Ror2 receptor requires tyrosine kinase activity to mediate Wnt5A signaling

Craniofacial studies in chicken embryos confirm the pathogenicity of human FZD2 variants associated with Robinow syndrome

Robinow syndrome is a rare disease caused by variants of seven WNT pathway genes. Craniofacial features include widening of the nasal bridge and jaw hypoplasia. We used the chicken embryo to test whether two missense human FZD2 variants (1301G>T, p.Gly434Val; 425C>T, p.Pro142Lys) were sufficient to change frontonasal mass development. In vivo, the overexpression of retroviruses with wild-type or variant human FZD2 inhibited upper beak ossification. In primary cultures, wild-type and variant human FZD2 significantly inhibited chondrogenesis, with the 425C>T variant significantly decreasing activity of a SOX9 luciferase reporter compared to that for the wild type or 1301G>T. Both variants also increased nuclear shuttling of β-catenin (CTNNB1) and increased the expression of TWIST1, which are inhibitory to chondrogenesis. In canonical WNT luciferase assays using frontonasal mass cells, the variants had dominant-negative effects on wild-type FZD2. In non-canonical assays, the 425C>T variant failed to activate the reporter above control levels and was unresponsive to exogenous WNT5A. This is the first single amino acid change to selectively alter ligand binding in a FZD receptor. Therefore, FZD2 missense variants are pathogenic and could lead to the altered craniofacial morphogenesis seen in Robinow syndrome.

Role of the Ror family receptors in Wnt5a signaling

Ror-family receptors, Ror1 and Ror2, are type I transmembrane proteins that possess an extracellular cysteine-rich domain, which is conserved throughout the Frizzled-family receptors and is a binding site for Wnt ligands. Both Ror1 and Ror2 function primarily as receptors or co-receptors for Wnt5a to activate the β-catenin-independent, non-canonical Wnt signaling, thereby regulating cell polarity, migration, proliferation, and differentiation depending on the context. Ror1 and Ror2 are expressed highly in many tissues during embryogenesis but minimally or scarcely in adult tissues, with some exceptions. In contrast, Ror1 and Ror2 are expressed in many types of cancers, and their high expression often contributes to the progression of the disease. Therefore, Ror1 and Ror2 have been proposed as potential targets for the treatment of the malignancies. In this review, we provide an overview of the regulatory mechanisms of Ror1/Ror2 expression and discuss how Wnt5a-Ror1/Ror2 signaling is mediated and regulated by their interacting proteins.

Morphogenesis of fungiform papillae in developing miniature pigs

Objective

Fungiform papillae contain taste buds and play a critical role in mastication and the gustatory system. In this study, we report a series of sequential observations of organogenesis of fungiform papillae in miniature pigs, as well as changes in the expression of BMP2, BMP4, Wnt5a, Sox2, and Notch1 signaling pathway components.

Design

In this study, we investigated the spatiotemporal expression patterns of BMP, Wnt, Sox2 and Notch in the fungiform papillae of miniature pigs at the bud stage (E40), cap stage (E50) and bell stage (E60). Pregnant miniature pigs were obtained, and the samples were processed for histological staining. Immunohistochemistry and real-time PCR were used to detect the mRNA and protein expression levels of BMP2, BMP4, Wnt5a, Sox2, and Notch1.

Results

At E40, fungiform papillae were present on the anterior two-thirds of the tongue in a specific array and pattern. The fungiform papillae were enlarged and basically developed at E50 and were largest at the earlier stage (E60). Most of the BMP2 was concentrated in the epithelial layer and the connective tissue core of the fungal papilloma and gradually accumulated from E40-E60. BMP-4 was weakly expressed in the fungiform papillae epithelia, but BMP-4-positive cells were also observed in the developing tongue muscle at E50 and E60. Wnt5a-positive cells were observed in the fungiform papillae epithelia and developing tongue muscle at all three time points. Sox2-positive cells were observed only in fungiform papillae epithelial cells, and Notch1-positive cells could not be detected.

Conclusions

This study provides primary data regarding the morphogenesis and expression of developmental signals in the fungiform papillae of miniature pigs, establishing a foundation for further research in both this model and humans.

Unraveling the prevalence of various signalling pathways in non-small-cell lung cancer: a review

Cancer has become a huge public health issue all around the world. The focus of research is on innovative cancer therapy techniques that include the disease's unique targets. Among the cancer-related deaths that occur, lung cancer is considered to be one of the major, accounting for about 1.6 million fatalities globally in 2012, or nearly 20% of all cancer deaths. Non-small-cell lung cancer, a type of lung cancer comprises upto 84% of lung cancer cases, demonstrating the need for a more effective treatment. A novel category of cancer management, known as targeted cancer medicines, has risen to prominence in recent years. Targeted cancer treatments, like traditional chemotherapy, employ pharmacological drugs to slow cancer development, enhance cell death, and prevent it from spreading. Targeted treatments, as the name implies, work by interfering with particular proteins implicated in cancer. Numerous research conducted in the last several decades have led to the conclusion that signalling pathways are involved in the growth of lung cancer. All malignant tumours are produced, spread, invade, and behave in various abnormal ways due to abnormal pathways. Numerous significant signalling pathways, including the RTK/RAS/MAP-Kinase pathway (hence often referred to as RTK-RAS for simplicity), PI3K/Akt signalling, and others, have been discovered as commonly genetically changed. The current developments in research on various signalling pathways, as well as the underlying mechanisms of the molecules implicated in these pathways, are innovatively summarised in this review. To give a good sense of the study that has been done so far, many routes are placed together. Thus, this review includes the detailed description regarding each pathways, the mutations formed, and the present treatment strategy to overcome the resistance.

Exploring the association between congenital vertebral malformations and neural tube defects

Congenital vertebral malformations (CVMs) and neural tube defects (NTDs) are common birth defects affecting the spine and nervous system, respectively, due to defects in somitogenesis and neurulation. Somitogenesis and neurulation rely on factors secreted from neighbouring tissues and the integrity of the axial structure. Crucial signalling pathways like Wnt, Notch and planar cell polarity regulate somitogenesis and neurulation with significant crosstalk. While previous studies suggest an association between CVMs and NTDs, the exact mechanism underlying this relationship remains unclear. In this review, we explore embryonic development, signalling pathways and clinical phenotypes involved in the association between CVMs and NTDs. Moreover, we provide a summary of syndromes that exhibit occurrences of both CVMs and NTDs. We aim to provide insights into the potential mechanisms underlying the association between CVMs and NTDs, thereby facilitating clinical diagnosis and management of these anomalies.

ROR2 homodimerization is sufficient to activate a neuronal Wnt/calcium signaling pathway

Wnt signaling plays a key role in the mature CNS by regulating trafficking of NMDA-type glutamate receptors and intrinsic properties of neurons. The Wnt receptor ROR2 has been identified as a necessary component of the neuronal Wnt5a/Ca2+ signaling pathway that regulates synaptic and neuronal function. Since ROR2 is considered a pseudokinase, its mechanism for downstream signaling upon ligand binding has been controversial. It has been suggested that its role is to function as a coreceptor of a G-protein-coupled Wnt receptor of the Frizzled family. We show that chemically induced homodimerization of ROR2 is sufficient to recapitulate key signaling events downstream of receptor activation in neurons, including PKC and JNK kinases activation, elevation of somatic and dendritic Ca2+ levels, and increased trafficking of NMDARs to synapses. In addition, we show that homodimerization of ROR2 induces phosphorylation of the receptor on Tyr residues. Point mutations in the conserved but presumed nonfunctional ATP-binding site of the receptor prevent its phosphorylation, as well as downstream signaling. This suggests an active kinase domain. Our results indicate that ROR2 can signal independently of Frizzled receptors to regulate the trafficking of a key synaptic component. Additionally, they suggest that homodimerization can overcome structural conformations that render the tyrosine kinase inactive. A better understanding of ROR2 signaling is crucial for comprehending the regulation of synaptic and neuronal function in normal brain processes in mature animals.

