scholarly journals Deficient FGF signaling in the developing peripheral retina disrupts ciliary margin development and causes aniridia

2018 ◽  
Author(s):  
Revathi Balasubramanian ◽  
Chenqi Tao ◽  
Karina Polanco ◽  
Jian Zhong ◽  
Fen Wang ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Critical Role ◽  
Peripheral Retina ◽  
Fgf Signaling ◽  
Surface Ectoderm ◽  
Genetic Ablation ◽  
Central Retina ◽  
Ciliary Margin ◽  
Wnt Ligands

ABSTRACTThe mammalian ciliary margin is a part of the developing peripheral neural retina that differentiates into the ciliary body and the iris. Canonical WNT signaling plays a critical role in the specification of the ciliary margin at the peripheral retina in the presence of strong FGF signaling in the central retina. The mechanism of how the boundary between the central retina and the ciliary margin is created has not been previously elucidated. Using genetic ablation and epistasis experiments, we show that loss of FGF signaling gradient in the peripheral retina causes expansion of WNT signaling towards the central retina thereby disrupting the neurogenic boundary and compartmentalization of the ciliary margin. Loss of WNT signaling displays a complimentary effect with expansion of FGF signaling into the ciliary marginal space. Using in vivo experiments, we elucidate the FGF signaling cascade involved in development of the ciliary margin. We also identify the surface ectoderm as the source of WNT ligands in eliciting WNT response at the ciliary margin. We show that an interaction between FGF and WNT signaling is required for generation of the ciliary marginal cells. Taken together, our results reveal that a gradient intersection of FGF and WNT signaling is required for specification of the ciliary margin.

scholarly journals An Essential Role of the Cysteine-rich Domain of FZD4 in Norrin/Wnt Signaling and Familial Exudative Vitreoretinopathy

2010 ◽  
Vol 286 (12) ◽  
pp. 10210-10215 ◽  
Author(s):  
Kang Zhang ◽  
Yuko Harada ◽  
Xinran Wei ◽  
Dhananjay Shukla ◽  
Anand Rajendran ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Wnt Pathway ◽  
Critical Role ◽  
Luciferase Reporter ◽  
Peripheral Retina ◽  
Familial Exudative Vitreoretinopathy ◽  
Rich Domain ◽  
Cysteine Rich Domain

The Wnt pathway plays important yet diverse roles in health and disease. Mutations in the Wnt receptor FZD4 gene have been confirmed to cause familial exudative vitreoretinopathy (FEVR). FEVR is characterized by incomplete vascularization of the peripheral retina, which can lead to vitreous bleeding, tractional retinal detachment, and blindness. We screened for mutations in the FZD4 gene in five families with FEVR and identified five mutations (C45Y, Y58C, W226X, C204R, and W496X), including three novel mutations (C45Y, Y58C, and W226X). In the retina, Norrin serves as a ligand and binds to FZD4 to activate the Wnt signaling pathway in normal angiogenesis and vascularization. The cysteine-rich domain (CRD) of FZD4 has been shown to play a critical role in Norrin-FZD4 binding. We investigated the effect of mutations in the FZD4 CRD in Norrin binding and signaling in vitro and in vivo. Wild-type and mutant FZD4 proteins were assayed for Norrin binding and Norrin-dependent activation of the canonical Wnt pathway by cell-surface and overlay binding assays and luciferase reporter assays. In HEK293 transfection studies, C45Y, Y58C, and C204R mutants did not bind to Norrin and failed to transduce FZD4-mediated Wnt/β-catenin signaling. In vivo studies using Xenopus embryos showed that these FZD4 mutations disrupt Norrin/β-catenin signaling as evidenced by decreased Siamois and Xnr3 expression. This study identified a new class of FZD4 gene mutations in human disease and demonstrates a critical role of the CRD in Norrin binding and activation of the β-catenin pathway.

scholarly journals Phase transition specified by a binary code patterns the vertebrate eye cup

