Development and regeneration dynamics of the Medaka notochord.

The notochord is an embryonic tissue that acts as a hydrostatic skeleton until ossification begins in vertebrates. It is composed of outer sheath cells and inner vacuolated cells, which are generated from a common pool of disc-shaped precursors. Notochord extension during early embryogenesis is driven by the growth of vacuolated cells, reflecting in turn the expansion of their inner vacuole. Here we use desmogon, a novel desmosomal cadherin, to follow notochord development and regeneration in medaka (Oryzias latipes). We trace desmogon â€‹+ disc-shaped precursors at the single cell level to demonstrate that they operate as unipotent progenitors, giving rise to either sheath or vacuolated cells. We reveal that once specified, vacuolated cells grow asynchronously and drive notochord expansion bi-directionally. Additionally, we uncover distinct regenerative responses in the notochord, which depend on the nature of the injury sustained. By generating a desmogon CRISPR mutant we demonstrate that this cadherin is essential for proper vacuolated cell shape and therefore correct notochord and spine morphology. Our work expands the repertoire of model systems to study dynamic aspects of the notochord in vivo, and provides new insights in its development and regeneration properties.

Integrative prognostic subtype discovery in high-grade serous ovarian cancer.

OBJECTIVE: We sought to identify novel molecular subtypes of high-grade serous ovarian cancer (HGSC) by the integration of gene expression and proteomics data and to find the underlying biological characteristics of ovarian cancer to improve the clinical outcome. METHODS: The iCluster method was utilized to analysis 131 common HGSC samples between TCGA and Clinical Proteomic Tumor Analysis Consortium databases. Kaplan-Meier survival curves were used to estimate the overall survival of patients, and the differences in survival curves were assessed using the log-rank test. RESULTS: Two novel ovarian cancer subtypes with different overall survival (P = .00114) and different platinum status (P = .0061) were identified. Eighteen messenger RNAs and 38 proteins were selected as differential molecules between subtypes. Pathway analysis demonstrated arrhythmogenic right ventricular cardiomyopathy pathway played a critical role in the discrimination of these two subtypes and desmosomal cadherin DSG2, DSP, JUP, and PKP2 in this pathway were overexpression in subtype I compared with subtype II. CONCLUSION: Our study extended the underlying prognosis-related biological characteristics of high-grade serous ovarian cancer. Enrichment of desmosomal cadherin increased the risk for HGSC prognosis among platinum-sensitive patients, the results guided the revision of the treatment options for platinum-sensitive ovarian cancer patients to improve outcomes.

Clinical and molecular implications of structural changes to desmosomes and corneodesmosomes.

Desmosomes provide the main intercellular adhesive properties between epidermal keratinocytes. Their distribution becomes uneven in severe dermatitis, multiple allergies and metabolic wasting syndrome due to desmoglein 1 deficiency and the loss of intercellular adhesion or acantholysis. When keratinocytes differentiate from granular cells into cornified cells, desmosomes are transformed into corneodesmosomes and can provide stronger intercellular adhesion. Degradation of corneodesmosomes is a tightly regulated process involving a number of proteases and their inhibitors. Peripheral corneodesmosomes are protected from proteolytic degradation by the tight junction-related structures around them, and this construction provides the basis for the normal basket weave-like structure of the stratum corneum. In Netherton syndrome, which is caused by an absence of the protease inhibitor lymphoepithelial Kazal-type-related inhibitor, premature degradation of corneodesmosomes occurs due to the overactivation of proteases involved in corneodesmosome degradation. Inflammatory peeling skin disease is caused by the absence of corneodesmosin, a unique component of corneodesmosomes. In this disease, corneodesmosomes are structurally abnormal, and their adhesiveness is compromised, which leads to intercellular splitting between the stratum corneum and stratum granulosum. The better we understand desmosome and corneodesmosome ultrastructure in normal and diseased skin, the clearer the physiological and pathological mechanisms of epidermal integrity become.

Combination of palmoplantar keratoderma and hair shaft anomalies, the warning signal of severe arrhythmogenic cardiomyopathy: a systematic review on genetic desmosomal diseases.

