Planar cell polarity in development and disease

An AIE-TICT fluorescence probe cascade responsive to H2S, polarity and viscosity to track microenvironment changes in cellular model of ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury is a common cause of cardiovascular and cerebrovascular diseases. The reoxygenation during reperfusion leads to an overproduction of reactive oxygen species (ROS). As an antioxidant, H2S can scavenge ROS to inhibit oxidative stress and inflammatory reaction, thus attenuating ischemia-reperfusion injury. In this process, the changes of cellular microenvironment (polarity or viscosity) have not been fully discussed. In order to real-time track the changes of cellular microenvironment during the treatment of ischemia-reperfusion injury with H2S. It is necessary to develop highly selective and sensitive probes that can cascade response to hydrogen sulfide and cellular microenvironment.

RESULTS

We designed and synthesized a fluorescent probe TPEC-DNBS which can produce cascade response to H2S and microenvironment. An intermediate TPEC-OH is produced after highly selective and sensitive response to H2S, which can further respond to polarity and viscosity. In addition, due to the aggregation-induced emission (AIE) and twisted intramolecular charge transfer (TICT) effects, polarity can promote the fluorescence emission wavelength and intensity of TPEC-OH to produce double response characteristics, and its change trend (from weak green fluorescence at low polarity to strong red fluorescence at high polarity) is opposite to that of traditional polar probes (from strong green fluorescence at low polarity to weak red fluorescence at high polarity). Viscosity can only induce the change of fluorescence intensity. By constructing the cardiomyocyte model and hepatocyte model of ischemia-reperfusion, we further prove that after ischemia-reperfusion injury, the cells are in an environment of low polarity, and the microenvironment can be recovered after H2S treatment.

SIGNIFICANCE

An AIE-TICT fluorescence probe capable of cascading responses to H2S, polarity and viscosity was constructed by using tetraphenylethylene and coumarin moieties. This probe provides a more intuitive and convenient condition for real-time tracking the changes of cellular microenvironment (polarity or viscosity) before and after H2S treatment of ischemia-reperfusion injury.

The ultimate microbial composition for correcting Th17/Treg cell imbalance and lipid metabolism disorders in osteoporosis

Osteoporosis is a systemic bone disease characterised by decreased bone mass and a deteriorated bone microstructure, leading to increased bone fragility and fracture risk. Disorders of the intestinal microbiota may be key inducers of osteoporosis. Furthermore, such disorders may contribute to osteoporosis by influencing immune function and lipid metabolism. Therefore, in this review, we aimed to summarise the molecular mechanisms through which the intestinal microbiota affect the onset and development of osteoporosis by regulating Th17/Treg imbalance and lipid metabolism disorders. We also discussed the regulatory mechanisms underlying the effect of intestinal microbiota-related modulators on Th17/Treg imbalance and lipid metabolism disorders in osteoporosis, to explore new molecular targets for its treatment and provide a theoretical basis for clinical management.

Structural basis of human VANGL-PRICKLE interaction

Planar cell polarity (PCP) is an evolutionarily conserved process for development and morphogenesis in metazoans. The well-organized polarity pattern in cells is established by the asymmetric distribution of two core protein complexes on opposite sides of the cell membrane. The Van Gogh-like (VANGL)-PRICKLE (PK) pair is one of these two key regulators; however, their structural information and detailed functions have been unclear. Here, we present five cryo-electron microscopy structures of human VANGL1, VANGL2, and their complexes with PK1 at resolutions of 2.2-3.0 Å. Through biochemical and cell imaging experiments, we decipher the molecular details of the VANGL-PK interaction. Furthermore, we reveal that PK1 can target VANGL-containing intracellular vesicles to the peripheral cell membrane. These findings provide a solid foundation to understand the explicit interaction between VANGL and PK while opening new avenues for subsequent studies of the PCP pathway.

Cryo-EM structure and oligomerization of the human planar cell polarity core protein Vangl1

Vangl is a planar cell polarity (PCP) core protein essential for aligned cell orientation along the epithelial plane perpendicular to the apical-basal direction, which is important for tissue morphogenesis, development and collective cell behavior. Mutations in Vangl are associated with developmental defects, including neural tube defects (NTDs), according to human cohort studies of sporadic and familial cases. The complex mechanisms underlying Vangl-mediated PCP signaling or Vangl-associated human congenital diseases have been hampered by the lack of molecular characterizations of Vangl. Here, we show biochemical and structural evidence that human Vangl1 oligomerizes as dimers of trimers, and that the dimerization of trimers promotes binding to the PCP effector Prickle1 (Pk1) in vitro. Mapping of human disease-associated point mutations suggests potential pathological mechanisms and paves the way for future studies on the importance of lipid binding, central vestibule and oligomerization of Vangl, thereby providing insights into the molecular mechanisms of the PCP signaling pathway.

The geometric basis of epithelial convergent extension

Shape changes of epithelia during animal development, such as convergent extension, are achieved through the concerted mechanical activity of individual cells. While much is known about the corresponding large-scale tissue flow and its genetic drivers, fundamental questions regarding local control of contractile activity on the cellular scale and its embryo-scale coordination remain open. To address these questions, we develop a quantitative, model-based analysis framework to relate cell geometry to local tension in recently obtained time-lapse imaging data of gastrulating Drosophila embryos. This analysis systematically decomposes cell shape changes and T1 rearrangements into internally driven, active, and externally driven, passive, contributions. Our analysis provides evidence that germ band extension is driven by active T1 processes that self-organize through positive feedback acting on tensions. More generally, our findings suggest that epithelial convergent extension results from the controlled transformation of internal force balance geometry which combines the effects of bottom-up local self-organization with the top-down, embryo-scale regulation by gene expression.

Radially patterned morphogenesis of murine hair follicle placodes ensures robust epithelial budding

The bending of simple cellular sheets into complex three-dimensional (3D) forms requires developmental patterning cues to specify where deformations occur, but how positional information directs morphological change is poorly understood. Here, we investigate how morphogen signaling and cell fate diversification contribute to the morphogenesis of murine hair placodes, in which collective cell movements transform radially symmetric primordia into bilaterally symmetric tubes. Through live imaging and 3D volumetric reconstructions, we demonstrate that Wnt and Shh establish radial patterns of cell fate, cell morphology, and movement within developing placodes. Cell fate diversity at different radial positions provides unique and essential contributions to placode morphogenesis. Further, we show that downstream of radial patterning, gradients of classical cadherin expression are required for efficient epithelial rearrangements. Given that the transformation of epithelial discs into 3D tubes is a common morphological motif used to shape diverse organ primordia, mechanisms of radially patterned morphogenesis are likely highly conserved across evolution.

Disrupted endosomal trafficking of the Vangl-Celsr polarity complex underlies congenital anomalies in trachea-esophageal morphogenesis

Disruptions in foregut morphogenesis can result in life-threatening conditions where the trachea and esophagus fail to separate properly, such as esophageal atresia (EA) and tracheoesophageal fistulas (TEF). The developmental basis of these congenital anomalies is poorly understood, but recent genome sequencing reveals that de novo variants in intracellular trafficking genes are enriched in EA/TEF patients. Here, we confirm that mutation of orthologous genes in Xenopus disrupts trachea-esophageal separation similar to EA/TEF patients. We show that the Rab11a recycling endosome pathway is required to localize Vangl-Celsr polarity complexes at the luminal cell surface where opposite sides of the foregut tube fuse. Partial loss of endosome trafficking or Vangl-Celsr complexes disrupts epithelial polarity and mutant cells accumulate at the fusion point, fail to downregulate Cadherin, and do not separate into distinct trachea and esophagus. These data provide insights into the mechanisms of congenital anomalies and general paradigms of tissue fusion during organogenesis.

