Spontaneous self-terminating atrial fibrillation (AF) is one of the most common heart rhythm disorders, yet the regulatory molecular mechanisms underlying this syndrome are rather unclear. In a recent paper published by researchers from the University of La Coruna, microRNA (miRNA) transcriptome and expression of candidate transcription factors (TFs) with potential roles in arrhythmogenesis, such as Pitx2, Tbx5, and myocardin (Myocd), were analyzed using LC Sciences’ miRNA microarray service, qRT-PCR, and Western blotting in left atrial (LA) samples from pigs with transitory AF established by right atrial tachypacing. This was shown to induce ectopic tachyarrhythmia caused rapid and substantial miRNA remodeling associated with a marked downregulation of Pitx2, Tbx5, and Myocd expression in atrial myocardium. The downregulation of Pitx2, Tbx5, and Myocd was inversely correlated with upregulation of the corresponding targeting miRNAs (miR-21, miR-10a/10b, and miR-1, resp.) in the LA of paced animals. Through in vitro transient transfections of HL-1 atrial myocytes, investigators further showed that upregulation of miR-21 did result in downregulation of Pitx2 in cardiomyocyte background. Their results suggest that immediate-early miRNA remodeling coupled with deregulation of TF expression underlies the onset of AF.


MicroRNA microarray expression profiling of the left atrium from paced versus nonpaced pigs.

Heat map of the most differentially expressed (statistically significant) miRNAs in the left atrium of three paced (4–6) compared to three sham (1–3) animals. Relative expression is log2.

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M. Torrado, D. Franco, E. Lozano-Velasco, F. Hernández-Torres, R. Calviño, G. Aldama, A. Centeno, A. Castro-Beiras, A. Mikhailov (2015) A MicroRNA-Transcription Factor Blueprint for Early Atrial Arrhythmogenic Remodeling BioMed Res Intl 2015:263151. [article]

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