The Experts below are selected from a list of 10860 Experts worldwide ranked by ideXlab platform
Colin A. Johnson - One of the best experts on this subject based on the ideXlab platform.
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the ciliary frizzled like receptor TMEM67 regulates canonical wnt β catenin signalling in the developing cerebellum via hoxb5
Scientific Reports, 2019Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Gabrielle Wheway, Dina I Abdelmottaleb, Mohammed E Elasrag, Colin A. JohnsonAbstract:Primary cilia defects result in a group of related pleiotropic malformation syndromes known as ciliopathies, often characterised by cerebellar developmental and foliation defects. Here, we describe the cerebellar anatomical and signalling defects in the TMEM67tm1(Dgen)/H knockout mouse. At mid-gestation, TMEM67 mutant cerebella were hypoplastic and had aberrantly high canonical Wnt/β-catenin signalling, proliferation and apoptosis. Later in development, mutant cerebellar hemispheres had severe foliation defects and inferior lobe malformation, characterized by immature Purkinje cells (PCs). Early postnatal TMEM67 mutant cerebellum had disrupted ciliogenesis and reduced responsiveness to Shh signalling. Transcriptome profiling of TMEM67 mutant cerebella identified ectopic increased expression of homeobox-type transcription factors (Hoxa5, Hoxa4, Hoxb5 and Hoxd3), normally required for early rostral hindbrain patterning. HOXB5 protein levels were increased in the inferior lobe, and increased canonical Wnt signalling, following loss of TMEM67, was dependent on HOXB5. HOXB5 occupancy at the β-catenin promoter was significantly increased by activation of canonical Wnt signalling in TMEM67−/− mutant cerebellar neurones, suggesting that increased canonical Wnt signalling following mutation or loss of TMEM67 was directly dependent on HOXB5. Our results link dysregulated expression of Hox group genes with ciliary Wnt signalling defects in the developing cerebellum, providing new mechanistic insights into ciliopathy cerebellar hypoplasia phenotypes.
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The Meckel-Gruber Syndrome protein TMEM67 (meckelin) regulates basal body planar polarization and non-canonical Wnt signalling via Wnt5a and ROR2
Cilia, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Daniel J. JaggerAbstract:Results: TMEM67 mutant phenotypes include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/ kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration. TMEM67 (meckelin) is essential for phosphorylation of the noncanonical Wnt receptor ROR2 (receptor tyrosine kinaselike orphan receptor 2) upon Wnt5a stimulation. ROR2 interacts with the intracellular C-terminal domain of TMEM67 and co-localizes with TMEM67 at the ciliary transition zone. The N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. TMEM67 mutant embryonic lungs in ex vivo culture failed to respond to Wnt5a stimulation of epithelial morphogenesis. However, stimulating the non-canonical Wnt pathway downstream of the receptor by activating RhoA resulted in an elicited response and the rescue of lung hypoplasia phenotypes.
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Biochemical characterization of transmembrane proteins (TMEMs) in the ciliary transition zone
Cilia, 2015Co-Authors: E Shoaib, Zakia Abdelhamed, Katarzyna Szymanska, Sandra M. Bell, Ewan E. Morrison, Colin A. JohnsonAbstract:Objective Ciliopathies are a group of heterogeneous disorders caused by mutations in proteins associated with primary cilia. Many proteins that are mutated in ciliopathies Joubert syndrome (JBTS), Meckel-Gruber syndrome (MKS) and nephronophthisis (NPHP) are localized to the transition zone (TZ), a compartment of the proximal region of the cilium. In particular, a protein complex known as the “MKS-JBTS module” contains many transmembrane proteins (TMEMs) that are mutated in these conditions. Here, we aim to understand the role of the ciliary proteins TMEM67, TMEM138, TMEM216, TMEM237, TMEM17 and TMEM231 by characterizing their biochemical functions and potential interactions. We hypothesize that pathogenic missense mutations disrupt the putative TMEM complex or localization to the TZ. Furthermore, we aim to identify new interacting proteins of TMEMs, including potential ligands of the orphan receptor TMEM67.
