Wnt4 inhibits beta-catenin/TCF signalling by redirecting beta-catenin to the cell membrane

Prdm15 acts upstream of Wnt4 signaling in anterior neural development of Xenopus laevis

Mutations in PRDM15 lead to a syndromic form of holoprosencephaly (HPE) known as the Galloway-Mowat syndrome (GAMOS). While a connection between PRDM15, a zinc finger transcription factor, and WNT/PCP signaling has been established, there is a critical need to delve deeper into their contributions to early development and GAMOS pathogenesis. We used the South African clawed frog Xenopus laevis as the vertebrate model organism and observed that prdm15 was enriched in the tissues and organs affected in GAMOS. Furthermore, we generated a morpholino oligonucleotide-mediated prdm15 knockdown model showing that the depletion of Prdm15 leads to abnormal eye, head, and brain development, effectively recapitulating the anterior neural features in GAMOS. An analysis of the underlying molecular basis revealed a reduced expression of key genes associated with eye, head, and brain development. Notably, this reduction could be rescued by the introduction of wnt4 RNA, particularly during the induction of the respective tissues. Mechanistically, our data demonstrate that Prdm15 acts upstream of both canonical and non-canonical Wnt4 signaling during anterior neural development. Our findings describe severe ocular and anterior neural abnormalities upon Prdm15 depletion and elucidate the role of Prdm15 in canonical and non-canonical Wnt4 signaling.

Reciprocal Interactions Between the Epithelium and Mesenchyme in Organogenesis

Many organs are composed of epithelial and mesenchymal tissue components. These two tissue component types develop via reciprocal interactions. However, for historical and technical reasons, the effects of the mesenchymal components on the epithelium have been emphasized. Well-documented examples are the regionally specific differentiation of the endoderm-derived primitive gut tube under the influence of surrounding mesenchyme. In contrast to a pile of reports on mesenchyme-derived signaling mechanisms, few studies have depicted the epithelial action in depth. This chapter highlights an example of an opposite action from the epithelial side, which was found in esophagus development.

Plasminogen activator inhibitor 1 is associated with high-grade serous ovarian cancer metastasis and is reduced in patients who have received neoadjuvant chemotherapy

Introduction: High-grade serous ovarian cancer (HGSOC) is the most prevalent and deadliest subtype of epithelial ovarian cancer (EOC), killing over 140,000 people annually. Morbidity and mortality are compounded by a lack of screening methods, and recurrence is common. Plasminogen-activator-inhibitor 1 (PAI-1, the protein product of SERPIN E1) is involved in hemostasis, extracellular matrix (ECM) remodeling, and tumor cell migration and invasion. Overexpression is associated with poor prognosis in EOC. Platelets significantly increase PAI-1 in cancer cells in vitro, and may contribute to the hematogenous metastasis of circulating tumor cells (CTCs). CTCs are viable tumor cells that intravasate and travel through the circulation-often aided by platelets - with the potential to form secondary metastases. Here, we provide evidence that PAI-1 is central to the platelet-cancer cell interactome, and plays a role in the metastatic cascade. Methods: SK-OV-3 cells where PAI-1 had been silenced, treated with healthy donor platelets, and treated with platelet-conditioned medium were used as an in vitro model of metastatic EOC. Gene expression analysis was performed using RNA-Seq data from untreated cells and cells treated with PAI-1 siRNA or negative control, each with and without platelets. Four cohorts of banked patient plasma samples (n = 239) were assayed for PAI-1 by ELISA. Treatment-naïve (TN) whole blood (WB) samples were evaluated for CTCs in conjunction with PAI-1 evaluation in matched plasma. Results and discussion: Significant phenotypic changes occurring when PAI-1 was silenced and when platelets were added to cells were reflected by RNA-seq data, with PAI-1 observed to be central to molecular mechanisms of EOC metastasis. Increased proliferation was observed in cells treated with platelets. Plasma PAI-1 significantly correlated with advanced disease in a TN cohort, and was significantly reduced in a neoadjuvant chemotherapy (NACT) cohort. PAI-1 demonstrated a trend towards significance in overall survival (OS) in the late-stage TN cohort, and correlation between PAI-1 and neutrophils in this cohort was significant. 72.7% (16/22) of TN patients with plasma PAI-1 levels higher than OS cutoff were CTC-positive. These data support a central role for PAI-1 in EOC metastasis, and highlight PAI-1's potential as a biomarker, prognostic indicator, or gauge of treatment response in HGSOC.

A WNT4- and DKK3-driven canonical to noncanonical Wnt signaling switch controls multiciliogenesis

Multiciliated cells contain hundreds of cilia whose directional movement powers the mucociliary clearance of the airways, a vital host defense mechanism. Multiciliated cell specification requires canonical Wnt signaling, which then must be turned off. Next, ciliogenesis and polarized ciliary orientation are regulated by noncanonical Wnt/planar cell polarity (Wnt/PCP) signaling. The mechanistic relationship between the Wnt pathways is unknown. We show that DKK3, a secreted canonical Wnt regulator and WNT4, a noncanonical Wnt ligand act together to facilitate a canonical to noncanonical Wnt signaling switch during multiciliated cell formation. In primary human airway epithelial cells, DKK3 and WNT4 CRISPR knockout blocks, whereas ectopic expression promotes, multiciliated cell formation by inhibiting canonical Wnt signaling. Wnt4 and Dkk3 single-knockout mice also display defective ciliated cells. DKK3 and WNT4 are co-secreted from basal stem cells and act directly on multiciliated cells via KREMEN1 and FZD6, respectively. We provide a novel mechanism that links specification to cilium biogenesis and polarization for proper multiciliated cell formation.

Dickkopf-1 and ROCK2 upregulation and associated protein aggregation in pseudoexfoliation syndrome and glaucoma

AIMS

The etiology of pseudoexfoliation (PEX), a stress-induced fibrillopathy and a leading cause of secondary glaucoma worldwide, remains limited. This study aims to understand the role of the Wnt antagonist Dickkopf-related protein 1 (DKK1) in PEX pathophysiology and assess its candidature as a biomarker for PEX.

MAIN METHODS

Expression levels of DKK1 and Wnt signaling genes were assayed in the anterior ocular tissues of study subjects by qRT-PCR, Western blotting, and immunohistochemistry. Protein aggregation was studied through Proteostat staining. Role of DKK1 in protein aggregation and regulation of target Wnt signaling genes was elucidated through overexpression and knockdown studies in Human Lens Epithelial cells (HLEB3). Levels of DKK1 in circulating fluids were assayed through ELISA.

KEY FINDINGS

DKK1 upregulation was observed in lens capsule and conjunctiva tissues of PEX individuals compared to controls correlating with an upregulation of the Wnt signaling target, ROCK2. Proteostat staining showed increased protein aggregates in lens epithelial cells of PEX patients. HLE B-3 cells overexpressed with DKK1 showed increased protein aggregates along with upregulation of ROCK2, and knockdown of DKK1 in HLE B-3 cells demonstrated downregulation of ROCK2. Further, ROCK2 inhibition by Y-27632 in DKK1 overexpressed cells showed that DKK1 regulated protein aggregation via ROCK2. Also, increased levels of DKK1 were observed in patients' plasma and aqueous humor compared to controls.

