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Sen S, Fabozzi L, Fujinami K, Fujinami-Yokokawa YU, Wright GA, Webster A, Mahroo O, Robson AG, Georgiou M, Michaelides M. IQCB1 (NPHP5)-Retinopathy: Clinical and Genetic Characterization and Natural History. Am J Ophthalmol 2024; 264:205-215. [PMID: 38522724 DOI: 10.1016/j.ajo.2024.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 03/04/2024] [Accepted: 03/11/2024] [Indexed: 03/26/2024]
Abstract
PURPOSE To describe the clinical and genetic features, and explore the natural history of retinopathy associated with IQCB1 variants in children and adults with retinopathy. DESIGN Retrospective cohort study at a single tertiary care referral center. METHODS The study recruited 19 patients with retinopathy, harboring likely disease-causing variants in IQCB1. Demographic data and clinical presentation, best corrected visual acuity (BCVA), fundus appearance, optical coherence tomography (OCT) and autofluorescence features, electroretinography (ERG) and molecular genetics are reported. RESULTS Ten patients had best corrected visual acuity better than 1.0 LogMAR, and BCVA remained stable till the last review. Seven patients had a vision of hand movements or worse in at least one eye at presentation. There was no correlation found between age of onset and severity of vision loss. Nine patients (47.4%) had a diagnosis of end-stage renal failure at presentation. The other 10 patients (52.6%) had a diagnosis of non-syndromic IQCB1-retinopathy and maintained normal renal function until the last follow-up. The mean age at diagnosis of renal failure was 26.3 ±19.8 years. OCT showed ellipsoid zone (EZ) disruption with foveal sparing in 8/13 patients. All patients had stable OCT findings. Full-field ERGs in four adults revealed a severe cone-rod dystrophy and three children had extinguished ERGs. We identified 17 IQCB1 variants, all predicted to cause loss of function. CONCLUSION IQCB1-retinopathy is a severe early-onset cone-rod dystrophy. The dissociation between severely decreased retinal function and relative preservation of retinal structure over a wide age window makes the disease a candidate for gene therapy.
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Affiliation(s)
- Sagnik Sen
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom
| | - Lorenzo Fabozzi
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom
| | - Kaoru Fujinami
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom; Laboratory of Visual Physiology, Division of Vision Research (K.F., Y.F.-Y.), National Institute of Sensory Organs, NHO Tokyo Medical Center, Tokyo, Japan
| | - Y U Fujinami-Yokokawa
- UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom; Laboratory of Visual Physiology, Division of Vision Research (K.F., Y.F.-Y.), National Institute of Sensory Organs, NHO Tokyo Medical Center, Tokyo, Japan; Department of Health Policy and Management (Y.F.-Y.), Keio University School of Medicine, Tokyo, Japan
| | - Genevieve A Wright
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom
| | - Andrew Webster
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom
| | - Omar Mahroo
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom
| | - Anthony G Robson
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom
| | - Michalis Georgiou
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom; Jones Eye Institute (M.G.), University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Michel Michaelides
- Moorfields Eye Hospital (S.S, L.F., K.F., G.W., A.W., O.M., A.R., M.G., M.MM), London, United Kingdom; UCL Institute of Ophthalmology (S.S., K.F., Y.F.-K., A.W., O.M., A.R., M.G., M.M.), University College London, London, United Kingdom.
