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Coene KLM, Mans DA, Boldt K, Gloeckner CJ, van Reeuwijk J, Bolat E, Roosing S, Letteboer SJF, Peters TA, Cremers FPM, Ueffing M, Roepman R. The ciliopathy-associated protein homologs RPGRIP1 and RPGRIP1L are linked to cilium integrity through interaction with Nek4 serine/threonine kinase. Hum Mol Genet 2011; 20:3592-605. [PMID: 21685204 DOI: 10.1093/hmg/ddr280] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Recent studies have established ciliary dysfunction as the underlying cause of a broad range of multi-organ phenotypes, known as 'ciliopathies'. Ciliopathy-associated proteins have a common site of action in the cilium, however, their overall importance for ciliary function differs, as implied by the extreme variability in ciliopathy phenotypes. The aim of this study was to gain more insight in the function of two ciliopathy-associated protein homologs, RPGR interacting protein 1 (RPGRIP1) and RPGRIP1-like protein (RPGRIP1L). Mutations in RPGRIP1 lead to the eye-restricted disease Leber congenital amaurosis, while mutations in RPGRIP1L are causative for Joubert and Meckel syndrome, which affect multiple organs and are at the severe end of the ciliopathy spectrum. Using tandem affinity purification in combination with mass spectrometry, we identified Nek4 serine/threonine kinase as a prominent component of both the RPGRIP1- as well as the RPGRIP1L-associated protein complex. In ciliated cells, this kinase localized to basal bodies, while in ciliated organs, the kinase was predominantly detected at the ciliary rootlet. Down-regulation of NEK4 in ciliated cells led to a significant decrease in cilium assembly, pointing to a role for Nek4 in cilium dynamics. We now hypothesize that RPGRIP1 and RPGRIP1L function as cilium-specific scaffolds that recruit a Nek4 signaling network which regulates cilium stability. Our data are in line with previously established roles in the cilium of other members of the Nek protein family and define NEK4 as a ciliopathy candidate gene.
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Affiliation(s)
- Karlien L M Coene
- Department of Human Genetics (855), Radboud University Nijmegen Medical Centre, PO Box9101, 6500 HB Nijmegen, The Netherlands
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102
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Li L, Xiao X, Li S, Jia X, Wang P, Guo X, Jiao X, Zhang Q, Hejtmancik JF. Detection of variants in 15 genes in 87 unrelated Chinese patients with Leber congenital amaurosis. PLoS One 2011; 6:e19458. [PMID: 21602930 PMCID: PMC3094346 DOI: 10.1371/journal.pone.0019458] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 03/30/2011] [Indexed: 11/18/2022] Open
Abstract
Background Leber congenital amaurosis (LCA) is the earliest onset and most severe form of hereditary retinal dystrophy. So far, full spectrum of variations in the 15 genes known to cause LCA has not been systemically evaluated in East Asians. Therefore, we performed comprehensive detection of variants in these 15 genes in 87 unrelated Han Chinese patients with LCA. Methodology/Principal Findings The 51 most frequently mutated exons and introns in the 15 genes were selected for an initial scan using cycle sequencing. All the remaining exons in 11 of the 15 genes were subsequently sequenced. Fifty-three different variants were identified in 44 of the 87 patients (50.6%), involving 78 of the 88 alleles (11 homozygous and 56 heterozygous variants). Of the 53 variants, 35 (66%) were novel pathogenic mutations. In these Chinese patients, variants in GUCY2D are the most common cause of LCA (16.1% cases), followed by CRB1 (11.5%), RPGRIP1 (8%), RPE65 (5.7%), SPATA7 (4.6%), CEP290 (4.6%), CRX (3.4%), LCA5 (2.3%), MERTK (2.3%), AIPL1 (1.1%), and RDH12 (1.1%). This differs from the variation spectrum described in other populations. An initial scan of 55 of 215 PCR amplicons, including 214 exons and 1 intron, detected 83.3% (65/78) of the mutant alleles ultimately found in these 87 patients. In addition, sequencing only 9 exons would detect over 50% of the identified variants and require less than 5% of the labor and cost of comprehensive sequencing for all exons. Conclusions/Significance Our results suggest that specific difference in the variation spectrum found in LCA patients from the Han Chinese and other populations are related by ethnicity. Sequencing exons in order of decreasing risk is a cost-effective way to identify causative mutations responsible for LCA, especially in the context of genetic counseling for individual patients in a clinical setting.
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Affiliation(s)
- Lin Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Xueshan Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Xiaoyun Jia
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Panfeng Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Xiangming Guo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Xiaodong Jiao
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Qingjiong Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong, China
- * E-mail:
| | - J. Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
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103
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Kuznetsova T, Zangerl B, Goldstein O, Acland GM, Aguirre GD. Structural organization and expression pattern of the canine RPGRIP1 isoforms in retinal tissue. Invest Ophthalmol Vis Sci 2011; 52:2989-98. [PMID: 21282582 DOI: 10.1167/iovs.10-6094] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To examine the structure and expression of RPGRIP1 in dog retina. METHODS Determination of the structural analysis and expression pattern of canine RPGRIP1 (cRPGRIP1) was based on cDNA amplification. Absolute quantification of the expression level of cRPGRIP1 splice variants was determined by qRT-PCR. Regulatory structures were examined by computational analysis of comparative genomics. RESULTS cRPGRIP1 encompasses 25 exons that harbor a 3627-bp open reading frame (ORF) encoding a 1209-amino-acid (aa)-predicted protein. In addition to the main transcript, five full-length and several partial cRPGRIP1 isoforms were identified revealing four alternative 3'-terminal exons--24, 19a, 19c, and 19d--three of which could potentially produce C-terminally truncated proteins that lack the RPGR-interacting domain. A complex organization of the 5'-UTR for the cRPGRIP1 splice products have been described, with a common promoter driving multiple isoforms, including four full-length transcripts using the 3'-terminal exon 24. In addition, a potential alternative internal promoter was revealed to initiate at least two cRPGRIP1 splice variants sharing the same 3'-terminal exon 19c. Transcription initiation sites were highly supported by conserved arrangements of cis-elements predicted in a bioinformatic analysis of orthologous RPGRIP1 promoter regions. CONCLUSIONS The use of alternative transcription start and termination sites results in substantial heterogeneity of cRPGRIP1 transcripts, many of which are likely to have tissue-specific expression. The identified exon-intron structure of cRPGRIP1 isoforms provides a basis for evaluating the gene defects underlying inherited retinal disorders in dogs.
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Affiliation(s)
- Tatyana Kuznetsova
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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104
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Qatarneh D, Mehta H, Lee V. Insight into Leber congenital amaurosis: potential for gene therapy. EXPERT REVIEW OF OPHTHALMOLOGY 2011. [DOI: 10.1586/eop.11.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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105
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Coppieters F, Lefever S, Leroy BP, De Baere E. CEP290, a gene with many faces: mutation overview and presentation of CEP290base. Hum Mutat 2011; 31:1097-108. [PMID: 20690115 DOI: 10.1002/humu.21337] [Citation(s) in RCA: 199] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ciliopathies are an emerging group of disorders, caused by mutations in ciliary genes. One of the most intriguing disease genes associated with ciliopathies is CEP290, in which mutations cause a wide variety of distinct phenotypes, ranging from isolated blindness over Senior-Loken syndrome (SLS), nephronophthisis (NPHP), Joubert syndrome (related disorders) (JS[RD]), Bardet-Biedl syndrome (BBS), to the lethal Meckel-Grüber syndrome (MKS). Despite the identification of over 100 unique CEP290 mutations, no clear genotype-phenotype correlations could yet be established, and consequently the predictive power of a CEP290-related genotype remains limited. One of the challenges is a better understanding of second-site modifiers. In this respect, there is a growing interest in the potential modifying effects of variations in genes encoding other members of the ciliary proteome that interact with CEP290. Here, we provide an overview of all CEP290 mutations identified so far, with their associated phenotypes. To this end, we developed CEP290base, a locus-specific mutation database that links mutations with patients and their phenotypes (medgen.ugent.be/cep290base).
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Affiliation(s)
- Frauke Coppieters
- Center for Medical Genetics, Ghent University Hospital, Ghent, Belgium
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106
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Coppieters F, Casteels I, Meire F, De Jaegere S, Hooghe S, van Regemorter N, Van Esch H, Matuleviciene A, Nunes L, Meersschaut V, Walraedt S, Standaert L, Coucke P, Hoeben H, Kroes HY, Vande Walle J, de Ravel T, Leroy BP, De Baere E. Genetic screening of LCA in Belgium: predominance of CEP290 and identification of potential modifier alleles in AHI1 of CEP290-related phenotypes. Hum Mutat 2011; 31:E1709-66. [PMID: 20683928 PMCID: PMC3048164 DOI: 10.1002/humu.21336] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Leber Congenital Amaurosis (LCA), the most severe inherited retinal dystrophy, is genetically heterogeneous, with 14 genes accounting for 70% of patients. Here, 91 LCA probands underwent LCA chip analysis and subsequent sequencing of 6 genes (CEP290, CRB1, RPE65, GUCY2D, AIPL1and CRX), revealing mutations in 69% of the cohort, with major involvement of CEP290 (30%). In addition, 11 patients with early-onset retinal dystrophy (EORD) and 13 patients with Senior-Loken syndrome (SLS), LCA-Joubert syndrome (LCA-JS) or cerebello-oculo-renal syndrome (CORS) were included. Exhaustive re-inspection of the overall phenotypes in our LCA cohort revealed novel insights mainly regarding the CEP290-related phenotype. The AHI1 gene was screened as a candidate modifier gene in three patients with the same CEP290 genotype but different neurological involvement. Interestingly, a heterozygous novel AHI1 mutation, p.Asn811Lys, was found in the most severely affected patient. Moreover, AHI1 screening in five other patients with CEP290-related disease and neurological involvement revealed a second novel missense variant, p.His758Pro, in one LCA patient with mild mental retardation and autism. These two AHI1 mutations might thus represent neurological modifiers of CEP290-related disease. © 2010 Wiley-Liss, Inc.
