Chicken Ovalbumin Upstream Promoter-transcription Factor II Research Articles

COUP-TFII in Kidneys, from Embryos to Sick Adults.

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is an orphan nuclear hormone receptor of unknown ligands. This molecule has two interesting features: (1) it is a developmental gene, and (2) it is a potential hormone receptor. Here, we describe the possible roles of COUP-TFII in the organogenesis of the kidneys and protection from adult renal diseases, primarily in mouse models. COUP-TFII is highly expressed in embryos, including primordial kidneys, and is essential for the formation of metanephric mesenchyme and the survival of renal precursor cells. Although the expression levels of COUP-TFII are low and its functions are unknown in healthy adults, it serves as a reno-protectant molecule against acute kidney injury. These are good examples of how developmental genes exhibit novel functions in the etiology of adult diseases. We also discuss the ongoing research on the roles of COUP-TFII in podocyte development and diabetic kidney disease. In addition, the identification of potential ligands suggests that COUP-TFII might be a novel therapeutic target for renal diseases in the future.

Effect of selected bisphenol derivatives on nuclear receptor expression in ovarian cell line COV434.

Objectives. Bisphenol A (BPA), as an indispensable plastic additive, has also been proven as an endocrine disruptor associated with adverse health effects including impaired ovarian function and cancer. Due to the restrictions of its usage, several analogs have been employed to replace BPA. Although many studies revealed a harmfulness in the biological effects of BPA analogs, their specific targets remain largely unknown. Nuclear receptors (NRs) may be one of the most important targets of bisphenols. Therefore, in this study, our attention was directed to explore the effect of BPA and its analogs, AF and S, on the mRNA expression of selected NRs involved in the steroidogenic and carcinogenic pathways in the human granulosa cell line COV434. The NRs investigated included: thyroid hormone receptor α (THRA), peroxisome proliferator activating receptor β/δ (PPARD), retinoid X receptor α (RXRA), chicken ovalbumin upstream promoter-transcription factor II (COUPTFII), nuclear receptor-related protein 1 (NURR1), and liver receptor homolog-1 (LRH1).Methods. COV434 cells were treated with the bisphenols at the concentrations of 10-9 M, 10-7 M, and 10-5 M, and after 24 and 48 h, cell viability was monitored by the MTS assay and gene expressions were analyzed using RT-qPCR.Results. Bisphenol treatment did not alter the COV434 cell viability. After 24 h, the expression of neither of the NRs was changed. Likewise, after 48 h, the expression of the selected genes was not altered. However, both BPAF and BPS increased, at the highest concentration (10-5 M) used, the mRNA levels of both PPARD and NURR1 NRs after 48 h of the treatment. In the BPA-treated groups, no significant upregulation was observed.Conclusions. In the present study, the effect of bisphenols on COUP-TFII, Nurr1, and LRH-1 NRs was investigated for the first time. Although generally we did not observe that BPs provoked any alterations in the expression of the selected NRs in COV434 cells, at specific concentrations and time points they might alter mRNA expression of certain NRs (NURR1, PPARD).

Extracellular vesicle-associated VEGF-C promotes lymphangiogenesis and immune cells infiltration in endometriosis

Endometriosis is a highly prevalent gynecological disease with severe negative impacts on life quality and financial burden. Unfortunately, there is no cure for this disease, which highlights the need for further investigation about the pathophysiology of this disease to provide clues for developing novel therapeutic regimens. Herein, we identified that vascular endothelial growth factor (VEGF)-C, a potent lymphangiogenic factor, is up-regulated in endometriotic cells and contributes to increased lymphangiogenesis. Bioinformatic analysis and molecular biological characterization revealed that VEGF-C is negatively regulated by an orphan nuclear receptor, chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII). Further studies demonstrated that proinflammatory cytokines, via suppression of COUP-TFII level, induce VEGF-C overexpression. More importantly, we show that functional VEGF-C is transported by extracellular vesicles (EVs) to enhance the lymphangiogenic ability of lymphatic endothelial cells. Autotransplanted mouse model of endometriosis showed lenvatinib treatment abrogated the increased lymphatic vessels development in the endometriotic lesion, enlarged retroperitoneal lymph nodes, and immune cells infiltration, indicating that blocking VEGF-C signaling can reduce local chronic inflammation and concomitantly endometriosis development. Evaluation of EV-transmitted VEGF-C from patients' sera demonstrates it is a reliable noninvasive way for clinical diagnosis. Taken together, we identify the vicious cycle of inflammation, COUP-TFII, VEGF-C, and lymphangiogenesis in the endometriotic microenvironment, which opens up new horizons in understanding the pathophysiology of endometriosis. VEGF-C not only can serve as a diagnostic biomarker but also a molecular target for developing therapeutic regimens.

