GATA-2 inhibits transforming growth factor-β signaling pathway through interaction with Smad4

Effect of strontium on transcription factors identified by transcriptome analyses of bovine ruminal epithelial cells

BACKGROUND

Strontium (Sr) has similar physicochemical properties as calcium (Ca) and is often used to evaluate the absorption of this mineral. Because the major route of Ca absorption in the bovine occurs in the rumen, it is essential to understand whether Sr impacts the ruminal epithelial cells and to what extent.

RESULTS

In the present study, RNA sequencing and assembled transcriptome assembly were used to identify transcription factors (TFs), screening and bioinformatics analysis in bovine ruminal epithelial cells treated with Sr. A total of 1405 TFs were identified and classified into 64 families based on an alignment of conserved domains. A total of 174 differently expressed TFs (DE-TFs) were increased and 52 DE-TFs were decreased; the biological process-epithelial cell differentiation was inhibited according to the GSEA-GO analysis of TFs; The GO analysis of DE-TFs was enriched in the DNA binding. Protein-protein interaction network (PPI) found 12 hubs, including SMAD4, SMAD2, SMAD3, SP1, GATA2, NR3C1, PPARG, FOXO1, MEF2A, NCOA2, LEF1, and ETS1, which verified genes expression levels by real-time PCR.

CONCLUSIONS

In this study, SMAD2, PPARG, LEF1, ETS1, GATA2, MEF2A, and NCOA2 are potential candidates that could be targeted by Sr to mediate cell proliferation and differentiation, as well as lipid metabolism. Hence, these results enhance the comprehension of Sr in the regulation of transcription factors and provide new insight into the study of Sr biological function in ruminant animals.

GATA2 co-opts TGFβ1/SMAD4 oncogenic signaling and inherited variants at 6q22 to modulate prostate cancer progression

BACKGROUND

Aberrant somatic genomic alteration including copy number amplification is a hallmark of cancer genomes. We previously profiled genomic landscapes of prostate cancer (PCa), yet the underlying causal genes with prognostic potential has not been defined. It remains unclear how a somatic genomic event cooperates with inherited germline variants contribute to cancer predisposition and progression.

METHODS

We applied integrated genomic and clinical data, experimental models and bioinformatic analysis to identify GATA2 as a highly prevalent metastasis-associated genomic amplification in PCa. Biological roles of GATA2 in PCa metastasis was determined in vitro and in vivo. Global chromatin co-occupancy and co-regulation of GATA2 and SMAD4 was investigated by coimmunoprecipitation, ChIP-seq and RNA-seq assays. Tumor cellular assays, qRT-PCR, western blot, ChIP, luciferase assays and CRISPR-Cas9 editing methods were performed to mechanistically understand the cooperation of GATA2 with SMAD4 in promoting TGFβ1 and AR signaling and mediating inherited PCa risk and progression.

RESULTS

In this study, by integrated genomics and experimental analysis, we identified GATA2 as a prevalent metastasis-associated genomic amplification to transcriptionally augment its own expression in PCa. Functional experiments demonstrated that GATA2 physically interacted and cooperated with SMAD4 for genome-wide chromatin co-occupancy and co-regulation of PCa genes and metastasis pathways like TGFβ signaling. Mechanistically, GATA2 was cooperative with SMAD4 to enhance TGFβ and AR signaling pathways, and activated the expression of TGFβ1 via directly binding to a distal enhancer of TGFβ1. Strinkingly, GATA2 and SMAD4 globally mediated inherited PCa risk and formed a transcriptional complex with HOXB13 at the PCa risk-associated rs339331/6q22 enhancer, leading to increased expression of the PCa susceptibility gene RFX6.

CONCLUSIONS

Our study prioritizes causal genomic amplification genes with prognostic values in PCa and reveals the pivotal roles of GATA2 in transcriptionally activating the expression of its own and TGFβ1, thereby co-opting to TGFβ1/SMAD4 signaling and RFX6 at 6q22 to modulate PCa predisposition and progression.