Wnt Signaling in Hepatocellular Carcinoma: Biological Mechanisms and Therapeutic Opportunities

Hepatocellular carcinoma (HCC), characterized by significant morbidity and mortality rates, poses a substantial threat to human health. The expression of ligands and receptors within the classical and non-classical Wnt signaling pathways plays an important role in HCC. The Wnt signaling pathway is essential for regulating multiple biological processes in HCC, including proliferation, invasion, migration, tumor microenvironment modulation, epithelial-mesenchymal transition (EMT), stem cell characteristics, and autophagy. Molecular agents that specifically target the Wnt signaling pathway have demonstrated significant potential for the treatment of HCC. However, the precise mechanism by which the Wnt signaling pathway interacts with HCC remains unclear. In this paper, we review the alteration of the Wnt signaling pathway in HCC, the mechanism of Wnt pathway action in HCC, and molecular agents targeting the Wnt pathway. This paper provides a theoretical foundation for identifying molecular agents targeting the Wnt pathway in hepatocellular carcinoma.

The early transition to cold-induced browning in mouse subcutaneous white adipose tissue (scWAT) involves proteins related to nerve remodeling, cytoskeleton, mitochondria, and immune cells

White adipose tissue (WAT) is a dynamic organ capable of remodelling in response to metabolic state. For example, in response to stimuli such as cold exposure, WAT can develop inducible brown adipocytes ('browning') capable of non-shivering thermogenesis, through concurrent changes to mitochondrial content and function. This is aided by increased neurite outgrowth and angiogenesis across the tissue, providing the needed neurovascular supply for uncoupling protein 1 activation. While several RNA-sequencing studies have been performed in WAT, including newer single cell and single nuclei studies, little work has been done to investigate changes to the adipose proteome, particularly during dynamic periods of tissue remodelling such as cold stimulation. Here, we conducted a comprehensive proteomic analysis of inguinal subcutaneous (sc) WAT during the initial 'browning' period of 24 or 72hrs of cold exposure in mice. We identified four significant pathways impacted by cold stimulation that are involved in tissue remodelling, which included mitochondrial function and metabolism, cytoskeletal remodelling, the immune response, and the nervous system. Taken together, we found that early changes in the proteome of WAT with cold stimulation predicted later structural and functional changes in the tissue that are important for tissue and whole-body remodelling to meet energetic and metabolic needs.

Directional ciliary beats across epithelia require Ccdc57-mediated coupling between axonemal orientation and basal body polarity

Motile cilia unify their axonemal orientations (AOs), or beat directions, across epithelia to drive liquid flows. This planar polarity results from cytoskeleton-driven swiveling of basal foot (BF), a basal body (BB) appendage coincident with the AO, in response to regulatory cues. How and when the BF-AO relationship is established, however, are unaddressed. Here, we show that the BF-AO coupling occurs during rotational polarizations of BBs and requires Ccdc57. Ccdc57 localizes on BBs as a rotationally-asymmetric punctum, which polarizes away from the BF in BBs having achieved the rotational polarity to probably fix the BF-AO relationship. Consistently, Ccdc57-deficient ependymal multicilia lack the BF-AO coupling and display directional beats at only single cell level. Ccdc57 -/- tracheal multicilia also fail to fully align their BFs. Furthermore, Ccdc57 -/- mice manifest severe hydrocephalus, due to impaired cerebrospinal fluid flow, and high mortality. These findings unravel mechanisms governing the planar polarity of epithelial motile cilia.

Functional annotation of the Hippo pathway somatic mutations in human cancers

The Hippo pathway is commonly altered in cancer initiation and progression; however, exactly how this pathway becomes dysregulated to promote human cancer development remains unclear. Here we analyze the Hippo somatic mutations in the human cancer genome and functionally annotate their roles in targeting the Hippo pathway. We identify a total of 85 loss-of-function (LOF) missense mutations for Hippo pathway genes and elucidate their underlying mechanisms. Interestingly, we reveal zinc-finger domain as an integral structure for MOB1 function, whose LOF mutations in head and neck cancer promote tumor growth. Moreover, the schwannoma/meningioma-derived NF2 LOF mutations not only inhibit its tumor suppressive function in the Hippo pathway, but also gain an oncogenic role for NF2 by activating the VANGL-JNK pathway. Collectively, our study not only offers a rich somatic mutation resource for investigating the Hippo pathway in human cancers, but also provides a molecular basis for Hippo-based cancer therapy.

Identification of a non-canonical planar cell polarity pathway triggered by light in the developing mouse retina

The coordinated spatial arrangement of organelles within a tissue plane, known as planar cell polarity (PCP), is critical for organ development and function. Gradients of morphogens and their receptors typically set-up PCP, but whether non-molecular cues, akin to phototropism in plants, also play a part remains unknown. Here, we report that basal bodies of newborn photoreceptor cells in the mouse retina are positioned centrally on the apical surface but then move laterally during the first postnatal week, generating cell-intrinsic asymmetry in the retinal plane. After 1 week, when the eyes open, basal bodies of cone cilia, but not rods, become coordinated across the plane to face the center of the retina. We further show that light is essential for cone PCP, triggering a cascade in which cone transducin interacts with the G-protein-signaling modulator protein 2 (GPSM2) to establish PCP. This work identifies a non-canonical PCP pathway initiated by light.

Distinct roles of Kif6 and Kif9 in mammalian ciliary trafficking and motility

Ciliary beat and intraflagellar transport depend on dynein and kinesin motors. The kinesin-9 family members Kif6 and Kif9 are implicated in motile cilia motilities across protists and mammals. How they function and whether they act redundantly, however, remain unclear. Here, we show that Kif6 and Kif9 play distinct roles in mammals. Kif6 forms puncta that move bidirectionally along axonemes, whereas Kif9 appears to oscillate regionally on the ciliary central apparatus. Consistently, only Kif6 displays microtubule-based motor activity in vitro, and its ciliary localization requires its ATPase activity. Kif6 deficiency in mice disrupts coordinated ciliary beat across ependymal tissues and impairs cerebrospinal fluid flow, resulting in severe hydrocephalus and high mortality. Kif9 deficiency causes mild hydrocephalus without obviously affecting the ciliary beat or the lifespan. Kif6-/- and Kif9-/- males are infertile but exhibit oligozoospermia with poor sperm motility and defective forward motion of sperms, respectively. These results suggest Kif6 as a motor for cargo transport and Kif9 as a central apparatus regulator.

Planar cell polarity zebrafish models of congenital scoliosis reveal underlying defects in notochord morphogenesis

Congenital scoliosis (CS) is a type of vertebral malformation for which the etiology remains elusive. The notochord is pivotal for vertebrae development, but its role in CS is still understudied. Here, we generated a zebrafish knockout of ptk7a, a planar cell polarity (PCP) gene that is essential for convergence and extension (C&E) of the notochord, and detected congenital scoliosis-like vertebral malformations (CVMs). Maternal zygotic ptk7a mutants displayed severe C&E defects of the notochord. Excessive apoptosis occurred in the malformed notochord, causing a significantly reduced number of vacuolated cells, and compromising the mechanical properties of the notochord. The latter manifested as a less-stiff extracellular matrix along with a significant reduction in the number of the caveolae and severely loosened intercellular junctions in the vacuolated region. These defects led to focal kinks, abnormal mineralization, and CVMs exclusively at the anterior spine. Loss of function of another PCP gene, vangl2, also revealed excessive apoptosis in the notochord associated with CVMs. This study suggests a new model for CS pathogenesis that is associated with defects in notochord C&E and highlights an essential role of PCP signaling in vertebrae development.