Augmented angiogenic transcription factor, SOX18, is associated with asthma exacerbation

Background Asthma characterized by airway hyperresponsiveness, inflammation, fibrosis, and angiogenesis. SRY-related HMG-box 18 (SOX18) is an important transcription factor involved in angiogenesis, tissue injury, wound-healing, and in embryonic cardiovascular and lymphatic vessels development. The role of angiogenic transcription factors, SOX18 and the related, prospero homeobox 1 (PROX1) and chicken ovalbumin upstream promoter transcription factor II (COUP-TFII), in asthma has had limited study. Objective In this study, we aimed to elucidate the role of SOX18 in the pathogenesis of bronchial asthma. Methods Plasma SOX18 protein was measured in control subjects, and subject with stable or exacerbated asthma. SOX18, PROX1, and COUP-TFII protein was measured by western blot, and immunohistochemistry in a murine model of ovalbumin-induced allergic asthma (OVA). SOX18, PROX1, and COUP-TFII protein was measured in lung human microvascular endothelial cells (HMVEC-L) and normal human bronchial epithelial (NHBE) cells treated with house dust mite (Der p1). Results Plasma SOX18 tended to be higher in subject with asthma compared to control subjects and increased more during exacerbation as compared to stable disease. In mice, OVA challenge lead to increased lung SOX18, PROX1, COUP-TFII, mucous gland hyperplasia and submucosal collagen. In NHBE cells, SOX18, PROX1 and COUP-TFII increased following Der p1 treatment. SOX18 protein increased in HMVEC-L following Der p1 treatment. Conclusion These results suggest that SOX18 may be involved in asthma pathogenesis and be associated with asthma exacerbation.

Recent progress on the role and molecular mechanism of chicken ovalbumin upstream promoter-transcription factor II in cancer.

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is an orphan receptor that regulates the expression of genes involved in development and homeostasis. COUP-TFII is also dysregulated in cancer, where it plays important roles in oncogenesis and malignant progression. Recent studies have also investigated altered microRNA-mediated regulation of COUP-TFII in cancer. Although many investigators have studied the expression and clinical significance of COUP-TFII in several cancer types, there remain many controversies regarding its role in these diseases. In this review, we will describe the functions and underlying molecular mechanisms of COUP-TFII in several cancers, especially colorectal, gastric, breast, and prostate cancer; additionally, we will briefly summarize what is known about microRNA-mediated regulation of COUP-TFII.

COUP-TFII Overexpression Inhibits Cell Proliferation and Invasion via Increased Expression of p53 and PTEN and Decreased Akt Phosphorylation in Human Colorectal Cancer SNU-C4 Cells.

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) plays an important role in cancer. We examined the effect of COUP-TFII overexpression on the proliferation and invasion of the human colorectal cancer SNU-C4 cells. SNU-C4 cells were stably transfected with COUP-TFII expression plasmid to overexpress COUP-TFII (COUP-TFII-SNU-C4 cells). Cell proliferation, colony-forming ability and transwell invasion assays were performed. To elucidate the underlying molecular mechanism of COUP-TFII action, western blot analysis, p53 shRNA transfection, and Myr-Akt transfection were performed. Cell proliferation and colony-forming ability were significantly inhibited in COUP-TFII-SNU-C4 cells. Western blot analyses demonstrated that while the expression of p53 and PTEN was increased, the p-Akt levels were decreased in COUP-TFII-SNU-C4 cells. Knockdown of p53 partially restored the cell proliferation, but did not reverse the inhibition of invasion. Constitutive activation of Akt via Myr-Akt transfection reversed the inhibited cell proliferation and invasion by COUP-TFII. p53 is required for the inhibition of cell proliferation, and decreased phosphorylation of Akt may mediate the inhibition of cell proliferation and invasion by COUP-TFII.