Inherited desmosomal diseases are characterised by skin and/or cardiac features. Dermatological features might be a clue in the determination of the underlying life-threatening cardiac disease. This article aims to propose a dermatological algorithm for the diagnosis of desmosomal diseases after a systematic review of published articles. Palmoplantar keratoderma (PPK), hair shaft anomalies and skin fragility are the major features in the 458 patients analysed. Isolated PPK or isolated hair shaft anomalies are associated with a desmosomal disease limited to skin. The combination of PPK and hair shaft anomalies was recorded in 161 patients, and this association is at high risk of cardiac disease (129/161, 80.1%). Skin features had led to cardiac monitoring in only 2.3% of those patients. We delineated three major phenotypes: the PPK-hair shaft anomalies-non-fragile skin subtype (77%), always associated with cardiac involvement; the PPK-hair shaft anomalies-skin fragility-normal cardiac function subtype (19.9%), frequently associated with PKP1 mutations; the PPK-hair shaft anomalies-skin fragility-cardiac involvement subtype (3.1%), always due to DSP mutations. Three mutation hotspots in DSP and JUP account for 90.8% of the patients with cardiac involvement. The combination of PPK and hair shaft anomalies justifies long-term cardiac monitoring.

Defining the nasal transcriptome in granulomatosis with polyangiitis (Wegener's).

OBJECTIVE: To determine whether disease processes related to granulomatosis with polyangiitis (Wegener's) (GPA) are reflected in gene expression profiles of the nasal mucosa. METHODS: Nasal brushings of the inferior turbinate were obtained from 32 patients with GPA (10 with active nasal disease, 13 with prior nasal disease, and 9 with no history of nasal disease) and a composite comparator group with and without inflammatory nasal disease (12 healthy people, 15 with sarcoidosis, and 8 with allergic rhinitis). Differential gene expression was assessed between subgroups of GPA and comparators. RESULTS: A total of 339 genes were differentially expressed between the GPA and comparator groups (absolute fold change >1.5; false discovery rate <0.05). Top canonical pathways up-regulated in nasal brushings from patients with GPA included granulocyte adhesion and diapedesis (P = 8.6(-22) ), agranulocyte adhesion and diapedesis (P = 1.3(-14) ), IL10 signaling (P = 3.0(-11) ), LXR/RXR activation (P = 4.3(-11) ), and TREM1 signaling (P = 9.0(-11) ). A set of genes differentially expressed in GPA independently of nasal disease activity status included genes related to epithelial barrier integrity (fibronectin 1, desmosomal proteins) and several matricellular proteins (e.g., osteonectin, osteopontin). Significant overlap of differentially expressed genes was observed between active and prior nasal disease GPA subgroups. Peripheral blood neutrophil and mononuclear gene expression levels associated with GPA were similarly altered in the nasal gene expression profiles of patients with active or prior nasal disease. CONCLUSION: Profiling the nasal transcriptome in GPA reveals gene expression signatures related to innate immunity, inflammatory cell chemotaxis, extracellular matrix composition, and epithelial barrier integrity. Thus, airway-based expression profiling is feasible and informative in GPA.

Expression of desmosomal proteins in acantholytic squamous cell carcinoma of the skin.

Acantholytic (adenoid) squamous cell carcinoma (ASCC) is a subtype of squamous cell carcinoma (SCC) in which neoplastic tumour cells form gland-like structures. Little is known about the pathogenetic mechanisms of ASCC. We hypothesised that they may be related to the compositon of desmosomes. We analysed the immunohistochemical expression of desmosomal proteins in 5 cases of ASCC of the skin, in comparison to 5 cases of conventional SCC of the skin. The most consistent findings were loss of desmoglein 1 (DSG 1), desmoglein 3 (DSG3), desmocollin 1 (DSC1), desmocollin 2 (DSC2), desmocollin 3 (DSC 3), and plakophilin 1 (PKP 1), and decreased expression of desmoplakin 1 (DP 1) and plakoglobin (PG). In conventional well to moderately differentiated SCC, the expression of desmosomal proteins was decreased, but membranous staining was mostly preserved with patterns similar to normal epidermis. Our results suggest that loss of desmosomal cadherins and decreased expression of desmosomal plaque proteins might be responsible for the formation of gland-like structures in ASCC. It seems that desmosomal cadherins, which correspond to the transmembrane core of desmosomes, are predominantly affected in ASCC, while DP 1 and PG, which correspond to cytoplasmic plaque of desmosomes, probably play a lesser role in maintenance of tumour cell cohesion. Our results also indicate that, in addition to previously described verrucous and spindle cell carcinoma, ASCC is another subtype of SCC with a characteristic expression pattern of desmosomal proteins.