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the meckel gruber syndrome protein TMEM67 controls basal body positioning and epithelial branching morphogenesis in mice via the non canonical wnt pathway
Disease Models & Mechanisms, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Gabrielle Wheway, Daniel J. JaggerAbstract:Ciliopathies are a group of developmental disorders that manifest with multi-organ anomalies. Mutations in TMEM67 (MKS3) cause a range of human ciliopathies, including Meckel-Gruber and Joubert syndromes. In this study we describe multi-organ developmental abnormalities in the TMEM67(tm1Dgen/H1) knockout mouse that closely resemble those seen in Wnt5a and Ror2 knockout mice. These include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration, although planar cell polarity and apical planar asymmetry in the organ of Corti were normal. TMEM67 (meckelin) is essential for phosphorylation of the non-canonical Wnt receptor ROR2 (receptor-tyrosine-kinase-like orphan receptor 2) upon stimulation with Wnt5a-conditioned medium. ROR2 also colocalises and interacts with TMEM67 at the ciliary transition zone. Additionally, the extracellular N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. Cultured lungs of TMEM67 mutant mice failed to respond to stimulation of epithelial branching morphogenesis by Wnt5a. Wnt5a also inhibited both the Shh and canonical Wnt/β-catenin signalling pathways in wild-type embryonic lung. Pulmonary hypoplasia phenotypes, including loss of correct epithelial branching morphogenesis and cell polarity, were rescued by stimulating the non-canonical Wnt pathway downstream of the Wnt5a-TMEM67-ROR2 axis by activating RhoA. We propose that TMEM67 is a receptor that has a main role in non-canonical Wnt signalling, mediated by Wnt5a and ROR2, and normally represses Shh signalling. Downstream therapeutic targeting of the Wnt5a-TMEM67-ROR2 axis might, therefore, reduce or prevent pulmonary hypoplasia in ciliopathies and other congenital conditions.
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Cerebellar Malformations in the TMEM67 Ciliopathy Mouse Model are Caused by Combined Wnt and Shh Signalling Systems Dysregulations
The FASEB Journal, 2015Co-Authors: Zakia Abdelhamed, C. F. Inglehearn, Carmel Toomes, Colin A. JohnsonAbstract:Objectives: This study focuses on the characterization of the cerebellum in the newly-described TMEM67tm1(Dgen) knockout ciliopathy mouse model. Methods: various molecular, immunohistochemical,prim...
Zakia Abdelhamed - One of the best experts on this subject based on the ideXlab platform.
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the ciliary frizzled like receptor TMEM67 regulates canonical wnt β catenin signalling in the developing cerebellum via hoxb5
Scientific Reports, 2019Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Gabrielle Wheway, Dina I Abdelmottaleb, Mohammed E Elasrag, Colin A. JohnsonAbstract:Primary cilia defects result in a group of related pleiotropic malformation syndromes known as ciliopathies, often characterised by cerebellar developmental and foliation defects. Here, we describe the cerebellar anatomical and signalling defects in the TMEM67tm1(Dgen)/H knockout mouse. At mid-gestation, TMEM67 mutant cerebella were hypoplastic and had aberrantly high canonical Wnt/β-catenin signalling, proliferation and apoptosis. Later in development, mutant cerebellar hemispheres had severe foliation defects and inferior lobe malformation, characterized by immature Purkinje cells (PCs). Early postnatal TMEM67 mutant cerebellum had disrupted ciliogenesis and reduced responsiveness to Shh signalling. Transcriptome profiling of TMEM67 mutant cerebella identified ectopic increased expression of homeobox-type transcription factors (Hoxa5, Hoxa4, Hoxb5 and Hoxd3), normally required for early rostral hindbrain patterning. HOXB5 protein levels were increased in the inferior lobe, and increased canonical Wnt signalling, following loss of TMEM67, was dependent on HOXB5. HOXB5 occupancy at the β-catenin promoter was significantly increased by activation of canonical Wnt signalling in TMEM67−/− mutant cerebellar neurones, suggesting that increased canonical Wnt signalling following mutation or loss of TMEM67 was directly dependent on HOXB5. Our results link dysregulated expression of Hox group genes with ciliary Wnt signalling defects in the developing cerebellum, providing new mechanistic insights into ciliopathy cerebellar hypoplasia phenotypes.