COUP-TFII Knock-down Promotes Proliferation and Invasion in Colorectal Cancer Cells via Activation of Akt Pathway and Up-regulation of FOXC1.

The chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) regulates cancer cell proliferation and invasion via complex molecular mechanisms. We aimed to investigate whether COUP-TFII modulates proliferation and invasion of the colorectal adenocarcinoma cell line HT-29. HT-29 cells were stably tranfected with COUP-TFII shRNA plasmid to knock-down COUP-TFII (COUP-TFII shRNA-HT-29 cells). Cell proliferation, colony formation assay, invasion assay, microarray assays and western blot analyses were performed. Cell proliferation and invasion were significantly enhanced in COUP-TFII shRNA-HT-29 cells. The protein levels of forkhead box C1 (FOXC1), p-Akt, p-glycogen synthase kinase-3β (p-GSK-3β), and β-catenin, which are known to be involved in cell proliferation and invasion, were significantly increased in COUP-TFII shRNA-HT-29 cells. Akt inhibitor IV and dominant negative (DN)-Akt expression vector transfection reversed the increased proliferation and invasion, which was accompanied by decreased protein levels of p-Akt, p-GSK-3β, β-catenin and FOXC1. COUP-TFII knock-down promoted proliferation and invasion via activation of Akt/GSK-3β/β-catenin and up-regulation of FOXC1. Further studies on the molecular mechanism of interaction between β-catenin and FOXC1 expression may reveal novel target molecules for metastatic colorectal cancer therapy.

Increased COUP-TFII Expression Mediates the Differentiation Imbalance of Bone Marrow-Derived Mesenchymal Stem Cells in Femoral Head Osteonecrosis.

Objective Bone marrow-derived mesenchymal stem cells (BMSCs) have multilineage differentiation potential, which allows them to progress to osteogenesis, adipogenesis, and chondrogenesis. An imbalance of differentiation between osteogenesis and adipogenesis will result in pathologic conditions inside the bone. This type of imbalance is also one of the pathological findings in osteonecrosis of the femoral head (ONFH). Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) was previously reported to mediate the differentiation of mesenchymal stem cells. This study investigated the expression of the osteogenesis regulator Runx2, osteocalcin, the adipogenesis regulator PPARγ, and COUP-TFII in the femoral head tissue harvested from ONFH patients, and characterized the effect of COUP-TFII on the differentiation of primary BMSCs. MethodsThirty patients with ONFH were recruited and separated into 3 groups: the trauma-, steroid- and alcohol-induced ONFH groups (10 patients each). Bone specimens were harvested from patients who underwent hip arthroplasty, and another 10 specimens were harvested from femoral neck fracture patients as the control group. Expression of the osteogenesis regulator Runx2, osteocalcin, the adipogenesis regulator PPARγ, C/EBP-α, and COUP-TFII was analyzed by Western blotting. Primary bone marrow mesenchymal cells were harvested from ONFH cells treated with COUP-TFII RNA interference to evaluate the effect of COUP-TFII on MSCs. ResultsONFH patients had significantly increased expression of the adipogenesis regulator PPARγ and C/EBP-α and decreased expression of the osteogenesis regulator osteocalcin. ONFH bone tissue also revealed higher COUP-TFII expression. Immunohistochemical staining displayed strong COUP-TFII immunoreactivity adjacent to osteonecrotic trabecular bone. Increased COUP-TFII expression in the bone tissue correlated with increased PPARγ and decreased osteocalcin expression. Knockdown of COUP-TFII with siRNA in BMSCs reduced adipogenesis and increased osteogenesis in mesenchymal cells. ConclusionIncreased COUP-TFII expression mediates the imbalance of BMSC differentiation and progression to ONFH in patients. This study might reveal a new target in the treatment of ONFH.

Chicken ovalbumin upstream promoter-transcription factor II protects against cisplatin-induced acute kidney injury.

The chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) plays essential roles in organogenesis of embryos. Recently COUP-TFII is also implicated in several diseases in adults. Here we focus on the role of COUP-TFII in cisplatin-induced acute kidney injury (AKI). COUP-TFII was the most abundantly expressed in the kidney among organs. Male tamoxifen-inducible COUP-TFII-knockout mice or control mice were intraperitoneally treated with 30 mg/kg body weight of cisplatin at 12 weeks old to induce AKI. The kidney samples were subject to morphological studies, terminal deoxynucleotidyl transferase-mediated deoxyuridine nick-end labeling (TUNEL) assay, immunohistochemistry and RT-qPCR. Serum levels of creatinine, blood urea nitrogen (BUN) and tumor necrosis factor alpha (TNF-α) were measured. Administration of cisplatin induced a more severe AKI in adult COUP-TFII-knockout mice. An increase in dead cells in both the proximal tubules and thick ascending limb of Henle's loop (TAL) was observed in the knockout mouse kidney. The expression levels of COUP-TFII decreased in the TAL by cisplatin administration. There was no difference in the expression levels of transporter mRNAs responsible for cellular cisplatin uptake between control and knockout mouse kidney. COUP-TFII-knockout mice and COUP-TFII-depleted cells exhibited an elevation in TNF-α levels, suggesting the involvement of the TNF-α pathway. Chromatin immunoprecipitation showed that COUP-TFII was enriched in the potential binding site, suggesting that COUP-TFII might directly suppress the TNF-α gene at transcriptional level. These results indicate the involvement of COUP-TFII in the pathophysiology of AKI and COUP-TFII may be a potential therapeutic target for AKI.

Orphan nuclear receptor COUP-TFII is an oncogenic gene in renal cell carcinoma.

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) may be an oncogenic gene in renal cell carcinoma (RCC). However, the direct association between COUP-TFII expression and patient survival has not been investigated in patients with RCC, and the molecular oncogenesis of COUP-TFII in RCC remains unclear. The mRNA expression levels of COUP-TFII in the tumors of 283 patients with RCC were determined by RT-qPCR. The remaining 266 patients were categorized into low- and high-expression groups according to the cut off value generated by receiver operating curve (ROC) analysis. The function of COUP-TFII in RCC cells was tested by knockdown experiments in vitro. In the present study, it was revealed that the mRNA expression levels of COUP-TFII were significantly higher in tumors compared with those in adjacent non-cancerous tissues, and that the overexpression of COUP-TFII was strongly associated with poor patient survival. It was further demonstrated that knockdown of COUP-TFII suppressed proliferation, and induced apoptosis and cell cycle arrest in RCC cells in vitro. This also resulted in the activation of the mitochondria-mediated apoptosis pathway, impaired migration and invasion of RCC cells through epithelial-mesenchymal transition in vitro, and suppressed tumor growth in vivo. In addition, it was revealed that the induction of cell migration and invasion by COUP-TFII was mediated, at least in part, by integrin subunit β1. In summary, the present study indicated that COUP-TFII is an oncogenic gene in RCC, and a potential therapeutic target for the treatment of the disease.

COUP-TFII is a modulator of cell-type-specific genetic programs based on genomic localization maps

Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) is a member of the steroid/thyroid hormone receptor superfamily, but its ligand has not yet been identified. Little is known about the role of the COUP-TFII nuclear receptor in cancer cells. In this study, we mapped the cistrome of COUP-TFII in three different cancer cells, namely breast cancer cells (MCF-7), myelogenous leukaemia cells (K562) and liver cancer cells (HepG2) using publicly available ChIP-seq data. Our results show that COUP-TFII co-localises with master transcription factors (TFs) in a cell-specific manner such as estrogen receptor alpha in MCF-7, hepatocyte nuclear factor alpha in HepG2, and GATA-binding factor in K562, while the shared, non-specific COUP-TFII binding sites are co-occupied by CTCF. We identified chromatin environments for these COUP-TFII and master TF co-bound sites together with COUP-TFII and CTCF co-bound sites. Our results show that COUP-TFII and master TF co-bound sites are marked with active enhancer specific histone modifications (H3K27ac and H3K4me1), while COUP-TFII and CTCF co-bound sites reveal active promoter specific histone marks (H3K27ac and H3K4me3). These results describe the genomic context and role of COUP-TFII in the cell-type specific transcriptional programs. Furthermore, we report that the VEGFA gene regulated by shared COUP-TFII and CTCF co-bound regulatory elements is involved in long-range looping in a cell-type-independent manner. These findings provide a genomic insight into the regulation and angiogenic role of COUP-TFII.

