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Blood, 19 February 2009, Vol. 113, No. 8, pp. 1794-1804. Prepublished online as a Blood First Edition Paper on October 10, 2008; DOI 10.1182/blood-2008-05-155812.
RED CELLS, IRON, AND ERYTHROPOIESIS miR-451 regulates zebrafish erythroid maturation in vivo via its target gata21 Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; 2 Department of Medical Biology, University of Melbourne, Parkville, Australia; 3 Ludwig Institute for Medical Research, The Royal Melbourne Hospital, Parkville, Australia; 4 Hubrecht Laboratory, Centre for Biomedical Genetics, Utrecht, The Netherlands; and 5 CSIRO Plant Industry, Canberra, Australia We demonstrate that in zebrafish, the microRNA miR-451 plays a crucial role in promoting erythroid maturation, in part via its target transcript gata2. Zebrafish miR-144 and miR-451 are processed from a single precursor transcript selectively expressed in erythrocytes. In contrast to other hematopoietic mutants, the zebrafish mutant meunier (mnr) showed intact erythroid specification but diminished miR-144/451 expression. Although erythropoiesis initiated normally in mnr, erythrocyte maturation was morphologically retarded. Morpholino knockdown of miR-451 increased erythrocyte immaturity in wild-type embryos, and miR-451 RNA duplexes partially rescued erythroid maturation in mnr, demonstrating a requirement and role for miR-451 in erythrocyte maturation. mnr provided a selectively miR-144/451-deficient background, facilitating studies to discern miRNA function and validate candidate targets. Among computer-predicted miR-451 targets potentially mediating these biologic effects, the pro-stem cell transcription factor gata2 was an attractive candidate. In vivo reporter assays validated the predicted miR-451/gata2-3'UTR interaction, gata2 down-regulation was delayed in miR-451-knockdown and mnr embryos, and gata2 knockdown partially restored erythroid maturation in mnr, collectively confirming gata2 down-regulation as pivotal for miR-451-driven erythroid maturation. These studies define a new genetic pathway promoting erythroid maturation (mnr/miR-451/gata2) and provide a rare example of partial rescue of a mutant phenotype solely by miRNA overexpression.
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