Conditional Expression of C/EBPα in Mice Reveals Developmental Plasticity of Lymphoid and Erythroid/ Megakaryocyte Precursors in Vivo.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 671-671 ◽  
Author(s):  
Yumi Fukuchi ◽  
Fumi Shibata ◽  
Miyuki Ito ◽  
Yuko Goto-Koshino ◽  
Yusuke Sotomaru ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Developmental Plasticity ◽  
Specific Binding ◽  
Critical Role ◽  
Ectopic Expression ◽  
Pcr Analysis ◽  
Lineage Specification ◽  
Myeloid Lineage ◽  
Conditional Expression

Abstract CCAAT/ enhancer binding protein α (C/EBP α) is a member of the bZIP family of transcription factors that plays a critical role for early myeloid differentiation. C/EBP α knockout mice showed a complete differentiation block at myeloblast stage in hematopoietic system, and mature neutrophils and eosinophils are absent in the peripheral blood. Lineage specification in developmental tree of hematopoiesis is generally determined by a lineage specific transcription factors such as C/EBP α and GATA-1 that allow commitment to the specific lineage with simultaneous extinction of their capacity to differentiate into the other ones. However, recent evidences shown by the ectopic expression of above transcription factors unveiled the unexpected developmental plasticity of various progenitors such as MEP (erythroid/ megakaryocyte progenitor) and CLP (common lymphoid progenitor). GATA-1 is reported to convert CLP and CMP (common myeloid progenitor) into erythroid/ megakaryocyte lineage, however, the effect of C/EBP α on MEP and CLP is still unlcear. In order to investigate the role of C/EBP α in the various aspect of hematopoietic differentiation, especially its effect on the lineage specification at different stages of differentiation in vivo, we generated transgenic mice expressing inducible form of C/EBP α (C/EBP α-ER) under H-2K promoter (C/EBP α-ER Tg). In these mice, C/EBP α activity can be induced conditionally by 4-hydroxy tamoxifen (4-HT) in all hematopoietic cells. As expected, C/EBP α-ER was expressed in almost all hematopoietic tissues including bone marrow, spleen and thymus in these mice. Gel shift analysis revealed that C/EBP α-ER was activated by 4-HT, and showed specific binding to C/EBP-specific oligonucleotide in these tissues. Next we tested differentiation plasticity of erythroid and lymphoid progenitors by ectopically inducing C/EBP α-ER activity in these cells. We sorted MEP and CLP by FACS from C/EBP α-ER Tg and examined their clonogenic activities in the presence or absence of 4-HT. In the absence of 4-HT, MEP and CLP exclusively formed erythroid/ megakaryocyte and lymphoid colonies, respectively, as previously reported. Surprisingly however, these cells dramatically changed their fate of differentiation and formed significant numbers of granulocyte/ macrophage (GM) colonies in the presence of 4-HT, indicating that ectopic activation of C/EBP α-ER activity skewed their differentiation pathways to myeloid lineage. Cytospin preparation of the colonies and RT-PCR analysis revealed that these were accompanied by the morphological differentiation to granulocytes/ macrophages, and upregulation of myeloid-specific genes at mRNA level. These results indicate that MEP and CLP are not fully committed to either erythroid/ megakaryocyte or lymphoid lineage, and possess differentiation plasticity that can be redirected to myeloid lineage.

scholarly journals CircDUSP16 promotes the tumorigenesis and invasion of gastric cancer by sponging miR-145-5p

2019 ◽  
Vol 23 (3) ◽  
pp. 437-448 ◽  
Author(s):  
Zizhen Zhang ◽  
Chaojie Wang ◽  
Yeqian Zhang ◽  
Site Yu ◽  
Gang Zhao ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Specific Binding ◽  
Critical Role ◽  
Ectopic Expression ◽  
Luciferase Reporter ◽  
Circular Rnas ◽  
Poor Survival ◽  
Data Set