Repression of COUP‐TFII by proinflammatory cytokines contributes to endometriotic lymphangiogenesis

Endometriosis is a common gynecological disease that affects 8–10% women of reproductive age. It is characterized as the presence of endometriotic lesions outside the uterine cavity and causes severe symptoms in patients such as pelvic pains, dyspareunia, and even infertility. Greater angiogenic and lymphangiogenic processes have been found in ectopic lesions. However, the underlying mechanism is largely unknown. In the present study, we found VEGF‐C is highly secreted by endometriotic stromal cells. Bioinformatic and molecular characterization reveals that elevation of VEGF‐C in endometriotic stromal cells is mediated by derepression of chicken ovalbumin upstream promoter‐transcription factor II (COUP‐TFII) dependent transcriptional regulation. Further investigation demonstrates that level of COUP‐TFII is suppressed by proinflammatory cytokines such as interleukin‐1β and tumor necrosis factor‐α. More importantly, we show, for the first time, that functional VEGF‐C can be transported by exosomes, a 30–100 nm‐size extracellular vesicles derived from the endosomal compartments, to enhance the tube formation abilities of lymphatic endothelial cells. Blockage of VEGF‐C signaling by a highly selective inhibitor of VEGFR‐2/3, Lenvatinib, abolishes loss of COUP‐TFII‐mediated lymphangiogenesis in endometriosis both in in vitro and in vivo models. Herein, we unveil the novel mechanism of VEGF‐C transportation by extracellular vesicles to communicate between endometriotic cells and lymphatic endothelial cells and demonstrate the pathophysiological process of VEGF‐C in the progression of endometriosis.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

COUP‑TFII promotes epithelial‑mesenchymal transition by inhibiting miR‑34a expression in colorectal cancer.

Chicken ovalbumin upstream promoter‑transcription factorII (COUP‑TFII) expression is upregulated in colorectal cancer and is associated with its progression and a poor prognosis. The aim of the present study was to determine whether COUP‑TFII regulates colorectal cancer cell (CRC) invasion and migration by inhibiting microRNA (miR)‑34a. Transwell system and wound healing assays were performed to examine cell invasiveness and migration, respectively. Reverse transcription polymerase chain reaction and western blotting were used to detect the RNA and protein levels of target molecules, respectively. The results revealed that COUP‑TFII knockdown significantly inhibited CRC invasion and migration. In addition, the expression of miR‑34a, a well‑known tumor suppressor was revealed to be inversely correlated with COUP‑TFII expression. The miR‑34a mimic significantly reduced CRC invasion and migration abilities, while the miR‑34a inhibitor enhanced CRC invasion and migration activity. There was no significant difference between the negative small interfering RNA and miR‑34a inhibitor groups following knockdown of COUP‑TFII. Furthermore, western blotting demonstrated that miR‑34a mimics inhibited the epithelial‑mesenchymal transition (EMT) process of CRCs, while the miR‑34a inhibitor had the opposite effect. Taken together, the results demonstrate that miR‑34a regulates CRC invasion and migration by examining the mechanism by which COUP‑TFII regulates EMT.

Suppression of COUP-TFII upregulates angiogenin and promotes angiogenesis in endometriosis.