Red Blood Cells as Potential Repositories of MicroRNAs in the Circulatory System

The amount of erythrocyte-derived microRNAs (miRNAs) represents the majority of miRNAs expressed in whole blood. miR-451, miR-144, and miR-486, which are abundant in red blood cells (RBCs), are involved in the process of erythropoiesis and disease occurrence. Moreover, erythrocyte-derived miRNAs have been reported to be potential biomarkers of specific diseases. However, the function and underlying mechanisms of miRNAs derived from erythrocytes remain unclear. Based on a review of previously published literature, we discuss several possible pathways by which RBC miRNAs may function and propose that RBCs may serve as repositories of miRNAs in the circulatory system and participate in the regulation of gene expression mainly via the transfer of miRNAs from erythrocyte extracellular vesicles (EVs). In the whole blood, there are still other important cell types such as leukocytes and platelets harboring functional miRNAs, and hemolysis also exists, which limit the abundance of miRNAs as disease biomarkers, and thus, miRNA studies on RBCs may be impacted. In the future, the role of RBCs in the regulation of normal physiological functions of the body and the entire circulatory system under pathological states, if any, remains to be determined.

Smad4 gene silencing enhances the chemosensitivity of human lymphoma cells to adriamycin via inhibition of the activation of transforming growth factor β signaling pathway

There are diverse investigations focused on the therapies of lymphoma. Our research was taken to identify the effects of lentiviral-mediated Smad4 gene silencing on chemosensitivity of human lymphoma cells to adriamycin (ADM) via transforming growth factor β (TGFβ) signaling pathway. Raji/ADM cells were cultured and infected with lentiviral particles Smad4-short hairpin (shRNA) and control-shRNA. Then, the messenger RNA (mRNA) and protein levels of TGFβ signaling pathway-related factors (Smad4, Smad3, cyclinE, cyclinD1, and p21) in Raji/ADM cells were determined. The effect of Smad4-shRNA on cell viability, invasion and migration, and apoptosis were also detected. Compared with the Raji group, increased mRNA and protein levels of Smad4, Smad3, cyclinE, cyclinD1, enhanced cell proliferation, migration and invasion as well as decreased mRNA, and protein levels of p21 and cell apoptosis rate were found in the Raji/ADM and control-shRNA groups. However, Smad4 gene silencing resulted in decreased mRNA and protein levels of Smad4, Smad3, cyclinE, and cyclinD1 along with inhibited cell proliferation, migration and invasion but increased expression of p21 together with cell apoptosis. Collectively, Smad4 gene silencing can inhibit the activation of TGFβ signaling pathway, thereby enhancing the chemosensitivity of human lymphoma cells to ADM.

Bone marrow hematopoietic dysfunction in untreated chronic lymphocytic leukemia patients

The consequences of immune dysfunction in B-chronic lymphocytic leukemia (CLL) likely relate to the incidence of serious recurrent infections and second malignancies that plague CLL patients. The well-described immune abnormalities are not able to consistently explain these complications. Here, we report bone marrow (BM) hematopoietic dysfunction in early and late stage untreated CLL patients. Numbers of CD34⁺ BM hematopoietic progenitors responsive in standard colony-forming unit (CFU) assays, including CFU-GM/GEMM and CFU-E, were significantly reduced. Flow cytometry revealed corresponding reductions in frequencies of all hematopoietic stem and progenitor cell (HSPC) subsets assessed in CLL patient marrow. Consistent with the reduction in HSPCs, BM resident monocytes and natural killer cells were reduced, a deficiency recapitulated in blood. Finally, we report increases in protein levels of the transcriptional regulators HIF-1α, GATA-1, PU.1, and GATA-2 in CLL patient BM, providing molecular insight into the basis of HSPC dysfunction. Importantly, PU.1 and GATA-2 were rapidly increased when healthy HSPCs were exposed in vitro to TNFα, a cytokine constitutively produced by CLL B cells. Together, these findings reveal BM hematopoietic dysfunction in untreated CLL patients that provides new insight into the etiology of the complex immunodeficiency state in CLL.

