Exclusion of Cx43 gene mutation as a major cause of criss-cross heart anomaly in man

Crisscross heart with situs invesus in pregnancy: A rare case report and literature review

Crisscross heart(CCH) is a rare congenital anomaly. CCH is always with rare complex congenital heart malformations, and for this reason it is difficult to diagnose. We present an asymptomatic 29-year-old pregant woman with history of cardiac murmur at 28 weeks of gestation. Transthoracic echocardiography revealed a CCH with situs inversus, concordant atrioventricular, double outlet right ventricle, ventricular septum defect and pulmonary stenosis. The anomalies were demonstrated by two-dimensional echocardiography and confirmed by color Doppler imaging. The patient was stable and did not require surgical interventions. She underwent successful term vaginal delivery without complication and her baby had a normal heart. Patients with CCHs can be diagnosed by a careful, systematic study with two-dimensional and Doppler echocardiography to identify the ventricular morphology and position, determine the sequence of connections and spatial relationships of the cardiac chambers and identify other abnormalities.

Association of Cx43 rs2071166 polymorphism with an increased risk for atrial septal defect

Atrial septal defect is one of the most common CHD. The pathogenesis of atrial septal defect still remains unknown. Cx43 is the most prevalent connexin in the mammalian heart during development. Its genetic variants can cause several CHD. The aim of our study was to investigate the association of genetic variations of the Cx43 with sporadic atrial septal defect. A total of 450 paediatric patients were recruited, including 150 cases with atrial septal defect and 300 healthy controls. The promoter region of Cx43 was analysed by sequencing after polymerase chain reaction. All data were analysed by using the Statistic Package for Social Science 19.0 software. The frequency of the single nucleotide polymorphism rs2071166 was significantly higher in atrial septal defect cases than in healthy controls. The CC genotype at rs2071166 site in Cx43 was correlated with an increased risk for atrial septal defect (p<0.0001, odds ratio=3.891, 95% confidence interval 1.948-7.772) and the C allele was positively correlated with atrial septal defect (p=0.007, odds ratio=1.567, 95% confidence interval 1.129-2.175). In conclusion, our results confirmed that rs2071166 in Cx43 may be relevant with an increased atrial septal defect risk.

Evaluating the role of connexin43 in congenital heart disease: Screening for mutations in patients with outflow tract anomalies and the analysis of knock-in mouse models

Background:

GJA1 gene encodes a gap junction protein known as connexin 43 (Cx43). Cx43 is abundantly expressed in the ventricular myocardium and in cardiac neural crest cells. Cx43 is proposed to play an important role in human congenital heart disease, as GJA1 knock-out mice die neonatally from outflow tract obstruction. In addition, patients with visceroatrial heterotaxia or hypoplastic left heart syndrome were reported to have point mutations in GJA1 at residues that affect protein kinase phosphorylation and gating of the gap junction channel. However, as these clinical findings were not replicated in subsequent studies, the question remains about the contribution of GJA1 mutations in human congenital heart disease (CHD).

Materials and Methods:

We analyzed the GJA1 coding sequence in 300 patients with CHD from two clinical centers, focusing on outflow tract anomalies. This included 152 with Tetralogy of Fallot from over 200 patients exhibiting outflow tract anomalies, as well as other structural heart defects including atrioventricular septal defects and other valvar anomalies. Our sequencing analysis revealed only two silent nucleotide substitutions in 8 patients. To further assess the possible role of Cx43 in CHD, we also generated two knock-in mouse models with point mutations at serine residues subject to protein kinase C or casein kinase phosphorylation, sites that are known to regulate gating and trafficking of Cx43, respectively.

Results:

Both heterozygous and homozygous knock-in mice were long term viable and did not exhibit overt CHD.

Conclusion:

The combined clinical and knock-in mouse mutant studies indicate GJA1 mutation is not likely a major contributor to CHD, especially those involving outflow tract anomalies.