Altered binding affinity of SIX1-Q177R correlates with enhanced WNT5A and WNT pathway effector expression in Wilms tumor

Wilms tumors present as an amalgam of varying proportions of tissues located within the developing kidney, one being the nephrogenic blastema comprising multipotent nephron progenitor cells (NPCs). The recurring missense mutation Q177R in NPC transcription factors SIX1 and SIX2 is most correlated with tumors of blastemal histology and is significantly associated with relapse. Yet, the transcriptional regulatory consequences of SIX1/2-Q177R that might promote tumor progression and recurrence have not been investigated extensively. Utilizing multiple Wilms tumor transcriptomic datasets, we identified upregulation of the gene encoding non-canonical WNT ligand WNT5A in addition to other WNT pathway effectors in SIX1/2-Q177R mutant tumors. SIX1 ChIP-seq datasets from Wilms tumors revealed shared binding sites for SIX1/SIX1-Q177R within a promoter of WNT5A and at putative distal cis-regulatory elements (CREs). We demonstrate colocalization of SIX1 and WNT5A in Wilms tumor tissue and utilize in vitro assays that support SIX1 and SIX1-Q177R activation of expression from the WNT5A CREs, as well as enhanced binding affinity within the WNT5A promoter that may promote the differential expression of WNT5A and other WNT pathway effectors associated with SIX1-Q177R tumors.

WNT5A: a double-edged sword in colorectal cancer progression

The Wnt signaling pathway is known to play a crucial role in cancer, and WNT5A is a member of this pathway that binds to the Frizzled (FZD) and Receptor Tyrosine Kinase-Like Orphan Receptor (ROR) family members to activate non-canonical Wnt signaling pathways. The WNT5A pathway is involved in various cellular processes, such as proliferation, differentiation, migration, adhesion, and polarization. In the case of colorectal cancer (CRC), abnormal activation or inhibition of WNT5A signaling can lead to both oncogenic and antitumor effects. Moreover, WNT5A is associated with inflammation, metastasis, and altered metabolism in cancer cells. This article aims to discuss the molecular mechanisms and dual roles of WNT5A in CRC.

Retrotransposon LINE-1 bodies in the cytoplasm of piRNA-deficient mouse spermatocytes: Ribonucleoproteins overcoming the integrated stress response

Transposable elements (TE) are mobile DNA sequences whose excessive proliferation endangers the host. Although animals have evolved robust TE-targeting defenses, including Piwi-interacting (pi)RNAs, retrotransposon LINE-1 (L1) still thrives in humans and mice. To gain insights into L1 endurance, we characterized L1 Bodies (LBs) and ORF1p complexes in germ cells of piRNA-deficient Maelstrom null mice. We report that ORF1p interacts with TE RNAs, genic mRNAs, and stress granule proteins, consistent with earlier studies. We also show that ORF1p associates with the CCR4-NOT deadenylation complex and PRKRA, a Protein Kinase R factor. Despite ORF1p interactions with these negative regulators of RNA expression, the stability and translation of LB-localized mRNAs remain unchanged. To scrutinize these findings, we studied the effects of PRKRA on L1 in cultured cells and showed that it elevates ORF1p levels and L1 retrotransposition. These results suggest that ORF1p-driven condensates promote L1 propagation, without affecting the metabolism of endogenous RNAs.

The Multifaceted Role of WNT Signaling in Alzheimer's Disease Onset and Age-Related Progression

The evolutionary conserved WNT signaling pathway orchestrates numerous complex biological processes during development and is critical to the maintenance of tissue integrity and homeostasis in the adult. As it relates to the central nervous system, WNT signaling plays several roles as it relates to neurogenesis, synaptic formation, memory, and learning. Thus, dysfunction of this pathway is associated with multiple diseases and disorders, including several neurodegenerative disorders. Alzheimer's disease (AD) is characterized by several pathologies, synaptic dysfunction, and cognitive decline. In this review, we will discuss the various epidemiological, clinical, and animal studies that demonstrate a precise link between aberrant WNT signaling and AD-associated pathologies. In turn, we will discuss the manner in which WNT signaling influences multiple molecular, biochemical, and cellular pathways upstream of these end-point pathologies. Finally, we will discuss how merging tools and technologies can be used to generate next generation cellular models to dissect the relationship between WNT signaling and AD.

Ribonucleoprotein condensation driven by retrotransposon LINE-1 sustains RNA integrity and translation in mouse spermatocytes

Transposable elements (TE) are mobile DNA sequences whose excessive proliferation endangers the host. Although animals have evolved robust TE-targeting defenses, including Piwi-interacting (pi)RNAs, retrotransposon LINE-1 (L1) still thrives in humans and mice. To gain insights into L1 endurance, we characterized L1 Bodies (LBs) and ORF1p complexes in germ cells of piRNA-deficient Maelstrom null mice. We report that ORF1p interacts with TE RNAs, genic mRNAs, and stress granule proteins, consistent with earlier studies. We also show that ORF1p associates with the CCR4-NOT deadenylation complex and PRKRA, a Protein Kinase R factor. Despite ORF1p interactions with these negative regulators of RNA expression, the stability and translation of LB-localized mRNAs remain unchanged. To scrutinize these findings, we studied the effects of PRKRA on L1 in cultured cells and showed that it elevates ORF1p levels and L1 retrotransposition. These results suggest that ORF1p-driven condensates promote L1 propagation, without affecting the metabolism of endogenous RNAs.

Novel Candidate Genes for Non-Syndromic Tooth Agenesis Identified Using Targeted Next-Generation Sequencing

Non-syndromic tooth agenesis (ns-TA) is one of the most common dental anomalies characterized by the congenital absence of at least one permanent tooth (excluding third molars). Regarding the essential role of genetic factors in ns-TA aetiology, the present study aimed to identify novel pathogenic variants underlying hypodontia and oligodontia. In a group of 65 ns-TA patients and 127 healthy individuals from the genetically homogenous Polish population, the coding sequences of 423 candidate genes were screened using targeted next-generation sequencing. Pathogenic and likely pathogenic variants were identified in 37 (56.92%) patients, including eight nucleotide alternations of genes not previously implicated in ns-TA (CHD7, CREBBP, EVC, LEF1, ROR2, TBX22 and TP63). However, since only single variants were detected, future research is required to confirm and fully understand their role in the aetiology of ns-TA. Additionally, our results support the importance of already known ns-TA candidate genes (AXIN2, EDA, EDAR, IRF6, LAMA3, LRP6, MSX1, PAX9 and WNT10A) and provide additional evidence that ns-TA might be an oligogenic condition involving the cumulative effect of rare variants in two or more distinct genes.

Tumor suppressive functions of WNT5A in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a highly aggressive soft tissue malignancy that predominantly affects children. The main subtypes are alveolar RMS (ARMS) and embryonal RMS (ERMS) and the two show an impaired muscle differentiation phenotype. One pathway involved in muscle differentiation is WNT signaling. However, the role of this pathway in RMS is far from clear. Our recent data showed that the canonical WNT/β-Catenin pathway serves a subordinate role in RMS, whereas non-canonical WNT signaling probably is more important for this tumor entity. The present study investigated the role of WNT5A, which is the major ligand of non-canonical WNT signaling, in ERMS and ARMS. Gene expression analysis showed that WNT5A was expressed in human RMS samples and that its expression is more pronounced in ERMS. When stably overexpressed in RMS cell lines, WNT5A decreased proliferation and migration of the cells as demonstrated by BrdU incorporation and Transwell migration or scratch assay, respectively. WNT5A also decreased the self-renewal capacity and the expression of stem cell markers and modulates the levels of muscle differentiation markers as shown by sphere assay and western blot analysis, respectively. Finally, overexpression of WNT5A can destabilize active β-Catenin of RMS cells. A WNT5A knockdown has opposite effects. Together, the results suggest that WNT5A has tumor suppressive functions in RMS, which accompanies downregulation of β-Catenin.

