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Background: Although mutations of several genes are associated with arrhythmogenic right ventricular cardiomyopathy (ARVC), the exact correlation between genotype and ventricular arrhythmia features remains unclear. This study was aimed to examine the possible association of the 9 known genes of ARVC with clinical and electrophysiological characteristics., Methods and Results: Ninety subjects diagnosed with ARVC who underwent electrophysiological study were recruited for screening the 9 known ARVC-causing genes. A total of 53 mutations were identified in 57 (63%) subjects. Mutation carriers had more frequent clinical ventricular tachycardia (VT; 89% versus 55%; P<0.001) and negative T waves in V1 to V3 (61% versus 33%; P=0.016). Subjects with plakophilin-2 (PKP2) mutations also had more frequent VT than those without mutations in PKP2. Comparison between subjects with multiple and single mutations showed that syncope occurred more often in the former group (58% versus 24%; P=0.018). VT was significantly more often induced in mutation carriers compared with noncarriers (75% versus 39%; P=0.001), as well as in PKP2 mutation carriers compared with subjects without PKP2 mutations (80% versus 48%; P=0.002). Induced VT with a rate ≥ 200 bpm was more often documented in mutation carriers (88% versus 54%; P=0.013), as well as in PKP2 mutation carriers (91% versus 67%; P=0.041)., Conclusions: Pathogenic gene mutations were found in nearly two thirds of subjects diagnosed with ARVC. Mutation carriers, especially PKP2, had a higher proportion of a history of VT and more inducible fast VT.

The recent decline in fertility is a serious problem in the dairy industry. To overcome this problem, we performed a genome-wide association study using 384 Holsteins and identified four loci associated with conception rates. Two of them contained gap junction-related genes: PKP2 and CTTNBP2NL. Further analysis confirmed that PKP2 increased connexin 43, a gap junction protein, whereas CTTNBP2NL dephosphorylated connexin 43. Knockdown of PKP2 or overexpression of CTTNBP2NL inhibited embryo implantation in mice. The other two loci contained neuroendocrine-related genes: SETD6 and CACNB2. Additional experiments indicated that SETD6 is involved in the transcriptional regulation of gonadotropin-releasing hormone, whereas CACNB2 controlled the secretion of follicle-stimulating hormone in cattle. The total allele substitution effect of these genes on conception rate was 3.5%. Our findings reveal important roles for gap junction communication and the neuroendocrine system in conception and suggest unique selection methods to improve reproductive performance in the livestock industry.

Objectives: The aim of this study was to determine if exercise testing could expose a latent electrical substrate of arrhythmogenic right ventricular cardiomyopathy (ARVC) in asymptomatic gene carriers., Background: Management of asymptomatic ARVC gene carriers is challenging because of variable penetrance of disease and the recognition that sudden cardiac death may be the first clinical manifestation., Methods: Exercise-induced abnormalities during exercise treadmill testing (ETT) were initially compared in 60 subjects: 30 asymptomatic ARVC gene carriers and 30 healthy controls. In phase 2 of the study, ETT results of 25 patients with ARVC with histories of sustained ventricular arrhythmia or cardiac arrest were evaluated to determine if ETT abnormalities in asymptomatic gene carriers were common to patients with a malignant electrical form of the disease., Results: Depolarization abnormalities during ETT were found to develop more frequently in asymptomatic gene carriers compared with healthy controls: epsilon waves appeared in 4 of 28 (14%) compared with 0 of 30 (0%) (p = 0.048), premature ventricular contractions in 17 of 30 (57%) compared with 3 of 30 (10%) (p = 0.0003), and new QRS terminal activation duration ≥ 55 ms in 7 of 22 (32%) compared with 2 of 29 (7%) (p = 0.03). Superior axis premature ventricular contractions occurred only in gene carriers. In the second phase of the study, the frequency of these abnormalities was found to be high in patients with symptomatic ARVC: new epsilon waves appeared in 3 of 18 (17%), superior axis premature ventricular contractions in 21 of 25 (84%), and new terminal activation duration ≥ 55 ms in 8 of 12 (67%)., Conclusions: Exercise testing exposes a latent electrical substrate in asymptomatic ARVC gene carriers that is shared by patients with ARVC with histories of ventricular arrhythmia. ETT may be useful in guiding treatment decisions, exercise prescription, and prioritizing medical surveillance in asymptomatic ARVC gene carriers., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The aim of this study was to identify the incremental value and optimal role of cardiac magnetic resonance (CMR) imaging in arrhythmic risk stratification of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C)-associated desmosomal mutation carriers without histories of sustained ventricular arrhythmia., Background: Risk stratification of ARVD/C mutation carriers is challenging., Methods: Sixty-nine patients (mean age 27.0 ± 15.3 years, 42% men) harboring ARVD/C-associated pathogenic mutations (83% plakophilin 2) without prior sustained ventricular arrhythmias were included. Electrocardiographic and 24-h Holter monitoring findings closest to presentation were analyzed for electrical abnormalities per revised task force criteria. CMR studies were done to identify abnormal cardiac structure and function according to the revised task force criteria., Results: Overall, 42 patients (61%) presented with electrical abnormalities on the basis of electrocardiography and Holter monitoring, of whom 20 (48%) had abnormal results on CMR. Only 1 of 27 patients (4%) without electrical abnormalities at initial evaluation had abnormal CMR results. Over a mean follow-up period of 5.8 ± 4.4 years, 11 patients (16%) experienced sustained ventricular arrhythmias, exclusively in patients with both electrical abnormalities (electrocardiography and/or Holter monitoring) and abnormal CMR results., Conclusions: These results suggest that electrical abnormalities on electrocardiography and Holter monitoring precede detectable structural abnormalities in ARVD/C mutation carriers. Therefore, evaluation of cardiac structure and function using CMR is probably not necessary in the absence of baseline electrical abnormalities. Among ARVD/C mutation carriers, the presence of both electrical and CMR abnormalities identifies patients at high risk for events and thus patients who might benefit from prophylactic implantable cardioverter-defibrillator placement., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Desmosomes are dynamic junctions between cells that maintain the structural integrity of skin and heart tissues by withstanding shear forces. Mutations in component genes cause life-threatening conditions including arrhythmogenic right ventricular cardiomyopathy, and desmosomal proteins are targeted by pathogenic autoantibodies in skin blistering diseases such as pemphigus. Here, we review a set of newly discovered pathogenic alterations and discuss the structural repercussions of debilitating mutations on desmosomal proteins. The architectures of native desmosomal assemblies have been visualized by cryo-electron microscopy and cryo-electron tomography, and the network of protein domain interactions is becoming apparent. Plakophilin and desmoplakin mutations have been discovered to alter binding interfaces, structures, and stabilities of folded domains that have been resolved by X-ray crystallography and NMR spectroscopy. The flexibility within desmoplakin has been revealed by small-angle X-ray scattering and fluorescence assays, explaining how mechanical stresses are accommodated. These studies have shown that the structural and functional consequences of desmosomal mutations can now begin to be understood at multiple levels of spatial and temporal resolution. This review discusses the recent structural insights and raises the possibility of using modeling for mechanism-based diagnosis of how deleterious mutations alter the integrity of solid tissues., (© 2013. Published by Elsevier Ltd. All rights reserved.)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary heart muscle disease characterized by progressive myocardial loss, with fibro-fatty replacement, and high frequency of ventricular arrhythmias that can lead to sudden cardiac death. ARVC is a genetically determined disorder, usually caused by point mutations in components of the cardiac desmosome. Conventional mutation screening of ARVC genes fails to detect causative mutations in about 50% of index cases, suggesting a further genetic heterogeneity. We performed a genome-wide linkage study and a copy number variations (CNVs) analysis, using high-density SNP arrays, in an ARVC family showing no mutations in any of the desmosomal genes. The CNVs analysis identified a heterozygous deletion of about 122 kb on chromosome 12p11.21, including the entire plakophilin-2 gene and shared by all affected family members. It was not listed on any of available public CNVs databases and was confirmed by quantitative real-time PCR. This is the first SNP array-based genome-wide study leading to the identification of a CNV segregating with the disease phenotype in an ARVC family. This result underscores the importance of performing additional analysis for possible genomic deletions/duplications in ARVC patients without point mutations in known disease genes.

