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Dan Doherty - One of the best experts on this subject based on the ideXlab platform.
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Prospective Evaluation of Kidney Disease in Joubert Syndrome
Clinical journal of the American Society of Nephrology : CJASN, 2017Co-Authors: Leah R. Fleming, Dan Doherty, Melissa A Parisi, Ian A. Glass, Joy Bryant, Roxanne Fischer, Baris Turkbey, Peter L. Choyke, Kailash Daryanani, Meghana VemulapalliAbstract:Background and objectives Joubert syndrome is a genetically heterogeneous ciliopathy associated with >30 genes. The characteristics of kidney disease and genotype-phenotype correlations have not been evaluated in a large cohort at a single center. Design, setting, participants, & measurements We evaluated 97 individuals with Joubert syndrome at the National Institutes of Health Clinical Center using abdominal ultrasonography, blood and urine chemistries, and DNA sequencing. Results Patients were ages 0.6–36 years old (mean of 9.0±7.6 years old); 41 were female. Mutations were identified in 19 genes in 92 patients; two thirds of the mutations resided in six genes: TMEM67, C5orf42, CC2D2A, CEP290, AHI1, and KIAA0586. Kidney disease was detected in 30%, most commonly in association with the following genes: CEP290 (six of six), TMEM67 (11 of 22), and AHI1 (three of six). No kidney disease was identified in patients with mutations in C5orf42 (zero of 15) or KIAA0586 (zero of six). Prenatal ultrasonography of kidneys was normal in 72% of patients with kidney disease. Specific types of kidney disease included nephronophthisis (31%), an overlap phenotype of autosomal recessive polycystic kidney disease/nephronophthisis (35%), unilateral multicystic dysplastic kidney (10%), and indeterminate-type cystic kidney disease (24%). Early-onset hypertension occurred in 24% of patients with kidney disease. Age at ESRD (n=13) ranged from 6 to 24 years old (mean of 11.3±4.8 years old). Conclusions Kidney disease occurs in up to one third of patients with Joubert syndrome, most commonly in those with mutations in CEP290, TMEM67, and AHI1. Patients with mutations in C5orf42 or KIAA0586 are less likely to develop kidney disease. Prenatal ultrasonography is a poor predictor of kidney involvement in Joubert syndrome. Unilateral multicystic dysplastic kidney and autosomal recessive polycystic kidney disease–like enlarged kidneys with early-onset hypertension can be part of the Joubert syndrome kidney phenotype.
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Genotype-Phenotype correlations in Joubert Syndrome in the Era of Next Generation Sequencing
Cilia, 2015Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Jennifer C Dempsey, Diana R. O’day, Christine R. Isabella, Brian J. O'roak, Jay Shendure, Ian A. Glass, Dan DohertyAbstract:Results Core JS diagnostic features (hypotonia, ataxia, cognitive dysfunction, oculo-motor apraxia) were present in >80% of individuals, while abnormal breathing pattern was reported in 60%. Frequently associated features included retinal dystrophy (31.4%), renal disease (20.9%), coloboma (17.7%), polydactyly (15.3%), liver fibrosis (15.2%) and encephalocele (8%). Liver fibrosis and coloboma were strongly associated with each other (Odds Ratio 7.0, 95% Confidence Interval = 3.0-13.2), while retinal dystrophy and renal disease were weakly associated (O.R. 2.2, 95%C. I. = 1.7-5.6). Additional clinical features included other brain abnormalities (n = 73), seizures (n = 49), cleft palate (n = 16), hearing loss (n = 14) and psychiatric problems (n = 45). The genetic cause was identified in 60% of families, with 5 genes accounting for the majority of patients (C5ORF42, CEP290, CC2D2A, AHI1, TMEM67). Bi-allelic causal mutations in B9D2 and C2CD3 were identified in 2 families each. Bi-allelic mutations in 2 different genes were identified in 4 families and heterozygous mutations (in addition to the causal mutation) were present in 62 individuals. Significant (p
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Live imaging of Rab8 trafficking defects in CC2D2A mutant zebrafish