SIGNIFICANCE

This study shows that DKK1 and ROCK2 might play a role in protein aggregation in PEX. Further, elevated levels of DKK1 in aqueous humor serve as a fair classifier of pseudoexfoliation glaucoma.

An Update on Genetics of Adrenal Gland and Associated Disorders

The intricacies of human adrenal development have been under scrutiny for decades. Each year marks the identification of new genes and new interactions between gene products that ultimately will act to produce the fully functioning adult gland. Due to the complexity of this process, genetic missteps may lead to a constellation of pathologies. Recent years have identified several novel genetic causes of adrenal dysgenesis and provided new insights into previously delineated processes. SF1, DAX1 (NR0B1), CDKN1C, SAMD9, GLI3, TPIT, MC2R, MRAP, NNT, TXNRD2, AAAS, and MCM4 are among the genes which have had significant contributions to our understanding of the development and function of both adrenals and gonads. Collection and elucidation of these genetic and clinical insights are valuable tools for clinicians who diagnose and manage cases of adrenal dysfunction.

Mesenchymal-epithelial crosstalk shapes intestinal regionalisation via Wnt and Shh signalling

Organs are anatomically compartmentalised to cater for specialised functions. In the small intestine (SI), regionalisation enables sequential processing of food and nutrient absorption. While several studies indicate the critical importance of non-epithelial cells during development and homeostasis, the extent to which these cells contribute to regionalisation during morphogenesis remains unexplored. Here, we identify a mesenchymal-epithelial crosstalk that shapes the developing SI during late morphogenesis. We find that subepithelial mesenchymal cells are characterised by gradients of factors supporting Wnt signalling and stimulate epithelial growth in vitro. Such a gradient impacts epithelial gene expression and regional villus formation along the anterior-posterior axis of the SI. Notably, we further provide evidence that Wnt signalling directly regulates epithelial expression of Sonic Hedgehog (SHH), which, in turn, acts on mesenchymal cells to drive villi formation. Taken together our results uncover a mechanistic link between Wnt and Hedgehog signalling across different cellular compartments that is central for anterior-posterior regionalisation and correct formation of the SI.

The small intestine forms via crosstalk between epithelial and mesenchymal cell compartments. Here, the authors show that a gradient of Wnt signalling along the anterior-posterior axis regulates Sonic Hedgehog which is required for correct formation and regionalization of the small intestine.

The Role of the Wnt Pathway in VEGF/Anti-VEGF-Dependent Control of the Endothelial Cell Barrier

Purpose

Investigate the contribution of the Wnt pathway to vascular endothelial growth factor (VEGF)/anti-VEGF-mediated control of endothelial cell permeability.

Methods

High glucose-treated primary human retinal endothelial cells (HRECs) were exposed to either VEGF, or VEGF and then anti-VEGF. Changes in gene expression were assayed by RNAseq and qRT-PCR. Permeability was monitored by electrical cell-substrate impedance sensing (ECIS). Approaches to activate the Wnt pathway included treatment with LiCl and overexpression of constitutively activated β-catenin. β-catenin-dependent transcriptional activity was monitored in HRECs stably expressing a TCF/LEF-driven reporter.

Results

VEGF/anti-VEGF altered expression of genes encoding many members of the Wnt pathway. A subset of these genes was regulated in a way that is likely to contribute to control of the endothelial cell barrier. Namely, the VEGF-induced alteration of expression of such genes was reversed by anti-VEGF, and such adjustments occurred at times corresponding to changes in barrier function. While pharmacological and molecular approaches to activate the Wnt pathway had no effect on basal permeability, they suppressed VEGF-induced relaxation. Furthermore, anti-VEGF-mediated restoration of barrier function was unaffected by activation of the Wnt pathway.

Conclusions

VEGF/anti-VEGF engages multiple members of the Wnt pathway, and activating this pathway enforces the endothelial barrier by attenuating VEGF-induced relaxation. These data suggest that FDA-approved agents such as LiCl may be an adjuvant to anti-VEGF therapy for patients afflicted with blinding conditions including diabetic retinopathy.

Cell-intrinsic Wnt4 promotes hematopoietic stem and progenitor cell self-renewal

Although intracellular Wnt signaling pathways need to be tightly regulated to promote hematopoietic stem cell self-renewal, the source and identity of important Wnt ligands in the bone marrow is still largely unknown. The noncanonical ligand Wnt4 is expressed in the bone marrow as well as in the stroma, and its overexpression in fetal liver cells facilitates thymic recovery; however, its impact on adult hematopoietic stem cell function remains unclear. Here, we report that the deletion of Wnt4 from hematopoietic cells in mice (Wnt4^Δ/Δ ) resulted in decreased lymphopoiesis at steady state. This was likely at least in part due to the increased proinflammatory environment present in the bone marrow of Wnt4^Δ/Δ mice. Wnt4^Δ/Δ hematopoietic stem cells displayed reduced reconstitution capacity in serial transplants, thus demonstrating defective self-renewal, and they expanded poorly in response to lipopolysaccharide stimulation. This appeared to be the result of the absence of Wnt4 in stem/progenitor cells, as myeloid-restricted Wnt4 deletion had no notable effect. Finally, we observed that Wnt4^Δ/Δ stem/progenitor cells were more quiescent, presenting enhanced levels of stress-associated JNK phosphorylation and p16^INK4a expression, likely contributing to the reduced expansion observed in transplants. In conclusion, our results identify a new, largely autocrine role for Wnt4 in hematopoietic stem cell self-renewal, suggesting that regulation of Wnt signaling in hematopoiesis may not need Wnt secretion and could be independent of morphogen gradients.

Metastatic suppression by DOC2B is mediated by inhibition of epithelial-mesenchymal transition and induction of senescence

Senescence induction and epithelial-mesenchymal transition (EMT) events are the opposite sides of the spectrum of cancer phenotypes. The key molecules involved in these processes may get influenced or altered by genetic and epigenetic changes during tumor progression. Double C2-like domain beta (DOC2B), an intracellular vesicle trafficking protein of the double C2 protein family, plays a critical role in exocytosis, neurotransmitter release, and intracellular vesicle trafficking. DOC2B is repressed by DNA promoter hypermethylation and functions as a tumor growth regulator in cervical cancer. To date, the molecular mechanisms of DOC2B in cervical cancer progression and metastasis is elusive. Herein, the biological functions and molecular mechanisms regulated by DOC2B and its impact on senescence and EMT are described. DOC2B inhibition promotes proliferation, growth, and migration by relieving G0/G1-S arrest, actin remodeling, and anoikis resistance in Cal27 cells. It enhanced tumor growth and liver metastasis in nude mice with the concomitant increase in metastasis-associated CD55 and CD61 expression. Inhibition of EMT and promotion of senescence by DOC2B is a calcium-dependent process and accompanied by calcium-mediated interaction between DOC2B and CDH1. In addition, we have identified several EMT and senescence regulators as targets of DOC2B. We show that DOC2B may act as a metastatic suppressor by inhibiting EMT through induction of senescence via DOC2B-calcium-EMT-senescence axis.