How does hypoxia-mediated downregulation of chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) promote angiogenesis in endometriosis? Suppression of COUP-TFII by hypoxia stimulates angiogenesis through induction of angiogenin (ANG). The level of COUP-TFII is downregulated in endometriotic tissues, and downregulation of COUP-TFII contributes to the development of endometriosis. Twenty-seven patients of reproductive age with endometriosis were recruited in this study. Eutopic endometrial and ectopic endometriotic stromal cells were isolated, cultured and subjected to various treatments. Microarray hybridization, quantitative RT-PCR, and Western blot were used to detect gene expression in normal and endometriotic samples. A luciferase reporter assay and chromatin immunoprecipitation in normoxia- or hypoxia-treated primary cultures of human endometrial stromal cells were performed. Tube formation analysis was performed using primary human umbilical vein endothelial cells (HUVECs). Protein level of COUP-TFII was downregulated by hypoxia (P < 0.05, normoxia versus hypoxia). Loss of COUP-TFII increased the angiogenic capacity of endometrial stromal cells (P < 0.05, COUP-TFII knockdown versus knockdown control). A novel COUP-TFII target gene, ANG, was identified through microarray analysis. Chromatin immunoprecipitation and promoter activity assays demonstrated that the ANG promoter was bound and suppressed by COUP-TFII (P < 0.05, COUP-TFII overexpression versus empty vector). The levels of ANG mRNA and protein were elevated in ectopic endometriotic stromal cells and negatively correlated with COUP-TFII (P < 0.05, endometrial versus endometriotic tissues/stromal cells). Both knockdown and forced-expression of COUP-TFII further demonstrated that ANG expression and ANG-mediated angiogenic activity were negatively regulated by COUP-TFII (P < 0.05, COUP-TFII knockdown versus knockdown control, and COUP-TFII overexpression versus empty vector). This study was conducted in primary human endometrial stromal cell cultures and HUVECs, therefore, may not fully reflect the situation in vivo. The raw data were submitted to Gene Expression Omnibus (GSE107469). This is the first study to highlight that the aberrant expression of ANG in endometriotic lesions is mediated by hypoxia-suppressed COUP-TFII expression, which reveals an as yet unidentified molecular pathogenesis of endometriosis. This work was supported by research grants (MOST 105-2314-B-006-059-MY3 to M.H.W. and MOST 104-2320-B-006-036-MY3 to S.J.T.) from the Ministry of Science and Technology, Taiwan. The authors declare that there is no conflict of interest.

Downregulation of COUP-TFII inhibits glioblastoma growth via targeting MPC1.

Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) is a steroid receptor that is broadly expressed in many tissues throughout embryonic development. Previous studies indicated that COUP-TFII is dysregulated in multiple types of cancer and serves crucial roles in cancer development. The mitochondrial pyruvate carrier 1 (MPC1) is involved in transporting pyruvate for entry into the citric acid cycle, an important event in cancer progression. However, the roles of COUP-TFII and MPC1 in glioma remain unknown. In the present study, it was demonstrated that MPC1 is downregulated in glioblastoma. Furthermore, the inhibition of COUP-TFII was able to increase MPC1 expression and inhibit the growth of glioblastoma cells in vitro and in vivo. The findings from the present study demonstrated that downregulation of COUP-TFII inhibits glioblastoma growth via targeting MPC1. Therefore, COUP-TFII is a potential therapeutic target for glioma.

COUP-TFII is required for morphogenesis of the neural crest-derived tympanic ring

Chicken Ovalbumin Upstream Promoter-Transcription Factor II (COUP-TFII) plays pivotal roles in cell growth, cell differentiation, and cell fate determination. Although genome-wide studies have identified COUP-TFII binding on gene sets mainly involved in neural crest cell (NCC) development and craniofacial morphogenesis, the direct functional connection between COUP-TFII and NCCs in vivo has not been well characterized. In this study, we show that COUP-TFII is expressed in the subpopulation of NCCs and its derivatives, and targeted ablation of COUP-TFII in mouse NCCs results in markedly shortened and bifurcated tympanic rings, which in turn disturb the caudal direction of external acoustic meatus invagination. However, formation of the manubrium of the malleus (MM) in Wnt1-Cre/+;COUP-TFIIflox/flox mice is not perturbed, suggesting that the rostral half of the tympanic ring is sufficient to support proper MM development. Interestingly, we found that loss of COUP-TFII up-regulates Sox9 in the tympanic ring primordium and affects the distribution of preosteoblasts before mesenchymal condensation. Together, our results demonstrate that COUP-TFII plays an essential role in regulating the patterning of the NCC-derived tympanic ring.

Endoglin inhibition leads to intussusceptive angiogenesis via activation of factors related to COUP-TFII signaling pathway.