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Affiliation(s)
- Frauke Coppieters
- Center for Medical Genetics Ghent, Ghent University Hospital, Ghent, Belgium
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107
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Pawlyk BS, Bulgakov OV, Liu X, Xu X, Adamian M, Sun X, Khani SC, Berson EL, Sandberg MA, Li T. Replacement gene therapy with a human RPGRIP1 sequence slows photoreceptor degeneration in a murine model of Leber congenital amaurosis. Hum Gene Ther 2011; 21:993-1004. [PMID: 20384479 DOI: 10.1089/hum.2009.218] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
RPGR-interacting protein-1 (RPGRIP1) is localized in the photoreceptor-connecting cilium, where it anchors the RPGR (retinitis pigmentosa GTPase regulator) protein, and its function is essential for photoreceptor maintenance. Genetic defect in RPGRIP1 is a known cause of Leber congenital amaurosis (LCA), a severe, early-onset form of retinal degeneration. We evaluated the efficacy of replacement gene therapy in a murine model of LCA carrying a targeted disruption of RPGRIP1. The replacement construct, packaged in an adeno-associated virus serotype 8 (AAV8) vector, used a rhodopsin kinase gene promoter to drive RPGRIP1 expression. Both promoter and transgene were of human origin. After subretinal delivery of the replacement gene in the mutant mice, human RPGRIP1 was expressed specifically in photoreceptors, localized correctly in the connecting cilia, and restored the normal localization of RPGR. Electroretinogram and histological examinations showed better preservation of rod and cone photoreceptor function and improved photoreceptor survival in the treated eyes. This study demonstrates the efficacy of human gene replacement therapy and validates a gene therapy design for future clinical trials in patients afflicted with this condition. Our results also have therapeutic implications for other forms of retinal degenerations attributable to a ciliary defect.
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Affiliation(s)
- Basil S Pawlyk
- Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, and Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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108
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Abstract
Glaucoma is a genetically heterogeneous disorder and is the second cause of blindness worldwide owing to the progressive degeneration of retinal ganglion neurons. Very few genes causing glaucoma were identified to this date. In this study, we screened 10 candidate genes of glaucoma between the D14S261 and D14S121 markers of chromosome 14q11, a critical region previously linked to primary open-angle glaucoma (POAG). Mutation analyses of two large cohorts of patients with POAG, normal tension glaucoma (NTG) and juvenile open-angle glaucoma (JOAG), and control subjects, found only association of non-synonymous heterozygous variants of the retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) with POAG, NTG and JOAG. The 20 non-synonymous variants identified in RPGRIP1 were all distinct from variants causing photoreceptor dystrophies and were found throughout all but one domain (RPGR-interacting domain) of RPGRIP1. Among them, 14 missense variants clustered within or around the C2 domains of RPGRIP1. Yeast two-hybrid analyses of a subset of the missense mutations within the C2 domains of RPGRIP1 shows that five of them (p.R598Q, p.A635G, p.T806I, p.A837G and p.I838V) decrease the association of the C2 domains with nephrocystin-4 (NPHPH). When considering only these five confirmed C2-domain mutations, the association remains statistically significant (P=0.001). Altogether, the data support that heterozygous non-synonymous variants of RPGRIP1 may cause or increase the susceptibility to various forms of glaucoma and that among other factors, physical impairment of the interaction of RPGRIP1with different proteins may contribute to the pathogenesis of forms of glaucoma.
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109
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Murga-Zamalloa CA, Desai NJ, Hildebrandt F, Khanna H. Interaction of ciliary disease protein retinitis pigmentosa GTPase regulator with nephronophthisis-associated proteins in mammalian retinas. Mol Vis 2010; 16:1373-81. [PMID: 20664800 PMCID: PMC2905641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 07/13/2010] [Indexed: 11/04/2022] Open
Abstract
PURPOSE Retinitis pigmentosa GTPase regulator (RPGR) is a cilia-centrosomal protein that frequently mutates in X-linked retinal degeneration and associated disorders. RPGR interacts with multiple ciliary proteins in the retina. Perturbations in the assembly of RPGR complexes are associated with retinal degeneration. This study was undertaken to delineate the composition and dissection of RPGR complexes in mammalian retinas. METHODS Immunoprecipitation of RPGR from ciliary fraction of bovine retina was performed, followed by mass spectrometry analysis. The glutathione S-transferase pull-down assay was performed to validate the interaction. Immunodepletion experiments were performed to dissect the partitioning of RPGR in different protein complexes in mammalian retinas. RESULTS We found that RPGR associates with a ciliary protein nephrocystin-4 (nephroretinin; NPHP4) that is mutated in nephronophthisis (NPH) and RP (Senior-Løken syndrome). This association is abolished in the Rpgr-knockout mouse retina. The RCC1-like domain of RPGR interacts with the N-terminal 316 amino acids of NPHP4. In the retina, RPGR also associates with NPHP1, an NPHP4-interacting protein; RPGR interacts directly with amino acids 243-586 of NPHP1. We further show that, in the retina, RPGR associates with and is partitioned in at least two different complexes with NPHP-associated proteins, (i) NPHP1, NPHP2, and NPHP5, and (ii) NPHP4, NPHP6, and NPHP8. CONCLUSIONS RPGR may regulate some complexes with NPHP proteins in the mammalian retina. The disruption of these complexes may contribute to the pathogenesis of retinal degeneration in X-linked RP and associated ciliary diseases.
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Affiliation(s)
- Carlos A. Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences and Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
| | - Nimit J. Desai
- Department of Ophthalmology and Visual Sciences and Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
| | | | - Hemant Khanna
- Department of Ophthalmology and Visual Sciences and Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
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Murga-Zamalloa CA, Swaroop A, Khanna H. RPGR-containing protein complexes in syndromic and non-syndromic retinal degeneration due to ciliary dysfunction. J Genet 2010; 88:399-407. [PMID: 20090203 DOI: 10.1007/s12041-009-0061-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dysfunction of primary cilia due to mutations in cilia-centrosomal proteins is associated with pleiotropic disorders. The primary (or sensory) cilium of photoreceptors mediates polarized trafficking of proteins for efficient phototransduction. Retinitis pigmentosa GTPase regulator (RPGR) is a cilia-centrosomal protein mutated in >70% of X-linked RP cases and 10%-20% of simplex RP males. Accumulating evidence indicates that RPGR may facilitate the orchestration of multiple ciliary protein complexes. Disruption of these complexes due to mutations in component proteins is an underlying cause of associated photoreceptor degeneration. Here, we highlight the recent developments in understanding the mechanism of cilia-dependent photoreceptor degeneration due to mutations in RPGR and PGR-interacting proteins in severe genetic diseases, including retinitis pigmentosa, Leber congenital amaurosis (LCA), Joubert syndrome, and Senior-Loken syndrome, and explore the physiological relevance of photoreceptor ciliary protein complexes.
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Affiliation(s)
- Carlos A Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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111
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Gerner M, Haribaskar R, Pütz M, Czerwitzki J, Walz G, Schäfer T. The retinitis pigmentosa GTPase regulator interacting protein 1 (RPGRIP1) links RPGR to the nephronophthisis protein network. Kidney Int 2010; 77:891-6. [DOI: 10.1038/ki.2010.27] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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112
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Ghosh AK, Murga-Zamalloa CA, Chan L, Hitchcock PF, Swaroop A, Khanna H. Human retinopathy-associated ciliary protein retinitis pigmentosa GTPase regulator mediates cilia-dependent vertebrate development. Hum Mol Genet 2010; 19:90-8. [PMID: 19815619 DOI: 10.1093/hmg/ddp469] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Dysfunction of primary cilia is associated with tissue-specific or syndromic disorders. RPGR is a ciliary protein, mutations in which can lead to retinitis pigmentosa (RP), cone-rod degeneration, respiratory infections and hearing disorders. Though RPGR is implicated in ciliary transport, the pathogenicity of RPGR mutations and the mechanism of underlying phenotypic heterogeneity are still unclear. Here we have utilized genetic rescue studies in zebrafish to elucidate the effect of human disease-associated mutations on its function. We show that rpgr is expressed predominantly in the retina, brain and gut of zebrafish. In the retina, RPGR primarily localizes to the sensory cilium of photoreceptors. Antisense morpholino (MO)-mediated knockdown of rpgr function in zebrafish results in reduced length of Kupffer's vesicle (KV) cilia and is associated with ciliary anomalies including shortened body-axis, kinked tail, hydrocephaly and edema but does not affect retinal development. These phenotypes can be rescued by wild-type (WT) human RPGR. Several of the RPGR mutants can also reverse the MO-induced phenotype, suggesting their potential hypomorphic function. Notably, selected RPGR mutations observed in XLRP (T99N, E589X) or syndromic RP (T124fs, K190fs and L280fs) do not completely rescue the rpgr-MO phenotype, indicating a more deleterious effect of the mutation on the function of RPGR. We propose that RPGR is involved in cilia-dependent cascades during development in zebrafish. Our studies provide evidence for a heterogenic effect of the disease-causing mutations on the function of RPGR.
