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.

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.

Mutation of perinatal myosin heavy chain associated with a Carney complex variant.

BACKGROUND: Familial cardiac myxomas occur in the hereditary syndrome Carney complex. Although PRKAR1A mutations can cause the Carney complex, the disorder is genetically heterogeneous. To identify the cause of a Carney complex variant associated with distal arthrogryposis (the trismus-pseudocamptodactyly syndrome), we performed clinical and genetic studies. METHODS: A large family with familial cardiac myxomas and the trismus-pseudocamptodactyly syndrome (Family 1) was identified and clinically evaluated along with two families with trismus and pseudocamptodactyly. Genetic linkage analyses were performed with the use of microsatellite polymorphisms to determine a locus for this Carney complex variant. Positional cloning and mutational analyses of candidate genes were performed to identify the genetic cause of disease in the family with the Carney complex as well as in the families with the trismus-pseudocamptodactyly syndrome. RESULTS: Clinical evaluations demonstrated that the Carney complex cosegregated with the trismus-pseudocamptodactyly syndrome in Family 1, and genetic analyses demonstrated linkage of the disease to chromosome 17p12-p13.1 (maximum multipoint lod score, 4.39). Sequence analysis revealed a missense mutation (Arg674Gln) in the perinatal myosin heavy-chain gene (MYH8). The same mutation was also found in the two families with the trismus-pseudocamptodactyly syndrome. Arg674 is highly conserved evolutionarily, localizes to the actin-binding domain of the perinatal myosin head, and is close to the ATP-binding site. We identified nonsynonymous MYH8 polymorphisms in patients with cardiac myxoma syndromes but without arthrogryposis. CONCLUSIONS: We describe a novel heart-hand syndrome involving familial cardiac myxomas and distal arthrogryposis and demonstrate that these disorders are caused by a founder mutation in the MYH8 gene. Our findings demonstrate novel roles for perinatal myosin in both the development of skeletal muscle and cardiac tumorigenesis.

Haploinsufficiency at the protein kinase A RI alpha gene locus leads to fertility defects in male mice and men.

Carney complex (CNC) is a familial multiple neoplasia syndrome characterized by spotty skin pigmentation, cardiac and cutaneous myxomas, and endocrine tumors. CNC is inherited as an autosomal dominant trait and is transmitted with greater frequency by women vs. men. Nearly two thirds of CNC patients are heterozygous for inactivating mutations in the gene encoding the protein kinase A (PKA) type I alpha regulatory subunit (RI alpha), PRKAR1. We report here that male mice heterozygous for the Prkar1a gene have severely reduced fertility. Sperm from Prkar1a heterozygous mice are morphologically abnormal and reduced in number. Genetic rescue experiments reveal that this phenotype results from elevated PKA catalytic activity in germ cells as early as the pachytene stage of spermatogenesis. Consistent with this defect in the male mutant mice, sperm from CNC patients heterozygous for PRKAR1A mutations were also found to be morphologically aberrant and decreased in number. We conclude that unregulated PKA activity in male meiotic or postmeiotic germ cells leads to structural defects in mature sperm and results in reduced fertility in mice and humans, contributing to the strikingly reduced transmission of PRKAR1A inactivating mutations by male patients with CNC.

Genetics of cardiac septation defects and their pre-implantation diagnosis.

Cardiac septation defects are among the most common birth defects in humans. The frequency of these defects reflects the complexity of cardiogenesis, which involves such processes as cell proliferation, migration, differentiation, and morphogenetic interactions. Major advances in the understanding of the underlying genetic etiologies of cardiac septation defects have provided insight into the genetic pathways involved. These genetic factors are most often transcription factors involved in the early stages of cardiogenesis. The ability to modify these genes in animal models is providing a better understanding of the role of these genes in common pathways leading to diverse forms of cardiac defects. Ultimately, our understanding of these basic processes should lead to molecular-based treatment and prevention options for those individuals most at risk for such birth defects.

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.

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.

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.

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 individual's 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. METHODS AND RESULTS: Subjects presented for clinical electrophysiologic evaluation of suspected WPW syndrome. WPW syndrome was diagnosed by ECG findings and/or by clinically indicated electrophysiologic study prior to enrollment. Echocardiography excluded hypertrophic cardiomyopathy. Denaturing high-performance liquid chromatography and automated sequencing were used to search for PRKAG2 mutations. Twenty-six patients without a family history of WPW syndrome were studied. No subject had cardiac hypertrophy, and only one patient had associated congenital heart disease. Accessory pathways were detected at diverse locations within the heart. Two polymorphisms in PRKAG2 were detected. [inv6+36insA] occurred in intron 6 in 4 WPW patients and [inv10+10delT] in intron 10 in 1 WPW patient. Both occurred in normal unrelated chromosomes. No PRKAG2 mutations were detected. CONCLUSION: This study shows that, unlike familial WPW syndrome, constitutional mutation of PRKAG2 is not commonly associated with sporadic WPW syndrome. Although polymorphisms within the PRKAG2 introns were identified, there is no evidence that these polymorphisms predispose to accessory pathway formation because their frequency is similarly high in both WPW patients and normal individuals. Further studies are warranted to identify the molecular basis of common sporadic WPW syndrome.

Comparative PRKAR1A genotype-phenotype analyses in humans with Carney complex and prkar1a haploinsufficient mice.

Carney complex (CNC) is a familial multiple neoplasia syndrome characterized by cardiac and extracardiac myxomas in the setting of spotty skin pigmentation and endocrinopathy. We previously identified PRKAR1A (regulatory subunit 1alpha of protein kinase A) mutations in CNC. Mutational analyses of the PRKAR1A gene in 51 unrelated CNC probands now detect mutations in 65%. All mutations, except for one unique missense mutation, lead to PRKAR1A haploinsufficiency. Therefore, we studied the consequences of prkar1a haploinsufficiency in mice. Although we did not observe cardiac myxomas or altered pigmentation in prkar1a(+/-) mice, we did observe some phenotypes similar to CNC, including altered heart rate variability. Moreover, prkar1a(+/-) mice exhibited a marked propensity for extracardiac tumorigenesis. They developed sarcomas and hepatocellular carcinomas. Sarcomas were frequently associated with myxomatous differentiation. Tumors from prkar1a(+/-) mice did not exhibit prkar1a loss of heterozygosity. Thus, we conclude that although PRKAR1A haploinsufficiency does predispose to tumorigenesis, distinct secondary genetic events are required for tumor formation.