NEXN inhibits GATA4 and leads to atrial septal defects in mice and humans

Aims Cardiac structural genes have been implicated as causative factors for congenital heart diseases (CHDs). NEXN is an F-actin binding protein and previously identified as a disease gene causing cardiomyopathies. Whether NEXN contributes to CHDs aetiologically remains unknown. Here, we explored the function of NEXN in cardiac development. Methods and results First, we determine the role of NEXN in cardiac differentiation using mouse P19cl6 in vitro model; we demonstrated that NEXN inhibited cardiac contractile markers, serving as a negative regulator. Interestingly, we found this effect was mediated by GATA4, a crucial transcription factor that controls cardiac development by knockdown, overexpression, and rescue experiment, respectively. We then generated transgenic mouse models and surprisingly, we discovered cardiac-selective expression of the NEXN gene caused atrial septal defects (ASDs). Next, to search for the mutations in NEXN gene in patients suffering from ASDs, we sequenced the exon and exon-intron joint regions of the NEXN gene in 150 probands with isolated ASDs and identified three mutations in the conserved region of NEXN (c.-52-78C>A, K199E, and L227S), which were not found in 500 healthy controls. Finally, we characterize the related mechanisms and found all mutations inhibited GATA4 expression. Conclusion We identify NEXN as a novel gene for ASD and its function to inhibit GATA4 established a critical regulation of an F-actin binding protein on a transcription factor in cardiac development.