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The Meckel-Gruber Syndrome protein TMEM67 (meckelin) regulates basal body planar polarization and non-canonical Wnt signalling via Wnt5a and ROR2
Cilia, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Daniel J. JaggerAbstract:Results: TMEM67 mutant phenotypes include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/ kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration. TMEM67 (meckelin) is essential for phosphorylation of the noncanonical Wnt receptor ROR2 (receptor tyrosine kinaselike orphan receptor 2) upon Wnt5a stimulation. ROR2 interacts with the intracellular C-terminal domain of TMEM67 and co-localizes with TMEM67 at the ciliary transition zone. The N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. TMEM67 mutant embryonic lungs in ex vivo culture failed to respond to Wnt5a stimulation of epithelial morphogenesis. However, stimulating the non-canonical Wnt pathway downstream of the receptor by activating RhoA resulted in an elicited response and the rescue of lung hypoplasia phenotypes.
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Biochemical characterization of transmembrane proteins (TMEMs) in the ciliary transition zone
Cilia, 2015Co-Authors: E Shoaib, Zakia Abdelhamed, Katarzyna Szymanska, Sandra M. Bell, Ewan E. Morrison, Colin A. JohnsonAbstract:Objective Ciliopathies are a group of heterogeneous disorders caused by mutations in proteins associated with primary cilia. Many proteins that are mutated in ciliopathies Joubert syndrome (JBTS), Meckel-Gruber syndrome (MKS) and nephronophthisis (NPHP) are localized to the transition zone (TZ), a compartment of the proximal region of the cilium. In particular, a protein complex known as the “MKS-JBTS module” contains many transmembrane proteins (TMEMs) that are mutated in these conditions. Here, we aim to understand the role of the ciliary proteins TMEM67, TMEM138, TMEM216, TMEM237, TMEM17 and TMEM231 by characterizing their biochemical functions and potential interactions. We hypothesize that pathogenic missense mutations disrupt the putative TMEM complex or localization to the TZ. Furthermore, we aim to identify new interacting proteins of TMEMs, including potential ligands of the orphan receptor TMEM67.
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the meckel gruber syndrome protein TMEM67 controls basal body positioning and epithelial branching morphogenesis in mice via the non canonical wnt pathway
Disease Models & Mechanisms, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Gabrielle Wheway, Daniel J. JaggerAbstract:Ciliopathies are a group of developmental disorders that manifest with multi-organ anomalies. Mutations in TMEM67 (MKS3) cause a range of human ciliopathies, including Meckel-Gruber and Joubert syndromes. In this study we describe multi-organ developmental abnormalities in the TMEM67(tm1Dgen/H1) knockout mouse that closely resemble those seen in Wnt5a and Ror2 knockout mice. These include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration, although planar cell polarity and apical planar asymmetry in the organ of Corti were normal. TMEM67 (meckelin) is essential for phosphorylation of the non-canonical Wnt receptor ROR2 (receptor-tyrosine-kinase-like orphan receptor 2) upon stimulation with Wnt5a-conditioned medium. ROR2 also colocalises and interacts with TMEM67 at the ciliary transition zone. Additionally, the extracellular N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. Cultured lungs of TMEM67 mutant mice failed to respond to stimulation of epithelial branching morphogenesis by Wnt5a. Wnt5a also inhibited both the Shh and canonical Wnt/β-catenin signalling pathways in wild-type embryonic lung. Pulmonary hypoplasia phenotypes, including loss of correct epithelial branching morphogenesis and cell polarity, were rescued by stimulating the non-canonical Wnt pathway downstream of the Wnt5a-TMEM67-ROR2 axis by activating RhoA. We propose that TMEM67 is a receptor that has a main role in non-canonical Wnt signalling, mediated by Wnt5a and ROR2, and normally represses Shh signalling. Downstream therapeutic targeting of the Wnt5a-TMEM67-ROR2 axis might, therefore, reduce or prevent pulmonary hypoplasia in ciliopathies and other congenital conditions.
