Identification of circular RNA hsa-PHACTR4_0009 as a new class of biomarker for transposition of the great arteries.

Dextro-Transposition of great arteries (d-TGA) is a cardiac birth anomaly with reversed anatomic position of the aorta and pulmonary artery, with a poor prognosis. The molecular aetiology of d-TGA remains elusive, possibly due to polygenic contributions and gene-environment interactions, suggesting the role of epigenetic components in d-TGA. Various non-coding RNAs, like circular RNA (circRNA), epigenetically regulate gene expression and may also serve as putative biomarkers because of their exceptionally high stability in plasma. In this study, we performed whole transcriptome analysis in the plasma of diseased and healthy neonates to identify circular RNA specifically dysregulated in the d-TGA condition. Our data suggested that a circular RNA, i.e., hsa-PHACTR4_0009, is significantly increased in the plasma of d-TGA neonates and has 85 % sensitivity and 80 % specificity with an AUC value of 0.900 with foetal echocardiography as the gold standard. Interestingly, d-TGA cases had a proportional increase of hsa-PHACTR4_0009 with the severity of the disease, as evident by comparably high levels in patients with intact interventricular and interatrial septa. Transcriptomics analysis further indicated that there is a dysregulation of the focal adhesion assembly genes like vimentin, profilin, gamma-actin and emerin, corroborating with hsa-PHACTR4_0009 expression. Notably, overexpression of hsa-PHACTR4_0009 led to increased cell migration in H9C2 cells, suggesting that defects in cell migration are involved in the development of d-TGA. Collectively, our study suggests hsa-PHACTR4_0009 as a potential biomarker of d-TGA and provides a highly valuable insight into the molecular pathogenesis of d-TGA from an unexplored perspective, enabling a better prognosis for these patients.