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Affiliation(s)
- Amiya K Ghosh
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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113
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Walia S, Fishman GA, Jacobson SG, Aleman TS, Koenekoop RK, Traboulsi EI, Weleber RG, Pennesi ME, Heon E, Drack A, Lam BL, Allikmets R, Stone EM. Visual acuity in patients with Leber's congenital amaurosis and early childhood-onset retinitis pigmentosa. Ophthalmology 2010; 117:1190-8. [PMID: 20079931 DOI: 10.1016/j.ophtha.2009.09.056] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 09/25/2009] [Accepted: 09/28/2009] [Indexed: 01/28/2023] Open
Abstract
PURPOSE To correlate visual acuity of patients with Leber's congenital amaurosis (LCA) and early childhood-onset retinitis pigmentosa (RP) with mutations in underlying LCA genes. DESIGN Multicentered retrospective observational study. PARTICIPANTS After exclusion of 28 subjects, 169 patients with the diagnosis of LCA and 27 patients with early childhood-onset RP were included in the study because the underlying mutations in AIPL1, GUCY2D, RDH12, RPE65, CRX, CRB1, RPGRIP1, CEP290, LCA5, and TULP1 genes could be identified in this cohort of patients. METHODS We collected data on best-corrected visual acuity as recorded at the time of the patient's most recent visit to one of the participating ophthalmology departments. The median and range of visual acuities for each genetic subtype were calculated separately for the LCA and early childhood-onset RP groups. MAIN OUTCOME MEASURES The range and median best-corrected visual acuities for each genetic subtype and age-related mean visual acuities for each genetic subtype. RESULTS A wide variation in visual acuity was observed in patients with LCA and RPE65, RDH12, and CRB1 mutations, whereas AIPL1, GUCY2D, CRX, and RPGRIP1 gene mutations were associated with severely decreased visual acuities beginning within the first year of life. It was also noted that patients with either an RPE65 or CRB1 mutation have progressive visual loss with advancing age. Onset of visual symptoms after infancy was associated with a relatively better visual prognosis. CONCLUSIONS The data obtained from this study will help clinicians provide counseling on visual prognosis to patients with known mutations in LCA genes and be of value in future studies aimed at the treatment of LCA and early childhood-onset RP.
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Affiliation(s)
- Saloni Walia
- Department of Ophthalmology, University of Illinois at Chicago, Chicago, Illinois, USA
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114
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Murga-Zamalloa C, Swaroop A, Khanna H. Multiprotein complexes of Retinitis Pigmentosa GTPase regulator (RPGR), a ciliary protein mutated in X-linked Retinitis Pigmentosa (XLRP). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 664:105-14. [PMID: 20238008 DOI: 10.1007/978-1-4419-1399-9_13] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mutations in Retinitis Pigmentosa GTPase Regulator (RPGR) are a frequent cause of X-linked Retinitis Pigmentosa (XLRP). The RPGR gene undergoes extensive alternative splicing and encodes for distinct protein isoforms in the retina. Extensive studies using isoform-specific antibodies and mouse mutants have revealed that RPGR predominantly localizes to the transition zone to primary cilia and associates with selected ciliary and microtubule-associated assemblies in photoreceptors. In this chapter, we have summarized recent advances on understanding the role of RPGR in photoreceptor protein trafficking. We also provide new evidence that suggests the existence of discrete RPGR multiprotein complexes in photoreceptors. Piecing together the RPGR-interactome in different subcellular compartments should provide critical insights into the role of alternative RPGR isoforms in associated orphan and syndromic retinal degenerative diseases.
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Affiliation(s)
- Carlos Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Ann Arbor, MI 48105, USA
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Veltel S, Wittinghofer A. RPGR and RP2: targets for the treatment of X-linked retinitis pigmentosa? Expert Opin Ther Targets 2009; 13:1239-51. [PMID: 19702441 DOI: 10.1517/14728220903225016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Retinitis pigmentosa is the most important hereditary eye disease and there is currently no cure available. Although mutations were found in more than 40 genes in patients with retinitis pigmentosa, only two genes have thus far been found to be responsible for one of the most severe forms of the disease, X-linked retinitis pigmentosa. In this review, we highlight the current knowledge about the two gene products RPGR and RP2 and try to link genetic data from patients with functional data on the corresponding proteins. Based on the fact that recent gene therapeutic approaches for eye diseases are at a very promising stage, we discuss the potential of RPGR and RP2 as drug targets to treat retinitis pigmentosa.
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Affiliation(s)
- Stefan Veltel
- Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto Hahn-Street 11, 44227 Dortmund, Germany
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Miyadera K, Kato K, Aguirre-Hernández J, Tokuriki T, Morimoto K, Busse C, Barnett K, Holmes N, Ogawa H, Sasaki N, Mellersh CS, Sargan DR. Phenotypic variation and genotype-phenotype discordance in canine cone-rod dystrophy with an RPGRIP1 mutation. Mol Vis 2009; 15:2287-305. [PMID: 19936303 PMCID: PMC2779058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 10/28/2009] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Previously, a 44 bp insertion in exon 2 of retinitis pigmentosa GTPase interacting protein 1 (RPGRIP1) was identified as the cause of cone-rod dystrophy 1 (cord1), a recessive form of progressive retinal atrophy (PRA) in the Miniature Longhaired Dachshund (MLHD), a dog model for Leber congenital amaurosis. The cord1 locus was mapped using MLHDs from an inbred colony with a homogeneous early onset disease phenotype. In this paper, the MLHD pet population was studied to investigate phenotypic variation and genotype-phenotype correlation. Further, the cord1 locus was fine-mapped using PRA cases from the MLHD pet population to narrow the critical region. Other dog breeds were also screened for the RGPRIP1 insertion. METHODS This study examined phenotypic variation in an MLHD pet population that included 59 sporadic PRA cases and 18 members of an extended family with shared environment and having six PRA cases. Ophthalmologic evaluations included behavioral abnormalities, responses to menace and light, fundoscopy, and electroretinography (ERG). The RPGRIP1 insertion was screened for in all cases and 200 apparently normal control MLHDs and in 510 dogs from 66 other breed. To fine-map the cord1 locus in the MLHD, 74 PRA cases and 86 controls aged 4 years or more were genotyped for 24 polymorphic markers within the previously mapped cord1 critical region of 14.15 Mb. RESULTS Among sporadic PRA cases from the MLHD pet population, the age of onset varied from 4 months to 15 years old; MLHDs from the extended family also showed variable onset and rate of progression. Screening for the insertion in RPGRIP1 identified substantial genotype-phenotype discordance: 16% of controls were homozygous for the insertion (RPGRIP1(-/-)), while 20% of PRA cases were not homozygous for it. Four other breeds were identified to carry the insertion including English Springer Spaniels and Beagles with insertion homozygotes. The former breed included both controls and PRA cases, yet in the latter breed, cone ERG was undetectable in two dogs with no clinically apparent visual dysfunction. Notably, the insertion in the Beagles was a longer variant of that seen in the other breeds. Fine-mapping of the cord1 locus narrowed the critical region on CFA15 from 14.15 Mb to 1.74 Mb which still contains the RPGRIP1 gene. CONCLUSIONS Extensive phenotypic variations of onset age and progression rate were observed in PRA cases of the MLHD pet population. The insertion in RPGRIP1 showed the strongest association with the disease, yet additional as well as alternative factors may account for the substantial genotype-phenotype discordance.
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Affiliation(s)
- Keiko Miyadera
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, United Kingdom,Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Kumiko Kato
- Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Jesús Aguirre-Hernández
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, United Kingdom
| | - Tsuyoshi Tokuriki
- Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Kyohei Morimoto
- Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Claudia Busse
- Comparative Ophthalmology Unit, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk, United Kingdom
| | - Keith Barnett
- Comparative Ophthalmology Unit, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk, United Kingdom
| | - Nigel Holmes
- Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk, United Kingdom
| | | | - Nobuo Sasaki
- Department of Veterinary Medical Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Cathryn S. Mellersh
- Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk, United Kingdom
| | - David R. Sargan
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, United Kingdom
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Sundaresan P, Vijayalakshmi P, Thompson S, Ko AC, Fingert JH, Stone EM. Mutations that are a common cause of Leber congenital amaurosis in northern America are rare in southern India. Mol Vis 2009; 15:1781-7. [PMID: 19753312 PMCID: PMC2742639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Accepted: 08/19/2009] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To test patients from southern India for the presence of mutations that most commonly cause Leber congenital amaurosis (LCA) in northern America. METHODS A review of the literature identified 177 unique LCA causing mutations in eight different genes: aryl hydrocarbon receptor interacting protein-like 1 (AIPL1), crumbs homolog 1 (CRB1), cone-rod homeobox (CRX), guanylate cyclase 2D (GUCY2D), nephronophthisis 6 (NPHP6), retinol dehydrogenase 12 (RDH12), retinal pigment epithelium-specific protein 65 kDa (RPE65), and retinitis pigmentosa GTPase regulator interacting protein 1 (RPGRIP1). Allele-specific ligation assay and bidirectional sequencing were used to test 38 unrelated LCA patients from southern India for 104 of these mutations, which contribute to more than 30% of the LCA cases in a northern American population. RESULTS Only one participant was found to harbor one of the 104 mutations in the allele-specific assay (homozygous RPE65 Tyr368His). A mutation that was not part of the assay (homozygous RPE65 Tyr143Asp) was incidentally detected in a second patient when an equivocal signal from one allele on the assay was followed up with automated DNA sequencing. CONCLUSIONS Mutations that contribute to 30% of the LCA cases in northern America were detected in only 2.6% of LCA cases in our cohort from southern India. There were no instances of IVS26 c.2991+1655 A>G in NPHP6, the most commonly detected mutation in LCA. These data suggest that LCA in India is caused primarily by a different set of mutations in the same genes associated with disease in northern America, or by mutations in other genes that have not yet been discovered. Therefore, mutation-specific assays developed for European and northern American cohorts may not be suited for testing LCA patients from India or other ethnically distinct populations.