Abstract Background Circular RNAs (circRNAs) as a novel subgroup of non-coding RNAs act a critical role in the pathogenesis of gastric cancer (GC). However, the underlying mechanisms by which hsa_circ_0003855 (circDUSP16) contributes to GC are still undocumented. Materials The differentially expressed circRNAs were identified by GEO database. The association of circDUSP16 or miR-145-5p expression with clinicopathological features and prognosis in GC patients was analyzed by FISH and TCGA-seq data set. Loss- and gain-of-function experiments as well as a xenograft tumor model were performed to assess the role of circDUSP16 in GC cells. circDUSP16-specific binding with miR-145-5p was confirmed by bioinformatic analysis, luciferase reporter, and RNA immunoprecipitation assays. Results The expression levels of circDUSP16 were markedly increased in GC tissue samples and acted as an independent prognostic factor of poor survival in patients with GC. Knockdown of circDUSP16 repressed the cell viability, colony formation, and invasive potential in vitro and in vivo, but ectopic expression of circDUSP16 reversed these effects. Moreover, circDUSP16 possessed a co-localization with miR-145-5p in the cytoplasm, and acted as a sponge of miR-145-5p, which attenuated circDUSP16-induced tumor-promoting effects and IVNS1ABP expression in GC cells. MiR-145-5p had a negative correlation with circDUSP16 expression and its low expression was associated with poor survival in GC patients. Conclusions CircDUSP16 facilitates the tumorigenesis and invasion of GC cells by sponging miR-145-5p, and may provide a novel therapeutic target for GC.

scholarly journals MLL3/MLL4-Associated PAGR1 Regulates Adipogenesis by Controlling Induction of C/EBPβ and C/EBPδ

2020 ◽  
Vol 40 (17) ◽  
Author(s):  
Ji-Eun Lee ◽  
Young-Wook Cho ◽  
Chu-Xia Deng ◽  
Kai Ge
Keyword(s):  
Transcription Factors ◽  
Muscle Development ◽  
Critical Role ◽  
Ectopic Expression ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Histone Methyltransferases ◽  
Brown Adipose ◽  
Phosphorylated Creb

ABSTRACT Transcription factors C/EBPβ and C/EBPδ are induced within hours after initiation of adipogenesis in culture. They directly promote the expression of master adipogenic transcription factors peroxisome proliferator-activated receptor γ (PPARγ) and C/EBPα and are required for adipogenesis in vivo. However, the mechanism that controls the induction of C/EBPβ and C/EBPδ remains elusive. We previously showed that histone methyltransferases MLL3/MLL4 and associated PTIP are required for the induction of PPARγ and C/EBPα during adipogenesis. Here, we show MLL3/MLL4/PTIP-associated protein PAGR1 (also known as PA1) cooperates with phosphorylated CREB and ligand-activated glucocorticoid receptor to directly control the induction of C/EBPβ and C/EBPδ in the early phase of adipogenesis. Deletion of Pagr1 in white and brown preadipocytes prevents the induction of C/EBPβ and C/EBPδ and leads to severe defects in adipogenesis. Adipogenesis defects in PAGR1-deficient cells can be rescued by the ectopic expression of C/EBPβ or PPARγ. Finally, the deletion of Pagr1 in Myf5+ precursor cells impairs brown adipose tissue and muscle development. Thus, by controlling the induction of C/EBPβ and C/EBPδ, PAGR1 plays a critical role in adipogenesis.

scholarly journals Single molecule tracking of Ace1p in Saccharomyces cerevisiae defines a characteristic residence time for non-specific interactions of transcription factors with chromatin

2016 ◽  
Vol 44 (21) ◽  
pp. e160-e160 ◽  
Author(s):  
David A Ball ◽  
Gunjan D Mehta ◽  
Ronit Salomon-Kent ◽  
Davide Mazza ◽  
Tatsuya Morisaki ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Residence Time ◽  
Single Molecule ◽  
Specific Binding ◽  
Underlying Mechanism ◽  
Specific Interactions ◽  
Single Molecule Tracking ◽  
Reliable Performance ◽  
Transient Interactions

Abstract In vivo single molecule tracking has recently developed into a powerful technique for measuring and understanding the transient interactions of transcription factors (TF) with their chromatin response elements. However, this method still lacks a solid foundation for distinguishing between specific and non-specific interactions. To address this issue, we took advantage of the power of molecular genetics of yeast. Yeast TF Ace1p has only five specific sites in the genome and thus serves as a benchmark to distinguish specific from non-specific binding. Here, we show that the estimated residence time of the short-residence molecules is essentially the same for Hht1p, Ace1p and Hsf1p, equaling 0.12–0.32 s. These three DNA-binding proteins are very different in their structure, function and intracellular concentration. This suggests that (i) short-residence molecules are bound to DNA non-specifically, and (ii) that non-specific binding shares common characteristics between vastly different DNA-bound proteins and thus may have a common underlying mechanism. We develop new and robust procedure for evaluation of adverse effects of labeling, and new quantitative analysis procedures that significantly improve residence time measurements by accounting for fluorophore blinking. Our results provide a framework for the reliable performance and analysis of single molecule TF experiments in yeast.

