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Background: Plakophilin 2 gene (PKP2) has been revealed to be differentially expressed in various cancer types and is correlated with prognosis. However, the role of PKP2 in colon adenocarcinoma remains indistinct. Methods: Differences in transcriptional expression of PKP2 between colon adenocarcinoma tissues and normal adjacent tissues were acquired from the publicly available dataset—the Cancer Genome Atlas. A receiver operating curve (ROC) was constructed to differentiate colon adenocarcinoma tissues from adjacent normal tissues. The Kaplan–Meier plot method was performed to evaluate the effect of PKP2 on survival. The correlation between mRNA expression of PKP2 and immune infiltrating was determined by the Tumor Immune Estimation Resource and Tumor–Immune System Interaction databases. Results: The expression of PKP2 in colon adenocarcinoma tissues was significantly downregulated compared with corresponding adjacent normal tissues. Decreased PKP2 mRNA expression was associated with lymph node metastases and advanced pathological stage. The ROC curve analysis indicated that with a cutoff value of 6.034, the sensitivity and specificity for PKP2 differentiating the colon adenocarcinoma tissues from the adjacent normal tissues were 90.2 and 66.5% respectively. Kaplan–Meier plot survival analysis revealed that colon adenocarcinoma patients with low‐PKP2 had a worse prognosis than those with high‐PKP2 (68.2 vs. 101.4 months, p = 0.028). Correlation analysis showed that mRNA expression of PKP2 was correlative with immune infiltrates. Conclusions: Downregulated PKP2 is significantly correlated with unfavorable immune infiltrating and survival in colon adenocarcinoma. This research indicates that PKP2 can be selected as a novel biomarker of potential immunotherapy targets and unfavorable prognosis in colon adenocarcinoma. [ABSTRACT FROM AUTHOR]

ACM is a rare hereditary heart disease characterized by a progressive fibro-fatty replacement of the myocardium that can affect either the right or the left ventricle or both. It is mainly caused by variants in the desmosome genes with autosomal dominant transmission and incomplete penetrance. The disease shows a wide spectrum of clinical manifestations, including ventricular arrhythmias, HF and myocarditis. The latter is considered a ‘hot phase’ in the natural history of the disease and must therefore be distinguished from the isolated AM, which is frequently due to viral infections. Our case report is an example of how an AM, as the first manifestation of the disease, helped to reach a diagnosis of ACM through the genetic analysis. In fact, the multi-parametric investigation, which also included CMR and EMB, revealed controversial aspects that led us to perform the genetic test. The latter revealed a heterozygous pathogenic variant in the PKP2 that was considered definitive proof of ACM.

Introduction and objectives: Arrhythmogenic cardiomyopathy (ACM) is a hereditary heart disease defined by the progressive replacement of the ventricular myocardium with fibroadipose tissue, which can act as a substrate for arrhythmias, sudden death, or even give rise to heart failure (HF). Sudden death is frequently the first manifestation of the disease, particularly among young patients. The aim of this study is to describe a new pathogenic variant in the PKP2 gene. Methods: A descriptive observational study that included eight initially non-interrelated families with a diagnosis of ACM undergoing follow-up at our HF and Familial Cardiomyopathies Unit, who were carriers of the NM_004572.3:c.775_776insG; p.(Glu259Glyfs*77) variant in the PKP2 gene. The genetic testing employed next-generation sequencing for the index cases and the Sanger method for the targeted study with family members. We compiled personal and family histories, demographic and clinical characteristics, data from the additional tests at the time of diagnosis, and arrhythmic events at diagnosis and during follow-up. Results: We included 47 subjects, of whom 8 were index cases (17%). Among the evaluated family members, 16 (34%) were carriers of the genetic variant, 3 of whom also had a diagnosis of ACM. The majority were women (26 patients; 55.3%), with a mean age on diagnosis of 48.9 ± 18.6 years and a median follow-up of 39 [24–59] months. Worthy of note are the high incidences of arrhythmic events as the form of presentation and in follow-up (21.5% and 20.9%, respectively), and the onset of HF in 25% of the sample. The most frequent ventricular involvements were right (four patients, 16.7%) and biventricular (four patients, 16.7%); we found no statistical differences in any of the variables analysed. Conclusions: This variant is a pathogenic variant of gene PKP2 that has not previously been described and is not present in the control groups associated with ACM. It has incomplete penetrance, a highly variable phenotypic expressivity, and was identified in eight families of our geographical area in Malaga (Andalusia, Spain), suggesting a founder effect in this area and describe the clinical and risk characteristics. [ABSTRACT FROM AUTHOR]

