A new diagnostic test for arrhythmogenic right ventricular cardiomyopathy

Role of genetic testing in arrhythmogenic right ventricular cardiomyopathy/dysplasia

In a cohort of patients with confirmed or suspected arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), genetic testing is useful in confirming the diagnosis, particularly in individuals who do not completely fulfil Task Force criteria for the disease, thereby also enabling the adoption of preventive measures in family members. Due to the high percentage of novel mutations that are expected to be identified in ARVC/D, the use of genetic screening technology based on the identification of known mutations seems to have very restricted value. Our results support that the presence of certain genetic variations could play a role in the final phenotype of patients with ARVC/D, where single and compound mutation carriers would have more symptomatic forms of the disease and the polymorphism P366L could be associated to a more benign phenotype.

The junctions that don't fit the scheme: special symmetrical cell-cell junctions of their own kind

Immunocytochemical, electron-, and immunoelectron-microscopical studies have revealed that, in addition to the four major "textbook categories" of cell-cell junctions (gap junctions, tight junctions, adherens junctions, and desmosomes), a broad range of other junctions exists, such as the tiny puncta adhaerentia minima, the taproot junctions (manubria adhaerentia), the plakophilin-2-containing adherens junctions of mesenchymal or mesenchymally derived cell types including malignantly transformed cells, the composite junctions (areae compositae) of the mature mammalian myocardium, the cortex adhaerens of the eye lens, the interdesmosomal "sandwich" or "stud" junctions in the subapical layers of stratified epithelia and the tumors derived therefrom, and the complexus adhaerentes of the endothelial and virgultar cells of the lymph node sinus. On the basis of their sizes and shapes, other morphological criteria, and their specific molecular ensembles, these junctions and the genes that encode them cannot be subsumed under one of the major categories mentioned above but represent special structures in their own right, appear to serve special functions, and can give rise to specific pathological disorders.

Cardiomyopathies: New test for arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is challenging to diagnose because of nonspecific findings, particularly in the early phases of the disease. Clinical diagnosis is made on the basis of several criteria, but these lack sensitivity. Asimaki et al. suggest that immunohistochemical analysis of myocardial desmosomal proteins is a highly sensitive and specific diagnostic test for ARVD/C.

Plakophilins: multifunctional scaffolds for adhesion and signaling

Armadillo family proteins known as plakophilins have been characterized as structural components of desmosomes that stabilize and strengthen adhesion by enhancing attachments with the intermediate filament cytoskeleton. However, plakophilins and their close relatives are emerging as versatile scaffolds for multiple signaling and metabolic processes that not only facilitate junction dynamics but also more globally regulate diverse cellular activities. While perturbation of plakophilin functions contribute to inherited diseases and cancer pathogenesis, the functional significance of the multiple PKP isoforms and the mechanisms by which their behaviors are regulated remain to be elucidated.

A case of mistaken identity of arrhythmogenic right ventricular dysplasia in a 75-year-old patient

We present an uncommon case of a 75-year-old woman who was admitted to our department for the evaluation of her double valvular disease that hid a diagnosis of arrhythmogenic right ventricular dysplasia (ARVD). In the course of preoperative workup, a mass of tissue substituting the right ventricular free wall was identified and documented with transthoracic echocardiography, computed tomography scanning, and nuclear magnetic resonance imaging. This pathology was not identified as ARVD. Before and after surgery (double valve replacement), malignant arrhythmias were observed and treated with an implantable cardioverter-defibrillator. The patient underwent reoperation 24 days later for endocarditis and died in the immediate postoperative period from untreatable ventricular arrhythmias. At autopsy the histological characteristics of ARVD were detected. This report highlights the difficulty in diagnosing ARVD in patients who do not fulfil the McKenna criteria.

Long-range silencing and position effects at telomeres and centromeres: parallels and differences

Most of the human genome is compacted into heterochromatin, a form that encompasses multiple forms of inactive chromatin structure. Transcriptional silencing mechanisms in budding and fission yeasts have provided genetically tractable models for understanding heritably repressed chromatin. These silent domains are typically found in regions of repetitive DNA, that is, either adjacent to centromeres or telomeres or within the tandemly repeated ribosomal DNA array. Here we address the mechanisms of centromeric, telomeric and locus-specific gene silencing, comparing simple and complex animals with yeast. Some aspects are universally shared, such as histone-tail modifications, while others are unique to either centromeres or telomeres. These may reflect roles for heterochromatin in other chromosomal functions, like kinetochore attachment and DNA ends protection.