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2
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Levy M, Elron E, Shohat M, Lifshitz S, Kahana S, Shani H, Grossman A, Amar S, Narkis G, Sagi-Dain L, Basel-Salmon L, Maya I. Exploring inheritance, and clinical penetrance of distal Xq28 duplication syndrome: insights from 47 new unpublished cases. J Hum Genet 2024; 69:337-343. [PMID: 38632380 PMCID: PMC11199134 DOI: 10.1038/s10038-024-01252-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Revised: 03/29/2024] [Accepted: 04/01/2024] [Indexed: 04/19/2024]
Abstract
BACKGROUND Distal Xq28 duplication, or int22h1/int22h2-mediated Xq28 duplication syndrome, leads to cognitive impairment, neurobehavioral issues, and facial dysmorphisms. Existing literature has limited information on clinical traits and penetrance. METHODS We identified cases of distal Xq28 duplication (chrX: 154,126,575-154,709,680, GRCh37/hg19) through a review of clinical records and microarray reports from five centers, encompassing both postnatal and prenatal cases, with no prior family knowledge of the duplication. RESULTS Our search found 47 cases across 26 families, with duplications ranging from 208 to 935 Kb. In total, 8 out of 26 index cases featured a 200-300 kb partial duplication, mainly from Armenian/Caucasian Jewish backgrounds. Most prenatal cases showed no major fetal ultrasound malformations. Of cases with known inheritance mode (15 out of 26), maternal inheritance was more common (80%). The study identified seven male carriers of the duplication from six unrelated families, indicating partial penetrance in males. CONCLUSION Our study provides key insights into distal Xq28 duplication. Most prenatal tests showed no major fetal ultrasound issues. Maternal inheritance was common, with unaffected mothers. In the postnatal group, a balanced gender distribution was observed. Among male family members, two fathers had ADHD, one was healthy, and one brother had mild symptoms, indicating partial penetrance in males.
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Affiliation(s)
- Michal Levy
- The Raphael Recanati Genetics Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel.
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
| | - Eyal Elron
- The Raphael Recanati Genetics Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Mordechai Shohat
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Maccabi Genetic Institute & Bioinformatics Unit, Sheba Cancer Research Center, Ramat Gan, Israel
| | - Shira Lifshitz
- Maccabi Genetic Institute & Bioinformatics Unit, Sheba Cancer Research Center, Ramat Gan, Israel
| | - Sarit Kahana
- The Raphael Recanati Genetics Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel
| | - Hagit Shani
- The Danek Gertner Institute of Human Genetics, Sheba Medical Center, Ramat Gan, Israel
| | - Anat Grossman
- The Danek Gertner Institute of Human Genetics, Sheba Medical Center, Ramat Gan, Israel
| | - Shirly Amar
- Genetic Institute, Soroka Medical Center & Ben Gurion University, Be'er Sheva, Israel
| | - Ginat Narkis
- Genetic Institute, Soroka Medical Center & Ben Gurion University, Be'er Sheva, Israel
| | - Lena Sagi-Dain
- Genetics Institute, Department of Obstetrics and Gynecology, Carmel Medical Center & The Ruth and Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Lina Basel-Salmon
- The Raphael Recanati Genetics Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Felsenstein Medical Research Center, Tel Aviv University, Tel Aviv, Israel
| | - Idit Maya
- The Raphael Recanati Genetics Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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3
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Kingdom R, Wright CF. Incomplete Penetrance and Variable Expressivity: From Clinical Studies to Population Cohorts. Front Genet 2022; 13:920390. [PMID: 35983412 PMCID: PMC9380816 DOI: 10.3389/fgene.2022.920390] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 06/09/2022] [Indexed: 12/20/2022] Open
Abstract
The same genetic variant found in different individuals can cause a range of diverse phenotypes, from no discernible clinical phenotype to severe disease, even among related individuals. Such variants can be said to display incomplete penetrance, a binary phenomenon where the genotype either causes the expected clinical phenotype or it does not, or they can be said to display variable expressivity, in which the same genotype can cause a wide range of clinical symptoms across a spectrum. Both incomplete penetrance and variable expressivity are thought to be caused by a range of factors, including common variants, variants in regulatory regions, epigenetics, environmental factors, and lifestyle. Many thousands of genetic variants have been identified as the cause of monogenic disorders, mostly determined through small clinical studies, and thus, the penetrance and expressivity of these variants may be overestimated when compared to their effect on the general population. With the wealth of population cohort data currently available, the penetrance and expressivity of such genetic variants can be investigated across a much wider contingent, potentially helping to reclassify variants that were previously thought to be completely penetrant. Research into the penetrance and expressivity of such genetic variants is important for clinical classification, both for determining causative mechanisms of disease in the affected population and for providing accurate risk information through genetic counseling. A genotype-based definition of the causes of rare diseases incorporating information from population cohorts and clinical studies is critical for our understanding of incomplete penetrance and variable expressivity. This review examines our current knowledge of the penetrance and expressivity of genetic variants in rare disease and across populations, as well as looking into the potential causes of the variation seen, including genetic modifiers, mosaicism, and polygenic factors, among others. We also considered the challenges that come with investigating penetrance and expressivity.
