451
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The base of the cilium: roles for transition fibres and the transition zone in ciliary formation, maintenance and compartmentalization. EMBO Rep 2012; 13:608-18. [PMID: 22653444 DOI: 10.1038/embor.2012.73] [Citation(s) in RCA: 359] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 05/11/2012] [Indexed: 12/13/2022] Open
Abstract
Both the basal body and the microtubule-based axoneme it nucleates have evolutionarily conserved subdomains crucial for cilium biogenesis, function and maintenance. Here, we focus on two conspicuous but underappreciated regions of these structures that make membrane connections. One is the basal body distal end, which includes transition fibres of largely undefined composition that link to the base of the ciliary membrane. Transition fibres seem to serve as docking sites for intraflagellar transport particles, which move proteins within the ciliary compartment and are required for cilium biogenesis and sustained function. The other is the proximal-most region of the axoneme, termed the transition zone, which is characterized by Y-shaped linkers that span from the axoneme to the ciliary necklace on the membrane surface. The transition zone comprises a growing number of ciliopathy proteins that function as modular components of a ciliary gate. This gate, which forms early during ciliogenesis, might function in part by regulating intraflagellar transport. Together with a recently described septin ring diffusion barrier at the ciliary base, the transition fibres and transition zone deserve attention for their varied roles in forming functional ciliary compartments.
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452
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Servattalab S, Yildiz O, Khanna H. Tackling Primary Cilia Dysfunction in Photoreceptor Degenerative Diseases of the Eye. ACTA ACUST UNITED AC 2012; 1. [PMID: 24455751 DOI: 10.4172/2324-8599.1000e101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Sarah Servattalab
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Ozge Yildiz
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Hemant Khanna
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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453
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Eckmann-Scholz C, Jonat W, Zerres K, Ortiz-Brüchle N. Earliest ultrasound findings and description of splicing mutations in Meckel-Gruber syndrome. Arch Gynecol Obstet 2012; 286:917-21. [PMID: 22699515 DOI: 10.1007/s00404-012-2411-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 05/31/2012] [Indexed: 12/21/2022]
Abstract
OBJECTIVE To describe early ultrasound findings in Meckel-Gruber syndrome (MKS) in first and second trimester of three families, detailed ultrasound findings have been documented in addition to pathoanatomical findings and results of DNA studies. A splice site mutation in the MKS4 gene could be detected. Clinical management accounting risk assessment for future pregnancies is discussed and early ultrasound markers in MKS are described. METHODS All cases were examined in a tertiary center for prenatal diagnosis by ultrasound. Necroscopy confirmed the clinical diagnosis. Fetal DNA analysis was accomplished in a reference center for MKS. In addition, ultrasound findings in early pregnancy of two further cases are described. RESULTS Three couples presented with pregnancies complicated by MKS. The earliest diagnosis was suspected in 11 + 6 weeks of gestation and was confirmed in 13 + 0 weeks by ultrasound revealing a large occipital encephalocele and polycystic kidneys. Another case with recurrent MKS in two consecutive pregnancies was diagnosed in 20 weeks and 14 weeks of gestation, respectively. Here a close molecular genetic follow-up was performed leading to the detection of two mutations in the MKS4 gene in both fetuses. The third case was diagnosed in 15 weeks of gestation. Ultrasound findings in all pregnancies were doubtless and autopsies confirmed the diagnosis. CONCLUSION Detection of MKS is already possible in the first trimester. Knowledge of the underlying genetic defect helps counseling the couples with recurrence of MKS and chorionic villi sampling in the first trimester of pregnancy can be offered.
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Affiliation(s)
- Christel Eckmann-Scholz
- Department of Gynecology and Obstetrics, University Hospital Schleswig-Holstein, Campus Kiel and Christian-Albrechts-University Kiel, Arnold-Heller-Straße 3, 24105 Kiel, Germany.
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454
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Christopher KJ, Wang B, Kong Y, Weatherbee SD. Forward genetics uncovers Transmembrane protein 107 as a novel factor required for ciliogenesis and Sonic hedgehog signaling. Dev Biol 2012; 368:382-92. [PMID: 22698544 DOI: 10.1016/j.ydbio.2012.06.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 06/01/2012] [Accepted: 06/04/2012] [Indexed: 12/28/2022]
Abstract
Cilia are dynamic organelles that are essential for a vast array of developmental patterning events, including left-right specification, skeletal formation, neural development, and organogenesis. Despite recent advances in understanding cilia form and function, many key ciliogenesis components have yet to be identified. By using a forward genetics approach, we isolated a novel mutant allele (schlei) of the mouse Transmembrane protein 107 (Tmem107) gene, which we show here is critical for cilia formation and embryonic patterning. Tmem107 is required for normal Sonic hedgehog (Shh) signaling in the neural tube and acts in combination with Gli2 and Gli3 to pattern ventral and intermediate neuronal cell types. schlei mutants also form extra digits, and we demonstrate that Tmem107 acts in the Shh pathway to determine digit number, but not identity, by regulating a subset of Shh target genes. Phenotypically, schlei mutants share several features with other cilia mutants; however, spatial restriction of mutant phenotypes and lack of left-right patterning defects in schlei animals suggest differential requirements for Tmem107 in cilia formation in distinct tissues. Also, in contrast to mutants with complete loss of cilia, schlei mutants retain some function of both Gli activator and repressor forms. Together, these studies identify a previously unknown regulator of ciliogenesis and provide insight into how ciliary factors affect Shh signaling and cilia biogenesis in distinct tissues.
