Increased SK3 expression in DM1 lens cells leads to impaired growth through a greater calcium-induced fragility

Although cataract is a characteristic feature of myotonic dystrophy type 1 (DM1), little is known of the underlying mechanisms. We generated four lens epithelial cell lines derived from DM1 cataracts and two from age-matched, non-DM cataracts. Small-pool PCR revealed typical large triplet repeat expansions in the DM1 cells. Furthermore, real-time PCR analysis showed reduced SIX5 expression and increased expression of the Ca2+-activated K+ channel SK3 in the DM1 cells. These cells also exhibited longer population doubling times which did not arise through reduced proliferation, but rather increased cell death as shown by increased release of lactate dehydrogenase (LDH). Using 86Rb+ as a tracer for K+, we found no difference in the resting K+ influx or efflux kinetics. In all cases, the ouabain sensitive component of the influx contributed ~50% of the total. However, stimulating internal Ca2+ by exposure to ionomycin not only caused greater stimulation of K+ (86Rb) efflux in the DM1 cells but also induced a higher rate of cell death (LDH assay). Since both the hyper-stimulation of K+ efflux and cell death were reduced by the highly specific SK inhibitor apamin, we suggest that increased expression of SK3 has a critical role in the increased Ca2+-induced fragility in DM1 cells. The present data, therefore, both help explain the lower epithelial cell density previously observed in DM1 cataracts and provide general insights into mechanisms underlying the fragility of other DM1-affected tissues

Pentamidine rescues contractility and rhythmicity in a Drosophila model of myotonic dystrophy heart dysfunction

Up to 80% of individuals with myotonic dystrophy type 1 (DM1) will develop cardiac abnormalities at some point during the progression of their disease, the most common of which is heart blockage of varying degrees. Such blockage is characterized by conduction defects and supraventricular and ventricular tachycardia, and carries a high risk of sudden cardiac death. Despite its importance, very few animal model studies have focused on the heart dysfunction in DM1. Here, we describe the characterization of the heart phenotype in a Drosophila model expressing pure expanded CUG repeats under the control of the cardiomyocyte-specific driver GMH5-Gal4. Morphologically, expression of 250 CUG repeats caused abnormalities in the parallel alignment of the spiral myofibrils in dissected fly hearts, as revealed by phalloidin staining. Moreover, combined immunofluorescence and in situ hybridization of Muscleblind and CUG repeats, respectively, confirmed detectable ribonuclear foci and Muscleblind sequestration, characteristic features of DM1, exclusively in flies expressing the expanded CTG repeats. Similarly to what has been reported in humans with DM1, heart-specific expression of toxic RNA resulted in reduced survival, increased arrhythmia, altered diastolic and systolic function, reduced heart tube diameters and reduced contractility in the model flies. As a proof of concept that the fly heart model can be used for in vivo testing of promising therapeutic compounds, we fed flies with pentamidine, a compound previously described to improve DM1 phenotypes. Pentamidine not only released Muscleblind from the CUG RNA repeats and reduced ribonuclear formation in the Drosophila heart, but also rescued heart arrhythmicity and contractility, and improved fly survival in animals expressing 250 CUG repeats

Disseminated Blastomycosis Presenting with Spontaneous Coronary Artery Dissection

Spontaneous coronary artery dissection (SCAD) is increasingly recognized as an important cause of acute coronary syndrome (ACS) and myocardial infarction (MI) in individuals with few or no known atherosclerotic risk factors. While systemic autoimmune inflammatory disorders are associated with precipitating SCAD, the role of infection-induced systemic inflammation in SCAD is not well defined. We present the case of a 49-year-old Caucasian woman with ST-elevation myocardial infarction (STEMI) diagnosed as SCAD from a severe systemic inflammatory response related to disseminated blastomycosis. Punch biopsy of a skin lesion and synovial fluid culture confirmed Blastomyces dermatitidis. This case suggests the possibility of systemic infection-induced inflammation as a precipitating factor in SCAD pathogenesis similar to autoimmune inflammatory disorders

Transgenic overexpression of human DMPK accumulates into hypertrophic cardiomyopathy, myotonic myopathy and hypotension traits of myotonic dystrophy.