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Affiliation(s)
- Rebecca Kingdom
- Institute of Biomedical and Clinical Science, Royal Devon & Exeter Hospital, University of Exeter Medical School, Exeter, United Kingdom
| | - Caroline F Wright
- Institute of Biomedical and Clinical Science, Royal Devon & Exeter Hospital, University of Exeter Medical School, Exeter, United Kingdom
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4
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Birtel J, Spital G, Book M, Habbig S, Bäumner S, Riehmer V, Beck BB, Rosenkranz D, Bolz HJ, Dahmer-Heath M, Herrmann P, König J, Charbel Issa P. NPHP1 gene-associated nephronophthisis is associated with an occult retinopathy. Kidney Int 2021; 100:1092-1100. [PMID: 34153329 DOI: 10.1016/j.kint.2021.06.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 05/04/2021] [Accepted: 06/07/2021] [Indexed: 10/21/2022]
Abstract
Biallelic deletions in the NPHP1 gene are the most frequent molecular defect of nephronophthisis, a kidney ciliopathy and leading cause of hereditary end-stage kidney disease. Nephrocystin 1, the gene product of NPHP1, is also expressed in photoreceptors where it plays an important role in intra-flagellar transport between the inner and outer segments. However, the human retinal phenotype has never been investigated in detail. Here, we characterized retinal features of 16 patients with homozygous deletions of the entire NPHP1 gene. Retinal assessment included multimodal imaging (optical coherence tomography, fundus autofluorescence) and visual function testing (visual acuity, full-field electroretinography, color vision, visual field). Fifteen patients had a mild retinal phenotype that predominantly affected cones, but with relative sparing of the fovea. Despite a predominant cone dysfunction, night vision problems were an early symptom in some cases. The consistent retinal phenotype on optical coherence tomography images included reduced reflectivity and often a granular appearance of the ellipsoid zone, fading or loss of the interdigitation zone, and mild outer retinal thinning. However, there were usually no obvious structural changes visible upon clinical examination and fundus autofluorescence imaging (occult retinopathy). More advanced retinal degeneration might occur with ageing. An identified additional CEP290 variant in one patient with a more severe retinal degeneration may indicate a potential role for genetic modifiers, although this requires further investigation. Thus, diagnostic awareness about this distinct retinal phenotype has implications for the differential diagnosis of nephronophthisis and for individual prognosis of visual function.