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Cerebellar Malformations in the TMEM67 Ciliopathy Mouse Model are Caused by Combined Wnt and Shh Signalling Systems Dysregulations
The FASEB Journal, 2015Co-Authors: Zakia Abdelhamed, C. F. Inglehearn, Carmel Toomes, Colin A. JohnsonAbstract:Objectives: This study focuses on the characterization of the cerebellum in the newly-described TMEM67tm1(Dgen) knockout ciliopathy mouse model. Methods: various molecular, immunohistochemical,prim...
Dragana Josifova - One of the best experts on this subject based on the ideXlab platform.
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A transition zone complex regulates mammalian ciliogenesis and ciliary membrane composition
Nature Genetics, 2011Co-Authors: Francesc R Garcia-gonzalo, María Salomé Sirerol-piquer, Thomas R. Noriega, Allen D. Seol, Jon F. Robinson, Kevin C. Corbit, Edgar A Otto, Christopher L. Bennett, Gokul Ramaswami, Dragana JosifovaAbstract:Jeremy Reiter and colleagues show that Tctn1 is a component of a transition zone complex that regulates ciliogenesis and ciliary membrane composition. They also identify a likely causal mutation in TCTN1 in two siblings with Joubert syndrome. Mutations affecting ciliary components cause ciliopathies. As described here, we investigated Tectonic1 (Tctn1), a regulator of mouse Hedgehog signaling, and found that it is essential for ciliogenesis in some, but not all, tissues. Cell types that do not require Tctn1 for ciliogenesis require it to localize select membrane-associated proteins to the cilium, including Arl13b, AC3, Smoothened and Pkd2. Tctn1 forms a complex with multiple ciliopathy proteins associated with Meckel and Joubert syndromes, including Mks1, Tmem216, TMEM67, Cep290, B9d1, Tctn2 and Cc2d2a. Components of this complex co-localize at the transition zone, a region between the basal body and ciliary axoneme. Like Tctn1, loss of Tctn2, TMEM67 or Cc2d2a causes tissue-specific defects in ciliogenesis and ciliary membrane composition. Consistent with a shared function for complex components, we identified a mutation in TCTN1 that causes Joubert syndrome. Thus, a transition zone complex of Meckel and Joubert syndrome proteins regulates ciliary assembly and trafficking, suggesting that transition zone dysfunction is the cause of these ciliopathies.
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A transition zone complex regulates mammalian ciliogenesis and ciliary membrane composition
Nature Genetics, 2011Co-Authors: Kevin C. Corbit, María Salomé Sirerol-piquer, Thomas R. Noriega, Allen D. Seol, Jon F. Robinson, Edgar A Otto, Christopher L. Bennett, Gokul Ramaswami, Dragana JosifovaAbstract:Mutations affecting ciliary components cause ciliopathies. As described here, we investigated Tectonic1 (Tctn1), a regulator of mouse Hedgehog signaling, and found that it is essential for ciliogenesis in some, but not all, tissues. Cell types that do not require Tctn1 for ciliogenesis require it to localize select membrane-associated proteins to the cilium, including Arl13b, AC3, Smoothened and Pkd2. Tctn1 forms a complex with multiple ciliopathy proteins associated with Meckel and Joubert syndromes, including Mks1, Tmem216, TMEM67, Cep290, B9d1, Tctn2 and Cc2d2a. Components of this complex co-localize at the transition zone, a region between the basal body and ciliary axoneme. Like Tctn1, loss of Tctn2, TMEM67 or Cc2d2a causes tissue-specific defects in ciliogenesis and ciliary membrane composition. Consistent with a shared function for complex components, we identified a mutation in TCTN1 that causes Joubert syndrome. Thus, a transition zone complex of Meckel and Joubert syndrome proteins regulates ciliary assembly and trafficking, suggesting that transition zone dysfunction is the cause of these ciliopathies.
