microRNAs: Key Players in Hematopoiesis

Effects of miR‑210‑3p on the erythroid differentiation of K562 cells under hypoxia

GATA binding protein 1 (GATA-1) is one of the most important hematopoietic transcription factors in the production of blood cells, such as platelets, eosinophils, mast cells and erythrocytes. GATA-1 regulates the participation of microRNA (miRNAs/miRs) in erythroid differentiation under normoxia. However, GATA-1 expression and the regulation of miR-210-3p in the context of erythroid differentiation under hypoxia remain unknown. The present study examined the expression levels of GATA-1 and miR-210-3p in the model of erythroid differentiation in K562 cells under hypoxia, and determined the effects of GATA-1, miR-210-3p and SMAD2 on erythroid differentiation through lentivirus transfection experiments. The present study detected increased GATA-1 expression under hypoxia. Moreover, miR-210-3p was identified as a positive regulator of erythroid differentiation, which was upregulated both during erythroid differentiation and in GATA-1 overexpression experiments under hypoxia. Importantly, in the K562 cell model of erythroid differentiation under hypoxia, miR-210-3p was upregulated in a GATA-1-dependent manner. Using a double luciferase reporter assay, miR-210-3p was identified as a downstream target of GATA-1-mediated regulation of erythropoiesis. Gain- or loss-of-function analysis of miR-210-3p identified its importance in erythroid differentiation. Furthermore, it was found that SMAD2 may be a downstream target gene for miR-210-3p. Bioinformatics predictions suggested that SMAD2 mediated miR-210-3p-induced regulation of erythroid differentiation. Collectively, the present study provides novel insights into the miRNA regulation of erythroid differentiation.

Megakaryoblastic leukemia: a study on novel role of clinically significant long non-coding RNA signatures in megakaryocyte development during treatment with phorbol ester

Acute megakaryocytic leukemia (AMKL) is one of the rarest sub-types of acute myeloid leukemia (AML). AMKL is characterized by high proliferation of megakaryoblasts and myelofibrosis of bone marrow, this disease is also associated with poor prognosis. Previous analyses have reported that the human megakaryoblastic cells can be differentiated into cells with megakaryocyte (MK)-like characteristics by phorbol 12-myristate 13-acetate (PMA). However, little is known about the mechanism responsible for regulating this differentiation process. We performed long non-coding RNA (lncRNA) profiling to investigate the differently expressed lncRNAs in megakaryocyte blast cells treated with and without PMA and examined those that may be responsible for the PMA-induced differentiation of megakaryoblasts into MKs. We found 30 out of 90 lncRNA signatures to be differentially expressed after PMA treatment of megakaryoblast cells, including the highly expressed JPX lncRNA. Further, in silico lncRNA-miRNA and miRNA-mRNA interaction analysis revealed that the JPX is likely involved in unblocking the expression of TGF-β receptor (TGF-βR) by sponging oncogenic miRNAs (miR-9-5p, miR-17-5p, and miR-106-5p) during MK differentiation. Further, we report the activation of TGF-βR-induced non-canonical ERK1/2 and PI3K/AKT pathways during PMA-induced MK differentiation and ploidy development. The present study demonstrates that TGF-βR-induced non-canonical ERK1/2 and PI3K/AKT pathways are associated with PMA-induced MK differentiation and ploidy development; in this molecular mechanism, JPX lncRNA could act as a decoy for miR-9-5p, miR-17-5p, and miR-106-5p, titrating them away from TGF-βR mRNAs. Importantly, this study reveals the activation of ERK1/2 and PI3K/AKT pathway in PMA-induced Dami cell differentiation into MK. The identified differentially expressed lncRNA signatures may facilitate further study of the detailed molecular mechanisms associated with MK development. Thus, our data provide numerous targets with therapeutic potential for the modulation of the differentiation of megakaryoblastic cells in AMKL.

Differential miRNA expression analysis during late stage terminal hindgut development in fetal rats

BACKGROUND

Terminal hindgut deformity is the leading digestive tract malformation, however, the etiology and pathogenesis remained unknown. To date, gene expression abnormalities were considered the primary cause of these diseases. miRNAs have been found to play an important role in regulating the expression of genes.

METHODS

A total of 24 pregnant rats were randomly divided into two groups. The experimental group (n=12) received 1% ethylenethiourea (125mg/kg) by gavage on gestational day 11, while the control group (n=12) received the same volume of distilled water. From each group, fetal rats were obtained by cesarean section on gestational day 16. For the extraction of total RNA, 1 cm rectum samples were obtained from four fetal rats that had similar weights. Chip hybridization was conducted after poly(A) and biotin were added to the RNA samples, and this was followed by washing, dyeing, and scanning of the chip. Differences identified in the miRNA expression profiles and the target gene analysis results were further analyzed to identify potential regulators of terminal hindgut development.