IgG autoantibody response against keratinocyte cadherins in endemic pemphigus foliaceus (fogo selvagem).

It is well established that autoantibodies against desmoglein 3 and desmoglein 1 (Dsg1) are relevant in the pathogenesis of pemphigus vulgaris and pemphigus foliaceus, including its endemic form fogo selvagem (FS). Isolated reports have shown that in certain patients with these diseases, autoantibodies against other desmosomal cadherins and E-cadherin may also be present. The goal of this investigation was to determine whether FS patients and normal individuals living in endemic areas possess autoantibodies against other desmosomal cadherins and E-cadherin. By testing a large number of FS and endemic control sera by ELISA, we found a consistent and specific autoantibody response against Dsg1 and other keratinocyte cadherins in these individuals, which is quite different from healthy individuals from the United States (US controls). Overall, the highest correlations among the autoantibody responses tested were in the endemic controls, followed by FS patients, and lowest in the US controls. These findings suggest that multiple, perhaps cross-reactive, keratinocyte cadherins are recognized by FS patients and endemic controls.

Desmosomal protein gene mutations in patients with idiopathic dilated cardiomyopathy undergoing cardiac transplantation: a clinicopathological study.

BACKGROUND: Idiopathic dilated cardiomyopathy (DCM) is the most frequent indication for orthotopic heart transplantation. It has been suggested that mutations in genes encoding desmosomal proteins, more typically associated with arrhythmogenic right ventricular cardiomyopathy, are a cause of DCM. OBJECTIVES: To determine the frequency of desmosomal protein gene mutations in heart transplant recipients and their families and to examine histopathological characteristics of explanted organs from mutation carriers. METHODS: 89 unrelated patients aged 47.9±13.5 years (80% male) transplanted for end-stage DCM underwent genetic screening of five desmosomal genes (PKP2, DSP, DSC2, DSG2 and JUP). The findings were correlated with clinical features and histological characteristics in explanted hearts. RESULTS: Pathogenic mutations were identified in 12 patients (13%). Five additional patients (6%) had genetic variants of unknown significance. The clinical phenotype of patients with pathogenic mutations was indistinguishable from that observed in patients without mutations. Evaluation of 76 relatives from 14 families with sequence variants (11 with pathogenic mutations and three with variants of unknown effect) identified 38 mutation carriers, four of whom had an overt DCM phenotype. Evidence of co-segregation of mutations with DCM phenotype was found in five families. Histological evaluation of explanted hearts did not show any specific features in patients with pathogenic mutations. CONCLUSIONS: Mutations in desmosomal genes are frequent in patients with advanced DCM undergoing cardiac transplantation. These findings emphasise the importance of familial evaluation and genetic counselling in patients with end-stage DCM and pose important challenges for current histopathological criteria for arrhythmogenic right ventricular cardiomyopathy.

Membrane-impermeable cross-linking provides evidence for homophilic, isoform-specific binding of desmosomal cadherins in epithelial cells.

Desmosomes and adherens junctions are cadherin-based protein complexes responsible for cell-cell adhesion of epithelial cells. Type 1 cadherins of adherens junctions show specific homophilic adhesion that plays a major role in developmental tissue segregation. The desmosomal cadherins, desmocollin and desmoglein, occur as several different isoforms with overlapping expression in some tissues where different isoforms are located in the same desmosomes. Although adhesive binding of desmosomal cadherins has been investigated in a variety of ways, their interaction in desmosome-forming epithelial cells has not been studied. Here, using extracellular homobifunctional cross-linking, we provide evidence for homophilic and isoform-specific binding between the Dsc2, Dsc3, Dsg2, and Dsg3 isoforms in HaCaT keratinocytes and show that it represents trans interaction. Furthermore, the cross-linked adducts are present in the detergent-insoluble fraction, and electron microscopy shows that extracellular cross-linking probably occurs in desmosomes. We found no evidence for either heterophilic or cis interaction, but neither can be completely excluded by our data. Mutation of amino acid residues Trp-2 and Ala-80 that are important for trans interaction in classical cadherin adhesive binding abolished Dsc2 binding, indicating that these residues are also involved in desmosomal adhesion. These interactions of desmosomal cadherins may be of key importance for their ordered arrangement within desmosomes that we believe is essential for desmosomal adhesive strength and the maintenance of tissue integrity.