2021 ◽  
Author(s):  
Revathi Balasubramanian ◽  
Xuanyu Min ◽  
Peter M.J. Quinn ◽  
Quentin Lo Giudice ◽  
Chenqi Tao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Wnt Signaling ◽  
Single Cell Analysis ◽  
Fgf Signaling ◽  
Independent Manner ◽  
Ciliary Margin ◽  
Evolutionarily Conserved ◽  
Human Ips Cells ◽  
Vertebrate Eye

The developing vertebrate eye cup is partitioned into the neural retina (NR), the retinal pigmented epithelium (RPE) and the ciliary margin (CM). By single cell analysis, we showed that a gradient of FGF signaling regulates demarcation and subdivision of the CM and controls its stem cell-like property of self-renewal, differentiation and survival. This regulation by FGF is balanced by an evolutionarily conserved Wnt signaling gradient induced by the lens ectoderm and the periocular mesenchyme, which specifies the CM and the distal RPE. These two morphogen gradients converge in the CM where FGF signaling promotes Wnt signaling by stabilizing β-catenin in a GSK3β-independent manner. We further showed that activation of Wnt signaling converts the NR to either the CM or the RPE depending on the level of FGF signaling. Conversely, activation of FGF transforms the RPE to the NR or CM dependent on Wnt activity. We demonstrated that the default fate of the eye cup is the NR, but synergistic FGF and Wnt signaling promotes CM formation both in vivo and in retinal organoid culture of human iPS cells. Our study reveals that the vertebrate eye develops through phase transition determined by a combinatorial code of FGF and Wnt signaling.

scholarly journals Increasing Wnt signaling in the bone marrow microenvironment inhibits the development of myeloma bone disease and reduces tumor burden in bone in vivo

Blood ◽  
2008 ◽  
Vol 111 (5) ◽  
pp. 2833-2842 ◽  
Author(s):  
Claire M. Edwards ◽  
James R. Edwards ◽  
Seint T. Lwin ◽  
Javier Esparza ◽  
Babatunde O. Oyajobi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Tumor Growth ◽  
Wnt Signaling ◽  
Bone Disease ◽  
Critical Role ◽  
Tumor Burden ◽  
Bone Marrow Microenvironment ◽  
Myeloma Bone Disease ◽  
Osteolytic Bone Disease

There is increasing evidence to suggest that the Wnt signaling pathway plays a critical role in the pathogenesis of myeloma bone disease. In the present study, we determined whether increasing Wnt signaling within the bone marrow microenvironment in myeloma counteracts development of osteolytic bone disease. C57BL/KaLwRij mice were inoculated intravenously with murine 5TGM1 myeloma cells, resulting in tumor growth in bone and development of myeloma bone disease. Lithium chloride (LiCl) treatment activated Wnt signaling in osteoblasts, inhibited myeloma bone disease, and decreased tumor burden in bone, but increased tumor growth when 5TGM1 cells were inoculated subcutaneously. Abrogation of β-catenin activity and disruption of Wnt signaling in 5TGM1 cells by stable overexpression of a dominant-negative TCF4 prevented the LiCl-induced increase in subcutaneous growth but had no effect on LiCl-induced reduction in tumor burden within bone or on osteolysis in myeloma-bearing mice. Together, these data highlight the importance of the local microenvironment in the effect of Wnt signaling on the development of myeloma bone disease and demonstrate that, despite a direct effect to increase tumor growth at extraosseous sites, increasing Wnt signaling in the bone marrow microenvironment can prevent the development of myeloma bone disease and inhibit myeloma growth within bone in vivo.

scholarly journals Neddylation is critical to cortical development by regulating Wnt/β-catenin signaling

2020 ◽  
Vol 117 (42) ◽  
pp. 26448-26459 ◽  
Author(s):  
Lei Zhang ◽  
Hongyang Jing ◽  
Haiwen Li ◽  
Wenbing Chen ◽  
Bin Luo ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Protein Modification ◽  
Radial Glia ◽  
Critical Role ◽  
Cortical Development ◽  
Nuclear Accumulation ◽  
Progressive Reduction ◽  
Intermediate Progenitors