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Affiliation(s)
- Johannes Birtel
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK; Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Department of Ophthalmology, University of Bonn, Bonn, Germany
| | - Georg Spital
- Eye Center at St. Franziskus-Hospital Münster, Münster, Germany
| | - Marius Book
- Eye Center at St. Franziskus-Hospital Münster, Münster, Germany
| | - Sandra Habbig
- Department of Pediatrics, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Sören Bäumner
- Department of Pediatrics, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Vera Riehmer
- Institute of Human Genetics, University of Cologne, University Hospital of Cologne, Cologne, Germany
| | - Bodo B Beck
- Institute of Human Genetics, University of Cologne, University Hospital of Cologne, Cologne, Germany; Institute of Human Genetics, Center for Molecular Medicine Cologne, Center for Rare Diseases Cologne, University of Cologne, University Hospital of Cologne, Cologne, Germany
| | | | - Hanno J Bolz
- Institute of Human Genetics, University of Cologne, University Hospital of Cologne, Cologne, Germany; Senckenberg Centre for Human Genetics, Frankfurt, Germany
| | - Mareike Dahmer-Heath
- Department of General Pediatrics, University Children's Hospital, Münster, Germany
| | | | - Jens König
- Department of General Pediatrics, University Children's Hospital, Münster, Germany
| | - Peter Charbel Issa
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK; Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
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5
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Next-Generation Sequencing Applications for Inherited Retinal Diseases. Int J Mol Sci 2021; 22:ijms22115684. [PMID: 34073611 PMCID: PMC8198572 DOI: 10.3390/ijms22115684] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/21/2021] [Accepted: 05/22/2021] [Indexed: 12/12/2022] Open
Abstract
Inherited retinal diseases (IRDs) represent a collection of phenotypically and genetically diverse conditions. IRDs phenotype(s) can be isolated to the eye or can involve multiple tissues. These conditions are associated with diverse forms of inheritance, and variants within the same gene often can be associated with multiple distinct phenotypes. Such aspects of the IRDs highlight the difficulty met when establishing a genetic diagnosis in patients. Here we provide an overview of cutting-edge next-generation sequencing techniques and strategies currently in use to maximise the effectivity of IRD gene screening. These techniques have helped researchers globally to find elusive causes of IRDs, including copy number variants, structural variants, new IRD genes and deep intronic variants, among others. Resolving a genetic diagnosis with thorough testing enables a more accurate diagnosis and more informed prognosis and should also provide information on inheritance patterns which may be of particular interest to patients of a child-bearing age. Given that IRDs are heritable conditions, genetic counselling may be offered to help inform family planning, carrier testing and prenatal screening. Additionally, a verified genetic diagnosis may enable access to appropriate clinical trials or approved medications that may be available for the condition.
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6
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Maya I, Kahana S, Agmon-Fishman I, Klein C, Matar R, Berger R, Josefsberg SBY, Shohat M, Marom D, Basel-Salmon L, Sagi-Dain L. The phenotype of 15 cases with rare 8q24.13-q24.3 deletions-A new syndrome or still an enigma? Am J Med Genet A 2021; 185:1461-1467. [PMID: 33619900 DOI: 10.1002/ajmg.a.62131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/26/2021] [Accepted: 02/06/2021] [Indexed: 11/10/2022]
Abstract
Diagnosis of rare copy number variants (CNVs) with scarce literature evidence poses a major challenge for interpretation of the clinical significance of chromosomal microarray analysis (CMA) results, especially in the prenatal setting. Bioinformatic tools can be used to assist in this issue; however, this prediction can be imprecise. Our objective was to describe the phenotype of the rare copy number losses encompassing the 8q24.13-q24.3 locus, and to find common features in terms of genomic coordinates, gene content, and clinical phenotypic characteristics. Appropriate cases were retrieved using local databases of two largest Israeli centers performing CMA analysis. In addition, literature and public databases search was performed. Local database search yielded seven new patients with del (8)(q24.13q24.3) (one of these with an additional copy number variant). Literature and public databases search yielded eight additional patients. The cases showed high phenotypic variability, ranging from asymptomatic adults and fetuses with normal ultrasound to patients with autism/developmental delay (6/11 postnatal cases, 54.5%). No clear association was noted between the specific disease-causing/high-pLI gene content of the described del (8)(q24.13q24.3) to neurodevelopmental disorders, except for a possibly relevant locus encompassing the KCNQ3 gene. We present the challenges in classification of rare variants with limited clinical information. In such cases, genotype-phenotype correlation must be assessed with extra-caution and possibly using additional methods to assist the classification, especially in the prenatal setting.
