scholarly journals Spatial and temporal expression of PORCN is highly dynamic in the developing mouse cochlea.

2021 ◽  
Author(s):  
Brianna L Oliver ◽  
Caryl A Young ◽  
Vidhya Munnamalai
Keyword(s):  
Hair Cells ◽  
Wnt Pathway ◽  
Organ Of Corti ◽  
Medial Compartment ◽  
Cell Fates ◽  
Spatial Expression ◽  
Fine Grained ◽  
Wnt Ligands ◽  
Mechanosensory Hair Cells ◽  
Canonical Wnt

The mammalian organ of Corti is a highly specialized sensory organ of the cochlea with fine-grained pattern that is essential for auditory function. Previous studies show that the Wnt pathway regulates proliferation, promotes medial compartment formation in the cochlea, differentiation of the mechanosensory hair cells and axon guidance of Type II afferent neurons. WNT ligand expressions are highly dynamic throughout development but are insufficient to explain the roles of the Wnt pathway. We address a potential way for how WNTs specify the medial compartment by characterizing the expression of Porcupine (PORCN), an O-acyltransferase that palmitoylates WNT ligands for secretion. We show PORCN expression across embryonic ages (E)12.5 - E14.5, E16.5, and postnatal day (P)1. Our results showed enriched PORCN in the medial domains during early stages of development, indicating that WNTs have a stronger influence on patterning of the medial compartment. PORCN was rapidly downregulated after E14.5, following the onset of sensory cell differentiation; residual expression remained in some hair cells and supporting cells. On E14.5 and E16.5, we also examined the spatial expression of Gsk3β, an inhibitor of canonical Wnt signaling to determine its potential role in radial patterning of the cochlea. Gsk3β was broadly expressed across the radial axis of the epithelium; therefore, unlikely to control WNT-mediated medial specification. In conclusion, the spatial expression of PORCN enriches WNT secretion from the medial domains of the cochlea to influence the specification of cell fates in the medial sensory domain.

Delta-Notch signalling and the patterning of sensory cell differentiation in the zebrafish ear: evidence from the mind bomb mutant

Development ◽  
1998 ◽  
Vol 125 (23) ◽  
pp. 4637-4644 ◽  
Author(s):  
C. Haddon ◽  
Y.J. Jiang ◽  
L. Smithers ◽  
J. Lewis
Keyword(s):  
Cell Differentiation ◽  
Lateral Inhibition ◽  
Hair Cells ◽  
Sensory Cell ◽  
Cell Types ◽  
Notch Signalling ◽  
Supporting Cells ◽  
Fine Grained ◽  
Mechanosensory Hair Cells ◽  
The Mind

Mechanosensory hair cells in the sensory patches of the vertebrate ear are interspersed among supporting cells, forming a fine-grained pattern of alternating cell types. Analogies with Drosophila mechanosensory bristle development suggest that this pattern could be generated through lateral inhibition mediated by Notch signalling. In the zebrafish ear rudiment, homologues of Notch are widely expressed, while the Delta homologues deltaA, deltaB and deltaD, coding for Notch ligands, are expressed in small numbers of cells in regions where hair cells are soon to differentiate. This suggests that the delta-expressing cells are nascent hair cells, in agreement with findings for Delta1 in the chick. According to the lateral inhibition hypothesis, the nascent hair cells, by expressing Delta protein, would inhibit their neighbours from becoming hair cells, forcing them to be supporting cells instead. The zebrafish mind bomb mutant has abnormalities in the central nervous system, somites, and elsewhere, diagnostic of a failure of Delta-Notch signalling: in the CNS, it shows a neurogenic phenotype accompanied by misregulated delta gene expression. Similar misregulation of delta; genes is seen in the ear, along with misregulation of a Serrate homologue, serrateB, coding for an alternative Notch ligand. Most dramatically, the sensory patches in the mind bomb ear consist solely of hair cells, which are produced in great excess and prematurely; at 36 hours post fertilization, there are more than ten times as many as normal, while supporting cells are absent. A twofold increase is seen in the number of otic neurons also. The findings are strong evidence that lateral inhibition mediated by Delta-Notch signalling controls the pattern of sensory cell differentiation in the ear.