Wnt signaling plays a critical role in production and differentiation of neurons and undergoes a progressive reduction during cortical development. However, how Wnt signaling is regulated is not well understood. Here we provide evidence for an indispensable role of neddylation, a ubiquitylation-like protein modification, in inhibiting Wnt/β-catenin signaling. We show that β-catenin is neddylated; and inhibiting β-catenin neddylation increases its nuclear accumulation and Wnt/β-catenin signaling. To test this hypothesis in vivo, we mutated Nae1, an obligative subunit of the E1 for neddylation in cortical progenitors. The mutation leads to eventual reduction in radial glia progenitors (RGPs). Consequently, the production of intermediate progenitors (IPs) and neurons is reduced, and neuron migration is impaired, resulting in disorganization of the cerebral cortex. These phenotypes are similar to those of β-catenin gain-of-function mice. Finally, suppressing β-catenin expression is able to rescue deficits of Nae1 mutant mice. Together, these observations identified a mechanism to regulate Wnt/β-catenin signaling in cortical development.

scholarly journals The Protein Dendrite Arborization and Synapse Maturation 1 (Dasm-1) Is Dispensable for Dendrite Arborization

2008 ◽  
Vol 28 (8) ◽  
pp. 2782-2791 ◽  
Author(s):  
Archana Mishra ◽  
Boris Knerr ◽  
Sónia Paixão ◽  
Edgar R. Kramer ◽  
Rüdiger Klein
Keyword(s):  
Hippocampal Neurons ◽  
Critical Role ◽  
Dendritic Tree ◽  
Dendrite Growth ◽  
Immunoglobulin Superfamily ◽  
Genetic Ablation ◽  
Neuronal Connections ◽  
Synapse Maturation

ABSTRACT The development of a highly branched dendritic tree is essential for the establishment of functional neuronal connections. The evolutionarily conserved immunoglobulin superfamily member, the protein dendrite arborization and synapse maturation 1 (Dasm-1) is thought to play a critical role in dendrite formation of dissociated hippocampal neurons. RNA interference-mediated Dasm-1 knockdown was previously shown to impair dendrite, but not axonal, outgrowth and branching (S. H. Shi, D. N. Cox, D. Wang, L. Y. Jan, and Y. N. Jan, Proc. Natl. Acad. Sci. USA 101:13341-13345, 2004). Here, we report the generation and analysis of Dasm-1 null mice. We find that genetic ablation of Dasm-1 does not interfere with hippocampal dendrite growth and branching in vitro and in vivo. Moreover, the absence of Dasm-1 does not affect the modulation of dendritic outgrowth induced by brain-derived neurotrophic factor. Importantly, the previously observed impairment in dendrite growth after Dasm-1 knockdown is also observed when the Dasm-1 knockdown is performed in cultured hippocampal neurons from Dasm-1 null mice. These findings indicate that the dendrite arborization phenotype was caused by off-target effects and that Dasm-1 is dispensable for hippocampal dendrite arborization.

scholarly journals Wnt-Frizzled Signaling Regulates Activity-Mediated Synapse Formation

2021 ◽  
Vol 14 ◽  
Author(s):  
Samuel Teo ◽  
Patricia C. Salinas
Keyword(s):  
Wnt Signaling ◽  
Neuronal Activity ◽  
Molecular Mechanisms ◽  
Synapse Formation ◽  
Model Systems ◽  
Mammalian Brain ◽  
Excitatory Synapses ◽  
Wnt Ligands

The formation of synapses is a tightly regulated process that requires the coordinated assembly of the presynaptic and postsynaptic sides. Defects in synaptogenesis during development or in the adult can lead to neurodevelopmental disorders, neurological disorders, and neurodegenerative diseases. In order to develop therapeutic approaches for these neurological conditions, we must first understand the molecular mechanisms that regulate synapse formation. The Wnt family of secreted glycoproteins are key regulators of synapse formation in different model systems from invertebrates to mammals. In this review, we will discuss the role of Wnt signaling in the formation of excitatory synapses in the mammalian brain by focusing on Wnt7a and Wnt5a, two Wnt ligands that play an in vivo role in this process. We will also discuss how changes in neuronal activity modulate the expression and/or release of Wnts, resulting in changes in the localization of surface levels of Frizzled, key Wnt receptors, at the synapse. Thus, changes in neuronal activity influence the magnitude of Wnt signaling, which in turn contributes to activity-mediated synapse formation.