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Affiliation(s)
- Idit Maya
- Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva, Israel.,Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Sarit Kahana
- Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva, Israel
| | - Ifaat Agmon-Fishman
- Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva, Israel
| | - Cochava Klein
- Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva, Israel
| | - Reut Matar
- Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva, Israel
| | - Racheli Berger
- Genetics Laboratory, Maccabi Health Services, Rehovot, Israel
| | | | - Mordechai Shohat
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.,Genetics Laboratory, Maccabi Health Services, Rehovot, Israel.,Bioinformatics Unit, Sheba Cancer Research Center, Sheba Medical Center, Tel Hashomer, Israel
| | - Daphna Marom
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.,Genetics Institute, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Lina Basel-Salmon
- Recanati Genetics Institute, Beilinson Hospital, Rabin Medical Center, Petach Tikva, Israel.,Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.,Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Felsenstein Medical Research Center, Rabin Medical Center, Petah Tikva, Israel
| | - Lena Sagi-Dain
- Genetics Institute, Carmel Medical Center, affiliated to the Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
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7
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Maya I, Sukenik-Halevy R, Basel-Salmon L, Sagi-Dain L. Ten points to consider when providing genetic counseling for variants of incomplete penetrance and variable expressivity detected in a prenatal setting. Acta Obstet Gynecol Scand 2020; 99:1427-1429. [PMID: 33084292 DOI: 10.1111/aogs.13963] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Idit Maya
- Rabin Medical Center, Recanati Genetics Institute, Beilinson Hospital, Petach Tikva, Israel
| | - Rivka Sukenik-Halevy
- Rabin Medical Center, Recanati Genetics Institute, Beilinson Hospital, Petach Tikva, Israel.,Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Lina Basel-Salmon
- Rabin Medical Center, Recanati Genetics Institute, Beilinson Hospital, Petach Tikva, Israel.,Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Lena Sagi-Dain
- Genetics Institute, Carmel Medical Center, affiliated to the Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
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8
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Zhang Z, Dai H, Wang L, Tao T, Xu J, Sun X, Yang L, Li G. Novel mutations of RPGR in Chinese families with X-linked retinitis pigmentosa. BMC Ophthalmol 2019; 19:240. [PMID: 31775781 PMCID: PMC6882249 DOI: 10.1186/s12886-019-1250-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/18/2019] [Indexed: 12/15/2022] Open
Abstract
Background RP (retinitis pigmentosa) is a group of hereditary retinal degenerative diseases. XLRP is a relatively severe subtype of RP. Thus, it is necessary to identify genes and mutations in patients who present with X-linked retinitis pigmentosa. Methods Genomic DNA was extracted from peripheral blood. The coding regions and intron-exon boundaries of the retinitis pigmentosa GTPase regulator (RPGR) and RP2 genes were amplified by PCR and then sequenced directly. Ophthalmic examinations were performed to identify affected individuals from two families and to characterize the phenotype of the disease. Results Mutation screening demonstrated two novel nonsense mutations (c.1541C > G; p.S514X and c.2833G > T; p.E945X) in the RPGR gene. The clinical manifestation of family 1 with mutations in exon 13 was mild. Genotype-phenotype correlation analysis suggested that patients with mutations close to the downstream region of ORF15 in family 2 manifested an early loss of cone function. Family 2 carried a nonsense mutation in ORF15 that appeared to have a semi-dominant pattern of inheritance. All male patients and two female carriers in family 2 manifested pathological myopia (PM), indicating that there may be a distinctive X-linked genotype-phenotype correlation between RP and PM. Conclusions We identified two novel mutations of the RPGR gene, which broadens the spectrum of RPGR mutations and the phenotypic spectrum of the disease in Chinese families.
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Affiliation(s)
- Zhimeng Zhang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Hehua Dai
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Lei Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Tianchang Tao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Jing Xu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Xiaowei Sun
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Liping Yang
- Department of Ophthalmology, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Peking University Third Hospital, Beijing, People's Republic of China
| | - Genlin Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China.