C. F. Inglehearn - One of the best experts on this subject based on the ideXlab platform.
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the ciliary frizzled like receptor TMEM67 regulates canonical wnt β catenin signalling in the developing cerebellum via hoxb5
Scientific Reports, 2019Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Gabrielle Wheway, Dina I Abdelmottaleb, Mohammed E Elasrag, Colin A. JohnsonAbstract:Primary cilia defects result in a group of related pleiotropic malformation syndromes known as ciliopathies, often characterised by cerebellar developmental and foliation defects. Here, we describe the cerebellar anatomical and signalling defects in the TMEM67tm1(Dgen)/H knockout mouse. At mid-gestation, TMEM67 mutant cerebella were hypoplastic and had aberrantly high canonical Wnt/β-catenin signalling, proliferation and apoptosis. Later in development, mutant cerebellar hemispheres had severe foliation defects and inferior lobe malformation, characterized by immature Purkinje cells (PCs). Early postnatal TMEM67 mutant cerebellum had disrupted ciliogenesis and reduced responsiveness to Shh signalling. Transcriptome profiling of TMEM67 mutant cerebella identified ectopic increased expression of homeobox-type transcription factors (Hoxa5, Hoxa4, Hoxb5 and Hoxd3), normally required for early rostral hindbrain patterning. HOXB5 protein levels were increased in the inferior lobe, and increased canonical Wnt signalling, following loss of TMEM67, was dependent on HOXB5. HOXB5 occupancy at the β-catenin promoter was significantly increased by activation of canonical Wnt signalling in TMEM67−/− mutant cerebellar neurones, suggesting that increased canonical Wnt signalling following mutation or loss of TMEM67 was directly dependent on HOXB5. Our results link dysregulated expression of Hox group genes with ciliary Wnt signalling defects in the developing cerebellum, providing new mechanistic insights into ciliopathy cerebellar hypoplasia phenotypes.
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The Meckel-Gruber Syndrome protein TMEM67 (meckelin) regulates basal body planar polarization and non-canonical Wnt signalling via Wnt5a and ROR2
Cilia, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Daniel J. JaggerAbstract:Results: TMEM67 mutant phenotypes include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/ kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration. TMEM67 (meckelin) is essential for phosphorylation of the noncanonical Wnt receptor ROR2 (receptor tyrosine kinaselike orphan receptor 2) upon Wnt5a stimulation. ROR2 interacts with the intracellular C-terminal domain of TMEM67 and co-localizes with TMEM67 at the ciliary transition zone. The N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. TMEM67 mutant embryonic lungs in ex vivo culture failed to respond to Wnt5a stimulation of epithelial morphogenesis. However, stimulating the non-canonical Wnt pathway downstream of the receptor by activating RhoA resulted in an elicited response and the rescue of lung hypoplasia phenotypes.
