Wingless-type MMTV Integration Site Family Research Articles

Insights into Molecular Features of Venerupis decussata Oocytes: A Microarray-Based Study

The production of Venerupis decussata relies on wild seed collection, which has been recently compromised due to recruitment failure and severe mortalities. To address this issue and provide an alternative source of seed, artificial spawning and larval rearing programs were developed. However, hatchery-based seed production is a relatively new industry and it is still underdeveloped. A major hurdle in the European clam seed production is the control of spawning and reproduction, which is further hindered by the impossibility of obtaining fertile gametes by gonadal “stripping”, as meiosis re-initiation is constrained to a maturation process along the genital ducts. In the present study, oocytes were collected from 15 females and microarray analyses was performed to investigate gene expression profiles characterizing released and stripped ovarian oocytes. A total of 198 differentially expressed transcripts between stripped and spawned oocytes were detected. Functional analysis carried out on these transcripts highlighted the importance of a few biological processes, which are most probably implicated in the control of oocyte competence. Significant differences were observed for transcripts encoding proteins involved in meiosis progression (e.g. dual specificity phosphatase CDC25), WNT signalling (e.g. frizzled class receptor 8, wingless-type MMTV integration site family member 4), steroid synthesis (e.g. progestin and adipoQ receptor family member 3, cytochrome P450-C17), mRNA processing (e.g. zinc finger protein XlCOF28), calcium regulation (e.g. regucalcin, calmodulin) and ceramide metabolism (ceramidase B, sphingomyelinase). This study provides new information on transcriptional profiles putatively associated with ovarian egg infertility, and suggests potential mechanisms regulating early oocyte development in clams. Genes which were differentially expressed between stripped and spawned oocytes might have a pivotal role during maturation process in the gonadal duct and could be interesting targets for further functional studies aiming to make ovarian oocytes fertilizable.

Suppression of wingless-type MMTV integration site family, member 1 expression by small interfering RNA inhibits U251 glioma cell growth in vitro.

A Wingless-type MMTV integration site family, member 1 (Wnt-1) RNA interference expression vector was constructed during the present study, which was used to transfect the glioma U251 cell line and investigate its effect on glioma. Two 21-base oligonucleotides complementary to the coding sequence that was flanking the loop sequence were designed to form a DNA hairpin template for the target small interfering RNA (siRNA). The siRNA templates were cloned into the siRNA expression vector, pGPU6/green fluorescent protein (GFP)/Neo and the sequence was confirmed by DNA sequencing. The pGPU6/GFP/Neo-short hairpin RNA (shRNA)-Wnt-1 vector was subsequently transfected into U251 cells, and reverse transcription polymerase chain reaction and western blot analysis were used to evaluate the Wnt-1 gene silencing effect on U251 cell growth by MTT assay and flow cytometry. The Wnt-1 protein expression was significantly reduced following transfection with the recombinant plasmid, as determined by western blot analysis of the transfected U251 cells. This transfection exhibited a significantly higher death rate, as shown by MTT. Thus, the present study demonstrated that the pGPU6/GFP/Neo-shRNA-Wnt-1 vector inhibited Wnt-1 protein expression. However, further investigations regarding the Wnt signaling pathway in glioma pathogenesis are required.

Autophagy regulator BECN1 suppresses mammary tumorigenesis driven by WNT1 activation and following parity

