Abstract 2174: MicroRNA 142–3p Regulates Heart Development, Somitegenesis and Hematopoiesis in the Stage of Early Mesoderm Formation
[Background] MicroRNAs (miRNAs) are small non-coding RNAs that repress the translation of messenger RNAs by binding to the 3′-untranslated regions (3′-UTR). They are critically involved in post-transcriptional regulation of various genes. miRNAs also play a pivotal role in the development of various organs. It was recently reported that aberrant miRNA expression causes developmental abnormalities and malfunction of the cardiovascular system, such as arrhythmia, angiogenesis and hypertrophy. However, most of the contribution of miRNAs in cardiac development remains unknown.
[Methods and Results]
We applied microRNA cloning to the surgical specimens from patients with severe heart failure who had undertaken the Batista operation, and identified mir-142–3p that was decreased in the failing hearts.
To clarify the role of mir-142–3p, we injected its antisense-morpholino into zebrafish embryo. Intriguingly, we observed abnormal cardiac phenotypes and insufficiency of somitegenesis in the knockdown (KD)-morphant. In the early developmental stage, a tiny heart, contractile dysfunction of ventricle, various kinds of cardiac arrhythmia such as 2:1 ratio of atrial: ventricular beating, and bradycardia were consistently observed. Histological examination revealed hyperplastic atrium, severe hypoplasia of the ventricle and disrupted muscle alignment. Moreover, erythropoiesis was also disrupted in KD-morphant. As revealed by hemoglobin staining, no red blood cell was observed in the circulating system.
To determine the mechanism, we performed DNA microarray analysis. As result, gene expression of One-eyed pinhead (Oep) and Spadetail were increased in mir-142–3p KD-morphant, which interact with the Nodal-signaling pathway and are together essential for the formation of cardiac and somatic mesoderm.
In luciferase reporter assay, mir-142–3p repressed luciferase activity on Oep-3′UTR in a dose-dependent manner.
In addition, we could restore the repression by inserting the point mutation to the target site of 3′UTR.
[Conclusions] These findings indicated that mir-142–3p plays a critical role in cardiac development, somitegenesis and hematopoiesis via the regulation of Oep in the early stage of mesoderm formation.