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MESH Headings
- Amino Acid Sequence
- Animals
- Body Patterning/genetics
- Cells, Cultured
- Cilia/genetics
- Embryo, Mammalian/cytology
- Embryo, Mammalian/embryology
- Embryo, Mammalian/metabolism
- Extremities/embryology
- Female
- Gene Expression Regulation, Developmental
- Hedgehog Proteins/genetics
- In Situ Hybridization
- Kruppel-Like Transcription Factors/genetics
- Male
- Membrane Proteins/genetics
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Mutant Strains
- Microscopy, Electron, Scanning
- Molecular Sequence Data
- Mutation
- Nerve Tissue Proteins/genetics
- Neural Tube/embryology
- Neural Tube/metabolism
- Neural Tube/ultrastructure
- Sequence Homology, Amino Acid
- Signal Transduction/genetics
- Zinc Finger Protein Gli2
- Zinc Finger Protein Gli3
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455
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Gate D, Danielpour M, Levy R, Breunig JJ, Town T. Basic biology and mechanisms of neural ciliogenesis and the B9 family. Mol Neurobiol 2012; 45:564-70. [PMID: 22644387 DOI: 10.1007/s12035-012-8276-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 05/07/2012] [Indexed: 11/28/2022]
Abstract
Although the discovery of cilia is one of the earliest in cell biology, the past two decades have witnessed an explosion of new insight into these enigmatic organelles. While long believed to be vestigial, cilia have recently moved into the spotlight as key players in multiple cellular processes, including brain development and homeostasis. This review focuses on the rapidly expanding basic biology of neural cilia, with special emphasis on the newly emerging B9 family of proteins. In particular, recent findings have identified a critical role for the B9 complex in a network of protein interactions that take place at the ciliary transition zone (TZ). We describe the essential role of these protein complexes in signaling cascades that require primary (nonmotile) cilia, including the sonic hedgehog pathway. Loss or dysfunction of ciliary trafficking and TZ function are linked to a number of neurologic diseases, which we propose to classify as neural ciliopathies. When taken together, the studies reviewed herein point to critical roles played by neural cilia, both in normal physiology and in disease.
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Affiliation(s)
- David Gate
- Department of Biomedical Sciences and Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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456
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Davis EE, Katsanis N. The ciliopathies: a transitional model into systems biology of human genetic disease. Curr Opin Genet Dev 2012; 22:290-303. [PMID: 22632799 DOI: 10.1016/j.gde.2012.04.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 04/24/2012] [Accepted: 04/24/2012] [Indexed: 01/19/2023]
Abstract
The last decade has witnessed an explosion in the identification of genes, mutations in which appear sufficient to cause clinical phenotypes in humans. This is especially true for disorders of ciliary dysfunction in which an excess of 50 causal loci are now known; this discovery was driven partly by an improved understanding of the protein composition of the cilium and the co-occurrence of clinical phenotypes associated with ciliary dysfunction. Despite this progress, the fundamental challenge of predicting phenotype and or clinical progression based on single locus information remains unsolved. Here, we explore how the combinatorial knowledge of allele quality and quantity, an improved understanding of the biological composition of the primary cilium, and the expanded appreciation of the subcellular roles of this organelle can be synthesized to generate improved models that can explain both causality but also variable penetrance and expressivity.
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Affiliation(s)
- Erica E Davis
- Center for Human Disease Modeling, Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA
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457
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Anand M, Khanna H. Ciliary transition zone (TZ) proteins RPGR and CEP290: role in photoreceptor cilia and degenerative diseases. Expert Opin Ther Targets 2012; 16:541-51. [PMID: 22563985 DOI: 10.1517/14728222.2012.680956] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
INTRODUCTION Primary cilia are microtubule-based extensions of the plasma membrane in nearly all cell types. In vertebrate photoreceptors, the sensory cilium develops as outer segment (OS) that contains the photopigment rhodopsin and other proteins necessary for phototransduction. The distinct composition of proteins and lipids in the OS membrane is maintained by the selective barrier located at the border between the basal body and the ciliary compartment, called the transition zone (TZ). AREAS COVERED In this review, we will discuss the identification and function of two ciliary TZ proteins, RPGR (retinitis pigmentosa GTPase regulator) and CEP290. Mutations in these proteins account for a majority of retinopathies due to ciliary dysfunction. We will also discuss the potential of such information in designing therapeutic approaches to treat cilia-dependent photoreceptor degenerative diseases. EXPERT OPINION RPGR and CEP290 perform overlapping yet distinct functions in regulating trafficking of cargo via the TZ of photoreceptors. While RPGR modulates the trafficking by acting as a GEF for the small GTPase RAB8A, CEP290 may be involved in maintaining the polarized distribution of proteins in the OS by modulating intracellular levels of selected proteins involved in inhibiting OS formation.
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Affiliation(s)
- Manisha Anand
- University of Massachusetts Medical School, Department of Ophthalmology, 381 Plantation Street, Biotech 5, Suite 250, Worcester, MA 01605, USA
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458
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Joubert syndrome: brain and spinal cord malformations in genotyped cases and implications for neurodevelopmental functions of primary cilia. Acta Neuropathol 2012; 123:695-709. [PMID: 22331178 DOI: 10.1007/s00401-012-0951-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 01/25/2012] [Accepted: 01/27/2012] [Indexed: 12/12/2022]
Abstract
Joubert syndrome (JS) is an autosomal recessive ciliopathy characterized by hypotonia, ataxia, abnormal eye movements, and intellectual disability. The brain is malformed, with severe vermian hypoplasia, fourth ventriculomegaly, and "molar tooth" appearance of the cerebral and superior cerebellar peduncles visible as consistent features on neuroimaging. Neuropathological studies, though few, suggest that several other brain and spinal cord structures, such as the dorsal cervicomedullary junction, may also be affected in at least some patients. Genetically, JS is heterogeneous, with mutations in 13 genes accounting for approximately 50% of patients. Here, we compare neuropathologic findings in five subjects with JS, including four with defined mutations in OFD1 (2 siblings), RPGRIP1L, or TCTN2. Characteristic findings in all JS genotypes included vermian hypoplasia, fragmented dentate and spinal trigeminal nuclei, hypoplastic pontine and inferior olivary nuclei, and nondecussation of corticospinal tracts. Other common findings, seen in multiple genotypes but not all subjects, were dorsal cervicomedullary heterotopia, nondecussation of superior cerebellar peduncles, enlarged arcuate nuclei, hypoplastic reticular formation, hypoplastic medial lemnisci, and dorsal spinal cord disorganization. Thus, while JS exhibits significant neuropathologic as well as genetic heterogeneity, no genotype-phenotype correlations are apparent as yet. Our findings suggest that primary cilia are important for neural patterning, progenitor proliferation, cell migration, and axon guidance in the developing human brain and spinal cord.