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Affiliation(s)
- Periasamy Sundaresan
- Department of Genetics, Dr. G. Venkataswamy Eye Research Institute, Aravind Medical Research Foundation, Madurai, Tamilnadu, India
| | - P. Vijayalakshmi
- Department of Paediatric Ophthalmology, Aravind Eye Hospital, Madurai, Tamilnadu, India
| | - Stewart Thompson
- Howard Hughes Medical Institute, Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA
| | - Audrey C. Ko
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA
| | - John H. Fingert
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA
| | - Edwin M. Stone
- Howard Hughes Medical Institute, Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA
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Sun X, Pawlyk B, Xu X, Liu X, Bulgakov OV, Adamian M, Sandberg MA, Khani SC, Tan MH, Smith AJ, Ali RR, Li T. Gene therapy with a promoter targeting both rods and cones rescues retinal degeneration caused by AIPL1 mutations. Gene Ther 2009; 17:117-31. [PMID: 19710705 PMCID: PMC2804971 DOI: 10.1038/gt.2009.104] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
AIPL1 is required for the biosynthesis of photoreceptor phosphodiesterase (PDE)1–3. Gene defects in AIPL1 cause a heterogeneous set of conditions ranging from Leber Congenital Amaurosis (LCA), the severest form of early-onset retinal degeneration, to milder forms such as retinitis pigmentosa (RP) and cone-rod dystrophy1,4,5. In mice, null and hypomorphic alleles cause retinal degeneration similar to human LCA and RP, respectively2,3,6. Thus these mouse models represent two ends of the disease spectrum associated with AIPL1 gene defects in humans. We evaluated whether adeno-associated virus (AAV)-mediated gene replacement therapy in these models could restore PDE biosynthesis in rods and cones and thereby improve photoreceptor survival. We validated the efficacy of human AIPL1 (isoform 1) replacement gene controlled by a promoter derived from the human rhodopsin kinase (RK) gene which is active in both rods and cones7. We found substantial and long-term rescue of the disease phenotype as a result of transgene expression. This is the first gene therapy study in which both rods and cones were targeted successfully with a single photoreceptor-specific promoter. We propose that the vector and construct design used in this study could serve as a prototype for a human clinical trial.
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Affiliation(s)
- X Sun
- Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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Won J, Gifford E, Smith RS, Yi H, Ferreira PA, Hicks WL, Li T, Naggert JK, Nishina PM. RPGRIP1 is essential for normal rod photoreceptor outer segment elaboration and morphogenesis. Hum Mol Genet 2009; 18:4329-39. [PMID: 19679561 DOI: 10.1093/hmg/ddp385] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The function of the retinitis pigmentosa GTPase regulator interacting protein 1 (RPGRIP1) gene is currently not known. However, mutations within the gene lead to Leber Congenital Amaurosis and autosomal recessive retinitis pigmentosa in human patients. In a previously described knockout mouse model of the long splice variant of Rpgrip1, herein referred to as Rpgrip1(tm1Tili) mice, mislocalization of key outer segment proteins and dysmorphogenesis of outer segment discs preceded subsequent photoreceptor degeneration. In this report, we describe a new mouse model carrying a splice acceptor site mutation in Rpgrip1, herein referred to as Rpgrip1(nmf247) that is phenotypically distinct from Rpgrip1(tm1Tili) mice. Photoreceptor degeneration in homozygous Rpgrip1(nmf247) mice is earlier in onset and more severe when compared with Rpgrip1(tm1Tili) mice. Also, ultrastructural studies reveal that whereas Rpgrip1(nmf247) mutants have a normal structure and number of connecting cilia, unlike Rpgrip1(tm1Tili) mice, they do not elaborate rod outer segments (OS). Therefore, in addition to its role in OS disc morphogenesis, RPGRIP1 is essential for rod OS formation. Our study indicates the absence of multiple Rpgrip1 isoforms in Rpgrip1(nmf247) mice, suggesting different isoforms may play different roles in photoreceptors and underscores the importance of considering splice variants when generating targeted null mutations.
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Affiliation(s)
- Jungyeon Won
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
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Abstract
RPGRIP1 encodes the retinitis pigmentosa GTPase interacting protein 1 and interacts with RPGR, the latter represents the major X-linked RP (XRRP) gene, as it accounts for 70-80% of the XRRP patients and up to 13% of all RP patients. RPGRIP1 contains a C-terminal RPGR interacting domain (RID) and a coiled-coil (CC) domain, which is homologous to proteins involved in vesicular trafficking. The interactions between the two proteins is between the RCC1-homologous domain of RPGR (RHD) and the RPGR-interacting domain of RPGRIP1 (RID). Both proteins co-localize to the photoreceptor connecting cilium and RPGRIP1 appears to be a structural component of the ciliary axoneme of the connecting cilium (which connects the inner to the outer segment of the photoreceptors) of both rods and cones and functions to anchor RPGR within the cilium.RPGRIP1 loci encode several different isoforms, which have distinct cellular, sub cellular and biochemical properties. RPGRIP1 is uniquely expressed in amacrine cells of the inner retina. Knockout mice studies have shown that RPGRIP1 is required for disc morphogenesis of the outer segments in the mouse, perhaps by regulating cytoskeleton dynamics. Thus far RPGRIP1 appears to be only mutated in LCA and is associated with 6% of LCA in two series. The purpose of this review is to highlight recent advances in our understanding of RPGRIP1 function in normal and diseased retinas.
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Affiliation(s)
- Robert K Koenekoop
- McGill Ocular Genetics Laboratory, Montreal Children's Hospital Research Institute, McGill University Health Center, Montreal, Canada.
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A common allele in RPGRIP1L is a modifier of retinal degeneration in ciliopathies. Nat Genet 2009; 41:739-45. [PMID: 19430481 PMCID: PMC2783476 DOI: 10.1038/ng.366] [Citation(s) in RCA: 230] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Accepted: 02/26/2009] [Indexed: 11/08/2022]
Abstract
Despite rapid advances in the identification of genes involved in disease, the predictive power of the genotype remains limited, in part owing to poorly understood effects of second-site modifiers. Here we demonstrate that a polymorphic coding variant of RPGRIP1L (retinitis pigmentosa GTPase regulator-interacting protein-1 like), a ciliary gene mutated in Meckel-Gruber (MKS) and Joubert (JBTS) syndromes, is associated with the development of retinal degeneration in individuals with ciliopathies caused by mutations in other genes. As part of our resequencing efforts of the ciliary proteome, we identified several putative loss-of-function RPGRIP1L mutations, including one common variant, A229T. Multiple genetic lines of evidence showed this allele to be associated with photoreceptor loss in ciliopathies. Moreover, we show that RPGRIP1L interacts biochemically with RPGR, loss of which causes retinal degeneration, and that the Thr229-encoded protein significantly compromises this interaction. Our data represent an example of modification of a discrete phenotype of syndromic disease and highlight the importance of a multifaceted approach for the discovery of modifier alleles of intermediate frequency and effect.
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Abstract
PURPOSE OF REVIEW The present review addresses the mechanisms, genetics and pathogenesis of Usher syndrome. RECENT FINDINGS Recent molecular findings have provided more information regarding the pathogenesis of this disorder and the wide phenotypic variation in both audiovestibular and/or visual systems. Evidence has begun to emerge supporting a theory of a protein interactome involving the Usher proteins in both the inner ear and the retina. This interactome appears to be important for hair cell development in the ear but its role in the retina remains unclear. SUMMARY Understanding clinical disease progression and molecular pathways is important in the progress towards developing gene therapy to prevent blindness due to Usher syndrome as well as delivering prognostic information to affected individuals.
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123
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Wang H, den Hollander AI, Moayedi Y, Abulimiti A, Li Y, Collin RW, Hoyng CB, Lopez I, Bray M, Lewis RA, Lupski JR, Mardon G, Koenekoop RK, Chen R, Koenekoop RK, Chen R. Mutations in SPATA7 cause Leber congenital amaurosis and juvenile retinitis pigmentosa. Am J Hum Genet 2009; 84:380-7. [PMID: 19268277 DOI: 10.1016/j.ajhg.2009.02.005] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/04/2009] [Accepted: 02/06/2009] [Indexed: 11/25/2022] Open
Abstract
Leber congenital amaurosis (LCA) and juvenile retinitis pigmentosa (RP) are the most common hereditary causes of visual impairment in infants and children. Using homozygosity mapping, we narrowed down the critical region of the LCA3 locus to 3.8 Mb between markers D14S1022 and D14S1005. By direct Sanger sequencing of all genes within this region, we found a homozygous nonsense mutation in the SPATA7 gene in Saudi Arabian family KKESH-060. Three other loss-of-function mutations were subsequently discovered in patients with LCA or juvenile RP from distinct populations. Furthermore, we determined that Spata7 is expressed in the mature mouse retina. Our findings reveal another human visual-disease gene that causes LCA and juvenile RP.
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Lhériteau E, Libeau L, Stieger K, Deschamps JY, Mendes-Madeira A, Provost N, Lemoine F, Mellersh C, Ellinwood NM, Cherel Y, Moullier P, Rolling F. The RPGRIP1-deficient dog, a promising canine model for gene therapy. Mol Vis 2009; 15:349-61. [PMID: 19223988 PMCID: PMC2642837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Accepted: 02/10/2009] [Indexed: 12/04/2022] Open
Abstract
PURPOSE To evaluate the RPGRIP1-deficient miniature longhaired dachshund (MLHD) dog as a potential candidate for gene therapy. METHODS Six RPGRIP1-deficient MLHD dogs from our dog colony have been observed for two years using a variety of noninvasive procedures. These included bilateral full-field electroretinograms (ERG) to evaluate retinal function, fundus photographs to evaluate retinal vascularization, and optical coherence tomographs (OCT) to evaluate retinal thickness. We also performed histological examination of hematoxylin- and eosin-stained retinal sections as well as sections labeled in situ by the terminal dUTP nick end labeling (TUNEL) method. RESULTS ERG findings showed that as early as 2 months of age, cone function was lost while rod function was preserved. However, by 9 months of age, both cone and rod functions could not be detected. Functional visual assessment based on the ability to avoid obstacles showed that vision was retained up to the age of 11 months. Both OCT and histopathology studies revealed a progressive thinning of the outer nuclear layer (ONL) over the first 2 years of age. TUNEL labeling identified apoptotic photoreceptor cell death as the cause of this thinning of the ONL. CONCLUSIONS A treatment strategy should consist in initiating gene therapy as early as possible after birth to prevent or delay the loss of rod function. In the MLHD, successful subretinal delivery of a therapeutic vector is feasible at 2 months of age and may prevent or delay the loss of rod function.