Loss of fragile X mental retardation protein (FMRP) causes synaptic dysfunction and intellectual disability. FMRP is an RNA-binding protein that controls the translation or turnover of a subset of mRNAs. Identifying these target transcripts is an important step toward understanding the pathology of the disease. Here, we show that FMRP regulates actin organization and neurite outgrowth via the armadillo protein p0071. In mouse embryonic fibroblasts (MEFs) lacking FMRP (Fmr1-), the actin cytoskeleton was markedly reorganized with reduced stress fibers and F-actin/G-actin ratios compared to fibroblasts re-expressing the protein. FMRP interfered with the translation of the p0071 mRNA in a 3'-UTR-dependent manner. Accordingly, FMRP-depleted cells revealed elevated levels of p0071 protein. The knockdown of p0071 in Fmr1- fibroblasts restored stress fibers and an elongated cell shape, thus rescuing the Fmr1- phenotype, whereas overexpression of p0071 in Fmr1+ cells mimicked the Fmr1- phenotype. Moreover, p0071 and FMRP regulated neurite outgrowth and branching in a diametrically opposed way in agreement with the negative regulation of p0071 by FMRP. These results identify p0071 as an important and novel FMRP target and strongly suggest that impaired actin cytoskeletal functions mediated by an excess of p0071 are key aspects underlying the fragile X syndrome.

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heritable cardiac disease predominantly caused by mutations in desmosomal protein genes. Previous genetic analyses of the Chinese ARVC population are limited to small size and restriction to a single gene. This study was aimed to investigate the genotype in a large series of Chinese patients with ARVC through comprehensively screening nine ARVC-causing genes., Methods: A total of 100 unrelated ARVC patients and 300 age, gender and ethnicity matched healthy controls were genetically tested with multiplexing targeted resequencing for nine previously reported ARVC-causing genes, including plakophilin-2, desmoplakin, desmoglein-2, desmocollin-2, plakoglobin, transforming growth factor beta-3, transmembrane protein 43, desmin and Lamin A/C., Results: Fifty-nine mutations were identified in 64% of the patients, among which, 93% were located in desmosomal protein genes. Plakophilin-2 mutations accounted for 54% of the total and 58% of the desmosomal mutations, with a truncating mutation type making up about 2/3 of the plakophilin-2 mutations. Only four mutations were found in non-desmosomal genes; two in transmembrane protein 43 and two in transforming growth factor beta-3. Two of them (one of each gene) appeared as single missense mutations. No mutation was identified in desmin or Lamin A/C. Multiple mutations were found in 23% of the patients, with plakophilin-2 being found in 57% of the multi-mutation carriers., Conclusions: Plakophilin-2 was the most common gene mutation that was identified in Chinese ARVC patients. Non-desmosomal genes should be added to desmosomal protein genes when performing molecular genetic screening in patients with suspected ARVC.

Desmosomes are prominent cell-cell adhesive junctions in stratified squamous epithelia and disruption of desmosomal adhesion has been shown to have dramatic effects on the function and integrity of these tissues. During normal physiologic processes, such as tissue development and wound healing, intercellular adhesion must be modified locally to allow coordinated cell movements. The mechanisms that control junction integrity and adhesive strength under these conditions are poorly understood. We utilized a proteomics approach to identify plakophilin-3 associated proteins and identified the 14-3-3 family member stratifin. Stratifin interacts specifically with plakophilin-3 and not with other plakophilin isoforms and mutation analysis demonstrated the binding site includes serine 285 in the amino terminal head domain of plakophilin-3. Stratifin interacts with a cytoplasmic pool of plakophilin-3 and is not associated with the desmosome in cultured cells. FRAP analysis revealed that decreased stratifin expression leads to an increase in the exchange rate of cytoplasmic plakophilin-3/GFP with the pool of plakophilin-3/GFP in the desmosome resulting in decreased desmosomal adhesion and increased cell migration. We propose a model by which stratifin plays a role in regulating plakophilin-3 incorporation into the desmosomal plaque by forming a plakophilin-3 stratifin complex in the cytosol and thereby affecting desmosome dynamics in squamous epithelial cells.

Aims: Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is an inherited cardiomyopathy characterized by fibro-fatty replacement of the right ventricle and ventricular arrhythmias. The major disease-causing genes encode cardiac desmosomal components but are involved in only ∼50% of patients. To identify the missing genetic determinants, we used a candidate gene approach, focusing on the 3'-untranslated region (UTR) of the main ARVC/D gene PKP2 and on additional genes involved in desmosomal structure or function., Methods and Results: We screened a population of 64 ARVC/D probands with no identified mutations in any of the five known desmosomal genes (PKP2, DSG2, DSP, DSC2, and JUP). No putative mutation was identified in the 3'-UTR of PKP2 or in PNN, CTNNA3, CAV1, or PLN coding sequences. In a single proband, we identified two rare heterozygous missense variants affecting evolutionary conserved residues: c.175G>A (p.Gly59Arg) in PERP and c.1811A>G (p.Asp604Gly) in PKP4 (minor allele frequency <0.5% in control population)., Conclusion: Our study suggests that mutations in the candidate genes studied and regulation of PKP2 mRNA via 3'-UTR dependent mechanisms are unlikely to be major causes of ARVC/D in the studied population. Additional studies are needed to investigate the putative effects of rare PKP4 and PERP variants in this disease.

Ectodermal dysplasia-skin fragility syndrome (EDSFS) is an autosomal recessive genodermatosis characterized by skin fragility, palmoplantar hyperkeratosis, onichodystrophy, perioral fissuring and noncicatricial alopecia. It is caused by plakophilin-1 (PKP1) deficiency, which results in desmosomal abnormality and poor intercellular cohesion between the epidermal cells. We report a case with a novel PKP1 mutation in intron 6., (© 2013 British Association of Dermatologists.)

