Discovery of GJC1 (Cx45) as a New Gene Underlying Congenital Heart Disease and Arrhythmias

Abstract

As the most prevalent type of birth malformation, congenital heart disease (CHD) gives rise to substantial mortality and morbidity as well as a socioeconomic burden. Although aggregating investigations highlight the genetic basis for CHD, the genetic determinants underpinning CHD remain largely obscure. In this research, a Chinese family suffering from autosomal dominant CHD (atrial septal defect) and arrhythmias was enrolled. A genome-wide genotyping with microsatellite markers followed by linkage assay as well as sequencing analysis was conducted. The functional effects of the discovered genetic mutation were characterized by dual patch-clamp electrophysiological recordings in N2A cells and propidium iodide uptake assays in HeLa cells. As a result, a novel genetic locus for CHD and arrhythmias was located on chromosome 17q21.31-q21.33, a 4.82-cM (5.12 Mb) region between two markers of D17S1861 and D17S1795. Sequencing assays of the genes at the mapped locus unveiled a novel heterozygous mutation in the GJC1 gene coding for connexin 45 (Cx45), NM_005497.4:c.550A>G;p.R184G, which was in co-segregation with the disease in the whole family and was not observed in 516 unrelated healthy individuals or gnomAD. Electrophysiological analyses revealed that the mutation significantly diminished the coupling conductance in homomeric cell pairs (R184G/R184G) and in cell pairs expressing either R184G/Cx45 or R184G/Cx43. Propidium iodide uptake experiments demonstrated that the Cx45 R184G mutation did not increase the Cx45 hemichannel function. This investigation locates a new genetic locus linked to CHD and arrhythmias on chromosome 17q21.31-q21.33 and indicates GJC1 as a novel gene predisposing to CHD and arrhythmias, implying clinical implications for prognostic risk assessment and personalized management of patients affected with CHD and arrhythmias.

Genetically engineered human embryonic kidney cells as a novel vehicle for dual patch clamp study of human gap junction channels

“…Here we showed that Cx26 was able to form functional GJ channels in DKO HEK293 cells and in some cases with only one or two channels between a cell pair providing an excellent vehicle to study mechanistic defects associated Cx26 mutants in individual GJ channels. Expression of a congenital heart disease and arrhythmia linked mutation in Cx45 (R184G) in DKO HEK293 cells resulted in no functional GJ formed, similar to that observed in N2A cells [53]. The failure to cluster at the cell-cell junctions of Cx45 R184G in DKO HEK293 cells was also observed in HeLa cells (Chen and Bai unpublished observations).…”

“…To reveal the mechanism of a congenital heart disease and arrhythmia linked Cx45 variant R184G [53], we expressed this variant in DKO HEK293 cells in two expression vectors, i.e. GFP untagged Cx45 R184G-IRES-GFP and GFP tagged Cx45 R814G-GFP for functional and morphological studies respectively.…”

Cor Triatriatum Dexter Associated with an Ostium Primum Atrial Defect and Left-Sided Opening of the Coronary Sinus in a Stillborn Fetus

“…In general, more than 50% of all CHD cases still fall into the unknown category [ 28 ]. Most cases with known etiology are believed to be caused by genomic abnormalities, including mutations in genes important for heart development such as transcription factors [ 29 ] or structural heart genes [ 30 ], but also maternal environmental factors such as diabetes [ 31 ], a high-fat diet [ 32 ], ethanol abuse [ 33 ] or exposure to other teratogens including prenatal viral infections (recently reviewed in [ 28 ]). The defects of atrial septation, as noted in our case, are far more common in mammals than in other vertebrates, probably due to its higher complexity with primary and secondary septa [ 34 ].…”