scholarly journals Loss of FLCN inhibits canonical WNT signaling via TFE3

2019 ◽  
Vol 28 (19) ◽  
pp. 3270-3281 ◽  
Author(s):  
John C Kennedy ◽  
Damir Khabibullin ◽  
Thomas Hougard ◽  
Julie Nijmeh ◽  
Wei Shi ◽  
...  
Keyword(s):  
Wnt Pathway ◽  
Lower Lobe ◽  
Fetal Lung ◽  
Lung Fibroblasts ◽  
Pulmonary Cysts ◽  
Wnt Ligands ◽  
Neonatal Lung ◽  
Canonical Wnt ◽  
Human Fetal Lung ◽  
Bhd Syndrome

Abstract Lower lobe predominant pulmonary cysts occur in up to 90% of patients with Birt–Hogg–Dubé (BHD) syndrome, but the key pathologic cell type and signaling events driving this distinct phenotype remain elusive. Through examination of the LungMAP database, we found that folliculin (FLCN) is highly expressed in neonatal lung mesenchymal cells. Using RNA-Seq, we found that inactivation of Flcn in mouse embryonic fibroblasts leads to changes in multiple Wnt ligands, including a 2.8-fold decrease in Wnt2. This was associated with decreased TCF/LEF activity, a readout of canonical WNT activity, after treatment with a GSK3-α/β inhibitor. Similarly, FLCN deficiency in HEK293T cells decreased WNT pathway activity by 76% post-GSK3-α/β inhibition. Inactivation of FLCN in human fetal lung fibroblasts (MRC-5) led to ~ 100-fold decrease in Wnt2 expression and a 33-fold decrease in Wnt7b expression—two ligands known to be necessary for lung development. Furthermore, canonical WNT activity was decreased by 60%. Classic WNT targets such as AXIN2 and BMP4, and WNT enhanceosome members including TCF4, LEF1 and BCL9 were also decreased after GSK3-α/β inhibition. FLCN-deficient MRC-5 cells failed to upregulate LEF1 in response to GSK3-α/β inhibition. Finally, we found that a constitutively active β-catenin could only partially rescue the decreased WNT activity phenotype seen in FLCN-deficient cells, whereas silencing the transcription factor TFE3 completely reversed this phenotype. In summary, our data establish FLCN as a critical regulator of the WNT pathway via TFE3 and suggest that FLCN-dependent defects in WNT pathway developmental cues may contribute to lung cyst pathogenesis in BHD.

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 Canonical Wnt Signaling Pathway on Polarity Formation of Utricle Hair Cells

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Di Deng ◽  
Xiaoqing Qian ◽  
Binjun Chen ◽  
Xiaoyu Yang ◽  
Yanmei Wang ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Inner Ear ◽  
Signaling Pathway ◽  
Hair Cells ◽  
Wnt Pathway ◽  
Wnt Signaling Pathway ◽  
Canonical Wnt Signaling ◽  
Stage Of Development ◽  
Canonical Wnt Pathway ◽  
Canonical Wnt

As part of the inner ear, the vestibular system is responsible for sense of balance, which consists of three semicircular canals, the utricle, and the saccule. Increasing evidence has indicated that the noncanonical Wnt/PCP signaling pathway plays a significant role in the development of the polarity of the inner ear. However, the role of canonical Wnt signaling in the polarity of the vestibule is still not completely clear. In this study, we found that canonical Wnt pathway-related genes are expressed in the early stage of development of the utricle and change dynamically. We conditionally knocked out β-catenin, a canonical Wnt signaling core protein, and found that the cilia orientation of hair cells was disordered with reduced number of hair cells in the utricle. Moreover, regulating the canonical Wnt pathway (Licl and IWP2) in vitro also affected hair cell polarity and indicated that Axin2 may be important in this process. In conclusion, our results not only confirm that the regulation of canonical Wnt signaling affects the number of hair cells in the utricle but also provide evidence for its role in polarity development.