Wnt family member 4 (WNT4) and WNT3A activate cell-autonomous Wnt signaling independent of porcupine O-acyltransferase or Wnt secretion

Porcupine O-acyltransferase (PORCN) is considered essential for Wnt secretion and signaling. However, we observed that PORCN inhibition does not phenocopy the effects of WNT4 knockdown in WNT4-dependent breast cancer cells. This suggests a unique relationship between PORCN and WNT4 signaling. To examine the role of PORCN in WNT4 signaling, here we overexpressed WNT4 or WNT3A in breast cancer, ovarian cancer, and fibrosarcoma cell lines. Conditioned media from these lines and co-culture systems were used to assess the dependence of Wnt secretion and activity on the critical Wnt secretion proteins PORCN and Wnt ligand secretion (WLS) mediator. We observed that WLS is universally required for Wnt secretion and paracrine signaling. In contrast, the dependence of WNT3A secretion and activity on PORCN varied across the cell lines, and WNT4 secretion was PORCN-independent in all models. Surprisingly, WNT4 did not exhibit paracrine activity in any tested context. Absent the expected paracrine activity of secreted WNT4, we identified cell-autonomous Wnt signaling activation by WNT4 and WNT3A, independent of PORCN or Wnt secretion. The PORCN-independent, cell-autonomous Wnt signaling demonstrated here may be critical in WNT4-driven cellular contexts or in those that are considered to have dysfunctional Wnt signaling.

Mechanisms of synovial joint and articular cartilage development

Articular cartilage is formed at the end of epiphyses in the synovial joint cavity and permanently contributes to the smooth movement of synovial joints. Most skeletal elements develop from transient cartilage by a biological process known as endochondral ossification. Accumulating evidence indicates that articular and growth plate cartilage are derived from different cell sources and that different molecules and signaling pathways regulate these two kinds of cartilage. As the first sign of joint development, the interzone emerges at the presumptive joint site within a pre-cartilage tissue. After that, joint cavitation occurs in the center of the interzone, and the cells in the interzone and its surroundings gradually form articular cartilage and the synovial joint. During joint development, the interzone cells continuously migrate out to the epiphyseal cartilage and the surrounding cells influx into the joint region. These complicated phenomena are regulated by various molecules and signaling pathways, including GDF5, Wnt, IHH, PTHrP, BMP, TGF-β, and FGF. Here, we summarize current literature and discuss the molecular mechanisms underlying joint formation and articular development.

Autologous activated platelet-rich plasma injection into adult human ovary tissue: molecular mechanism, analysis, and discussion of reproductive response

In clinical infertility practice, one intractable problem is low (or absent) ovarian reserve which in turn reflects the natural oocyte depletion associated with advancing maternal age. The number of available eggs has been generally thought to be finite and strictly limited, an entrenched and largely unchallenged tenet dating back more than 50 years. In the past decade, it has been suggested that renewable ovarian germline stem cells (GSCs) exist in adults, and that such cells may be utilized as an oocyte source for women seeking to extend fertility. Currently, the issue of whether mammalian females possess such a population of renewable GSCs remains unsettled. The topic is complex and even agreement on a definitive approach to verify the process of 'ovarian rescue' or 're-potentiation' has been elusive. Similarities have been noted between wound healing and ovarian tissue repair following capsule rupture at ovulation. In addition, molecular signaling events which might be necessary to reverse the effects of reproductive ageing seem congruent with changes occurring in tissue injury responses elsewhere. Recently, clinical experience with such a technique based on autologous activated platelet-rich plasma (PRP) treatment of the adult human ovary has been reported. This review summarizes the present state of understanding of the interaction of platelet-derived growth factors with adult ovarian tissue, and the outcome of human reproductive potential following PRP treatment.

The Zinc Finger Transcription Factor PLAGL2 Enhances Stem Cell Fate and Activates Expression of ASCL2 in Intestinal Epithelial Cells

Intestinal epithelial stem cell (IESC) fate is promoted by two major transcriptional regulators, the TCF4/β-catenin complex and ASCL2, which drive expression of IESC-specific factors, including Lgr5, Ephb2, and Rnf43. Canonical Wnt signaling via TCF4/β-catenin directly transactivates Ascl2, which in turn auto-regulates its own expression. Conversely, Let-7 microRNAs antagonize the IESC lineage by repressing specific mRNA targets. Here, we identify the zinc finger transcription factor PLAGL2 as a Let-7 target that regulates IESC fate. PLAGL2 drives an IESC expression signature, activates Wnt gene expression, and enhances a TCF/LEF reporter in intestinal organoids. In parallel, via cell-autonomous mechanisms, PLAGL2 is required for lineage clonal expansion and directly enhances expression of ASCL2. PLAGL2 also supports enteroid growth and survival in the context of Wnt ligand depletion. PLAGL2 expression is strongly associated with an IESC signature in colorectal cancer and may be responsible for contributing to the aberrant activation of an immature phenotype.

Up-regulation of Wnt/β-catenin expression is accompanied with vascular repair after traumatic brain injury

Recent data suggest that repairing the cerebral vasculature after traumatic brain injury (TBI) may help to improve functional recovery. The Wnt/β-catenin signaling pathway promotes blood vessel formation during vascular development, but its role in vascular repair after TBI remains elusive. In this study, we examined how the cerebral vasculature responds to TBI and the role of Wnt/β-catenin signaling in vascular repair. We induced a moderate controlled cortical impact in adult mice and performed vessel painting to visualize the vascular alterations in the brain. Brain tissue around the injury site was assessed for β-catenin and vascular markers. A Wnt transgenic mouse line was utilized to evaluate Wnt gene expression. We report that TBI results in vascular loss followed by increases in vascular structure at seven days post injury (dpi). Immature, non-perfusing vessels were evident in the tissue around the injury site. β-catenin protein expression was significantly reduced in the injury site at 7 dpi. However, there was an increase in β-catenin expression in perilesional vessels at 1 and 7 dpi. Similarly, we found increased number of Wnt-GFP-positive vessels after TBI. Our findings suggest that Wnt/β-catenin expression contributes to the vascular repair process after TBI.

Gonadal soma controls ovarian follicle proliferation through Gsdf in zebrafish

BACKGROUND

Aberrant signaling between germ cells and somatic cells can lead to reproductive disease and depends on diffusible signals, including transforming growth factor-beta (TGFB) -family proteins. The TGFB-family protein Gsdf (gonadal soma derived factor) controls sex determination in some fish and is a candidate for mediating germ cell/soma signaling.

RESULTS

Zebrafish expressed gsdf in somatic cells of bipotential gonads and expression continued in ovarian granulosa cells and testicular Sertoli cells. Homozygous gsdf knockout mutants delayed leaving the bipotential gonad state, but then became a male or a female. Mutant females ovulated a few oocytes, then became sterile, accumulating immature follicles. Female mutants stored excess lipid and down-regulated aromatase, gata4, insulin receptor, estrogen receptor, and genes for lipid metabolism, vitellogenin, and steroid biosynthesis. Mutant females contained less estrogen and more androgen than wild-types. Mutant males were fertile. Genomic analysis suggests that Gsdf, Bmp15, and Gdf9, originated as paralogs in vertebrate genome duplication events.