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459
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460
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Hsiao YC, Tuz K, Ferland RJ. Trafficking in and to the primary cilium. Cilia 2012; 1:4. [PMID: 23351793 PMCID: PMC3541539 DOI: 10.1186/2046-2530-1-4] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 04/25/2012] [Indexed: 01/08/2023] Open
Abstract
Polarized vesicle trafficking is mediated by small GTPase proteins, such as Rabs and Arls/Arfs. These proteins have essential roles in maintaining normal cellular function, in part, through regulating intracellular trafficking. Moreover, these families of proteins have recently been implicated in the formation and function of the primary cilium. The primary cilium, which is found on almost every cell type in vertebrates, is an organelle that protrudes from the surface of the cell and functions as a signaling center. Interestingly, it has recently been linked to a variety of human diseases, collectively referred to as ciliopathies. The primary cilium has an exceptionally high density of receptors on its membrane that are important for sensing and transducing extracellular stimuli. Moreover, the primary cilium serves as a separate cellular compartment from the cytosol, providing for unique spatial and temporal regulation of signaling molecules to initiate downstream events. Thus, functional primary cilia are essential for normal signal transduction. Rabs and Arls/Arfs play critical roles in early cilia formation but are also needed for maintenance of ciliary function through their coordination with intraflagellar transport (IFT), a specialized trafficking system in primary cilia. IFT in cilia is pivotal for the proper movement of proteins into and out of this highly regulated organelle. In this review article, we explore the involvement of polarized vesicular trafficking in cilia formation and function, and discuss how defects in these processes could subsequently lead to the abnormalities observed in ciliopathies.
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Affiliation(s)
- Yi-Chun Hsiao
- Department of Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.,Albany Medical College, Center for Neuropharmacology and Neuroscience, Albany, NY 12208, USA
| | - Karina Tuz
- Albany Medical College, Center for Neuropharmacology and Neuroscience, Albany, NY 12208, USA
| | - Russell J Ferland
- Albany Medical College, Center for Neuropharmacology and Neuroscience, Albany, NY 12208, USA.,Department of Neurology, Albany Medical College, Albany, NY 12208, USA
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461
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Srour M, Schwartzentruber J, Hamdan FF, Ospina LH, Patry L, Labuda D, Massicotte C, Dobrzeniecka S, Capo-Chichi JM, Papillon-Cavanagh S, Samuels ME, Boycott KM, Shevell MI, Laframboise R, Désilets V, Maranda B, Rouleau GA, Majewski J, Michaud JL. Mutations in C5ORF42 cause Joubert syndrome in the French Canadian population. Am J Hum Genet 2012; 90:693-700. [PMID: 22425360 DOI: 10.1016/j.ajhg.2012.02.011] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 01/23/2012] [Accepted: 02/13/2012] [Indexed: 11/29/2022] Open
Abstract
Joubert syndrome (JBTS) is an autosomal-recessive disorder characterized by a distinctive mid-hindbrain malformation, developmental delay with hypotonia, ocular-motor apraxia, and breathing abnormalities. Although JBTS was first described more than 40 years ago in French Canadian siblings, the causal mutations have not yet been identified in this family nor in most French Canadian individuals subsequently described. We ascertained a cluster of 16 JBTS-affected individuals from 11 families living in the Lower St. Lawrence region. SNP genotyping excluded the presence of a common homozygous mutation that would explain the clustering of these individuals. Exome sequencing performed on 15 subjects showed that nine affected individuals from seven families (including the original JBTS family) carried rare compound-heterozygous mutations in C5ORF42. Two missense variants (c.4006C>T [p.Arg1336Trp] and c.4690G>A [p.Ala1564Thr]) and a splicing mutation (c.7400+1G>A), which causes exon skipping, were found in multiple subjects that were not known to be related, whereas three other truncating mutations (c.6407del [p.Pro2136Hisfs*31], c.4804C>T [p.Arg1602*], and c.7477C>T [p.Arg2493*]) were identified in single individuals. None of the unaffected first-degree relatives were compound heterozygous for these mutations. Moreover, none of the six putative mutations were detected among 477 French Canadian controls. Our data suggest that mutations in C5ORF42 explain a large portion of French Canadian individuals with JBTS.
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Affiliation(s)
- Myriam Srour
- Centre of Excellence in Neurosciences, Université de Montréal and Sainte-Justine Hospital Research Center, Montréal, QC, Canada
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462
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Abstract
Through the combined study of model organisms, cell biology, cell signaling and medical genetics we have significantly increased our understanding of the structure and functions of the vertebrate cilium. This ancient organelle has now emerged as a crucial component of certain signaling and sensory perception pathways in both developmental and homeostatic contexts. Here, we provide a snapshot of the structure, function and distribution of the vertebrate cilium and of the pathologies that are associated with its dysfunction.
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Affiliation(s)
- Edwin C Oh
- Center for Human Disease Modeling, Department of Cell Biology, Duke University, Durham NC 27710, USA.
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463
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Czarnecki PG, Shah JV. The ciliary transition zone: from morphology and molecules to medicine. Trends Cell Biol 2012; 22:201-10. [PMID: 22401885 DOI: 10.1016/j.tcb.2012.02.001] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 01/28/2012] [Accepted: 02/01/2012] [Indexed: 11/29/2022]
Abstract
Researchers from various disciplines, including cell and developmental biology, genetics and molecular medicine, have revealed an exceptional diversity of cellular functions that are mediated by cilia-dependent mechanisms. Recent studies have directed our attention to proteins that localize to the ciliary transition zone (TZ), a small evolutionarily conserved subcompartment that is situated between the basal body (BB) and the more distal ciliary axoneme. These reports shed light on the roles of TZ proteins in ciliogenesis, ciliary protein homeostasis and specification of ciliary signaling, and pave the way for understanding their contribution to human ciliopathies. In this review, we describe the interplay of multimeric protein complexes at the TZ, integrating morphological, genetic and proteomic data towards an account of TZ function in ciliary physiology.
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Affiliation(s)
- Peter G Czarnecki
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
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464
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Carroll CE, Marada S, Stewart DP, Ouyang JX, Ogden SK. The extracellular loops of Smoothened play a regulatory role in control of Hedgehog pathway activation. Development 2012; 139:612-21. [PMID: 22223683 DOI: 10.1242/dev.075614] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Hedgehog (Hh) signaling pathway plays an instructional role during development, and is frequently activated in cancer. Ligand-induced pathway activation requires signaling by the transmembrane protein Smoothened (Smo), a member of the G-protein-coupled receptor (GPCR) superfamily. The extracellular (EC) loops of canonical GPCRs harbor cysteine residues that engage in disulfide bonds, affecting active and inactive signaling states through regulating receptor conformation, dimerization and/or ligand binding. Although a functional importance for cysteines localized to the N-terminal extracellular cysteine-rich domain has been described, a functional role for a set of conserved cysteines in the EC loops of Smo has not yet been established. In this study, we mutated each of the conserved EC cysteines, and tested for effects on Hh signal transduction. Cysteine mutagenesis reveals that previously uncharacterized functional roles exist for Smo EC1 and EC2. We provide in vitro and in vivo evidence that EC1 cysteine mutation induces significant Hh-independent Smo signaling, triggering a level of pathway activation similar to that of a maximal Hh response in Drosophila and mammalian systems. Furthermore, we show that a single amino acid change in EC2 attenuates Hh-induced Smo signaling, whereas deletion of the central region of EC2 renders Smo fully active, suggesting that the conformation of EC2 is crucial for regulated Smo activity. Taken together, these findings are consistent with loop cysteines engaging in disulfide bonds that facilitate a Smo conformation that is silent in the absence of Hh, but can transition to a fully active state in response to ligand.