Linking planar polarity signalling to actomyosin contractility during vertebrate neurulation

Actomyosin contractility represents an ancient feature of eukaryotic cells participating in many developmental and homeostasis events, including tissue morphogenesis, muscle contraction and cell migration, with dysregulation implicated in various pathological conditions, such as cancer. At the molecular level, actomyosin comprises actin bundles and myosin motor proteins that are sensitive to posttranslational modifications like phosphorylation. While the molecular components of actomyosin are well understood, the coordination of contractility by extracellular and intracellular signals, particularly from cellular signalling pathways, remains incompletely elucidated. This study focuses on WNT/planar cell polarity (PCP) signalling, previously associated with actomyosin contractility during vertebrate neurulation. Our investigation reveals that the main cytoplasmic PCP proteins, Prickle and Dishevelled, interact with key actomyosin components such as myosin light chain 9 (MLC9), leading to its phosphorylation and localized activation. Using proteomics and microscopy approaches, we demonstrate that both PCP proteins actively control actomyosin contractility through Rap1 small GTPases in relevant in vitro and in vivo models. These findings unveil a novel mechanism of how PCP signalling regulates actomyosin contractility through MLC9 and Rap1 that is relevant to vertebrate neurulation.

Vangl2 regulates intercellular junctions by remodeling actin-based cytoskeleton through the Rock signaling pathway during spermatogenesis in Eriocheir sinensis

As a key planar cell polarity protein, Van Gogh-like 2 (Vangl2) is essential for mammalian spermatogenesis. As a decapod crustacean, Eriocheir sinensis exhibits distinct spermatogenic processes due to its unique seminiferous tubule morphology and hemolymph-testis barrier (HTB). To determine whether Vangl2 performs analogous functions in E. sinensis, we identified the Es-Vangl2. Es-Vangl2 exhibited high expression and wide distribution in the testes, indicating its crucial involvement in spermatogenesis. Following targeted knockdown of Es-Vangl2in vivo, the structure of seminiferous tubules was disrupted, characterized by vacuolization of the germinal zone and obstruction of spermatozoon release. Concurrently, the integrity of the HTB was compromised, accompanied by reduced expression and aberrant localization of junction proteins. More importantly, the regulatory influence of Es-Vangl2 was manifested through modulating the organization of microfilaments, a process mediated by epidermal growth factor receptor pathway substrate 8 (Eps8). Further studies demonstrated that these phenotypes resulting from Es-Vangl2 knockdown were attributed to the inhibition of Rock signaling pathway activity, which was verified by the Es-Rock interference and Y27632 inhibition assays. In summary, the findings highlight the pivotal role of Es-Vangl2 in stabilizing HTB integrity by regulating Eps8-mediated actin remodeling through the Rock signaling pathway in the spermatogenesis of E. sinensis.

Carboxy-terminal polyglutamylation regulates signaling and phase separation of the Dishevelled protein

Polyglutamylation is a reversible posttranslational modification that is catalyzed by enzymes of the tubulin tyrosine ligase-like (TTLL) family. Here, we found that TTLL11 generates a previously unknown type of polyglutamylation that is initiated by the addition of a glutamate residue to the free C-terminal carboxyl group of a substrate protein. TTLL11 efficiently polyglutamylates the Wnt signaling protein Dishevelled 3 (DVL3), thereby changing the interactome of DVL3. Polyglutamylation increases the capacity of DVL3 to get phosphorylated, to undergo phase separation, and to act in the noncanonical Wnt pathway. Both carboxy-terminal polyglutamylation and the resulting reduction in phase separation capacity of DVL3 can be reverted by the deglutamylating enzyme CCP6, demonstrating a causal relationship between TTLL11-mediated polyglutamylation and phase separation. Thus, C-terminal polyglutamylation represents a new type of posttranslational modification, broadening the range of proteins that can be modified by polyglutamylation and providing the first evidence that polyglutamylation can modulate protein phase separation.

From polarity to pathology: Decoding the role of cell orientation in osteoarthritis

Cell polarity refers to the orientation of tissue and organelles within a cell and the direction of its function. It is one of the most critical characteristics of metazoans. The development, growth, and functional tissue distribution are closely related to holistic tissue or organ homeostasis. However, the connection between cell polarity and osteoarthritis (OA) is less well-known. In OA, multiple chondrocyte clusters and tissue disorganisation can be observed in the degraded cartilage tissue. The excessive upregulation of the planar cell polarity (PCP) signalling pathway leads to the loss of cell polarity and organisation in OA progression and aetiology. Recent research has become increasingly aware of the importance of cell polarity and its correlation with OA. Several cell polarity-related treatments have shed light on OA. A thorough understanding of cell polarity and OA would provide more insights for future investigations to treat this worldwide disease.

The translational potential of this article

Understanding cell polarity, associated signalling pathways, organelle changes, and cell movement in the development of OA could lead to advances in precision medicine and enhanced treatment strategies for OA patients.

Differential Sensitivity of Midline Patterning to Mitosis during and after Primitive Streak Extension

Background

Midline establishment is a fundamental process during early embryogenesis for Bilaterians . Midline patterning in nonamniotes can occur without mitosis, through Planar Cell Polarity (PCP) signaling. By contrast, amniotes utilize both cell proliferation and PCP signaling for patterning early midline landmark, the primitive streak (PS). This study examined their roles for midline patterning at post PS-extension.

Results

In contrast to PS extension stages, embryos under mitotic arrest during the post PS-extension preserved notochord (NC) extension and Hensen's node (HN)/PS regression judged by both morphology and marker genes, although they became shorter, and laterality was lost. Remarkably, no or background level of expression was detected for the majority of PCP core components in the NC-HN-PS area at post PS-extension stages, except for robustly detected prickle-1 . Morpholino knockdown of Prickle-1 showed little influence on midline patterning, except for suppressed embryonic growth. Lastly, associated with mitotic arrest-induced size reduction, midline tissue cells displayed hypertrophy.

Conclusion

Thus, the study has identified at least two distinct mitosis sensitivity phases during early midline pattering: One is PS extension that requires both mitosis and PCP, and the other is mitotic arrest-resistant midline patterning with little influence by PCP at post PS-extension stages.

Flamingo participates in multiple models of cell competition

The growth and survival of cells with different fitness, such as those with a proliferative advantage or a deleterious mutation, is controlled through cell competition. During development, cell competition enables healthy cells to eliminate less fit cells that could jeopardize tissue integrity, and facilitates the elimination of pre-malignant cells by healthy cells as a surveillance mechanism to prevent oncogenesis. Malignant cells also benefit from cell competition to promote their expansion. Despite its ubiquitous presence, the mechanisms governing cell competition, particularly those common to developmental competition and tumorigenesis, are poorly understood. Here, we show that in Drosophila, the planar cell polarity (PCP) protein Flamingo (Fmi) is required by winners to maintain their status during cell competition in malignant tumors to overtake healthy tissue, in early pre-malignant cells when they overproliferate among wildtype cells, in healthy cells when they later eliminate pre-malignant cells, and by supercompetitors as they compete to occupy excessive territory within wildtype tissues. "Would-be" winners that lack Fmi are unable to over-proliferate, and instead become losers. We demonstrate that the role of Fmi in cell competition is independent of PCP, and that it uses a distinct mechanism that may more closely resemble one used in other less well-defined functions of Fmi.