Earlier studies reported allelic deletion of the essential autophagy regulator BECN1 in breast cancers implicating BECN1 loss, and likely defective autophagy, in tumorigenesis. Recent studies have questioned the tumor suppressive role of autophagy, as autophagy-related gene (Atg) defects generally suppress tumorigenesis in well-characterized mouse tumor models. We now report that, while it delays or does not alter mammary tumorigenesis driven by Palb2 loss or ERBB2 and PyMT overexpression, monoallelic Becn1 loss promotes mammary tumor development in 2 specific contexts, namely following parity and in association with wingless-type MMTV integration site family, member 1 (WNT1) activation. Our studies demonstrate that Becn1 heterozygosity, which results in immature mammary epithelial cell expansion and aberrant TNFRSF11A/TNR11/RANK (tumor necrosis factor receptor superfamily, member 11a, NFKB activator) signaling, promotes mammary tumorigenesis in multiparous FVB/N mice and in cooperation with the progenitor cell-transforming WNT1 oncogene. Similar to our Becn1+/−;MMTV-Wnt1 mouse model, low BECN1 expression and an activated WNT pathway gene signature correlate with the triple-negative subtype, TNFRSF11A axis activation and poor prognosis in human breast cancers. Our results suggest that BECN1 may have nonautophagy-related roles in mammary development, provide insight in the seemingly paradoxical roles of BECN1 in tumorigenesis, and constitute the basis for further studies on the pathophysiology and treatment of clinically aggressive triple negative breast cancers (TNBCs).

Wingless-type MMTV integration site family member 16B (WNT16B)

Wingless-type MMTV integration site family member 16B (WNT16B)

Abstract 4067: TRPM7 channels regulate glioma stem cell through STAT3 and Notch signaling pathways

Abstract A small fraction of cancer stem cells (CSC) initiate and maintain tumors thus driving glioma tumorigenesis and are responsible for resistance to classical chemo- and radio-therapies. It is desirable to identify signaling pathways related to CSC to develop novel therapies to selectively target them. TRPM7 is a ubiquitous Ca2+ and Mg2+ permeable ion channel which contains a serine/threonine kinase. Recent studies have demonstrated that TRPM7 plays an important role in the growth and proliferation of various tumor cells. To determine the possibility of an interaction among TRPM7, Notch, STAT3 and the ALDH1 signaling in the context of brain tumors, we investigated the effects of TRPM7 pathway activation on glioma cells and stem-like cells derived from them. Methods: 1) We analyzed human stem cell signaling pathways using real time RT2 Profile PCR arrays in the A172 glioma cells upon TRPM7 gene silencing. 2) We then examined Notch and STAT3 pathway activation, Aldehyde dehydrogenase 2 family, mitochondrial (ALDH1) and CD133 expressions in parental and glioma stem cell (GSC) populations using quantitative real time-PCR, Western blot, and immunofluorence images. 3) We conducted a ChIP analysis to examine the effects of STAT3 on ALDH1 promoter by introducing constitutive STAT3 (caSTAT3) and dominant STAT3 (dnSTAT3) into A172 cells. 4) Finally, we examined the role of TRPM7 in glioma cell migration and invasion using transwell invasion assay and wound healing assay. Results: 1) RT2 Profile PCR arrays showed that TRPM7 gene silencing down-regulated genes (≥2 fold-change) involved in Notch pathway [Notch1, Jagged 1(JAG1) and Delta-like 1, Drosophila (DLL1)], Wnt pathway, Wingless-type MMTV integration site family, member 1(WNT1) and ALDH1. 2) STAT3 activation and Notch1 expression were decreased in response to TRPM7 silencing. 3) Notch-regulated genes including Notch1, Hey2, JAG1, and Survivin as well as ALDH1 were significantly expressed higher in spheroid glioma CSCs when compared with monolayer cultures. 4) ALDH1 promoter activity was activated by STAT3 in A172 cells. 5) Knockdown of TRPM7 inhibited migration and invasion of A172 cells. Conclusions: TRPM7 activates JAK2/STAT3 and/or Notch signaling pathways and leads to increased cell proliferation and migration. These findings for the first time demonstrate that TRPM7 (1) activates a previously unrecognized STAT3→ALDH1 pathway, and (2) promotes the induction of ALDH1 activity in glioma cells. (This work was supported by the National Institutes of Health grant numbers NIH R01NS047506, R01NS066027, UL1 RR025008, U54 RR026137, AHA 0840132N, and ALZ IIRG-10-173350.) Citation Format: Mingli Liu, Koichi Inoue, Tiandong Leng, Shanchun Guo, Zhigang Xiong. TRPM7 channels regulate glioma stem cell through STAT3 and Notch signaling pathways. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4067. doi:10.1158/1538-7445.AM2014-4067

The WNT/β-catenin pathway is a transcriptional regulator of CYP2E1, CYP1A2, and aryl hydrocarbon receptor gene expression in primary human hepatocytes.

