Wnt Signaling Cascade Research Articles

Role of Sfrps in cardiovascular disease.

Secreted frizzled-related proteins (Sfrps) are a family of secreted proteins that bind extracellularly to Wnt ligands and frizzled receptors. This binding modulates the Wnt signaling cascade, and Sfrps interact with their corresponding receptors. Sfrps are thought to play an important role in the pathological mechanism of cardiac disease such as myocardial infarction, cardiac remodeling, and heart failure. However, the overall role of Sfrps in cardiac disease is unknown. Some members of the Sfrps family modulate cellular apoptosis, angiogenesis, differentiation, the inflammatory process, and cardiac remodeling. In this review, we summarize the evidence of Sfrps association with cardiac disease. We also discuss how multiple mechanisms may underlie Sfrps being involved in such diverse pathologies.

Wnt Signaling: Paths for Cancer Progression.

The Wnt signaling pathways are well known for having several pivotal roles during embryonic development. However, the same developmental signaling pathways also present key roles in cancer initiation and progression. In this chapter, several issues regarding the roles of both canonical and non-canonical Wnt signaling pathways in cancer will be explored, mainly concerning their role in the maintenance of cancer stemness, in the metabolism reprograming of cancer cells and in the modulation of the tumor microenvironment. The role of Wnt signaling cascades in the response of cancer cells to anti-cancer treatments will be also discussed, as well as its potential therapeutic targeting during cancer treatment. Collectively, increasing evidence has been supporting pivotal roles of Wnt signaling in several features of cancer biology, however; a lot is still to be elucidated.

The role of tumor budding in colorectal adenocarcinoma: Possible involvement of the intestinal cancer stem cell marker Lgr5.

Tumor budding (TB) is a promising prognostic factor in colorectal cancer (CRC) that is independent of tumor-node-metastasis (TNM) staging. Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) is a stem cell marker and a member of the canonical Wnt-signaling cascade. It is involved in colorectal carcinogenesis. However, its role in CRC progression and TB needs to be clarified. TB was assessed in both H and E and CK immunostained sections of 92 CRC cases. Associations between TB grade and different clinicopathological parameters were evaluated. Lgr5 expression in CRC cases and its association with TB grade and other clinicopathological features was also evaluated. H and E stained sections revealed low- and high-grade budding in 55 (59.8%) and 37 (40.2%) tumors, respectively, whereas Cytokeratin Immunohistochemistry (CK-IHC) showed low- and high-grade budding in 31 (33.7%) and 61 (66.3%) tumors, respectively. TB grade (in H and E and CK stained sections) was significantly associated with adverse pathological prognostic variables including vascular invasion (P = 0.03 and 0.001), lymph node metastasis (P = 0.001 and 0,001), advanced Dukes (P = 0.000 and 0.000), and TNM (P = 0.001 and 0.000) stages and inversely associated with Tumor infiltrating lymphocytes (TILS) (P = 0.02 and 0.0001) which is known to be a good prognostic indicator. Lgr5 protein was positively expressed in 52.2% (48/92) of the CRCs. Immunoreactivity of Lgr5 was significantly associated with histological grade (P = 0.01), lymph node metastasis (P = 0.002), vascular invasion (P = 0.02), TNM stage (P = 0.000), Dukes stage (P = 0.000), and TILS (P = 0.03). Furthermore, Lgr5 was found to be significantly associated with TB estimated in both H and E and CK stained tumors (P = 0.003 and 0.001 respectively). This study supported the relevance of TB in the assessment of CRC aggressiveness. It also revealed that Lgr5 expression is related to morphologic features in the invasive front of CRC. Lgr5 could have an important role in forming a morphologic feature at the invasive front associated with the aggressiveness of the tumor.

