| Hematopoiesis is an important physiological process through all the life. It involves the self-renewal and commitment of hematopoietic stem cells (HSCs) to various lineages and further differentiation and development of the committed progenitors to mature cells, and the whole process is under restrict control of the regulatory network in cells. Once the abnormalities in differentiation pathway appear, it will lead to hematopoietic diseases and leukemia genesis.Differentiation of monocytes and granulocytes (narrow myeloid differentiation) is an important branch of hematopoiesis, which is under the control of a complex network of cytokins and transcription factors, such as G-CSF, GM-CSF, M-CSF and the transcription factor PU.1 and C/EBPa. Although many factors have been identified, the regulatory network of myeloid differentiation is still incomplete. MicroRNAs that have been extensively investigated recently, were also identified as crucial regulators in this process.MicroRNAs (miRNAs) are～22 nucleotides (nt) non-protein-coding RNAs that usually negtively regulate a variety of gene expression at post transcriptional level through binding to mRNA 3’untranslated regions (3’UTR) in a sequence specific manner and result in translation repression or degradation of the target mRNAs in eukaryotic cells. The analysis of miRNAs’ expression and function has unraveled their important regulatory role in various life events such as cell cycle, apoptosis, and differentiation, and their involvements in various diseases.Abnormal proliferation, apoptosis repression and differentiation blockage of hematopoietic stem/progenitor population have been characterized to be the main reasons leading to acute myeloid leukemia (AML). Previous studies showed that miR-29a and miR-142-3p could function as tumor suppressors in leukemogenesis, and have been shown to be important regulators of myeloid differentiation and acute myeloid leukemia.Based on this, we intended to analyze the global gene expression pattern of HL-60 cells overexpressed miR-29a/miR-142-3p and induced by PMA/ATRA respectively to understand the regulatory network of myeloid differentiation promoted by miR-29a/miR-142-3p deeply. We also aimed to identify the new target genes of miR-29a during myeloid differentiation. Firstly, miR-29a and miR-142-3p was overexpressed in HL-60 cells by transfecting miRNA mimic meanwhile HL-60 cells were also induced towards mononcyte and granulocyte differentiation using PMA and ATRA respectively. May-Grunwald-Giemsa staining shown that HL-60 cells were induced towards mononcyte and granulocyte differentiation using PMA and ATRA respectively with success. Four groups of gene expression profile of the above cells were obtained by microarray and analyzed for their similarities. Genes which possessed similar expression pattern were further analyzed by GO clustering and Genetic correlation function using DAVID and GeneMANIA. The results shown that many differential expressed genes during ATRA/PMA induced myeloid differentiation or in the cells with miR-29a/miR-142-3p overexpression were similar. Significantly enriched genes in GO analysis which also possessed similar expression patterns were almost associated with cell differentiation. The above results suggested that miR-29a and miR-142-3p regulated the activity of their targets, triggered global gene expression change to make it closer to that during myeloid differentiation and then promoted myeloid differentiation. Utilizing PicTar and TargetScan, we predicted new targets of miR-29a which were also verified by double-luciferase reporter assay. As a result, ZBTB5, CaMKK2, SUV420H2, TRIB2 and CANX were identified to be new targets of miR-29a and may play important roles in myeloid differentiation promoted by miR-29a. In conclusion, this study revealed the global gene expression change triggered by miR-29a/miR-142-3p and found different pathways and target genes in myeloid differentiation promoted by miR-29a/miR-142-3p. |
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