The wingless-type MMTV integration site family (WNT)/β-catenin/adenomatous polyposis coli (CTNNB1/APC) pathway has been identified as a regulator of drug-metabolizing enzymes in the rodent liver. Conversely, little is known about the role of this pathway in drug metabolism regulation in human liver. Primary human hepatocytes (PHHs), which are the most physiologically relevant culture system to study drug metabolism in vitro, were used to investigate this issue. This study assessed the link between cytochrome P450 expression and WNT/β-catenin pathway activity in PHHs by modulating its activity with recombinant mouse Wnt3a (the canonical activator), inhibitors of glycogen synthase kinase 3β, and small-interfering RNA to invalidate CTNNB1 or its repressor APC, used separately or in combination. We found that the WNT/β-catenin pathway can be activated in PHHs, as assessed by universal β-catenin target gene expression, leucine-rich repeat containing G protein-coupled receptor 5. Moreover, WNT/β-catenin pathway activation induces the expression of CYP2E1, CYP1A2, and aryl hydrocarbon receptor, but not of CYP3A4, hepatocyte nuclear factor-4α, or pregnane X receptor (PXR) in PHHs. Specifically, we show for the first time that CYP2E1 is transcriptionally regulated by the WNT/β-catenin pathway. Moreover, CYP2E1 induction was accompanied by an increase in its metabolic activity, as indicated by the increased production of 6-OH-chlorzoxazone and by glutathione depletion after incubation with high doses of acetaminophen. In conclusion, the WNT/β-catenin pathway is functional in PHHs, and its induction in PHHs represents a powerful tool to evaluate the hepatotoxicity of drugs that are metabolized by CYP2E1.

Wingless-type MMTV integration site family member 4 (WNT4)

Wingless-type MMTV integration site family member 4 (WNT4)

Association of CDKN2B-AS and WNT4 genetic polymorphisms in Korean patients with endometriosis

To investigate whether specific genetic polymorphisms in the cyclin-dependent kinase inhibitor 2B antisense RNA (CDKN2B-AS) gene and near the wingless-type MMTV integration site family member 4 (WNT4) gene are associated with endometriosis in a Korean population. Case-control genetic association study. University. Surgically or histologically diagnosed cases of endometriosis (n=673) and controls (n=500) among a population of ethnic Koreans. None. Genotype distribution and synergistic interaction. Significant differences were found in the allele distributions of the CC genotype of the rs10965235 single-nucleotide polymorphism (SNP) of the CDKN2B-AS gene and the GG genotype of the rs16826658 SNP on chromosome 1p36 between the endometriosis cases and the controls (rs10965235: 69.7% CC, 26.9% CA, and 3.4% AA vs. 59.2% CC, 35.2% CA, and 5.6% AA; rs16826658: 33.7% GG, 48.4% GT, and 17.8% TT vs. 25.6% GG, 49.8% GT, and 24.6% TT, respectively). A significant interaction was not found between the CC genotype of the rs10965235 SNP and the GG genotype of the rs16826658 SNP after Bonferroni correction (32.8% of CC+GG and 67.2% of CC+non-GG in the endometriosis cases vs. 25.0% of CC+GG and 75.0% of CC+non-GG in the controls). Our results suggest that the rs10965235 SNP in the CDKN2B-AS gene and the rs16826658 SNP near the WNT4 gene were significantly associated with endometriosis in this Korean population.

Osteogenesis imperfecta due to mutations in non-collagenous genes: lessons in the biology of bone formation.