Emergence of planar cell polarity from the interplay of local interactions and global gradients

Planar cell polarity (PCP) - tissue-scale alignment of the direction of asymmetric localization of proteins at the cell-cell interface - is essential for embryonic development and physiological functions. Abnormalities in PCP can result in developmental imperfections, including neural tube closure defects and misaligned hair follicles. Decoding the mechanisms responsible for PCP establishment and maintenance remains a fundamental open question. While the roles of various molecules - broadly classified into 'global' and 'local' modules - have been well-studied, their necessity and sufficiency in explaining PCP and connecting their perturbations to experimentally observed patterns have not been examined. Here, we develop a minimal model that captures the proposed features of PCP establishment - a global tissue-level gradient and local asymmetric distribution of protein complexes. The proposed model suggests that while polarity can emerge without a gradient, the gradient not only acts as a global cue but also increases the robustness of PCP against stochastic perturbations. We also recapitulated and quantified the experimentally observed features of swirling patterns and domineering non-autonomy, using only three free model parameters - rate of protein binding to membrane, the concentration of PCP proteins, and the gradient steepness. We explain how self-stabilizing asymmetric protein localizations in the presence of tissue-level gradient can lead to robust PCP patterns and reveal minimal design principles for a polarized system.

Cluster Assembly Dynamics Drive Fidelity of Planar Cell Polarity Polarization

The planar cell polarity (PCP) signaling pathway polarizes epithelial cells in the tissue plane by segregating distinct molecular subcomplexes to opposite sides of each cell, where they interact across intercellular junctions to form asymmetric clusters. The role of clustering in this process is unknown. We hypothesized that protein cluster size distributions could be used to infer the underlying molecular dynamics and function of cluster assembly and polarization. We developed a method to count the number of monomers of core PCP proteins within individual clusters in live animals, and made measurements over time and space in wild type and in strategically chosen mutants. The data demonstrate that clustering is required for polarization, and together with mathematical modeling provide evidence that cluster assembly dynamics dictate that larger clusters are more likely to be strongly asymmetric and correctly oriented. We propose that cluster assembly dynamics thereby drive fidelity of cell- and tissue-level polarization.

4D pathology: translating dynamic epithelial tubulogenesis to prostate cancer pathology

The Gleason score is the gold standard for grading of prostate cancer (PCa) and is assessed by assigning specific grades to different microscopical growth patterns. Aside from the Gleason grades, individual growth patterns such as cribriform architecture were recently shown to have independent prognostic value for disease outcome. PCa grading is performed on static tissue samples collected at one point in time, whereas in vivo epithelial tumour structures are dynamically invading, branching and expanding into the surrounding stroma. Due to the lack of models that are able to track human PCa microscopical developments over time, our understanding of underlying tissue dynamics is sparse. We postulate that human PCa expansion utilizes embryonic and developmental tubulogenetic pathways. The aim of this study is to provide a comprehensive overview of developmental pathways of normal epithelial tubule formation, elongation, and branching, and relate those to the static microscopical PCa growth patterns observed in daily clinical practise. This study could provide a rationale for the discerned pathological interobserver variability and the clinical outcome differences between PCa growth patterns.

SLMAP3 is crucial for organogenesis through mechanisms involving primary cilia formation

SLMAP3 is a constituent of the centrosome and is known to assemble with the striatin-interacting phosphatase and kinase (STRIPAK) complex, where it has been reported to repress Hippo signalling. The global knockout of SLMAP3 in mice results in embryonic/perinatal lethality and stunted growth without changes in the phosphorylation status of YAP. Diverse phenotypes present in the SLMAP3-/- embryos include reduced body axis, small and abnormal organs resembling defects in planar cell polarity (PCP) signalling, while also displaying the notable polycystic kidneys, a known manifestation of ciliopathies. Analysis of cell polarity in primary mouse embryonic fibroblasts (MEFs) including cell migration, orientation and mitotic spindle angle did not reveal any changes due to SLMAP3 loss in these cells, although the expression of DVL3 was significantly reduced. Furthermore, MEFs lacking FGFR1OP2 or STRN3, two other STRIPAK members, did not reveal any significant changes in any of these parameters either. Significant changes in the number of ciliated cells and primary cilium length in SLMAP3 and FGFR1OP2 deficient MEFs were evident, while a reduced primary cilium length was notable in chondrocytes of SLMAP3 deficient embryos. Our findings suggest that SLMAP3 is essential for mouse embryogenesis through novel mechanisms involving the primary cilium/PCP and protein stability independent of Hippo signalling.

Ventral body wall closure: Mechanistic insights from mouse models and translation to human pathology

The ventral body wall (VBW) that encloses the thoracic and abdominal cavities arises by extensive cell movements and morphogenetic changes during embryonic development. These morphogenetic processes include embryonic folding generating the primary body wall; the initial ventral cover of the embryo, followed by directed mesodermal cell migrations, contributing to the secondary body wall. Clinical anomalies in VBW development affect approximately 1 in 3000 live births. However, the cell interactions and critical cellular behaviors that control VBW development remain little understood. Here, we describe the embryonic origins of the VBW, the cellular and morphogenetic processes, and key genes, that are essential for VBW development. We also provide a clinical overview of VBW anomalies, together with environmental and genetic influences, and discuss the insight gained from over 70 mouse models that exhibit VBW defects, and their relevance, with respect to human pathology. In doing so we propose a phenotypic framework for researchers in the field which takes into account the clinical picture. We also highlight cases where there is a current paucity of mouse models for particular clinical defects and key gaps in knowledge about embryonic VBW development that need to be addressed to further understand mechanisms of human VBW pathologies.

Combinatorial Wnt signaling landscape during brachiopod anteroposterior patterning

BACKGROUND

Wnt signaling pathways play crucial roles in animal development. They establish embryonic axes, specify cell fates, and regulate tissue morphogenesis from the early embryo to organogenesis. It is becoming increasingly recognized that these distinct developmental outcomes depend upon dynamic interactions between multiple ligands, receptors, antagonists, and other pathway modulators, consolidating the view that a combinatorial "code" controls the output of Wnt signaling. However, due to the lack of comprehensive analyses of Wnt components in several animal groups, it remains unclear if specific combinations always give rise to specific outcomes, and if these combinatorial patterns are conserved throughout evolution.

RESULTS

In this work, we investigate the combinatorial expression of Wnt signaling components during the axial patterning of the brachiopod Terebratalia transversa. We find that T. transversa has a conserved repertoire of ligands, receptors, and antagonists. These genes are expressed throughout embryogenesis but undergo significant upregulation during axial elongation. At this stage, Frizzled domains occupy broad regions across the body while Wnt domains are narrower and distributed in partially overlapping patches; antagonists are mostly restricted to the anterior end. Based on their combinatorial expression, we identify a series of unique transcriptional subregions along the anteroposterior axis that coincide with the different morphological subdivisions of the brachiopod larval body. When comparing these data across the animal phylogeny, we find that the expression of Frizzled genes is relatively conserved, whereas the expression of Wnt genes is more variable.