Cilia, 2012Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Dan Doherty, A Forbes, Cecilia B. MoensAbstract:Primary cilia provide a means of regulating and concentrating receptors and other proteins essential for transmission of sensory signals or signaling pathways. Consequently, a thorough understanding of the sorting and trafficking mechanisms that allow appropriate protein delivery to the ciliary compartment is crucial to our understanding of ciliary function in development, homeostasis and disease. Recent work has demonstrated that ciliopathy proteins, such as CC2D2A, are localized to the transition zone at the base of the cilium and function to regulate protein entry into the ciliary compartment. Upstream of the cilium, small GTPases from the Rab family participate in controlling trafficking of ciliary-directed proteins. Here, we describe the relationship between the transition zone protein CC2D2A and Rab8 trafficking in photoreceptors. Detailed phenotypic analysis of a zebrafish CC2D2A mutant reveals typical ciliopathy phenotypes including cystic kidneys and abnormal photoreceptor outer segments. Mislocalization of opsins in mutant photoreceptors and massive accumulation of vesicles suggest a role for CC2D2A in vesicle trafficking. Partial rab8 knockdown enhances the photoreceptor phenotype of CC2D2A mutants. A fluorescently-tagged Rab8 transgene demonstrates a punctate localization pattern for Rab8 in photoreceptors that is disrupted in the absence of CC2D2A. Live imaging of Rab8 trafficking in zebrafish photoreceptors reveals complex and highly dynamic movements of Rab8 puncta towards different cellular destinations, including the outer segment and the synapse, which are differentially affected by loss of CC2D2A function.
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the ciliopathy gene CC2D2A controls zebrafish photoreceptor outer segment development through a role in rab8 dependent vesicle trafficking
Human Molecular Genetics, 2011Co-Authors: Ruxandra Bachmanngagescu, George W Stearns, Susan E Brockerhoff, Brian A Link, Ian G. Phelps, Cecilia B. Moens, Dan DohertyAbstract:Ciliopathies are a genetically and phenotypically heterogeneous group of human developmental disorders whose root cause is the absence or dysfunction of primary cilia. Joubert syndrome is characterized by a distinctive hindbrain malformation variably associated with retinal dystrophy and cystic kidney disease. Mutations in CC2D2A are found in ∼10% of patients with Joubert syndrome. Here we describe the retinal phenotype of CC2D2A mutant zebrafish consisting of disorganized rod and cone photoreceptor outer segments resulting in abnormal visual function as measured by electroretinogram. Our analysis reveals trafficking defects in mutant photoreceptors affecting transmembrane outer segment proteins (opsins) and striking accumulation of vesicles, suggesting a role for CC2D2A in vesicle trafficking and fusion. This is further supported by mislocalization of Rab8, a key regulator of opsin carrier vesicle trafficking, in CC2D2A mutant photoreceptors and by enhancement of the CC2D2A retinal and kidney phenotypes with partial knockdown of rab8. We demonstrate that CC2D2A localizes to the connecting cilium in photoreceptors and to the transition zone in other ciliated cell types and that cilia are present in these cells in CC2D2A mutants, arguing against a primary function for CC2D2A in ciliogenesis. Our data support a model where CC2D2A, localized at the photoreceptor connecting cilium/transition zone, facilitates protein transport through a role in Rab8-dependent vesicle trafficking and fusion.
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co occurrence of joubert syndrome and jeune asphyxiating thoracic dystrophy
American Journal of Medical Genetics Part A, 2010Co-Authors: Anna Lehman, Dan Doherty, Ian A. Glass, Patrice Eydoux, David Chitayat, Bhy Chung, Sylvie Langlois, Siuli Yong, R B Lowry, Friedhelm HildebrandtAbstract:Ciliary disorders share typical features, such as polydactyly, renal and biliary cystic dysplasia, and retinitis pigmentosa, which often overlap across diagnostic entities. We report on two siblings of consanguineous parents and two unrelated children, both of unrelated parents, with co-occurrence of Joubert syndrome and Jeune asphyxiating thoracic dystrophy, an association that adds to the observation of common final patterns of malformations in ciliary disorders. Using homozygosity mapping in the siblings, we were able to exclude all known genes/loci for both syndromes except for INVS, AHI1, and three genes from the previously described Jeune locus at 15q13. No pathogenic variants were found in these genes by direct sequencing. In the third child reported, sequencing of RPGRIP1L, ARL13B, AHI1, TMEM67, OFD1, CC2D2A, and deletion analysis of NPHP1 showed no mutations. Although this study failed to identify a mutation in the patients tested, the co-occurrence of Joubert and Jeune syndromes is likely to represent a distinct entity caused by mutations in a yet to be discovered gene. The mechanisms by which certain organ systems are affected more than others in the spectrum of ciliary diseases remain largely unknown.