ROR2 regulates self-renewal and maintenance of hair follicle stem cells

Hair follicles undergo cycles of regeneration fueled by hair follicle stem cells (HFSCs). While β-catenin-dependent canonical Wnt signaling has been extensively studied and implicated in HFSC activation and fate determination, very little is known about the function of β-catenin-independent Wnt signaling in HFSCs. In this study, we investigate the functional role of ROR2, a Wnt receptor, in HFSCs. By analyzing Ror2-depleted HFSCs, we uncover that ROR2 is not only essential to regulate Wnt-activated signaling that is responsible for HFSC activation and self-renewal, but it is also required to maintain proper ATM/ATR-dependent DNA damage response, which is indispensable for the long-term maintenance of HFSCs. In analyzing HFSCs lacking β-catenin, we identify a compensatory role of ROR2-PKC signaling in protecting β-catenin-null HFSCs from the loss of stem cell pool. Collectively, our study unveils a previously unrecognized role of ROR2 in regulation of stem cell self-renewal and maintenance.

Wnt signaling functions in tissue homeostasis and tumorigenesis. Here the authors show that ROR2, a Wnt receptor, plays roles not only in transducing Wnt signaling, but also in regulation of DNA damage response critical for stem cell maintenance.

The Ror-Family Receptors in Development, Tissue Regeneration and Age-Related Disease

The Ror-family proteins, Ror1 and Ror2, act as receptors or co-receptors for Wnt5a and its related Wnt proteins to activate non-canonical Wnt signaling. Ror1 and/or Ror2-mediated signaling plays essential roles in regulating cell polarity, migration, proliferation and differentiation during developmental morphogenesis, tissue-/organo-genesis and regeneration of adult tissues following injury. Ror1 and Ror2 are expressed abundantly in developing tissues in an overlapping, yet distinct manner, and their expression in adult tissues is restricted to specific cell types such as tissue stem/progenitor cells. Expression levels of Ror1 and/or Ror2 in the adult tissues are increased following injury, thereby promoting regeneration or repair of these injured tissues. On the other hand, disruption of Wnt5a-Ror2 signaling is implicated in senescence of tissue stem/progenitor cells that is related to the impaired regeneration capacity of aged tissues. In fact, Ror1 and Ror2 are implicated in age-related diseases, including tissue fibrosis, atherosclerosis (or arteriosclerosis), neurodegenerative diseases, and cancers. In these diseases, enhanced and/or sustained (chronic) expression of Ror1 and/or Ror2 is observed, and they might contribute to the progression of these diseases through Wnt5a-dependent and -independent manners. In this article, we overview recent advances in our understanding of the roles of Ror1 and Ror2-mediated signaling in the development, tissue regeneration and age-related diseases, and discuss their potential to be therapeutic targets for chronic inflammatory diseases and cancers.

WNT5A Interacts With FZD5 and LRP5 to Regulate Proliferation and Self-Renewal of Endometrial Mesenchymal Stem-Like Cells

Endometrial mesenchymal stem-like cells (eMSC) reside in the basal layer of the endometrium and are responsible for cyclic regeneration during the reproductive lives of women. Myometrial cells act as a component of the niche and regulate the stem cell fate through the activation of WNT/β-catenin signaling via WNT5A. Since WNT5A-responsive mechanisms on eMSC are still uncertain, we hypothesize that the WNT ligand–WNT5A works to activate WNT/β-catenin signaling through binding to Frizzled receptors (FZDs) and co-receptor low-density lipoprotein receptor-related protein 5 (LRP5). Among the various receptors that have been reported to interact with WNT5A, we found FZD5 abundantly expressed by eMSC when compared to unfractionated stromal cells. Neutralizing the protein expression by using anti-FZD5 antibody suppressed the stimulatory effects on phenotypic expression and the clonogenicity of eMSC in a myometrial cell–eMSC co-culture system as well as in an L-Wnt5a conditioned medium. Gene silencing of FZD5 not only reduced the binding of WNT5A to eMSC but also decreased the TCF/LEF transcriptional activities and expression of active β-catenin. Inhibition of LRP coreceptors with recombinant Dickkopf-1 protein significantly reduced the binding affinity of eMSC to WNT5A as well as the proliferation and self-renewal activity. During postpartum remodeling in mouse endometrium, active β-catenin (ABC) was detected in label-retaining stromal cells (LRSCs), and these ABC+ LRSCs express FZD5 and LRP5, suggesting the activation of WNT/β-catenin signaling. In conclusion, our findings demonstrate the interaction of WNT5A, FZD5, and LRP5 in regulating the proliferation and self-renewal of eMSC through WNT/β-catenin signaling.

Cellular and molecular mechanisms implicated in the dual role of ROR2 in cancer

ROR1 and ROR2 are Wnt receptors that are critical for β-catenin-independent Wnt pathways and have been linked to processes driving tumor progression, such as cell proliferation, survival, invasion, and therapy resistance. Both receptors have garnered interest as potential therapeutic targets since they are largely absent in adult tissue, are overexpressed in several cancers, and, as members of the receptor tyrosine kinase family, are easier to target than all other components of the pathway. Unlike ROR1 which always promotes tumorigenesis, ROR2 has a very complex role in cancer acting either to promote or inhibit tumor progression in different tumor types. In the present article, we summarize the findings on ROR2 expression in cancer patients and its impact on clinical outcome. Further, we review the biological processes and signaling pathways regulated by ROR2 that explain its dual role in cancer. Finally, we describe the ongoing strategies to target ROR2 in cancer.

Receptor Tyrosine Kinases ror1/2 and ryk Are Co-expressed with Multiple Wnt Signaling Components During Early Development of Sea Urchin Embryos

AbstractA combination of receptors, co-receptors, and secreted Wnt modulators form protein complexes at the cell surface that activate one or more of the three different Wnt signaling pathways (Wnt/β-catenin, Wnt/JNK, and Wnt/Ca2+). Two or more of these pathways are often active in the same cellular territories, forming Wnt signaling networks; however, the molecular mechanisms necessary to integrate information from these pathways in these situations are unclear in any in vivo model system. Recent studies have implicated two Wnt binding receptor tyrosine kinases, receptor tyrosine kinase-like orphan receptor (Ror) and related-to-receptor tyrosine kinase (Ryk), in the regulation of canonical and non-canonical Wnt signaling pathways, depending on the context; however, the spatiotemporal expression of these genes in relation to Wnt signaling components has not been well characterized in most deuterostome model systems. Here we use a combination of phylogenetic and spatiotemporal gene expression analyses to characterize Ror and Ryk orthologs in sea urchin embryos. Our phylogenetic analysis indicates that both ror1/2 and ryk originated as single genes from the metazoan ancestor. Expression analyses indicate that ror1/2 and ryk are expressed in the same domains of many Wnt ligands and Frizzled receptors essential for the specification and patterning of germ layers along the early anterior-posterior axis. In addition, both genes are co-expressed with Wnt signaling components in the gut, ventral ectoderm, and anterior neuroectoderm territories later in development. Together, our results indicate that Ror and Ryk have a complex evolutionary history and that their spatiotemporal expression suggests that they could contribute to the complexity of Wnt signaling in early sea urchin embryogenesis.

Upregulation of receptor tyrosine kinase-like orphan receptor 2 in idiopathic pulmonary fibrosis

BACKGROUND/AIMS

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) is a major regulator of Wnt signaling, which is involved in fibroblast dysfunction. Because its role has not been evaluated in idiopathic pulmonary fibrosis (IPF), we examined the clinical implications of ROR2 expression.

METHODS

ROR2 mRNA expression was measured using reverse transcription polymerase chain reaction in lung tissue-derived fibroblasts from IPF patients (n = 14) and from controls (n = 10). ROR2 protein was measured using enzyme-linked immunosorbent assay in primary fibroblasts from IPF patients (n = 14) and controls (n = 10), and in bronchoalveolar lavage (BAL) fluids obtained from normal controls (NC; n = 30). IPF patients (n = 84), and other patients with interstitial lung diseases, including nonspecific interstitial pneumonia (NSIP; n = 10), hypersensitivity pneumonitis (HP; n = 10), and sarcoidosis (n = 10).

RESULTS

ROR2 mRNA and protein levels were significantly higher in IPF fibroblasts than in controls (p = 0.003, p = 0.0017, respectively). ROR2 protein levels in BAL fluids from patients with IPF were significantly higher than in those from NC (p < 0.001), and from patients with NSIP (p = 0.006), HP (p = 0.004), or sarcoidosis (p = 0.004). Receiver operating characteristic curves showed a clear difference between IPF and NC in ROR2 protein level (area under the curve, 0.890; confidence interval, 0.829 to 0.950; p < 0.001). ROR2 protein levels were significantly higher in GAP stage III than in GAP stages I and II (p = 0.016).