Gene variants of TCF7L2 are histopathologically important in colorectal cancers but do not have direct association with MYC expression

Rapidly accumulating preclinical and clinical studies have helped us to unveil underlying mechanisms of colorectal cancer development and progression. Deregulated signaling pathways play instrumental role in carcinogenesis, drug resistance and metastasis. Wnt signaling cascade has attracted considerable attention in colorectal cancer as many ground-breaking researches have highlighted central role of Wnt pathway in pathogenesis of colorectal cancer. T-Cell Transcription Factors (TCFs) have been shown to work synchronously with β-catenin to fuel colorectal cancer development and progression. Chromatin immuno-precipitation coupled with high-throughput sequencing (ChIP-Seq) data sets has deepened our knowledge about critical role of risk-associated SNPs. Increasingly it is being reported that many risk-associated SNPs are located within binding sites for transcription factors and consequently risk status of these SNPs may modify binding pattern of transcriptional factors and thus rewire the transcriptional regulation. DNA was extracted from peripheral blood samples of 117 colorectal cancer patients and 127 healthy subjects. TCF7L2 variants (rs6983267, rs7903146) were examined by the PCR-RFLP method. Tumor and the surrounding tissues were dissected from 37 CRC patients and RNA isolation was performed. The gene expression of c-myc was determined by RT-PCR. T allele carriage of rs6983267 variant was found to be associated with CRC (p=0.042). TT genotype of rs7903146 was associated with late tumor stage (T3+T4) (p=0.037) and presence of mucinous component (p=0.031). TTCT haplotype was found to be statistically higher in CRC compared to the control group (p=0.007). There was no statistically significant difference in c-myc gene expression. TCF7L2 gene variants may play an important role in histopathologic aspects associated with CRC and it is independent of c-myc gene expression.

Coactivation of Endogenous Wnt10b and Foxc2 by CRISPR Activation Enhances BMSC Osteogenesis and Promotes Calvarial Bone Regeneration.

CRISPR activation (CRISPRa) is a burgeoning technology for programmable gene activation, but its potential for tissue regeneration has yet to be fully explored. Bone marrow-derived mesenchymal stem cells (BMSCs) can differentiate into osteogenic or adipogenic pathways, which are governed by the Wnt (Wingless-related integration site) signaling cascade. To promote BMSC differentiation toward osteogenesis and improve calvarial bone healing by BMSCs, we harnessed a highly efficient hybrid baculovirus vector for gene delivery and exploited a synergistic activation mediator (SAM)-based CRISPRa system to activate Wnt10b (that triggers the canonical Wnt pathway) and forkhead c2 (Foxc2) (that elicits the noncanonical Wnt pathway) in BMSCs. We constructed a Bac-CRISPRa vector to deliver the SAM-based CRISPRa system into rat BMSCs. We showed that Bac-CRISPRa enabled CRISPRa delivery and potently activated endogenous Wnt10b and Foxc2 expression in BMSCs for >14days. Activation of Wnt10b or Foxc2 alone was sufficient to promote osteogenesis and repress adipogenesis invitro. Furthermore, the robust and prolonged coactivation of both Wnt10b and Foxc2 additively enhanced osteogenic differentiation while inhibiting adipogenic differentiation of BMSCs. The CRISPRa-engineered BMSCs with activated Wnt10b and Foxc2 remarkably improved the calvarial bone healing after implantation into the critical-sized calvarial defects in rats. These data implicate the potentials of CRISPRa technology for bone tissue regeneration.

Precision medicine for human cancers with Notch signaling dysregulation (Review).