Ruxandra Bachmann-gagescu - One of the best experts on this subject based on the ideXlab platform.
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Loss-of-function of the ciliopathy protein CC2D2A disorganizes the vesicle fusion machinery at the periciliary membrane and indirectly affects Rab8-trafficking in zebrafish photoreceptors.
PLoS genetics, 2017Co-Authors: Irene Ojeda Naharros, Matthias Gesemann, José María Mateos, Gery Barmettler, Austin Forbes, Urs Ziegler, Stephan C.f. Neuhauss, Ruxandra Bachmann-gagescuAbstract:Ciliopathies are human disorders caused by dysfunction of primary cilia, ubiquitous organelles involved in transduction of environmental signals such as light sensation in photoreceptors. Concentration of signal detection proteins such as opsins in the ciliary membrane is achieved by RabGTPase-regulated polarized vesicle trafficking and by a selective barrier at the ciliary base, the transition zone (TZ). Dysfunction of the TZ protein CC2D2A causes Joubert/Meckel syndromes in humans and loss of ciliary protein localization in animal models, including opsins in retinal photoreceptors. The link between the TZ and upstream vesicle trafficking has been little explored to date. Moreover, the role of the small GTPase Rab8 in opsin-carrier vesicle (OCV) trafficking has been recently questioned in a mouse model. Using correlative light and electron microscopy and live imaging in zebrafish photoreceptors, we provide the first live characterization of Rab8-mediated trafficking in photoreceptors in vivo. Our results support a possibly redundant role for both Rab8a/b paralogs in OCV trafficking, based on co-localization of Rab8 and opsins in vesicular structures, and joint movement of Rab8-tagged particles with opsin. We further investigate the role of the TZ protein CC2D2A in Rab8-mediated trafficking using CC2D2A zebrafish mutants and identify a requirement for CC2D2A in the latest step of OCV trafficking, namely vesicle fusion. Progressive accumulation of opsin-containing vesicles in the apical portion of photoreceptors lacking CC2D2A is caused by disorganization of the vesicle fusion machinery at the periciliary membrane with mislocalization and loss of the t-SNAREs SNAP25 and Syntaxin3 and of the exocyst component Exoc4. We further observe secondary defects on upstream Rab8-trafficking with cytoplasmic accumulation of Rab8. Taken together, our results support participation of Rab8 in OCV trafficking and identify a novel role for the TZ protein CC2D2A in fusion of incoming ciliary-directed vesicles, through organization of the vesicle fusion machinery at the periciliary membrane.
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The Ciliopathy Protein CC2D2A Associates with NINL and Functions in RAB8-MICAL3-Regulated Vesicle Trafficking.