CONCLUSIONS

In zebrafish, gsdf regulates ovarian follicle maturation and expression of genes for steroid biosynthesis, obesity, diabetes, and female fertility, leading to ovarian and extra-ovarian phenotypes that mimic human polycystic ovarian syndrome (PCOS), suggesting a role for a related TGFB signaling molecule in the etiology of PCOS. Developmental Dynamics 246:925-945, 2017. © 2017 Wiley Periodicals, Inc.

A Daple-Akt feed-forward loop enhances noncanonical Wnt signals by compartmentalizing β-catenin

Balance between canonical and noncanonical Wnt pathways controls the β-catenin transcriptional program; how the noncanonical pathway antagonizes the canonical pathway remains unclear. We show that Daple, an enhancer of noncanonical Wnt signals, accomplishes that goal by dictating the subcellular distribution of β-catenin in cells.

Cellular proliferation is antagonistically regulated by canonical and noncanonical Wnt signals; their dysbalance triggers cancers. We previously showed that a multimodular signal transducer, Daple, enhances PI3-K→Akt signals within the noncanonical Wnt signaling pathway and antagonistically inhibits canonical Wnt responses. Here we demonstrate that the PI3-K→Akt pathway serves as a positive feedback loop that further enhances noncanonical Wnt signals by compartmentalizing β-catenin. By phosphorylating the phosphoinositide- (PI) binding domain of Daple, Akt abolishes Daple’s ability to bind PI3-P-enriched endosomes that engage dynein motor complex for long-distance trafficking of β-catenin/E-cadherin complexes to pericentriolar recycling endosomes (PCREs). Phosphorylation compartmentalizes Daple/β-catenin/E-cadherin complexes to cell–cell contact sites, enhances noncanonical Wnt signals, and thereby suppresses colony growth. Dephosphorylation compartmentalizes β-catenin on PCREs, a specialized compartment for prolonged unopposed canonical Wnt signaling, and enhances colony growth. Cancer-associated Daple mutants that are insensitive to Akt mimic a constitutively dephosphorylated state. This work not only identifies Daple as a platform for cross-talk between Akt and the noncanonical Wnt pathway but also reveals the impact of such cross-talk on tumor cell phenotypes that are critical for cancer initiation and progression.

Modulation of Wnt signaling is essential for the differentiation of ciliated epithelial cells in human airways

Wnt signaling is essential for the differentiation of airway epithelial cells during development. Here, we examined the role of Wnt signaling during redifferentiation of ciliated airway epithelial cells in vitro at the air liquid interface as a model of airway epithelial repair. Phases of proliferation and differentiation were defined. Markers of squamous metaplasia and epithelial ciliation were followed while enhancing β‐catenin signaling by blocking glycogen synthase kinase 3β with SB216763 and shRNA as well as inhibiting canonical WNT signaling with apical application of Dickkopf 1 (Dkk1). Our findings indicate that enhanced β‐catenin signaling decreases the number of ciliated cells and causes squamous changes in the epithelium, whereas treatment with DDk1 leads to an increased number of ciliated cells.

Wnt Signaling in Chronic Rhinosinusitis with Nasal Polyps

The signaling pathways that sustain the disease process of chronic rhinosinusitis with nasal polyps (CRSwNP) remain poorly understood. We sought to determine the expression levels of Wnt signaling genes in CRSwNP and to study the role of the Wnt pathway in inflammation and epithelial remodeling in the nasal mucosa. Microarrays and real time-quantitative polymerase chain reaction comparing gene expression in matched NPs and inferior turbinates revealed that WNT2B, WNT3A, WNT4, WNT7A, WNT7B, and FZD2 were up-regulated and that FZD1, LRP5, LRP6, and WIF1 were down-regulated in NPs. Immunolabeling showed robust expression of Wnt ligands, nuclear β-catenin, and Axin-2 in NP tissue, suggesting that Wnt/β-catenin signaling is activated in NPs. We used primary human nasal epithelial cell (HNEpC) cultures to test the functional consequences of Wnt pathway activation. Monolayer HNEpCs treated with recombinant human WNT (rhWNT) 3A, but not with rhWNT4, had altered epithelial morphology and decreased adhesion, without loss of viability. We found that neither rhWNT3A nor rhWNT4 treatment induced proliferation. The expression and release of inflammatory cytokines IL-6 and granulocyte-macrophage colony-stimulating factor were increased after rhWNT3A exposure of HNEpCs. When differentiated at an air-liquid interface, rhWNT3A- and WNT agonist-, but not rhWNT4-treated HNEpCs, had abnormal epithelial architecture, failed to undergo motile ciliogenesis, and had defective noncanonical Wnt (planar cell polarity) signaling. On the basis of these results, we propose a model in which Wnt/β-catenin signaling sustains mucosal inflammation and leads to a spectrum of changes consistent with those seen during epithelial remodeling in NPs.

Type XVII collagen coordinates proliferation in the interfollicular epidermis

Type XVII collagen (COL17) is a transmembrane protein located at the epidermal basement membrane zone. COL17 deficiency results in premature hair aging phenotypes and in junctional epidermolysis bullosa. Here, we show that COL17 plays a central role in regulating interfollicular epidermis (IFE) proliferation. Loss of COL17 leads to transient IFE hypertrophy in neonatal mice owing to aberrant Wnt signaling. The replenishment of COL17 in the neonatal epidermis of COL17-null mice reverses the proliferative IFE phenotype and the altered Wnt signaling. Physical aging abolishes membranous COL17 in IFE basal cells because of inactive atypical protein kinase C signaling and also induces epidermal hyperproliferation. The overexpression of human COL17 in aged mouse epidermis suppresses IFE hypertrophy. These findings demonstrate that COL17 governs IFE proliferation of neonatal and aged skin in distinct ways. Our study indicates that COL17 could be an important target of anti-aging strategies in the skin.

The Interplay between Defensins and Microbiota in Crohn's Disease

Crohn's disease (CD) is a chronic inflammation of the intestinal mucosa, characterized by periods of acute recurrence and remission. Depending on the specific region affected, CD is classified as ileal CD or colonic CD. It is largely accepted that the intestinal microbiota is involved in the onset of the pathology. Indeed, a reduced immune tolerance to components of the intestinal commensal microbiota and inflammation of the intestinal barrier typifies patients with CD. Several studies have shown defective expression of intestinal antimicrobial peptides (AMPs) in patients with CD compared to controls, particularly defensins. A reduction in α-defensins is observed in ileal CD, while β-defensins are increased in colonic CD. In addition to an immunological basis, the disease is frequently associated with genetic alterations including mutations of NOD2 gene. Several therapeutic strategies to circumvent the dysfunction observed in CD are currently under investigation. These include the use of delivery systems to administer endogenous AMPs and the engineering of peptidomimetics that could ameliorate the severity of CD. In this review, the role defensins play in CD and the strategies aimed at overcoming bacterial resistance will be discussed.