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Affiliation(s)
- Candace E Carroll
- Department of Biochemistry, St Jude Children's Research Hospital, 262 Danny Thomas Place, MS 340, Memphis, TN 38105, USA
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465
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Warburton-Pitt SRF, Jauregui AR, Li C, Wang J, Leroux MR, Barr MM. Ciliogenesis in Caenorhabditis elegans requires genetic interactions between ciliary middle segment localized NPHP-2 (inversin) and transition zone-associated proteins. J Cell Sci 2012; 125:2592-603. [PMID: 22393243 DOI: 10.1242/jcs.095539] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The cystic kidney diseases nephronophthisis (NPHP), Meckel-Gruber syndrome (MKS) and Joubert syndrome (JBTS) share an underlying etiology of dysfunctional cilia. Patients diagnosed with NPHP type II have mutations in the gene INVS (also known as NPHP2), which encodes inversin, a cilia localizing protein. Here, we show that the C. elegans inversin ortholog, NPHP-2, localizes to the middle segment of sensory cilia and that nphp-2 is partially redundant with nphp-1 and nphp-4 (orthologs of human NPHP1 and NPHP4, respectively) for cilia placement within the head and tail sensilla. nphp-2 also genetically interacts with MKS ciliopathy gene orthologs, including mks-1, mks-3, mks-6, mksr-1 and mksr-2, in a sensilla-dependent manner to control cilia formation and placement. However, nphp-2 is not required for correct localization of the NPHP- and MKS-encoded ciliary transition zone proteins or for intraflagellar transport (IFT). We conclude that INVS/NPHP2 is conserved in C. elegans and that nphp-2 plays an important role in C. elegans cilia by acting as a modifier of the NPHP and MKS pathways to control cilia formation and development.
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466
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A size-exclusion permeability barrier and nucleoporins characterize a ciliary pore complex that regulates transport into cilia. Nat Cell Biol 2012; 14:431-7. [PMID: 22388888 PMCID: PMC3319646 DOI: 10.1038/ncb2450] [Citation(s) in RCA: 226] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 02/01/2012] [Indexed: 12/14/2022]
Abstract
The cilium is a microtubule-based organelle that contains a unique complement of proteins for cell motility and signaling functions. Entry into the ciliary compartment is proposed to be regulated at the base of the cilium 1. Recent work demonstrated that components of the nuclear import machinery, including the RanGTPase and importins, regulate ciliary entry 2–4. We hypothesized that the ciliary base contains a ciliary pore complex (CPC) whose molecular nature and selective mechanism are similar to the nuclear pore complex (NPC). By microinjecting fluorescently-labeled dextrans and recombinant proteins of various sizes, we characterize a size-dependent diffusion barrier for the entry of cytoplasmic molecules into primary cilia in mammalian cells. We demonstrate that nucleoporins localize to the base of primary and motile cilia and that microinjection of nucleoporin function-blocking reagents blocks the ciliary entry of kinesin-2 KIF17 motors. Together, this work demonstrates that the physical and molecular nature of the CPC is similar to the NPC, and further extends functional parallels between nuclear and ciliary import.
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467
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Collin GB, Won J, Hicks WL, Cook SA, Nishina PM, Naggert JK. Meckelin is necessary for photoreceptor intraciliary transport and outer segment morphogenesis. Invest Ophthalmol Vis Sci 2012; 53:967-74. [PMID: 22247471 PMCID: PMC3317434 DOI: 10.1167/iovs.11-8766] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 12/21/2011] [Accepted: 12/30/2011] [Indexed: 01/16/2023] Open
Abstract
PURPOSE Cilia, complex structures found ubiquitously in most vertebrate cells, serve a variety of functions ranging from cell and fluid movement, cell signaling, tissue homeostasis, to sensory perception. Meckelin is a component of ciliary and cell membranes and is encoded by Tmem67 (Mks3). In this study, the retinal morphology and ciliary function in a mouse model for Meckel Syndrome Type 3 (MKS3) throughout the course of photoreceptor development was examined. METHODS To study the effects of a disruption in the Mks3 gene on the retina, the authors introduced a functional allele of Pde6b into B6C3Fe a/a-bpck/J mice and evaluated their retinas by ophthalmoscopic, histologic, and ultrastructural examination. In addition, immunofluorescence microscopy was used to assess protein trafficking through the connecting cilium and to examine the localization of ciliary and synaptic proteins in Tmem67(bpck) mice and controls. RESULTS Photoreceptors degenerate early and rapidly in bpck/bpck mutant mice. In addition, phototransduction proteins, such as rhodopsin, arrestin, and transducin, are mislocalized. Ultrastructural examination of photoreceptors reveal morphologically intact connecting cilia but dysmorphic and misoriented outer segment (OS) discs, at the earliest time point examined. CONCLUSIONS These findings underscore the important role for meckelin in intraciliary transport of phototransduction molecules and their effects on subsequent OS morphogenesis and maintenance.