Contains fulltext : 59209.pdf (publisher's version ) (Closed access)Abnormal expression of human myotonic dystrophy protein kinase (hDMPK) gene products has been implicated in myotonic dystrophy type 1 (DM1), yet the impact of distress accumulation produced by persistent overexpression of this poorly understood member of the Rho kinase-related protein kinase gene-family remains unknown. Here, in the aged transgenic murine line carrying approximately 25 extra copies of a complete hDMPK gene with all exons and an intact promoter region (Tg26-hDMPK), overexpression of mRNA and protein transgene products in cardiac, skeletal and smooth muscles resulted in deficient exercise endurance, an integrative index of muscle systems underperformance. In contrast to age-matched (11-15 months) wild-type controls, hearts from Tg26-hDMPK developed cardiomyopathic remodeling with myocardial hypertrophy, myocyte disarray and interstitial fibrosis. Hypertrophic cardiomyopathy was associated with a propensity for dysrhythmia and characterized by overt intracellular calcium overload promoting nuclear translocation of transcription factors responsible for maladaptive gene reprogramming. Skeletal muscles in distal limbs of Tg26-hDMPK showed myopathy with myotonic discharges coupled with deficit in sarcolemmal chloride channels, required regulators of hyperexcitability. Fiber degeneration in Tg26-hDMPK resulted in sarcomeric disorganization, centralization of nuclei and tubular aggregation. Moreover, the reduced blood pressure in Tg26-hDMPK indicated deficient arterial smooth muscle tone. Thus, the cumulative stress induced by permanent overexpression of hDMPK gene products translates into an increased risk for workload intolerance, hypertrophic cardiomyopathy with dysrhythmia, myotonic myopathy and hypotension, all distinctive muscle traits of DM1. Proper expression of hDMPK is, therefore, mandatory in supporting the integral balance among cytoarchitectural infrastructure, ion-homeostasis and viability control in various muscle cell types

ABCD‐GENE Score and Clinical Outcomes Following Percutaneous Coronary Intervention: Insights from the TAILOR‐PCI Trial

Background In TAILOR‐PCI, genotype‐guided selection of P2Y12 inhibitors after percutaneous coronary intervention did not significantly reduce the risk of ischemic events at 12 months. The Age, Body Mass Index, Chronic Kidney Disease, Diabetes, and Genotyping (ABCD‐GENE) score identifies patients with high platelet reactivity on clopidogrel at increased risk of ischemic events. The aim of this study was to investigate the value of the ABCD‐GENE score for tailoring P2Y12 inhibitor selection after percutaneous coronary intervention. Methods and Results In a post hoc analysis of the TAILOR‐PCI, outcomes were analyzed by ABCD‐GENE score and allocation to genotype‐guided or conventional P2Y12 inhibitor selection. Primary (death, myocardial infarction, or stroke) and secondary (cardiovascular death, myocardial infarction, stroke, stent thrombosis, or severe recurrent ischemia) outcomes were assessed. Among 3883 patients discharged on clopidogrel in the genotype‐guided and conventional therapy groups, 15.8% and 84.2% had high (≥10 points) or low (<10) ABCD‐GENE scores, respectively. At 12 months, both the primary (5.2% versus 2.6%, P<0.001) and secondary outcomes (7.7% versus 4.6%, P=0.001) were significantly increased in patients with high ABCD‐GENE score. Among 4714 patients allocated to genotype‐guided or conventional therapy, the former did not significantly reduce the 12‐month risk of the primary and secondary outcomes in both the high and low ABCD‐GENE score groups (pinteraction=0.48 and 0.27, respectively). Conclusions Among patients with percutaneous coronary intervention on clopidogrel, the ABCD‐GENE score was helpful in identifying those at higher risk. The ABCD‐GENE score may potentially enhance the precision of tailored selection of P2Y12 inhibitors, which needs to be confirmed in prospective investigations. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01742117

DMPK protein isoforms are differentially expressed in myogenic and neural cell lineages.

Contains fulltext : 79892.pdf (publisher's version ) (Closed access)Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by an unstable (CTG . CAG)n segment in the 3' untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. It is commonly accepted that DMPK mRNA-based toxicity is the main contributor to DM1 manifestations; however, not much is known about the significance of the DMPK protein. To appreciate its normal and possible pathobiological role, we analyzed the patterns of DMPK splice isoform expression in mouse tissues. Long membrane-anchored DMPK dominated in heart, diaphragm, and skeletal muscle, whereas short cytosolic isoforms were highly expressed in bladder and stomach. Both isoform types were present in diverse brain regions. DMPK protein was also detectable in cultured myoblasts, myotubes, cortical astrocytes, and related cell lines of neural or muscle origin, but not in hippocampal neurons. This work identifies DMPK as a kinase with pronounced expression in diverse muscle and neural tissues that are affected in DM1