MicroRNAs: Crucial Players in the Differentiation of Human Pluripotent and Multipotent Stem Cells into Functional Hepatocyte-Like Cells

2021 ◽  
Vol 16 ◽  
Author(s):  
Hao Xu ◽  
Liying Wu ◽  
Guojia Yuan ◽  
Xiaolu Liang ◽  
Xiaoguang Liu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Liver Disease ◽  
Pluripotent Stem Cells ◽  
Disease Modeling ◽  
Critical Role ◽  
Ectopic Expression ◽  
Embryonic Stem ◽  
The Body

: Hepatic disease negatively impacts liver function and metabolism. Primary human hepatocytes are the gold standard for the prediction and successful treatment of liver disease. However, the sources of hepatocytes for drug toxicity testing and disease modeling are limited. To overcome this issue, pluripotent stem cells (PSCs) have emerged as an alternative strategy for liver disease therapy. Human PSCs, including embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) can self-renew and give rise to all cells of the body. Human PSCs are attractive cell sources for regenerative medicine, tissue engineering, drug discovery, and developmental studies. Several recent studies have shown that mesenchymal stem cells (MSCs) can also differentiate (or trans-differentiate) into hepatocytes. Differentiation of human PSCs and MSCs into functional hepatocyte-like cells (HLCs) opens new strategies to study genetic diseases, hepatotoxicity, infection of hepatotropic viruses, and analyze hepatic biology. Numerous in vitro and in vivo differentiation protocols have been established to obtain human PSCs/MSCs-derived HLCs and mimic their characteristics. It was recently discovered that microRNAs (miRNAs) play a critical role in controlling the ectopic expression of transcription factors and governing the hepatocyte differentiation of human PSCs and MSCs. In this review, we focused on the role of miRNAs in the differentiation of human PSCs and MSCs into hepatocytes.

scholarly journals P0511ENHANCER AND SUPER-ENHANCER DYNAMICS IN REPAIR AFTER ISCHEMIC ACUTE KIDNEY INJURY

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Julia Wilflingseder ◽  
Michaela Willi ◽  
Hye Kyung Lee ◽  
Hannes Olauson ◽  
Jakub Jankowsky ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Transcription Factors ◽  
Small Molecule ◽  
Ischemia Reperfusion Injury ◽  
Specific Binding ◽  
Ischemia Reperfusion ◽  
Kidney Injury ◽  
Kidney Cortex ◽  
Super Enhancer

Abstract Background and Aims The endogenous repair process of the mammalian kidney allows rapid recovery after acute kidney injury (AKI) through robust proliferation of tubular epithelial cells. There is currently limited understanding of which transcriptional regulators activate these repair programs and how transcriptional dysregulation leads to maladaptive repair. Here we investigate the existence of enhancer dynamics in the regenerating mouse kidney. Method RNA-seq and ChIP-seq (H3K27ac, H3K4m3, BRD4, POL2 and selected transcription factors) were performed on samples from repairing kidney cortex 2 days after ischemia/reperfusion injury (IRI) to identify activated genes, transcription factors, enhancer and super-enhancers associated with kidney repair. Further we investigated the role of super-enhancer activation in kidney repair through pharmacological BET inhibition using the small molecule JQ1 in vitro and in acute kidney injury models in vivo. Results Response to kidney injury leads to genome-wide alteration in enhancer repertoire in-vivo. We identified 16,781 enhancer sites (H3K27ac and BRD4 positive, H3K4me3 negative binding) active in SHAM and IRI samples; 6,512 lost and 9,774 gained after IRI. The lost and gained enhancer sites can be annotated to 62% and 63% of down- and up-regulated transcripts at day 2 after kidney injury, respectively. Super-enhancer analysis revealed 164 lost and 216 gained super-enhancer sites at IRI day 2. 385 super-enhancers maintain activity before and after injury. ChIP-seq profiles of selected transcription factors based on motif analysis show specific binding at corresponding enhancer sites. We observed lost enhancer binding of HNF4A and GR mainly at kidney related enhancer elements. In contrast, STAT3 showed increased binding at injury induces enhancer elements. No dynamic was observed for STAT5. Both transcription factor groups show corresponding mRNA changes after injury. Pharmacological inhibition of enhancer and super-enhancer activity by BRD4 inhibition (JQ1: 50mg/kg/day) before IRI leads to suppression of 40% of injury-induced transcripts associated with cell cycle regulation and significantly increased mortality between days 2 and 3 after AKI. Conclusion This is the first demonstration of enhancer and super-enhancer function in the repairing kidney. In addition, our data call attention to potential caveats for use of small molecule inhibitors of BET proteins that are currently being tested in clinical trials in cancer patients who are at risk for AKI. Our analyses of enhancer dynamics after kidney injury in vivo have the potential to identify new targets for therapeutic intervention.

