BioProject

MiRNAs have the potential to regulate cellular differentiation programs. However, miRNA-deficiency in primary hematopoietic stem cells (HSCs) results in HSC depletion in mice, leaving the question of whether miRNAs play a role in early-lineage decisions unanswered. More...

MiRNAs have the potential to regulate cellular differentiation programs. However, miRNA-deficiency in primary hematopoietic stem cells (HSCs) results in HSC depletion in mice, leaving the question of whether miRNAs play a role in early-lineage decisions unanswered. To address this issue, we deleted Dicer1, which encodes an essential RNaseIII enzyme for miRNA biogenesis, in murine CCAAT/enhancer-binding protein alpha (C/EBPA)-positive myeloid-committed progenitors in vivo. In contrast to the results in HSCs, we found that miRNA depletion affected neither the number of myeloid progenitors nor the percentage of C/EBPA-positive progenitor cells. Analysis of gene-expression profiles from wild type and Dicer1-deficient granulocyte-macrophage progenitors (GMPs) revealed that 20 miRNA families were active in GMPs. Of the derepressed miRNA targets in Dicer1-null GMPs, 27% are normally exclusively expressed in HSCs or are specific for multi-potent progenitors and erythropoiesis, indicating an altered gene-expression landscape. Dicer1-deficient GMPs were defective in myeloid development in vitro and exhibited an increased replating capacity, indicating a regained self-renewal potential of these cells. In mice, Dicer1 deletion blocked monocytic differentiation, depleted macrophages and caused myeloid dysplasia with morphological features of Pelger-Huët anomaly. These results provide evidence for a miRNA-controlled switch for a cellular program of self-renewal and expansion towards myeloid differentiation in GMPs. Overall design: To generate Cebpa-Cre;R26-LSL-Eyfp;Dicer1wt/fl/Dicer1fl/fl mice, we crossed mice that contain floxed Dicer1 alleles (Dicer1fl) with Cebpa-Cre;R26-LSL-Eyfp reporter mice 2. Fetal livers were obtained on embryonic day (E) 13.5. Routine genotyping of Dicer1; Cebpa-Cre;R26-LSL-Eyfp mice was performed by PCR assays of DNA from tail or toe biopsies. For transplantation, 6 to 8-week-old recipient mice (C57Bl/6, Jackson Laboratories) were irradiated (8.5 Gy) and tail-vein injected with fetal liver single-cell suspensions. Typically, cells from each fetal liver were transplanted into two recipient mice. Hematopoietic tissues were analyzed 6-10 weeks post transplantation. EYFP positive GMPs from the bone marrow of Dicer wt control (n=3), Dicer -/wt (n=3 and Dicer fl/fl (n=3) were sorted and analyzed for gene expression profiles. Less...