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Affiliation(s)
| | - Lyse Libeau
- INSERM UMR 649, CHU-Hôtel Dieu, Nantes, France
| | | | | | | | | | | | - Cathryn Mellersh
- Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk, UK
| | | | - Yan Cherel
- INRA UMR 703, Ecole Nationale Vétérinaire de Nantes, Nantes, France
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Gorden NT, Arts HH, Parisi MA, Coene KLM, Letteboer SJF, van Beersum SEC, Mans DA, Hikida A, Eckert M, Knutzen D, Alswaid AF, Ozyurek H, Dibooglu S, Otto EA, Liu Y, Davis EE, Hutter CM, Bammler TK, Farin FM, Dorschner M, Topçu M, Zackai EH, Rosenthal P, Owens KN, Katsanis N, Vincent JB, Hildebrandt F, Rubel EW, Raible DW, Knoers NVAM, Chance PF, Roepman R, Moens CB, Glass IA, Doherty D. CC2D2A is mutated in Joubert syndrome and interacts with the ciliopathy-associated basal body protein CEP290. Am J Hum Genet 2008; 83:559-71. [PMID: 18950740 DOI: 10.1016/j.ajhg.2008.10.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 10/01/2008] [Accepted: 10/02/2008] [Indexed: 12/18/2022] Open
Abstract
Joubert syndrome and related disorders (JSRD) are primarily autosomal-recessive conditions characterized by hypotonia, ataxia, abnormal eye movements, and intellectual disability with a distinctive mid-hindbrain malformation. Variable features include retinal dystrophy, cystic kidney disease, and liver fibrosis. JSRD are included in the rapidly expanding group of disorders called ciliopathies, because all six gene products implicated in JSRD (NPHP1, AHI1, CEP290, RPGRIP1L, TMEM67, and ARL13B) function in the primary cilium/basal body organelle. By using homozygosity mapping in consanguineous families, we identify loss-of-function mutations in CC2D2A in JSRD patients with and without retinal, kidney, and liver disease. CC2D2A is expressed in all fetal and adult tissues tested. In ciliated cells, we observe localization of recombinant CC2D2A at the basal body and colocalization with CEP290, whose cognate gene is mutated in multiple hereditary ciliopathies. In addition, the proteins can physically interact in vitro, as shown by yeast two-hybrid and GST pull-down experiments. A nonsense mutation in the zebrafish CC2D2A ortholog (sentinel) results in pronephric cysts, a hallmark of ciliary dysfunction analogous to human cystic kidney disease. Knockdown of cep290 function in sentinel fish results in a synergistic pronephric cyst phenotype, revealing a genetic interaction between CC2D2A and CEP290 and implicating CC2D2A in cilium/basal body function. These observations extend the genetic spectrum of JSRD and provide a model system for studying extragenic modifiers in JSRD and other ciliopathies.
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Affiliation(s)
- Nicholas T Gorden
- Division of Genetics and Developmental Medicine, Department of Pediatrics, School of Medicine, University of Washington, Seattle, WA 98195, USA
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Li Y, Wang H, Peng J, Gibbs RA, Lewis RA, Lupski JR, Mardon G, Chen R. Mutation survey of known LCA genes and loci in the Saudi Arabian population. Invest Ophthalmol Vis Sci 2008; 50:1336-43. [PMID: 18936139 DOI: 10.1167/iovs.08-2589] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The purpose of this study was to perform a comprehensive survey of all known Leber congenital amaurosis (LCA) genes and loci in a collection of 37 consanguineous LCA families from Saudi Arabia. METHODS Direct PCR and sequencing were used to screen 13 known LCA genes (GUCY2D, CRX, RPE65, TULP1, AIPL1, CRB1, RPGRIP1, LRAT, RDH12, IMPDH1, CEP290, RD3, LCA5). In addition, families without mutations identified were further screened with STR markers around these 13 known LCA genes and two loci. RESULTS Disease-causing mutations were identified in nine of the 37 families: five in TULP1, two in CRB1, one in RPE65, and one in GUCY2D. Mutations in known genes only accounted for 24% of the Saudi families--much less than what has been observed in the European population (65%). Phenotype-genotype analysis was carried out to investigate the LCA disease penetrance for all families whose mutations identified. All identified mutations were found to segregate perfectly with the disease phenotype. On the other hand, severity of the disease varies for different patients carrying the same mutation and even within the same family. Furthermore, based on homozygosity mapping with both STR and SNP markers, one family is likely to map to the LCA3 locus. CONCLUSIONS These results underscore the importance of studying LCA disease families from different ethnic backgrounds to identify additional novel LCA disease genes. Furthermore, perfect segregation between mutation and disease indicates that LCA is fully penetrant. However, phenotypic variations among patients carrying the same mutation suggest that at least some of the variations in the clinical phenotype is due to modification from the genetic background, environment, or other factors.
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Affiliation(s)
- Yumei Li
- Departments of Molecular and Human Genetics
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127
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van Wijk E, Kersten FFJ, Kartono A, Mans DA, Brandwijk K, Letteboer SJF, Peters TA, Märker T, Yan X, Cremers CWRJ, Cremers FPM, Wolfrum U, Roepman R, Kremer H. Usher syndrome and Leber congenital amaurosis are molecularly linked via a novel isoform of the centrosomal ninein-like protein. Hum Mol Genet 2008; 18:51-64. [PMID: 18826961 DOI: 10.1093/hmg/ddn312] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Usher syndrome (USH) and Leber congenital amaurosis (LCA) are autosomal recessive disorders resulting in syndromic and non-syndromic forms of blindness. In order to gain insight into the pathogenic mechanisms underlying retinal degeneration, we searched for interacting proteins of USH2A isoform B (USH2A(isoB)) and the LCA5-encoded protein lebercilin. We identified a novel isoform of the centrosomal ninein-like protein, hereby named Nlp isoform B (Nlp(isoB)), as a common interactor. Although we identified the capacity of this protein to bind calcium with one of its three EF-hand domains, the interacton with USH2A(isoB) did not depend on this. Upon expression in ARPE-19 cells, recombinant Nlp(isoB), lebercilin and USH2A(isoB) were all found to co-localize at the centrosomes. Staining of retinal sections with specific antibodies against all three proteins revealed their co-localization at the basal bodies of the photoreceptor-connecting cilia. Based on this subcellular localization and the nature of their previously identified binding partners, we hypothesize that the pathogenic mechanisms for LCA and USH show significant overlap and involve defects in ciliogenesis, cilia maintenance and intraflagellar and/or microtubule-based transport. The direct association of Nlp(isoB) with USH2A(isoB) and lebercilin indicates that Nlp can be considered as a novel candidate gene for USH, LCA and allied retinal ciliopathies.
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Affiliation(s)
- Erwin van Wijk
- Department of Otorhinolaryngology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Wiik AC, Wade C, Biagi T, Ropstad EO, Bjerkås E, Lindblad-Toh K, Lingaas F. A deletion in nephronophthisis 4 (NPHP4) is associated with recessive cone-rod dystrophy in standard wire-haired dachshund. Genome Res 2008; 18:1415-21. [PMID: 18687878 DOI: 10.1101/gr.074302.107] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cone-rod dystrophy is a retinal degenerative disorder occurring naturally in man and dog. Here we identify a novel gene for early-onset cone-rod dystrophy in the wire-haired dachshund. For the first time, we use genome-wide association-based Sibling Transmission Disequilibrium Test (sibTDT) analysis of only 13 discordant sib-pairs to identify a single significantly associated 6.5-Mb region (PrawTDT = 4.8 x 10(-5), PgenomeTDT = 6 x 10(-4)) on canine chromosome 5, containing more than 70 genes. Segregation studies using microsatellites in the candidate region including additional meiosis supported the sibTDT analysis but could not further reduce the area. Candidate gene resequencing identified a 180-bp deletion in exon/intron 5 of NPHP4 (nephronophthisis 4, also known as nephroretinin). RT-PCR analysis of NPHP4 in cases and controls showed exon skipping of exon 5, resulting in a truncated protein that retains the binding domain interacting with nephronophthisis 1 (also known as nephrocystin-1) in the kidney but lacks the domain interacting with RPGRIP1 in retina. We suggest that this deletion in the canine NPHP4 gene is the cause of cone-rod dystrophy in the standard wire-haired dachshund. In humans, mutations in NPHP4 have been associated with simultaneous eye and kidney disease. Here we describe the first naturally occurring mutation in NPHP4 without additional kidney disease. Further studies will permit elucidation of the complex molecular mechanism of this retinopathy and the development of potential therapies.