Compound Astragalus and Salvia miltiorrhiza extract inhibits hepatocarcinogenesis via modulating TGF-β/TβR and Imp7/8

Compound Astragalus and Salvia miltiorrhiza extract (CASE) is a Chinese herbal formula consisting of astragalosides, astragalus polysaccharide and salvianolic acids extracted from Astragalus membranaceus and Salvia miltiorhiza. Previous studies by our group have demonstrated that CASE effectively suppresses diethylinitrosamine (DEN)-induced hepatocellular carcinoma (HCC) in rats via modulating transforming growth factor β/Mothers against decapentaplegic (TGFβ/Smad) signaling. To further elucidate the mechanism of CASE, the effects of CASE on TGF-β₁, the serine/threonine kinase receptors of TGF-β [TGF-β receptor type-I (TβRI) and TβRII] and karyopherins [Importin 7 (Imp7) and Imp8], which are crucial for TGF-β/Smad signaling in fibro-hepatocarcinogenesis, were assessed in the present study using in vivo (DEN-induced HCC in rats) and in vitro [TGF-β₁-stimulated rat myofibroblasts (MFBs) and HepG2 cells] models of fibro-hepatocarcinogenesis. Hematoxylin and eosin staining revealed that CASE may suppress inflammatory reactions and fibrosis in HCC as well as increasing the differentiation of HCC cells. Positive TGF-β₁ staining was increased in HCC nodule areas and in adjacent normal liver tissues in DEN-treated rats, while TβRI staining was increased only in normal adjacent liver tissues. The elevated expression of TGF-β₁, TβRI and TβRII was suppressed by CASE. CASE treatment also reduced glutathione S-transferase P 1 and Imp7/8 protein expression in fibro-hepatocarcinogenesis. In vitro experiments confirmed that CASE was able to decrease the expression of TβRI and TβRII in TGF-β₁-stimulated MFBs and HepG2 cells. These results indicate that the anti-HCC effect of CASE may be achieved by mediating TGF-β/TβR and Imp7/8 protein expression, suggesting that CASE has multiple targets in HCC treatment.

Matrix stiffness controls lymphatic vessel formation through regulation of a GATA2-dependent transcriptional program

Tissue and vessel wall stiffening alters endothelial cell properties and contributes to vascular dysfunction. However, whether extracellular matrix (ECM) stiffness impacts vascular development is not known. Here we show that matrix stiffness controls lymphatic vascular morphogenesis. Atomic force microscopy measurements in mouse embryos reveal that venous lymphatic endothelial cell (LEC) progenitors experience a decrease in substrate stiffness upon migration out of the cardinal vein, which induces a GATA2-dependent transcriptional program required to form the first lymphatic vessels. Transcriptome analysis shows that LECs grown on a soft matrix exhibit increased GATA2 expression and a GATA2-dependent upregulation of genes involved in cell migration and lymphangiogenesis, including VEGFR3. Analyses of mouse models demonstrate a cell-autonomous function of GATA2 in regulating LEC responsiveness to VEGF-C and in controlling LEC migration and sprouting in vivo. Our study thus uncovers a mechanism by which ECM stiffness dictates the migratory behavior of LECs during early lymphatic development.

A comprehensive joint analysis of the long and short RNA transcriptomes of human erythrocytes

Background

Human erythrocytes are terminally differentiated, anucleate cells long thought to lack RNAs. However, previous studies have shown the persistence of many small-sized RNAs in erythrocytes. To comprehensively define the erythrocyte transcriptome, we used high-throughput sequencing to identify both short (18–24 nt) and long (>200 nt) RNAs in mature erythrocytes.