Tph2 Genetic Ablation Contributes to Senile Plaque Load and Astrogliosis in APP/PS1 Mice

2019 ◽  
Vol 16 (3) ◽  
pp. 219-232 ◽  
Author(s):  
Chao-Jin Xu ◽  
Jun-Ling Wang ◽  
Jing-Pan ◽  
Min-Liao
Keyword(s):  
Congo Red ◽  
Tryptophan Hydroxylase ◽  
Senile Plaque ◽  
Senile Plaques ◽  
Critical Role ◽  
Amyloid Β ◽  
Conditional Knockout ◽  
Genetic Ablation ◽  
Congo Red Staining

Background: Amyloid-β (Aβ) accumulation plays a critical role in the pathogenesis of Alzheimer’s disease (AD) lesions. Deficiency of Serotonin signaling recently has been linked to the increased Aβ level in transgenic mice and humans. In addition, tryptophan hydroxylase-2 (Tph2), a second tryptophan hydroxylase isoform, controls brain serotonin synthesis. However, it remains to be determined that whether Tph2 deficient APP/PS1mice affect the formation of Aβ plaques in vivo. Methods: Both quantitative and qualitative immunochemistry methods, as well as Congo red staining were used to evaluate the Aβ load and astrogliosis in these animals. Results: we studied alterations of cortex and hippocampus in astrocytes and senile plaques by Tph2 conditional knockout (Tph2 CKO) AD mice from 6-10 months of age. Using Congo red staining and immunostained with Aβ antibody, we showed that plaques load or plaques numbers significantly increased in Tph2 CKO experimental groups at 8 to 10 months old, compared to wild type (WT) group, respectively. Using GFAP+ astrocytes immunofluorescence method, we found that the density of GFAP+ astrocytes markedly enhanced in Tph2 CKO at 10 months. We showed Aβ plaques co-localized autophagic markers LC3 and p62. Nevertheless, we did not observe any co-localization between GFAP+ astrocytes and autophagic markers, but detected the co-localization between βIII-tubulin+ neurons and autophagic markers. Conclusion: Overall, our work provides the preliminary evidence in vivo that Tph2 plays a role in amyloid plaques generation.

scholarly journals R-Spondin Family Members Regulate the Wnt Pathway by a Common Mechanism

2008 ◽  
Vol 19 (6) ◽  
pp. 2588-2596 ◽  
Author(s):  
Kyung-Ah Kim ◽  
Marie Wagle ◽  
Karolyn Tran ◽  
Xiaoming Zhan ◽  
Melissa A. Dixon ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Wnt Pathway ◽  
Expression Patterns ◽  
Family Members ◽  
Wnt Signaling Pathway ◽  
Direct Consequence ◽  
Common Mechanism ◽  
Wnt Ligands ◽  
Canonical Wnt

The R-Spondin (RSpo) family of secreted proteins is implicated in the activation of the Wnt signaling pathway. Despite the high structural homology between the four members, expression patterns and phenotypes in knockout mice have demonstrated striking differences. Here we dissected and compared the molecular and cellular function of all RSpo family members. Although all four RSpo proteins activate the canonical Wnt pathway, RSpo2 and 3 are more potent than RSpo1, whereas RSpo4 is relatively inactive. All RSpo members require Wnt ligands and LRP6 for activity and amplify signaling of Wnt3A, Wnt1, and Wnt7A, suggesting that RSpo proteins are general regulators of canonical Wnt signaling. Like RSpo1, RSpo2-4 antagonize DKK1 activity by interfering with DKK1 mediated LRP6 and Kremen association. Analysis of RSpo deletion mutants indicates that the cysteine-rich furin domains are sufficient and essential for the amplification of Wnt signaling and inhibition of DKK1, suggesting that Wnt amplification by RSpo proteins may be a direct consequence of DKK1 inhibition. Together, these findings indicate that RSpo proteins modulate the Wnt pathway by a common mechanism and suggest that coexpression with specific Wnt ligands and DKK1 may determine their biological specificity in vivo.