CONCLUSION

ROR2 may be related to the development of IPF, and its protein level may be a useful and severity-dependent candidate marker for IPF.

ROR2 blockade as a therapy for osteoarthritis

Osteoarthritis is characterized by the loss of the articular cartilage, bone remodeling, pain, and disability. No pharmacological intervention can currently halt progression of osteoarthritis. Here, we show that blocking receptor tyrosine kinase-like orphan receptor 2 (ROR2) improves cartilage integrity and pain in osteoarthritis models by inhibiting yes-associated protein (YAP) signaling. ROR2 was up-regulated in the cartilage in response to inflammatory cytokines and mechanical stress. The main ligand for ROR2, WNT5A, and the targets YAP and connective tissue growth factor were up-regulated in osteoarthritis in humans. In vitro, ROR2 overexpression inhibited chondrocytic differentiation. Conversely, ROR2 blockade triggered chondrogenic differentiation of C3H10T¹/₂ cells and suppressed the expression of the cartilage-degrading enzymes a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5. The chondrogenic effect of ROR2 blockade in the cartilage was independent of WNT signaling and was mediated by down-regulation of YAP signaling. ROR2 signaling induced G protein and Rho-dependent nuclear accumulation of YAP, and YAP inhibition was required but not sufficient for ROR2 blockade-induced chondrogenesis. ROR2 silencing protected mice from instability-induced osteoarthritis with improved structural outcomes, sustained pain relief, and without apparent side effects or organ toxicity. Last, ROR2 silencing in human articular chondrocytes transplanted in nude mice led to the formation of cartilage organoids with more and better differentiated extracellular matrix, suggesting that the anabolic effect of ROR2 blockade is conserved in humans. Thus, ROR2 blockade is efficacious and well tolerated in preclinical animal models of osteoarthritis.

Tyrosine Kinase ROR1 as a Target for Anti-Cancer Therapies

Receptor tyrosine kinase ROR1 plays an essential role in embryogenesis and is overexpressed in many types of malignant tumors. Studies have demonstrated that it plays an important role in oncogenesis by activating cell survival signaling events, particularly the non-canonical WNT signaling pathway. Antibody-based immunotherapies targeting ROR1 have been developed and evaluated in preclinical and clinical studies with promising outcomes. However, small molecule inhibitors targeting ROR1 are underappreciated because of the initial characterization of ROR1 as a peusdokinase. The function of ROR1 as a tyrosine kinase remains poorly understood, although accumulating evidence have demonstrated its intrinsic tyrosine kinase activity. In this review, we analyzed the structural and functional features of ROR1 and discussed therapeutic strategies targeting this kinase.

Kidney and epigenetic mechanisms of salt-sensitive hypertension

Dietary salt intake increases blood pressure (BP) but the salt sensitivity of BP differs between individuals. The interplay of ageing, genetics and environmental factors, including malnutrition and stress, contributes to BP salt sensitivity. In adults, obesity is often associated with salt-sensitive hypertension. The children of women who experience malnutrition during pregnancy are at increased risk of developing obesity, diabetes and salt-sensitive hypertension as adults. Similarly, the offspring of mice that are fed a low-protein diet during pregnancy develop salt-sensitive hypertension in association with aberrant DNA methylation of the gene encoding type 1A angiotensin II receptor (AT_1AR) in the hypothalamus, leading to upregulation of hypothalamic AT_1AR and renal sympathetic overactivity. Ageing is also associated with salt-sensitive hypertension. In aged mice, promoter methylation leads to reduced kidney production of the anti-ageing factor Klotho and a decrease in circulating soluble Klotho. In the setting of Klotho deficiency, salt-induced activation of the vascular Wnt5a-RhoA pathway leads to ageing-associated salt-sensitive hypertension, potentially as a result of reduced renal blood flow and increased peripheral resistance. Thus, kidney mechanisms and aberrant DNA methylation of certain genes are involved in the development of salt-sensitive hypertension during fetal development and old age. Three distinct paradigms of epigenetic memory operate on different timescales in prenatal malnutrition, obesity and ageing.

WNT5a in Colorectal Cancer: Research Progress and Challenges

Despite the clinical development of new adjuvant and neoadjuvant chemotherapy drugs, colorectal cancer is still one of the leading causes of cancer-related death in human beings. WNT5a, an autocrine and paracrine β-catenin independent ligand, has been shown to induce tumor inhibition and carcinogenic signals, depending on the type of cancer. In patients with colorectal cancer, WNT5a triggers a variety of downstream signaling pathways, which mainly affect the migration and invasion of tumor cells. This article reviews the mechanism and therapeutic potential of WNT5a in colorectal cancer. In short, an in-depth understanding of the role of WNT5a in colorectal cancer is very helpful to better deal with this disease.

E2F1-mediated repression of WNT5A expression promotes brain metastasis dependent on the ERK1/2 pathway in EGFR-mutant non-small cell lung cancer

Brain metastasis (BM) is associated with poor prognosis in patients with advanced non-small cell lung cancer (NSCLC). Epidermal growth factor receptor (EGFR) mutation reportedly enhances the development of BM. However, the exact mechanism of how EGFR-mutant NSCLC contributes to BM remains unknown. Herein, we found the protein WNT5A, was significantly downregulated in BM tissues and EGFR-mutant samples. In addition, the overexpression of WNT5A inhibited the growth, migration, and invasion of EGFR-mutant cells in vitro and retarded tumor growth and metastasis in vivo compared with the EGFR wide-type cells. We demonstrated a molecular mechanism whereby WNT5A be negatively regulated by transcription factor E2F1, and ERK1/2 inhibitor (U0126) suppressed E2F1's regulation of WNT5A expression in EGFR-mutant cells. Furthermore, WNT5A inhibited β-catenin activity and the transcriptional levels of its downstream genes in cancer progression. Our research revealed the role of WNT5A in NSCLC BM with EGFR mutation, and proved that E2F1-mediated repression of WNT5A was dependent on the ERK1/2 pathway, supporting the notion that targeting the ERK1/2-E2F1-WNT5A pathway could be an effective strategy for treating BM in EGFR-mutant NSCLC.

Salt causes aging-associated hypertension via vascular Wnt5a under Klotho deficiency

Aging is associated with a high prevalence of hypertension due to elevated susceptibility of BP to dietary salt, but its mechanism is unknown. Serum levels of Klotho, an anti-aging factor, decline with age. We found that high salt (HS) increased BP in aged mice and young heterozygous Klotho-knockout mice and was associated with increased vascular expression of Wnt5a and p-MYPT1, which indicate RhoA activity. Not only the Wnt inhibitor LGK974 and the Wnt5a antagonist Box5 but Klotho supplementation inhibits HS-induced BP elevation, similarly to the Rho kinase inhibitor fasudil, associated with reduced p-MYPT1 expression in both groups of mice. In cultured vascular smooth muscle cells, Wnt5a and angiotensin II (Ang II) increased p-MYPT1 expression but knockdown of Wnt5a with siRNA abolished Ang II-induced upregulation of p-MYPT1, indicating that Wnt5a is indispensable for Ang II-induced Rho/ROCK activation. Notably, Klotho inhibited Wnt5a- and Ang II-induced upregulation of p-MYPT1. Consistently, Klotho supplementation ameliorated HS-induced augmentation of reduced renal blood flow (RBF) response to intra-arterial infusion of Ang II and the thromboxane A2 analog U46619, which activated RhoA in both groups of mice and were associated with the inhibition of BP elevation, suggesting that abnormal response of RBF to Ang II contributes to HS-induced BP elevation. Thus, Klotho deficiency underlies aging-associated salt-sensitive hypertension through vascular non-canonical Wnt5a/RhoA activation.