Humans and dogs are both affected by the allergic skin disease atopic dermatitis (AD), caused by an interaction between genetic and environmental factors. The German shepherd dog (GSD) is a high-risk breed for canine AD (CAD). In this study, we used a Swedish cohort of GSDs as a model for human AD. Serum IgA levels are known to be lower in GSDs compared to other breeds. We detected significantly lower IgA levels in the CAD cases compared to controls (p = 1.1 × 10(-5)) in our study population. We also detected a separation within the GSD cohort, where dogs could be grouped into two different subpopulations. Disease prevalence differed significantly between the subpopulations contributing to population stratification (λ = 1.3), which was successfully corrected for using a mixed model approach. A genome-wide association analysis of CAD was performed (n cases = 91, n controls = 88). IgA levels were included in the model, due to the high correlation between CAD and low IgA levels. In addition, we detected a correlation between IgA levels and the age at the time of sampling (corr = 0.42, p = 3.0 × 10(-9)), thus age was included in the model. A genome-wide significant association was detected on chromosome 27 (praw = 3.1 × 10(-7), pgenome = 0.03). The total associated region was defined as a ~1.5-Mb-long haplotype including eight genes. Through targeted re-sequencing and additional genotyping of a subset of identified SNPs, we defined 11 smaller haplotype blocks within the associated region. Two blocks showed the strongest association to CAD. The ~209-kb region, defined by the two blocks, harbors only the PKP2 gene, encoding Plakophilin 2 expressed in the desmosomes and important for skin structure. Our results may yield further insight into the genetics behind both canine and human AD., Competing Interests: The authors have declared that no competing interests exist.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited myocardial disease that predominantly affects the right ventricle and is associated with ventricular arrhythmias that may lead to sudden cardiac death. Mutations within at least seven separate genes have been identified to cause ARVC, however a genetic culprit remains elusive in approximately 50% of cases. Although negative genetic testing may be secondary to pathogenic mutations within undiscovered genes, an alternative explanation may be the presence of large deletions or duplications involving known genes. These large copy number variants may not be detected with standard clinical genetic testing which is presently limited to direct DNA sequencing. We describe two cases of ARVC possessing large deletions involving plakophilin-2 (PKP2) identified with microarray analysis and/or multiplex ligation-dependent probe amplification (MLPA) that would have been classified as genotype negative with standard clinical genetic testing. A deletion of the entire coding region of PKP2 excluding exon 1 was identified in patient 1 and his son. In patient 2, MLPA analysis of PKP2 revealed deletion of the entire gene with subsequent microarray analysis demonstrating a de novo 7.9 Mb deletion of chromosome 12p12.1p11.1. These findings support screening for large copy number variants in clinically suspected ARVC cases without clear disease causing mutations following initial sequencing analysis., (© 2012 John Wiley & Sons A/S.)

Downregulation of adherens junction proteins is a frequent event in carcinogenesis. How desmosomal proteins contribute to tumor formation by regulating the balance between adhesion and proliferation is not well understood. The desmosomal protein plakophilin 1 can increase intercellular adhesion by recruiting desmosomal proteins to the plasma membrane or stimulate proliferation by enhancing translation rates. Here, we show that these dual functions of plakophilin 1 are regulated by growth factor signaling. Insulin stimulation induced the phosphorylation of plakophilin 1, which correlated with reduced intercellular adhesion and an increased activity of plakophilin 1 in the stimulation of translation. Phosphorylation was mediated by Akt2 at four motifs within the plakophilin 1 N-terminal domain. A plakophilin 1 phospho-mimetic mutant revealed reduced intercellular adhesion and accumulated in the cytoplasm, where it increased translation and proliferation rates and conferred the capacity of anchorage-independent growth. The cytoplasmic accumulation was mediated by the stabilization of phosphorylated plakophilin 1, which displayed a considerably increased half-life, whereas non-phosphorylated plakophilin 1 was more rapidly degraded. Our data indicate that upon activation of growth factor signaling, plakophilin 1 switches from a desmosome-associated growth-inhibiting to a cytoplasmic proliferation-promoting function. This supports the view that the deregulation of plakophilin 1, as observed in several tumors, directly contributes to hyperproliferation and carcinogenesis in a context-dependent manner.

Aims: Clinical and electrocardiographic (ECG) presentation of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and idiopathic right ventricular outflow-tract tachycardia (RVOT) may be similar. The aim of the study was to assess the validity and utility of T-wave integral measurement as an ECG discriminator of patients with ARVC and RVOT using a body surface mapping (BSM)., Methods and Results: A 120-channel BSM with quantitative signal analysis of the T-wave integral was performed in 10 patients with ARVC. Results were compared with those obtained from 13 patients with RVOT and a control group of 12 healthy subjects (controls). Age, body mass index, and QRS-axis on surface ECG were not significantly different between the groups. Arrhythmogenic right ventricular cardiomyopathy patients showed a significantly negative T-wave integral in the right lower anterior region of the torso when compared with RVOT (P < 0.001). There was no statistically significant difference between RVOT patients and controls. At a cut-off level of -0.3 mV ms, sensitivity and specificity were 83% [area under curve (AUC) 0.85 ± 0.04 for the comparison of ARVC and RVOT]. These differences were pronounced in ARVC patients with a plakophlin-2 mutation (P < 0.001)., Conclusion: Quantitative analysis of the BSM T-wave integral in distinct anatomical regions discriminates ARVC patients from RVOT patients and controls and may serve as an additional diagnostic tool.

Background: Arrhythmogenic cardiomyopathy (AC) is considered a predominantly right ventricular (RV) desmosomal disease. However, left-dominant forms due to desmosomal gene mutations, including PKP2 variant c.419C>T, have been described. Recently, a nondesmosomal phospholamban (PLN) mutation (c.40&#95;42delAGA) has been identified, causing dilated cardiomyopathy and arrhythmias., Objective: To gain more insight into pathogenicity of the PKP2 variant c.419C>T by cosegregation analysis of the PKP2 variant c.419C>T vs the PLN mutation c.40&#95;42delAGA., Methods: A Dutch family (13 family members, median age 49 years, range 34-71 years) with ventricular tachycardia underwent (1) meticulous phenotypic characterization and (2) screening of 5 desmosomal genes (PKP2, DSC2, DSG2, DSP, JUP) and PLN., Results: Six family members fulfilled 2010 AC Task Force Criteria. Seven had signs of left ventricular (LV) involvement (inverted T waves in leads V4-V6, LV wall motion abnormalities and late enhancement, and reduced LV ejection fraction), including 6 family members with proven AC. The PKP2 variant c.419C>T was found as a single variant in 3 family members, combined with the PLN mutation c.40&#95;42delAGA in 3 others. PLN mutation was found in 9 family members, including the 6 with AC and all 7 with LV involvement. The PLN mutation c.40&#95;42delAGA was found as a single mutation in 6, combined with the PKP2 variant c.419C>T in 3 others. A low-voltage electrocardiogram was seen in 4 of 9 PLN mutation-positive subjects. None of the family members with the single PKP2 variant showed any sign of RV or LV involvement., Conclusions: The PLN mutation c.40&#95;42delAGA cosegregates with AC and with electrocardiographic and structural LV abnormalities. In this family, there was no evidence of disease-causing contribution of the PKP2 variant c.419C>T., (Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Aims: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary heart muscle disorder associated with sudden cardiac death. Its pathophysiology is still poorly understood. We aimed to produce an in vitro cellular model of ARVC using patient-specific induced pluripotent stem cell (iPSC)-derived cardiomyocytes and determine whether the model could recapitulate key features of the disease phenotype., Methods and Results: Dermal fibroblasts were obtained from a 30-year-old man with a clinical diagnosis of ARVC, harbouring a plakophilin 2 (PKP2) gene mutation. Four stable iPSC lines were generated using retroviral reprogramming, and functional cardiomyocytes were derived. Gene expression levels of desmosomal proteins (PKP2 and plakoglobin) in cardiomyocytes from ARVC-iPSCs were significantly lower compared with cardiomyocytes from control iPSCs (P< 0.01); there were no significant differences in the expression of desmoplakin, N-cadherin, and connexin 43 between the two groups. Cardiomyocytes derived from ARVC-iPSCs exhibited markedly reduced immunofluorescence signals when stained for PKP2 and plakoglobin, but similar levels of staining for desmoplakin, N-cadherin, and connexin 43 compared with control cardiomyocytes. Transmission electron microscopy showed that ARVC-iPSC cardiomyocytes were larger and contained darker lipid droplets compared with control cardiomyocytes. After 2 weeks of cell exposure to adiopgenic differentiation medium, ARVC-iPSC cardiomyocytes were found to contain a significantly greater amount of lipid, calculated using Oil Red O staining, compared with controls (734 ± 35.6 vs. 8.1 ± 0.49 a.u., respectively; n = 7, P = 0.001)., Conclusion: Patient-specific iPSC-derived cardiomyocytes display key features of ARVC, including reduced cell surface localization of desmosomal proteins and a more adipogenic phenotype.