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Disruption of RPGR protein interaction network is the common feature of RPGR missense variations that cause XLRP. Proc Natl Acad Sci U S A 2019; 116:1353-1360. [PMID: 30622176 DOI: 10.1073/pnas.1817639116] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Retinitis pigmentosa (RP) is an inherited retinal degenerative disease with severe vision impairment leading to blindness. About 10-15% of RP cases are caused by mutations in the RPGR gene, with RPGR mutations accounting for 70% of X-linked RP cases. The mechanism by which RPGR mutations cause photoreceptor cell dysfunction is not well understood. In this study, we show that the two isoforms of RPGR (RPGR1-19 and RPGRORF15) interact with endogenous PDE6D, INPP5E, and RPGRIP1L. The RPGR1-19 isoform contains two PDE6D binding sites with the C-terminal prenylation site being the predominant PDE6D binding site. The C terminus of RPGR1-19 that contains the prenylation site regulates its interaction with PDE6D, INPP5E, and RPGRIP1L. Only the RPGR1-19 isoform localizes to cilia in cultured RPE1 cells. Missense variations found in RPGR patients disrupt the interaction between RPGR isoforms and their endogenous interactors INPP5E, PDE6D, and RPGRIP1L. We evaluated a RPGR missense variation (M58K) found in a family with X-linked retinitis pigmentosa (XLRP) and show that this missense variation disrupts the interaction of RPGR isoforms with their endogenous interactors. The M58K variation also disrupts the ciliary localization of the RPGR1-19 isoform. Using this assay, we also show that some of the RPGR missense variants reported in the literature might not actually be disease causing. Our data establishes an in vitro assay that can be used to validate the potential pathogenicity of RPGR missense variants.
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10
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Clinical and genetic characteristics of 251 consecutive patients with macular and cone/cone-rod dystrophy. Sci Rep 2018; 8:4824. [PMID: 29555955 PMCID: PMC5859282 DOI: 10.1038/s41598-018-22096-0] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 02/16/2018] [Indexed: 12/14/2022] Open
Abstract
Macular and cone/cone-rod dystrophies (MD/CCRD) demonstrate a broad genetic and phenotypic heterogeneity, with retinal alterations solely or predominantly involving the central retina. Targeted next-generation sequencing (NGS) is an efficient diagnostic tool for identifying mutations in patient with retinitis pigmentosa, which shows similar genetic heterogeneity. To detect the genetic causes of disease in patients with MD/CCRD, we implemented a two-tier procedure consisting of Sanger sequencing and targeted NGS including genes associated with clinically overlapping conditions. Disease-causing mutations were identified in 74% of 251 consecutive MD/CCRD patients (33% of the variants were novel). Mutations in ABCA4, PRPH2 and BEST1 accounted for 57% of disease cases. Further mutations were identified in CDHR1, GUCY2D, PROM1, CRX, GUCA1A, CERKL, MT-TL1, KIF11, RP1L1, MERTK, RDH5, CDH3, C1QTNF5, CRB1, JAG1, DRAM2, POC1B, NPHP1 and RPGR. We provide detailed illustrations of rare phenotypes, including autofluorescence and optical coherence tomography imaging. Targeted NGS also identified six potential novel genotype-phenotype correlations for FAM161A, INPP5E, MERTK, FBLN5, SEMA4A and IMPDH1. Clinical reassessment of genetically unsolved patients revealed subgroups with similar retinal phenotype, indicating a common molecular disease cause in each subgroup.
