Ana Morales

A novel human R25C-phospholamban mutation is associated with super-inhibition of calcium cycling and ventricular arrhythmia

AIMS Depressed sarcoplasmic reticulum (SR) Ca(2+) cycling, a universal characteristic of human and experimental heart failure, may be associated with genetic alterations in key Ca(2+)-handling proteins. In this study, we identified a novel PLN mutation (R25C) in dilated cardiomyopathy (DCM) and investigated its functional significance in cardiomyocyte Ca(2+)-handling and contractility. METHODS AND RESULTS Exome sequencing identified a C73T substitution in the coding region of PLN in a family with DCM. The four heterozygous family members had implantable cardiac defibrillators, and three developed prominent ventricular arrhythmias. Overexpression of R25C-PLN in adult rat cardiomyocytes significantly suppressed the Ca(2+) affinity of SR Ca(2+)-ATPase (SERCA2a), resulting in decreased SR Ca(2+) content, Ca(2+) transients, and impaired contractile function, compared with WT-PLN. These inhibitory effects were associated with enhanced interaction of R25C-PLN with SERCA2, which was prevented by PKA phosphorylation. Accordingly, isoproterenol stimulation relieved the depressive effects of R25C-PLN in cardiomyocytes. However, R25C-PLN also elicited increases in the frequency of Ca(2+) sparks and waves as well as stress-induced aftercontractions. This was accompanied by increased Ca(2+)/calmodulin-dependent protein kinase II activity and hyper-phosphorylation of RyR2 at serine 2814. CONCLUSION The findings demonstrate that human R25C-PLN is associated with super-inhibition of SERCA2a and Ca(2+) transport as well as increased SR Ca(2+) leak, promoting arrhythmogenesis under stress conditions. This is the first mechanistic evidence that increased PLN inhibition may impact both SR Ca(2+) uptake and Ca(2+) release activities and suggests that the human R25C-PLN may be a prognostic factor for increased ventricular arrhythmia risk in DCM carriers.

The Rationale and Timing of Molecular Genetic Testing for Dilated Cardiomyopathy

The genetic evaluation of dilated cardiomyopathy (DCM) has been challenging, owing in large part to marked genetic heterogeneity. However, lower costs from next-generation sequencing have enabled gene discovery and the expansion of genetic testing panels. These advances have improved molecular diagnostics and predictive testing in DCM. We provide a rationale and recommendation for clinical genetic testing in all DCM cases.

Novel familial dilated cardiomyopathy mutation in MYL2 affects the structure and function of myosin regulatory light chain

Dilated cardiomyopathy (DCM) is a disease of the myocardium characterized by left ventricular dilatation and diminished contractile function. Here we describe a novel DCM mutation in the myosin regulatory light chain (RLC), in which aspartic acid at position 94 is replaced by alanine (D94A). The mutation was identified by exome sequencing of three adult first‐degree relatives who met formal criteria for idiopathic DCM. To obtain insight into the functional significance of this pathogenic MYL2 variant, we cloned and purified the human ventricular RLC wild‐type (WT) and D94A mutant proteins, and performed in vitro experiments using RLC‐mutant or WT‐reconstituted porcine cardiac preparations. The mutation induced a reduction in the α‐helical content of the RLC, and imposed intra‐molecular rearrangements. The phosphorylation of RLC by Ca2+/calmodulin‐activated myosin light chain kinase was not affected by D94A. The mutation was seen to impair binding of RLC to the myosin heavy chain, and its incorporation into RLC‐depleted porcine myosin. The actin‐activated ATPase activity of mutant‐reconstituted porcine cardiac myosin was significantly higher compared with ATPase of wild‐type. No changes in the myofibrillar ATPase–pCa relationship were observed in wild‐type‐ or D94A‐reconstituted preparations. Measurements of contractile force showed a slightly reduced maximal tension per cross‐section of muscle, with no change in the calcium sensitivity of force in D94A‐reconstituted skinned porcine papillary muscle strips compared with wild‐type. Our data indicate that subtle structural rearrangements in the RLC molecule, followed by its impaired interaction with the myosin heavy chain, may trigger functional abnormalities contributing to the DCM phenotype.

