The Complex and Diverse Genetic Architecture of Dilated Cardiomyopathy.

Our insight into the diverse and complex nature of dilated cardiomyopathy (DCM) genetic architecture continues to evolve rapidly. The foundations of DCM genetics rest on marked locus and allelic heterogeneity. While DCM exhibits a Mendelian, monogenic architecture in some families, preliminary data from our studies and others suggests that at least 20% to 30% of DCM may have an oligogenic basis, meaning that multiple rare variants from different, unlinked loci, determine the DCM phenotype.

Gain-of-Function Variants in Dilated Cardiomyopathy.

Background: Dilated cardiomyopathy (DCM) is a genetically heterogeneous cardiac disease characterized by progressive ventricular enlargement and reduced systolic function. Here, we report genetic and functional analyses implicating the rat sarcoma signaling protein, SOS1 (Son of sevenless homolog 1), in DCM pathogenesis.

Methods: Exome sequencing was performed on 412 probands and family members from our DCM cohort, identifying several variants with potential disease involvement.

Multigenic Disease and Bilineal Inheritance in Dilated Cardiomyopathy Is Illustrated in Nonsegregating LMNA Pedigrees.

Background: We have previously described 19 pedigrees with apparent lamin ()-related dilated cardiomyopathy (DCM) manifesting in affected family members across multiple generations. In 6 of 19 families, at least 1 individual with idiopathic DCM did not carry the family's variant. We hypothesized that additional genetic cause may underlie DCM in these families.

Copy number variation as a genetic basis for heterotaxy and heterotaxy-spectrum congenital heart defects.

Genomic disorders and rare copy number abnormalities are identified in 15-25% of patients with syndromic conditions, but their prevalence in individuals with isolated birth defects is less clear. A spectrum of congenital heart defects (CHDs) is seen in heterotaxy, a highly heritable and genetically heterogeneous multiple congenital anomaly syndrome resulting from failure to properly establish left-right (L-R) organ asymmetry during early embryonic development. To identify novel genetic causes of heterotaxy, we analysed copy number variants (CNVs) in 225 patients with heterotaxy and heterotaxy-spectrum CHDs using array-based genotyping methods.

Genetics and genetic testing in congenital heart disease.

Congenital heart defects (CHDs) are structural abnormalities of the heart and great vessels that are present from birth. The presence or absence of extracardiac anomalies has historically been used to identify patients with possible monogenic, chromosomal, or teratogenic CHD causes. These distinctions remain clinically relevant, but it is increasingly clear that nonsyndromic CHDs can also be genetic.

Genetic and functional analyses of ZIC3 variants in congenital heart disease.

Mutations in zinc-finger in cerebellum 3 (ZIC3) result in heterotaxy or isolated congenital heart disease (CHD). The majority of reported mutations cluster in zinc-finger domains. We previously demonstrated that many of these lead to aberrant ZIC3 subcellular trafficking.

Return of genetic results in the familial dilated cardiomyopathy research project.

The goal of the Familial Dilated Cardiomyopathy (FDC) Research Project, initiated in 1993, has been to identify and characterize FDC genetic cause. All participating individuals have been consented for the return of genetic results, an important but challenging undertaking. Since the inception of the Project we have enrolled 606 probands, and 269 of these had 1670 family members also enrolled.

Maternal smoking at first prenatal visit as a marker of risk for adverse pregnancy outcomes in the Qikiqtaaluk (Baffin) Region.

Introduction: In Nunavut, 60-80% of pregnant women report smoking in pregnancy, a rate five times the Canadian average. Nunavut also has the highest rates of preterm birth and low birth weight infants in Canada. The present study assessed whether the number of cigarettes smoked per day, as recorded in the first trimester, influenced birth outcomes.

Morphological analysis of 13 LMNA variants identified in a cohort of 324 unrelated patients with idiopathic or familial dilated cardiomyopathy.

Background: Mutations in the LMNA gene, encoding lamins A/C, represent a significant cause of dilated cardiomyopathy. We recently identified 18 protein-altering LMNA variants in a cohort of 324 unrelated patients with dilated cardiomyopathy. However, at least one family member with dilated cardiomyopathy in each of 6 pedigrees lacked the LMNA mutation (nonsegregation), whereas small sizes of 5 additional families precluded definitive determinations of segregation, raising questions regarding contributions by those variants to disease.

Clinical and functional characterization of TNNT2 mutations identified in patients with dilated cardiomyopathy.

Background: A key issue for cardiovascular genetic medicine is ascertaining if a putative mutation indeed causes dilated cardiomyopathy (DCM). This is critically important as genetic DCM, usually presenting with advanced, life-threatening disease, may be preventable with early intervention in relatives known to carry the mutation.

Methods And Results: We recently undertook bidirectional resequencing of TNNT2, the cardiac troponin T gene, in 313 probands with DCM.

Progress with genetic cardiomyopathies: screening, counseling, and testing in dilated, hypertrophic, and arrhythmogenic right ventricular dysplasia/cardiomyopathy.

This review focuses on the genetic cardiomyopathies: principally dilated cardiomyopathy, with salient features of hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia/cardiomyopathy, regarding genetic etiology, genetic testing, and genetic counseling. Enormous progress has recently been made in identifying genetic causes for each cardiomyopathy, and key phenotype and genotype information is reviewed. Clinical genetic testing is rapidly emerging with a principal rationale of identifying at-risk asymptomatic or disease-free relatives.

Genetic testing and genetic counseling in cardiovascular genetic medicine: overview and preliminary recommendations.

In this emerging era of cardiovascular genetic medicine, increasing responsibility will be placed on cardiovascular practitioners to be aware of the latest clinical genetic testing methods and the knowledge base needed to interpret genetic test results. Some cardiovascular specialists will develop the expertise within the field to order genetic testing and interpret results, while other practitioners will refer patients to centers of excellence in cardiovascular genetic medicine. A previous article in the Cardiovascular Genetic Medicine: Clinical Perspectives and Future Applications series(1) highlighted an increasing recognition of the cardiomyopathies (hypertrophic [HCM], dilated [DCM], arrhythmogenic right ventricular dysplasia [ARVD]) and channelopathies (long QT syndrome [LQTS] and others) as genetic diseases, and focused on the importance of a targeted family history as a critical part of patient evaluation.

Family history: an essential tool for cardiovascular genetic medicine.

We are pleased to provide a new section devoted to topics in cardiovascular genetic medicine. An emerging field, cardiovascular genetic medicine is devoted to the identification and understanding of cardiac conditions resulting from genetic mechanisms and to the development and validation of treatment algorithms and guidelines. Cardiovascular genetic medicine is rapidly enlarging, and we anticipate a broad range of comprehensive reviews.