Abstract Background Aerobic glycolysis is an emerging hallmark of cancer. Although some studies have constructed glycolysis-related prognostic models of colon adenocarcinoma (COAD) based on The Cancer Genome Atlas (TCGA) database, whether the COAD glycolysis-related prognostic model is appropriate for distinguishing the prognosis of rectal adenocarcinoma (READ) patients remains unknown. Exploring critical and specific glycolytic genes related to READ prognosis may help us discover new potential therapeutic targets for READ patients. Results Three gene sets, HALLMARK_GLYCOLYSIS, REACTOME_GLYCOLYSIS and REACTOME_REGULATION_OF_GLYCOLYSIS_BY_FRUCTOSE_2_6_BISPHOSPHATE_METABOLISM, were both significantly enriched in both COAD and READ through glycolysis-related gene set enrichment analysis (GSEA). We found that six genes (ANKZF1, STC2, SUCLG2P2, P4HA1, GPC1 and PCK1) were independent prognostic genes in COAD, while TSTA3 and PKP2 were independent prognostic genes in READ. Glycolysis-related prognostic model of COAD and READ was, respectively, constructed and assessed in COAD and READ. We found that the glycolysis-related prognostic model of COAD was not appropriate for READ, while glycolysis-related prognostic model of READ was more appropriate for READ than for COAD. PCA and t-SNE analysis confirmed that READ patients in two groups (high and low risk score groups) were distributed in discrete directions based on the glycolysis-related prognostic model of READ. We found that this model was an independent prognostic indicator through multivariate Cox analysis, and it still showed robust effectiveness in different age, gender, M stage, and TNM stage. A nomogram combining the risk model of READ with clinicopathological characteristics was established to provide oncologists with a practical tool to evaluate the rectal cancer outcomes. GO enrichment and KEGG analyses confirmed that differentially expressed genes (DEGs) were enriched in several glycolysis-related molecular functions or pathways based on glycolysis-related prognostic model of READ. Conclusions We found that a glycolysis-related prognostic model of COAD was not appropriate for READ, and we established a novel glycolysis-related two-gene risk model to effectively predict the prognosis of rectal cancer patients.

Gastric cancer (GC) exhibits significant heterogeneity and its prognosis remains dismal. Therefore, it is essential to investigate new approaches for diagnosing and treating GC. Desmosome proteins are crucial for the advancement and growth of cancer. Plakophilin-2 (PKP2), a member of the desmosome protein family, frequently exhibits aberrant expression and is strongly associated with many tumor types' progression. In this study, we found upregulation of PKP2 in GC. Further correlation analysis showed a notable association between increased PKP2 expression and both tumor stage and poor prognosis in individuals diagnosed with gastric adenocarcinoma. In addition, our research revealed that the Yes-associated protein1 (YAP1)/TEAD4 complex could stimulate the transcriptional expression of PKP2 in GC. Elevated PKP2 levels facilitate activation of the AKT/mammalian target of rapamycin signaling pathway, thereby promoting the malignant progression of GC. By constructing a mouse model, we ultimately validated the molecular mechanism and function of PKP2 in GC. Taken together, these discoveries suggest that PKP2, as a direct gene target of YAP/TEAD4 regulation, has the potential to be used as an indication of GC progression and prognosis. PKP2 is expected to be a promising therapeutic target for GC., (© 2024 Wiley Periodicals LLC.)

Yang Wu,1 Lu Liu,2 Xiaoyu Shen,1 Wenjing Liu,1 Rui Ma1 1Medical Oncology Department of Thoracic Cancer (2), Cancer Hospital of China Medical University, Liaoning Cancer Hospital & Institute, Shenyang 110042, Liaoning, People’s Republic of China; 2Institute of Cancer Stem Cell, Dalian Medical University, Dalian 116044, Liaoning, People’s Republic of ChinaCorrespondence: Rui MaMedical Oncology Department of Thoracic Cancer (2), Cancer Hospital of China Medical University, Liaoning Cancer Hospital & Institute, Shenyang 110042, Liaoning, People’s Republic of ChinaEmail marui2222@sina.comBackground: Lung cancer is one of the most aggressive tumors with high incidence and mortality, which could be classified into lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD). Overexpression of Plakophilin-2 (PKP2) has been reported in multiple malignancies. However, the expression and function mechanism of PKP2 in LUAD remain illusive.Methods: Real-time PCR (RT-PCR) was conducted to assess the expression of PKP2 in LUAD cells and tissues. An integrated analysis of PKP2 expression in The Cancer Genome Atlas (TCGA) was further performed. The effect of PKP2 on cell proliferation and invasion potential were then evaluated with loss-of-function assays in vitro. Xenograft nude mouse models were used to determine the role of PKP2 in LUAD tumorigenicity in vivo. Bioinformatics prediction, immunohistochemistry and Western blot were performed to examine whether PKP2 promoted LUAD development via enhancing focal adhesion and epithelial–mesenchymal transition.Results: PKP2 expression was highly expressed in LUAD tissues compared with that in normal tissues and predicated poor prognosis of LUAD patients. TCGA LUAD cohort analysis also showed that high expression of PKP2 indicated unfavorable outcomes in LUAD patients. PKP2 expression was also upregulated in lung cancer cells. Functionally, knockdown of PKP2 suppressed lung cancer cell proliferation and invasion in vitro, while inhibited xenograft lung tumor development in vivo. Mechanistically, we demonstrated that high expression of PKP2 in LUAD was correlated with enhanced EMT and focal adhesion. Knockdown of PKP2 inhibited the expression of EMT-related Vimentin and N-cadherin and focal adhesion-associated expression of BMP4, ICAM1, and VCAM1 in xenograft tumors and lung cancer cells.Conclusion: In summary, our findings indicate that PKP2 functions as an oncogene in LUAD, which could be utilized as a novel diagnostic and therapeutic marker for LUAD treatment.Keywords: PKP2, focal adhesion, EMT, lung adenocarcinoma