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468
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Poretti A, Vitiello G, Hennekam RCM, Arrigoni F, Bertini E, Borgatti R, Brancati F, D'Arrigo S, Faravelli F, Giordano L, Huisman TAGM, Iannicelli M, Kluger G, Kyllerman M, Landgren M, Lees MM, Pinelli L, Romaniello R, Scheer I, Schwarz CE, Spiegel R, Tibussek D, Valente EM, Boltshauser E. Delineation and diagnostic criteria of Oral-Facial-Digital Syndrome type VI. Orphanet J Rare Dis 2012; 7:4. [PMID: 22236771 PMCID: PMC3313869 DOI: 10.1186/1750-1172-7-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 01/11/2012] [Indexed: 01/20/2023] Open
Abstract
Oral-Facial-Digital Syndrome type VI (OFD VI) represents a rare phenotypic subtype of Joubert syndrome and related disorders (JSRD). In the original report polydactyly, oral findings, intellectual disability, and absence of the cerebellar vermis at post-mortem characterized the syndrome. Subsequently, the molar tooth sign (MTS) has been found in patients with OFD VI, prompting the inclusion of OFD VI in JSRD. We studied the clinical, neurodevelopmental, neuroimaging, and genetic findings in a cohort of 16 patients with OFD VI. We derived the following inclusion criteria from the literature: 1) MTS and one oral finding and polydactyly, or 2) MTS and more than one typical oral finding. The OFD VI neuroimaging pattern was found to be more severe than in other JSRD subgroups and includes severe hypoplasia of the cerebellar vermis, hypoplastic and dysplastic cerebellar hemispheres, marked enlargement of the posterior fossa, increased retrocerebellar collection of cerebrospinal fluid, abnormal brainstem, and frequently supratentorial abnormalities that occasionally include characteristic hypothalamic hamartomas. Additionally, two new JSRD neuroimaging findings (ascending superior cerebellar peduncles and fused thalami) have been identified. Tongue hamartomas, additional frenula, upper lip notch, and mesoaxial polydactyly are specific findings in OFD VI, while cleft lip/palate and other types of polydactyly of hands and feet are not specific. Involvement of other organs may include ocular findings, particularly colobomas. The majority of the patients have absent motor development and profound cognitive impairment. In OFD VI, normal cognitive functions are possible, but exceptional. Sequencing of known JSRD genes in most patients failed to detect pathogenetic mutations, therefore the genetic basis of OFD VI remains unknown. Compared with other JSRD subgroups, the neurological findings and impairment of motor development and cognitive functions in OFD VI are significantly worse, suggesting a correlation with the more severe neuroimaging findings. Based on the literature and this study we suggest as diagnostic criteria for OFD VI: MTS and one or more of the following: 1) tongue hamartoma(s) and/or additional frenula and/or upper lip notch; 2) mesoaxial polydactyly of one or more hands or feet; 3) hypothalamic hamartoma.
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Affiliation(s)
- Andrea Poretti
- Department of Pediatric Neurology, University Children's Hospital of Zurich, Switzerland
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469
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Silva DA, Huang X, Behal RH, Cole DG, Qin H. The RABL5 homolog IFT22 regulates the cellular pool size and the amount of IFT particles partitioned to the flagellar compartment in Chlamydomonas reinhardtii. Cytoskeleton (Hoboken) 2012; 69:33-48. [PMID: 22076686 DOI: 10.1002/cm.20546] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 10/28/2011] [Indexed: 12/14/2022]
Abstract
Cilia and flagella, sensory and motile structures protruding from the cell body, rely on the continuous bidirectional traffic of intraflagellar transport (IFT) particles to ferry flagellar precursors into flagella for assembly. Cells synthesize a large pool of IFT particle proteins in the cell body, but only a small portion engages in active transport within the flagella at any given time. The atypical small G protein Rab-like 5 (RABL5) has been shown to move in an IFT-like manner in the flagella, but its function in ciliogenesis is controversial. In this report, we demonstrate that IFT22, the Chlamydomonas reinhardtii homolog of RABL5, is a bona fide IFT particle complex B subunit. Although the amount of IFT22 remains unaffected by depletion of either complex A or B, depletion of IFT22 leads to a smaller pool of both complex A and B. Strikingly, the smaller cellular pool of IFT particles does not lead to a reduced distribution of IFT particles to flagella. Instead, the amount of IFT particle proteins, including IFT22 itself, increase in the flagella. Moreover, cells over-expressing IFT22 also accumulate IFT particles in their flagella. Taken together, these data indicate that, in C. reinhardtii, IFT22 controls the cellular levels of both complex A and B, thus plays a critical role in determining the cellular availability of IFT particles. In addition, although IFT22 may not directly carry any precursors for flagellar assembly, it controls how many IFT particles participate in ferrying precursors into flagella.
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Affiliation(s)
- David A Silva
- Department of Biology, Texas A&M University, College Station, Texas 77843, USA
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470
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Drummond IA. Cilia functions in development. Curr Opin Cell Biol 2012; 24:24-30. [PMID: 22226236 DOI: 10.1016/j.ceb.2011.12.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 12/12/2011] [Accepted: 12/13/2011] [Indexed: 11/28/2022]
Abstract
Recent advances in developmental genetics and human disease gene cloning have highlighted the essential roles played by cilia in developmental cell fate decisions, left-right asymmetry, and the pathology of human congenital disorders. Hedgehog signaling in sensory cilia illustrates the importance of trafficking receptors to the cilia membrane (Patched and Smoothened) and the concept of cilia 'gatekeepers' that restrict entry and egress of cilia proteins (Suppressor of fused: Gli complexes). Cilia-driven fluid flow in the embryonic node highlights the role of motile cilia in both generation and detection of mechanical signals in development. In this brief review I select examples of recent studies that have clarified and consolidated our understanding of the role of cilia in development.
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Affiliation(s)
- Iain A Drummond
- Nephrology Division, Massachusetts General Hospital and Department of Genetics, Harvard Medical School, 149, 13th Street, Charlestown, MA 02129, United States.
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471
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Deane JA, Ricardo SD. Emerging roles for renal primary cilia in epithelial repair. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 293:169-93. [PMID: 22251562 DOI: 10.1016/b978-0-12-394304-0.00011-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Primary cilia are microscopic sensory antennae that cells in many vertebrate tissues use to gather information about their environment. In the kidney, primary cilia sense urine flow and are essential for the maintenance of epithelial architecture. Defects of this organelle cause the cystic kidney disease characterized by epithelial abnormalities. These findings link primary cilia to the regulation of epithelial differentiation and proliferation, processes that must be precisely controlled during epithelial repair in the kidney. Here, we consider likely roles for primary cilium-based signaling during responses to renal injury and ensuing epithelial repair processes.