NOTCH1, NOTCH2, NOTCH3 and NOTCH4 are transmembrane receptors that transduce juxtacrine signals of the delta-like canonical Notch ligand (DLL)1, DLL3, DLL4, jagged canonical Notch ligand (JAG)1 and JAG2. Canonical Notch signaling activates the transcription of BMI1 proto-oncogene polycomb ring finger, cyclin D1, CD44, cyclin dependent kinase inhibitor 1A, hes family bHLH transcription factor 1, hes related family bHLH transcription factor with YRPW motif 1, MYC, NOTCH3, RE1 silencing transcription factor and transcription factor 7 in a cellular context-dependent manner, while non-canonical Notch signaling activates NF-κB and Rac family small GTPase 1. Notch signaling is aberrantly activated in breast cancer, non-small-cell lung cancer and hematological malignancies, such as T-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma. However, Notch signaling is inactivated in small-cell lung cancer and squamous cell carcinomas. Loss-of-function NOTCH1 mutations are early events during esophageal tumorigenesis, whereas gain-of-function NOTCH1 mutations are late events during T-cell leukemogenesis and B-cell lymphomagenesis. Notch signaling cascades crosstalk with fibroblast growth factor and WNT signaling cascades in the tumor microenvironment to maintain cancer stem cells and remodel the tumor microenvironment. The Notch signaling network exerts oncogenic and tumor-suppressive effects in a cancer stage- or (sub)type-dependent manner. Small-molecule γ-secretase inhibitors (AL101, MRK-560, nirogacestat and others) and antibody-based biologics targeting Notch ligands or receptors [ABT-165, AMG 119, rovalpituzumab tesirine (Rova-T) and others] have been developed as investigational drugs. The DLL3-targeting antibody-drug conjugate (ADC) Rova-T, and DLL3-targeting chimeric antigen receptor-modified T cells (CAR-Ts), AMG 119, are promising anti-cancer therapeutics, as are other ADCs or CAR-Ts targeting tumor necrosis factor receptor superfamily member 17, CD19, CD22, CD30, CD79B, CD205, Claudin 18.2, fibroblast growth factor receptor (FGFR)2, FGFR3, receptor-type tyrosine-protein kinase FLT3, HER2, hepatocyte growth factor receptor, NECTIN4, inactive tyrosine-protein kinase 7, inactive tyrosine-protein kinase transmembrane receptor ROR1 and tumor-associated calcium signal transducer 2. ADCs and CAR-Ts could alter the therapeutic framework for refractory cancers, especially diffuse-type gastric cancer, ovarian cancer and pancreatic cancer with peritoneal dissemination. Phase III clinical trials of Rova-T for patients with small-cell lung cancer and a phase III clinical trial of nirogacestat for patients with desmoid tumors are ongoing. Integration of human intelligence, cognitive computing and explainable artificial intelligence is necessary to construct a Notch-related knowledge-base and optimize Notch-targeted therapy for patients with cancer.

Targeting signalling pathways and the immune microenvironment of cancer stem cells — a clinical update

Cancer stem cells (CSCs) have important roles in tumour development, relapse and metastasis; the intrinsic self-renewal characteristics and tumorigenic properties of these cells provide them with unique capabilities to resist diverse forms of anticancer therapy, seed recurrent tumours, and disseminate to and colonize distant tissues. The findings of several studies indicate that CSCs originate from non-malignant stem or progenitor cells. Accordingly, inhibition of developmental signalling pathways that are crucial for stem and progenitor cell homeostasis and function, such as the Notch, WNT, Hedgehog and Hippo signalling cascades, continues to be pursued across multiple cancer types as a strategy for targeting the CSCs hypothesized to drive cancer progression - with some success in certain malignancies. In addition, with the renaissance of anticancer immunotherapy, a better understanding of the interplay between CSCs and the tumour immune microenvironment might be the key to unlocking a new era of oncological treatments associated with a reduced propensity for the development of resistance and with enhanced antimetastatic activity, thus ultimately resulting in improved patient outcomes. Herein, we provide an update on the progress to date in the clinical development of therapeutics targeting the Notch, WNT, Hedgehog and Hippo pathways. We also discuss the interactions between CSCs and the immune system, including the potential immunological effects of agents targeting CSC-associated developmental signalling pathways, and provide an overview of the emerging approaches to CSC-targeted immunotherapy.

Wnt Signaling in Cancer: Not a Binary ON:OFF Switch.