Background: Aerobic glycolysis is an emerging hallmark of cancer. Although some studies have constructed glycolysis-related prognostic models of colon adenocarcinoma (COAD) based on The Cancer Genome Atlas (TCGA) database, whether the COAD glycolysis-related prognostic model is appropriate for distinguishing the prognosis of rectal adenocarcinoma (READ) patients remains unknown. Exploring critical and specific glycolytic genes related to READ prognosis may help us discover new potential therapeutic targets for READ patients. Results: Three gene sets, HALLMARK_GLYCOLYSIS, REACTOME_GLYCOLYSIS and REACTOME_REGULATION_OF_GLYCOLYSIS_BY_FRUCTOSE_2_6_BISPHOSPHATE_METABOLISM, were both significantly enriched in both COAD and READ through glycolysis-related gene set enrichment analysis (GSEA). We found that six genes (ANKZF1, STC2, SUCLG2P2, P4HA1, GPC1 and PCK1) were independent prognostic genes in COAD, while TSTA3 and PKP2 were independent prognostic genes in READ. Glycolysis-related prognostic model of COAD and READ was, respectively, constructed and assessed in COAD and READ. We found that the glycolysis-related prognostic model of COAD was not appropriate for READ, while glycolysis-related prognostic model of READ was more appropriate for READ than for COAD. PCA and t-SNE analysis confirmed that READ patients in two groups (high and low risk score groups) were distributed in discrete directions based on the glycolysis-related prognostic model of READ. We found that this model was an independent prognostic indicator through multivariate Cox analysis, and it still showed robust effectiveness in different age, gender, M stage, and TNM stage. A nomogram combining the risk model of READ with clinicopathological characteristics was established to provide oncologists with a practical tool to evaluate the rectal cancer outcomes. GO enrichment and KEGG analyses confirmed that differentially expressed genes (DEGs) were enriched in several glycolysis-related molecular functions or pathways based on glycolysis-related prognostic model of READ. Conclusions: We found that a glycolysis-related prognostic model of COAD was not appropriate for READ, and we established a novel glycolysis-related two-gene risk model to effectively predict the prognosis of rectal cancer patients. [ABSTRACT FROM AUTHOR]

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is mainly caused by mutations in genes encoding desmosomal proteins. Variants in plakophilin-2 gene (PKP2) are the most common cause of the disease, associated with conventional ARVC phenotype. The study aims to evaluate the prevalence of PKP2 variants and examine genotype–phenotype correlation in Polish ARVC cohort. All 56 ARVC patients fulfilling the current criteria were screened for genetic variants in PKP2 using denaturing high-performance liquid chromatography or next-generation sequencing. The clinical evaluation involved medical history, electrocardiogram, echocardiography, and follow-up. Ten variants (5 frameshift, 2 nonsense, 2 splicing, and 1 missense) in PKP2 were found in 28 (50%) cases. All truncating variants are classified as pathogenic/likely pathogenic, while the missense variant is classified as variant of uncertain significance. Patients carrying a PKP2 mutation were younger at diagnosis (p = 0.003), more often had negative T waves in V1–V3 (p = 0.01), had higher left ventricular ejection fraction (p = 0.04), and were less likely to present symptoms of heart failure (p = 0.01) and left ventricular damage progression (p = 0.04). Combined endpoint of death or heart transplant was more frequent in subgroup without PKP2 mutation (p = 0.03). Pathogenic variants in PKP2 are responsible for 50% of ARVC cases in the Polish population and are associated with a better prognosis. ARVC patients with PKP2 mutation are less likely to present left ventricular involvement and heart failure symptoms. Combined endpoint of death or heart transplant was less frequent in this group. [ABSTRACT FROM AUTHOR]