Background: Arrhythmogenic cardiomyopathy (AC) is closely associated with desmosomal mutations in a majority of patients. Arrhythmogenesis in patients with AC is likely related to remodeling of cardiac gap junctions and increased levels of fibrosis. Recently, using experimental models, we also identified sodium channel dysfunction secondary to desmosomal dysfunction., Objective: To assess the immunoreactive signal levels of the sodium channel protein NaV1.5, as well as connexin43 (Cx43) and plakoglobin (PKG), in myocardial specimens obtained from patients with AC., Methods: Left and right ventricular free wall postmortem material was obtained from 5 patients with AC and 5 controls matched for age and sex. Right ventricular septal biopsies were taken from another 15 patients with AC. All patients fulfilled the 2010 revised Task Force Criteria for the diagnosis of AC. Immunohistochemical analyses were performed using antibodies against Cx43, PKG, NaV1.5, plakophilin-2, and N-cadherin., Results: N-cadherin and desmoplakin immunoreactive signals and distribution were normal in patients with AC compared to controls. Plakophilin-2 signals were unaffected unless a plakophilin-2 mutation predicting haploinsufficiency was present. Distribution was unchanged compared to that in controls. Immunoreactive signal levels of PKG, Cx43, and NaV1.5 were disturbed in 74%, 70%, and 65% of the patients, respectively., Conclusions: A reduced immunoreactive signal of PKG, Cx43, and NaV1.5 at the intercalated disks can be observed in a large majority of the patients. Decreased levels of Nav1.5 might contribute to arrhythmia vulnerability and, in the future, potentially could serve as a new clinically relevant tool for risk assessment strategies., (Copyright © 2013 Heart Rhythm Society. All rights reserved.)

Cellular reprogramming of somatic cells to patient-specific induced pluripotent stem cells (iPSCs) enables in vitro modelling of human genetic disorders for pathogenic investigations and therapeutic screens. However, using iPSC-derived cardiomyocytes (iPSC-CMs) to model an adult-onset heart disease remains challenging owing to the uncertainty regarding the ability of relatively immature iPSC-CMs to fully recapitulate adult disease phenotypes. Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited heart disease characterized by pathological fatty infiltration and cardiomyocyte loss predominantly in the right ventricle, which is associated with life-threatening ventricular arrhythmias. Over 50% of affected individuals have desmosome gene mutations, most commonly in PKP2, encoding plakophilin-2 (ref. 9). The median age at presentation of ARVD/C is 26 years. We used previously published methods to generate iPSC lines from fibroblasts of two patients with ARVD/C and PKP2 mutations. Mutant PKP2 iPSC-CMs demonstrate abnormal plakoglobin nuclear translocation and decreased β-catenin activity in cardiogenic conditions; yet, these abnormal features are insufficient to reproduce the pathological phenotypes of ARVD/C in standard cardiogenic conditions. Here we show that induction of adult-like metabolic energetics from an embryonic/glycolytic state and abnormal peroxisome proliferator-activated receptor gamma (PPAR-γ) activation underlie the pathogenesis of ARVD/C. By co-activating normal PPAR-alpha-dependent metabolism and abnormal PPAR-γ pathway in beating embryoid bodies (EBs) with defined media, we established an efficient ARVD/C in vitro model within 2 months. This model manifests exaggerated lipogenesis and apoptosis in mutant PKP2 iPSC-CMs. iPSC-CMs with a homozygous PKP2 mutation also had calcium-handling deficits. Our study is the first to demonstrate that induction of adult-like metabolism has a critical role in establishing an adult-onset disease model using patient-specific iPSCs. Using this model, we revealed crucial pathogenic insights that metabolic derangement in adult-like metabolic milieu underlies ARVD/C pathologies, enabling us to propose novel disease-modifying therapeutic strategies.

Humans sleep approximately a third of their lifetime. The observation that individuals with either long or short sleep duration show associations with metabolic syndrome and psychiatric disorders suggests that the length of sleep is adaptive. Although sleep duration can be influenced by photoperiod (season) and phase of entrainment (chronotype), human familial sleep disorders indicate that there is a strong genetic modulation of sleep. Therefore, we conducted high-density genome-wide association studies for sleep duration in seven European populations (N=4251). We identified an intronic variant (rs11046205; P=3.99 × 10(-8)) in the ABCC9 gene that explains ≈5% of the variation in sleep duration. An influence of season and chronotype on sleep duration was solely observed in the replication sample (N=5949). Meta-analysis of the associations found in a subgroup of the replication sample, chosen for season of entry and chronotype, together with the discovery results showed genome-wide significance. RNA interference knockdown experiments of the conserved ABCC9 homologue in Drosophila neurons renders flies sleepless during the first 3 h of the night. ABCC9 encodes an ATP-sensitive potassium channel subunit (SUR2), serving as a sensor of intracellular energy metabolism.

Background:  Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a heart muscle disease caused by desmosomal gene mutations, and presents as ventricular tachycardia and sudden cardiac death. Although the mean age at onset or diagnosis of ARVC/D are reported to be around the 30-40s, the age-dependent clinical and genetic differences remain unknown., Methods and Results:  A total of 35 consecutive Japanese probands (23 male) who were clinically diagnosed with ARVC/D were enrolled in the present study, and genetic analysis of PKP2, DSP, DSG2, and DSC2 was done. The mean age at the first symptom and at diagnosis was 38.6±14.8 years and 40.5±17.7 years, respectively. Probands in whom the onset was cardiopulmonary arrest were significantly younger (22.3±15.3 years) than those with arrhythmia (41.1±13.2 years) or congestive heart failure (45.7±8.5 years). On genetic screening, 19 mutation carriers were identified. Although there was no age dependence for each gene mutation carrier, carriers with PKP2 premature stop codon developed the disease at a significantly younger age than other mutation carriers., Conclusions:  The initial clinical manifestations in some young probands were very severe, and PKP2 mutations with a premature stop codon would be associated with disease onset at a younger age.

