Deborah A. McDermott

Mutations in the desmosomal protein plakophilin-2 are common in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with fibrofatty replacement of cardiac myocytes, ventricular tachyarrhythmias and sudden cardiac death. In 32 of 120 unrelated individuals with ARVC, we identified heterozygous mutations in PKP2, which encodes plakophilin-2, an essential armadillo-repeat protein of the cardiac desmosome. In two kindreds with ARVC, disease was incompletely penetrant in most carriers of PKP2 mutations.

Relevance of Genetics and Genomics for Prevention and Treatment of Cardiovascular Disease A Scientific Statement From the American Heart Association Council on Epidemiology and Prevention, the Stroke Council, and the Functional Genomics and Translational Biology Interdisciplinary Working Group

Atherosclerotic cardiovascular disease (CVD) is a major health problem in the United States and around the world. Evidence accumulated over decades convincingly demonstrates that family history in a parent or a sibling is associated with atherosclerotic CVD, manifested as coronary heart disease, stroke, and/or peripheral arterial disease. Although there are several mendelian disorders that contribute to CVD, most common forms of CVD are believed to be multifactorial and to result from many genes, each with a relatively small effect working alone or in combination with modifier genes and/or environmental factors. The identification and the characterization of these genes and their modifiers would enhance prediction of CVD risk and improve prevention, treatment, and quality of care. This scientific statement describes the approaches researchers are using to advance understanding of the genetic basis of CVD and details the current state of knowledge regarding the genetics of myocardial infarction, atherosclerotic CVD, hypercholesterolemia, and hypertension. Current areas of interest and investigation—including gene–environment interaction, pharmacogenetics, and genetic counseling—are also discussed. The statement concludes with a list of specific recommendations intended to help incorporate usable knowledge into current clinical and public health practice, foster and guide future research, and prepare both researchers and practitioners for the changes likely to occur as molecular genetics moves from the laboratory to clinic.

TBX5 genetic testing validates strict clinical criteria for Holt-Oram syndrome

Holt-Oram syndrome (HOS) is an autosomal dominant heart-hand syndrome characterized by congenital heart disease (CHD) and upper limb deformity, and caused by mutations in the TBX5 gene. To date, the sensitivity of TBX5 genetic testing for HOS has been unclear. We now report mutational analyses of a nongenetically selected population of 54 unrelated individuals who were consecutively referred to our center with a clinical diagnosis of HOS. TBX5 mutational analyses were performed in all individuals, and clinical histories and findings were reviewed for each patient without reference to the genotypes. Twenty-six percent of the complete cohort was shown to have mutations of the TBX5 gene. However, among those subjects for whom clinical review demonstrated that their presentations met strict diagnostic criteria for HOS, TBX5 mutations were identified in 74%. No mutations were identified in those subjects who did not meet these criteria. Thus, these studies validate our clinical diagnostic criteria for HOS including an absolute requirement for preaxial radial ray upper limb malformation. Accordingly, TBX5 genotyping has high sensitivity and specificity for HOS if stringent diagnostic criteria are used in assigning the clinical diagnosis.

Clinical phenotypes and molecular genetic mechanisms of Carney complex

Carney complex is a familial multiple neoplasia disorder with characteristic features such as cardiac and cutaneous myxomas and spotty pigmentation of the skin. Clinical genetic analyses have shown that Carney complex is transmitted in an autosomal dominant way and can present with a wide array of other tumours, such as psammomatous melanotic schwannoma, testicular Sertoli-cell tumours, and pituitary adenomas. Molecular genetic studies show that mutations in the PRKAR1A gene, encoding the R1alpha regulatory subunit of cyclic-AMP-dependent protein kinase A, are the cause of Carney complex in most patients. Investigation of genetically engineered animal models confirms the role of PRKAR1A as a tumour suppressor and has begun to elaborate mechanisms underlying tumorigenesis in this disorder. Further genetic studies in human beings have highlighted novel variant phenotypes, such as congenital contractures, which are potentially associated with Carney complex, and have identified alternative genetic pathways to cardiac tumorigenesis, including mutation of the MYH8 gene that encodes perinatal myosin.

Adults with genetic syndromes and cardiovascular abnormalities: clinical history and management

Cardiovascular abnormalities, especially structural congenital heart defects, commonly occur in malformation syndromes and genetic disorders. Individuals with syndromes comprise a significant proportion of those affected with selected congenital heart defects such as complete atrioventricular canal, interrupted arch type B, supravalvar aortic stenosis, and pulmonary stenosis. As these individuals age, they contribute to the growing population of adults with special health care needs. Although most will require longterm cardiology follow-up, primary care providers, geneticists, and other specialists should be aware of (1) the type and frequency of cardiovascular abnormalities, (2) the range of clinical outcomes, and (3) guidelines for prospective management and treatment of potential complications. This article reviews fundamental genetic, cardiac, medical, and reproductive issues associated with common genetic syndromes that are frequently associated with a cardiovascular abnormality. New data are also provided about the cardiac status of adults with a 22q11.2 deletion and with Down syndrome.