Background and objectives: Plakophilin‐2 (PKP2) is an intracellular desmosomal anchoring protein that has been implicated in a genome‐wide association study, in which genetic variants of PKP2 are associated with Porphyromonas gingivalis (P.gingivalis) ‐dominant periodontal dysbiosis. In this study, we compared the ex vivo PKP2 expression in periodontitis gingival biopsies to periodontitis‐free subjects and assessed the in vitro role of PKP2 in gingival epithelial barrier function and the mechanism by which P.gingivalis modulates PKP2 expression. Material and methods: Using reverse transcription quantitative real‐time PCR (RT‐qPCR), we determined PKP2 mRNA expression levels in gingival biopsies collected from 11 periodontally healthy, 10 experimental gingivitis, and 10 chronic periodontitis subjects. PKP2 protein expression in gingival biopsies was detected by immunohistochemistry. We then challenged primary gingival epithelial cells with bacteria including P.gingivalis, Campylobacter rectus, and various Toll‐like receptor agonists. Western blot and immunofluorescence staining were used to detect protein expression. Inhibitors blocking proteases pathways were tested for P.gingivalis‐mediated PKP2 protein degradations. We also knocked down endogenous epithelial PKP2 using lentiviral short‐hairpin RNA (shRNA) and evaluated cell proliferation, spreading, and barrier function. Results: Periodontitis gingival biopsies had approximately twofold less PKP2 mRNA than did healthy controls (p <.05). PKP2 protein was predominantly expressed in gingival epithelium. In primary gingival epithelial cells, P.gingivalis challenge increased PKP2 mRNA levels, while protein expression decreased, which suggests that P.gingivalis has a protein degradation mechanism. Cysteine proteases inhibitors greatly attenuated P.gingivalis‐mediated PKP2 protein degradation. Epithelial cells with deficient PKP2 exhibited inhibited cell proliferation and spreading and failed to form monolayers. Finally, P.gingivalis impaired gingival epithelial barrier function. Conclusions: PKP2 appears to be critical in maintaining gingival epithelial barrier function and is susceptible to degradation by cysteine proteases produced by P.gingivalis. Our findings have identified a mechanism by which P.gingivalis impairs epithelial barrier function by promoting PKP2 degradation. [ABSTRACT FROM AUTHOR]

Left ventricular non-compaction (LVNC) is a rare and genetically heterogeneous cardiomyopathy. The disorder vastly affects infants and young children. Severe neonatal LVNC is relatively rare. The prevalence of genetic defects underlying pediatric and adult-onset LVNC is about 17–40%. Mutations of MYH7 and MYBPC3 sarcomeric genes are found in the vast majority of the positive pediatric cases. PKP2 encodes plakophilin-2, a non-sarcomeric desmosomal protein, which has multiple roles in cardiac myocytes including cell–cell adhesion, tightening gap junction, and transcriptional factor. Most of the reported PKP2 mutations are heterozygous missense and truncating variants, and they are associated with an adult-onset autosomal dominant disorder, namely arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). Homozygous PKP2 mutations have been rarely described. Herein, we present a rare case of an infant with neonatal onset of congestive heart failure owing to severe LVNC and multiple muscular VSD. Medical treatments failed to control the heart failure and the patient died at 11 months of age. Whole-exome sequencing identified a novel homozygous PKP2 variant, c.1511-1G>C, in the patient. An mRNA analysis revealed aberrant transcript lacking exon 7, which was predicted to cause a frameshift and truncated peptide (p.Gly460GlufsTer2). The heterozygous parents had normal cardiac structures and functions as demonstrated by electrocardiogram and echocardiography. Pathogenic variants of sarcomeric genes analyzed were not found in the patient. We conducted a literature review and identified eight families with biallelic PKP2 mutations. We observed that three families (our included) with null variants were linked to lethal phenotypes, while homozygous missense mutations resulted in less severe manifestations: adolescent-onset ARVD/C and childhood-onset DCM. Our data support a previous notion that severe neonatal LVNC might represent a unique entity and had distinct genetic spectrum. In conclusion, the present study has extended the phenotypes and genotypes of PKP2-related disorders and lethal LVNC.

OBJECTIVE: This project aims to elucidate the diagnostic and prognostic values of PPM1D in osteosarcoma and the molecular mechanism. PATIENTS AND METHODS: PPM1D levels in osteosarcoma and adjacent tissues were detected. Pathological information of included osteosarcoma patients was collected for analyzing the relationship between PPM1D and prognosis of osteosarcoma. Regulatory effects of PPM1D on in vivo and in vitro progressions of osteosarcoma were assessed by generating xenograft model in nude mice and PPM1D knockdown models in MG63 and U2OS cells, respectively. The involvement of PKP2, the target gene of PPM1D in osteosarcoma progression was finally evaluated. RESULTS: PPM1D was upregulated in osteosarcoma tissues than adjacent ones. High level of PPM1D indicated higher risks of distant metastasis and worse prognosis in osteosarcoma. In vivo knockdown of PPM1D contributed to a delay in tumor growth of osteosarcoma in nude mice. PKP2, as the downstream gene targeting PPM1D, was highly expressed in osteosarcoma tissues and positively correlated to PPM1D level. The overexpression of PKP2 was able to abolish the inhibited proliferative and migratory abilities in osteosarcoma cells with PPM1D knockdown. CONCLUSIONS: PPM1D triggers proliferative and migratory abilities of osteosarcoma by positively regulating PKP2, which can be served as an effective diagnostic marker for osteosarcoma in the early phase. [ABSTRACT FROM AUTHOR]