scholarly journals Canonical Wnt signalling is activated during BEC-to-hepatocyte conversion in vivo and modulates liver epithelial cell plasticity in hepatic organoids

2020 ◽  
Author(s):  
Eider Valle-Encinas ◽  
Niya Aleksieva ◽  
Carmen Velasco Martinez ◽  
Michael Dawes ◽  
Matthew Zverev ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Progenitor Cell ◽  
Wnt Pathway ◽  
Hepatocyte Proliferation ◽  
Limiting Factor ◽  
Cell Plasticity ◽  
Wnt Ligands ◽  
Severe Liver Damage ◽  
Canonical Wnt

SummaryWhile it is recognized that the Wnt/ß-catenin pathway orchestrates hepatocyte proliferation in both homeostasis and injury, little is known about the importance of β-catenin in biliary epithelial cell (BEC) plasticity. In this study, the dynamics of activation of the canonical Wnt pathway were investigated during BEC-to-hepatocyte conversion using as a model methionine/choline deficient (MCD)-injured livers where hepatocyte proliferation was compromised by the overexpression of p21. In this model, activation of β-catenin was found an event associated with BEC reprogramming. Using ductal organoids to model BECs transitioning into hepatocytes, we found that activation of the Wnt/ß-catenin pathway in these cells promoted partial escape from a biliary fate and triggered the acquisition of progenitor cell features. Our data furthermore support that BECs are source of Wnt ligands and that Rspo proteins potentially act as the limiting factor controlling the activation of β-catenin activation and BEC reprogramming during severe liver damage.

scholarly journals Fine-tuning of Notch signaling sets the boundary of the organ of Corti and establishes sensory cell fates

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Martin L Basch ◽  
Rogers M Brown ◽  
Hsin-I Jen ◽  
Fatih Semerci ◽  
Frederic Depreux ◽  
...  
Keyword(s):  
Hair Cell ◽  
Notch Signaling ◽  
Hair Cells ◽  
Sensory Cell ◽  
Organ Of Corti ◽  
Fine Tuning ◽  
Pharmacological Treatments ◽  
Cell Fates ◽  
Inner Hair Cells ◽  
Mouse Mutants

The signals that induce the organ of Corti and define its boundaries in the cochlea are poorly understood. We show that two Notch modifiers, Lfng and Mfng, are transiently expressed precisely at the neural boundary of the organ of Corti. Cre-Lox fate mapping shows this region gives rise to inner hair cells and their associated inner phalangeal cells. Mutation of Lfng and Mfng disrupts this boundary, producing unexpected duplications of inner hair cells and inner phalangeal cells. This phenotype is mimicked by other mouse mutants or pharmacological treatments that lower but not abolish Notch signaling. However, strong disruption of Notch signaling causes a very different result, generating many ectopic hair cells at the expense of inner phalangeal cells. Our results show that Notch signaling is finely calibrated in the cochlea to produce precisely tuned levels of signaling that first set the boundary of the organ of Corti and later regulate hair cell development.

scholarly journals Wnt7b Activates Canonical Signaling in Epithelial and Vascular Smooth Muscle Cells through Interactions with Fzd1, Fzd10, and LRP5

2005 ◽  
Vol 25 (12) ◽  
pp. 5022-5030 ◽  
Author(s):  
Zhishan Wang ◽  
Weiguo Shu ◽  
Min Min Lu ◽  
Edward E. Morrisey
Keyword(s):  
Cell Surface ◽  
Wnt Signaling ◽  
Airway Epithelium ◽  
Lung Development ◽  
Wnt Pathway ◽  
Vascular Development ◽  
Placental Development ◽  
Surface Receptors ◽  
Wnt Ligands ◽  
Canonical Wnt