ROR2 Is Epigenetically Regulated in Endometrial Cancer

Simple Summary

Endometrial cancer is one of the fastest rising cancers in women. The Wnt signalling receptor ROR2 has been shown to play distinct roles in regards to tumorigenesis in different tumour types. The aim of this study was to investigate the role of ROR2 in endometrial cancer and to determine if ROR2 expression is epigenetically regulated. Through the analyses of publicly available TCGA and GEO datasets, low ROR2 expression was correlated with unfavourable outcome and reduced overall survival of endometrial cancer patients. In addition, we observed epigenetic repression of ROR2 expression in endometrial cancer cell lines and patient samples. Ectopic expression of ROR2 in vitro inhibited the invasive ability of high grade serous endometrial cancer cells. Therefore, we concluded that ROR2 plays a tumour suppressor role in endometrial cancer and appears to be a diagnostic or therapeutic candidate.

Abstract

The Wnt signalling receptor ROR2 has been identified as a possible therapeutic target in numerous cancers; however, its exact role remains unclear. The aim of this study was to investigate the role of ROR2 in endometrial cancer (EC) and the potential mechanism associated with its altered expression. The association between ROR2 mRNA expression levels and clinicopathological parameters, including overall survival (OS), in EC was analysed in The Cancer Genome Atlas Uterine Corpus Endometrial Carcinoma (TCGA-UCEC) cohort and GEO dataset GSE17025. Four EC cell lines (KLE, MFE-296, Ishikawa and ARK-1) and eight clinical EC samples were analysed for ROR2 methylation via Combined Bisulphite Restriction Analysis (COBRA) and bisulphite genomic sequencing (BGS). In addition, the functional effects of ROR2 overexpression were investigated in Ishikawa and ARK-1 cells following ectopic ROR2 expression. ROR2 promoter methylation or reduced ROR2 expression were both found to correlate with shorter OS, high grade and serous subtype in the TCGA-UCEC and GEO datasets. ROR2 was epigenetically silenced by promoter methylation in both patient samples and cell lines. A significant correlation between ROR2 expression levels and promoter methylation was observed in patient samples (r = −0.797, p = 0.018). ROR2 restoration in ARK-1 significantly decreased invasion ability, with associated changes in epithelial-mesenchymal transition (EMT) markers. ROR2 plays a tumour-suppressor role in EC and is epigenetically suppressed with the development of disease. It may represent a diagnostic or therapeutic candidate for EC.

The WNT/ROR Pathway in Cancer: From Signaling to Therapeutic Intervention

The WNT pathway is one of the major signaling cascades frequently deregulated in human cancer. While research had initially focused on signal transduction centered on β-catenin as a key effector activating a pro-tumorigenic transcriptional response, nowadays it is known that WNT ligands can also induce a multitude of β-catenin-independent cellular pathways. Traditionally, these comprise WNT/planar cell polarity (PCP) and WNT/Ca²⁺ signaling. In addition, signaling via the receptor tyrosine kinase-like orphan receptors (RORs) has gained increasing attention in cancer research due to their overexpression in a multitude of tumor entities. Active WNT/ROR signaling has been linked to processes driving tumor development and progression, such as cell proliferation, survival, invasion, or therapy resistance. In adult tissue, the RORs are largely absent, which has spiked the interest in them for targeted cancer therapy. Promising results in preclinical and initial clinical studies are beginning to unravel the great potential of such treatment approaches. In this review, we summarize seminal findings on the structure and expression of the RORs in cancer, their downstream signaling, and its output in regard to tumor cell function. Furthermore, we present the current clinical anti-ROR treatment strategies and discuss the state-of-the-art, as well as the challenges of the different approaches.

The Wnt/Ca2+ signaling pathway is essential for the regeneration of GABAergic neurons in planarian Dugesia japonica

The growth and differentiation of neurons are critical events in the establishment of proper neuron connectivity and function. Planarians have a remarkable ability to completely regenerate a functional nervous system from a pluripotent stem cell population. Thus, planarians provide a powerful model to identify genes required for neuronal differentiation in vivo. The Wnt/Ca²⁺ signaling pathway is crucial for cancer development, arousing inflammatory responses, and neurodegeneration. We analyzed the expression patterns and RNAi phenotypes for members of the Wnt/Ca²⁺ signaling pathway in the planarian, Dugesia japonica. The expression of DjWnt5a, DjPLC-β, DjCamKII, and DjCaln during regeneration was surprisingly similar and revealing in the regenerated brain. RNAi knockdown of DjWnt5a, DjPLC-β, DjCamKII, and DjCaln led to defects in regenerated brains including brain partial deletions, incompact phenotypes at the posterior of the new brain, and lateral branches, which could not regenerate. Furthermore, the expressions of GAD and the number of GABAergic neurons decreased. Together, these results suggest that the Wnt/Ca²⁺ signaling pathway is required for GABAergic neuron regeneration.

ROR1 is upregulated in endometrial cancer and represents a novel therapeutic target

ROR1 and ROR2 are receptor tyrosine kinases with altered expression in a range of cancers. Silencing ROR1 or ROR2 in different tumour types has been shown to inhibit proliferation and decrease metastatic potential. The aim of this study was to investigate the role of ROR1 and ROR2 in endometrial cancer via immunohistochemistry (IHC) in a large endometrial cancer patient cohort (n = 499) and through in vitro analysis in endometrial cancer cell lines. Correlation was assessed between ROR1/2 expression and clinicopathological parameters. Kaplan Meier curves were produced for 5-year progression free survival (PFS) and overall survival (OS) with low/moderate versus high ROR1/2 intensity. Cox multivariate regression was applied to analyse the effect of selected covariates on the PFS and OS. The effect of ROR1 and/or ROR2 modulation on cell proliferation, adhesion, migration and invasion was analysed in two endometrial cancer cell lines (KLE and MFE-296). We observed a significant decrease in OS and PFS in patients with high ROR1 expression. ROR1 silencing and ROR2 overexpression significantly inhibited proliferation of KLE endometrial cancer cells and decreased migration. This study supports the oncogenic role of ROR1 in endometrial cancer, and warrants investigation of future application of ROR1-targeting therapies in endometrial cancer patients.

Wnt Signaling in Gynecologic Malignancies

Gynecologic malignancies, including ovarian cancer, endometrial cancer, and cervical cancer, affect hundreds of thousands of women worldwide every year. Wnt signaling, specifically Wnt/β-catenin signaling, has been found to play an essential role in many oncogenic processes in gynecologic malignancies, including tumorigenesis, metastasis, recurrence, and chemotherapy resistance. As such, the Wnt/β-catenin signaling pathway has the potential to be a target for effective treatment, improving patient outcomes. In this review, we discuss the evidence supporting the importance of the Wnt signaling pathways in the development, progression, and treatment of gynecologic malignancies.

Canonical and non-canonical Wnt signaling are simultaneously activated by Wnts in colon cancer cells

The Wnt signaling pathway is a crucial regulator of the intestinal epithelium homeostasis and is altered in most colon cancers. While the role of aberrant canonical, β-catenin-dependent Wnt signaling has been well established in colon cancer promotion, much less is known about the role played by noncanonical, β-catenin-independent Wnt signaling in this type of cancer. This work aimed to characterize the noncanonical signal transduction pathway in colon cancer cells. To this end, we used the prototype noncanonical ligand, Wnt5a, in comparison with Wnt3a, the prototype of a canonical β-catenin activating ligand. The analysis of the expression profile of Wnt receptors in colon cancer cell lines showed a clear increase in both level expression and variety of Frizzled receptor types expressed in colon cancer cells compared with non-malignant cells. We found that Wnt5a activates a typical Wnt/Ca++ - noncanonical signaling pathway in colon malignant cells, inducing the hyperphosphorylation of Dvl1, Dvl2 and Dvl3, promoting Ca++ mobilization as a result of phospholipase C (PLC) activation via pertussis toxin-sensitive G-protein, and inducing PLC-dependent cell migration. We also found that while the co-receptor Ror2 tyrosine kinase activity is not required for Ca++ mobilization-induced by Wnt5a, it is required for the inhibitory effects of Wnt5a on the β-catenin-dependent transcriptional activity. Unexpectedly, we found that although the prototype canonical Wnt3a ligand was unique in stimulating the β-catenin-dependent transcriptional activity, it also simultaneously activated PLC, promoted Ca++ mobilization, and induced Rho kinase and PLC-dependent cell migration. Our data indicate, therefore, that a Wnt ligand can activate at the same time the so-called Wnt canonical and noncanonical pathways inducing the formation of complex signaling networks to integrate both pathways in colon cancer cells.