In the March 1 issue of Cancer Research, we identified the Wnt receptor Fzd7 as an attractive therapeutic target for the treatment of gastric cancer. In summary, we showed that pharmacological inhibition of Wnt receptors, or genetic deletion of Fzd7, blocks the initiation and growth of gastric tumors. Inhibiting Fzd receptors, specifically Fzd7, inhibits the growth of gastric cancer cells even in the presence of adenomatous polyposis coli (Apc) mutation. Apc is located in the cytoplasm downstream of Fzd7 in the Wnt signaling cascade and APC mutations activate Wnt/β-catenin signaling, therefore, this result seems counterintuitive. Here, we analyze this result in greater detail in the context of current knowledge of Wnt signaling and discuss the wider implications of this aspect of Wnt signaling in other cancers.

Comparative phosphorylation map of Dishevelled 3 links phospho-signatures to biological outputs

BackgroundDishevelled (DVL) is an essential component of the Wnt signaling cascades. Function of DVL is controlled by phosphorylation but the molecular details are missing. DVL3 contains 131 serines and threonines whose phosphorylation generates complex barcodes underlying diverse DVL3 functions. In order to dissect the role of DVL phosphorylation we analyzed the phosphorylation of human DVL3 induced by previously reported (CK1ε, NEK2, PLK1, CK2α, RIPK4, PKCδ) and newly identified (TTBK2, Aurora A) DVL kinases.MethodsShotgun proteomics including TiO2 enrichment of phosphorylated peptides followed by liquid chromatography tandem mass spectrometry on immunoprecipitates from HEK293T cells was used to identify and quantify phosphorylation of DVL3 protein induced by 8 kinases. Functional characterization was performed by in-cell analysis of phospho-mimicking/non-phosphorylatable DVL3 mutants and supported by FRET assays and NMR spectroscopy.ResultsWe used quantitative mass spectrometry and calculated site occupancies and quantified phosphorylation of > 80 residues. Functional validation demonstrated the importance of CK1ε-induced phosphorylation of S268 and S311 for Wnt-3a-induced β-catenin activation. S630–643 cluster phosphorylation by CK1, NEK2 or TTBK2 is essential for even subcellular distribution of DVL3 when induced by CK1 and TTBK2 but not by NEK2. Further investigation showed that NEK2 utilizes a different mechanism to promote even localization of DVL3. NEK2 triggered phosphorylation of PDZ domain at S263 and S280 prevents binding of DVL C-terminus to PDZ and promotes an open conformation of DVL3 that is more prone to even subcellular localization.ConclusionsWe identify unique phosphorylation barcodes associated with DVL function. Our data provide an example of functional synergy between phosphorylation in structured domains and unstructured IDRs that together dictate the biological outcome.6BqYee6BDHWtLZWNZ_gBTSVideo Abtract.Graphical abstract

Targeting WNT10B-Driven Signalling through Induction of FZD6 By Porcupine Inhibition in T Cell Acute Lymphoblastic Leukemia