CONCLUSIONS

Our results suggest that the differential activation of Wnt signaling pathways may play a role in regionalizing the anteroposterior axis of brachiopod larvae. More generally, our analyses suggest that changes in the receptor context of Wnt ligands may act as a mechanism for the evolution and diversification of the metazoan body axis.

Pleiotropy in FOXC1-attributable phenotypes involves altered ciliation and cilia-dependent signaling

Alterations to cilia are responsible for a wide range of severe disease; however, understanding of the transcriptional control of ciliogenesis remains incomplete. In this study we investigated whether altered cilia-mediated signaling contributes to the pleiotropic phenotypes caused by the Forkhead transcription factor FOXC1. Here, we show that patients with FOXC1-attributable Axenfeld-Rieger Syndrome (ARS) have a prevalence of ciliopathy-associated phenotypes comparable to syndromic ciliopathies. We demonstrate that altering the level of Foxc1 protein, via shRNA mediated inhibition, CRISPR/Cas9 mutagenesis and overexpression, modifies cilia length in vitro. These structural changes were associated with substantially perturbed cilia-dependent signaling [Hedgehog (Hh) and PDGFRα], and altered ciliary compartmentalization of the Hh pathway transcription factor, Gli2. Consistent with these data, in primary cultures of murine embryonic meninges, cilia length was significantly reduced in heterozygous and homozygous Foxc1 mutants compared to controls. Meningeal expression of the core Hh signaling components Gli1, Gli3 and Sufu was dysregulated, with comparable dysregulation of Pdgfrα signaling evident from significantly altered Pdgfrα and phosphorylated Pdgfrα expression. On the basis of these clinical and experimental findings, we propose a model that altered cilia-mediated signaling contributes to some FOXC1-induced phenotypes.

Wnt7b acts in concert with Wnt5a to regulate tissue elongation and planar cell polarity via noncanonical Wnt signaling

Intercellular signaling mediated by evolutionarily conserved planar cell polarity (PCP) proteins aligns cell polarity along the tissue plane and drives polarized cell behaviors during tissue morphogenesis. Accumulating evidence indicates that the vertebrate PCP pathway is regulated by noncanonical, β-catenin-independent Wnt signaling; however, the signaling components and mechanisms are incompletely understood. In the mouse hearing organ, both PCP and noncanonical Wnt (ncWnt) signaling are required in the developing auditory sensory epithelium to control cochlear duct elongation and planar polarity of resident sensory hair cells (HCs), including the shape and orientation of the stereociliary hair bundle essential for sound detection. We have recently discovered a Wnt/G-protein/PI3K pathway that coordinates HC planar polarity and intercellular PCP signaling. Here, we identify Wnt7b as a ncWnt ligand acting in concert with Wnt5a to promote tissue elongation in diverse developmental processes. In the cochlea, Wnt5a and Wnt7b are redundantly required for cochlear duct coiling and elongation, HC planar polarity, and asymmetric localization of core PCP proteins Fzd6 and Dvl2. Mechanistically, Wnt5a/Wnt7b-mediated ncWnt signaling promotes membrane recruitment of Daple, a nonreceptor guanine nucleotide exchange factor for Gαi, and activates PI3K/AKT and ERK signaling, which promote asymmetric Fzd6 localization. Thus, ncWnt and PCP signaling pathways have distinct mutant phenotypes and signaling components, suggesting that they act as separate, parallel pathways with nonoverlapping functions in cochlear morphogenesis. NcWnt signaling drives tissue elongation and reinforces intercellular PCP signaling by regulating the trafficking of PCP-specific Frizzled receptors.

Villification of the intestinal epithelium is driven by Foxl1

The primitive gut tube of mammals initially forms as a simple cylinder consisting of the endoderm-derived, pseudostratified epithelium and the mesoderm-derived surrounding mesenchyme. During mid-gestation a dramatic transformation occurs in which the epithelium is both restructured into its final cuboidal form and simultaneously folded and refolded to create intestinal villi and intervillus regions, the incipient crypts. Here we show that the mesenchymal winged helix transcription factor Foxl1, itself induced by epithelial hedgehog signaling, controls villification by activating BMP and PDGFRa as well as planar cell polarity genes in epithelial-adjacent telocyte progenitors, both directly and in a feed- forward loop with Foxo3. In the absence of Foxl1-dependent mesenchymal signaling, villus formation is delayed, the separation of epithelial cells into mitotic intervillus and postmitotic villus cells impaired, and the differentiation of secretory progenitors blocked. Thus, Foxl1 orchestrates key events during the epithelial transition of the fetal mammalian gut.

Exploring the principles of embryonic mammary gland branching morphogenesis

Branching morphogenesis is a characteristic feature of many essential organs, such as the lung and kidney, and most glands, and is the net result of two tissue behaviors: branch point initiation and elongation. Each branched organ has a distinct architecture customized to its physiological function, but how patterning occurs in these ramified tubular structures is a fundamental problem of development. Here, we use quantitative 3D morphometrics, time-lapse imaging, manipulation of ex vivo cultured mouse embryonic organs and mice deficient in the planar cell polarity component Vangl2 to address this question in the developing mammary gland. Our results show that the embryonic epithelial trees are highly complex in topology owing to the flexible use of two distinct modes of branch point initiation: lateral branching and tip bifurcation. This non-stereotypy was contrasted by the remarkably constant average branch frequency, indicating a ductal growth invariant, yet stochastic, propensity to branch. The probability of branching was malleable and could be tuned by manipulating the Fgf10 and Tgfβ1 pathways. Finally, our in vivo data and ex vivo time-lapse imaging suggest the involvement of tissue rearrangements in mammary branch elongation.

Frizzled receptors (FZDs) in Wnt signaling: potential therapeutic targets for human cancers

Frizzled receptors (FZDs) are key contributors intrinsic to the Wnt signaling pathway, activation of FZDs triggering the Wnt signaling cascade is frequently observed in human tumors and intimately associated with an aggressive carcinoma phenotype. It has been shown that the abnormal expression of FZD receptors contributes to the manifestation of malignant characteristics in human tumors such as enhanced cell proliferation, metastasis, chemotherapy resistance as well as the acquisition of cancer stemness. Given the essential roles of FZD receptors in the Wnt signaling in human tumors, this review aims to consolidate the prevailing knowledge on the specific status of FZD receptors (FZD1-10) and elucidate their respective functions in tumor progression. Furthermore, we delineate the structural basis for binding of FZD and its co-receptors to Wnt, and provide a better theoretical foundation for subsequent studies on related mechanisms. Finally, we describe the existing biological classes of small molecule-based FZD inhibitors in detail in the hope that they can provide useful assistance for design and development of novel drug candidates targeted FZDs.