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Affiliation(s)
- James A Deane
- Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton, Victoria, Australia
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472
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Aubusson-Fleury A, Lemullois M, de Loubresse NG, Laligné C, Cohen J, Rosnet O, Jerka-Dziadosz M, Beisson J, Koll F. FOR20, a conserved centrosomal protein, is required for assembly of the transition zone and basal body docking at the cell surface. J Cell Sci 2012; 125:4395-404. [DOI: 10.1242/jcs.108639] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Within the FOP family of centrosomal proteins, the conserved FOR20 protein has been implicated in the control of primary cilium assembly in human cells. To ascertain its role in ciliogenesis, we have investigated the function of its ortholog, PtFOR20p, in a multiciliated unicellular organism, Paramecium. By a combined functional and cytological analysis, we found that PtFOR20p specifically localizes at basal bodies and is required to build the transition zone, a prerequisite to their maturation and docking at the cell surface, hence to ciliogenesis. We also found that PtCen2p (one of the two basal body specific centrins, ortholog of HsCen2) is required to recruit PtFOR20p at the developing basal body and to control its length. In contrast, the other basal body specific centrin, PtCen3p, is not needed for assembly of the transition zone, but is required downstream, for basal body docking. Comparison of the structural defects induced by depletion of PtFOR20p, PtCen2p or PtCen3p respectively illustrates the dual role of the transition zone in the biogenesis of the basal body and in cilium assembly. The multiple potential roles of the transition zone during basal body biogenesis and the evolutionary conserved function of the FOP proteins in microtubule membrane interactions are discussed.
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473
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A ciliopathy complex at the transition zone protects the cilia as a privileged membrane domain. Nat Cell Biol 2011; 14:61-72. [PMID: 22179047 DOI: 10.1038/ncb2410] [Citation(s) in RCA: 262] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 11/23/2011] [Indexed: 12/21/2022]
Abstract
Using RNAi screening, proteomics, cell biological and mouse genetics approaches, we have identified a complex of nine proteins, seven of which are disrupted in human ciliopathies. A transmembrane component, TMEM231, localizes to the basal body before and independently of intraflagellar transport in a Septin 2 (Sept2)-regulated fashion. The localizations of TMEM231, B9D1 (B9 domain-containing protein 1) and CC2D2A (coiled-coil and C2 domain-containing protein 2A) at the transition zone are dependent on one another and on Sept2. Disruption of the complex in vitro causes a reduction in cilia formation and a loss of signalling receptors from the remaining cilia. Mouse knockouts of B9D1 and TMEM231 have identical defects in Sonic hedgehog (Shh) signalling and ciliogenesis. Strikingly, disruption of the complex increases the rate of diffusion into the ciliary membrane and the amount of plasma-membrane protein in the cilia. The complex that we have described is essential for normal cilia function and acts as a diffusion barrier to maintain the cilia membrane as a compartmentalized signalling organelle.
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474
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Avasthi P, Marshall WF. Stages of ciliogenesis and regulation of ciliary length. Differentiation 2011; 83:S30-42. [PMID: 22178116 DOI: 10.1016/j.diff.2011.11.015] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 11/30/2011] [Accepted: 11/30/2011] [Indexed: 12/25/2022]
Abstract
Cilia and flagella are highly conserved eukaryotic microtubule-based organelles that protrude from the surface of most mammalian cells. These structures require large protein complexes and motors for distal addition of tubulin and extension of the ciliary membrane. In order for ciliogenesis to occur, coordination of many processes must take place. An intricate concert of cell cycle regulation, vesicular trafficking, and ciliary extension must all play out with accurate timing to produce a cilium. Here, we review the stages of ciliogenesis as well as regulation of the length of the assembled cilium. Regulation of ciliogenesis during cell cycle progression centers on centrioles, from which cilia extend upon maturation into basal bodies. Centriole maturation involves a shift from roles in cell division to cilium nucleation via migration to the cell surface and docking at the plasma membrane. Docking is dependent on a variety of proteinaceous structures, termed distal appendages, acquired by the mother centriole. Ciliary elongation by the process of intraflagellar transport (IFT) ensues. Direct modification of ciliary structures, as well as modulation of signal transduction pathways, play a role in maintenance of the cilium. All of these stages are tightly regulated to produce a cilium of the right size at the right time. Finally, we discuss the implications of abnormal ciliogenesis and ciliary length control in human disease as well as some open questions.
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Affiliation(s)
- Prachee Avasthi
- Department of Biochemistry & Biophysics, University of California GH-N372F Genentech Hall, Box 2200, UCSF, 600 16th St. San Francisco, CA 94158, USA
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475
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The ciliary transitional zone and nephrocystins. Differentiation 2011; 83:S91-6. [PMID: 22169048 DOI: 10.1016/j.diff.2011.11.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 11/10/2011] [Accepted: 11/16/2011] [Indexed: 01/13/2023]
Abstract
Loss of cilia and ciliary protein causes various abnormalities (called ciliopathy), including situs inversus, renal cystic diseases, polydactyly and dysgenesis of the nervous system. Renal cystic diseases are the most frequently observed symptoms in ciliopathies. Cilia are microtubule-based organelles with the following regions: a ciliary tip, shaft, transitional zone and basal body/mother centriole. Joubert syndrome (JBTS), Meckel Gruber syndrome (MKS) and Nephronophthisis (NPHP) are overlapping syndromes. Recent studies show that JBST and MKS responsible gene products are localized in the transitional zone of the cilia, where they function as a diffusion barrier, and control protein sorting and ciliary membrane composition. Nephrocystins are gene products of NPHP responsible genes, and at least 11 genes have been identified. Although some nephrocystins interact with JBST and MKS proteins, proteomic analysis suggests that they do not form a single complex. Localization analysis reveals that nephrocystins can be divided into two groups. Group I nephrocystins are localized in the transitional zone, whereas group II nephrocystins are localized in the Inv compartment. Homologs of group I nephrocystins, but not group II nephrocystins, have been reported in C. reinhardtii and C. elegans. In this review, we summarize the structure of the ciliary base of C. reinhardtii, C. elegans and mammalian primary cilia, and discuss function of nephrocystins. We also propose a new classification of nephrocystins.