The role of WNT5A and Ror2 in peritoneal membrane injury

Patients on peritoneal dialysis are at risk of developing peritoneal fibrosis and angiogenesis, which can lead to dysfunction of the peritoneal membrane. Recent evidence has identified cross‐talk between transforming growth factor beta (TGFB) and the WNT/β‐catenin pathway to induce fibrosis and angiogenesis. Limited evidence exists describing the role of non‐canonical WNT signalling in peritoneal membrane injury. Non‐canonical WNT5A is suggested to have different effects depending on the receptor environment. WNT5A has been implicated in antagonizing canonical WNT/β‐catenin signalling in the presence of receptor tyrosine kinase‐like orphan receptor (Ror2). We co‐expressed TGFB and WNT5A using adenovirus and examined its role in the development of peritoneal fibrosis and angiogenesis. Treatment of mouse peritoneum with AdWNT5A decreased the submesothelial thickening and angiogenesis induced by AdTGFB. WNT5A appeared to block WNT/β‐catenin signalling by inhibiting phosphorylation of glycogen synthase kinase 3 beta (GSK3B) and reducing levels of total β‐catenin and target proteins. To examine the function of Ror2, we silenced Ror2 in a human mesothelial cell line. We treated cells with AdWNT5A and observed a significant increase in fibronectin compared with AdWNT5A alone. We also analysed fibronectin and vascular endothelial growth factor (VEGF) in a TGFB model of mesothelial cell injury. Both fibronectin and VEGF were significantly increased in response to Ror2 silencing when cells were exposed to TGFB. Our results suggest that WNT5A inhibits peritoneal injury and this is associated with a decrease in WNT/β‐catenin signalling. In human mesothelial cells, Ror2 is involved in regulating levels of fibronectin and VEGF.

Regulation of spermatogonial development by Fsh: The complementary roles of locally produced Igf and Wnt signaling molecules in adult zebrafish testis

Spermatogenesis is a cellular developmental process characterized by the coordinated proliferation and differentiation activities of somatic and germ cells in order to produce a large number of spermatozoa, the cellular basis of male fertility. Somatic cells in the testis, such as Leydig, peritubular myoid and Sertoli cells, provide structural and metabolic support and contribute to the regulatory microenvironment required for proper germ cell survival and development. The pituitary follicle-stimulating hormone (Fsh) is a major endocrine regulator of vertebrate spermatogenesis, targeting somatic cell functions in the testes. In fish, Fsh regulates Leydig and Sertoli cell functions, such as sex steroid and growth factor production, processes that also control the development of spermatogonia, the germ cell stages at the basis of the spermatogenic process. Here, we summarize recent advances in our understanding of mechanisms used by Fsh to regulate the development of spermatogonia. This involves discussing the roles of insulin-like growth factor (Igf) 3 and canonical and non-canonical Wnt signaling pathways. We will also discuss how these locally active regulatory systems interact to maintain testis tissue homeostasis.

Targeting the Versatile Wnt/β-Catenin Pathway in Cancer Biology and Therapeutics: From Concept to Actionable Strategy

This expert review offers a critical synthesis of the latest insights and approaches at targeting the Wnt/β-catenin pathway in various cancers such as colorectal cancer, melanoma, leukemia, and breast and lung cancers. Notably, from organogenesis to cancer, the Wnt/β-catenin signaling displays varied and highly versatile biological functions in animals, with virtually all tissues requiring the Wnt/β-catenin signaling in one way or the other. Aberrant expression of the members of the Wnt/β-catenin has been implicated in many pathological conditions, particularly in human cancers. Mutations in the Wnt/β-catenin pathway genes have been noted in diverse cancers. Biochemical and genetic data support the idea that inhibition of Wnt/β-catenin signaling is beneficial in cancer therapeutics. The interaction of this important pathway with other signaling systems is also noteworthy, but remains as an area for further research and discovery. In addition, formation of different complexes by components of the Wnt/β-catenin pathway and the precise roles of these complexes in the cytoplasmic milieu are yet to be fully elucidated. This article highlights the latest medical technologies in imaging, single-cell omics, use of artificial intelligence (e.g., machine learning techniques), genome sequencing, quantum computing, molecular docking, and computational softwares in modeling interactions between molecules and predicting protein-protein and compound-protein interactions pertinent to the biology and therapeutic value of the Wnt/β-catenin signaling pathway. We discuss these emerging technologies in relationship to what is currently needed to move from concept to actionable strategies in translating the Wnt/β-catenin laboratory discoveries to Wnt-targeted cancer therapies and diagnostics in the clinic.

Wnt Binding Affinity Prediction for Putative Frizzled-Type Cysteine-Rich Domains

Several proteins other than the frizzled receptors (Fzd) and the secreted Frizzled-related proteins (sFRP) contain Fzd-type cysteine-rich domains (CRD). We have termed these domains “putative Fzd-type CRDs”, as the relevance of Wnt signalling in the majority of these is unknown; the RORs, an exception to this, are well known for mediating non-canonical Wnt signalling. In this study, we have predicted the likely binding affinity of all Wnts for all putative Fzd-type CRDs. We applied both our previously determined Wnt‒Fzd CRD binding affinity prediction model, as well as a newly devised model wherein the lipid term was forced to contribute favourably to the predicted binding energy. The results obtained from our new model indicate that certain putative Fzd CRDs are much more likely to bind Wnts, in some cases exhibiting selectivity for specific Wnts. The results of this study inform the investigation of Wnt signalling modulation beyond Fzds and sFRPs.

Robinow syndrome skeletal phenotypes caused by the WNT5AC83S variant are due to dominant interference with chondrogenesis

Heterozygous missense mutations in several genes in the WNT5A signaling pathway cause autosomal dominant Robinow syndrome 1 (DRS1). Our objective was to clarify the functional impact of a missense mutation in WNT5A on the skeleton, one of the main affected tissues in RS. We delivered avian replication competent retroviruses (RCAS) containing human wild-type WNT5A (wtWNT5A), WNT5AC83S variant or GFP/AlkPO4 control genes to the chicken embryo limb. Strikingly, WNT5AC83S consistently caused a delay in ossification and bones were more than 50% shorter and 200% wider than controls. In contrast, bone dimensions in wtWNT5A limbs were slightly affected (20% shorter, 25% wider) but ossification occurred on schedule. The dysmorphology of bones was established during cartilage differentiation. Instead of stereotypical stacking of chondrocytes, the WNT5AC83S-infected cartilage was composed of randomly oriented chondrocytes and that had diffuse, rather than concentrated Prickle staining, both signs of disrupted planar cell polarity (PCP) mechanisms. Biochemical assays revealed that C83S variant was able to activate the Jun N-terminal kinase-PCP pathway similar to wtWNT5A; however, the activity of the variant ligand was influenced by receptor availability. Unexpectedly, the C83S change caused a reduction in the amount of protein being synthesized and secreted, compared to wtWNT5A. Thus, in the chicken and human, RS phenotypes are produced from the C83S mutation, even though the variant protein is less abundant than wtWNT5A. We conclude the variant protein has dominant-negative effects on chondrogenesis leading to limb abnormalities.

Agrin-Lrp4-Ror2 signaling regulates adult hippocampal neurogenesis in mice

Adult neurogenesis in the hippocampus may represent a form of plasticity in brain functions including mood, learning and memory. However, mechanisms underlying neural stem/progenitor cells (NSPCs) proliferation are not well understood. We found that Agrin, a factor critical for neuromuscular junction formation, is elevated in the hippocampus of mice that are stimulated by enriched environment (EE). Genetic deletion of the Agrn gene in excitatory neurons decreases NSPCs proliferation and increases depressive-like behavior. Low-density lipoprotein receptor-related protein 4 (Lrp4), a receptor for Agrin, is expressed in hippocampal NSPCs and its mutation blocked basal as well as EE-induced NSPCs proliferation and maturation of newborn neurons. Finally, we show that Lrp4 interacts with and activates receptor tyrosine kinase-like orphan receptor 2 (Ror2); and Ror2 mutation impairs NSPCs proliferation. Together, these observations identify a role of Agrin-Lrp4-Ror2 signaling for adult neurogenesis, uncovering previously unexpected functions of Agrin and Lrp4 in the brain.