ABSTRACT Wnt7b is a Wnt ligand that has been demonstrated to play critical roles in several developmental processes, including lung airway and vascular development and chorion-allantois fusion during placental development. Wnt signaling involves the binding of Wnt ligands to cell surface receptors of the frizzled family and coreceptors of the LRP5/6 family. However, little is known of the ligand-receptor specificity exhibited by different Wnts, Fzds, and LRPs in Wnt signaling. Expression analysis of Fzds and LRP5/6 in the developing lung and vasculature showed that Fzd1, -4, -7, and -10 and LRP5/6 are expressed in tissue-specific patterns during lung development. Fzd1, -4, and -7 are expressed primarily in the developing lung mesenchyme, and Fzd10 is expressed in airway epithelium. LRP5 and LRP6 are expressed in airway epithelium during lung development, whereas LRP5 but not LRP6 expression is observed in the muscular component of large blood vessels, including the aorta. Cell transfection studies demonstrate that Wnt7b can activate the canonical Wnt pathway but not the noncanonical Wnt pathway in a cell-specific manner. Biochemical analysis demonstrates that Wnt7b can bind to Fzd1 and -10 on the cell surface and cooperatively activate canonical Wnt signaling with these receptors in the presence of LRP5. Together, these data demonstrate that Wnt7b signals through Fzd1 and -10 and LRP5 and implicate these Wnt coreceptors in the regulation of lung airway and vascular development.

scholarly journals Hair necessities: Hair cell differentiation and regeneration

2002 ◽  
Vol 24 (6) ◽  
pp. 9-11
Author(s):  
Matthew Holley
Keyword(s):  
Cell Differentiation ◽  
Hair Cell ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Structural Diversity ◽  
Sensory Epithelium ◽  
Animal Kingdom ◽  
Hair Cell Differentiation ◽  
Human Hearing ◽  
Mechanosensory Hair Cells

Human hearing is governed by approximately 15 500 mechanosensory hair cells in each ear. These cells are located within the organ of Corti, the elongated auditory sensory epithelium that is stretched inside the coiled cochleae of the inner ear. Despite the structural diversity between the organs of hearing throughout the animal kingdom, hair cells are instantly recognizable. Their shapes and sizes vary considerably, but their apices carry a characteristic bundle of actin-filled stereocilia, or hairs, whose tips are connected by stretch-sensitive ‘tip-links’1. However, unlike most other animals, mammals do not regenerate lost hair cells2, consequently most forms of deafness are irreversible.

scholarly journals A Screen for Mutations That Suppress the Phenotype of Drosophila armadillo, the β-Catenin Homolog

Genetics ◽  
2000 ◽  
Vol 155 (4) ◽  
pp. 1725-1740
Author(s):  
Rachel T Cox ◽  
Donald G McEwen ◽  
Denise L Myster ◽  
Robert J Duronio ◽  
Joseph Loureiro ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Adhesion ◽  
Programmed Cell Death ◽  
Cell Survival ◽  
Wnt Pathway ◽  
Genetic Modifier ◽  
Wnt Signaling Pathway ◽  
Adherens Junction ◽  
Cell Fates ◽  
Wnt Signal

Abstract During development signaling pathways coordinate cell fates and regulate the choice between cell survival or programmed cell death. The well-conserved Wingless/Wnt pathway is required for many developmental decisions in all animals. One transducer of the Wingless/Wnt signal is Armadillo/β-catenin. Drosophila Armadillo not only transduces Wingless signal, but also acts in cell-cell adhesion via its role in the epithelial adherens junction. While many components of both the Wingless/Wnt signaling pathway and adherens junctions are known, both processes are complex, suggesting that unknown components influence signaling and junctions. We carried out a genetic modifier screen to identify some of these components by screening for mutations that can suppress the armadillo mutant phenotype. We identified 12 regions of the genome that have this property. From these regions and from additional candidate genes tested we identified four genes that suppress arm: dTCF, puckered, head involution defective (hid), and Dpresenilin. We further investigated the interaction with hid, a known regulator of programmed cell death. Our data suggest that Wg signaling modulates Hid activity and that Hid regulates programmed cell death in a dose-sensitive fashion.

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