Plakoglobin rescues adhesive defects induced by ectodomain truncation of the desmosomal cadherin desmoglein 1: implications for exfoliative toxin-mediated skin blistering.

Desmoglein 1 (Dsg1) is a desmosomal cadherin that is essential to epidermal integrity. In the blistering diseases bullous impetigo and staphylococcal scalded-skin syndrome, pathogenesis depends on cleavage of Dsg1 by a bacterial protease, exfoliative toxin A, which removes residues 1 to 381 of the Dsg1 ectodomain. However, the cellular responses to Dsg1 cleavage that precipitate keratinocyte separation to induce blister formation are unknown. Here, we show that ectodomain-deleted Dsg1 (Δ381-Dsg1) mimics the toxin-cleaved cadherin, disrupts desmosomes, and reduces the mechanical integrity of keratinocyte sheets. In addition, we demonstrate that truncated Dsg1 remains associated with its catenin partner, plakoglobin, and causes a reduction in the levels of endogenous desmosomal cadherins in a dose-dependent manner, leading us to hypothesize that plakoglobin sequestration by truncated Dsg1 destabilizes other cadherins. Accordingly, a triple-point mutant of the ectodomain-deleted cadherin, which is uncoupled from plakoglobin, does not impair adhesion, indicating that this interaction is essential to the pathogenic potential of truncated Dsg1. Moreover, we demonstrate that increasing plakoglobin levels rescues cadherin expression, desmosome organization, and functional adhesion in cells expressing Δ381-Dsg1 or treated with exfoliative toxin A. Finally, we report that histone deacetylase inhibition up-regulates desmosomal cadherins and prevents the loss of adhesion induced by Dsg1 truncation. These findings further our understanding of the mechanism of exfoliative toxin-induced pathology and suggest novel strategies to suppress blistering in bulbous impetigo and staphylococcal scalded-skin syndrome.

Prevalence of desmosomal protein gene mutations in patients with dilated cardiomyopathy.

BACKGROUND: Idiopathic dilated cardiomyopathy is a familial disorder in 25% to 50% of patients, but the genetic basis in the majority of cases remains unknown. Genes encoding desmosomal proteins, currently regarded as synonymous with another disorder, arrhythmogenic right ventricular cardiomyopathy, are known to cause left ventricular dysfunction, but their importance in unselected patients with unequivocal dilated cardiomyopathy is unknown. The objective of this study was to determine the prevalence of mutations in 5 desmosomal protein genes in patients with dilated cardiomyopathy. METHODS AND RESULTS: We studied 100 unrelated patients with idiopathic dilated cardiomyopathy consecutively referred to a dedicated cardiomyopathy unit. Patients underwent clinical evaluation, ECG, echocardiography, exercise testing, 24-hour ambulatory ECG monitoring, and mutation screening of 5 genes implicated in arrhythmogenic right ventricular cardiomyopathy: plakoglobin, desmoplakin, plakophilin-2, desmoglein-2, and desmocollin-2. Of the 100 patients (mean age at evaluation, 46.8+/-13.8 years; range, 17.0 to 72.8 years; male sex, 63%), 5 were found to carry pathogenic desmosomal protein gene mutations. An additional 13 patients had sequence variants of uncertain pathogenic significance and were excluded from further comparative analysis. Patients harboring desmosomal gene mutations had a phenotype indistinguishable from the 82 noncarriers, with the exception of exercise-induced ventricular ectopy, which was more frequent in the desmosomal mutation carriers (P=0.033). None of the 5 carriers of desmosomal mutations fulfilled current diagnostic criteria for arrhythmogenic right ventricular cardiomyopathy, but 1 had fibrofatty change in the left ventricle at autopsy. CONCLUSIONS: Heart failure caused by a dilated, poorly contracting left ventricle and arrhythmogenic right ventricular cardiomyopathy have been considered distinct clinicopathologic entities. This study suggests that both clinical presentations can be caused by mutations in desmosomal protein genes.

Perturbed desmosomal cadherin expression in grainy head-like 1-null mice.