Desmosomes in keratinocytes are the most important intercellular adhering junctions that provide structural strength for the epidermis. These junctions are connected directly with desmosomal cadherin proteins. Desmosomal cadherins are divided into four desmogleins (Dsgs), Dsg1-4, and three desmocollins (Dscs), Dsc1-3, all of which are involved in desmosomal adhesion by homo- and/or heterophilic binding between Dsgs and Dscs in a Ca(2+)-dependent manner. Cadherins are present on the cell surface and anchor keratin intermediate filaments (KIFs) to their inner cytoplasmic surface to generate an intracellular KIF-skeletal scaffold through several associate proteins, including plakoglobin, plakophillin, and desmoplakins. As such, the desmosomal contacts between adjacent cells generate an intercellular KIF scaffold throughout the whole epidermal sheet. However, despite these critical roles in maintaining epidermal adhesion and integrity, desmosomes are not static structures. Rather, they are dynamic units that undergo regular remodeling, i.e., assembly and disassembly, to allow for cell migration within the epidermis in response to outside-in signaling during epidermal differentiation. Recently, two cell-cell adhesion states controlled by desmosomes have been recognized, including "stable hyperadhesion (Ca(2+)-independent)" and "dynamic weak-adhesion (Ca(2+)-dependent)" conditions. These conditions are mutually reversible through cell signaling events involving protein kinase C (PKC) and epidermal growth factor receptor. Pemphigus vulgaris (PV) is an autoimmune bullous disease caused by anti-Dsg3 antibodies. Binding of these antibodies to Dsg3 causes endocytosis of Dsg3 from the cell surface and results in the specific depletion of Dsg3 from desmosomes, an event linked to acantholysis in the epidermis. This binding of anti-Dsg3 antibody to Dsg3 in epidermal keratinocytes activates PKC, to generate the "weak-adhesion (Ca(2+)-dependent)" state of desmosomes. The weak-adhesion desmosomes appear to be the susceptible desmosomal state and a prerequisite for Dsg3 depletion from desmosomes, pivotal and specific events leading to PV blistering. These observations allow us to propose a concept for pemphigus blistering disorders as a "desmosome-remodeling impairment disease" involving a mechanism of Dsg3 nonassembly and depletion from desmosomes through PV immunoglobulin G-activated intracellular signaling events., (Copyright © 2012. Published by Elsevier B.V.)

Inherited mutations in the folliculin (FLCN) gene cause the Birt-Hogg-Dubé syndrome of familial hair follicle tumours (fibrofolliculomas), lung cysts and kidney tumours. Though folliculin has features of a tumour suppressor, the precise function of the FLCN gene product is not well characterized. We identified plakophilin-4 (p0071) as a potential novel folliculin interacting protein by yeast two-hybrid analysis. We confirmed the interaction of folliculin with p0071 by co-immunoprecipitation studies and, in view of previous studies linking p0071 to the regulation of rho-signalling, cytokinesis and intercellular junction formation, we investigated the effect of cell folliculin status on p0071-related functions. Folliculin and p0071 partially co-localized at cell junctions and in mitotic cells, at the midbody during cytokinesis. Previously, p0071 has been reported to regulate RhoA signalling during cytokinesis and we found that folliculin deficiency was associated with increased expression and activity of RhoA and evidence of disordered cytokinesis. Treatment of folliculin-deficient cells with a downstream inhibitor of RhoA signalling (the ROCK inhibitor Y-27632) reversed the increased cell migration phenotype observed in folliculin-deficient cells. Deficiency of folliculin and of p0071 resulted in tight junction defects and mislocalization of E-cadherin in mouse inner medullary collecting duct-3 renal tubular cells. These findings suggest that aspects of folliculin tumour suppressor function are linked to interaction with p0071 and the regulation of RhoA signalling.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an uncommon heart disease characterised by arrhythmias, right ventricular scarring, and fibrofatty change. Although mutations in the desmosome have been frequently observed in patients clinically diagnosed with ARVC, recent data have put a direct causal relationship in question. Many patients with ARVC and mutations have not had histological confirmation, and many family members with mutations are not affected. Desmosomal mutations have been found in other cardiac diseases, and the specificity of histopathological features is even in question. We aim to review the purported link between ARVC and the desmosome by a critical analysis of reported data.

The association of estrogen receptor alpha (ERα) expression with differentiated breast tumors presenting a lower metastasis risk could be explained by the estrogen modulation of cell adhesion, motility and invasiveness. Since desmosomes play a crucial role in cell-cell adhesion and may interfere in tumor progression, we studied their regulation by estrogens in human breast cancer and normal mammary cells. Estrogens increased the formation of desmosomes in normal and malignant cells. Furthermore, four desmosomal proteins (desmocollin, γ-catenin, plakophilin and desmoplakin) appeared significantly up-regulated by estrogens in three ERα-expressing cancer cell lines and this effect was reversed by a pure antiestrogen. Finally, silencing of ERα or desmoplakin expression by specific siRNA revealed that estrogen-modulated desmosomal proteins are essential for the estrogenic control of intercellular adhesion. This estrogen modulation of desmosome formation could contribute to the lower invasiveness of ERα-positive tumors and to the integrity of epithelial layers in estrogen target tissues., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Aims: The shRNA-mediated loss of expression of the desmosomal protein plakophilin-2 leads to sodium current (I(Na)) dysfunction. Whether pkp2 gene haploinsufficiency leads to I(Na) deficit in vivo remains undefined. Mutations in pkp2 are detected in arrhythmogenic right ventricular cardiomyopathy (ARVC). Ventricular fibrillation and sudden death often occur in the 'concealed phase' of the disease, prior to overt structural damage. The mechanisms responsible for these arrhythmias remain poorly understood. We sought to characterize the morphology, histology, and ultrastructural features of PKP2-heterozygous-null (PKP2-Hz) murine hearts and explore the relation between PKP2 abundance, I(Na) function, and cardiac electrical synchrony., Methods and Results: Hearts of PKP2-Hz mice were characterized by multiple methods. We observed ultrastructural but not histological or gross anatomical differences in PKP2-Hz hearts compared with wild-type (WT) littermates. Yet, in myocytes, decreased amplitude and a shift in gating and kinetics of I(Na) were observed. To further unmask I(Na) deficiency, we exposed myocytes, Langendorff-perfused hearts, and anaesthetized animals to a pharmacological challenge (flecainide). In PKP2-Hz hearts, the extent of flecainide-induced I(Na) block, impaired ventricular conduction, and altered electrocardiographic parameters were larger than controls. Flecainide provoked ventricular arrhythmias and death in PKP2-Hz animals, but not in the WT., Conclusions: PKP2 haploinsufficiency leads to I(Na) deficit in murine hearts. Our data support the notion of a cross-talk between desmosome and sodium channel complex. They also suggest that I(Na) dysfunction may contribute to generation and/or maintenance of arrhythmias in PKP2-deficient hearts. Whether pharmacological challenges could help unveil arrhythmia risk in patients with mutations or variants in PKP2 remains undefined.

Background: The overt stage of arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C) is preceded by a concealed stage with minor or no signs of disease. However, sudden death may occur in this early phase. Deformation imaging may contribute to early diagnosis. The aims of this study were to compare the diagnostic accuracy of the conventional (1994) versus the recently published (2010) new echocardiographic criteria for ARVD/C and to evaluate the additional value of echocardiographic tissue deformation imaging to detect subclinical RV functional abnormalities in asymptomatic carriers of pathogenic ARVD/C mutations., Methods: Fourteen asymptomatic first-degree relatives of ARVD/C probands (the ARVD/C-r group; mean age, 38.0 ± 13.2 years) with a pathogenic plakophilin-2 mutation and a group of age-matched controls (n = 56; mean age, 38.2 ± 12.7 years) were included at a 1:4 ratio. A complete echocardiographic evaluation (dimensions, global systolic parameters, and visual assessment and deformation imaging of the RV free wall including Doppler tissue imaging and two-dimensional strain echocardiography) was obtained. Peak systolic strain less negative than -18% and/or postsystolic shortening (postsystolic index > 15%) in any RV segment was considered abnormal., Results: RV dimensions in the ARVD/C-r group were similar to those in controls (RV outflow tract, 15.4 ± 2.9 vs 14.4 ± 1.9 mm/m(2), P = NS; RV inflow tract, 18.6 ± 2.6 vs 19.1 ± 2.6 mm/m(2), P = NS), and global systolic parameters were moderately reduced (tricuspid annular plane systolic excursion, 20.0 ± 3.2 vs 23.9 ± 2.8 mm, P = .001; RV fractional area change, 40.3 ± 8.4 vs 40.6 ± 7.1, P = NS). According to task force criteria, 57% of the ARVD/C-r group and 29% of controls were classified as abnormal when applying the 1994 criteria and 29% and 4% when applying the 2010 criteria, respectively. Doppler tissue imaging and two-dimensional strain deformation (and strain rate) values were reduced in the ARVD/C-r group in the basal and mid RV segments compared with controls (P < .001). In the ARVD/C-r group, peak systolic strain less negative than -18% was seen in six patients (43%), postsystolic strain in nine (64%), and either abnormality in 10 (71%), almost exclusively in the basal segment; these findings were observed in none of the controls., Conclusions: The 2010 criteria for ARVD/C improve specificity, whereas sensitivity is significantly reduced in this asymptomatic population. In contrast, echocardiographic deformation imaging detects functional abnormalities in the subtricuspid region in 71% of asymptomatic carriers of a pathogenic plakophilin-2 mutation, while regional deformation was normal in all control subjects, indicating superiority of both sensitivity and specificity with these new modalities., (Copyright © 2012. Published by Mosby, Inc.)