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is an inherited genetic disorder, characterized by the substitution of heart muscle with fibro-fatty tissue and severe ventricular arrhythmias, often leading to heart failure and sudden cardiac death. ACM is considered a monogenic disorder, but the low penetrance of mutations identified in patients suggests the involvement of additional genetic or environmental factors. Methods We used whole exome sequencing to investigate digenic inheritance in two ACM families where previous diagnostic tests have revealed a PKP2 mutation in all affected and some healthy individuals. In family members with PKP2 mutations we determined all genes that harbor variants in affected but not in healthy carriers or vice versa. We computationally prioritized the most likely candidates, focusing on known ACM genes and genes related to PKP2 through protein interactions, functional relationships, or shared biological processes. Results We identified four candidate genes in family 1, namely DAG1, DAB2IP, CTBP2 and TCF25, and eleven candidate genes in family 2. The most promising gene in the second family is TTN, a gene previously associated with ACM, in which the affected individual harbors two rare deleterious-predicted missense variants, one of which is located in the protein’s only serine kinase domain. Conclusions In this study we report genes that might act as digenic players in ACM pathogenesis, on the basis of co-segregation with PKP2 mutations. Validation in larger cohorts is still required to prove the utility of this model.

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that instigates several signaling cascades, including the NF-κB signaling pathway, to induce cell differentiation and proliferation. Overexpression and mutations of EGFR are found in up to 30% of solid tumors and correlate with a poor prognosis. Although it is known that EGFR-mediated NF-κB activation is involved in tumor development, the signaling axis is not well elucidated. Here, we found that plakophilin 2 (PKP2) and the linear ubiquitin chain assembly complex (LUBAC) were required for EGFR-mediated NF-κB activation. Upon EGF stimulation, EGFR recruited PKP2 to the plasma membrane, and PKP2 bridged HOIP, the catalytic E3 ubiquitin ligase in the LUBAC, to the EGFR complex. The recruitment activated the LUBAC complex and the linear ubiquitination of NEMO, leading to IκB phosphorylation and subsequent NF-κB activation. Furthermore, EGF-induced linear ubiquitination was critical for tumor cell proliferation and tumor development. Knockout of HOIP impaired EGF-induced NF-κB activity and reduced cell proliferation. HOIP knockout also abrogated the growth of A431 epidermal xenograft tumors in nude mice by more than 70%. More importantly, the HOIP inhibitor, HOIPIN-8, inhibited EGFR-mediated NF-κB activation and cell proliferation of A431, MCF-7, and MDA-MB-231 cancer cells. Overall, our study reveals a novel linear ubiquitination signaling axis of EGFR and that perturbation of HOIP E3 ubiquitin ligase activity is potential targeted cancer therapy.

Cell junctions play an important role in coordinating intercellular communication and intracellular ultrastructures, with desmosomes representing the mechanical component of such intercellular connections. Mutations to desmosomal component proteins compromise both inter- and intracellular signalling and correlate with severe diseases like arrhythmogenic cardiomyopathy (AC), with pathological phenotypes in tissues subjected to intense mechanical stimuli (skin and heart). Here, we explore the consequences of dysfunctional desmosomes in one line of induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) derived from an AC patient with a homozygous pathogenic mutation in desmosomal component protein plakophilin-2 (PKP2). We specifically aim at investigating the response to mechanical stress in an AC-pathological setting. To this aim, we aligned hiPS-CMs on stretchable patterned substrates to mimic the cardiac functional syncytium and compared transcriptomic profiles of PKP2-mutated hiPS-CMs and healthy controls. AC-CMs display altered transcription towards a pro-fibrotic gene expression program, and concurrent dysregulation of gene sets closely associated with cell-to-cell connections. By integrating the culture substrate with a macroscopic stretching setup able to accurately apply cyclic uniaxial elongation, we show how response to mechanical loads in AC-CMs deviates from the canonical mechanical-stress response observed in healthy-CMs. [ABSTRACT FROM AUTHOR]

Objective: The Latvian arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD-C) registry was established to determine the genetic background of ARVD-C for analyzing discovered genetic variation frequencies in the European and Latvian populations. Methods: In total, 38 patients with suspected ARVD-C were selected. The clinical parameters were defined according to the ARVD-C guidelines, PKP2 and DSG2 gene analysis was performed using the Sanger sequencing. Additionally, large deletions/duplications were analyzed using the multiplex ligation-dependent probe amplification (MLPA) analysis. Results: Twenty symptomatic patients were enrolled in the study. Typical ARVD abnormalities were found in electrocardiography for 10 (50%) patients, in Holter monitoring for 19 (95%), in transthoracic echocardiography for 20 (100%), and in cardiac magnetic resonance for 6 (30%). Different benign genetic variations were found. Three novel, unregistered, possibly benign variations were found in the PKP2 gene: c.2489+131G>A, c.2489+72delA, and c.1035-5T>C and three in the DSG2 gene: c.404G>A, c.1107G>A, and c.379-15A>G. Two genetic variations in the PKP2 gene: c.1592T>G, c.2489+1G>A are possibly pathogenic. For the first time, variation c.1592T>G, has been discovered in the homozygote form. Using the MLPA analysis, large deletions or duplications were not found. Conclusion: The prevalence of the majority of non-pathological genetic variations is similar in the Latvian ARVD-C patients and the European population. Possibly, pathogenic variations were found only in 10% of our registry patients, which could mean that PkP2 and DSG2 are not the most commonly affected genes in the Latvian population. [ABSTRACT FROM AUTHOR]

