PITX2 Loss-of-Function Mutation Contributes to Congenital Endocardial Cushion Defect and Axenfeld-Rieger Syndrome

Abstract

Congenital heart disease (CHD), the most common type of birth defect, is still the leading non-infectious cause of infant morbidity and mortality in humans. Aggregating evidence demonstrates that genetic defects are involved in the pathogenesis of CHD. However, CHD is genetically heterogeneous and the genetic components underpinning CHD in an overwhelming majority of patients remain unclear. In the present study, the coding exons and flanking introns of the PITX2 gene, which encodes a paired-like homeodomain transcription factor 2essential for cardiovascular morphogenesis as well as maxillary facial development, was sequenced in 196 unrelated patients with CHD and subsequently in the mutation carrier’s family members available. As a result, a novel heterozygous PITX2 mutation, p.Q102X for PITX2a, or p.Q148X for PITX2b, or p.Q155X for PITX2c, was identified in a family with endocardial cushion defect (ECD) and Axenfeld-Rieger syndrome (ARS). Genetic analysis of the pedigree showed that the nonsense mutation co-segregated with ECD and ARS transmitted in an autosomal dominant pattern with complete penetrance. The mutation was absent in 800 control chromosomes from an ethnically matched population. Functional analysis by using a dual-luciferase reporter assay system revealed that the mutant PITX2 had no transcriptional activity and that the mutation eliminated synergistic transcriptional activation between PITX2 and NKX2.5, another transcription factor pivotal for cardiogenesis. To our knowledge, this is the first report on the association of PITX2 loss-of-function mutation with increased susceptibility to ECD and ARS. The findings provide novel insight into the molecular mechanisms underpinning ECD and ARS, suggesting the potential implications for the antenatal prophylaxis and personalized treatment of CHD and ARS.

A Novel Mutation in PITX2 in a Patient with Axenfeld-Rieger Syndrome

“…As specific genes have been identified as causally related to disorders of the anterior segment, the clinical spectrum is being clarified. Mutations in PITX2 have been reported to cause Axenfeld-Rieger syndrome Type 1 (OMIM 180500) [Tümer and Bach-Holm, 2009;Law et al, 2011;Chang et al, 2012;Li et al, 2014;Zhao et al, 2015;Seifi et al, 2016]. The patient reported herein has several features consistent with Axenfeld-Rieger syndrome: Peters anomaly, left eye opacity and ptosis, congenital heart defect, and small umbilical hernia.…”

“…Axenfeld-Rieger syndrome, a rare autosomal dominant condition, encompasses a range of anomalies including anterior segment dysgenesis of the eye, dental anomalies, maxillary hypoplasia, periumbilical anomalies, and congenital heart defects [Alward, 2000;Tümer and Bach-Holm, 2009;Chang et al, 2012;Zhao et al, 2015;Sun et al, 2016]. Mutations in the PITX2 (pairedlike homeodomain transcription factor 2; OMIM 601542), and FOXC1 (forkhead box C1; OMIM 601090) genes have been identified in families with Axenfeld-Rieger syndrome.…”

Corneal endothelial cell density and cardiovascular mortality

“…Although CNCC and CEC‐destined NCC's originate from anatomically separate cell fields within the cranial neural crest, work by Silla et al () and Chen et al () has shown that these transcription factors provide key developmental instructions to both. As evidence of the commonalities of heart and eye development, several investigators have reported the coinheritance of corneal/anterior segment dysgenesis syndromes with congenital cardiac defects as reported in studies by Titheradge et al (), Gripp et al (2013), Zhao et al (), Du et al (2014), and Khalil et al (). The underlying mechanisms responsible for NCC dysfunction in all of these related oculo‐cardiac syndromes are due to genetic mutations in FOXC1 and/or PITX2.…”

Translational issues for human corneal endothelial tissue engineering

“…In humans, PAX6 mutations may be associated with abnormalities of the Descemet's membrane and corneal endothelium (Kenyon, ), such as those seen in Peters' anomaly (Prosser and van Heyningen, ). Mutations of PITX2 (Zhao et al, ) and FOXC1 (Pasutto et al , ) have also been implicated in up to 63% of patients with Axenfeld–Rieger syndrome (Reis et al , ), which is characterized by abnormal corneal endothelium development and retention of primordial endothelial tissue across the iris surface and anterior chamber angle (Shields, ). Similar corneal endothelial developmental anomalies may be induced in animal models, such as zebrafish PAX6 orthologue mutants (Takamiya et al , ) and mice whose PITX2 and FOXC1 gene expression patterns have been modified (Berry et al , ).…”