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disorder mainly caused by dominant mutations in several components of the cardiac desmosome including plakophilin-2 (PKP2), the most prevalent disease gene. Little is known about the underlying genetic and molecular mechanisms of missense mutations located in the armadillo (ARM) domains of PKP2, as well as their consequences on human cardiac pathology., Methods and Results: We focused on in vivo and in vitro studies of the PKP2 founder mutation c.2386T>C (p.C796R), and demonstrated in cardiac tissue from 2 related mutation carriers a patchy expression pattern ranging from unchanged to totally absent immunoreactive signals of PKP2 and other desmosomal proteins. In vitro expression analysis of mutant PKP2 in cardiac derived HL-1 cells revealed unstable proteins that fail to interact with desmoplakin and are targeted by degradation involving calpain proteases. Bacterial expression, crystallization, and structural modeling of mutated proteins impacting different ARM domains and helices of PKP2 confirmed their instability and degradation, resulting in the same remaining protein fragment that was crystallized and used to model the entire ARM domain of PKP2., Conclusions: The p.C796R and other ARVC-related PKP2 mutations indicate loss of function effects by intrinsic instability and calpain proteases mediated degradation in in vitro model systems, suggesting haploinsufficiency as the most likely cause for the genesis of dominant ARVC due to mutations in PKP2.

The aim of this investigation was to identify and characterise pathogenic mutations in a sudden cardiac death (SCD) cohort suspected of cardiomyopathy in persons aged 0-40 years. The study material for the genetic screening of cardiomyopathies consisted of 41 cases and was selected from the case database at the Institute of Forensic Medicine. Mutational screening by DNA sequencing was performed to detect mutations in DNA samples from deceased persons suspected of suffering from hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic right ventricle cardiomyopathy (ARVC). A total of 9 of the examined 41 cases had a rare sequence variant in the MYBPC3, MYH7, LMNA, PKP2 or TMEM43 genes, of which 4 cases (9.8%) were presumed to be pathogenic mutations. The presumed pathogenic mutations were distributed with one case of suspected HCM and DCM (MYH7; p.R442H), one case of suspected DCM (LMNA; p.R471H), and two cases of suspected ARVC (PKP2; p.R79X and LMNA; p.R644C). The presented data adds important information on the genetic elements of SCD in the young, and calls for expert pathological evaluation and molecular autopsy in the post-mortem examination of SCD victims with structural anomalies of the heart., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Aims: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by fibrofatty replacement of muscular fibers predominantly in the right ventricle and with ventricular arrhythmias as the main clinical manifestation. Mutations in several components of the desmosome genes have been identified and mutations of the plakophilin-2 (PKP-2) gene are a common cause of ARVC. The aim of this study is to investigate the correlation between genotype and phenotype in a family with a novel PKP-2 variant., Methods and Results: This study describes the clinical findings and genetic analysis in a family with ARVC. A part of the family has been followed clinically long term for up to 27 years. Two not previously reported PKP-2 variants (L506P and T526A) have been identified in this family. Even though all members of this family share the novel variant L506P, the clinical features, i.e., their phenotypes are different. The L506P variant is located in exon 7 and affects a highly conserved residue. The same amino acid, leucine, is present in all species evaluated, indicating a functional importance and the variant is predicted to be damaging. The novel L506P variant in the PKP-2 gene is thus a possible pathogenic alteration in the described family with ARVC. In contrast, the T526A variant is weakly conserved and predicted to be tolerated., Conclusion: While many of the reported ARVC mutations are truncating mutations, the possibly damaging variant found in this family, is a missense alteration affecting a highly conserved residue 506 located in exon 7.

The aberrant DNA methylation of tumor suppressor genes occurs frequently in Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC) and likely affects the initiation and progression of BE to EAC. In the present study, we discovered PKP1 as a novel methylated gene in EAC and then investigated the role of loss of PKP1, a constituent of the desmosome complex found in stratified epithelial layers, on the behavior of Barrett's esophagus and esophageal adenocarcinoma cells. By using primary esophageal tissue samples we determined that PKP1 was rarely methylated in normal squamous esophagus (5/55; 9.1%) and BE (5/39; 12.8%) and more frequently methylated in Barrett's esophagus with high-grade dysplasia (HGD) or EAC (20/60; 33.3%; P < 0.05). Furthermore, PKP1 levels were decreased in BE and HGD/EAC cases compared to normal squamous esophagus cases. Knockdown of PKP1 in the BE cell lines CP-A and CP-D (both normally express PKP1) resulted in increased cell motility. Thus, PKP1 loss secondary to promoter methylation, as well as other mechanisms, may promote the progression of BE to EAC in a subset of patients via decreased desmosome assembly and increased cell motility., (Copyright © 2011 Wiley Periodicals, Inc.)

Objectives: The autosomal dominant form of arrhythmogenic right ventricular cardiomyopathy (ARVC) has been linked to mutations in desmosomal proteins. A mutation in plakophilin 2 (PKP 2) is a frequent cause for ARVC. We describe a new mutation in the PKP2 gene, the genotype-phenotype variation in this mutation and its clinical consequences., Design: Individuals in a three-generation family were investigated after the sudden cardiac death of a young male. Clinical evaluation, electrocardiography, echocardiography, magnetic resonance imaging, endomyocardial biopsy and genetic testing were performed., Results: A novel heterozygote mutation, a c.368G > A transition, located in exon 3 of the PKP2 gene was found (p.Trp123X). The phenotype was characterized by arrhythmia at an early age in some individuals, with mild abnormalities on imaging., Conclusions: This new plakophilin mutation demonstrates variable penetrance and phenotypic expression in ARVC, and highlights the need of genetic testing and thorough phenotype examination in ARVC pedigrees.

