Mutations in RBM20 encoding the RNA-binding motif protein 20 (RBM20) are associated with an early onset and clinically severe forms of cardiomyopathies. Transcriptome analyses revealed RBM20 as an important regulator of cardiac alternative splicing. RBM20 mutations are especially localized in exons 9 and 11 including the highly conserved arginine and serine-rich domain (RS domain). Here, we investigated in several cardiomyopathy patients, the previously described RBM20-mutation p.Pro638Leu localized within the RS domain. In addition, we identified in a patient the novel mutation p.Val914Ala localized in the (glutamaterich) Glu-rich domain of RBM20 encoded by exon 11. Its impact on the disease was investigated with a novel TTN-and RYR2-splicing assay based on the patients' cardiac messenger RNA. Furthermore, we showed in cell culture and in human cardiac tissue that mutant RBM20-p.Pro638Leu is not localized in the nuclei but causes an abnormal cytoplasmic localization of the protein. In contrast the splicing deficient RBM20-p.Val914Ala has no influence on the intracellular localization. These results indicate that disease-associated variants in RBM20 lead to aberrant splicing through different pathomechanisms dependent on the localization of the mutation. This might have an impact on the future development of therapeutic strategies for the treatment of RBM20-induced cardiomyopathies.

Aims Timely referrals for transplantation and left ventricular assist device (LVAD) play a key role in favourable outcomes in patients with advanced heart failure (HF). The purpose of the Catheter Ablation for atrial fibrillation in patientS with end-sTage heart faiLure and Eligibility for Heart Transplantation (CASTLE-HTx) trial is to test the hypothesis that atrial fibrillation (AF) ablation has beneficial effects on mortality and morbidity during 'waiting time' for heart transplantation (HTx) or to prolong the time span until LVAD implantation. Methods and Results CASTLE-HTx is a randomized evaluation of ablative treatment of AF in patients with severe left ventricular dysfunction who are candidates and eligible for HTx. The primary endpoint is the composite of all-cause mortality, worsening of HF requiring a high urgent transplantation, or LVAD implantation. The secondary study endpoints are all-cause mortality, cardiovascular mortality, cerebrovascular accidents, worsening of HF requiring unplanned hospitalization, AF burden reduction, unplanned hospitalization due to cardiovascular reason, all-cause hospitalization, quality of life, number of delivered implantable cardioverter defibrillator therapies, time to first implantable cardioverter defibrillator therapy, number of device-detected ventricular tachycardia/ventricular fibrillation episodes, left ventricular function, exercise tolerance, and percentage of right ventricular pacing. Ventricular myocardial tissue will be obtained from patients who will undergo LVAD implantation or HTx to assess the effect of catheter ablation on human HF myocardium. CASTLE-HTx will randomize 194 patients over a minimum time period of 2 years. Conclusions CASTLE-HTx will determine if AF ablation has beneficial effects on mortality in patients with end-stage HF who are eligible for HTx.

Mechanical unloading by ventricular assist devices (VADs) has become increasingly important for the therapy of end-stage heart failure during the last decade. However, VAD support was claimed to be associated with partial reverse remodelling. Unfortunately, the literature describes the contradictory effects of VAD systems on cardiac fibrosis, a hallmark of cardiac remodelling. To clarify these inconsistent results, the effects on cardiac fibrosis before and after mechanical unloading in 125 patients were examined.