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Affiliation(s)
- Anne Caroline Wiik
- Department of Basic Sciences and Aquatic Medicine, Division of Genetics, Norwegian School of Veterinary Science, 0033 Oslo, Norway
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Seong MW, Kim SY, Yu YS, Hwang JM, Kim JY, Park SS. Molecular characterization of Leber congenital amaurosis in Koreans. Mol Vis 2008; 14:1429-36. [PMID: 18682808 PMCID: PMC2493025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Accepted: 06/18/2008] [Indexed: 11/18/2022] Open
Abstract
PURPOSE Leber congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy, and invariably leads to blindness. LCA is a genetically and clinically heterogenous disorder. Although more than nine genes have been found to be associated with LCA, they only account for about half of LCA cases. We performed a comprehensive mutational analysis on nine known genes in 20 unrelated patients to investigate the genetic cause of LCA in Koreans. METHODS All exons and flanking regions of the nine genes (AIPL1, CRB1, CRX, GUCY2D, RDH12, RPE65, RPGRIP1, LRAT, and TULP1) were analyzed by direct sequencing. We also screened our patients for the common CEP290: c.2991+1655A>G mutation found in Caucasian. RESULTS Six different mutations including four novel ones were identified in three patients (15.0%): one frameshift, one nonsense, one splicing, and three missense mutations. These patients were compound heterozygotes and harbored two different mutations in CRB1, RPE65, and RPGRIP1, respectively. We identified three novel unclassified missense variants in RPGRIP1 of the three patients. These patients were heterozygous for each variant and did not have a large deletion or duplication in the same gene. CONCLUSIONS This comprehensive mutational analysis shows marked genetic heterogeneity in Korean LCA patients and reveals a mutation spectrum that differs from those previously reported. In turn, this suggests that a different strategy should be used for the molecular diagnosis of LCA in Koreans.
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Affiliation(s)
- Moon-Woo Seong
- Department of Laboratory Medicine, Seoul National University Hospital and Clinical Research Institute, Seoul, Korea;,Department of Laboratory Medicine, National Cancer Center, Goyang, Korea
| | - Seong Yeon Kim
- Department of Laboratory Medicine, Seoul National University Hospital and Clinical Research Institute, Seoul, Korea
| | - Young Suk Yu
- Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea
| | - Jeong-Min Hwang
- Department of Ophthalmology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Ji Yeon Kim
- Department of Laboratory Medicine, Seoul National University Hospital and Clinical Research Institute, Seoul, Korea
| | - Sung Sup Park
- Department of Laboratory Medicine, Seoul National University Hospital and Clinical Research Institute, Seoul, Korea
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130
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A study of candidate genes for day blindness in the standard wire haired dachshund. BMC Vet Res 2008; 4:23. [PMID: 18593457 PMCID: PMC2494547 DOI: 10.1186/1746-6148-4-23] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Accepted: 07/01/2008] [Indexed: 01/21/2023] Open
Abstract
Background A genetic study was performed to identify candidate genes associated with day blindness in the standard wire haired dachshund. Based on a literature review of diseases in dogs and human with phenotypes similar to day blindness, ten genes were selected and evaluated as potential candidate genes associated with day blindness in the breed. Results Three of the genes, CNGB3, CNGA3 and GNAT2, involved in cone degeneration and seven genes and loci, ABCA4, RDH5, CORD8, CORD9, RPGRIP1, GUCY2D and CRX, reported to be involved in cone-rod dystrophies were studied. Polymorphic markers at each of the candidate loci were studied in a family with 36 informative offspring. The study revealed a high frequency of recombinations between the candidate marker alleles and the disease. Conclusion Since all of the markers were at the exact position of the candidate loci, and several recombinations were detected for each of the loci, all ten genes were excluded as causal for this canine, early onset cone-rod dystrophy. The described markers may, however, be useful to screen other canine resource families segregating eye diseases for association to the ten genes.
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131
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Brancati F, Travaglini L, Zablocka D, Boltshauser E, Accorsi P, Montagna G, Silhavy JL, Barrano G, Bertini E, Emma F, Rigoli L, Dallapiccola B, Gleeson JG, Valente EM. RPGRIP1L mutations are mainly associated with the cerebello-renal phenotype of Joubert syndrome-related disorders. Clin Genet 2008; 74:164-70. [PMID: 18565097 DOI: 10.1111/j.1399-0004.2008.01047.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Joubert syndrome-related disorders (JSRDs) are autosomal recessive pleiotropic conditions sharing a peculiar cerebellar and brainstem malformation known as the 'molar tooth sign' (MTS). Recently, mutations in a novel ciliary gene, RPGRIP1L, have been shown to cause both JSRDs and Meckel-Gruber syndrome. We searched for RPGRIP1L mutations in 120 patients with proven MTS and phenotypes representative of all JSRD clinical subgroups. Two homozygous mutations, the previously reported p.T615P in exon 15 and the novel c.2268_2269delA in exon 16, were detected in 2 of 16 families with cerebello-renal presentation ( approximately 12%). Conversely, no pathogenic changes were found in patients with other JSRD phenotypes, suggesting that RPGRIP1L mutations are largely confined to the cerebello-renal subgroup, while they overall represent a rare cause of JSRD (<2%).
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Affiliation(s)
- F Brancati
- Istituto di Ricovero e Cura a Carattere Scientifico, CSS-Mendel Institute, Rome, Italy
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132
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den Hollander AI, Roepman R, Koenekoop RK, Cremers FPM. Leber congenital amaurosis: genes, proteins and disease mechanisms. Prog Retin Eye Res 2008; 27:391-419. [PMID: 18632300 DOI: 10.1016/j.preteyeres.2008.05.003] [Citation(s) in RCA: 556] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Leber congenital amaurosis (LCA) is the most severe retinal dystrophy causing blindness or severe visual impairment before the age of 1 year. Linkage analysis, homozygosity mapping and candidate gene analysis facilitated the identification of 14 genes mutated in patients with LCA and juvenile retinal degeneration, which together explain approximately 70% of the cases. Several of these genes have also been implicated in other non-syndromic or syndromic retinal diseases, such as retinitis pigmentosa and Joubert syndrome, respectively. CEP290 (15%), GUCY2D (12%), and CRB1 (10%) are the most frequently mutated LCA genes; one intronic CEP290 mutation (p.Cys998X) is found in approximately 20% of all LCA patients from north-western Europe, although this frequency is lower in other populations. Despite the large degree of genetic and allelic heterogeneity, it is possible to identify the causative mutations in approximately 55% of LCA patients by employing a microarray-based, allele-specific primer extension analysis of all known DNA variants. The LCA genes encode proteins with a wide variety of retinal functions, such as photoreceptor morphogenesis (CRB1, CRX), phototransduction (AIPL1, GUCY2D), vitamin A cycling (LRAT, RDH12, RPE65), guanine synthesis (IMPDH1), and outer segment phagocytosis (MERTK). Recently, several defects were identified that are likely to affect intra-photoreceptor ciliary transport processes (CEP290, LCA5, RPGRIP1, TULP1). As the eye represents an accessible and immune-privileged organ, it appears to be uniquely suitable for human gene replacement therapy. Rodent (Crb1, Lrat, Mertk, Rpe65, Rpgrip1), avian (Gucy2D) and canine (Rpe65) models for LCA and profound visual impairment have been successfully corrected employing adeno-associated virus or lentivirus-based gene therapy. Moreover, phase 1 clinical trials have been carried out in humans with RPE65 deficiencies. Apart from ethical considerations inherently linked to treating children, major obstacles for the treatment of LCA could be the putative developmental deficiencies in the visual cortex in persons blind from birth (amblyopia), the absence of sufficient numbers of viable photoreceptor or RPE cells in LCA patients, and the unknown and possibly toxic effects of overexpression of transduced genes. Future LCA research will focus on the identification of the remaining causal genes, the elucidation of the molecular mechanisms of disease in the retina, and the development of gene therapy approaches for different genetic subtypes of LCA.
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Affiliation(s)
- Anneke I den Hollander
- Department of Human Genetics & Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
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133
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Ciliary syndromes and treatment. Pathol Res Pract 2008; 204:77-88. [PMID: 18312782 DOI: 10.1016/j.prp.2007.10.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2006] [Revised: 10/26/2007] [Accepted: 10/30/2007] [Indexed: 12/21/2022]
Abstract
Abnormal visceral patterning has been known for centuries. However, it has not been associated with ciliary dysfunction until recently. Overlapping clinical entities including situs inversus, certain infertility disorders, as well as chronic respiratory infections have their roots in abnormal ciliary function. Current research focuses on causative factors and genes involved in signal transduction pathways that define ciliary function and structure, as well as treatment. In this review, attempts are made to outline selected, yet key topics related to ciliary function in health and disease.
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134
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Abstract
Over the last decade there have been major advances in our understanding of the molecular pathology of inherited retinal dystrophies. This paper reviews recent advances in the identification of genetic mutations underlying infantile-onset inherited retinal disorders and considers how this knowledge may lead to novel therapeutic approaches.
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Affiliation(s)
- P Moradi
- Institute of Ophthalmology UCL, London, UK
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135
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Arts HH, Cremers FPM, Knoers NVAM, Roepman R. Focus on molecules: RPGRIP1. Exp Eye Res 2008; 88:332-3. [PMID: 18538322 DOI: 10.1016/j.exer.2008.03.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 03/27/2008] [Accepted: 03/28/2008] [Indexed: 11/27/2022]
Affiliation(s)
- Heleen H Arts
- Department of Human Genetics and Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, HB Nijmegen, The Netherlands
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136
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Shu X, McDowall E, Brown AF, Wright AF. The human retinitis pigmentosa GTPase regulator gene variant database. Hum Mutat 2008; 29:605-8. [DOI: 10.1002/humu.20733] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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137
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Abstract
Leber congenital amaurosis (LCA) is a congenital retinal dystrophy that was first described almost 150 years ago. LCA still remains an important cause of blindness with about 20% of children in schools for the blind being affected by it. LCA has genetic heterogeneity and the study of this disease is elucidating the genetics and molecular interactions involved in the development of the retina. This paper reviews the clinical history of the disease since it was first described. We further discuss the differential diagnosis of the disease and the difficulties encountered in making the diagnosis. We also review the genetics of the disease and the role of future therapies.