scholarly journals Binding of disparate transcriptional activators to nucleosomal DNA is inherently cooperative.

1995 ◽  
Vol 15 (3) ◽  
pp. 1405-1421 ◽  
Author(s):  
C C Adams ◽  
J L Workman
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Sites ◽  
Specific Binding ◽  
General Mechanism ◽  
Nf Kappa B ◽  
Nucleosomal Dna ◽  
Nucleosome Binding

To investigate mechanisms by which multiple transcription factors access complex promoters and enhancers within cellular chromatin, we have analyzed the binding of disparate factors to nucleosome cores. We used a purified in vitro system to analyze binding of four activator proteins, two GAL4 derivatives, USF, and NF-kappa B (KBF1), to reconstituted nucleosome cores containing different combinations of binding sites. Here we show that binding of any two or all three of these factors to nucleosomal DNA is inherently cooperative. Thus, the binuclear Zn clusters of GAL4, the helix-loop-helix/basic domains of USF, and the rel domain of NF-kappa B all participated in cooperative nucleosome binding, illustrating that this effect is not restricted to a particular DNA-binding domain. Simultaneous binding by two factors increased the affinity of individual factors for nucleosomal DNA by up to 2 orders of magnitude. Importantly, cooperative binding resulted in efficient nucleosome binding by factors (USF and NF-kappa B) which independently possess little nucleosome-binding ability. The participation of GAL4 derivatives in cooperative nucleosome binding required only DNA-binding and dimerization domains, indicating that disruption of histone-DNA contacts by factor binding was responsible for the increased affinity of additional factors. Cooperative nucleosome binding required sequence-specific binding of all transcription factors, appeared to have spatial constraints, and was independent of the orientation of the binding sites on the nucleosome. These results indicate that cooperative nucleosome binding is a general mechanism that may play a significant role in loading complex enhancer and promoter elements with multiple diverse factors in chromatin and contribute to the generation of threshold responses and transcriptional synergy by multiple activator sites in vivo.

46 EXPRESSION OF TRANSCRIPTION FACTORS SPECIFIC TO THE TROPHOBLAST LINEAGE IN MOUSE SOMATIC NUCLEAR TRANSFER EMBRYOS

2008 ◽  
Vol 20 (1) ◽  
pp. 103
Author(s):  
T. Mitani ◽  
M. Nishiwaki ◽  
M. Anzai ◽  
H. Kato ◽  
Y. Hosoi ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Real Time ◽  
Real Time Pcr ◽  
Nuclear Transfer ◽  
Ectopic Expression ◽  
Expression Level ◽  
Pcr Analysis ◽  
Cell Stage ◽  
Cdx2 Expression ◽  
Morula Stage

