MiR-144 regulates hematopoiesis and vascular development by targeting meis1 during zebrafish development.

Hematopoiesis is a dynamic process by which peripheral blood lineages are developed. It is a process tightly regulated by many intrinsic and extrinsic factors, including transcriptional factors and signaling molecules. However, the epigenetic regulation of hematopoiesis, for example, regulation via microRNAs (miRNAs), remains incompletely understood. Here we show that miR-144 regulates hematopoiesis and vascular development in zebrafish. Overexpression of miR-144 inhibited primitive hematopoiesis as demonstrated by a reduced number of circulating blood cells, reduced o-dianisidine staining of hemoglobin, and reduced expression of hbαe1, hbβe1, gata1 and pu.1. Overexpression of miR-144 also inhibited definitive hematopoiesis as shown by reduced expression of runx1 and c-myb. Mechanistically, miR-144 regulates hematopoiesis by repressing expression of meis1 involved in hematopoiesis. Both real-time RT-PCR and Western blot analyses showed that overexpression of miR-144 repressed expression of meis1. Bioinformatic analysis predicts a target binding sequence for miR-144 at the 3'-UTR of meis1. Deletion of the miR-144 target sequence eliminated the repression of meis1 expression mediated by miR-144. The miR-144-mediated abnormal phenotypes were partially rescued by co-injection of meis1 mRNA and could be almost completely rescued by injection of both meis1 and gata1 mRNA. Finally, because meis1 is involved in vascular development, we tested the effect of miR-144 on vascular development. Overexpression of miR-144 resulted in abnormal vascular development of intersegmental vessels in transgenic zebrafish with Flk1p-EGFP, and the defect was rescued by co-injection of meis1 mRNA. These findings establish miR-144 as a novel miRNA that regulates hematopoiesis and vascular development by repressing expression of meis1.

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