The Battle of the Sexes: Human Sex Development and Its Disorders

The process of sexual differentiation is central for reproduction of almost all metazoan and therefore for maintenance of practically all multicellular organisms. In sex development we can distinguish two different processes: First, sex determination is the developmental decision that directs the undifferentiated embryo into a sexually dimorphic individual. In mammals, sex determination equals gonadal development. The second process known as sex differentiation takes place once the sex determination decision has been made through factors produced by the gonads that determine the development of the phenotypic sex. Most of the knowledge on the factors involved in sexual development came from animal models and from studies of cases in whom the genetic or the gonadal sex does not match the phenotypical sex, i.e., patients affected by disorders of sex development (DSD). Generally speaking, factors influencing sex determination are transcriptional regulators, whereas factors important for sex differentiation are secreted hormones and their receptors. This review focuses on the factors involved in gonadal determination, and whenever possible, references on the "prismatic" clinical cases are given.

Bisleuconothine A, a bisindole alkaloid, inhibits colorectal cancer cell in vitro and in vivo targeting Wnt signaling

Wnt signaling pathway is aberrantly activated in a variety of cancers, especially in colorectal cancer and small molecule antagonists of Wnt/β-catenin signaling are attractive candidates for developing effective therapeutics. In the present study, we identified Bisleuconothine A, a bisindole alkaloid with an eburnane-aspidosperma type skeleton, as a novel and selective Wnt signaling inhibitor by using a cell-based luciferase assay system. Our study found that Bisleuconothine A down-regulated the endogenous Wnt target gene expression through promoting phosphorylation of β-catenin and the subsequent inhibition of its nuclear translocation in HCT116 and SW480 colorectal cancer cells. In vitro, Bisleuconothine A inhibited cell proliferation through induction of apoptosis by increasing the cleavage of caspases in HCT116 and SW480 colorectal cancer cells. Moreover, in vivo, Bisleuconothine A dramatically suppressed tumor growth in HCT116 Xenograft. And further analysis showed that Bisleuconothine A suppressed the Wnt target gene expression in HCT116 Xenograft, which was associated with up-regulation of β-catenin phosphorylation and subsequent Wnt signaling inhibition. Taken together, our study indicated that bisindole alkaloids could be included as a new chemotype of small-molecule Wnt signaling inhibitors, and have great potential to be further developed for anti-tumor agents.

Wnt4 antagonises Wnt3a mediated increases in growth and glucose stimulated insulin secretion in the pancreatic beta-cell line, INS-1

The Wnt signalling pathway in beta-cells has been linked to the development of type 2 diabetes. Investigating the impact of a non-canonical Wnt ligand, Wnt4, on beta-cell function we found that in INS-1 cells, Wnt4 was able to completely block Wnt3a stimulated cell growth and insulin secretion. However, despite high levels of Wnt4 protein being detected in INS-1 cells, reducing the expression of Wnt4 had no impact on cell growth or Wnt3a signalling. As such, the role of the endogenously expressed Wnt4 in beta-cells is unclear, but the data showing that Wnt4 can act as a negative regulator of canonical Wnt signalling in beta-cells suggests that this pathway could be a potential target for modulating beta-cell function.

Adipose- and muscle-derived Wnts trigger pancreatic β-cell adaptation to systemic insulin resistance

Wnt signaling molecules are associated with obesity, hyperlipidemia, and type 2 diabetes (T2D). Here, we show that two Wnt proteins, WNT3a and WNT4, are specifically secreted by skeletal muscle and adipose tissue during the development of insulin resistance and play an important role in cross-talk between insulin-resistant tissues and pancreatic beta cells. The activation of Frizzled receptor and Wnt signaling in pancreatic islets via circulating WNT3a in blood resulted in higher insulin secretion and an increase in beta cell proliferation, thus leading to islet adaptation in a pre-diabetic state. Interestingly, in fully developed T2D, the expression profiles of Wnt3a and Wnt4 in adipose tissue and muscle cells and blood plasma levels of these proteins were opposite to the pre-diabetic state, thus favoring the downregulation of Wnt signaling in beta cells and resulting in dysfunctional pancreatic islets. These results demonstrate that alterations in the secretion profile of a canonical Wnt activator (WNT3a) and inhibitor (WNT4) from insulin-resistant tissues during the development of T2D are responsible for triggering progression from a pre-diabetic to a diabetic state. We also show here that WNT3a and WNT4 are potent myokines, and their expression and secretion are regulated in response to nutritional and metabolic changes.

Glucagon Like Peptide-1 Promotes Adipocyte Differentiation via the Wnt4 Mediated Sequestering of Beta-Catenin

Glucagon-like peptide-1 (GLP-1) plays a role in the regulation of adipogenesis; however, the precise underlying molecular mechanism has not been fully defined. Wnt was recently identified as an important regulator of adipogenesis. This study aimed to investigate the involvement of the Wnt signaling pathway in the effects of GLP-1 on adipocyte differentiation. 3T3-L1 cells were induced to differentiate. The changes in the expression levels of adipogenic transcription factors and Wnts and the phosphorylation level and subcellular localization of β-catenin were quantified after GLP-1 treatment. GLP-1 stimulated adipocyte differentiation and lipid accumulation, which were accompanied by the expression of adipocyte marker genes. The expression of Wnt4 was upregulated in the process of adipocyte differentiation, which was further enhanced by treatment with GLP-1. β-catenin, an important mediator of the Wnt pathway, was immediately dephosphorylated and translocated from cytoplasm to nucleus when differentiation was induced. In the presence of GLP-1, however, β-catenin was redirected to the cell plasma membrane leading to its decreased accumulation in the nucleus. Knockdown of Wnt4 blocked the effect of GLP-1 on the cellular localization of β-catenin and expression level of adipogenic transcription factors. Our findings showed that GLP-1 promoted adipogenesis through the modulation of the Wnt4/β-catenin signaling pathway, suggesting that the GLP-1-Wntβ-catenin system might be a new target for the treatment of metabolic disease.

WNT4 mediates the autocrine effects of growth hormone in mammary carcinoma cells

The expression of Wingless and Int-related protein (Wnt) ligands is aberrantly high in human breast cancer. We report here that WNT4 is significantly upregulated at the mRNA and protein level in mammary carcinoma cells expressing autocrine human growth hormone (hGH). Depletion of WNT4 using small interfering (si) RNA markedly decreased the rate of human breast cancer cell proliferation induced by autocrine hGH. Forced expression of WNT4 in the nonmalignant human mammary epithelial cell line MCF-12A stimulated cell proliferation in low and normal serum conditions, enhanced cell survival and promoted anchorage-independent growth and colony formation in soft agar. The effects of sustained production of WNT4 were concomitant with upregulation of proliferative markers (c-Myc, Cyclin D1), the survival marker BCL-XL, the putative WNT4 receptor FZD6 and activation of ERK1 and STAT3. Forced expression of WNT4 resulted in phenotypic conversion of MCF-12A cells, such that they exhibited the molecular and morphological characteristics of mesenchymal cells with increased cell motility. WNT4 production resulted in increased mesenchymal and cytoskeletal remodeling markers, promoted actin cytoskeleton reorganization and led to dissolution of cell-cell contacts. In xenograft studies, tumors with autocrine hGH expressed higher levels of WNT4 and FZD6 when compared with control tumors. In addition, Oncomine data indicated that WNT4 expression is increased in neoplastic compared with normal human breast tissue. Accordingly, immunohistochemical detection of WNT4 in human breast cancer biopsies revealed higher expression in tumor tissue vs normal breast epithelium. WNT4 is thus an autocrine hGH-regulated gene involved in the growth and development of the tumorigenic phenotype.

