Submitted November 17, 2008
Accepted February 17, 2009
Gfi1 regulates miR-21 and miR-196b to control myelopoiesis
Chinavenmeni S. Velu, Avinash M. Baktula, and H. Leighton Grimes*
Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
* Corresponding author; email: lee.grimes{at}cchmc.org.
The zinc finger protein Growth factor independent-1 (Gfi1) is a transcriptional repressor that is critically required for normal granulocytic differentiation. GFI1 loss-of-function mutations are found in some patients with severe congenital neutropenia (SCN). The SCN-associated GFI1-mutant proteins act as dominant negatives to block granulopoiesis through selective deregulation of a subset of GFI1 target genes. Here we show that Gfi1 is a master regulator of microRNAs, and that deregulated expression of these microRNAs recapitulates a Gfi1 loss-of-function block to G-CSF stimulated granulopoiesis. Specifically, bone marrow cells from a GFI1-mutant SCN patient and Gfi1-/- mice display deregulated expression of miR-21 and miR-196B expresion. Flow cytometric analysis and colony assays reveal that the overexpression or depletion of either miR induces changes in myeloid development. However, co-expression of miR-21 and miR-196b (as seen in Gfi1-/- mice and a GFI1N382S SCN patient) completely blocks G-CSF-induced granulopoiesis. Thus, our results not only identify microRNAs whose regulation is required during myelopoiesis, but also provide an example of synergy in microRNA biological activity and illustrate potential mechanisms underlying SCN disease pathogenesis.