scholarly journals Hypoxic mitophagy regulates mitochondrial quality and platelet activation and determines severity of I/R heart injury

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Weilin Zhang ◽  
He Ren ◽  
Chunling Xu ◽  
Chongzhuo Zhu ◽  
Hao Wu ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Ischemia Reperfusion ◽  
Critical Role ◽  
Acute Ischemia ◽  
Dependent Manner ◽  
Genetic Ablation ◽  
A Cell ◽  
Novel Strategy

Mitochondrial dysfunction underlies many prevalent diseases including heart disease arising from acute ischemia/reperfusion (I/R) injury. Here, we demonstrate that mitophagy, which selectively removes damaged or unwanted mitochondria, regulated mitochondrial quality and quantity in vivo. Hypoxia induced extensive mitochondrial degradation in a FUNDC1-dependent manner in platelets, and this was blocked by in vivo administration of a cell-penetrating peptide encompassing the LIR motif of FUNDC1 only in wild-type mice. Genetic ablation of Fundc1 impaired mitochondrial quality and increased mitochondrial mass in platelets and rendered the platelets insensitive to hypoxia and the peptide. Moreover, hypoxic mitophagy in platelets protected the heart from worsening of I/R injury. This represents a new mechanism of the hypoxic preconditioning effect which reduces I/R injury. Our results demonstrate a critical role of mitophagy in mitochondrial quality control and platelet activation, and suggest that manipulation of mitophagy by hypoxia or pharmacological approaches may be a novel strategy for cardioprotection.

Epidermal growth factor-like repeats of SCUBE1 derived from platelets are critical for thrombus formation

2019 ◽  
Vol 116 (1) ◽  
pp. 193-201
Author(s):  
Wei-Ju Liao ◽  
Meng-Ying Wu ◽  
Chen-Chung Peng ◽  
Yi-Chung Tung ◽  
Ruey-Bing Yang
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Arterial Thrombosis ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Critical Role ◽  
Adenosine Diphosphate ◽  
Genetic Ablation ◽  
Epidermal Growth

Abstract Aims SCUBE1 [signal peptide-CUB-epidermal growth factor (EGF) domain-containing protein 1], expressed in endothelial cells (ECs) and platelets, exists in soluble or membrane forms. We previously showed that soluble SCUBE1 is a biomarker for platelet activation and also an active participant of thrombosis. However, whether the adhesive module of its EGF-like repeats is essential and the specific contribution of SCUBE1 synthesized in ECs or platelets to thrombosis in vivo remain unclear. Methods and results We generated new mutant (Δ2) mice lacking the entire EGF-like repeats to evaluate the module’s functional importance during thrombogenesis in vivo. The Δ2 platelet-rich plasma showed markedly impaired platelet aggregation induced by agonists including adenosine diphosphate, collagen, the thrombin agonist PAR-4 peptide and the thromboxane A2 analogue U46619. Consistently, genetic ablation of the EGF-like repeats diminished arterial thrombosis and protected Δ2 mice against lethal thromboembolism. On flow chamber assay, whole blood isolated from Δ2 or wild-type (WT) mice pre-treated with blocking antibodies against the EGF-like repeats showed a significant decrease in platelet deposition and thrombus formation on collagen-coated surfaces under arterial shear rates. Moreover, we created animals expressing SCUBE1 only in ECs (S1-EC) or platelets (S1-PLT) by reciprocal bone-marrow transplantation between WT and Δ2 mice. The time of carotid arterial thrombosis induced by ferric chloride was normal in S1-PLT chimeric mice but much prolonged in S1-EC animals. Conclusions We demonstrate that platelet-derived SCUBE1 plays a critical role in arterial thrombosis via its adhesive EGF-like repeats in vivo and suggest targeting these adhesive motifs of SCUBE1 for potential anti-thrombotic strategy.

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