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the meckel gruber syndrome protein TMEM67 controls basal body positioning and epithelial branching morphogenesis in mice via the non canonical wnt pathway
Disease Models & Mechanisms, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Gabrielle Wheway, Daniel J. JaggerAbstract:Ciliopathies are a group of developmental disorders that manifest with multi-organ anomalies. Mutations in TMEM67 (MKS3) cause a range of human ciliopathies, including Meckel-Gruber and Joubert syndromes. In this study we describe multi-organ developmental abnormalities in the TMEM67(tm1Dgen/H1) knockout mouse that closely resemble those seen in Wnt5a and Ror2 knockout mice. These include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration, although planar cell polarity and apical planar asymmetry in the organ of Corti were normal. TMEM67 (meckelin) is essential for phosphorylation of the non-canonical Wnt receptor ROR2 (receptor-tyrosine-kinase-like orphan receptor 2) upon stimulation with Wnt5a-conditioned medium. ROR2 also colocalises and interacts with TMEM67 at the ciliary transition zone. Additionally, the extracellular N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. Cultured lungs of TMEM67 mutant mice failed to respond to stimulation of epithelial branching morphogenesis by Wnt5a. Wnt5a also inhibited both the Shh and canonical Wnt/β-catenin signalling pathways in wild-type embryonic lung. Pulmonary hypoplasia phenotypes, including loss of correct epithelial branching morphogenesis and cell polarity, were rescued by stimulating the non-canonical Wnt pathway downstream of the Wnt5a-TMEM67-ROR2 axis by activating RhoA. We propose that TMEM67 is a receptor that has a main role in non-canonical Wnt signalling, mediated by Wnt5a and ROR2, and normally represses Shh signalling. Downstream therapeutic targeting of the Wnt5a-TMEM67-ROR2 axis might, therefore, reduce or prevent pulmonary hypoplasia in ciliopathies and other congenital conditions.
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Cerebellar Malformations in the TMEM67 Ciliopathy Mouse Model are Caused by Combined Wnt and Shh Signalling Systems Dysregulations
The FASEB Journal, 2015Co-Authors: Zakia Abdelhamed, C. F. Inglehearn, Carmel Toomes, Colin A. JohnsonAbstract:Objectives: This study focuses on the characterization of the cerebellum in the newly-described TMEM67tm1(Dgen) knockout ciliopathy mouse model. Methods: various molecular, immunohistochemical,prim...
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variable expressivity of ciliopathy neurological phenotypes that encompass meckel gruber syndrome and joubert syndrome is caused by complex de regulated ciliogenesis shh and wnt signalling defects
Human Molecular Genetics, 2013Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Gabrielle Wheway, Katarzyna Szymanska, Colin A. JohnsonAbstract:The ciliopathies are a group of heterogeneous diseases with considerable variations in phenotype for allelic conditions such as Meckel-Gruber syndrome (MKS) and Joubert syndrome (JBTS) even at the inter-individual level within families. In humans, mutations in TMEM67 (also known as MKS3) cause both MKS and JBTS, with TMEM67 encoding the orphan receptor meckelin (TMEM67) that localizes to the ciliary transition zone. We now describe the TMEM67(tm1(Dgen/H)) knockout mouse model that recapitulates the brain phenotypic variability of these human ciliopathies, with categorization of TMEM67 mutant animals into two phenotypic groups. An MKS-like incipient congenic group (F6 to F10) manifested very variable neurological features (including exencephaly, and frontal/occipital encephalocele) that were associated with the loss of primary cilia, diminished Shh signalling and dorsalization of the caudal neural tube. The 'MKS-like' group also had high de-regulated canonical Wnt/β-catenin signalling associated with hyper-activated Dishevelled-1 (Dvl-1) localized to the basal body. Conversely, a second fully congenic group (F > 10) had less variable features pathognomonic for JBTS (including cerebellar hypoplasia), and retention of abnormal bulbous cilia associated with mild neural tube ventralization. The 'JBTS-like' group had de-regulated low levels of canonical Wnt signalling associated with the loss of Dvl-1 localization to the basal body. Our results suggest that modifier alleles partially determine the variation between MKS and JBTS, implicating the interaction between Dvl-1 and meckelin, or other components of the ciliary transition zone. The TMEM67(tm1(Dgen/H)) line is unique in modelling the variable expressivity of phenotypes in these two ciliopathies.