PLoS genetics, 2015Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Margo Dona, Lisette Hetterschijt, E.l.g.m. Tonnaer, Theo A. Peters, Erik De Vrieze, Dorus A. Mans, Sylvia E. C. Van Beersum, Heleen H. ArtsAbstract:Ciliopathies are a group of human disorders caused by dysfunction of primary cilia, ubiquitous microtubule-based organelles involved in transduction of extra-cellular signals to the cell. This function requires the concentration of receptors and channels in the ciliary membrane, which is achieved by complex trafficking mechanisms, in part controlled by the small GTPase RAB8, and by sorting at the transition zone located at the entrance of the ciliary compartment. Mutations in the transition zone gene CC2D2A cause the related Joubert and Meckel syndromes, two typical ciliopathies characterized by central nervous system malformations, and result in loss of ciliary localization of multiple proteins in various models. The precise mechanisms by which CC2D2A and other transition zone proteins control protein entrance into the cilium and how they are linked to vesicular trafficking of incoming cargo remain largely unknown. In this work, we identify the centrosomal protein NINL as a physical interaction partner of CC2D2A. NINL partially co-localizes with CC2D2A at the base of cilia and ninl knockdown in zebrafish leads to photoreceptor outer segment loss, mislocalization of opsins and vesicle accumulation, similar to CC2D2A-/- phenotypes. Moreover, partial ninl knockdown in CC2D2A-/- embryos enhances the retinal phenotype of the mutants, indicating a genetic interaction in vivo, for which an illustration is found in patients from a Joubert Syndrome cohort. Similar to zebrafish CC2D2A mutants, ninl morphants display altered Rab8a localization. Further exploration of the NINL-associated interactome identifies MICAL3, a protein known to interact with Rab8 and to play an important role in vesicle docking and fusion. Together, these data support a model where CC2D2A associates with NINL to provide a docking point for cilia-directed cargo vesicles, suggesting a mechanism by which transition zone proteins can control the protein content of the ciliary compartment.
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Genotype-Phenotype correlations in Joubert Syndrome in the Era of Next Generation Sequencing
Cilia, 2015Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Jennifer C Dempsey, Diana R. O’day, Christine R. Isabella, Brian J. O'roak, Jay Shendure, Ian A. Glass, Dan DohertyAbstract:Results Core JS diagnostic features (hypotonia, ataxia, cognitive dysfunction, oculo-motor apraxia) were present in >80% of individuals, while abnormal breathing pattern was reported in 60%. Frequently associated features included retinal dystrophy (31.4%), renal disease (20.9%), coloboma (17.7%), polydactyly (15.3%), liver fibrosis (15.2%) and encephalocele (8%). Liver fibrosis and coloboma were strongly associated with each other (Odds Ratio 7.0, 95% Confidence Interval = 3.0-13.2), while retinal dystrophy and renal disease were weakly associated (O.R. 2.2, 95%C. I. = 1.7-5.6). Additional clinical features included other brain abnormalities (n = 73), seizures (n = 49), cleft palate (n = 16), hearing loss (n = 14) and psychiatric problems (n = 45). The genetic cause was identified in 60% of families, with 5 genes accounting for the majority of patients (C5ORF42, CEP290, CC2D2A, AHI1, TMEM67). Bi-allelic causal mutations in B9D2 and C2CD3 were identified in 2 families each. Bi-allelic mutations in 2 different genes were identified in 4 families and heterozygous mutations (in addition to the causal mutation) were present in 62 individuals. Significant (p
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Live imaging of Rab8 trafficking defects in CC2D2A mutant zebrafish
Cilia, 2012Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Dan Doherty, A Forbes, Cecilia B. MoensAbstract:Primary cilia provide a means of regulating and concentrating receptors and other proteins essential for transmission of sensory signals or signaling pathways. Consequently, a thorough understanding of the sorting and trafficking mechanisms that allow appropriate protein delivery to the ciliary compartment is crucial to our understanding of ciliary function in development, homeostasis and disease. Recent work has demonstrated that ciliopathy proteins, such as CC2D2A, are localized to the transition zone at the base of the cilium and function to regulate protein entry into the ciliary compartment. Upstream of the cilium, small GTPases from the Rab family participate in controlling trafficking of ciliary-directed proteins. Here, we describe the relationship between the transition zone protein CC2D2A and Rab8 trafficking in photoreceptors. Detailed phenotypic analysis of a zebrafish CC2D2A mutant reveals typical ciliopathy phenotypes including cystic kidneys and abnormal photoreceptor outer segments. Mislocalization of opsins in mutant photoreceptors and massive accumulation of vesicles suggest a role for CC2D2A in vesicle trafficking. Partial rab8 knockdown enhances the photoreceptor phenotype of CC2D2A mutants. A fluorescently-tagged Rab8 transgene demonstrates a punctate localization pattern for Rab8 in photoreceptors that is disrupted in the absence of CC2D2A. Live imaging of Rab8 trafficking in zebrafish photoreceptors reveals complex and highly dynamic movements of Rab8 puncta towards different cellular destinations, including the outer segment and the synapse, which are differentially affected by loss of CC2D2A function.