Background: Tuberculosis has been associated with genetic variation in host immunity. We hypothesized that single-nucleotide polymorphisms (SNPs) in SIGIRR, a negative regulator of Toll-like receptor/IL-1R signaling, are associated with susceptibility to tuberculosis., Methods: We used a case-population study design in Vietnam with cases that had either tuberculous meningitis or pulmonary tuberculosis. We genotyped 6 SNPs in the SIGIRR gene region (including the adjacent genes PKP3 and TMEM16J) in a discovery cohort of 352 patients with tuberculosis and 382 controls. Significant associations were genotyped in a validation cohort (339 patients with tuberculosis, 376 controls)., Results: Three SNPs (rs10902158, rs7105848, rs7111432) were associated with tuberculosis in discovery and validation cohorts. The polymorphisms were associated with both tuberculous meningitis and pulmonary tuberculosis and were strongest with a recessive genetic model (odds ratios, 1.5-1.6; P = .0006-.001). Coinheritance of these polymorphisms with previously identified risk alleles in Toll-like receptor 2 and TIRAP was associated with an additive risk of tuberculosis susceptibility., Conclusions: These results demonstrate a strong association of SNPs in the PKP3-SIGIRR-TMEM16J gene region and tuberculosis in discovery and validation cohorts. To our knowledge, these are the first associations of polymorphisms in this region with any disease.

Ectodermal dysplasia-skin fragility syndrome (ED-SFS) is a rare autosomal recessive genodermatosis resulting from mutations in the PKP1 gene, encoding the desmosomal plaque protein plakophilin-1 (PKP1). Mutations in PKP1 may manifest with skin fragility and erosions, patches of scale crust on the trunk and limbs, peri-oral cracking and inflammation, hypotrichosis, palmoplantar keratoderma with painful fissuring and other somewhat variable ectodermal anomalies. Ten cases of the syndrome have been reported. We report a further case of this desmosomal genodermatosis. A 14-month old child, born to consanguineous parents, presented with a history of neonatal bullae and subsequent development of dystrophic nails, sparse eyelashes and eyebrows, woolly scalp hair, abnormal dental development and a desquamating erythematous rash at sites of trauma. A clinical diagnosis of ED-SFS was supported by skin biopsy findings of suprabasal intraepidermal clefting and a loss of immunoreactivity for PKP1. Sequencing of genomic DNA revealed a homozygous 5 base pair deletion in exon 5 of the PKP1 gene, designated c.897del5 (CAACC). This new mutation creates a frameshift, leading to a downstream premature termination codon, p.Pro299fsX61. This case highlights the clinicopathological consequences of inherited mutations in the PKP1 gene and illustrates the key role of desmosomes in skin biology., (© 2011 The Authors. Australasian Journal of Dermatology © 2011 The Australasian College of Dermatologists.)

The desmosome anchors keratin filaments in epithelial cells leading to the formation of a tissue wide IF network. Loss of the desmosomal plaque protein plakophilin3 (PKP3) in HCT116 cells, leads to an increase in neoplastic progression and metastasis, which was accompanied by an increase in K8 levels. The increase in levels was due to an increase in the protein levels of the Phosphatase of Regenerating Liver 3 (PRL3), which results in a decrease in phosphorylation on K8. The increase in PRL3 and K8 protein levels could be reversed by introduction of an shRNA resistant PKP3 cDNA. Inhibition of K8 expression in the PKP3 knockdown clone S10, led to a decrease in cell migration and lamellipodia formation. Further, the K8 PKP3 double knockdown clones showed a decrease in colony formation in soft agar and decreased tumorigenesis and metastasis in nude mice. These results suggest that a stabilisation of K8 filaments leading to an increase in migration and transformation may be one mechanism by which PKP3 loss leads to tumor progression and metastasis.

Objective: To examine plakophilin proteins (Pkp) and 3 expression levels in bladder cancer, in particular their levels during cellular growth and invasion. Pkp is associated with the binding of cadherin to intermediate filaments of the cytoskeleton., Methods: The relative mRNA and protein expression levels of Pkp2 and 3 in bladder cancer cell lines were determined using quantitative real-time polymerase chain reaction and Western blot analyses. The cellular localization of Pkp2 and 3 proteins in bladder cancer cells was also assayed using immunohistochemistry. The proliferation and invasive activities of bladder cancer cells were evaluated using cell growth and in vitro cell invasion assays, and were compared with those of bladder cancer cells treated with Pkp2 and 3 small interfering RNAs., Results: Pkp2 mRNA and protein levels were elevated, and those of Pkp3 were reduced, in bladder cancer cells that are known to exhibit increased proliferation and invasive activity. Pkp2/3 protein expression was predominantly observed in the cytoplasm of invasive bladder cancer cells and tissues. Pkp2 knockdown inhibited, and Pkp3 knockdown enhanced, invasion of bladder cancer cells, but these knockdowns did not alter cell proliferation., Conclusion: We conclude that high Pkp2, and low Pkp3, expression is associated with bladder cancer cell invasion and that neither Pkp2 nor Pkp3 is associated with cell proliferation. We further hypothesize that accumulation of Pkp2 and 3 in the cell cytoplasm, rather than their recruitment to the cell membrane, is related to an increased ability of the tumor to invade and metastasize., (Copyright © 2012. Published by Elsevier Inc.)

Desmosomes are intercellular junctions that contribute to cell-cell adhesion, signalling, development and differentiation in various tissues, including the skin. Composed of a network of transmembranous and intracellular plaque proteins, pathogenic autosomal dominant or recessive mutations have been reported in 10 different desmosomal genes, resulting in a spectrum of phenotypes variably affecting skin, hair and heart. This review summarizes the molecular pathology and phenotypes that predominantly affect the skin/hair. Recent desmosomal genodermatoses described include lethal congenital epidermolysis bullosa (plakoglobin), cardiomyopathy with alopecia and palmoplantar keratoderma (plakoglobin), hypotrichosis with scalp vesicles (desmocollin 3), and generalized peeling skin disease (corneodesmosin). Understanding the range of clinical phenotypes in combination with knowledge of the inherent desmosome gene mutation(s) is helpful in managing and counselling patients, as well as providing insight into the biological function of specific components of desmosomes in skin and other tissues., (© 2011 The Authors. BJD © 2011 British Association of Dermatologists.)

The desmosomal armadillo protein plakophilin 2 is the only plakophilin expressed in the heart, and mutations in the human plakophilin 2 gene result in arrhythmogenic right ventricular cardiomyopathy. To investigate loss of function, we knocked down plakophilin 2 by morpholino microinjection in zebrafish. This resulted in decreased heart rate, cardiac oedema, blood pooling, a failure of the heart to pattern correctly and a twisted tail. Co-injection of plakophilin 2 mRNA rescued the morphant phenotype, indicating the specificity of the knockdown. Desmosome numbers were decreased in morphant hearts and the plaque and midline structures of the desmosomes in the intercalated discs were disrupted when examined by electron microscopy. cmlc2 and vmhc expression at 48 hours post-fertilization (hpf) showed incomplete looping of the heart in morphant embryos by whole mount in situ hybridization, and bmp4 expression was expanded into the ventricle. The domain of expression of the heart marker nkx2.5 at 24 hpf was expanded. At the 18 somite stage, expression of the cardiogenic gene lefty2 was abolished in the left cardiac field, with concomitant increases in bmp4, spaw and lefty1 expression, likely resulting in the looping defects. These results indicate that plakophilin 2 has both structural and signalling roles in zebrafish heart development.