Background Wnt/Fzd signaling is known to play a pervasive influence in hematopoietic stem cell maintenance, T-cell development in the thymus and function as well as an important role in T-cell acute lymphoblastic leukemia (T-ALL) establishment. We have previously described a recurrent rearrangement involving the WNT10Blocus (WNT10BR) expressing a transcript variant (WNT10BIVS1) in acute myeloid leukemia. To determine the occurrence of this rearrangement in T-ALL we analyzed retrospectively an italian cohort of patients (n=20) and detected the WNT10BRrearrangement with a high prevalence (14/20). We also confirmed the relevance of these findings to human disease, detecting the molecular circuit triggered by the WNT10B over-expression using the MOLT-4 T-ALL cell model.In this report, we examined the expression of components of the Wnt signaling cascade mediated by WNT10B and the effects of specific gene silencing by short hairpin RNA (shRNA) and exposure to the potent PORCN inhibitor (LGK974), or the TGFbRI inhibitor (A83-01) on the WNT10B-mediated Wnt signaling activation. Methods We used the T-ALL model MOLT-4 cell line to assess the WNT10B/FZD signaling axis driven by WNT10BR. In order to identify interaction between WNT10B and FZD receptors we performed in situ proximity ligation assay (PLA) a method used to visualize protein-protein interactions.MOLT4 cells were infected with WNT10B/WNT10BIVS1-shRNA silencing lentiviral vectors versus empty vector control and treated with increased concentration of LGK974 or A83-01, subsequently the effects of pharmacological inhibition on the WNT10B/FZD interactions and on Wnt effector proteins were evaluated by PLA and expression analyses. Cell proliferation and cell death were measured by EdU assay and Annexin-V/Propidium Iodide (PI) analyses. Results We found that WNT10BRdrives Wnt signaling activity in T-ALL through interaction of WNT10B with FZD6 receptor. The effects of WNT10B/FZD6 interaction on Wnt-mediated signal in MOLT-4 were interfered by short hairpin RNAs (shRNAs)-mediated gene silencing and by small molecules-mediated disruption of Wnt-dependent signaling. We performed WNT10BIVS1knockdown or pharmacological inhibition of WNT10B release by the porcupine (PORCN) inhibitor LGK974 and these in turn progressively down-modulate WNT10B/FZD6 protein complex formation and significantly impairs intracellular effectors and leukemic expansion. Finally, we induced interference to the WNT10B/FZD6 protein complex formation by exposure to the TGFbRI inhibitor A83-01 via inhibiting FZD6 expression, confirming its role in the WNT10B-mediated signaling activation. Conclusion Our study describes the molecular circuit of WNT10BR-mediated activation and highlight a strategy for a major improvement in T-ALL treatment.By altering FZD6-WNT10B complex formation, may provide the basis for therapeutic strategies to eradicate leukemic stem cells in patients selectively deployed depending on the underlying genetics of disease. Disclosures No relevant conflicts of interest to declare.

The developmental Wnt signaling pathway effector β-catenin/TCF mediates hepatic functions of the sex hormone estradiol in regulating lipid metabolism.

The bipartite transcription factor β-catenin (β-cat)/T cell factor (TCF), formed by free β-cat and a given TCF family member, serves as the effector of the developmental Wnt signaling cascade. β-cat/TCFs also serve as effectors of certain peptide hormones or growth factors during adulthood. We reported that liver-specific expression of dominant-negative Transcription factor 7 like 2 (TCF7L2DN) led to impaired glucose disposal. Here we show that, in this LTCFDN transgenic mouse model, serum and hepatic lipid contents were elevated in male but not in female mice. In hepatocytes, TCF7L2DN adenovirus infection led to stimulated expression of genes that encode lipogenic transcription factors and lipogenic enzymes, while estradiol (E2) treatment attenuated the stimulation, associated with Wnt-target gene activation. Mechanistically, this E2-mediated activation can be attributed to elevated β-cat Ser675 phosphorylation and TCF expression. In wild-type female mice, ovariectomy (OVX) plus high-fat diet (HFD) challenge impaired glucose disposal and insulin tolerance, associated with increased hepatic lipogenic transcription factor sterol regulatory element-binding protein 1-c (SREBP-1c) expression. In wild-type mice with OVX, E2 reconstitution attenuated HFD-induced metabolic defects. Some of the attenuation effects, including insulin intolerance, elevated liver-weight gain, and hepatic SREBP-1c expression, were not affected by E2 reconstitution in HFD-fed LTCFDN mice with OVX. Finally, the effects of E2 in hepatocytes on β-cat/TCF activation can be attenuated by the G-protein-coupled estrogen receptor (GPER) antagonist G15. Our study thus expanded the scope of functions of the Wnt pathway effector β-cat/TCF, as it can also mediate hepatic functions of E2 during adulthood. This study also enriches our mechanistic understanding of gender differences in the risk and pathophysiology of metabolic diseases.