Stearoylation cycle regulates the cell surface distribution of the PCP protein Vangl2

Defects in planar cell polarity (PCP) have been implicated in diverse human pathologies. Vangl2 is one of the core PCP components crucial for PCP signaling. Dysregulation of Vangl2 has been associated with severe neural tube defects and cancers. However, how Vangl2 protein is regulated at the posttranslational level has not been well understood. Using chemical reporters of fatty acylation and biochemical validation, here we present that Vangl2 subcellular localization is regulated by a reversible S-stearoylation cycle. The dynamic process is mainly regulated by acyltransferase ZDHHC9 and deacylase acyl-protein thioesterase 1 (APT1). The stearoylation-deficient mutant of Vangl2 shows decreased plasma membrane localization, resulting in disruption of PCP establishment during cell migration. Genetically or pharmacologically inhibiting ZDHHC9 phenocopies the effects of the stearoylation loss of Vangl2. In addition, loss of Vangl2 stearoylation enhances the activation of oncogenic Yes-associated protein 1 (YAP), serine-threonine kinase AKT, and extracellular signal-regulated protein kinase (ERK) signaling and promotes breast cancer cell growth and HRas G12V mutant (HRasV12)-induced oncogenic transformation. Our results reveal a regulation mechanism of Vangl2, and provide mechanistic insight into how fatty acid metabolism and protein fatty acylation regulate PCP signaling and tumorigenesis by core PCP protein lipidation.

Emergence of cellular nematic order is a conserved feature of gastrulation in animal embryos

Cells undergo dramatic changes in morphology during embryogenesis, yet how these changes affect the formation of ordered tissues remains elusive. Here we find that the emergence of a nematic liquid crystal phase occurs in cells during gastrulation in the development of embryos of fish, frogs, and fruit flies. Moreover, the spatial correlations in all three organisms are long-ranged and follow a similar power-law decay( y ∼ x - α ) with α less than unity for the nematic order parameter, suggesting a common underlying physical mechanism unifies events in these distantly related species. All three species exhibit similar propagation of the nematic phase, reminiscent of nucleation and growth phenomena. Finally, we use a theoretical model along with disruptions of cell adhesion and cell specification to characterize the minimal features required for formation of the nematic phase. Our results provide a framework for understanding a potentially universal features of metazoan embryogenesis and shed light on the advent of ordered structures during animal development.

Emergence of cellular nematic order is a conserved feature of gastrulation in animal embryos

Cells undergo dramatic changes in morphology during embryogenesis, yet how these changes affect the formation of ordered tissues remains elusive. Here we find that the emergence of a nematic liquid crystal phase occurs in cells during gastrulation in the development of embryos of fish, frogs, and fruit flies. Moreover, the spatial correlations in all three organisms are long-ranged and follow a similar power-law decay( y ∼ x - α ) with α less than unity for the nematic order parameter, suggesting a common underlying physical mechanism unifies events in these distantly related species. All three species exhibit similar propagation of the nematic phase, reminiscent of nucleation and growth phenomena. Finally, we use a theoretical model along with disruptions of cell adhesion and cell specification to characterize the minimal features required for formation of the nematic phase. Our results provide a framework for understanding a potentially universal features of metazoan embryogenesis and shed light on the advent of ordered structures during animal development.

Collective cell dynamics and luminal fluid flow in the epididymis: A mechanobiological perspective

BACKGROUND

The mammalian epididymis is a specialized duct system that serves a critical role in sperm maturation and storage. Its distinctive, highly coiled tissue morphology provides a unique opportunity to investigate the link between form and function in reproductive biology. Although recent genetic studies have identified key genes and signaling pathways involved in the development and physiological functions of the epididymis, there has been limited discussion about the underlying dynamic and mechanical processes that govern these phenomena.

AIMS

In this review, we aim to address this gap by examining two key aspects of the epididymis across its developmental and physiological phases.

RESULTS AND DISCUSSION

First, we discuss how the complex morphology of the Wolffian/epididymal duct emerges through collective cell dynamics, including duct elongation, cell proliferation, and arrangement during embryonic development. Second, we highlight dynamic aspects of luminal fluid flow in the epididymis, essential for regulating the microenvironment for sperm maturation and motility, and discuss how this phenomenon emerges and interplays with epididymal epithelial cells.

CONCLUSION

This review not only aims to summarize current knowledge but also to provide a starting point for further exploration of mechanobiological aspects related to the cellular and extracellular fluid dynamics in the epididymis.

A CUC1/auxin genetic module links cell polarity to patterned tissue growth and leaf shape diversity in crucifer plants

How tissue-level information encoded by fields of regulatory gene activity is translated into the patterns of cell polarity and growth that generate the diverse shapes of different species remains poorly understood. Here, we investigate this problem in the case of leaf shape differences between Arabidopsis thaliana, which has simple leaves, and its relative Cardamine hirsuta that has complex leaves divided into leaflets. We show that patterned expression of the transcription factor CUP-SHAPED COTYLEDON1 in C. hirsuta (ChCUC1) is a key determinant of leaf shape differences between the two species. Through inducible genetic perturbations, time-lapse imaging of growth, and computational modeling, we find that ChCUC1 provides instructive input into auxin-based leaf margin patterning. This input arises via transcriptional regulation of multiple auxin homeostasis components, including direct activation of WAG kinases that are known to regulate the polarity of PIN-FORMED auxin transporters. Thus, we have uncovered a mechanism that bridges biological scales by linking spatially distributed and species-specific transcription factor expression to cell-level polarity and growth, to shape diverse leaf forms.

Hierarchical global and local auxin signals coordinate cellular interdigitation in Arabidopsis

The development of multicellular tissues requires both local and global coordination of cell polarization, however, the mechanisms underlying their interplay are poorly understood. In Arabidopsis, leaf epidermal pavement cells (PC) develop a puzzle-piece shape locally coordinated through apoplastic auxin signaling. Here we show auxin also globally coordinates interdigitation by activating the TIR1/AFB-dependent nuclear signaling pathway. This pathway promotes a transient maximum of auxin at the cotyledon tip, which then moves across the leaf activating local PC polarization, as demonstrated by locally uncaged auxin globally rescuing defects in tir1;afb1;afb2;afb4;afb5 mutant but not in tmk1;tmk2;tmk3;tmk4 mutants. Our findings show that hierarchically integrated global and local auxin signaling systems, which respectively depend on TIR1/AFB-dependent gene transcription in the nucleus and TMK-mediated rapid activation of ROP GTPases at the cell surface, control PC interdigitation patterns in Arabidopsis cotyledons, revealing a mechanism for coordinating a local cellular process with the development of whole tissues.

MPP7 mediates EMT via Wnt/β-catenin pathway to promote polarity changes in epithelial ovarian cancer cells

Ovarian cancer is one of the gynecological malignancies with the highest mortality rate. Its widespread metastasis is difficult to cure, and the beneficiaries of targeted therapy are still limited, which has been a long-standing bottleneck problem. MAGUK P55 scaffold protein 7 (MPP7) plays an important role in the establishment of epithelial cell polarity, but its potential significance in epithelial ovarian cancer is still unclear. In this study, we investigated the expression profile of MPP7 and its functional role in epithelial ovarian cancer. Through analysis of TCGA and GEO databases, combined with immunohistochemical staining of ovarian tumor tissue chips, it was found that MPP7 is significantly overexpressed in epithelial ovarian cancer tissue, and its high expression is closely related to poor prognosis of patients. It has been verified through cell function experiments that interference with MPP7 can inhibit the proliferation, migration, and invasion of ovarian cancer cells in vitro. Performing planar polarity immunofluorescence staining on ovarian cancer cells revealed that interference with MPP7 can cause polarity changes in ovarian cancer cells. The transcriptome sequencing results of the ovarian cancer database were analyzed, and Western Blot was used to verify that MPP7 may mediate EMT via Wnt/β-catenin signaling pathway and promote changes in cell polarity in human epithelial ovarian cancer, thereby promoting cancer progression, demonstrating the potential of MPP7 as a new biomarker and target for the diagnosis and treatment of ovarian cancer.