Osteogenesis imperfecta or 'brittle bone disease' has mainly been considered a bone disorder caused by collagen mutations. Within the last decade, however, a surge of genetic discoveries has created a new paradigm for osteogenesis imperfecta as a collagen-related disorder, where most cases are due to autosomal dominant type I collagen defects, while rare, mostly recessive, forms are due to defects in genes whose protein products interact with collagen protein. This review is both timely and relevant in outlining the genesis, development, and future of this paradigm shift in the understanding of osteogenesis imperfecta. Bone-restricted interferon-induced transmembrane (IFITM)-like protein (BRIL) and pigment epithelium-derived factor (PEDF) defects cause types V and VI osteogenesis imperfecta via defective bone mineralization, while defects in cartilage-associated protein (CRTAP), prolyl 3-hydroxylase 1 (P3H1), and cyclophilin B (CYPB) cause types VII-IX osteogenesis imperfecta via defective collagen post-translational modification. Heat shock protein 47 (HSP47) and FK506-binding protein-65 (FKBP65) defects cause types X and XI osteogenesis imperfecta via aberrant collagen crosslinking, folding, and chaperoning, while defects in SP7 transcription factor, wingless-type MMTV integration site family member 1 (WNT1), trimeric intracellular cation channel type b (TRIC-B), and old astrocyte specifically induced substance (OASIS) disrupt osteoblast development. Finally, absence of the type I collagen C-propeptidase bone morphogenetic protein 1 (BMP1) causes type XII osteogenesis imperfecta due to altered collagen maturation/processing. Identification of these multiple causative defects has provided crucial information for accurate genetic counseling, inspired a recently proposed functional grouping of osteogenesis imperfecta types by shared mechanism to simplify current nosology, and has prodded investigations into common pathways in osteogenesis imperfecta. Such investigations could yield critical information on cellular and bone tissue mechanisms and translate to new mechanistic insight into clinical therapies for patients.

WNT1 (wingless-type MMTV integration site family, member 1)

Review on WNT1, with data on DNA/RNA, on the protein encoded and where the gene is implicated.

Mechanical forces induce odontoblastic differentiation of mesenchymal stem cells on three-dimensional biomimetic scaffolds.

The mechanical induction of cell differentiation is well known. However, the effect of mechanical compression on odontoblastic differentiation remains to be elucidated. Thus, we first determined the optimal conditions for the induction of human dental pulp stem cells (hDPSCs) into odontoblastic differentiation in response to mechanical compression of three-dimensional (3D) scaffolds with dentinal tubule-like pores. The odontoblastic differentiation was evaluated by gene expression and confocal laser microscopy. The optimal conditions, which were: cell density, 4.0 × 105 cells/cm2 ; compression magnitude, 19.6 kPa; and loading time, 9 h, significantly increased expression of the odontoblast-specific markers dentine sialophosphoprotein (DSPP) and enamelysin and enhanced the elongation of cellular processes into the pores of the membrane, a typical morphological feature of odontoblasts. In addition, upregulation of bone morphogenetic protein 7 (BMP7) and wingless-type MMTV integration site family member 10a (Wnt10a) was observed. Moreover, the phosphorylation levels of mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 were also enhanced by mechanical compression, indicating the involvement of the MAPK signalling pathway. It is noteworthy that human mesenchymal stem cells (MSCs) derived from bone marrow and amnion also differentiated into odontoblasts in response to the optimal mechanical compression, demonstrating the importance of the physical structure of the scaffold in odontoblastic differentiation. Thus, odontoblastic differentiation of hDPSCs is promoted by optimal mechanical compression through the MAPK signalling pathway and expression of the BMP7 and Wnt10a genes. The 3D biomimetic scaffolds with dentinal tubule-like pores were critical for the odontoblastic differentiation of MSCs induced by mechanical compression. Copyright © 2014 John Wiley & Sons, Ltd.

Lgr4 gene regulates corpus luteum maturation through modulation of the WNT-mediated EGFR-ERK signaling pathway.