Oral biosciences: The annual review 2018

BACKGROUND

The Journal of Oral Biosciences is devoted to the advancement and dissemination of fundamental knowledge regarding every aspect of oral biosciences.

HIGHLIGHT

This editorial review features summaries of review articles in the fields of "Bone Biology," "Epigenomics," "Periodontium," and "Amelogenesis" in addition to review articles by winners of the Lion Dental Research Award ("Role of non-canonical Wnt signaling pathways in bone resorption," "Mechanisms of orofacial sensory processing in the rat insular cortex," and "Analysis of the mechanism in salivary gland development using gene database") and the Rising Members Award ("Synergistic findings from microbiological and evolutional analyses of virulence factors among pathogenic streptococcal species" and "Free fatty acids may be involved in the pathogenesis of oral-related and cardiovascular diseases"), presented by the Japanese Association for Oral Biology.

CONCLUSION

These reviews published in the Journal of Oral Biosciences have inspired the readers of the Journal to broaden their knowledge of various aspects in the oral biosciences. This editorial review summarizes these exciting articles.

Genetic interactions between Ror2 and Wnt9a, Ror1 and Wnt9a and Ror2 and Ror1: Phenotypic analysis of the limb skeleton and palate in compound mutants

Mutations in the human receptor tyrosine kinase ROR2 are associated with Robinow syndrome (RRS) and brachydactyly type B1. Amongst others, the shortened limb phenotype associated with RRS is recapitulated in Ror2^-/- mutant mice. In contrast, Ror1^-/- mutant mice are viable and show no limb phenotype. Ror1^-/- ;Ror2^-/- double mutants are embryonic lethal, whereas double mutants containing a hypomorphic Ror1 allele (Ror1^hyp ) survive up to birth and display a more severe shortened limb phenotype. Both orphan receptors have been shown to act as possible Wnt coreceptors and to mediate the Wnt5a signal. Here, we analyzed genetic interactions between the Wnt ligand, Wnt9a, and Ror2 or Ror1, as Wnt9a has also been implicated in skeletal development. Wnt9a^-/- single mutants display a mild shortening of the long bones, whereas these are severely shortened in Ror2^-/- mutants. Ror2^-/- ;Wnt9a^-/- double mutants displayed even more severely shortened long bones, and intermediate phenotypes were observed in compound Ror2;Wnt9a mutants. Long bones were also shorter in Ror1^hyp/hyp ;Wnt9a^-/- double mutants. In addition, Ror1^hyp/hyp ;Wnt9a^-/- double mutants displayed a secondary palate cleft phenotype, which was not present in the respective single mutants. Interestingly, 50% of compound mutant pups heterozygous for Ror2 and homozygous mutant for Ror1 also developed a secondary palate cleft phenotype.

Molecular, functional, and gene expression analysis of zebrafish Ror1 receptor

Ror family of receptor tyrosine kinases ROR1 and ROR2 plays crucial roles in animal development by regulating cell proliferation, differentiation, and migration, as well as survival and death by acting as a receptor or co-receptor for Wnt5a and mediating Wnt5a-induced activation. Compared with our extensive understanding of ROR2, our knowledge of ROR1 is limited. In this study, we characterized the zebrafish ror1 gene and determined its temporal and spatial expression and biological activity. Sequence comparison and phylogenetic analyses indicate that its protein structure is similar to its mammalian orthologs. During embryogenesis, the ror1 mRNA levels were relatively low or undetectable at 6 and 9 h postfertilization. In adult fish, ror1 mRNA was most abundantly expressed in the ovary and testis. The levels of ror1 mRNA in non-reproductive system tissues were very low or barely detectable. Spatiotemporal distribution of ror1 and its ligand wnt5a in the ovary was then investigated. Reverse transcription PCR on isolated follicle layers and denuded oocytes demonstrated that both wnt5a and ror1 were exclusively expressed in the oocyte but not in the follicle layers. During oogenesis, the ror1 mRNA levels were relatively low from I to IV stage oocytes and increased dramatically at V stage oocyte. Unlike ror1, the wnt5a mRNA levels were increased gradually from I to V stage oocyte. When Ror1 was co-transfected with Wnt5a and Wnt3a in HEK293T cells, the Wnt3a-induced Wnt reporter activity was inhibited by Ror1 in a dose-dependent manner. Taken together, these results provide new information about the structural and functional conservation, spatial and temporal expression, and biological activity of Ror1 in a fish model organism.

PIK3IP1/TrIP restricts activation of T cells through inhibition of PI3K/Akt

This study demonstrates a role for the transmembrane regulator of PI3K (TrIP) in restricting early T cell activation, at least in part through effects on PI3K. It is also shown that levels of TrIP decrease preceding full T cell activation.

Phosphatidylinositol-3 kinases (PI3Ks) modulate cellular growth, proliferation, and survival; dysregulation of the PI3K pathway can lead to autoimmune disease and cancer. PIK3IP1 (or transmembrane inhibitor of PI3K [TrIP]) is a putative transmembrane regulator of PI3K. TrIP contains an extracellular kringle domain and an intracellular domain with homology to the inter-SH2 domain of the PI3K regulatory subunit p85, but the mechanism of TrIP function is poorly understood. We show that both the kringle and p85-like domains are necessary for TrIP inhibition of PI3K and that TrIP is down-modulated from the surface of T cells during T cell activation. In addition, we present evidence that the kringle domain may modulate TrIP function by mediating oligomerization. Using an inducible knockout mouse model, we show that TrIP-deficient T cells exhibit more robust activation and can mediate clearance of Listeria monocytogenes infection faster than WT mice. Thus, TrIP is a negative regulator of T cell activation and may represent a novel target for immune modulation.

Wnt/PCP controls spreading of Wnt/β-catenin signals by cytonemes in vertebrates

Signaling filopodia, termed cytonemes, are dynamic actin-based membrane structures that regulate the exchange of signaling molecules and their receptors within tissues. However, how cytoneme formation is regulated remains unclear. Here, we show that Wnt/planar cell polarity (PCP) autocrine signaling controls the emergence of cytonemes, and that cytonemes subsequently control paracrine Wnt/β-catenin signal activation. Upon binding of the Wnt family member Wnt8a, the receptor tyrosine kinase Ror2 becomes activated. Ror2/PCP signaling leads to the induction of cytonemes, which mediate the transport of Wnt8a to neighboring cells. In the Wnt-receiving cells, Wnt8a on cytonemes triggers Wnt/β-catenin-dependent gene transcription and proliferation. We show that cytoneme-based Wnt transport operates in diverse processes, including zebrafish development, murine intestinal crypt and human cancer organoids, demonstrating that Wnt transport by cytonemes and its control via the Ror2 pathway is highly conserved in vertebrates.

Communication helps the cells that make up tissues and organs to work together as a team. One way that cells share information with each other as tissues grow and develop is by exchanging signaling proteins. These interact with receptors on the surface of other cells; this causes the cell to change how it behaves.

The Wnt family of signaling proteins orchestrate organ development. Wnt proteins influence which types of cells develop, how fast they divide, and how and when they move. Relatively few cells, or small groups of cells, in developing tissues produce Wnt proteins, while larger groups nearby respond to the signals.

We do not fully understand how Wnt proteins travel between cells, but recent work revealed an unexpected mechanism – cells seem to hand-deliver their messages. Finger-like structures called cytonemes grow out of the cell membrane and carry Wnt proteins to their destination. If the cytonemes do not form properly the target cells do not behave correctly, which can lead to severe tissue malformation.

Mattes et al. have now investigated how cytonemes form using a combination of state-of-the-art genetic and high-resolution imaging techniques. In initial experiments involving zebrafish cells that were grown in the laboratory, Mattes et al. found that the Wnt proteins kick start their own transport; before they travel to their destination, they act on the cells that made them. A Wnt protein called Wnt8a activates the receptor Ror2 on the surface of the signal-producing cell. Ror2 then triggers signals inside the cell that begin the assembly of the cytonemes. The more Ror2 is activated, the more cytonemes the cell makes, and the more Wnt signals it can send out.