Carmel Toomes - One of the best experts on this subject based on the ideXlab platform.
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the ciliary frizzled like receptor TMEM67 regulates canonical wnt β catenin signalling in the developing cerebellum via hoxb5
Scientific Reports, 2019Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Gabrielle Wheway, Dina I Abdelmottaleb, Mohammed E Elasrag, Colin A. JohnsonAbstract:Primary cilia defects result in a group of related pleiotropic malformation syndromes known as ciliopathies, often characterised by cerebellar developmental and foliation defects. Here, we describe the cerebellar anatomical and signalling defects in the TMEM67tm1(Dgen)/H knockout mouse. At mid-gestation, TMEM67 mutant cerebella were hypoplastic and had aberrantly high canonical Wnt/β-catenin signalling, proliferation and apoptosis. Later in development, mutant cerebellar hemispheres had severe foliation defects and inferior lobe malformation, characterized by immature Purkinje cells (PCs). Early postnatal TMEM67 mutant cerebellum had disrupted ciliogenesis and reduced responsiveness to Shh signalling. Transcriptome profiling of TMEM67 mutant cerebella identified ectopic increased expression of homeobox-type transcription factors (Hoxa5, Hoxa4, Hoxb5 and Hoxd3), normally required for early rostral hindbrain patterning. HOXB5 protein levels were increased in the inferior lobe, and increased canonical Wnt signalling, following loss of TMEM67, was dependent on HOXB5. HOXB5 occupancy at the β-catenin promoter was significantly increased by activation of canonical Wnt signalling in TMEM67−/− mutant cerebellar neurones, suggesting that increased canonical Wnt signalling following mutation or loss of TMEM67 was directly dependent on HOXB5. Our results link dysregulated expression of Hox group genes with ciliary Wnt signalling defects in the developing cerebellum, providing new mechanistic insights into ciliopathy cerebellar hypoplasia phenotypes.
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The Meckel-Gruber Syndrome protein TMEM67 (meckelin) regulates basal body planar polarization and non-canonical Wnt signalling via Wnt5a and ROR2
Cilia, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Daniel J. JaggerAbstract:Results: TMEM67 mutant phenotypes include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/ kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration. TMEM67 (meckelin) is essential for phosphorylation of the noncanonical Wnt receptor ROR2 (receptor tyrosine kinaselike orphan receptor 2) upon Wnt5a stimulation. ROR2 interacts with the intracellular C-terminal domain of TMEM67 and co-localizes with TMEM67 at the ciliary transition zone. The N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. TMEM67 mutant embryonic lungs in ex vivo culture failed to respond to Wnt5a stimulation of epithelial morphogenesis. However, stimulating the non-canonical Wnt pathway downstream of the receptor by activating RhoA resulted in an elicited response and the rescue of lung hypoplasia phenotypes.