In Drosophila, the grainy head (grh) gene plays a range of key developmental roles through the regulation of members of the cadherin gene family. We now report that mice lacking the grh homologue grainy head-like 1 (Grhl1) exhibit hair and skin phenotypes consistent with a reduction in expression of the genes encoding the desmosomal cadherin, desmoglein 1 (Dsg1). Grhl1-null mice show an initial delay in coat growth, and older mice exhibit hair loss as a result of poor anchoring of the hair shaft in the follicle. The mice also develop palmoplantar keratoderma, analogous to humans with DSG1 mutations. Sequence analysis, DNA binding, and chromatin immunoprecipitation experiments demonstrate that the human and mouse Dsg1 promoters are direct targets of GRHL1. Ultrastructural analysis reveals reduced numbers of abnormal desmosomes in the interfollicular epidermis. These findings establish GRHL1 as an important regulator of the Dsg1 genes in the context of hair anchorage and epidermal differentiation, and suggest that cadherin family genes are key targets of the grainy head-like genes across 700 million years of evolution.

Discriminating roles of desmosomal cadherins: beyond desmosomal adhesion.

The desmosomal cadherins, which include desmogleins and desmocollins, are Ca(2+)-dependent adhesion molecules that cooperate to make up the adhesive core of intercellular junctions known as desmosomes. The roles of desmosomal cadherins in epidermal integrity and as targets in human cutaneous disease have been well established. However, the molecular basis of these disorders is still poorly understood, due in part to a lack of fundamental knowledge about the organization of the adhesive interface and molecular machinery that dictates the proper presentation of desmogleins and desmocollins on the cell surface. Further, the diversity of the desmosomal cadherin family, and their individualized expression patterns within complex tissues, suggests that these adhesion molecules may have differentiation-specific functions that transcend their roles in intercellular adhesion. Here we will review the most recent data from our own group and others that are beginning to unveil the diverse properties and functions of this complex family of adhesion molecules.

Desmoglein 4 mutations underlie localized autosomal recessive hypotrichosis in humans, mice, and rats.

A newly defined form of inherited hair loss, named localized autosomal recessive hypotrichosis (LAH, OMIM 607903), was recently described in the literature and shown to be linked to chromosome 18. A large, intragenic deletion in the desmoglein 4 gene (DSG4) as the underlying mutation in several unrelated families of Pakistani origin. LAH is an autosomal recessive form of hypotrichosis affecting the scalp, trunk, and extremities, and largely sparing the facial, pubic, and axillary hair. Typical hairs are fragile and break easily, leaving short sparse scalp hairs with a characteristic appearance. Using comparative genomics, we also demonstrated that human LAH is allelic with the lanceolate hair (lah) mouse, as well as the lanceolate hair (lah) rat phenotype. Together, these models provide new information about the role of desmosomal cadherins in disease, and serve as in vivo models for functional and mechanistic studies into the role of desmoglein 4 in the skin and hair follicle.

Impaired formation of desmosomal junctions in ADPKD epithelia.

Mutations in polycystin-1 (PC-1) are responsible for autosomal dominant polycystic kidney disease (ADPKD), characterized by formation of fluid-filled tubular cysts. The PC-1 is a multifunctional protein essential for tubular differentiation and maturation found in desmosomal junctions of epithelial cells where its primary function is to mediate cell-cell adhesion. To address the impact of mutated PC-1 on intercellular adhesion, we have analyzed the structure/function of desmosomal junctions in primary cells derived from ADPKD cysts. Primary epithelial cells from normal kidney showed co-localization of PC-1 and desmosomal proteins at cell-cell contacts. A striking difference was seen in ADPKD cells, where PC-1 and desmosomal proteins were lost from the intercellular junction membrane, despite unchanged protein expression levels. Instead, punctate intracellular expression for PC-1 and desmosomal proteins was detected. The N-cadherin, but not E-cadherin was expressed in adherens junctions of ADPKD cells. These data together with co-sedimentation analysis demonstrate that, in the absence of functional PC-1, desmosomal junctions cannot be properly assembled and remain sequestered in cytoplasmic compartments. Taken together, our results demonstrate that PC-1 is crucial for formation of intercellular contacts. We propose that abnormal expression of PC-1 causes disregulation of cellular adhesion complexes leading to increased proliferation, loss of polarity and, ultimately, cystogenesis.