This mechanism operates in various tissues: Ror2 also controls the cytoneme transport process in living zebrafish embryos, the mouse intestine and human stomach tumors. This knowledge will help researchers to develop new ways to control Wnt signaling, which could help to produce new treatments for diseases ranging from cancers (for example in the stomach and bowel) to degenerative diseases such as Alzheimer’s disease.

Aberrant Wnt Signaling Pathway in the Hematopoietic Stem/Progenitor Compartment in Experimental Leukemic Animal

The evolutionarily conserved Wnt signaling pathway regulates physiological hematopoiesis, a process of formation of blood cells and has been shown to play crucial role in the development of both myeloid and lymphoid malignancies. The Wnt signaling pathway can be broadly divided into canonical and non-canonical pathways. In the present study, we investigated the pathobiology of leukemia by studying the expression profile of Wnt proteins, receptors, key signaling intermediates and endogenous Wnt antagonist involved in canonical and non-canonical pathways in the bone marrow (BM) hematopoietic stem/progenitor cell (HSPC) compartment of experimental leukemic mice. Cell adhesion molecule N-Cadherin and leukemic BM microenvironment with reference to Wnt were also studied. We used ENU, a potent carcinogen, to induce leukemia in wild type Swiss albino mice and malignant transformation was cofirmed by peripheral blood and BM studies. Flow cytometric expression analysis revealed profound up-regulation of canonical Wnt3a/β-catenin/CyclinD1 signaling axis along with N-Cadherin whereas down-regulation of non-canonical Wnt5a/Ca²⁺/CaMKII signaling axis in the leukemic HSPC compartment. Subsequent use of anti-Wnt3a antibody in the in vitro clonogenicity assay uncovered that anti-Wnt3a antibody preferentially inhibited the growth and number of the primitive leukemic hematopoietic CFU-GEMM and BFU-E colonies. Stromal cells derived from the leukemic BM also exhibited aberrant Wnt3a and Wnt5a protein expression. Taken together, alteration of canonical and non-canonical Wnt signaling pathways in the HSPC compartment along with classical Wnt protein expression pattern in the leukemic stromal microenvironment resulted in progression of leukemia.

Identification of a WNT5A-Responsive Degradation Domain in the Kinesin Superfamily Protein KIF26B

Noncanonical WNT pathways function independently of the β-catenin transcriptional co-activator to regulate diverse morphogenetic and pathogenic processes. Recent studies showed that noncanonical WNTs, such as WNT5A, can signal the degradation of several downstream effectors, thereby modulating these effectors' cellular activities. The protein domain(s) that mediates the WNT5A-dependent degradation response, however, has not been identified. By coupling protein mutagenesis experiments with a flow cytometry-based degradation reporter assay, we have defined a protein domain in the kinesin superfamily protein KIF26B that is essential for WNT5A-dependent degradation. We found that a human disease-causing KIF26B mutation located at a conserved amino acid within this domain compromises the ability of WNT5A to induce KIF26B degradation. Using pharmacological perturbation, we further uncovered a role of glycogen synthase kinase 3 (GSK3) in WNT5A regulation of KIF26B degradation. Lastly, based on the identification of the WNT5A-responsive domain, we developed a new reporter system that allows for efficient profiling of WNT5A-KIF26B signaling activity in both somatic and stem cells. In conclusion, our study identifies a new protein domain that mediates WNT5A-dependent degradation of KIF26B and provides a new tool for functional characterization of noncanonical WNT5A signaling in cells.

The biochemistry, signalling and disease relevance of RYK and other WNT-binding receptor tyrosine kinases

The receptor tyrosine kinases (RTKs) are a well-characterized family of growth factor receptors that have central roles in human disease and are frequently therapeutically targeted. The RYK, ROR, PTK7 and MuSK subfamilies make up an understudied subset of WNT-binding RTKs. Numerous developmental, stem cell and pathological roles of WNTs, in particular WNT5A, involve signalling via these WNT receptors. The WNT-binding RTKs have highly context-dependent signalling outputs and stimulate the β-catenin-dependent, planar cell polarity and/or WNT/Ca²⁺ pathways. RYK, ROR and PTK7 members have a pseudokinase domain in their intracellular regions. Alternative signalling mechanisms, including proteolytic cleavage and protein scaffolding functions, have been identified for these receptors. This review explores the structure, signalling, physiological and pathological roles of RYK, with particular attention paid to cancer and the possibility of therapeutically targeting RYK. The other WNT-binding RTKs are compared with RYK throughout to highlight the similarities and differences within this subset of WNT receptors.

Kinesin superfamily protein Kif26b links Wnt5a-Ror signaling to the control of cell and tissue behaviors in vertebrates

Wnt5a-Ror signaling constitutes a developmental pathway crucial for embryonic tissue morphogenesis, reproduction and adult tissue regeneration, yet the molecular mechanisms by which the Wnt5a-Ror pathway mediates these processes are largely unknown. Using a proteomic screen, we identify the kinesin superfamily protein Kif26b as a downstream target of the Wnt5a-Ror pathway. Wnt5a-Ror, through a process independent of the canonical Wnt/β-catenin-dependent pathway, regulates the cellular stability of Kif26b by inducing its degradation via the ubiquitin-proteasome system. Through this mechanism, Kif26b modulates the migratory behavior of cultured mesenchymal cells in a Wnt5a-dependent manner. Genetic perturbation of Kif26b function in vivo caused embryonic axis malformations and depletion of primordial germ cells in the developing gonad, two phenotypes characteristic of disrupted Wnt5a-Ror signaling. These findings indicate that Kif26b links Wnt5a-Ror signaling to the control of morphogenetic cell and tissue behaviors in vertebrates and reveal a new role for regulated proteolysis in noncanonical Wnt5a-Ror signal transduction.

WNT signaling - lung cancer is no exception

Since the initial discovery of the oncogenic activity of WNT ligands our understanding of the complex roles for WNT signaling pathways in lung cancers has increased substantially. In the current review, the various effects of activation and inhibition of the WNT signaling pathways are summarized in the context of lung carcinogenesis. Recent evidence regarding WNT ligand transport mechanisms, the role of WNT signaling in lung cancer angiogenesis and drug transporter regulation and the importance of microRNA and posttranscriptional regulation of WNT signaling are also reviewed.

The Wnt5a Receptor, Receptor Tyrosine Kinase-Like Orphan Receptor 2, Is a Predictive Cell Surface Marker of Human Mesenchymal Stem Cells with an Enhanced Capacity for Chondrogenic Differentiation

Multipotent mesenchymal stem cells (MSCs) have enormous potential in tissue engineering and regenerative medicine. However, until now, their development for clinical use has been severely limited as they are a mixed population of cells with varying capacities for lineage differentiation and tissue formation. Here, we identify receptor tyrosine kinase‐like orphan receptor 2 (ROR2) as a cell surface marker expressed by those MSCs with an enhanced capacity for cartilage formation. We generated clonal human MSC populations with varying capacities for chondrogenesis. ROR2 was identified through screening for upregulated genes in the most chondrogenic clones. When isolated from uncloned populations, ROR2+ve MSCs were significantly more chondrogenic than either ROR2–ve or unfractionated MSCs. In a sheep cartilage‐repair model, they produced significantly more defect filling with no loss of cartilage quality compared with controls. ROR2+ve MSCs/perivascular cells were present in developing human cartilage, adult bone marrow, and adipose tissue. Their frequency in bone marrow was significantly lower in patients with osteoarthritis (OA) than in controls. However, after isolation of these cells and their initial expansion in vitro, there was greater ROR2 expression in the population derived from OA patients compared with controls. Furthermore, osteoarthritis‐derived MSCs were better able to form cartilage than MSCs from control patients in a tissue engineering assay. We conclude that MSCs expressing high levels of ROR2 provide a defined population capable of predictably enhanced cartilage production. Stem Cells2017;35:2280–2291