Results

Analysis of the short RNA transcriptome with miRDeep identified 287 known and 72 putative novel microRNAs. Unexpectedly, we also uncover an extensive repertoire of long erythrocyte RNAs that encode many proteins critical for erythrocyte differentiation and function. Additionally, the erythrocyte long RNA transcriptome is significantly enriched in the erythroid progenitor transcriptome. Joint analysis of both short and long RNAs identified several loci with co-expression of both microRNAs and long RNAs spanning microRNA precursor regions. Within the miR-144/451 locus previously implicated in erythroid development, we observed unique co-expression of several primate-specific noncoding RNAs, including a lncRNA, and miR-4732-5p/-3p. We show that miR-4732-3p targets both SMAD2 and SMAD4, two critical components of the TGF-β pathway implicated in erythropoiesis. Furthermore, miR-4732-3p represses SMAD2/4-dependent TGF-β signaling, thereby promoting cell proliferation during erythroid differentiation.

Conclusions

Our study presents the most extensive profiling of erythrocyte RNAs to date, and describes primate-specific interactions between the key modulator miR-4732-3p and TGF-β signaling during human erythropoiesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2156-2) contains supplementary material, which is available to authorized users.

MAPK inhibitors modulate Smad2/3/4 complex cyto-nuclear translocation in myofibroblasts via Imp7/8 mediation

Mitogen-activated protein kinase (MAPK) pathway-dependent linker phosphorylation of Smad2/3 and subsequent formation of Smad2/3/4 complex and its nuclear translocation are crucial for dysregulated transforming growth factor beta (TGF)-β/Smad signaling in liver fibrosis. Abrogation of this critical step of TGF-β/Smad signaling leading to liver fibrosis could provide new insights for future therapy, but the mechanisms remain incompletely understood. In pursuit, we investigated the subcellular expression and nuclear trafficking of the rate limiting Smad2/3/4 complex in exogenous TGF-β1-stimulated myofibroblasts (MFBs) using three MAPK-specific inhibitors. Our results showed that exogenous TGF-β1 stimulation of MFBs produced both increased protein expression and nuclear translocation of phosphorylated (p)-Smad2C/L, oncogenic pSmad3L, Smad4, importin7/8 (Imp7/8), and plasminogen activator inhibitor (PAI)-1 (Protein and mRNA), while decreased Smad7 protein expression. However, the MAPK-specific inhibitors differentially reversed these observations; for instance, ERK-specific inhibitor blocked the expression and nuclear translocation of pSmad2C/L, while both JNK and p38-specific inhibitors blocked the expression and nuclear translocation of pSmad2C/L and oncogenic pSmad3L. The MAPK-specific inhibitors had no significant effect on the total protein expression of Smad4, but rather significantly blocked its nuclear translocation. All the MAPK-specific inhibitors restored Smad7 expression and also decreased Imp7/8 and PAI-1 (Protein and mRNA) expression. Evidently, the MAPK-specific inhibitors blocked Smad2/3/4 complex formation via restoration of inhibitory Smad7 expression and blockade of Smad3L phosphorylation, while they blocked nuclear translocation of Smad2/3/4 complex through inhibition of Imp7/8 leading to decreased PAI-1 (Protein and mRNA) expression.

Haematopoietic and immune defects associated with GATA2 mutation

Heterozygous familial or sporadic GATA2 mutations cause a multifaceted disorder, encompassing susceptibility to infection, pulmonary dysfunction, autoimmunity, lymphoedema and malignancy. Although often healthy in childhood, carriers of defective GATA2 alleles develop progressive loss of mononuclear cells (dendritic cells, monocytes, B and Natural Killer lymphocytes), elevated FLT3 ligand, and a 90% risk of clinical complications, including progression to myelodysplastic syndrome (MDS) by 60 years of age. Premature death may occur from childhood due to infection, pulmonary dysfunction, solid malignancy and MDS/acute myeloid leukaemia. GATA2 mutations include frameshifts, amino acid substitutions, insertions and deletions scattered throughout the gene but concentrated in the region encoding the two zinc finger domains. Mutations appear to cause haplo-insufficiency, which is known to impair haematopoietic stem cell survival in animal models. Management includes genetic counselling, prevention of infection, cancer surveillance, haematopoietic monitoring and, ultimately, stem cell transplantation upon the development of MDS or another life-threatening complication.