Two Functional MicroRNA-126s Repress a Novel Target Gene p21-Activated Kinase 1 to Regulate Vascular Integrity in Zebrafish

Rationale:MicroRNAs (miRNAs) are key regulators of vascular development and diseases. The function and underlying mechanism of endothelial miRNAs have not been fully defined. Objective:To investigate the role of endothelial miR-126 in zebrafish vascular development. Methods and Results:Two homologs of miR-126, miR-126a (namely miR-126 in previous literature) and miR-126b, with only 1 nucleotide difference in their mature sequences, were identified in zebrafish genome. In vitro analysis showed that both precursors could sufficiently produce mature functional miRNAs. Expression analyses by Northern blot and quantitative RT-PCR showed that both miR-126s accumulated significantly 12 hours after fertilization and were specifically expressed in endothelial cells of zebrafish. Inhibition of miR-126a or miR-126b with specific morpholinos caused cranial hemorrhage, and simultaneous inhibition of both miR-126s resulted in a pronounced hemorrhage in higher percentage of embryos. Bioinformatics prediction showed that...