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Affiliation(s)
- Ednan Ahmed
- Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA
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138
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Mans DA, Voest EE, Giles RH. All along the watchtower: is the cilium a tumor suppressor organelle? Biochim Biophys Acta Rev Cancer 2008; 1786:114-25. [PMID: 18343234 DOI: 10.1016/j.bbcan.2008.02.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 02/10/2008] [Accepted: 02/14/2008] [Indexed: 01/09/2023]
Abstract
Cilia or flagella have been around since almost the beginning of life, and have now developed specialized cell-type specific functions from locomotion to acting as environmental sensors participating in cell signalling. Genetic defects affecting cilia result in a myriad of pathological instances, including infertility, obesity, blindness, deafness, skeletal malformations, and lung problems. However, the consistency in which the common kidney cyst is coupled with cilia dysfunction has raised interest in the possibility that ciliary dysfunction might contribute to other neoplasms as well. A suite of recent papers convincingly linking cilia to hedgehog signalling, platelet-derived growth factor signalling, Wnt signalling and the von Hippel-Lindau tumor suppressor protein has rapidly expanded the knowledge base connecting cilia to cancer. We propose that these data support the notion of the cilium as a cellular Watchtower, whose absence can be an initiating event in neoplastic growth. Furthermore, we predict that we are just now seeing the tip of the iceberg, and that the list of cancers associated with altered ciliary signalling will grow exponentially in the next few years.
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Affiliation(s)
- Dorus A Mans
- Department of Medical Oncology, University Medical Center Utrecht, The Netherlands
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139
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Abstract
The recent identification of RPGRIP1L as a Joubert syndrome gene brings the total of known genes to five. Three of these are also associated with the lethal Meckel syndrome, and two with Senior-Løken syndrome; both of these disorders share Joubert syndrome phenotypes, illustrating the genetic complexity of this.
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Affiliation(s)
- P C Harris
- Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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140
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Abstract
While the functions of many of the proteins located in or associated with the photoreceptor cilia are poorly understood, disruption of the function of these proteins may result in a wide variety of phenotypes ranging from isolated retinal degeneration to more pleiotropic phenotypes. Systemic findings include neurosensory hearing loss, developmental delay, situs-inversus, infertility, disorders of limb and digit development, obesity, kidney disease, liver disease, and respiratory disease. The concept of "retinal ciliopathies" brings to attention the importance of further molecular analysis of this organelle as well as provides a potential common target for therapies for these disorders. The retinal ciliopathies include retinitis pigmentosa, macular degeneration, cone-dystrophy, cone-rod dystrophy, Leber congenital amaurosis, as well as retinal degenerations associated with Usher syndrome, primary ciliary dyskinesia, Senior-Loken syndrome, Joubert syndrome, Bardet-Biedl syndrome, Laurence-Moon syndrome, McKusick-Kaufman syndrome, and Biemond syndrome. Mutations for these disorders have been found in retinitis pigmentosa-1 (RP1), retinitis pigmentosa GTPase regulator (RPGR), retinitis pigmentosa GTPase regulator interacting protein (RPGR-IP), as well as the Usher, Bardet-Biedl, and nephronophthisis genes. Other systemic disorders associated with retinal degenerations that may also involve ciliary abnormalities include: Alstrom, Edwards-Sethi, Ellis-van Creveld, Jeune, Meckel-Gruber, Orofaciodigital Type 9, and Gurrieri syndromes. Understanding these conditions as ciliopathies may help the ophthalmologist to recognize associations between seemingly unrelated diseases and have a high degree of suspicion that a systemic finding may be present.
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Affiliation(s)
- N A Adams
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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141
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Stone EM. Leber congenital amaurosis - a model for efficient genetic testing of heterogeneous disorders: LXIV Edward Jackson Memorial Lecture. Am J Ophthalmol 2007; 144:791-811. [PMID: 17964524 DOI: 10.1016/j.ajo.2007.08.022] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 07/26/2007] [Accepted: 08/07/2007] [Indexed: 01/24/2023]
Abstract
PURPOSE To critically evaluate our experience in molecular testing of Leber congenital amaurosis (LCA) and to use this information to devise a general approach to heterogeneous recessive disorders. Careful clinical and molecular characterization of large cohorts of patients affected with inherited eye diseases will be an essential step in the development of effective therapy for these diseases, especially when the therapy involves gene replacement. DESIGN A molecular genetic case-control study. METHODS Six hundred forty-two unrelated individuals with the clinical diagnosis of LCA and 200 unrelated control individuals were screened for disease-causing sequence variations in eight genes using various combinations of single-strand conformational polymorphism analysis (SSCP), automated DNA sequencing, multiplex allele-specific ligation analysis (SNPlex), and high-density solid-phase single nucleotide polymorphism genotyping. RESULTS Four hundred forty instances of 189 different disease-causing sequence variations were observed in this study, 98 of which have not been previously reported. One hundred forty-six of the 189 variations (77%) were observed in only a single individual. The observed variations were not evenly distributed among the LCA patients or among the eight genes. Empirical analysis of this uneven distribution was used to devise a multi-platform mutation detection strategy that is four times more efficient than a more conventional strategy of completely sequencing all of the coding regions of all LCA genes in all subjects. Hardy-Weinberg analysis of the observed mutations suggests that these eight genes are collectively responsible for about 70% of the cases of LCA in North America. The carrier frequency of the most common LCA allele (an intron 26 variation in CEP290) was found to be 2/3,248, which suggests that the overall prevalence of LCA in this population is about 1/81,000. An allele-specific ligation assay (SNPlex) was designed to detect 68 of the most common LCA-causing alleles, and semi-quantitative analysis of the data from this assay also revealed examples of gene deletion and isodisomy in the cohort. CONCLUSIONS The data demonstrates that a tiered screening strategy combining allele-specific detection with automated DNA sequencing can increase the efficiency of autosomal recessive mutation detection four-fold when compared with DNA sequencing alone. However, the very high rate of unique mutations observed in this study (77%) suggests that DNA sequencing will remain an important part of the overall strategy if high sensitivity is to be achieved.
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142
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Koenekoop RK, Cremers FPM, den Hollander AI. Leber congenital amaurosis: ciliary proteins on the move. Ophthalmic Genet 2007; 28:111-2. [PMID: 17896308 DOI: 10.1080/13816810701537457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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143
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Preising MN, Paunescu K, Friedburg C, Lorenz B. [Genetic and clinical heterogeneity in LCA patients. The end of uniformity]. Ophthalmologe 2007; 104:490-8. [PMID: 17525851 DOI: 10.1007/s00347-007-1533-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND Leber congenital amaurosis (LCA) usually describes patients with severely reduced vision due to a retinal dystrophy in early childhood. METHODS In 135 families in a case series with severely reduced vision due to a retinal dystrophy in early childhood a complete ophthalmologic examination was extended by two-color threshold perimetry, fundus autofluorescence (FAF), und optical coherence tomography (OCT). Mutation screening included AIPL1, CRB1, CRX, GUCY2D, LRAT, RPE65, RPGRIP, and TULP1. RESULTS GUCY2D mutations caused the most severe phenotype with severely reduced vision from birth but unremarkable fundus appearance. RPE65 mutations were correlated with an obvious lack of FAF. CRB1 mutations showed a significantly thickened retina on OCT. CRX mutations were associated with a progressive form of cone-rod dystrophy. CONCLUSION A genotype-phenotype correlation for selected genes allows an optimized strategy for the molecular genetic work-up.
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Affiliation(s)
- M N Preising
- Abt. für Kinderophthalmologie, Strabismologie und Ophthalmogenetik, Klinikum der Universität Regensburg, 93042, Regensburg
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144
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Neidhardt J, Glaus E, Barthelmes D, Zeitz C, Fleischhauer J, Berger W. Identification and characterization of a novel RPGR isoform in human retina. Hum Mutat 2007; 28:797-807. [PMID: 17405150 DOI: 10.1002/humu.20521] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Retinitis pigmentosa (RP) constitutes a major cause of blindness and the Retinitis Pigmentosa GTPase Regulator (RPGR) gene accounts for up to 80% of all X-linked RP cases. A novel isoform of RPGR, expressed in the human retina, was identified and characterized. It truncates the Regulator of Chromosome Condensation 1 (RCC1) homologous protein domain (RCC1h) of RPGR and mediates the formation of isoform-specific complexes with the RPGR-interacting protein 1 (RPGRIP1). Immunohistochemistry localized the novel RPGR isoform predominantly to inner segments of cone photoreceptors, where it colocalizes with RPGRIP1 in the human retina. In a patient with a mild RP phenotype, we identified a nucleotide substitution in a splicing regulator, which leads to 3.5 times higher levels of the transcripts coding for the novel RPGR isoform. The nucleotide substitution affects regulated alternative splicing of the novel RPGR isoform and suggests a tight adjustment of splicing as a prerequisite for proper function of photoreceptors.
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Affiliation(s)
- John Neidhardt
- Division of Medical Molecular Genetics and Gene Diagnostics, Institute of Medical Genetics, University of Zurich, Zurich, Switzerland.