Somatic cell nuclear transfer (SCNT) embryos can develop at relatively high rates during the preimplantation period; however, most of these fail after implantation. Development of extraembryonic tissue is indispensable for normal embryonic development. Hence, an abnormality of trophoblast development might be a significant factor in post-implantation lethality of SCNT embryos. A transcription factor, caudal-related homeobox 2 (Cdx2), appears to be involved in the segregation of ICM and trophectoderm (TE) in preimplantation embryos (Niwa et al. 2005 Cell 123, 917–929). Both Cdx2 and Oct3/4 are expressed in all cells at the morula stage, and then Cdx2 expression becomes restricted to the TE and Oct3/4 to the ICM as the blastocyst develops. Mouse embryos deficient in Cdx2 are able to develop to normal blastocysts but die soon after implantation, probably because of defects in the TE lineage. Moreover, dysplasia of the spongiotrophoblast layer might attribute to an abnormality of Tpbpa expression in mouse SCNT embryos (Wakisaka-Saito et al. 2006 Biochem. Biophys. Res. Commun. 349, 106–114). In this study, we examined the expression profiles of transcription factors implicated in trophoblast development in mouse SCNT embryos and intracytoplasmic sperm injection (ICSI) embryos by immunohistochemistry and real-time PCR analysis. SCNT embryos were produced according to the method reported previously (Wakayama et al. 1998 Nature 394, 369–374). In brief, B6D2F1 and B6C3F1 female mice were used for the collection of recipient oocytes and donor cells, respectively. After nuclear transfer, the oocytes were activated and cultured in KSOM to the morula and blastocyst stages. Immunohistochemical analysis demonstrated that in ICSI embryos Cdx2 was only partially expressed at the 8-cell stage but completely in early morulae. In contrast, in SCNT embryos, it was absent at the 8-cell stage and appeared partially at the early morula stage. Thereafter, Cdx2 expression became restricted to the TE cells in both the ICSI and the SCNT blastocysts. However, ectopic expression of Oct3/4 was observed in the TE cells of SCNT, but not in ICSI blastocysts. Real-time PCR analysis showed that at the 8-cell stage, Cdx2 was expressed in ICSI but not in SCNT embryos. In addition, the expression level of Cdx2 in SCNT embryos at the blastocyst stage was only half that in ICSI embryos (P < 0.05). However, there was no significant difference in expression level of Oct3/4 between ICSI and SCNT embryos. Eomesodermin (Eomes) is also implicated in trophoblast development and its expression depends on Cdx2, BMP4, and FGF4. In SCNT embryos, the expression level of Eomes was also only half that in ICSI embryos. These results indicate that the delayed expression of Cdx2 in SCNT embryos may lead to the ectopic expression of Oct3/4 in blastocysts and, along with the limited expression of Cdx2 and Eomes, may contribute to disorders in the function of the trophoblast lineage for normal placental development. This work was supported by a Grant-in-Aid for the 21st Century Center of Excellence Program of the MEXT, Japan, and by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science.

scholarly journals lncRNA MEG3 Suppresses the Tumorigenesis of Hemangioma by Sponging miR-494 and Regulating PTEN/ PI3K/AKT Pathway

2018 ◽  
Vol 51 (6) ◽  
pp. 2872-2886 ◽  
Author(s):  
Yuxin Dai ◽  
Yongkun Wan ◽  
Mingke Qiu ◽  
Shuqing Wang ◽  
Chang Pan ◽  
...  
Keyword(s):  
Negative Correlation ◽  
Colony Formation ◽  
Normal Skin ◽  
Ectopic Expression ◽  
Tumor Model ◽  
Bioinformatic Analysis ◽  
Akt Pathway ◽  
Pcr Analysis

Background/Aims: Dysregulation of long noncoding RNAs (lncRNAs) is associated with the proliferation and metastasis in a variety of cancers, of which lncRNA maternally expressed gene 3 (MEG3) has been indicated as a tumor suppressor in multiple malignancies. However, the underlying mechanisms by which MEG3 contributes to human hemangiomas (HAs) remain undetermined. Methods: qRT-PCR analysis was performed to examine the expression levels of MEG3 and VEGF in proliferating or involuting phase HAs. MTT, colony formation assay, flow cytometry analysis and a subcutaneous xenograft tumor model were conducted to assess the effects of MEG3 on the HAs tumorigenesis. The interaction between MEG3 and miRNAs or their downstream pathways was evidenced by bioinformatic analysis, luciferase report assays, RNA immunoprecipitation (RIP) assay. and Western blot analysis. Results: The expression of MEG3 was substantially decreased and had a negative correlation with VEGF expression in proliferating phase HAs, as compared with the involuting phase HAs and normal skin tissues. Ectopic expression of MEG3 suppressed cell proliferation, colony formation and induced cycle arrest in vitro and in vivo, followed by the downregulation of VEGF and cyclinD1, but knockdown of MEG3 reversed these effects. Furthermore, MEG3 was verified to act as a sponge of miR-494 in HAs cells, and miR-494 counteracted MEG3-caused anti-proliferative effects by regulating PTEN/PI3K/AKT pathway, and exhibited the negative correlation with MEG3 and PTEN expression in proliferating phase HAs. Conclusion: Our findings suggested that lncRNA MEG3 inhibited HAs tumorigenesis by sponging miR-494 and regulating PTEN/PI3K/AKT pathway.