Luteal-phase insufficiency is one of the major causes of female infertility, but the molecular mechanisms are still largely unknown. Here we found that disruption of Lgr4/Gpr48, the newly identified receptor for R-spondins, greatly reduced female fertility in mice. The expression of Lgr4 was induced specifically in granulosa-lutein cells during luteinization. In Lgr4-deficient female mice, the estrous cycle was prolonged and serum progesterone levels were dramatically downregulated. In Lgr4(-/-) corpora lutea, the expression of key enzymes for steroidogenesis as well as common luteal marker genes was significantly decreased. Additionally, the activity of epidermal growth factor receptor (EGFR)-ERK signaling was attenuated in Lgr4(-/-) granulosa-lutein cells. We found that the maturation of Lgr4(-/-) cells was impaired in cultured primary granulosa cells, but the defect was partially rescued by reactivation of EGFR signaling by heparin-binding EGF-like growth factor treatment. We found that the expression of wingless-type MMTV integration site family (WNT)/catenin (cadherin associated protein), beta 1 (CTNNB1) downstream targets, including matrix metalloproteinase 9, which is a critical matrix metalloproteinase for activation of EGF-like factors, was significantly downregulated in Lgr4(-/-) ovaries. Matrix metalloproteinase 9 inhibitor treatment attenuated human chorionic gonadotropin- but not heparin-binding EGF-like growth factor-induced ERK activation and luteinization in primary granulosa cells. Together, we report that Lgr4 modulates WNT-mediated EGFR-ERK signaling to facilitate corpus luteum maturation and ovarian steroidogenesis to maintain female reproduction.

Ex vivo wingless-type MMTV integration site family member 7A (WNT7A) treatment of myogenic cells prior to muscle cell transplantation to enhance both fusion with myofibrils and muscle function

Ex vivo wingless-type MMTV integration site family member 7A (WNT7A) treatment of myogenic cells prior to muscle cell transplantation to enhance both fusion with myofibrils and muscle function

Oncogenic effects of WNT5A in Epstein-Barr virus-associated nasopharyngeal carcinoma

The molecular events that drive the progression of Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) are still to be elucidated. Here, we report for the first time the pathogenic significance of an NPC-associated gene, wingless-type MMTV integration site family, member 5A (WNT5A) and the contribution of EBV to its expression. WNT5A is a representative Wnt protein that activates non-canonical Wnt signalling. With regard to its role in carcinogenesis, there is conflicting evidence as to whether WNT5A has a tumour-promoting or tumour-suppressive role. We show that WNT5A is upregulated in primary NPC tissue samples. We also demonstrate that WNT5A expression was dramatically increased in NPC cell lines expressing the EBV-encoded LMP2A gene, suggesting that this EBV-encoded latent gene is responsible for upregulating WNT5A in NPC. In addition, in vitro WNT5A overexpression promotes the proliferation, migration and invasion of NPC cells. Our results not only reveal pro-tumorigenic effects of WNT5A in NPC but also suggest that WNT5A could be an important therapeutic target in patients with EBV-associated disease.

The impact of bone marrow adipocytes on osteoblast and osteoclast differentiation