CDK12 drives breast tumor initiation and trastuzumab resistance via WNT and IRS1-ErbB-PI3K signaling.

Cyclin-dependent kinase 12 (CDK12) has emerged as an effective therapeutic target due to its ability to regulate DNA damage repair in human cancers, but little is known about the role of CDK12 in driving tumorigenesis. Here, we demonstrate that CDK12 promotes tumor initiation as a novel regulator of cancer stem cells (CSCs) and induces anti-HER2 therapy resistance in human breast cancer. High CDK12 expression caused by concurrent amplification of CDK12 and HER2 in breast cancer patients is associated with disease recurrence and poor survival. CDK12 induces self-renewal of breast CSCs and invivo tumor-initiating ability, and also reduces susceptibility to trastuzumab. Furthermore, CDK12 kinase activity inhibition facilitates anticancer efficacy of trastuzumab in HER2+ tumors, and mice bearing trastuzumab-resistant HER2+ tumor show sensitivity to an inhibitor of CDK12. Mechanistically, the catalytic activity of CDK12 is required for the expression of genes involved in the activation of ErbB-PI3K-AKT or WNT-signaling cascades. These results suggest that CDK12 is a major oncogenic driver and an actionable target for HER2+ breast cancer to replace or augment current anti-HER2 therapies.

Wnt Signaling Pathways in Keratinocyte Carcinomas.

The skin functions as a barrier between the organism and the surrounding environment. Direct exposure to external stimuli and the accumulation of genetic mutations may lead to abnormal cell growth, irreversible tissue damage and potentially favor skin malignancy. Skin homeostasis is coordinated by an intricate signaling network, and its dysregulation has been implicated in the development of skin cancers. Wnt signaling is one such regulatory pathway orchestrating skin development, homeostasis, and stem cell activation. Aberrant regulation of Wnt signaling cascades not only gives rise to tumor initiation, progression and invasion, but also maintains cancer stem cells which contribute to tumor recurrence. In this review, we summarize recent studies highlighting functional evidence of Wnt-related oncology in keratinocyte carcinomas, as well as discussing preclinical and clinical approaches that target oncogenic Wnt signaling to treat cancers. Our review provides valuable insight into the significance of Wnt signaling for future interventions against keratinocyte carcinomas.

The Function of Wnt Ligands on Osteocyte and Bone Remodeling

Bone homeostasis is continually maintained by the process of bone remodeling throughout life. Recent studies have demonstrated that Wnt signaling pathways play a fundamental role in the process of bone homeostasis and remodeling. Intracellular Wnt signaling cascades are initially triggered by a Wnt ligand–receptor complex formation. In previous studies, the blocking of Wnt ligands from different osteoblastic differentiation stages could cause defective bone development at an early stage. Osteocytes, the most abundant and long-lived type of bone cell, are a crucial orchestrator of bone remodeling. However, the role of Wnt ligands on osteocyte and bone remodeling remains unclear. In our present study, we found that, besides osteoblasts, osteocytes also express multiple Wnt ligands in the bone environment. Then, we used a Dmp1-Cre mouse line, in which there is expression in a subset of osteoblasts but mainly osteocytes, to study the function of Wnt ligands on osteocyte and bone remodeling in vivo. Furthermore, we explored the role of Wnt ligands on osteocytic mineralization ability, as well as the regulatory function of osteocytes on the process of osteoblastic differentiation and osteoclastic migration and maturity in vitro. We concluded that Wnt proteins play an important regulatory role in 1) the process of perilacunar/canalicular remodeling, as mediated by osteocytes, and 2) the balance of osteogenesis and bone resorption at the bone surface, as mediated by osteoblasts and osteoclasts, at least partly through the canonical Wnt/β-catenin signaling pathway and the OPG/RANKL signaling pathway.

