mutations are associated with a variety of hereditary cardiomyopathy,such as arrhythmia cardiomyopathy,dilated cardiomyopathy(DCM),left ventricular noncompaction,and is also closely associated with the Carvajal syndrome,Naxos disease,and erythro-keratodermia-cardiomyopathy syndrome with skin and heart damage.The structure and function of DSP,as well as the clinical manifestations of DSP-related cardiomyopathy were reviewed in this article.

Mutations of Desmoglein‑2 in Sudden Unexplained Death in the Chinese Han Population

Sudden unexplained death(SUD)remains a puzzle in forensic medicine.Desmoglein‑2(DSG2)has been linked to arrhythmogenic right ventricular cardiomyopathy which may cause life‑threatening ventricular arrhythmias and sudden death.Fatal arrhythmias resulting in sudden death also occur in the absence of morphologic cardiac abnormalities at autopsy.We hypothesized that DSG2 mutations may be responsible for certain Chinese SUD cases.We sequenced all 15 exons of DSG2 in DNA extracted from postmortem heart tissues of 25 Chinese patients dying from SUD.The primers were designed using the Primer Express 3.0 software.Direct sequencing for both sense and antisense strands was performed with a BigDye Terminator DNA sequencing kit on a 3130 Xl Genetic Analyzer.Mutation damage prediction was made using Mutation Taster,PolyPhen,and SIFT software.In 2 of 25 cases of Chinese SUD samples,two DSG2 heterozygous mutations(p.P927 L and p.T1070M)were identified,and one is probably damaging.We concluded that DSG2 mutations may be related to the occurrence of part of SUD cases in the Chinese Han population.