Throughout life, bone is constantly remodeled through the complementary processes of bone resorption and bone formation. Highly coordinated regulation of these activities is essential for maintaining consistent bone quality and quantity. Normally, the development and function of bone-forming (osteoblast) and bone-resorbing (osteoclast) cells are tightly regulated by signaling molecules secreted by these two cell types. Within the bone marrow microenvironment, osteoblasts arise from mesenchymal stem cells (MSCs), which are in close contact with the hematopoietic stem cell (HSC) precursors that differentiate into mature osteoclasts. Signaling molecules secreted by osteoblasts (e.g., receptor activator of nuclear factor kappa B ligand and osteoprotegerin) and osteoclasts (e.g., bone morphogenetic protein 6, wingless-type MMTV integration site family member 10B, sphingosine-1-phosphate, and ephrin-B2) play a key role in bone remodeling by guiding the differentiation, localization, and function of bone cells. In addition to osteoblasts, bone marrow MSCs can also differentiate into adipocytes that affect bone remodeling by competitively suppressing intracellular osteogenic signals, including runt-related transcription factor 2, osterix, and beta-catenin, while simultaneously promoting the secretion of adipogenic signaling molecules such as leptin, adiponectin, chemerin, omentin-1, resistin, and visfatin. Secreted adipogenic factors have also been shown to affect the osteoclastogenic differentiation of HSCs. Herein, we discuss the impact of bone marrow adipocytes on the coupling of osteoblast and osteoclast differentiation, and the relevance to bone-loss disorders such as osteoporosis. © 2014 IUBMB Life, 66(3):147-155, 2014.

Long non‐coding RNA UCA1 increases chemoresistance of bladder cancer cells by regulating Wnt signaling

Chemotherapy is a reasonable alternative to cystectomy in patients with invasive and advanced bladder cancer. However, bladder cancer cells often develop drug resistance to these therapies, and ~ 50% of patients with advanced bladder cancer do not respond to chemotherapy. Recent studies have shown that long non-coding RNA (lncRNA) is involved in the development of chemoresistance. Here we investigated the role of the urothelial cancer-associated 1 (UCA1) lncRNA in cisplatin resistance during chemotherapy for bladder cancer. We showed that cisplatin-based chemotherapy results in up-regulation of UCA1 expression in patients with bladder cancer. Similarly, UCA1 levels are increased in cisplatin-resistant bladder cancer cells. Over-expression of UCA1 significantly increases the cell viability during cisplatin treatment, whereas UCA1 knockdown reduces the cell viability during cisplatin treatment. UCA1 inhibition also partially overcomes drug resistance in cisplatin-resistant T24 cells. Furthermore, we showed that UCA1 positively regulates expression of wingless-type MMTV integration site family member 6 (Wnt6) in human bladder cancer cell lines. UCA1 and Wnt6 expression is also positively correlated in vivo. Up-regulation of UCA1 activates Wnt signaling in a Wnt6-dependent manner. We finally demonstrate that UCA1 increases the cisplatin resistance of bladder cancer cells by enhancing the expression of Wnt6, and thus represents a potential target to overcome chemoresistance in bladder cancer.

Wnt3a activates β1-integrin and regulates migration and adhesion of vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs) are known to undergo functional changes that contribute to the pathogenesis of atherosclerosis and restenosis. Wnts are a family of secreted glycoproteins that bind to transmembrane Frizzled receptors and initiate signaling cascades with indispensable roles during cell migration, adhesion, proliferation, and survival. The present study reports that wingless-type MMTV integration site family, member 3a (Wnt3a) activates the canonical Wnt pathway in rat VSMCs by triggering the phosphorylation of β-catenin at position Ser675 and GSK-3β at position Ser9. Phosphorylation of these two proteins increases VSMC migration and adhesion. In a search for the downstream mediators of Wnt3a's effects on VSMC migration and adhesion, Wnt3a treatment was observed to increase integrin-linked kinase (ILK) protein expression. ILK is a serine/threonine protein kinase that is thought to control cell migration and adhesion by regulating the affinity of β1-integrin for the extracellular matrix. Wnt3a treatment of VSMCs also activated β1-integrin without changing the quantity of protein expressed on the cell surface. These results demonstrate that Wnt3a enhances migration and adhesion of VSMCs by activating β1-integrin.