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476
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Huang L, Szymanska K, Jensen V, Janecke A, Innes A, Davis E, Frosk P, Li C, Willer J, Chodirker B, Greenberg C, McLeod D, Bernier F, Chudley A, Müller T, Shboul M, Logan C, Loucks C, Beaulieu C, Bowie R, Bell S, Adkins J, Zuniga F, Ross K, Wang J, Ban M, Becker C, Nürnberg P, Douglas S, Craft C, Akimenko MA, Hegele R, Ober C, Utermann G, Bolz H, Bulman D, Katsanis N, Blacque O, Doherty D, Parboosingh J, Leroux M, Johnson C, Boycott K. TMEM237 is mutated in individuals with a Joubert syndrome related disorder and expands the role of the TMEM family at the ciliary transition zone. Am J Hum Genet 2011; 89:713-30. [PMID: 22152675 PMCID: PMC3234373 DOI: 10.1016/j.ajhg.2011.11.005] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 10/25/2011] [Accepted: 11/08/2011] [Indexed: 12/23/2022] Open
Abstract
Joubert syndrome related disorders (JSRDs) have broad but variable phenotypic overlap with other ciliopathies. The molecular etiology of this overlap is unclear but probably arises from disrupting common functional module components within primary cilia. To identify additional module elements associated with JSRDs, we performed homozygosity mapping followed by next-generation sequencing (NGS) and uncovered mutations in TMEM237 (previously known as ALS2CR4). We show that loss of the mammalian TMEM237, which localizes to the ciliary transition zone (TZ), results in defective ciliogenesis and deregulation of Wnt signaling. Furthermore, disruption of Danio rerio (zebrafish) tmem237 expression produces gastrulation defects consistent with ciliary dysfunction, and Caenorhabditis elegans jbts-14 genetically interacts with nphp-4, encoding another TZ protein, to control basal body-TZ anchoring to the membrane and ciliogenesis. Both mammalian and C. elegans TMEM237/JBTS-14 require RPGRIP1L/MKS5 for proper TZ localization, and we demonstrate additional functional interactions between C. elegans JBTS-14 and MKS-2/TMEM216, MKSR-1/B9D1, and MKSR-2/B9D2. Collectively, our findings integrate TMEM237/JBTS-14 in a complex interaction network of TZ-associated proteins and reveal a growing contribution of a TZ functional module to the spectrum of ciliopathy phenotypes.
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Affiliation(s)
- Lijia Huang
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON K1H 8L1, Canada
| | - Katarzyna Szymanska
- Section of Ophthalmology and Neurosciences, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Victor L. Jensen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Andreas R. Janecke
- Department of Pediatrics II, Innsbruck Medical University, Innsbruck 6020, Austria
- Division of Human Genetics, Innsbruck Medical University, Innsbruck 6020, Austria
| | - A. Micheil Innes
- Department of Medical Genetics, University of Calgary, Calgary, AB T3B 6A8, Canada
| | - Erica E. Davis
- Center for Human Disease Modeling, Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Patrick Frosk
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB R3R 0J9, Canada
| | - Chunmei Li
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Jason R. Willer
- Center for Human Disease Modeling, Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Bernard N. Chodirker
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB R3R 0J9, Canada
| | - Cheryl R. Greenberg
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB R3R 0J9, Canada
| | - D. Ross McLeod
- Department of Medical Genetics, University of Calgary, Calgary, AB T3B 6A8, Canada
| | - Francois P. Bernier
- Department of Medical Genetics, University of Calgary, Calgary, AB T3B 6A8, Canada
| | - Albert E. Chudley
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB R3R 0J9, Canada
| | - Thomas Müller
- Department of Pediatrics II, Innsbruck Medical University, Innsbruck 6020, Austria
| | - Mohammad Shboul
- Institute of Medical Biology: Human Embryology, 8A Biomedical Grove, #05-40 Immunos, Singapore 138648, Singapore
| | - Clare V. Logan
- Section of Ophthalmology and Neurosciences, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Catrina M. Loucks
- Department of Medical Genetics, University of Calgary, Calgary, AB T3B 6A8, Canada
| | - Chandree L. Beaulieu
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON K1H 8L1, Canada
| | - Rachel V. Bowie
- School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
| | - Sandra M. Bell
- Section of Ophthalmology and Neurosciences, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Jonathan Adkins
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
| | - Freddi I. Zuniga
- Mary D. Allen Laboratory in Vision Research, Doheny Eye Institute, Departments of Ophthalmology and Cell and Neurobiology, Los Angeles, CA 90033-9224, USA
| | - Kevin D. Ross
- Department of Human Genetics, University of Chicago, Chicago, IL 60637, USA
| | - Jian Wang
- Robarts Research Institute and University of Western Ontario, London, ON, N6A 5C1, Canada
| | - Matthew R. Ban
- Robarts Research Institute and University of Western Ontario, London, ON, N6A 5C1, Canada
| | - Christian Becker
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50931 Cologne, Germany
| | - Stuart Douglas
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON K1H 8L1, Canada
| | - Cheryl M. Craft
- Mary D. Allen Laboratory in Vision Research, Doheny Eye Institute, Departments of Ophthalmology and Cell and Neurobiology, Los Angeles, CA 90033-9224, USA
| | | | - Robert A. Hegele
- Robarts Research Institute and University of Western Ontario, London, ON, N6A 5C1, Canada
| | - Carole Ober
- Department of Human Genetics, University of Chicago, Chicago, IL 60637, USA
| | - Gerd Utermann
- Division of Human Genetics, Innsbruck Medical University, Innsbruck 6020, Austria
| | - Hanno J. Bolz
- Center for Human Genetics, Bioscientia, 55218 Ingelheim, Germany
- Institute of Human Genetics, University Hospital of Cologne, 50931 Cologne, Germany
| | - Dennis E. Bulman
- Ottawa Hospital Research Institute and University of Ottawa, Ottawa, ON K1H 8L6, Canada
| | - Nicholas Katsanis
- Center for Human Disease Modeling, Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Oliver E. Blacque
- School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
| | - Dan Doherty
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
| | | | - Michel R. Leroux
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Colin A. Johnson
- Section of Ophthalmology and Neurosciences, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Kym M. Boycott
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON K1H 8L1, Canada
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477
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Novarino G, Akizu N, Gleeson JG. Modeling human disease in humans: the ciliopathies. Cell 2011; 147:70-9. [PMID: 21962508 DOI: 10.1016/j.cell.2011.09.014] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Indexed: 11/26/2022]
Abstract
Soon, the genetic basis of most human Mendelian diseases will be solved. The next challenge will be to leverage this information to uncover basic mechanisms of disease and develop new therapies. To understand how this transformation is already beginning to unfold, we focus on the ciliopathies, a class of multi-organ diseases caused by disruption of the primary cilium. Through a convergence of data involving mutant gene discovery, proteomics, and cell biology, more than a dozen phenotypically distinguishable conditions are now united as ciliopathies. Sitting at the interface between simple and complex genetic conditions, these diseases provide clues to the future direction of human genetics.