Both Wnt/β-catenin and ERK5 signaling pathways are involved in BDNF-induced differentiation of pluripotent stem cells into neural stem cells

Although brain-derived neurotrophic factor (BDNF) induces the differentiation of induced pluripotent stem cells (iPSCs) into neural stem cells (NSCs), its exact mechanism remains unelucidated. Wnt/β-catenin and ERK5 are two important signalling pathways of the Wnt and MAPK signalling cascades and are speculated to be closely related to the differentiation of cells. In this study, we reported the role of the Wnt/β-catenin and ERK5 signalling pathways on the BDNF-induced differentiation of iPSCs into NSCs. We examined the expression of β-catenin and p-ERK5 using small interfering RNA (siRNA)-induced silencing of β-catenin and ERK genes. We found that BDNF significantly improved the efficiency of iPSC differentiation and that the expression of β-catenin and p-ERK5 in the BDNF culture medium was significantly upregulated. Furthermore, we found that the expression of the β-catenin component was downregulated by siRNA-β-catenin, and the expression of the p-ERK5 component was downregulated by siRNA-ERK5. Flow cytometry showed that the differentiation rate of iPSCs was also significantly decreased by RNA interference. The results suggested that the Wnt/β-catenin and ERK5 signalling pathways are activated in the process of BDNF-induced iPSC differentiation. Interestingly, our study showed that siRNA-ERK5 not only inhibits the activity of the ERK5 signalling pathway but also partially controls the activity of the Wnt/β-catenin signalling pathway. The results suggested that the Wnt/β-catenin and ERK5 signalling pathways are not independently involved in the process of BDNF-induced iPSC differentiation. Our study showed that BDNF promotes the differentiation of iPSCs into NSCs by activating the Wnt/β-catenin and ERK5 signalling pathways, and an interconnected relationship may exist between the Wnt/β-catenin and ERK5 signalling pathways.

Osteocytes and mechanical loading: The Wnt connection.

Bone adapts to the mechanical forces that it experiences. Orthodontic tooth movement harnesses the cell- and tissue-level properties of mechanotransduction to achieve alignment and reorganization of the dentition. However, the mechanisms of action that permit bone resorption and formation in response to loads placed on the teeth are incompletely elucidated, though several mechanisms have been identified. Wnt/Lrp5 signalling in osteocytes is a key pathway that modulates bone tissue's response to load. Numerous mouse models that harbour knock-in, knockout and transgenic/overexpression alleles targeting genes related to Wnt signalling point to the necessity of Wnt/Lrp5, and its localization to osteocytes, for proper mechanotransduction in bone. Alveolar bone is rich in osteocytes and is a highly mechanoresponsive tissue in which components of the canonical Wnt signalling cascade have been identified. As Wnt-based agents become clinically available in the next several years, the major challenge that lies ahead will be to gain a more complete understanding of Wnt biology in alveolar bone so that improved/expedited tooth movement becomes a possibility.

The Nuclear Receptor and Clock Repressor Rev-erb\u03b1 Suppresses Myogenesis

Rev-erbα is a ligand-dependent nuclear receptor and a key repressor of the molecular clock transcription network. Accumulating evidence indicate that the circadian clock machinery governs diverse biological processes in skeletal muscle, including muscle growth, repair and mass maintenance. The physiological function of Rev-erbα in myogenic regulation remains largely unknown. Here we show that Rev-erbα exerts cell-autonomous inhibitory effects on proliferation and differentiation of myogenic precursor cells, and these actions concertedly inhibit muscle regeneration in vivo. Mechanistic studies reveal Rev-erbα direct transcriptional control of two major myogenic mechanisms, proliferative pathway and the Wnt signaling cascade. Consistent with this finding, primary myoblasts lacking Rev-erbα display significantly enhanced proliferative growth and myogenic progression. Furthermore, pharmacological activation of Rev-erbα activity attenuates, whereas its inhibition by an antagonist promotes these processes. Notably, upon muscle injury, the loss-of-function of Rev-erbα in vivo augmented satellite cell proliferative expansion and regenerative progression during regeneration. Collectively, our study identifies Rev-erbα as a novel inhibitory regulator of myogenic progenitor cell properties that suppresses postnatal myogenesis. Pharmacological interventions to dampen Rev-erbα activity may have potential utilities to enhance regenerative capacity in muscle diseases.