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Kammenga JE. The background puzzle: how identical mutations in the same gene lead to different disease symptoms. FEBS J 2017; 284:3362-3373. [PMID: 28390082 DOI: 10.1111/febs.14080] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 01/05/2023]
Abstract
Identical disease-causing mutations can lead to different symptoms in different people. The reason for this has been a puzzling problem for geneticists. Differential penetrance and expressivity of mutations has been observed within individuals with different and similar genetic backgrounds. Attempts have been made to uncover the underlying mechanisms that determine differential phenotypic effects of identical mutations through studies of model organisms. From these studies evidence is accumulating that to understand disease mechanism or predict disease prevalence, an understanding of the influence of genetic background is as important as the putative disease-causing mutations of relatively large effect. This review highlights current insights into phenotypic variation due to gene interactions, epigenetics and stochasticity in model organisms, and discusses their importance for understanding the mutational effect on disease symptoms.
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Affiliation(s)
- Jan E Kammenga
- Laboratory of Nematology, Wageningen University, The Netherlands
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Wang H, Zhang L, Cao J, Wu M, Ma X, Liu Z, Liu R, Zhao F, Wei C, Du L. Genome-Wide Specific Selection in Three Domestic Sheep Breeds. PLoS One 2015; 10:e0128688. [PMID: 26083354 PMCID: PMC4471085 DOI: 10.1371/journal.pone.0128688] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 04/29/2015] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Commercial sheep raised for mutton grow faster than traditional Chinese sheep breeds. Here, we aimed to evaluate genetic selection among three different types of sheep breed: two well-known commercial mutton breeds and one indigenous Chinese breed. RESULTS We first combined locus-specific branch lengths and di statistical methods to detect candidate regions targeted by selection in the three different populations. The results showed that the genetic distances reached at least medium divergence for each pairwise combination. We found these two methods were highly correlated, and identified many growth-related candidate genes undergoing artificial selection. For production traits, APOBR and FTO are associated with body mass index. For meat traits, ALDOA, STK32B and FAM190A are related to marbling. For reproduction traits, CCNB2 and SLC8A3 affect oocyte development. We also found two well-known genes, GHR (which affects meat production and quality) and EDAR (associated with hair thickness) were associated with German mutton merino sheep. Furthermore, four genes (POL, RPL7, MSL1 and SHISA9) were associated with pre-weaning gain in our previous genome-wide association study. CONCLUSIONS Our results indicated that combine locus-specific branch lengths and di statistical approaches can reduce the searching ranges for specific selection. And we got many credible candidate genes which not only confirm the results of previous reports, but also provide a suite of novel candidate genes in defined breeds to guide hybridization breeding.
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Affiliation(s)
- Huihua Wang
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Li Zhang
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Jiaxve Cao
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Mingming Wu
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Xiaomeng Ma
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Zhen Liu
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Ruizao Liu
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Fuping Zhao
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Caihong Wei
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
| | - Lixin Du
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, People’s Republic of China, Beijing, China
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Hoffman DR, Hughbanks-Wheaton DK, Pearson NS, Fish GE, Spencer R, Takacs A, Klein M, Locke KG, Birch DG. Four-year placebo-controlled trial of docosahexaenoic acid in X-linked retinitis pigmentosa (DHAX trial): a randomized clinical trial. JAMA Ophthalmol 2014; 132:866-73. [PMID: 24805262 DOI: 10.1001/jamaophthalmol.2014.1634] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