Genetics and Genomics for the Prevention and Treatment of Cardiovascular Disease: Update A Scientific Statement From the American Heart Association

Cardiovascular diseases (CVDs) are a major source of morbidity and mortality worldwide. Despite a decline of ≈30% over the past decade, heart disease remains the leading killer of Americans.1 For rare and familial forms of CVD, we are increasingly recognizing single-gene mutations that impart relatively large effects on individual phenotype. Examples include inherited forms of cardiomyopathy, arrhythmias, and aortic diseases. However, the prevalence of monogenic disorders typically accounts for a small proportion of the total CVD observed in the population. CVDs in the general population are complex diseases, with several contributing genetic and environmental factors. Although recent progress in monogenic disorders has occurred, we have seen a period of intense investigation to identify the genetic architecture of more common forms of CVD and related traits. Genomics serves several roles in cardiovascular health and disease, including disease prediction, discovery of genetic loci influencing CVD, functional evaluation of these genetic loci to understand mechanisms, and identification of therapeutic targets. For single-gene CVDs, progress has led to several clinically useful diagnostic tests, extending our ability to inform the management of afflicted patients and their family members. However, there has been little progress in developing genetic testing for complex CVD because individual common variants have only a modest impact on risk. The study of the genomics of complex CVDs is further challenged by the influence of environmental variables, phenotypic heterogeneity, and pathogenic complexity. Characterization of the clinical phenotype requires consideration of the clinical details of the diseases and traits under study. This update expands the prior scientific statement on the relevance of genetics and genomics for the prevention and treatment of CVDs.2 In the earlier report, we focused on the current status of the field, which consisted of predominantly family-based linkage studies and single-gene or mendelian mutations of relatively large phenotypic effect …

Preimplantation genetic diagnosis of human congenital heart malformation and Holt-Oram syndrome.

Holt–Oram syndrome (HOS) is a multiple malformation syndrome associated with congenital heart malformation (CHM) and caused by mutations in the TBX5 transcription factor. Effective prenatal genetic diagnosis of HOS is limited by factors that modify clinical manifestations and confound prediction of an individuals phenotype. Although preimplantation genetic diagnosis (PGD) has been applied to complex disorders with some cardiovascular manifestations, its utility in Mendelian CHM has not been previously demonstrated. We tested whether PGD and in vitro fertilization (IVF) technology, including oocyte donation, can identify fertilized eggs affected by HOS for potential embryo selection. Five donor oocytes were fertilized in vitro with sperm from a HOS patient heterozygous for a Glu69ter‐TBX5 mutation and then underwent embryo biopsy and genotyping. One carried the Glu69ter‐TBX5 mutation; all others had wildtype genotypes. Two wildtype blastocysts were transferred to the mother, and the resulting singleton pregnancy was successfully delivered. Mutational analysis of fetal amniocytes and postpartum umbilical cord blood confirmed PGD. Fetal ultrasonography as well as postpartum electrocardiography and echocardiography also validated accurate prediction of normal skeletal and cardiac phenotypes. We conclude that PGD is an effective reproductive strategy for HOS patients. As more genetic etiologies for CHM are identified, application of PGD as adjunctive therapy to IVF will be increasingly available to prevent transmission of such diseases from affected parents to their children. Clinical application of PGD must balance the benefits of avoiding disease transmission with the medical risks and financial burdens of IVF.

Molecular Genetic Analysis of PRKAG2 in Sporadic Wolff-Parkinson-White Syndrome

Introduction: Mutations in the PRKAG2 gene that encodes the gamma2 regulatory subunit of AMP‐activated protein kinase have been shown to cause autosomal dominant Wolff‐Parkinson‐White (WPW) syndrome associated with hypertrophic cardiomyopathy. Prior studies focused on familial WPW syndrome associated with other heart disease such as hypertrophic cardiomyopathy. However, such disease accounts for only a small fraction of WPW cases, and the contribution of PRKAG2 mutations to sporadic isolated WPW syndrome is unknown.

Atrial Fibrillation and Other Clinical Manifestations of Altered TBX5 Dosage in Typical Holt–Oram Syndrome

To the editor: We were pleased to read the recent study in Circulation Research by Postma et al1 that describes an activation mutation in TBX5 that causes Holt–Oram syndrome. These exciting findings validate prior studies (reviewed elsewhere2) showing that cytogenetic abnormalities that produce TBX5 duplication (and presumed TBX5 overexpression) result in phenotypes that include Holt–Oram syndrome associated abnormalities. Moreover, we3,4 and others5 have previously demonstrated in experimental models that cell biological consequences of diminished and augmented Tbx5 expression are similar. In aggregate, these prior findings and the current data support a model6 in which Tbx5 dosage must …

Using the TBX5 transcription factor to grow and sculpt the heart

TBX5 mutations cause the cardiac and limb defects of the autosomal dominant Holt–Oram syndrome (HOS). We have explored the role of the TBX5 transcription factor during cardiogenesis and have elucidated some of its functions in regulating myocardial cell proliferation and proepicardial cell migration. Our identification of TBX5 mutations has enabled us to offer genetic testing for diagnosis of HOS in patients and also to perform preimplantation genetic diagnosis on blastocysts for couples desiring to have a child unaffected by HOS. We hope that our genetic testing approach will serve as a paradigm for mutation screening in other inherited syndromes.