Variation at 2q35 (PNKD and TMBIM1) influences colorectal cancer risk and identifies a pleiotropic effect with inflammatory bowel disease

To identify new risk loci for colorectal cancer (CRC), we conducted a meta-analysis of seven genome-wide association studies (GWAS) with independent replication, totalling 13 656 CRC cases and 21 667 controls of European ancestry. The combined analysis identified a new risk association for CRC at 2q35 marked by rs992157 (P = 3.15 × 10-8, odds ratio = 1.10, 95% confidence interval = 1.06-1.13), which is intronic to PNKD (paroxysmal non-kinesigenic dyskinesia) and TMBIM1 (transmembrane BAX inhibitor motif containing 1). Intriguingly this susceptibility single-nucleotide polymorphism (SNP) is in strong linkage disequilibrium (r2 = 0.90, D' = 0.96) with the previously discovered GWAS SNP rs2382817 for inflammatory bowel disease (IBD). Following on from this observation we examined for pleiotropy, or shared genetic susceptibility, between CRC and the 200 established IBD risk loci, identifying an additional 11 significant associations (false discovery rate [FDR]) < 0.05). Our findings provide further insight into the biological basis of inherited genetic susceptibility to CRC, and identify risk factors that may influence the development of both CRC and IBD.

WNT4-like protein is a cortical granule component in mouse oocytes and functions in regulating preimplantation embryogenesis

Mammalian cortical granules (CG) are membrane-bound organelles located in the cortex of the unfertilized oocytes. Upon fertilization, CG undergo exocytosis to function in blocking polyspermy. While cortical granules are important in fertilization, their exact biochemical composition and reproductive function have not been fully defined. In the present study, a 66 kDa wingless-type MMTV integration site family, member 4 (WNT4)-like protein, with mouse CG origin was identified. Oocytes that were double labeled with lectin Lens culinaris agglutinin (LCA) and WNT4 antibody showed colocalization of the WNT4 molecules and cortical granules. The disappearance of WNT4 molecules in the artificially activated oocytes that were devoid of cortical granules confirmed their granule origin. Following fertilization, WNT4 remained associated with zygotes and blastomeres of 2-cell and 8-cell embryos; however the amount of protein present was reduced more than 2-fold as embryos developed. Prior to implantation, WNT4 appeared to be detectable only in the trophoblast cells. Our functional study revealed that WNT4 molecules were involved in regulating zygotic cleavage and early embryogenesis. To our knowledge, this is the first study demonstrating mammalian cortical granules contain signaling molecules that are involved in the regulation of the first phase of embryonic development.

Crosstalk between SOXB1 proteins and WNT/β-catenin signaling in NT2/D1 cells

During early vertebrate embryogenesis, the expression of SOXB1 proteins is precisely regulated by a number of different mechanisms, including Wnt/β-catenin signaling. This is essential for controlling the balance between stemness and differentiation in embryonic stem cells. In the present study, we analyzed the molecular mechanism of LiCl action in NT2/D1 cells and examined the crosstalk between SOXB1 proteins and Wnt signaling in this model system. We have shown that LiCl increases β-catenin level, induces its translocation to the nucleus and consequently up-regulates β-catenin/Tcf-dependent transcription in NT2/D1 cells. Our results also suggest that LiCl treatment leads to increased expression of SOX2 and SOX3 proteins in NT2/D1 cells through activation of canonical Wnt signaling. Finally, we have detected a negative feedback loop between β-catenin and SOX2 expression in NT2/D1 cells. Since β-catenin and SOX2 have been linked to processes of self-renewal and pluripotency, our results have implications for future research on the maintenance of stemness and lineage commitment of embryonic stem cells.

Stem cells, progenitor cells, and lineage decisions in the ovary

Exploring stem cells in the mammalian ovary has unleashed a Pandora's box of new insights and questions. Recent evidence supports the existence of stem cells of a number of the different cell types within the ovary. The evidence for a stem cell model producing mural granulosa cells and cumulus cells is strong, despite a limited number of reports. The recent identification of a precursor granulosa cell, the gonadal ridge epithelial-like cell, is exciting and novel. The identification of female germline (oogonial) stem cells is still very new and is currently limited to just a few species. Their origins and physiological roles, if any, are unknown, and their potential to produce oocytes and contribute to follicle formation in vivo lacks robust evidence. The precursor of thecal cells remains elusive, and more compelling data are needed. Similarly, claims of very small embryonic-like cells are also preliminary. Surface epithelial cells originating from gonadal ridge epithelial-like cells and from the mesonephric epithelium at the hilum of the ovary have also been proposed. Another important issue is the role of the stroma in guiding the formation of the ovary, ovigerous cords, follicles, and surface epithelium. Immune cells may also play key roles in developmental patterning, given their critical roles in corpora lutea formation and regression. Thus, while the cellular biology of the ovary is extremely important for its major endocrine and fertility roles, there is much still to be discovered. This review draws together the current evidence and perspectives on this topic.

The hemodynamically-regulated vascular microenvironment promotes migration of the steroidogenic tissue during its interaction with chromaffin cells in the zebrafish embryo

Background

While the endothelium-organ interaction is critical for regulating cellular behaviors during development and disease, the role of blood flow in these processes is only partially understood. The dorsal aorta performs paracrine functions for the timely migration and differentiation of the sympatho-adrenal system. However, it is unclear how the adrenal cortex and medulla achieve and maintain specific integration and whether hemodynamic forces play a role.

Methodology and Principal Findings

In this study, the possible modulation of steroidogenic and chromaffin cell integration by blood flow was investigated in the teleostean counterpart of the adrenal gland, the interrenal gland, in the zebrafish (Danio rerio). Steroidogenic tissue migration and angiogenesis were suppressed by genetic or pharmacologic inhibition of blood flow, and enhanced by acceleration of blood flow upon norepinephrine treatment. Repressed steroidogenic tissue migration and angiogenesis due to flow deficiency were recoverable following restoration of flow. The regulation of interrenal morphogenesis by blood flow was found to be mediated through the vascular microenvironment and the Fibronectin-phosphorylated Focal Adhesion Kinase (Fn-pFak) signaling. Moreover, the knockdown of krüppel-like factor 2a (klf2a) or matrix metalloproteinase 2 (mmp2), two genes regulated by the hemodynamic force, phenocopied the defects in migration, angiogenesis, the vascular microenvironment, and pFak signaling of the steroidogenic tissue observed in flow-deficient embryos, indicating a direct requirement of mechanotransduction in these processes. Interestingly, epithelial-type steroidogenic cells assumed a mesenchymal-like character and downregulated β-Catenin at cell-cell junctions during interaction with chromaffin cells, which was reversed by inhibiting blood flow or Fn-pFak signaling. Blood flow obstruction also affected the migration of chromaffin cells, but not through mechanosensitive or Fn-pFak dependent mechanisms.

Conclusions and Significance

These results demonstrate that hemodynamically regulated Fn-pFak signaling promotes the migration of steroidogenic cells, ensuring their interaction with chromaffin cells along both sides of the midline during interrenal gland development.