Background: Arrhythmogenic cardiomyopathy (ACM) is an inherited genetic disorder, characterized by the substitution of heart muscle with fibro-fatty tissue and severe ventricular arrhythmias, often leading to heart failure and sudden cardiac death. ACM is considered a monogenic disorder, but the low penetrance of mutations identified in patients suggests the involvement of additional genetic or environmental factors. Methods: We used whole exome sequencing to investigate digenic inheritance in two ACM families where previous diagnostic tests have revealed a PKP2 mutation in all affected and some healthy individuals. In family members with PKP2 mutations we determined all genes that harbor variants in affected but not in healthy carriers or vice versa. We computationally prioritized the most likely candidates, focusing on known ACM genes and genes related to PKP2 through protein interactions, functional relationships, or shared biological processes. Results: We identified four candidate genes in family 1, namely DAG1, DAB2IP, CTBP2 and TCF25 and eleven candidate genes in family 2. The most promising gene in the second family is TTN, a gene previously associated with ACM, in which the affected individual harbors two rare deleterious-predicted missense variants, one of which is located in the protein's only serine kinase domain. Conclusions: In this study we report genes that might act as digenic players in ACM pathogenesis, on the basis of co-segregation with PKP2 mutations. Validation in larger cohorts is still required to prove the utility of this model. [ABSTRACT FROM AUTHOR]

Glioma is the most common type of primary brain tumor in the CNS. Due to its poor prognosis and high mortality rates, it is urgent to find out more effective therapies. Plakophilin-2 (PKP2) is a widespread desmosomal plaque protein. Recently, the important roles of PKP2 in the proliferation and migration of cancer cells and tumor progression has been shown. However, the expression and potential function of PKP2 in glioma was still unclear. In this study, we demonstrated that PKP2 protein expression level was increased in glioma tissues compared with normal brain tissues, and its level was significantly associated with the Ki-67 expression and WHO grade by Western blot analysis and immunohistochemistry. Clinically, high PKP2 expression was tightly related to poor prognosis of glioma patients. Interestingly, we found that down-regulated PKP2 expression was shown to inhibit the migration of cells in glioma. Moreover, cell counting kit (CCK)-8 and colony formation analyses proved that reduced expression of PKP2 could weaken glioma cell proliferation. Taken together, these data uncover a potential role for PKP2 in the pathogenic process of glioma, suggesting that PKP2 may be a promising therapeutic target of glioma. [ABSTRACT FROM AUTHOR]

Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disease. While desmosomal gene mutations are considered major causes of ARVC, LMNA mutations have been reported to be possible causes of ARVC. In this study, we performed extensive genetic screening for LMNA mutations in our Japanese ARVC cohort to assess the prevalence and characteristics of LMNA mutation-positive ARVC cases. Methods Our study cohort consisted of 57 ARVC probands. Genetic analyses were performed by using direct sequencing and targeted sequencing of LMNA and four desmosomal genes. We compared clinical features of probands with desmosomal gene mutations to those of probands with LMNA mutations. Results Among 57 clinically diagnosed ARVC probands, we identified desmosomal gene mutations in 26 probands (45.6%) and two LMNA mutations in two probands. The first LMNA mutation p.M1K was detected in a 62-year-old male proband, while the second mutation p.W514X was found in a 70-year-old male proband. Compared to the 26 probands with desmosomal gene mutations, in the two probands with LMNA mutations, the mean age at diagnosis was significantly higher, and their heart rate at the diagnosis was significantly slower. While both probands with LMNA mutations underwent pacemaker implantation, only one proband with desmosomal mutations received this treatment (2/2 vs. 1/26). Conclusion Genetic screening for LMNA gene is important for ARVC patients, particularly in patients with bradycardia. [ABSTRACT FROM AUTHOR]