Mesenchymal Wnts are required for morphogenetic movements of calvarial osteoblasts during apical expansion

Apical expansion of calvarial osteoblast progenitors from the cranial mesenchyme (CM) above the eye is integral to calvarial growth and enclosure of the brain. The cellular behaviors and signals underlying the morphogenetic process of calvarial expansion are unknown. Time-lapse light-sheet imaging of mouse embryos revealed calvarial progenitors intercalate in 3D in the CM above the eye, and exhibit protrusive and crawling activity more apically. CM cells express non-canonical Wnt/planar cell polarity (PCP) core components and calvarial osteoblasts are bidirectionally polarized. We found non-canonical ligand Wnt5a-/- mutants have less dynamic cell rearrangements and protrusive activity. Loss of CM-restricted Wntless (CM-Wls), a gene required for secretion of all Wnt ligands, led to diminished apical expansion of Osx+ calvarial osteoblasts in the frontal bone primordia in a non-cell autonomous manner without perturbing proliferation or survival. Calvarial osteoblast polarization, progressive cell elongation and enrichment for actin along the baso-apical axis were dependent on CM-Wnts. Thus, CM-Wnts regulate cellular behaviors during calvarial morphogenesis for efficient apical expansion of calvarial osteoblasts. These findings also offer potential insights into the etiologies of calvarial dysplasias.

Wnt-Ror-Dvl signalling and the dystrophin complex organize planar-polarized membrane compartments in C. elegans muscles

Cell polarity mechanisms allow the formation of specialized membrane domains with unique protein compositions, signalling properties, and functional characteristics. By analyzing the localization of potassium channels and proteins belonging to the dystrophin-associated protein complex, we reveal the existence of distinct planar-polarized membrane compartments at the surface of C. elegans muscle cells. We find that muscle polarity is controlled by a non-canonical Wnt signalling cascade involving the ligand EGL-20/Wnt, the receptor CAM-1/Ror, and the intracellular effector DSH-1/Dishevelled. Interestingly, classical planar cell polarity proteins are not required for this process. Using time-resolved protein degradation, we demonstrate that -while it is essentially in place by the end of embryogenesis- muscle polarity is a dynamic state, requiring continued presence of DSH-1 throughout post-embryonic life. Our results reveal the unsuspected complexity of the C. elegans muscle membrane and establish a genetically tractable model system to study cellular polarity and membrane compartmentalization in vivo.

Rac1 and Nectin3 are essential for PCP-directed axon guidance in the peripheral auditory system

Our sense of hearing is critically dependent on the spiral ganglion neurons (SGNs) that connect the sound receptors in the organ of Corti (OC) to the cochlear nuclei of the hindbrain. Type I SGNs innervate inner hair cells (IHCs) to transmit sound signals, while type II SGNs (SGNIIs) innervate outer hair cells (OHCs) to detect moderate-to-intense sound. During development, SGNII afferents make a characteristic 90-degree turn toward the base of the cochlea and innervate multiple OHCs. It has been shown that the Planar Cell Polarity (PCP) pathway acts non-autonomously to mediate environmental cues in the cochlear epithelium for SGNII afferent turning towards the base. However, the underlying mechanisms are unknown. Here, we present evidence that PCP signaling regulates multiple downstream effectors to influence cell adhesion and the cytoskeleton in cochlear supporting cells (SCs), which serve as intermediate targets of SGNII afferents. We show that the core PCP gene Vangl2 regulates the localization of the small GTPase Rac1 and the cell adhesion molecule Nectin3 at SC-SC junctions through which SGNII afferents travel. Through in vivo genetic analysis, we also show that loss of Rac1 or Nectin3 partially phenocopied SGNII peripheral afferent turning defects in Vangl2 mutants, and that Rac1 plays a non-autonomous role in this process in part by regulating PCP protein localization at the SC-SC junctions. Additionally, epistasis analysis indicates that Nectin3 and Rac1 likely act in the same genetic pathway to control SGNII afferent turning. Together, these experiments identify Nectin3 and Rac1 as novel regulators of PCP-directed SGNII axon guidance in the cochlea.

Hyperexpression of tumor necrosis factor receptor 2 inhibits differentiation of myeloid-derived suppressor cells by instigating apolarity during ageing

During the ageing process, TNF-α can promote the expansion of myeloid-derived suppressor cells (MDSCs). However, it remains unclear which receptor(s) of TNF-α are involved in and how they modulate this process. Here, we report that TNFR2 hyperexpression induced by either TNF-α or IL-6, two proinflammatory factors of senescence-associated secretory phenotype (SASP), causes cellular apolarity and differentiation inhibition in aged MDSCs. Ex vivo overexpression of TNFR2 in young MDSCs inhibited their polarity and differentiation, whereas in vivo depletion of Tnfr2 in aged MDSCs promotes their differentiation. Consequently, the age-dependent increase of TNFR2 versus unaltered TNFR1 expression in aged MDSCs significantly shifts the balance of TNF-α signaling toward the TNFR2-JNK axis, which accounts for JNK-induced impairment of cell polarity and differentiation failure of aged MDSCs. Consistently, inhibiting JNK attenuates apolarity and partially restores the differentiation capacity of aged MDSCs, suggesting that upregulated TNFR2/JNK signaling is a key factor limiting MDSC differentiation during organismal ageing. Therefore, abnormal hyperexpression of TNFR2 represents a general mechanism by which extrinsic SASP signals disrupt intrinsic cell polarity behavior, thereby arresting mature differentiation of MDSCs with ageing, suggesting that TNFR2 could be a potential therapeutic target for intervention of ageing through rejuvenation of aged MDSCs.

Recent insights into the therapeutic strategies targeting the pseudokinase PTK7 in cancer

The generation of drugs counteracting deregulated protein kinases has been a major focus in cancer therapy development. Breakthroughs in this effort have produced many therapeutic agents to the benefit of patients, mostly through the development of chemical or antibody-based drugs targeting active kinases. These strategies are challenged when considering catalytically inactive protein kinases (or pseudokinases), which represent 10% of the human kinome with many of relevance in cancer. Among the so-called pseudotyrosine kinases, the PTK7 receptor tyrosine kinase (RTK) stands as a bona fide target overexpressed in several solid tumors and hematological malignancies and linked to metastasis, poor prognosis, and resistance to treatment. Despite the lack of catalytic activity, PTK7 has signaling capacities through heterodimerization with active RTKs and offers pharmacological targeting opportunities through its inactive kinase domain. Moreover, PTK7-targeting strategies based on antibody-drug conjugates, aptamers, and CAR-T cell-based therapies have demonstrated encouraging results in preclinical and clinical settings. We review the most recent data assigning to PTK7 a prominent role in cancer progression as well as current preclinical and clinical targeting strategies against RTK family pseudokinases including PTK7.