scholarly journals Molecular signature of an ancient organizer regulated by Wnt/β-catenin signalling during primary body axis patterning in Hydra

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Puli Chandramouli Reddy ◽  
Akhila Gungi ◽  
Suyog Ubhe ◽  
Saurabh J. Pradhan ◽  
Amol Kolte ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Regulatory Network ◽  
Critical Role ◽  
Ectopic Expression ◽  
Wnt Signalling ◽  
Body Axis ◽  
Molecular Signature ◽  
Zebrafish Embryos ◽  
Primary Body ◽  
Animal Phyla

AbstractWnt/β-catenin signalling has been shown to play a critical role during head organizer formation in Hydra. Here, we characterized the Wnt signalling regulatory network involved in formation of the head organizer. We found that Wnt signalling regulates genes that are important in tissue morphogenesis. We identified that majority of transcription factors (TFs) regulated by Wnt/β-catenin signalling belong to the homeodomain and forkhead families. Silencing of Margin, one of the Wnt regulated homeodomain TFs, results in loss of the ectopic tentacle phenotype typically seen upon activation of Wnt signalling. Furthermore, we show that the Margin promoter is directly bound and regulated by β-catenin. Ectopic expression of Margin in zebrafish embryos results in body axis abnormalities suggesting that Margin plays a role in axis patterning. Our findings suggest that homeobox TFs came under the regulatory umbrella of Wnt/β-catenin signalling presumably resulting in the evolution of primary body axis in animal phyla.

scholarly journals Circular RNA_CNST Promotes the Tumorigenesis of Osteosarcoma Cells by Sponging miR-421

2020 ◽  
Vol 29 ◽  
pp. 096368972092614
Author(s):  
Ji-Hai Wang ◽  
Xue-Jian Wu ◽  
Yong-Zhuang Duan ◽  
Feng Li
Keyword(s):  
Colony Formation ◽  
Specific Binding ◽  
Tumor Model ◽  
Gene Expression Omnibus ◽  
Pcr Analysis ◽  
Circular Rnas ◽  
Xenograft Tumor ◽  
Potential Biomarker

Circular RNAs (circRNAs) act crucial roles in the progression of multiple malignancies including osteosarcoma (OS). But, the underlying mechanisms by which hsa_circ_0017311 (circCNST) contributes to the tumorigenesis of OS remain poorly understood. Our present study aimed to explore the role and mechanisms of circCNST in OS tumorigenesis. The differentially expressed circRNAs were identified by the Gene Expression Omnibus database. The association of circCNST with clinicopathological features and prognosis in patients with OS was analyzed by RNA fluorescence in situ hybridization (FISH) and quantitative real-time polymerase chain reaction (PCR) analysis. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation assays, and a xenograft tumor model were conducted to assess the role of circCNST in OS cells in vitro and in vivo. CircCNST-specific binding with miR-421 was confirmed by FISH, luciferase gene report, and RNA immunoprecipitation assays. As a result, we found that the expression levels of circCNST were dramatically increased in OS tissues and cell lines as compared with the adjacent normal tissues, and it was associated with tumor size and poor survival in OS patients. Knockdown of circCNST repressed cell viability, colony formation, and xenograft tumor growth, while restored expression of circCNST reversed these effects. Furthermore, circCNST was colocalized with miR-421 in the cytoplasm and acted as a sponge of miR-421, which attenuated circCNST-induced proliferation-promoting effects in OS cells by targeting SLC25A3. In conclusion, our findings demonstrate that circCNST promotes the tumorigenesis of OS cells by sponging miR-421, and provides a potential biomarker for patients with OS.

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