Background: Canine atopic dermatitis (CAD) is a chronic inflammatory skin disease triggered by allergic reactions involving IgE antibodies directed towards environmental allergens. We previously identified a ∼1.5 Mb locus on canine chromosome 27 associated with CAD in German shepherd dogs (GSDs). Fine-mapping indicated association closest to the PKP2 gene encoding plakophilin 2. Results: Additional genotyping and association analyses in GSDs combined with control dogs from five breeds with low-risk for CAD revealed the top SNP 27:19,086,778 (p = 1.4× 10-7) and a rare ∼48 kb risk haplotype overlapping the PKP2 gene and shared only with other high-risk CAD breeds. We selected altogether nine SNPs (four top-associated in GSDs and five within the ~48 kb risk haplotype) that spanned ~280 kb forming one risk haplotype carried by 35 % of the GSD cases and 10 % of the GSD controls (OR = 5.1, p = 5.9 × 10-5), and another haplotype present in 85 % of the GSD cases and 98 % of the GSD controls and conferring a protective effect against CAD in GSDs (OR = 0.14, p = 0.0032). Eight of these SNPs were analyzed for transcriptional regulation using reporter assays where all tested regions exerted regulatory effects on transcription in epithelial and/or immune cell lines, and seven SNPs showed allelic differences. The DNA fragment with the top-associated SNP 27:19,086,778 displayed the highest activity in keratinocytes with 11-fold induction of transcription by the risk allele versus 8-fold by the control allele (pdifference = 0.003), and also mapped close (∼3 kb) to an ENCODE skin-specific enhancer region. Conclusions: Our experiments indicate that multiple CAD-associated genetic variants located in cell type-specific enhancers are involved in gene regulation in different cells and tissues. No single causative variant alone, but rather multiple variants combined in a risk haplotype likely contribute to an altered expression of the PKP2 gene, and possibly nearby genes, in immune and epithelial cells, and predispose GSDs to CAD. [ABSTRACT FROM AUTHOR]

Background: Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is an inherited disease mainly found in young people causing malignant arrhythmias which can result in sudden cardiac death. Due to unspecific symptoms the diagnosis of ARVC is still challenging and requires clinical testing and expert knowledge. Genetic testing of index patients is helpful in the primary diagnosis and further testing of family members may allow for prevention of sudden cardiac death. Case presentation: We report a case of newly diagnosed ARVC where genetic testing identified a novel familial frame-shift mutation in the PKP2 gene. Screening of the family members identified both children and the father as mutation carriers following an autosomal-dominant inheritance pattern. Conclusion: Our findings emphasize the importance of genetic family screening after the identification of a causative mutation in an index case. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Common electrocardiographic patterns in Brugada Syndrome and Arrhythmogenic Cardiomyopathy have been reported despite phenotypic alterations during its clinical course. Recently, potentially pathogenic variants in the PKP2 gene, the most prevalent gene associated with Arrhythmogenic Cardiomyopathy, have been associated with Brugada Syndrome. In addition, in vitro studies demonstrated the interaction between plakophilin-2 and sodium channel, the most prevalent gene associated with Brugada Syndrome. All these facts reinforce the suggested overlapping between both entities but little is known about the pathophysiological mechanisms. We have performed a comprehensive genetic revision of all PKP2 genetic variants currently associated with Brugada Syndrome. In all variants we identified a lack of solid evidences in order to establish a definite genotype–phenotype association. Hence, despite we believe that PKP2 analysis should be considered as a part of molecular genetic testing in Brugada Syndrome patients, comprehensive clinical and molecular studies should be performed before establish pathogenic association. Therefore, PKP2 variants in Brugada Syndrome cases should be interpreted carefully and additional studies including family segregation should be performed before translation into clinical practice. [ABSTRACT FROM AUTHOR]

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that instigates several signaling cascades, including the NF-κB signaling pathway, to induce cell differentiation and proliferation. Overexpression and mutations of EGFR are found in up to 30% of solid tumors and correlate with a poor prognosis. Although it is known that EGFR-mediated NF-κB activation is involved in tumor development, the signaling axis is not well elucidated. Here, we found that plakophilin 2 (PKP2) and the linear ubiquitin chain assembly complex (LUBAC) were required for EGFR-mediated NF-κB activation. Upon EGF stimulation, EGFR recruited PKP2 to the plasma membrane, and PKP2 bridged HOIP, the catalytic E3 ubiquitin ligase in the LUBAC, to the EGFR complex. The recruitment activated the LUBAC complex and the linear ubiquitination of NEMO, leading to IκB phosphorylation and subsequent NF-κB activation. Furthermore, EGF-induced linear ubiquitination was critical for tumor cell proliferation and tumor development. Knockout of HOIP impaired EGF-induced NF-κB activity and reduced cell proliferation. HOIP knockout also abrogated the growth of A431 epidermal xenograft tumors in nude mice by more than 70%. More importantly, the HOIP inhibitor, HOIPIN-8, inhibited EGFR-mediated NF-κB activation and cell proliferation of A431, MCF-7, and MDA-MB-231 cancer cells. Overall, our study reveals a novel linear ubiquitination signaling axis of EGFR and that perturbation of HOIP E3 ubiquitin ligase activity is potential targeted cancer therapy. [ABSTRACT FROM AUTHOR]