Concentration-dependent effects of WNTLESS on WNT1/3A signaling

BACKGROUND

WNTLESS (WLS) is a multi-transmembrane protein that transports Wnt ligands from the Golgi to the cell surface. Although WLS loss-of-function experiments in the developing central nervous system reveal phenotypes consistent with defects in WNT1 and WNT3A signaling, data from complementary gain-of-function experiments have not yet been reported. Here, we report the phenotypic consequences of WLS overexpression in cultured cells and in the developing chick spinal cord.

RESULTS

Overexpression of small amounts of WLS along with either WNT1 or WNT3A promotes the Wnt/β-catenin pathway in HEK293T cells, while overexpression of higher levels of WLS inhibits the Wnt/β-catenin pathway in these cells. Similarly, overexpressed WLS inhibits the Wnt/β-catenin pathway in the developing spinal cord, as assessed by cell proliferation and specification. These effects appear to be Wnt-specific as overexpression of WLS inhibits the expression of FZD10, a target of β-catenin-dependent transcription.

CONCLUSIONS

Our results show that overexpression of WLS inhibits Wnt/β-catenin signaling in the spinal cord. As the activation of the Wnt/β-catenin pathway in the spinal cord requires WNT1 or WNT3A, our results are consistent with a model in which the relative concentration of WLS to Wnt regulates WNT1/3A signaling in the developing spinal cord.

Exposure of fathead minnows to municipal wastewater effluent affects intracellular signaling pathways in the liver

Municipal wastewater effluent can impact its receiving environment. In the St. Lawrence River, male fish living downstream from Montreal exhibit increased hepatic vitellogenin, intersex, delayed spermatogenesis and altered immune function. Few studies have examined genome-wide effects associated with municipal effluent exposure in fish to decipher the mechanisms of toxicity. The present objective was to identify hepatic cellular signaling pathways in fathead minnows following exposure to municipal wastewater effluent. Immature minnows were exposed for 21 days to either 0% (Control) or 20% municipal effluent, the highest concentration in the St. Lawrence River. Hepatic RNA was extracted and used to hybridize a fathead minnow oligonucleotide microarray containing approximately 15k gene sequences. A total of 1300 genes were differentially expressed, of which 309 genes had more than 2-fold change in expression level between control and MWWE-exposed fish. Of those, 118 were up-regulated and 191 were down-regulated. Altered genes grouped according to function, indicated effects on various signaling pathways, apoptosis, immune responses, and cellular metabolism. Pathway analysis software predicted at least 5 signaling pathways that were altered by treatment: cell adhesion, inflammation, various kinases, estrogen receptor signaling and WNT signaling. Various components of the canonical Wnt pathway were dramatically down-regulated, while several other genes involved in the non-canonical Wnt pathway, such as Wnt4, LRP6, and PPP2R5E, which are known to inhibit the canonical Wnt pathway, were increased. These results indicate that municipal wastewater effluent from Montreal can target and inhibit various signaling including those implicated in hepatic Wnt signaling pathway in fathead minnows.

Melanoma Development and Progression Are Associated with Rad6 Upregulation and β -Catenin Relocation to the Cell Membrane

We have previously demonstrated that Rad6 and β -catenin enhance each other's expression through a positive feedback loop to promote breast cancer development/progression. While β -catenin has been implicated in melanoma pathogenesis, Rad6 function has not been investigated. Here, we examined the relationship between Rad6 and β -catenin in melanoma development and progression. Eighty-eight cutaneous tumors, 30 nevi, 29 primary melanoma, and 29 metastatic melanomas, were immunostained with anti- β -catenin and anti-Rad6 antibodies. Strong expression of Rad6 was observed in only 27% of nevi as compared to 100% of primary and 96% of metastatic melanomas. β -Catenin was strongly expressed in 97% of primary and 93% of metastatic melanomas, and unlike Rad6, in 93% of nevi. None of the tumors expressed nuclear β -catenin. β -Catenin was exclusively localized on the cell membrane of 55% of primary, 62% of metastatic melanomas, and only 10% of nevi. Cytoplasmic β -catenin was detected in 90% of nevi, 17% of primary, and 8% of metastatic melanoma, whereas 28% of primary and 30% of metastatic melanomas exhibited β -catenin at both locations. These data suggest that melanoma development and progression are associated with Rad6 upregulation and membranous redistribution of β -catenin and that β -catenin and Rad6 play independent roles in melanoma development.

Kindlin-1 controls Wnt and TGF-β availability to regulate cutaneous stem cell proliferation

Kindlin-1 is an integrin tail binding protein that controls integrin activation. Mutations in the FERMT-1 gene lead to Kindler Syndrome in man, which is characterized by skin blistering, premature skin ageing and skin cancer of unknown etiology. Here we show that loss of Kindlin-1 in mouse keratinocytes recapitulates Kindler Syndrome, and in addition produces enlarged and hyperactive stem cell compartments, which lead to hyperthickened epidermis, ectopic hair follicle development and increased skin tumor susceptibility. Mechanistically, Kindlin-1 controls keratinocyte adhesion through β₁-class integrins and proliferation and differentiation of cutaneous epithelial stem cells by promoting α_vβ₆ integrin-mediated TGFβ activation and by inhibiting Wnt-β-catenin signaling through an integrin-independent regulation of Wnt ligand expression. Our findings assign Kindlin-1 the novel and essential task to control cutaneous epithelial stem cell homeostasis by balancing TGFβ mediated growth inhibitory and Wnt-β-catenin mediated growth-promoting signals.

The WNT/β-catenin signaling pathway and expression of survival promoting genes in luteinized granulosa cells: endometriosis as a paradigm for a dysregulated apoptosis pathway

OBJECTIVE

To analyze the WNT/β-catenin signaling pathway in luteinized granulosa cells from women with and without endometriosis in relation to cellular apoptosis.

DESIGN

Basic.

SETTING

University hospital.

PATIENT(S)

Patients with a laparoscopic diagnosis of endometriosis (n = 30) and women undergoing intracytoplasmic sperm injection for male infertility (control group n = 39).

INTERVENTION(S)

Isolation of luteinized granulosa cells.

MAIN OUTCOME MEASURE(S)

Gene expression analysis of components of the WNT/β-catenin pathway, protein expression levels of β-catenin, and cell cycle studies in luteinized granulosa cells.

RESULT(S)

Compared with luteinized granulosa cells from control women, cells derived from endometriosis patients had significantly higher transcript levels of the β-catenin-independent molecules WNT4 and WNT5a and lower levels of the β-catenin-dependent molecule WNT1. A decrease of total β-catenin as well as of its dephosphorylated active form, together with an aberrant gene expression of the downstream targets survivin and BMP4, was detected in cells from affected women. Flow cytometry analysis confirmed an enhanced apoptosis of luteinized granulosa cells from patients with endometriosis.

CONCLUSION(S)

The concomitant dysregulation of specific members of the WNT pathway and of its pivot molecule β-catenin in granulosa cells characterized by an increased apoptosis suggests that the WNT/β-catenin signaling pathway might be involved in leading to granulosa cell atresia.