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145
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Guyon R, Pearce-Kelling SE, Zeiss CJ, Acland GM, Aguirre GD. Analysis of six candidate genes as potential modifiers of disease expression in canine XLPRA1, a model for human X-linked retinitis pigmentosa 3. Mol Vis 2007; 13:1094-105. [PMID: 17653054 PMCID: PMC2779147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Canine X-linked progressive retinal atrophy (XLPRA) is caused by mutations in RPGR exon ORF15, which is also a mutation hotspot in human X-linked retinitis pigmentosa 3 (RP3). The XLPRA1 form of disease has shown extensive phenotypic variability in a colony of dogs that all inherited the same mutant X-chromosome. This variability in onset and severity makes XLPRA1 a valuable model to use to identify genes influencing photoreceptors degeneration in dog and to elucidate molecular mechanisms underlying RP in its human homolog. In this study, RPGRIP1, RANBP2, NPM1, PDE6D, NPHP5, and ABCA4 genes were selected on the basis of interaction with RPGR or RPGRIP1 or their implication in related retinal diseases, and were investigated as candidate genetic modifiers of XLPRA1. METHODS A pedigree derived from an affected male dog outcrossed to unrelated normal mix bred or purebred females was used. Morphologic examination revealed phenotypic variability in the affected dogs characterized as mild, moderate, or severe. Single nucleotide polymorphisms (SNPs) and indel-containing markers spanning the entire genes were designed, based on the canine sequence and the Broad Institute SNP library, and genotyped on the pedigree. For each candidate gene, haplotypes were identified and their frequencies in severely and moderately affected dogs were compared to detect a putative correlation between a gene-specific haplotype(s), and severity level of the disease. Primers were derived from expressed sequence tags (ESTs) and predicted transcripts to assess the relative retinal expression of the six genes of interest in normal and affected retinas of different ages. RESULTS Four to seven haplotypes per gene were identified. None of the haplotypes of RPGRIP1, NPM1, PDE6D, NPHP5, RANBP2, and ABCA4 were found to co-segregate with the moderate or severe phenotype. No significant difference in the retinal expression levels of the candidate genes was observed between normal and affected dogs. CONCLUSIONS The haplotype distribution of RPGRIP1, NPM1, PDE6D, NPHP5, RANBP2, and ABCA4 suggests these genes are not modifiers of the disease phenotype observed in the XLPRA1 pedigree. The RPGRORF15 stop mutation does not affect the retinal expression of these genes at the mRNA level in the pre-degenerate stage of disease, but no conclusions can be made at this time about changes that may occur at the protein level.
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Affiliation(s)
- Richard Guyon
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
| | - Susan E. Pearce-Kelling
- James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY
| | - Caroline J. Zeiss
- Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT
| | - Gregory M. Acland
- James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY
| | - Gustavo D. Aguirre
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
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146
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Abstract
The field of molecular genetics is evolving to encompass techniques that are directly relevant to the diagnosis and management of eye disease. Therefore, pediatric ophthalmologists must have a knowledge base that includes basic genetic concepts and their application to current clinical care.
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Affiliation(s)
- Kathryn Bollinger
- Department of Pediatric Ophthalmology and Strabismus, Cole Eye Institute, Cleveland, Ohio 44195, USA
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147
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Delous M, Baala L, Salomon R, Laclef C, Vierkotten J, Tory K, Golzio C, Lacoste T, Besse L, Ozilou C, Moutkine I, Hellman NE, Anselme I, Silbermann F, Vesque C, Gerhardt C, Rattenberry E, Wolf MTF, Gubler MC, Martinovic J, Encha-Razavi F, Boddaert N, Gonzales M, Macher MA, Nivet H, Champion G, Berthélémé JP, Niaudet P, McDonald F, Hildebrandt F, Johnson CA, Vekemans M, Antignac C, Rüther U, Schneider-Maunoury S, Attié-Bitach T, Saunier S. The ciliary gene RPGRIP1L is mutated in cerebello-oculo-renal syndrome (Joubert syndrome type B) and Meckel syndrome. Nat Genet 2007; 39:875-81. [PMID: 17558409 DOI: 10.1038/ng2039] [Citation(s) in RCA: 377] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Accepted: 04/04/2007] [Indexed: 12/15/2022]
Abstract
Cerebello-oculo-renal syndrome (CORS), also called Joubert syndrome type B, and Meckel (MKS) syndrome belong to the group of developmental autosomal recessive disorders that are associated with primary cilium dysfunction. Using SNP mapping, we identified missense and truncating mutations in RPGRIP1L (KIAA1005) in both CORS and MKS, and we show that inactivation of the mouse ortholog Rpgrip1l (Ftm) recapitulates the cerebral, renal and hepatic defects of CORS and MKS. In addition, we show that RPGRIP1L colocalizes at the basal body and centrosomes with the protein products of both NPHP6 and NPHP4, known genes associated with MKS, CORS and nephronophthisis (a related renal disorder and ciliopathy). In addition, the RPGRIP1L missense mutations found in CORS individuals diminishes the interaction between RPGRIP1L and nephrocystin-4. Our findings show that mutations in RPGRIP1L can cause the multiorgan phenotypic abnormalities found in CORS or MKS, which therefore represent a continuum of the same underlying disorder.
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Affiliation(s)
- Marion Delous
- Institut National de la Santé et de la Recherche Médicale (INSERM) U-574, Hôpital Necker-Enfants Malades, 75015 Paris, France
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148
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Arts HH, Doherty D, van Beersum SEC, Parisi MA, Letteboer SJF, Gorden NT, Peters TA, Märker T, Voesenek K, Kartono A, Ozyurek H, Farin FM, Kroes HY, Wolfrum U, Brunner HG, Cremers FPM, Glass IA, Knoers NVAM, Roepman R. Mutations in the gene encoding the basal body protein RPGRIP1L, a nephrocystin-4 interactor, cause Joubert syndrome. Nat Genet 2007; 39:882-8. [PMID: 17558407 DOI: 10.1038/ng2069] [Citation(s) in RCA: 250] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 05/14/2007] [Indexed: 11/09/2022]
Abstract
Protein-protein interaction analyses have uncovered a ciliary and basal body protein network that, when disrupted, can result in nephronophthisis (NPHP), Leber congenital amaurosis, Senior-Løken syndrome (SLSN) or Joubert syndrome (JBTS). However, details of the molecular mechanisms underlying these disorders remain poorly understood. RPGRIP1-like protein (RPGRIP1L) is a homolog of RPGRIP1 (RPGR-interacting protein 1), a ciliary protein defective in Leber congenital amaurosis. We show that RPGRIP1L interacts with nephrocystin-4 and that mutations in the gene encoding nephrocystin-4 (NPHP4) that are known to cause SLSN disrupt this interaction. RPGRIP1L is ubiquitously expressed, and its protein product localizes to basal bodies. Therefore, we analyzed RPGRIP1L as a candidate gene for JBTS and identified loss-of-function mutations in three families with typical JBTS, including the characteristic mid-hindbrain malformation. This work identifies RPGRIP1L as a gene responsible for JBTS and establishes a central role for cilia and basal bodies in the pathophysiology of this disorder.
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Affiliation(s)
- Heleen H Arts
- Department of Human Genetics, Radboud University Nijmegen Medical Centre and Nijmegen Centre for Molecular Life Sciences, 6500 HB Nijmegen, The Netherlands
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149
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Jacobson SG, Cideciyan AV, Aleman TS, Sumaroka A, Schwartz SB, Roman AJ, Stone EM. Leber Congenital Amaurosis Caused by an RPGRIP1 Mutation Shows Treatment Potential. Ophthalmology 2007; 114:895-8. [PMID: 17306875 DOI: 10.1016/j.ophtha.2006.10.028] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 10/04/2006] [Accepted: 10/05/2006] [Indexed: 02/07/2023] Open
Abstract
PURPOSE To determine the treatment potential in Leber congenital amaurosis (LCA) resulting from an RPGRIP1 (retinitis pigmentosa GTPase regulating-interacting protein 1) mutation, a form of LCA with recent gene therapy success in an animal model. DESIGN Case report of a rare genetic eye disease investigated for intervention potential. PARTICIPANTS A 19-year-old man with LCA. METHODS We studied the retinal structure and function in an LCA patient with a novel homozygous Val1211Glu mutation in the RPGRIP1 gene using optical coherence tomography and colocalized dark-adapted thresholds. MAIN OUTCOME MEASURE Optical coherence tomography results. RESULTS Central retinal laminar architecture was preserved, and there was a measurable outer nuclear layer. The retained retinal structure corresponded to the region of visual sensitivity. With increasing eccentricity, there was no measurable visual function, and retinal laminar disorganization suggested a remodeling process. CONCLUSIONS The RPGRIP1-LCA patient has treatment potential for a gene replacement strategy if targeted to central, but not pericentral or peripheral, retina. The results differ from similarly studied RPE65-LCA and CRB1-LCA patients. Preclinical progress toward therapy in LCA patients warrants detailed structure-function studies in humans to determine feasibility and candidacy for clinical trials.
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Affiliation(s)
- Samuel G Jacobson
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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150
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Sweeney MO, McGee TL, Berson EL, Dryja TP. Low prevalence of lecithin retinol acyltransferase mutations in patients with Leber congenital amaurosis and autosomal recessive retinitis pigmentosa. Mol Vis 2007; 13:588-93. [PMID: 17438524 PMCID: PMC2669503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
PURPOSE To determine the the prevalence of pathogenic mutations in the gene encoding lecithin retinol acyltransferase (LRAT) in patients from North America with either Leber congenital amaurosis (LCA) or autosomal recessive retinitis pigmentosa (ARRP). METHODS Exon 1, exon 2, and the coding region of exon 3 of LRAT were PCR-amplified and directly sequenced from the leukocyte DNA of 82 unrelated patients with LCA and 190 unrelated patients with ARRP. RESULTS One isocoding change was found in this screen of LRAT (Glu114 GAG>GAA; c.342), and 5 other sequence changes were found in intronic or untranslated regions of the gene. None of these changes were predicted to affect the encoded protein and were therefore deemed non-pathogenic. CONCLUSIONS LRAT mutations are likely a rare cause of LCA among patients from North America.
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Affiliation(s)
- Meredith O Sweeney
- Ocular Molecular Genetics Institute and the Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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