Plakophilin-2 (PKP2) is the most frequently mutated desmosomal gene in arrhythmogenic cardiomyopathy (ACM), a disease characterized by structural and electrical alterations predominantly affecting the right ventricular myocardium. Notably, ACM cases without overt structural alterations are frequently reported, mainly in the early phases of the disease. Recently, the PKP2 p.S183N mutation was found in a patient affected by Brugada syndrome (BS), an inherited arrhythmic channelopathy most commonly caused by sodium channel gene mutations. We here describe a case of a patient carrier of the same BS-related PKP2 p.S183N mutation but with a clear diagnosis of ACM. Specifically, we report how clinical and molecular investigations can be integrated for diagnostic purposes, distinguishing between ACM and BS, which are increasingly recognized as syndromes with clinical and genetic overlaps. This observation is fundamentally relevant in redefining the role of genetics in the approach to the arrhythmic patient, progressing beyond the concept of "one mutation, one disease", and raising concerns about the most appropriate approach to patients affected by structural/electrical cardiomyopathy. The merging of genetics, electroanatomical mapping, and tissue and cell characterization summarized in our patient seems to be the most complete diagnostic algorithm, favoring a reliable diagnosis. [ABSTRACT FROM AUTHOR]

Background: Mutations in genes encoding intercalated disk/desmosome proteins, such as plakophilin 2 (PKP2), cause arrhythmogenic cardiomyopathy (ACM). Desmosomes are responsible for myocyte–myocyte attachment and maintaining mechanical integrity of the myocardium. Methods: We knocked down Pkp2 in HL-1 mouse atrial cardiomyocytes (HL-1Pkp2-shRNA) and characterized their biomechanical properties. Gene expression was analyzed by RNA-Sequencing, microarray, and qPCR. Immunofluorescence was used to detect changes in cytoskeleton and focal adhesion. Antagomirs were used to knock down expression of selected microRNA (miR) in the rescue experiments. Results: Knockdown of Pkp2 was associated with decreased cardiomyocyte stiffness and work of detachment, and increased plasticity index. Altered mechanical properties were associated with impaired actin cytoskeleton in HL-1Pkp2-shRNA cells. Analysis of differentially expressed genes identified focal adhesion and actin cytoskeleton amongst the most dysregulated pathways, and miR200 family (a, b, and 429) as the most upregulated miRs in HL-1Pkp2-shRNA cells. Knockdown of miR-200b but not miR-200a, miR-429, by sequence-specific shRNAs partially rescued integrin-α1 (Itga1) levels, actin organization, cell adhesion (on collagen), and stiffness. Conclusions: PKP2 deficiency alters cardiomyocytes adhesion through a mechanism that involves upregulation of miR-200b and suppression of Itga1 expression. These findings provide new insights into the molecular basis of altered mechanosensing in ACM. [ABSTRACT FROM AUTHOR]

• The first study to explore the expression and clinical significance of PKP2 in non-small cell lung cancer. • The clinical significance of PKP2 between lung adenocarcinoma and lung squamous carcinoma are different. • PKP2 expression is associated with EGFR signaling pathway in lung adenocarcinoma, but not in lung squamous carcinoma. Plakophilin 2 (PKP2), encodes a plakophilin protein that belongs to the member of desmosomal proteins. It has been reported that high expression of PKP2 is associated with several types of cancer in humans. However, the role of PKP2 in lung cancer remains obscure. PKP2 expression was investigated in non-small cell lung cancer (NSCLC) tissues and non-tumor tissues by performing immunohistochemistry on a tissue microarray and using The Cancer Genome Atlas (TCGA) database. Kaplan-Meier survival analysis and multivariate Cox-regression analysis were performed to identify the clinical significance of PKP2. 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), colony formation, Transwell and xenograft tumor growth/ metastasis assays were conducted to evaluate the biological function of PKP2 in vitro and in vivo. Gene set enrichment analysis (GSEA), WB and immunoprecipitation (IP) assay were utilized to explore the potential downstream signaling pathway and molecule mechanism of PKP2 in lung adenocarcinoma (LUAD). Analysis of PKP2 expression and clinicopathological parameters reveals a significant correlation of PKP2 expression with gender (n = 1020, P < 0.001) and histological type (n = 1020, P < 0.001). Subsequently, our results demonstrated that high PKP2 expression is not associated with poor survival in different gender of lung cancer patients, and is an unfavorable and independent prognostic biomarker for LUAD patients, but not for LUSC patients. Gene set enrichment analysis (GSEA) revealed that PKP2 expression is positively associated with EGFR signaling in LUAD. Further, in vitro and in vivo assays revealed that PKP2 promotes cell proliferation, migration and invasion through activating EGFR signaling pathway in LUAD cells. Our study provides the basis for further investigation of the function and molecular mechanism by which upregulation of PKP2 promotes the development and progression of LUAD. PKP2 may serve as a potential target for anticancer therapies. [ABSTRACT FROM AUTHOR]

CANAC1C encodes for the main cardiac L-type calcium channel and mutations on it lead to a prolonged QT interval in Timothy Syndrome (TS). We provide a new de novo constitutional heterozygote missense variation in CACNA1C in a living adult woman, also carrier of the known c.2146-1G>C heterozygous variation of PKP2 inherited from her father. To our knowledge, this patient is the first to have the two variations in these genes. Theses clinical and molecular findings expand the clinical and molecular spectrum of TS and show the interest of next generation sequencing or whole exome sequencing in rare disorders, atypical or novel phenotype. [ABSTRACT FROM AUTHOR]