Angiogenesis is a highly coordinated, extremely complex process orchestrated by multiple signaling molecules and blood flow conditions. While sprouting mode of angiogenesis is very well investigated, the molecular mechanisms underlying intussusception, the second mode of angiogenesis, remain largely unclear. In the current study two molecules involved in vascular growth and differentiation, namely endoglin (ENG/CD105) and chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) were examined to unravel their specific roles in angiogenesis. Down- respectively up-regulation of both molecules tightly correlates with intussusceptive microvascular growth. Upon ENG inhibition in chicken embryo model, formation of irregular capillary meshwork accompanied by increased expression of COUP-TFII could be observed. This dynamic expression pattern of ENG and COUP-TFII during vascular development and remodeling correlated with formation of pillars and progression of intussusceptive angiogenesis. Similar findings could be observed in mammalian model of acute rat Thy1.1 glomerulonephritis, which was induced by intravenous injection of anti-Thy1 antibody and has shown upregulation of COUP-TFII in initial phase of intussusception, while ENG expression was not disturbed compared to the controls but decreased over the time of pillar formation. In this study, we have shown that ENG inhibition and at the same time up-regulation of COUP-TFII expression promotes intussusceptive angiogenesis.

Expression of chicken ovalbumin upstream promoter-transcription factor II and liver X receptor as prognostic indicators for human colorectal cancer.

Cholesterol increases the risk of colorectal cancer. Liver X receptor (LXR), retinoid X receptor (RXR)α and sterol regulatory element binding protein (SREBP)-1c are transcriptional regulators of lipid metabolism. Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) serves an essential role in angiogenesis and development, but its role in cancer is controversial. The expression of COUP-TFII, LXR, RXRα and SREBP-1c in colorectal cancer, as well as their association with clinicopathologic features, was assessed, and their utility as prognostic indicators in colorectal cancer evaluated. Colorectal cancer samples (n=707 patients) were analyzed for COUP-TII, LXR, RXRα and SREBP-1c expression by immunohistochemistry. Overall survival curves of patients with tumors expressing different levels of these proteins were produced and risk factors were assessed. Of the 707 patients, 32.7, 50.9, 56.4, and 41.7% were positive for COUP-TFII, LXR, RXRα, and SREBP-1c, respectively. The lack of COUP-TFII or LXR expression was associated with lower overall survival rates (P=0.0154 for COUP-TFII, and 0.0113 for LXR). Following adjustment for other clinical risk factors (age, sex, tumor size, grade, vascular invasion, and Tumor-Node-Metastasis stage), the lack of COUP-TFII or LXR expression was a negative independent prognostic factor for survival. The expression of COUP-TFII and LXR alone or in combination may be biomarkers to indicate a positive prognosis in patients with colorectal cancer.

Dysregulation of nuclear receptor COUP-TFII impairs skeletal muscle development

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) has been shown to inhibit myogenesis and skeletal muscle metabolism in vitro. However, its precise role and in vivo function in muscle development has yet to be clearly defined. COUP-TFII protein expression level is high in undifferentiated progenitors and gradually declines during differentiation, raising an important question of whether downregulation of COUP-TFII expression is required for proper muscle cell differentiation. In this study, we generated a mouse model ectopically expressing COUP-TFII in myogenic precursors to maintain COUP-TFII activity during myogenesis and found that elevated COUP-TFII activity resulted in inefficient skeletal muscle development. Using in vitro cell culture and in vivo mouse models, we showed that COUP-TFII hinders myogenic development by repressing myoblast fusion. Mechanistically, the inefficient muscle cell fusion correlates well with the transcriptional repression of Npnt, Itgb1D and Cav3, genes important for cell-cell fusion. We further demonstrated that COUP-TFII also reduces the activation of focal adhesion kinase (FAK), an integrin downstream regulator which is essential for fusion process. Collectively, our studies highlight the importance of down-regulation of COUP-TFII signaling to allow for the induction of factors crucial for myoblast fusion.

The Role of COUP-TFII in Striated Muscle Development and Disease.

Skeletal and cardiac muscles are the only striated muscles in the body. Although sharing many structural and functional similarities, skeletal and cardiac muscles have intrinsic differences in terms of physiology and regenerative potential. While skeletal muscle possesses a robust regenerative response, the mammalian heart has limited repair capacity after birth. In this review, we provide an updated view regarding chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) function in vertebrate myogenesis, with particular emphasis on the skeletal and cardiac muscles. We also highlight the new insights of COUP-TFII hyperactivity underlying striated muscle dysfunction. Lastly, we discuss the challenges and strategies in translating COUP-TFII action for clinical intervention.