Myogenic Differentiation of Muscular Dystrophy-Specific Induced Pluripotent Stem Cells for Use in Drug Discovery

Human induced pluripotent stem cells (iPSCs) represent a scalable source of potentially any cell type for disease modeling and therapeutic screening. We have a particular interest in modeling skeletal muscle from various genetic backgrounds; however, efficient and reproducible methods for the myogenic differentiation of iPSCs have not previously been demonstrated. Ectopic myogenic differentiation 1 (MyoD) expression has been shown to induce myogenesis in primary cell types, but the same effect has been unexpectedly challenging to reproduce in human iPSCs. In this study, we report that optimization of culture conditions enabled direct MyoD-mediated differentiation of iPSCs into myoblasts without the need for an intermediate step or cell sorting. MyoD induction mediated efficient cell fusion of mature myocytes yielding multinucleated myosin heavy chain-positive myotubes. We applied the same approach to dystrophic iPSCs, generating 16 iPSC lines from fibroblasts of four patients with Duchenne and Becker muscular dystrophies. As seen with iPSCs from healthy donors, within 36 hours from MyoD induction there was a clear commitment toward the myogenic identity by the majority of iPSCs in culture (50%-70%). The patient iPSC-derived myotubes successfully adopted the skeletal muscle program, as determined by global gene expression profiling, and were functionally responsive to treatment with hypertrophic proteins insulin-like growth factor 1 (IGF-1) and wingless-type MMTV integration site family, member 7A (Wnt7a), which are being investigated as potential treatments for muscular dystrophy in clinical and preclinical studies, respectively. Our results demonstrate that iPSCs have no intrinsic barriers preventing MyoD from inducing efficient and rapid myogenesis and thus providing a scalable source of normal and dystrophic myoblasts for use in disease modeling and drug discovery.

The non-canonical Wnt5a/Ror2 signaling pathway in bone metabolism

Wingless-type MMTV integration site (Wnt) family molecules, a family of secreted glycoproteins have now gathered attention as a therapeutic target. Drug innovation targeting the canonical Wnt pathway is in the most interest since its molecular mechanism is well understood and clinical trials are in progress for osteoporosis. Recent findings have revealed the contribution of the non-canonical Wnt pathway in malignant tumors suggesting this pathway as a new treatment target, but it is relatively less understood. Recently, several reports have demonstrated the involvement of the non-canonical Wnt pathway in the bone metabolism. Therefore, we have compiled the current understanding of the non-canonical Wnt pathway in association with bone metabolism.

TCF7L2 in mouse pancreatic beta cells plays a crucial role in glucose homeostasis by regulating beta cell mass

Common genetic variations of the transcription factor 7-like 2 gene (encoded by TCF7L2), one of the T cell factor/lymphoid enhancer-binding factor transcription factors for the converging wingless-type MMTV integration site family (Wnt)/β-catenin signalling pathway, are known to be associated with type 2 diabetes. Individuals with at-risk alleles of TCF7L2 exhibit impaired insulin secretion. Although previous studies using animal models have revealed the existence of a relationship between the Wnt/β-catenin signalling pathway and glucose homeostasis, it remains unclear whether TCF7L2 in the pancreatic beta cells might be causally involved in insulin secretion in vivo. In this study, we investigated the role of TCF7L2 expressed in the pancreatic beta cells in glucose homeostasis. Three independent groups of genetically engineered mice (DN mice) were generated, in which expression of the dominant-negative form of Tcf7l2 was driven under a rat insulin promoter. Phenotypes of both adult and newborn mice were evaluated. The levels of genes and proteins expressed in isolated islets were determined by reverse transcription-quantitative PCR and western blot analysis, respectively. Adult DN mice showed impaired glucose tolerance and decreased insulin secretion in both oral and intraperitoneal glucose tolerance tests. Marked reduction of the beta cell area and whole-pancreas insulin content was observed in both the adult and newborn DN mice. Islets from the DN mice showed decreased gene expressions of Ccnd1, Ccnd2, Irs1, Irs2, Ins1, Ins2 and Mafa, consistent with the deleterious effects of the dominant-negative form of Tcf7l2 on beta cell proliferation and insulin production. TCF7L2 expressed in the pancreatic beta cells plays a crucial role in glucose metabolism through regulation of the beta cell mass.