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Genotype–phenotype correlation in CC2D2A -related Joubert syndrome reveals an association with ventriculomegaly and seizures
Journal of medical genetics, 2012Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Gisele E Ishak, Jennifer C Dempsey, Jonathan Adkins, Antonie D Kline, Diana R. O’day, Meral Gunay-aygun, Krzysztof Szczałuba, Loreto MartorellAbstract:Background Joubert syndrome (JS) is a ciliopathy characterised by a distinctive brain malformation (the ‘molar tooth sign’), developmental delay, abnormal eye movements and abnormal breathing pattern. Retinal dystrophy, cystic kidney disease, liver fibrosis and polydactyly are variably present, resulting in significant phenotypic heterogeneity and overlap with other ciliopathies. JS is also genetically heterogeneous, resulting from mutations in 13 genes. These factors render clinical/molecular diagnosis and management challenging. CC2D2A mutations are a relatively common cause of JS and also cause Meckel syndrome. The clinical consequences of CC2D2A mutations in patients with JS have been incompletely reported. Methods Subjects with JS from 209 families were evaluated to identify mutations in CC2D2A . Clinical and imaging features in subjects with CC2D2A mutations were compared with those in subjects without CC2D2A mutations and reports in the literature. Results 10 novel CC2D2A mutations in 20 subjects were identified; a summary is provided of all published CC2D2A mutations. Subjects with CC2D2A -related JS were more likely to have ventriculomegaly (p
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: 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: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.
Francesc R. Garcia-gonzalo - One of the best experts on this subject based on the ideXlab platform.
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A transition zone complex of ciliopathy proteins regulates ciliary composition
Cilia, 2012Co-Authors: Jeremy F. Reiter, Francesc R. Garcia-gonzalo, Kevin C. Corbit, William E. Dowdle, Laura E. YeeAbstract:We have identified a complex of proteins that form part of the transition zone, a region at the base of the cilium. This complex includes the three members of the Tectonic family, extracytosolic glycoproteins that interact with transmembrane components of the transition zone such as Tmem67, Tmem216, and Tmem231. These transmembrane proteins connect to an intracellular transition zone complex comprised of many known Joubert- and Meckel-associated proteins including CC2D2A, B9d1, B9d2, Mks1. Loss of components of this transition zone complex in mice compromise ciliogenesis in some tissues, and deregulate ciliary protein composition in others. In particular, the ciliary localization of Smoothened (Smo), a central component of the Hedgehog pathway, depends on this complex. As Smo functions at the cilium, many mouse transition zone mutants show deregulation of Hh signaling, resulting in ventralization of the neural tube and polydactyly. Defining the components of the transition zone has led to the identification of additional genes underlying Joubert and Meckel syndromes including Tctn1, Tctn2 and B9d2. We hypothesize that Joubert and Meckel syndromes are caused by transition zone dysfunction that disrupts intercellular signaling, leading to developmental defects.
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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: 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: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.
Ian G. Phelps - One of the best experts on this subject based on the ideXlab platform.
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The Ciliopathy Protein CC2D2A Associates with NINL and Functions in RAB8-MICAL3-Regulated Vesicle Trafficking.