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Affiliation(s)
- Gaia Novarino
- Neurogenetics Laboratory, Institute for Genomic Medicine, Howard Hughes Medical Institute, Department of Neurosciences and Pediatrics, University of California, San Diego, La Jolla 92093, USA
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478
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Seo S, Zhang Q, Bugge K, Breslow DK, Searby CC, Nachury MV, Sheffield VC. A novel protein LZTFL1 regulates ciliary trafficking of the BBSome and Smoothened. PLoS Genet 2011; 7:e1002358. [PMID: 22072986 PMCID: PMC3207910 DOI: 10.1371/journal.pgen.1002358] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 09/11/2011] [Indexed: 11/29/2022] Open
Abstract
Many signaling proteins including G protein-coupled receptors localize to primary cilia, regulating cellular processes including differentiation, proliferation, organogenesis, and tumorigenesis. Bardet-Biedl Syndrome (BBS) proteins are involved in maintaining ciliary function by mediating protein trafficking to the cilia. However, the mechanisms governing ciliary trafficking by BBS proteins are not well understood. Here, we show that a novel protein, Leucine-zipper transcription factor-like 1 (LZTFL1), interacts with a BBS protein complex known as the BBSome and regulates ciliary trafficking of this complex. We also show that all BBSome subunits and BBS3 (also known as ARL6) are required for BBSome ciliary entry and that reduction of LZTFL1 restores BBSome trafficking to cilia in BBS3 and BBS5 depleted cells. Finally, we found that BBS proteins and LZTFL1 regulate ciliary trafficking of hedgehog signal transducer, Smoothened. Our findings suggest that LZTFL1 is an important regulator of BBSome ciliary trafficking and hedgehog signaling.
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Affiliation(s)
- Seongjin Seo
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Qihong Zhang
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Kevin Bugge
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - David K. Breslow
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Charles C. Searby
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Maxence V. Nachury
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Val C. Sheffield
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
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479
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Abstract
'Ciliopathies' are an emerging class of genetic multisystemic human disorders that are caused by a multitude of largely unrelated genes that affect ciliary structure/function. They are unified by shared clinical features, such as mental retardation, cystic kidney, retinal defects and polydactyly, and by the common localization of the protein products of these genes at or near the primary cilium of cells. With the realization that many previously disparate conditions are a part of this spectrum of disorders, there has been tremendous interest in the function of cilia in developmental signaling and homeostasis. Ciliopathies are mostly inherited as simple recessive traits, but phenotypic expressivity is under the control of numerous genetic modifiers, putting these conditions at the interface of simple and complex genetics. In this review, we discuss the ever-expanding ciliopathy field, which has three interrelated goals: developing a comprehensive understanding of genes mutated in the ciliopathies and required for ciliogenesis; understanding how the encoded proteins work together in complexes and networks to modulate activity and structure-function relationships; and uncovering signaling pathways and modifier relationships.
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Affiliation(s)
- Ji Eun Lee
- Neurogenetics Laboratory, Howard Hughes Medical Institute, Department of Neuroscience and Pediatrics, University of California, San Diego 92093-0691, USA.
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480
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van Reeuwijk J, Arts HH, Roepman R. Scrutinizing ciliopathies by unraveling ciliary interaction networks. Hum Mol Genet 2011; 20:R149-57. [PMID: 21862450 DOI: 10.1093/hmg/ddr354] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Research of cilia has gained significant momentum in the last 15 years, as an increasing number of human genetic diseases were found to be caused by disruption of a protein that localizes to cilia. These ciliopathies are as diverse as the functions of the associated proteins, covering a spectrum of overlapping phenotypes that ranges from relatively mild characteristics in isolated tissues with a late onset, to severe defects of multiple tissues with an onset early in embryogenesis that is incompatible with life. As cilia harbour many receptors and components of key signaling cascades, such as Hedgehog, Wnt, Notch and Hippo signaling, disruption of ciliary function has severe consequences. Recent (affinity) proteomics studies have focused on the composition and dynamics of ciliary protein interaction networks. This has unveiled important knowledge about the highly ordered, interconnected but very dynamic nature of the cilium as a molecular machine. Disruption of the members of the same functional modules of this machine leads to similar phenotypes, and detailed analyses of the binding repertoire, the biochemical properties and the biological functions of these modules have yielded new ciliopathy genes as well as new insights into the pathogenic mechanisms underlying ciliopathies.
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Affiliation(s)
- Jeroen van Reeuwijk
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, and Institute for Genetic and Metabolic Disease, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands
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Dowdle WE, Robinson JF, Kneist A, Sirerol-Piquer MS, Frints SGM, Corbit KC, Zaghloul NA, van Lijnschoten G, Mulders L, Verver DE, Zerres K, Reed RR, Attié-Bitach T, Johnson CA, García-Verdugo JM, Katsanis N, Bergmann C, Reiter JF. Disruption of a ciliary B9 protein complex causes Meckel syndrome. Am J Hum Genet 2011; 89:94-110. [PMID: 21763481 DOI: 10.1016/j.ajhg.2011.06.003] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/24/2011] [Accepted: 06/03/2011] [Indexed: 02/06/2023] Open
Abstract
Nearly every ciliated organism possesses three B9 domain-containing proteins: MKS1, B9D1, and B9D2. Mutations in human MKS1 cause Meckel syndrome (MKS), a severe ciliopathy characterized by occipital encephalocele, liver ductal plate malformations, polydactyly, and kidney cysts. Mouse mutations in either Mks1 or B9d2 compromise ciliogenesis and result in phenotypes similar to those of MKS. Given the importance of these two B9 proteins to ciliogenesis, we examined the role of the third B9 protein, B9d1. Mice lacking B9d1 displayed polydactyly, kidney cysts, ductal plate malformations, and abnormal patterning of the neural tube, concomitant with compromised ciliogenesis, ciliary protein localization, and Hedgehog (Hh) signal transduction. These data prompted us to screen MKS patients for mutations in B9D1 and B9D2. We identified a homozygous c.301A>C (p.Ser101Arg) B9D2 mutation that segregates with MKS, affects an evolutionarily conserved residue, and is absent from controls. Unlike wild-type B9D2 mRNA, the p.Ser101Arg mutation failed to rescue zebrafish phenotypes induced by the suppression of b9d2. With coimmunoprecipitation and mass spectrometric analyses, we found that Mks1, B9d1, and B9d2 interact physically, but that the p.Ser101Arg mutation abrogates the ability of B9d2 to interact with Mks1, further suggesting that the mutation compromises B9d2 function. Our data indicate that B9d1 is required for normal Hh signaling, ciliogenesis, and ciliary protein localization and that B9d1 and B9d2 are essential components of a B9 protein complex, disruption of which causes MKS.
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Affiliation(s)
- William E Dowdle
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, 94158, USA
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