Toward Genetics-Driven Early Intervention in Dilated Cardiomyopathy: Design and Implementation of the DCM Precision Medicine Study

Background— The cause of idiopathic dilated cardiomyopathy (DCM) is unknown by definition, but its familial subtype is considered to have a genetic component. We hypothesize that most idiopathic DCM, whether familial or nonfamilial, has a genetic basis, in which case a genetics-driven approach to identifying at-risk family members for clinical screening and early intervention could reduce morbidity and mortality. Methods— On the basis of this hypothesis, we have launched the National Heart, Lung, and Blood Institute- and National Human Genome Research Institute-funded DCM Precision Medicine Study, which aims to enroll 1300 individuals (600 non-Hispanic African ancestry, 600 non-Hispanic European ancestry, and 100 Hispanic) who meet rigorous clinical criteria for idiopathic DCM along with 2600 of their relatives. Enrolled relatives will undergo clinical cardiovascular screening to identify asymptomatic disease, and all individuals with idiopathic DCM will undergo exome sequencing to identify relevant variants in genes previously implicated in DCM. Results will be returned by genetic counselors 12 to 14 months after enrollment. The data obtained will be used to describe the prevalence of familial DCM among idiopathic DCM cases and the genetic architecture of idiopathic DCM in multiple ethnicity–ancestry groups. We will also conduct a randomized controlled trial to test the effectiveness of Family Heart Talk, an intervention to aid family communication, for improving uptake of preventive screening and surveillance in at-risk first-degree relatives. Conclusions— We anticipate that this study will demonstrate that idiopathic DCM has a genetic basis and guide best practices for a genetics-driven approach to early intervention in at-risk relatives. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT03037632.

Family history of dilated cardiomyopathy among patients with heart failure from the HF-ACTION genetic ancillary study

The value of family history (FH) is well established, but its sensitivity to detect familial dilated cardiomyopathy (FDC) has been infrequently examined.

Erratum to: At the Heart of the Pregnancy: What Prenatal and Cardiovascular Genetic Counselors Need to Know about Maternal Heart Disease

1 Department of Internal Medicine, The Ohio State University, Columbus, OH, USA 2 Human Genetics Division, The Ohio State University, 306 BRT, 460 W. 12th Ave, Columbus, OH 43210, USA 3 Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA 4 Allegheny General Hospital, Pittsburgh, PA, USA 5 Institute of Genetic Medicine, Johns Hopkins University, Baltimore, MD, USA 6 Division of Cardiology, Johns Hopkins University, Baltimore, MD, USA 7 Heart Institute, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA

Clinical Application of Genetic Testing in Heart Failure

Purpose of ReviewThe purpose of this review is to present our current understanding of the genetic etiologies that may cause or predispose to heart failure. We highlight known phenotypes for which a genetic evaluation has clinical utility.Recent FindingsThe literature continues to demonstrate and confirm a genetic basis for conditions that cause heart failure. Evidence suggests a genetic model involving rare and common variants of strong or weak effect, in combination with environmental factors that may manifest as familial or simplex disease. Clinical genetic testing is available for several phenotypes, which can aid in the diagnosis and identification of at-risk family members.SummaryThe evaluation of heart failure should include investigating etiologies with a genetic basis. Conducting a genetic evaluation in patients with heart failure requires the ability to identify possible genetic etiologies in an individual’s phenotype, obtain relevant family history, and clinically interpret genetic testing results.

Is Left Ventricular Noncompaction a Trait, Phenotype, or Disease?: The Evidence Points to Phenotype

The question is is left ventricular noncompaction (LVNC) a trait, phenotype, or disease? By trait, we refer to a discrete and measurable characteristic like eye color. The term phenotype expands this definition to include multiple observable traits derived from diverse genetic factors (genotype) and to recognize additional roles for the environment in shaping visible expression of a genetically defined trait. Pathological phenotypes, with their myriad signs, symptoms, diagnoses, and prognoses, are recognized as diseases and are most often associated with adverse clinical manifestations or need for medical or surgical intervention. See Article by Miller et al So where in this conceptual framework do we place LVNC? This is a well-debated topic1,2 and one that has been recently systematically and expertly reviewed in much greater depth than afforded by this editorial.1–4 Although LVNC has increasingly been recognized as a cardiomyopathy5—itself a term with clear disease connotations—mounting evidence now points to reclassification of LVNC as a distinct but not necessarily pathological phenotype. More specifically, the degree of compacted to noncompacted (NC) myocardium, by itself alone, does not seem to cause disease. Why phenotype rather than trait? Traits are considered to be genetically driven and not malleable by the environment. As defined above, genetics interacting with environment are best labeled as phenotype. Left ventricular (LV) morphology is not fixed for certain characteristics, including LV wall thickness or LV size. The former is well known to increase with severe hypertension or aortic stenosis, and the latter increases with volume overload from aortic insufficiency. With medical or surgical therapy, both conditions will regress. A similar paradigm has been observed with dilated cardiomyopathy—a disease phenotype associated with heart failure and arrhythmia for which the dilated or remodeled left ventricle will reverse remodel with appropriate medical therapy. Characteristics such …