PLoS genetics, 2015Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Margo Dona, Lisette Hetterschijt, E.l.g.m. Tonnaer, Theo A. Peters, Erik De Vrieze, Dorus A. Mans, Sylvia E. C. Van Beersum, Heleen H. ArtsAbstract:Ciliopathies are a group of human disorders caused by dysfunction of primary cilia, ubiquitous microtubule-based organelles involved in transduction of extra-cellular signals to the cell. This function requires the concentration of receptors and channels in the ciliary membrane, which is achieved by complex trafficking mechanisms, in part controlled by the small GTPase RAB8, and by sorting at the transition zone located at the entrance of the ciliary compartment. Mutations in the transition zone gene CC2D2A cause the related Joubert and Meckel syndromes, two typical ciliopathies characterized by central nervous system malformations, and result in loss of ciliary localization of multiple proteins in various models. The precise mechanisms by which CC2D2A and other transition zone proteins control protein entrance into the cilium and how they are linked to vesicular trafficking of incoming cargo remain largely unknown. In this work, we identify the centrosomal protein NINL as a physical interaction partner of CC2D2A. NINL partially co-localizes with CC2D2A at the base of cilia and ninl knockdown in zebrafish leads to photoreceptor outer segment loss, mislocalization of opsins and vesicle accumulation, similar to CC2D2A-/- phenotypes. Moreover, partial ninl knockdown in CC2D2A-/- embryos enhances the retinal phenotype of the mutants, indicating a genetic interaction in vivo, for which an illustration is found in patients from a Joubert Syndrome cohort. Similar to zebrafish CC2D2A mutants, ninl morphants display altered Rab8a localization. Further exploration of the NINL-associated interactome identifies MICAL3, a protein known to interact with Rab8 and to play an important role in vesicle docking and fusion. Together, these data support a model where CC2D2A associates with NINL to provide a docking point for cilia-directed cargo vesicles, suggesting a mechanism by which transition zone proteins can control the protein content of the ciliary compartment.
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Genotype-Phenotype correlations in Joubert Syndrome in the Era of Next Generation Sequencing
Cilia, 2015Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Jennifer C Dempsey, Diana R. O’day, Christine R. Isabella, Brian J. O'roak, Jay Shendure, Ian A. Glass, Dan DohertyAbstract:Results Core JS diagnostic features (hypotonia, ataxia, cognitive dysfunction, oculo-motor apraxia) were present in >80% of individuals, while abnormal breathing pattern was reported in 60%. Frequently associated features included retinal dystrophy (31.4%), renal disease (20.9%), coloboma (17.7%), polydactyly (15.3%), liver fibrosis (15.2%) and encephalocele (8%). Liver fibrosis and coloboma were strongly associated with each other (Odds Ratio 7.0, 95% Confidence Interval = 3.0-13.2), while retinal dystrophy and renal disease were weakly associated (O.R. 2.2, 95%C. I. = 1.7-5.6). Additional clinical features included other brain abnormalities (n = 73), seizures (n = 49), cleft palate (n = 16), hearing loss (n = 14) and psychiatric problems (n = 45). The genetic cause was identified in 60% of families, with 5 genes accounting for the majority of patients (C5ORF42, CEP290, CC2D2A, AHI1, TMEM67). Bi-allelic causal mutations in B9D2 and C2CD3 were identified in 2 families each. Bi-allelic mutations in 2 different genes were identified in 4 families and heterozygous mutations (in addition to the causal mutation) were present in 62 individuals. Significant (p
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Live imaging of Rab8 trafficking defects in CC2D2A mutant zebrafish
Cilia, 2012Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Dan Doherty, A Forbes, Cecilia B. MoensAbstract:Primary cilia provide a means of regulating and concentrating receptors and other proteins essential for transmission of sensory signals or signaling pathways. Consequently, a thorough understanding of the sorting and trafficking mechanisms that allow appropriate protein delivery to the ciliary compartment is crucial to our understanding of ciliary function in development, homeostasis and disease. Recent work has demonstrated that ciliopathy proteins, such as CC2D2A, are localized to the transition zone at the base of the cilium and function to regulate protein entry into the ciliary compartment. Upstream of the cilium, small GTPases from the Rab family participate in controlling trafficking of ciliary-directed proteins. Here, we describe the relationship between the transition zone protein CC2D2A and Rab8 trafficking in photoreceptors. Detailed phenotypic analysis of a zebrafish CC2D2A mutant reveals typical ciliopathy phenotypes including cystic kidneys and abnormal photoreceptor outer segments. Mislocalization of opsins in mutant photoreceptors and massive accumulation of vesicles suggest a role for CC2D2A in vesicle trafficking. Partial rab8 knockdown enhances the photoreceptor phenotype of CC2D2A mutants. A fluorescently-tagged Rab8 transgene demonstrates a punctate localization pattern for Rab8 in photoreceptors that is disrupted in the absence of CC2D2A. Live imaging of Rab8 trafficking in zebrafish photoreceptors reveals complex and highly dynamic movements of Rab8 puncta towards different cellular destinations, including the outer segment and the synapse, which are differentially affected by loss of CC2D2A function.