Background: Plakophilin2 (PKP2) is a desmosome-related protein with numerous armadillo repeats and has been linked to arrhythmogenic right ventricular cardiomyopathy (ARVC). Fatal arrhythmias resulting in sudden death also occur in the absence of morphologic cardiac abnormalities at autopsy, and have been linked to ion channel mutations in a subset of cases, but so far not to PKP2., Methods and Results: We sequenced all 14 exons of PKP2 in DNA extracted from postmortem heart tissues of 25 patients dying from ARVC and 25 from sudden unexpected death with negative autopsy (SUDNA). 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 3130XL Genetic Analyzer. Mutation damage prediction was made using Mutation Taster, Polyphen and SIFT software. In 6 of the 25 ARVC samples, 6 PKP2 mutations were identified, 4 of which were likely significant, and 3 of which were novel (p.N641del, p.L64PfsX22, p.G269R). In 6 of the 25 cases of SUDNA samples, 6 PKP2 mutations were identified, 3 of which were likely significant, and 4 of which were not previously described (p.P665S, p.Y217TfsX45, p.E540, p.S615T)., Conclusions: PKP2 mutations are not specific for ARVC and may result in SUDNA. The link between ARVC and desmosomal mutations may not be causal but related to an association between defective desmosomal proteins and arrhythmias.

In humans, congenital and hereditary skin diseases associated with epidermal cell-cell separation (acantholysis) are very rare, and spontaneous animal models of these diseases are exceptional. Our objectives are to report a novel congenital acantholytic dermatosis that developed in Chesapeake Bay retriever dogs. Nine affected puppies in four different litters were born to eight closely related clinically normal dogs. The disease transmission was consistent with an autosomal recessive mode of inheritance. Clinical signs occurred immediately after birth with superficial epidermal layers sloughing upon pressure. At three month of age, dogs exhibited recurrent superficial skin sloughing and erosions at areas of friction and mucocutaneous junctions; their coat was also finer than normal and there were patches of partial hair loss. At birth, histopathology revealed severe suprabasal acantholysis, which became less severe with ageing. Electron microscopy demonstrated a reduced number of partially formed desmosomes with detached and aggregated keratin intermediate filaments. Immunostaining for desmosomal adhesion molecules revealed a complete lack of staining for plakophilin-1 and anomalies in the distribution of desmoplakin and keratins 10 and 14. Sequencing revealed a homozygous splice donor site mutation within the first intron of PKP1 resulting in a premature stop codon, thereby explaining the inability to detect plakophilin-1 in the skin. Altogether, the clinical and pathological findings, along with the PKP1 mutation, were consistent with the diagnosis of ectodermal dysplasia-skin fragility syndrome with plakophilin-1 deficiency. This is the first occurrence of ectodermal dysplasia-skin fragility syndrome in an animal species. Controlled mating of carrier dogs would yield puppies that could, in theory, be tested for gene therapy of this rare but severe skin disease of children.

Objectives: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is characterized by fibrofatty replacement of cardiomyocytes. In around 50% of index patients, a genetic predisposition is demonstrated. The purpose of this study was to examine a plakophilin-2 (PKP2) splice site mutation, c.2489+4A>C, identified in 4 separately ascertained Dutch ARVD/C families., Methods: Genealogical studies and comprehensive screening of 5 desmosomal genes were undertaken. Reverse transcriptase PCR (RT-PCR) and subsequent sequencing was performed., Results: An A-to-C change (c.2489+4A>C) near the splice donor site of intervening sequence 12 of PKP2 was found in all 4 families. Based on pedigree data and haplotype sharing, a common ancestor should be situated more than 7 generations ago. RT-PCR demonstrated the presence of aberrant messenger RNA. Clinical manifestations ranged from severe disease to nonpenetrance in elderly mutation carriers., Conclusions: This founder mutation in PKP2 is predicted to lead to the presence of a dysfunctional PKP2 protein, whereas most truncating mutations are expected to lead to loss of protein. Mutation carriers displayed a wide range of disease severity, suggesting that PKP2 mutations alone are not sufficient to cause disease, which results in the variable expression and incomplete penetrance characteristic of ARVD/C mutations., (Copyright © 2012 S. Karger AG, Basel.)

Monomeric actin regulates gene expression through serum response factor (SRF) by inhibiting its transcriptional coactivator myocardin-related transcription factor (MAL/MRTF). Many affected genes encode cytoskeletal components. We have analysed the migratory effects of actin-MAL signalling and of new target genes in non-invasive highly adherent cells. Expression of active MAL impaired migration of both fibroblasts and epithelial cells, whereas dominant-negative constructs and partial knockdown of MAL/MRTF enhanced motility. Knockdown of three newly characterised G-actin-regulated MAL targets, integrin α5, plakophilin 2 (Pkp2) and FHL1, enhanced cell migration. All three were upregulated by external stimulation through actin-MAL-SRF signalling, and MAL and SRF were inducibly recruited to cis-regulatory elements of the integrin α5 and Pkp2 genes. Finally, the reduced migration of epithelial cells stably expressing MAL was partially reversed by knockdown of Pkp2 and FHL1. We conclude that the actin-MAL pathway promotes adhesive gene expression, including integrin α5, Pkp2 and FHL1, and that this is anti-motile for non-invasive cells harbouring high basal activity.

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an uncommon inherited myocardial disorder characterised by fibro-fatty inflammation affecting the right and left ventricles. It most commonly presents with palpitations or syncope but sudden death may occur, especially in young males., Methods: Diagnosis is not possible with a single test and may be difficult. Task Force criteria agreed in 1994 comprise major and minor criteria spanning structural abnormalities, ECG appearances, arrhythmias, family history of premature death and myocardial histology. Modified criteria were introduced in 2010 to improve sensitivity., Results: Arrhythmogenic right ventricular cardiomyopathy is a desmosomal disease. Mutations have been detected in five desmosomal genes, most frequently in plakophilin-2 (PKP2) and multiple mutations are also reported. Antiarrhythmic drugs such as sotalol and amiodarone may improve symptoms but are unproven to increase survival. An implantable defibrillator is appropriate in individuals surviving cardiac arrest or sustained ventricular tachycardia, but there is not yet consensus about prophylactic treatment of Task Force positive but asymptomatic individuals., Conclusions: Arrhythmogenic right ventricular cardiomyopathy is more common than previously believed. Preliminary evidence supports improved sensitivity without loss of specificity using the revised Task Force criteria. The genetics of the disease are complex but should ultimately advance diagnosis and management., (Copyright © 2011 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier B.V. All rights reserved.)

The Boyden chamber assay has been developed for various cell migration and invasion protocols. One variant of the Boyden chamber assay is the pseudopodium isolation assay, which has been developed to identify RNA and proteins localized in pseudopodia cell protrusions. Astrocytes are the most abundant cell type in the CNS and typically extend long cellular protrusions. Increasing interest emerges concerning for example the growth mechanisms and functions of astrocytes in respect to brain development, re-uptake of neurotransmitters in the synaptic cleft and glial scar formation. Protein and RNA localization mechanisms have been extensively examined in neurons and shown to play pivotal roles for the functional presence of specific protein components in neuronal protrusions. Here we present a simple Boyden chamber based method to isolate astrocyte cell protrusions for biochemical analysis. We have succeeded in isolating protrusion localized RNA and protein from the mouse astrocyte cell line, C8-S, and mouse primary astrocytes. This is exemplified in biochemical analyses showing specific localization of the mRNA for Ras-related protein (Rab13), Plakophilin-4 (Pkp4), Ankyrin Repeat Domain 25 (Ankrd25), and inositol polyphosphate-1-phosphatase (Inpp1) in the protrusions of both C8-S cells and primary astrocytes. Concordant, the Pkp4 protein was also predominantly localized in the protrusions of C8-S and primary astrocytes. The described methodology can be the basis for both genome wide and specific descriptive and functional studies of RNA and protein localization in the protrusions of astrocytes which could contribute considerably to the existing knowledge of astrocyte functions in the CNS., (Copyright © 2011 Wiley-Liss, Inc.)