RESULTS

Compared with the control group, 111 miRNAs expressed in the terminal hindgut of the experimental group were up-regulated on gestational day 16, while 117 miRNAs were down-regulated. The ten miRNAs with the greatest differential expression profiles between the experimental and control samples were selected for target gene prediction, pathway analysis, and gene ontology analysis. A subset of these miRNAs was found to be closely related to rat fetus terminal hindgut growth and development. In addition, target gene analysis showed that miR-193 may have an important role in regulating a key gene in anorectal development, Hoxd13. This role was confirmed in a dual luciferase reporter assay when miR-193 was able to inhibit expression of a reporter gene under the control of the 3' untranslated region of the Hoxd13 gene in the human embryonic kidney cell line, 293T. Real-time PCR and Western blotting experiments further showed that the expression of Hoxd13 was significantly lower when miR-193 was highly expressed in rat intestinal epithelial cells. The differences in both sets of experiments were statistically significant compared with the negative control group (P<0.05).

CONCLUSION

These data support an important regulatory role for miRNAs in the expression of target genes during terminal hindgut development in fetal rats. In particular, miR-193-mediated inhibition of Hoxd13 was found to be significant in rat intestinal epithelial cells.

The Enigma of miRNA Regulation in Cancer

MicroRNAs (miRNAs or miRs) are small 19-22 nucleotide long, noncoding, single-stranded, and multifunctional RNAs that regulate a diverse assortment of gene and protein functions that impact on a vast network of pathways. Lin-4, a noncoding transcript discovered in 1993 and named miRNA, initiated the exploration of research into these intriguing molecules identified in almost all organisms. miRNAs interfere with translation or posttranscriptional regulation of their target gene and regulate multiple biological actions exerted by these target genes. In cancer, they function as both oncogenes and tumor suppressor genes displaying differential activity in various cellular contexts. Although the role of miRNAs on target gene functions has been extensively investigated, less is currently known about the upstream regulatory molecules that regulate miRNAs. This chapter focuses on the factors and processes involved in miRNA regulation.

The role of microRNAs in the pathogenesis of autoimmune diseases

MicroRNAs (miRNAs) are single-stranded, endogenous non-coding small RNAs, ranging from 18 to 25 nucleotides in length. Growing evidence suggests that miRNAs are essential in regulating gene expression, cell development, differentiation and function. Autoimmune diseases are a family of chronic systemic inflammatory diseases. Recent findings on miRNA expression profiles have been suggesting their role as biomarkers in autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis and Sjögren's syndrome. In this review, we summarize the characteristics of miRNAs and their functional role in the immune system and autoimmune diseases including systemic lupus erythematosus, primary Sjögren's syndrome, rheumatoid arthritis, systemic sclerosis, multiple sclerosis and psoriasis; moreover, we depict the advantages of miRNAs in modern diagnostics.

Elevation of Circulating miR-210-3p in High-Altitude Hypoxic Environment

Background: The induction of miR-210-3p, a master hypoxamir, is a consistent feature of the hypoxic response in both normal and malignant cells. However, whether miR-210-3p acts as a circulating factor in response to a hypoxic environment remains unknown. The current study aimed to examine the effect of a high-altitude hypoxic environment on circulating miR-210-3p.

Methods: We examined and compared the levels of miR-210-3p using TaqMan-based qRT-PCR in both peripheral blood cells and plasma from 84 ethnic Chinese Tibetans residing at 3560 m, 46 newly arrived migrant Han Chinese (Tibet Han) and 82 Han Chinese residing at 8.9 m (Nanjing Han). Furthermore, we analyzed the correlations of miR-210-3p with hematological indices.

Results: The relative concentrations of miR-210-3p to internal reference U6 in blood cells were significantly higher in the Tibet Han group (1.01 ± 0.11, P < 0.001) and in the Tibetan group (1.17 ± 0.09, P < 0.001) than in the Nanjing Han group (0.51 ± 0.04). The absolute concentrations of plasma miR-210-3p were also markedly elevated in the Tibet Han group (503.54 ± 42.95 fmol/L, P = 0.004) and in the Tibetan group (557.78 ± 39.84 fmol/L, P < 0.001) compared to the Nanjing Han group (358.39 ± 16.16 fmol/L). However, in both blood cells and plasma, miR-210-3p levels were not significantly different between the Tibet Han group and the Tibetan group (P = 0.280, P = 0.620, respectively). Plasma miR-210-3p concentrations were positively correlated with miR-210-3p levels in blood cells (r = 0.192, P = 0.005). Furthermore, miR-210-3p levels in both blood cells and plasma showed strong positive correlations with red blood cell counts and hemoglobin and hematocrit values.

Conclusion: These data demonstrated, for the first time, that miR-210-3p might act as a circulating factor in response to hypoxic environments and could be associated with human adaptation to life at high altitudes.