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genotype phenotype correlation in CC2D2A related joubert syndrome reveals an association with ventriculomegaly and seizures
Journal of Medical Genetics, 2012Co-Authors: Ruxandra Bachmanngagescu, Ian G. Phelps, Meral Gunayaygun, Gisele E Ishak, Jennifer C Dempsey, Jonathan Adkins, Diana R Oday, Antonie D Kline, Krzysztof Szczaluba, Loreto MartorellAbstract:Background Joubert syndrome (JS) is a ciliopathy characterised by a distinctive brain malformation (the ‘molar tooth sign’), developmental delay, abnormal eye movements and abnormal breathing pattern. Retinal dystrophy, cystic kidney disease, liver fibrosis and polydactyly are variably present, resulting in significant phenotypic heterogeneity and overlap with other ciliopathies. JS is also genetically heterogeneous, resulting from mutations in 13 genes. These factors render clinical/molecular diagnosis and management challenging. CC2D2A mutations are a relatively common cause of JS and also cause Meckel syndrome. The clinical consequences of CC2D2A mutations in patients with JS have been incompletely reported. Methods Subjects with JS from 209 families were evaluated to identify mutations in CC2D2A . Clinical and imaging features in subjects with CC2D2A mutations were compared with those in subjects without CC2D2A mutations and reports in the literature. Results 10 novel CC2D2A mutations in 20 subjects were identified; a summary is provided of all published CC2D2A mutations. Subjects with CC2D2A -related JS were more likely to have ventriculomegaly (p<0.0001) and seizures (p=0.024) than subjects without CC2D2A mutations. No mutation-specific genotype–phenotype correlations could be identified, but the findings confirm the observation that mutations that cause CC2D2A -related JS are predicted to be less deleterious than mutations that cause CC2D2A -related Meckel syndrome. Missense variants in the coiled-coil and C2 domains, as well as the C-terminal region, identify these regions as important for the biological mechanisms underlying JS. Conclusions CC2D2A testing should be prioritised in patients with JS and ventriculomegaly and/or seizures. Patients with CC2D2A -related JS should be monitored for hydrocephalus and seizures.
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Genotype–phenotype correlation in CC2D2A -related Joubert syndrome reveals an association with ventriculomegaly and seizures
Journal of medical genetics, 2012Co-Authors: Ruxandra Bachmann-gagescu, Ian G. Phelps, Gisele E Ishak, Jennifer C Dempsey, Jonathan Adkins, Antonie D Kline, Diana R. O’day, Meral Gunay-aygun, Krzysztof Szczałuba, Loreto MartorellAbstract:Background Joubert syndrome (JS) is a ciliopathy characterised by a distinctive brain malformation (the ‘molar tooth sign’), developmental delay, abnormal eye movements and abnormal breathing pattern. Retinal dystrophy, cystic kidney disease, liver fibrosis and polydactyly are variably present, resulting in significant phenotypic heterogeneity and overlap with other ciliopathies. JS is also genetically heterogeneous, resulting from mutations in 13 genes. These factors render clinical/molecular diagnosis and management challenging. CC2D2A mutations are a relatively common cause of JS and also cause Meckel syndrome. The clinical consequences of CC2D2A mutations in patients with JS have been incompletely reported. Methods Subjects with JS from 209 families were evaluated to identify mutations in CC2D2A . Clinical and imaging features in subjects with CC2D2A mutations were compared with those in subjects without CC2D2A mutations and reports in the literature. Results 10 novel CC2D2A mutations in 20 subjects were identified; a summary is provided of all published CC2D2A mutations. Subjects with CC2D2A -related JS were more likely to have ventriculomegaly (p