Restoration of WNT4 inhibits cell growth in leukemia-derived cell lines

Background

WNT signaling pathways are significantly altered during cancer development. Vertebrates possess two classes of WNT signaling pathways: the “canonical” WNT/β-catenin signaling pathway, and the “non-canonical” pathways including WNT/Ca2⁺ and WNT/Planar cell polarity [PCP] signaling. WNT4 influences hematopoietic progenitor cell expansion and survival; however, WNT4 function in cancer development and the resulting implications for oncogenesis are poorly understood.

The aim of this study was twofold: first, to determine the expression of WNT4 in mature peripheral blood cells and diverse leukemia-derived cells including cell lines from hematopoietic neoplasms and cells from patients with leukemia; second, to identify the effect of this ligand on the proliferation and apoptosis of the blast-derived cell lines BJAB, Jurkat, CEM, K562, and HL60.

Methods

We determined WNT4 expression by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) in peripheral blood mononuclear cells (PBMCs) and T- and B-lymphocytes from healthy individuals, as well as from five leukemia-derived cell lines and blasts derived from patients with leukemia. To analyze the effect of WNT4 on cell proliferation, PBMCs and cell lines were exposed to a commercially available WNT4 recombinant human protein. Furthermore, WNT4 expression was restored in BJAB cells using an inducible lentiviral expression system. Cell viability and proliferation were measured by the addition of WST-1 to cell cultures and counting cells; in addition, the progression of the cell cycle and the amount of apoptosis were analyzed in the absence or presence of WNT4. Finally, the expression of WNT-pathway target genes was measured by qRT-PCR.

Results

WNT4 expression was severely reduced in leukemia-derived cell lines and blasts derived from patients with leukemia. The exposure of cell lines to WNT4 recombinant protein significantly inhibited cell proliferation; inducing WNT4 expression in BJAB cells corroborated this observation. Interestingly, restoration of WNT4 expression in BJAB cells increased the accumulation of cells in G1 phase, and did not induce activation of canonical WNT/β-catenin target genes.

Conclusions

Our findings suggest that the WNT4 ligand plays a role in regulating the cell growth of leukemia-derived cells by arresting cells in the G1 cell cycle phase in an FZD6-independent manner, possibly through antagonizing the canonical WNT/β-catenin signaling pathway.

Interaction of Wnt Signaling with BMP/Smad Signaling during the Transition from Cell Proliferation to Myogenic Differentiation in Mouse Myoblast-Derived Cells

Background. Wnt signaling is involved in muscle formation through β-catenin-dependent or -independent pathways, but interactions with other signaling pathways including transforming growth factor β/Smad have not been precisely elucidated. Results. As Wnt4 stimulates myogenic differentiation by antagonizing myostatin (GDF8) activity, we examined the role of Wnt4 signaling during muscle differentiation in the C2C12 myoblast cell line. Among several extrinsic signaling molecules examined in a microarray analysis of C2C12 cells during the transition from cell proliferation to differentiation after mitogen deprivation, bone morphogenetic protein 4 (BMP4) expression was prominently increased. Wnt4 overexpression had similar effects on BMP4 expression. BMP4 was able to inhibit muscle differentiation when added to the culture medium. BMP4 and noggin had no effects on the cellular localization of β-catenin induced by Wnt3a; however, the BMP4-induced phosphorylation of Smad1/5/8 was enhanced by Wnt4, but not by Wnt3a. The BMP antagonist noggin effectively stimulated muscle differentiation through binding to endogenous BMPs, and the effect of noggin was enhanced by the presence of Wnt3a and Wnt4. Conclusion. These results suggest that BMP/Smad pathways are modified through Wnt signaling during the transition from progenitor cell proliferation to myogenic differentiation, although Wnt/β-catenin signaling is not modified with BMP/Smad signaling.

Wnt signaling during cochlear development

Wnt signaling is a hallmark of all embryonic development with multiple roles at multiple developmental time points. Wnt signaling is also important in the development of several organs, one of which is the inner ear, where it participates in otic specification, the formation of vestibular structures, and the development of the cochlea. In particular, we focus on Wnt signaling in the auditory organ, the cochlea. Attempting to dissect the multiple Wnt signaling pathways in the mammalian cochlea is a challenging task due to limited expression data, particularly at proliferating stages. To offer predictions about Wnt activity, we compare cochlear development with that of other biological systems such as Xenopus retina, brain, cancer cells and osteoblasts. Wnts are likely to regulate development through crosstalk with other signaling pathways, particularly Notch and FGF, leading to changes in the expression of Sox2 and proneural (pro-hair cell) genes. In this review we have consolidated the known signaling pathways in the cochlea with known developmental roles of Wnts from other systems to generate a potential timeline of cochlear development.

Renal hypodysplasia associates with a WNT4 variant that causes aberrant canonical WNT signaling

Abnormal differentiation of the renal stem/progenitor pool into kidney tissue can lead to renal hypodysplasia (RHD), but the underlying causes of RHD are not well understood. In this multicenter study, we identified 20 Israeli pedigrees with isolated familial, nonsyndromic RHD and screened for mutations in candidate genes involved in kidney development, including PAX2, HNF1B, EYA1, SIX1, SIX2, SALL1, GDNF, WNT4, and WT1. In addition to previously reported RHD-causing genes, we found that two affected brothers were heterozygous for a missense variant in the WNT4 gene. Functional analysis of this variant revealed both antagonistic and agonistic canonical WNT stimuli, dependent on cell type. In HEK293 cells, WNT4 inhibited WNT3A induced canonical activation, and the WNT4 variant significantly enhanced this inhibition of the canonical WNT pathway. In contrast, in primary cultures of human fetal kidney cells, which maintain WNT activation and more closely represent WNT signaling in renal progenitors during nephrogenesis, this mutation caused significant loss of function, resulting in diminished canonical WNT/β-catenin signaling. In conclusion, heterozygous WNT4 variants are likely to play a causative role in renal hypodysplasia.

Regulation of Wnt4 in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is associated with persistent inflammation and oxidative stress in susceptible individuals. Using microarray analysis of bronchial biopsy samples from patients with COPD and controls, we identified Wnt4 as being up-regulated in COPD. Analysis of bronchial biopsy samples showed a very strong correlation between Wnt4 and IL8 gene expression, suggesting that Wnt4 plays a role in chronic lung inflammation. In vitro, Wnt4 induced proliferation and inflammation in human epithelial cells (BEAS-2B) and normal primary human bronchial epithelial cells in a concentration-dependent manner. This effect was enhanced in the presence of interleukin-1β (IL-1β) as a result of activation of the p38 and c-Jun NH2-terminal kinase mitogen-activated protein kinase pathways. Hydrogen peroxide, but not proinflammatory stimuli, up-regulated Wnt4 expression in epithelial cells. In monocytic THP-1 and primary airway smooth muscle cells, Wnt4 induced inflammation and enhanced the inflammatory response to lipopolysaccharide and IL-1β but did not induce proliferation. In addition, these other cell types did not have enhanced Wnt4 expression in response to hydrogen peroxide. Our results indicate that airway epithelial activation, due to oxidative stress, may lead to Wnt4 induction. Wnt4, in turn, acts through the noncanonical pathway to activate epithelial cell remodeling and IL8 gene expression, leading to neutrophil infiltration and inflammation.