Vangl-dependent mesenchymal thinning shapes the distal lung during murine sacculation

The planar cell polarity (PCP) complex is speculated to function in murine lung development, where branching morphogenesis generates an epithelial tree whose distal tips expand dramatically during sacculation. Here, we show that PCP is dispensable in the airway epithelium for sacculation. Rather, we find a Celsr1-independent role for the PCP component Vangl in the pulmonary mesenchyme: loss of Vangl1/2 inhibits mesenchymal thinning and expansion of the saccular epithelium. Further, loss of mesenchymal Wnt5a mimics sacculation defects observed in Vangl2-mutant lungs, implicating mesenchymal Wnt5a/Vangl signaling as a key regulator of late lung morphogenesis. A computational model predicts that sacculation requires a fluid mesenchymal compartment. Lineage-tracing and cell-shape analyses are consistent with the mesenchyme acting as a fluid tissue, suggesting that loss of Vangl1/2 impacts the ability of mesenchymal cells to exchange neighbors. Our data thus identify an explicit function for Vangl and the pulmonary mesenchyme in actively shaping the saccular epithelium.

The Geometric Basis of Epithelial Convergent Extension

Shape changes of epithelia during animal development, such as convergent extension, are achieved through concerted mechanical activity of individual cells. While much is known about the corresponding large scale tissue flow and its genetic drivers, fundamental questions regarding local control of contractile activity on cellular scale and its embryo-scale coordination remain open. To address these questions, we develop a quantitative, model-based analysis framework to relate cell geometry to local tension in recently obtained timelapse imaging data of gastrulating Drosophila embryos. This analysis provides a systematic decomposition of cell shape changes and T1-rearrangements into internally driven, active, and externally driven, passive, contributions. Our analysis provides evidence that germ band extension is driven by active T1 processes that self-organize through positive feedback acting on tensions. More generally, our findings suggest that epithelial convergent extension results from controlled transformation of internal force balance geometry which combines the effects of bottom-up local self-organization with the top-down, embryo-scale regulation by gene expression.

The evolving roles of Wnt signaling in stem cell proliferation and differentiation, the development of human diseases, and therapeutic opportunities

The evolutionarily conserved Wnt signaling pathway plays a central role in development and adult tissue homeostasis across species. Wnt proteins are secreted, lipid-modified signaling molecules that activate the canonical (β-catenin dependent) and non-canonical (β-catenin independent) Wnt signaling pathways. Cellular behaviors such as proliferation, differentiation, maturation, and proper body-axis specification are carried out by the canonical pathway, which is the best characterized of the known Wnt signaling paths. Wnt signaling has emerged as an important factor in stem cell biology and is known to affect the self-renewal of stem cells in various tissues. This includes but is not limited to embryonic, hematopoietic, mesenchymal, gut, neural, and epidermal stem cells. Wnt signaling has also been implicated in tumor cells that exhibit stem cell-like properties. Wnt signaling is crucial for bone formation and presents a potential target for the development of therapeutics for bone disorders. Not surprisingly, aberrant Wnt signaling is also associated with a wide variety of diseases, including cancer. Mutations of Wnt pathway members in cancer can lead to unchecked cell proliferation, epithelial-mesenchymal transition, and metastasis. Altogether, advances in the understanding of dysregulated Wnt signaling in disease have paved the way for the development of novel therapeutics that target components of the Wnt pathway. Beginning with a brief overview of the mechanisms of canonical and non-canonical Wnt, this review aims to summarize the current knowledge of Wnt signaling in stem cells, aberrations to the Wnt pathway associated with diseases, and novel therapeutics targeting the Wnt pathway in preclinical and clinical studies.

Research Progress on the Mechanism of the SFRP-Mediated Wnt Signalling Pathway Involved in Bone Metabolism in Osteoporosis

Osteoporosis (OP) is a metabolic bone disease linked to an elevated fracture risk, primarily stemming from disruptions in bone metabolism. Present clinical treatments for OP merely alleviate symptoms. Hence, there exists a pressing need to identify novel targets for the clinical treatment of OP. Research indicates that the Wnt signalling pathway is modulated by serum-secreted frizzled-related protein 5 (SFRP5), potentially serving as a pivotal regulator in bone metabolism disorders. Moreover, studies confirm elevated SFRP5 expression in OP, with SFRP5 overexpression leading to the downregulation of Wnt and β-catenin proteins in the Wnt signalling pathway, as well as the expression of osteogenesis-related marker molecules such as RUNX2, ALP, and OPN. Conversely, the opposite has been reported when SFRP5 is knocked out, suggesting that SFRP5 may be a key factor involved in the regulation of bone metabolism via the Wnt signalling axis. However, the molecular mechanisms underlying the action of SFRP5-induced OP have yet to be comprehensively elucidated. This review focusses on the molecular structure and function of SFRP5 and the potential molecular mechanisms of the SFRP5-mediated Wnt signalling pathway involved in bone metabolism in OP, providing reasonable evidence for the targeted therapy of SFRP5 for the prevention and treatment of OP.

PDZome-wide and structural characterization of the PDZ-binding motif of VANGL2

VANGL2 is a core component of the non-canonical Wnt/Planar Cell Polarity signaling pathway that uses its highly conserved carboxy-terminal type 1 PDZ-binding motif (PBM) to bind a variety of PDZ proteins. In this study, we characterize and quantitatively assess the largest VANGL2 PDZome-binding profile documented so far, using orthogonal methods. The results of our holdup approach support VANGL2 interactions with a large panel of both long-recognized and unprecedented PDZ domains. Truncation and point mutation analyses of the VANGL2 PBM establish that, beyond the strict requirement of the P-0 / V521 and P-2 / T519 amino acids, upstream residues, including E518, Q516 and R514 at, respectively, P-3, P-5 and P-7 further contribute to the robustness of VANGL2 interactions with two distinct PDZ domains, SNX27 and SCRIBBLE-PDZ3. In agreement with these data, incremental amino-terminal deletions of the VANGL2 PBM causes its overall affinity to progressively decline. Moreover, the holdup data establish that the PDZome binding repertoire of VANGL2 starts to diverge significantly with the truncation of E518. A structural analysis of the SYNJ2BP-PDZ/VANGL2 interaction with truncated PBMs identifies a major conformational change in the binding direction of the PBM peptide after the P-2 position. Finally, we report that the PDZome binding profile of VANGL2 is dramatically rearranged upon phosphorylation of S517, T519 and S520. Our crystallographic approach illustrates how SYNJ2BP accommodates a S520-phosphorylated PBM peptide through the ideal positioning of two basic residues, K48 and R86. Altogether our data provides a comprehensive view of the VANGL2 PDZ network and how this network specifically responds to the post-translation modification of distinct PBM residues. These findings should prove useful in guiding future functional and molecular studies of the key PCP component VANGL2.

The role of prickle proteins in vertebrate development and pathology

Prickle is an evolutionarily conserved family of proteins exclusively associated with planar cell polarity (PCP) signalling. This signalling pathway provides directional and positional cues to eukaryotic cells along the plane of an epithelial sheet, orthogonal to both apicobasal and left-right axes. Through studies in the fruit fly Drosophila, we have learned that PCP signalling is manifested by the spatial segregation of two protein complexes, namely Prickle/Vangl and Frizzled/Dishevelled. While Vangl, Frizzled, and Dishevelled proteins have been extensively studied, Prickle has been largely neglected. This is likely because its role in vertebrate development and pathologies is still being explored and is not yet fully understood. The current review aims to address this gap by summarizing our current knowledge on vertebrate Prickle proteins and to cover their broad versatility. Accumulating evidence suggests that Prickle is involved in many developmental events, contributes to homeostasis, and can cause diseases when its expression and signalling properties are deregulated. This review highlights the importance of Prickle in vertebrate development, discusses the implications of Prickle-dependent signalling in pathology, and points out the blind spots or potential links regarding Prickle, which could be studied further.