Wnt signaling pathway in osteoporosis: Epigenetic regulation, interaction with other signaling pathways, and therapeutic promises.

Wnt is a major signaling pathway involved in multifaceted roles of various biological processes. Bones are dynamic tissues which are able to remodel and maintain the tissue homeostasis. Wnt signaling cascade leads to the promotion of bone formation and suppression of bone resorption, leading to a balance in bone remodeling. Recent evidence has reinforced the inevitable role of Wnt signaling in osteoporosis. The complex genetic and epigenetic regulations of Wnt signaling factors and their interaction with other master signaling pathways such as TGF-β, BMP, PI3K/AKT, and Hedgehog outline their importance in diagnosis and treatment of osteoporosis. In this review, we highlighted the recent advances in function of Wnt signaling-related epigenetic regulation, different signaling pathways interacting with Wnt, and their roles in osteoporosis. Finally, we discussed novel promises in molecular targeted therapy of osteoporosis.

Establishment of the Axial Polarity and Cell Fate in Metazoa via Canonical Wnt Signaling: New Insights from Sponges and Annelids

In this paper, the role of the Wnt/β-catenin pathway in the establishment of the body plan in multicellular animals has been analyzed. We demonstrated that at different stages of development the Wnt signaling cascade is involved in several directly unrelated processes such as inner germ layer specification, anterior–posterior axis patterning, and terminal growth. Bioinformatics analysis revealed the independent divergence of Wnt ligands in basal Metazoa and conservation of Wnt subfamilies within the Cnidaria + Bilateria clade. Polarized expression of Wnt ligands in sponge and annelid larvae has been shown, thus confirming the applicability of the existing model of the main body axis patterning to two more taxa. The β-catenin localization and inhibitory analysis have provided evidence of the unlikely role for Wnt pathway in endomesoderm determination in nereid polychaetes. The evolutionary trend to establish alternative mechanisms even for key events such as segregation of germ layers has been observed in the case of more determinative ontogeny and predominance of autonomous specification, as exemplified by the heteroquadrant (unequal) type of spiral development.

Deletion of Pr72 causes cardiac developmental defects in Zebrafish.

The alpha regulator subunit B'' of protein phosphatase 2 (PPP2R3A), a regulatory subunit of protein phosphatase 2A (PP2A), was reported to present a special subcellular localization in cardiomyocytes and elevate in non-ischemia failing hearts. PPP2R3A has two transcriptions PR72 and PR130. PR72 acts as a negative regulator of the Wnt signaling cascade, while the Wnt signaling cascade plays a pivotal role in cardiac development. And PR130 was found to be involved in cardiac development of zebrafish in our previous study. Thus, to investigate the function of PR72 in heart, two stable pr72 knockout (KO) zebrafish lines were generated using Transcription Activator-Like Effector Nuclease (TALEN) technology. Homozygous pr72 KO fish struggled to survive to adulthood and exhibited cardiac developmental defects, including enlarged ventricular chambers, reduced cardiomyocytes and decreased cardiac function. And the defective sarcomere ultrastructure that affected mitochondria, I bands, Z lines, and intercalated disks was also observed. Furthermore, the abnormal heart looping was detected in mutants which could be rescued by injection with wild type pr72 mRNA. Additionally, it was found that Wnt effectors were elevated in mutants. Those indicated that deletion of pr72 in zebrafish interrupted cardiac development, probably through activation of the Wnt pathway.