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the meckel gruber syndrome protein TMEM67 controls basal body positioning and epithelial branching morphogenesis in mice via the non canonical wnt pathway
Disease Models & Mechanisms, 2015Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Colin A. Johnson, Gabrielle Wheway, Daniel J. JaggerAbstract:Ciliopathies are a group of developmental disorders that manifest with multi-organ anomalies. Mutations in TMEM67 (MKS3) cause a range of human ciliopathies, including Meckel-Gruber and Joubert syndromes. In this study we describe multi-organ developmental abnormalities in the TMEM67(tm1Dgen/H1) knockout mouse that closely resemble those seen in Wnt5a and Ror2 knockout mice. These include pulmonary hypoplasia, ventricular septal defects, shortening of the body longitudinal axis, limb abnormalities, and cochlear hair cell stereociliary bundle orientation and basal body/kinocilium positioning defects. The basal body/kinocilium complex was often uncoupled from the hair bundle, suggesting aberrant basal body migration, although planar cell polarity and apical planar asymmetry in the organ of Corti were normal. TMEM67 (meckelin) is essential for phosphorylation of the non-canonical Wnt receptor ROR2 (receptor-tyrosine-kinase-like orphan receptor 2) upon stimulation with Wnt5a-conditioned medium. ROR2 also colocalises and interacts with TMEM67 at the ciliary transition zone. Additionally, the extracellular N-terminal domain of TMEM67 preferentially binds to Wnt5a in an in vitro binding assay. Cultured lungs of TMEM67 mutant mice failed to respond to stimulation of epithelial branching morphogenesis by Wnt5a. Wnt5a also inhibited both the Shh and canonical Wnt/β-catenin signalling pathways in wild-type embryonic lung. Pulmonary hypoplasia phenotypes, including loss of correct epithelial branching morphogenesis and cell polarity, were rescued by stimulating the non-canonical Wnt pathway downstream of the Wnt5a-TMEM67-ROR2 axis by activating RhoA. We propose that TMEM67 is a receptor that has a main role in non-canonical Wnt signalling, mediated by Wnt5a and ROR2, and normally represses Shh signalling. Downstream therapeutic targeting of the Wnt5a-TMEM67-ROR2 axis might, therefore, reduce or prevent pulmonary hypoplasia in ciliopathies and other congenital conditions.
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Cerebellar Malformations in the TMEM67 Ciliopathy Mouse Model are Caused by Combined Wnt and Shh Signalling Systems Dysregulations
The FASEB Journal, 2015Co-Authors: Zakia Abdelhamed, C. F. Inglehearn, Carmel Toomes, Colin A. JohnsonAbstract:Objectives: This study focuses on the characterization of the cerebellum in the newly-described TMEM67tm1(Dgen) knockout ciliopathy mouse model. Methods: various molecular, immunohistochemical,prim...
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variable expressivity of ciliopathy neurological phenotypes that encompass meckel gruber syndrome and joubert syndrome is caused by complex de regulated ciliogenesis shh and wnt signalling defects
Human Molecular Genetics, 2013Co-Authors: Zakia Abdelhamed, Subaashini Natarajan, C. F. Inglehearn, Carmel Toomes, Gabrielle Wheway, Katarzyna Szymanska, Colin A. JohnsonAbstract:The ciliopathies are a group of heterogeneous diseases with considerable variations in phenotype for allelic conditions such as Meckel-Gruber syndrome (MKS) and Joubert syndrome (JBTS) even at the inter-individual level within families. In humans, mutations in TMEM67 (also known as MKS3) cause both MKS and JBTS, with TMEM67 encoding the orphan receptor meckelin (TMEM67) that localizes to the ciliary transition zone. We now describe the TMEM67(tm1(Dgen/H)) knockout mouse model that recapitulates the brain phenotypic variability of these human ciliopathies, with categorization of TMEM67 mutant animals into two phenotypic groups. An MKS-like incipient congenic group (F6 to F10) manifested very variable neurological features (including exencephaly, and frontal/occipital encephalocele) that were associated with the loss of primary cilia, diminished Shh signalling and dorsalization of the caudal neural tube. The 'MKS-like' group also had high de-regulated canonical Wnt/β-catenin signalling associated with hyper-activated Dishevelled-1 (Dvl-1) localized to the basal body. Conversely, a second fully congenic group (F > 10) had less variable features pathognomonic for JBTS (including cerebellar hypoplasia), and retention of abnormal bulbous cilia associated with mild neural tube ventralization. The 'JBTS-like' group had de-regulated low levels of canonical Wnt signalling associated with the loss of Dvl-1 localization to the basal body. Our results suggest that modifier alleles partially determine the variation between MKS and JBTS, implicating the interaction between Dvl-1 and meckelin, or other components of the ciliary transition zone. The TMEM67(tm1(Dgen/H)) line is unique in modelling the variable expressivity of phenotypes in these two ciliopathies.
