Tricuspid atresia and annular hypoplasia: report of a familial occurrence

Monochorionic Twin Discordance for Horseshoe Lung and Tricuspid Atresia

Background: The horseshoe lung is a congenital malformation in which the bases of the right and the left lung are fused. Case report: We describe a monochorionic twin gestation with malformation discordance. The abnormal twin had a horseshoe lung with hypoplasia of the right lung, tricuspid atresia, cleft lip, and a pelvic right kidney. Conclusion: The discordance of anomalies in this monochorionic twin suggests that a postzygotic mutation, epigenetic change, or environmental factors may be responsible for these malformations.

Prevalence rates study of selected isolated non-Mendelian congenital anomalies in the Hutterite population of Alberta, 1980-2016

A study of the prevalence rates for selected isolated non-Mendelian congenital anomalies in the Hutterite Brethren of Alberta, Canada was undertaken to further examine longitudinal data in this isolated community that was last reported in 1985 (Lowry et al., 1985), although there are numerous publications on recessive disorders (Boycott et al., 2008; Triggs-Raine et al., 2016). Cases were ascertained from the Alberta Congenital Anomaly Surveillance System for the years 1997-2016. Since our initial results showed some surprising findings in the Hutterite Brethren, such as zero cases of spina bifida, cleft lip and palate, gastroschisis, and omphalocele, and a significant excess of cases with hypospadias, we extended the study to prior years (1980-1996) for selected anomalies. For the extended study period (1980-2016), there was a significant increased prevalence of hypospadias, tetralogy of Fallot and tricuspid atresia in the Hutterite population, and although not statistically significant, zero cases of cleft lip with cleft palate, gastroschisis and omphalocele were confirmed. Further research is needed to determine the precise effects of rural environmental exposures, lifestyle factors, and genetic associations for selected multifactorial congenital anomalies.

Tricuspid atresia: Where are we now?

Tricuspid atresia (TA) is a complex congenital heart disease that presents with cyanosis in the neonatal period. It is invariably fatal if left untreated and requires multiple stages of palliation. Early recognition and timely surgical intervention are therefore pivotal in the management of these infants. This literature review considers the pathophysiology, presentation, investigations, and classification of TA. Moreover, it discusses the evidence upon which the latest medical and surgical treatments are based, as well as numerous recent case reports. Further work is needed to elucidate the etiology of TA, clarify the role of pharmacotherapy, and optimize the surgical management that these patients receive.

A Pathogenic Homozygous Mutation in The Pleckstrin Homology Domain of RASA1 Is Responsible for Familial Tricuspid Atresia in An Iranian Consanguineous Family

Objective

Tricuspid atresia (TA) is a rare life-threatening form of congenital heart defect (CHD). The genetic mechanisms underlying TA are not clearly understood. According to previous studies, the endocardial cushioning event, as the primary sign of cardiac valvulogenesis, is governed by several overlapping signaling pathways including Ras/ ERK pathway. RASA1, a regulator of cardiovascular development, is involved in this pathway and its haploinsufficiency (due to heterozygous mutations) has been identified as the underlying etiology of the autosomal dominant capillary malformation/arteriovenous malformation (CM/AVM).

Materials and Methods

In this prospective study, we used whole exome sequencing (WES) followed by serial bioinformatics filtering steps for two siblings with TA and early onset CM. Their parents were consanguineous which had a history of recurrent abortions. Patients were carefully assessed to exclude extra-cardiac anomalies.

Results

We identified a homozygous RASA1 germline mutation, c.1583A>G (p.Tyr528Cys) in the family. This mutation lies in the pleckstrin homology (PH) domain of the gene. The parents who were heterozygous for this variant displayed CM.

Conclusion

This is the first study reporting an adverse phenotypic outcome of a RASA1 homozygous mutation. Here, we propose that the phenotypic consequence of the homozygous RASA1 p.Tyr528Cys mutation is more serious than the heterozygous type. This could be responsible for the TA pathogenesis in our patients. We strongly suggest that parents with CM/AVM should be investigated for RASA1 heterozygous mutations. Prenatal diagnosis and fetal echocardiography should also be carried out in the event of pregnancy in heterozygous parents.

Congenital heart diseases in small animals: part II. Potential genetic aetiologies based on human genetic studies

Comparative genetics provides veterinary researchers and clinicians with invaluable information for the understanding the possible genetic aetiologies and the disease process in congenital heart defects (CHDs) of dogs and cats. Although, the demand on this type of research has increased in the veterinary field, to date no fundamental genetic studies have been reported in the veterinary literature. In this second part of a two-part review, the general features and pathogenesis of major CHDs in humans and small animals are discussed. In addition, the known genetic aetiologies in human CHDs have been considered in parallel to CHDs in small animals.

A syndrome of tricuspid atresia in mice with a targeted mutation of the gene encoding Fog-2

Tricuspid atresia (TA) is a common form of congenital heart disease, accounting for 1-3% of congenital cardiac disorders. TA is characterized by the congenital agenesis of the tricuspid valve connecting the right atrium to the right ventricle and both an atrial septal defect (ASD) and a ventricular septal defect (VSD). Some patients also have pulmonic stenosis, persistence of a left-sided superior vena cava or transposition of the great arteries. Most cases of TA are sporadic, but familial occurrences with disease in multiple siblings have been reported. Gata4 is a zinc-finger transcription factor with a role in early cardiac development. Gata4-deficient mice fail to form a ventral heart tube and die of circulatory failure at embryonic day (E) 8.5 (refs 6,7). Zfpm2 (also known as Fog-2) is a multi-zinc-finger protein that is co-expressed with Gata4 in the developing heart beginning at E8.5 (refs 8-10). Zfpm2 interacts specifically with the N-terminal zinc finger of Gata4 and represses Gata4-dependent transcription. Here we use targeted mutagenesis to explore the role of Zfpm2 in normal cardiac development. Zfpm2-deficient mice died of congestive heart failure at E13 with a syndrome of tricuspid atresia that includes an absent tricuspid valve, a large ASD, a VSD, an elongated left ventricular outflow tract, rightward displacement of the aortic valve and pulmonic stenosis. These mice also display hypoplasia of the compact zone of the left ventricle. Our findings indicate the importance of Zfpm2 in the normal looping and septation of the heart and suggest a genetic basis for the syndrome of tricuspid atresia.

The genetic basis of pediatric cardiovascular disease

Congenital heart disease (CHD), cardiomyopathy, and vasculopathies are common causes of mortality and morbidity in pediatrics, including the perinatal period. This article reviews evidence that single gene defects cause many of the pediatric heart diseases. Vasculopathies discussed include Marfan's syndrome, supravalvar aortic stenosis and Williams' syndrome, Alagille's syndrome, and hereditary telangiectasia, the Osler-Weber-Rendu syndrome. Genetic causes of hypertrophic cardiomyopathy caused by sarcomeric protein mutations (beta-cardiac myosin heavy chain) and of dilated cardiomyopathy secondary to structural protein deficiencies (dystrophin) are presented. Defects in proteins essential for myocardial energy production such as oxidative phosphorylation proteins and fatty acid oxidation genes that cause cardiomyopathy or sudden death are described. Gene ablation models in mice, such as RXR alpha and homeobox gene knockouts, which result in cardiac phenotypes resembling human congenital heart disease, are described. Familial types of human CHD which are being investigated for genetic causes by positional cloning methods and known cytogenetic causes of CHD, including the CATCH-22 syndrome and monosomy at 22q11, are presented. General lessons and principles derived from these new and exciting discoveries in human cardiovascular development are surmised.