Congenital heart defects in two siblings in an Axenfeld–Rieger syndrome family

Axenfeld-Rieger syndrome

Axenfeld-Rieger syndrome (ARS) is a clinically and genetically heterogeneous group of developmental disorders affecting primarily the anterior segment of the eye, often leading to secondary glaucoma. Patients with ARS may also present with systemic changes, including dental defects, mild craniofacial dysmorphism, and umbilical anomalies. ARS is inherited in an autosomal-dominant fashion; the underlying defect in 40% of patients is mutations in PITX2 or FOXC1. Here, an overview of the clinical spectrum of ARS is provided. As well, the known underlying genetic defects, clinical diagnostic possibilities, genetic counseling and treatments of ARS are discussed in detail.

Cardiac anomalies in Axenfeld-Rieger syndrome due to a novel FOXC1 mutation

Axenfeld-Rieger syndrome (ARS) is an autosomal dominant condition characterized by ophthalmologic anterior segment abnormalities and extraocular findings including dental anomalies and redundant periumbilical skin. Intragenic mutations in the homeobox gene PITX2 or the transcription factor encoding FOXC1 were identified, and genomic rearrangements encompassing either gene also cause ARS. A molecular etiology is identified in 40-60%. Extraocular anomalies occur more often with intragenic PITX2 than FOXC1 mutations. We report on a patient with infantile glaucoma presenting at age 21 months with congestive heart failure due to a dysplastic arcade mitral valve necessitating valve replacement, and mildly hypoplastic left ventricular outflow tract and aortic arch. Family history included early onset glaucoma in four relatives; congenital hip dysplasia requiring surgery in three; and an atrial septal defect in the affected maternal grandmother. Despite the absence of dental or umbilical abnormalities, anterior chamber abnormalities consistent with ARS were present in affected individuals. Molecular testing revealed a novel FOXC1 mutation (c.508C>T; p.Arg170Trp) in the proband and his affected mother; other family members were unavailable. A literature review revealed four reports of congenital heart disease associated with intragenic FOXC1 mutations, and none with intragenic PITX2 mutations. Previously, mouse studies showed Foxc1 (Mf1) expression in the developing valves and atrial septum, supporting a causal relationship of FOXC1 mutations for valvar anomalies and ASD. Hip dysplasia in three family members suggests a role for FOXC1 in the femoral head dysplasia of de Hauwere syndrome with 6p25 deletions. Further reports of clinical and molecular diagnoses will clarify genotype-phenotype correlation.

Xenopus: An emerging model for studying congenital heart disease

Congenital heart defects affect nearly 1% of all newborns and are a significant cause of infant death. Clinical studies have identified a number of congenital heart syndromes associated with mutations in genes that are involved in the complex process of cardiogenesis. The African clawed frog, Xenopus, has been instrumental in studies of vertebrate heart development and provides a valuable tool to investigate the molecular mechanisms underlying human congenital heart diseases. In this review, we discuss the methodologies that make Xenopus an ideal model system to investigate heart development and disease. We also outline congenital heart conditions linked to cardiac genes that have been well studied in Xenopus and describe some emerging technologies that will further aid in the study of these complex syndromes.