IMPORTANCE X-linked retinitis pigmentosa is a severe inherited retinal degenerative disease with a frequency of 1 in 100,000 persons. Because no cure is available for this orphan disease and treatment options are limited, slowing of disease progression would be a meaningful outcome. OBJECTIVE To determine whether high-dose docosahexaenoic acid (DHA), an ω-3 polyunsaturated fatty acid, slows progression of X-linked retinitis pigmentosa measured by cone electroretinography (ERG). DESIGN, SETTING, AND PARTICIPANTS A 4-year, single-site, randomized, placebo-controlled, double-masked phase 2 clinical trial at a research center specializing in medical retina. Seventy-eight male patients diagnosed as having X-linked retinitis pigmentosa were randomized to DHA or placebo. Data were omitted for 2 patients with non-X-linked retinitis pigmentosa and 16 patients who were unable to follow protocol during the first year. The remaining participants were tested annually and composed a modified intent-to-treat cohort (DHA group, n = 33; placebo group, n = 27). INTERVENTIONS All participants received a multivitamin and were randomly assigned to oral DHA (30 mg/kg/d) or placebo. MAIN OUTCOMES AND MEASURES The primary outcome was the rate of loss of cone ERG function. Secondary outcomes were rod and maximal ERG amplitudes and cone ERG implicit times. Capsule counts and red blood cell DHA levels were assessed to monitor adherence. RESULTS Average (6-month to 4-year) red blood cell DHA levels were 4-fold higher in the DHA group than in the placebo group (P < .001). There was no difference between the DHA and placebo groups in the rate of cone ERG functional loss (0.028 vs 0.022 log µV/y, respectively; P = .30). No group differences were evident for change in rod ERG (P = .27), maximal ERG (P = .65), or cone implicit time (no change over 4 years). The rate of cone loss (ie, event rate) was markedly reduced compared with rates in previous studies. No severe treatment-emergent adverse events were found. CONCLUSIONS AND RELEVANCE Long-term DHA supplementation was not effective in slowing the loss of cone or rod ERG function associated with X-linked retinitis pigmentosa. Participant dropout and lower-than-expected disease event rate limited power to detect statistical significance. A larger sample size, longer trial, and attainment of a target blood DHA level (13%) would be desirable. While DHA supplementation at 30 mg/kg/d does not present serious adverse effects, routine monitoring of gastrointestinal tolerance is prudent. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00100230.
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Affiliation(s)
- Dennis R Hoffman
- Retina Foundation of the Southwest, Dallas, Texas2Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas
| | - Dianna K Hughbanks-Wheaton
- Retina Foundation of the Southwest, Dallas, Texas2Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas
| | - N Shirlene Pearson
- Pearson Statistical Consulting and Expert Witness Testimony, Richardson, Texas
| | | | | | | | - Martin Klein
- Retina Foundation of the Southwest, Dallas, Texas
| | | | - David G Birch
- Retina Foundation of the Southwest, Dallas, Texas2Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas
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Yang L, Yin X, Feng L, You D, Wu L, Chen N, Li A, Li G, Ma Z. Novel mutations of RPGR in Chinese retinitis pigmentosa patients and the genotype-phenotype correlation. PLoS One 2014; 9:e85752. [PMID: 24454928 PMCID: PMC3893273 DOI: 10.1371/journal.pone.0085752] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 11/30/2013] [Indexed: 11/19/2022] Open
Abstract
X-linked Retinitis Pigmentosa (XLRP) accounts for 10–20% of all RP cases, and represents the most severe subtype of this disease. Mutations in the Retinitis Pigmentosa GTPase Regulator (RPGR) gene are the most common causes of XLRP, accounting for over 70–75% of all XLRP cases. In this work, we analyzed all the exons of RPGR gene with Sanger sequencing in seven Chinese XLRP families, two of these with a provisional diagnosis of adRP but without male-to-male transmission. Three novel deletions (c.2233_34delAG; c.2236_37delGA and c.2403_04delAG) and two known nonsense mutations (c.851C→G and c.2260G→T) were identified in five families. Two novel deletions (c.2233_34delAG and c.2236_37delGA) resulted in the same frame shift (p.E746RfsX22), created similar phenotype in Family 3 and 4. The novel deletion (c.2403_04delAG; p.E802GfsX31) resulted in both XLRP and x-linked cone-rod dystrophy within the male patients of family 5, which suggested the presence of either genetic or environmental modifiers, or both, play a substantial role in disease expression. Genotype-phenotype correlation analysis suggested that (1) both patients and female carriers with mutation in Exon 8 (Family 1) manifest more severe disease than did those with ORF15 mutations (Family 2&3&4); (2) mutation close to downstream of ORF15 (Family 5) demonstrate the early preferential loss of cone function with moderate loss of rod function.
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Affiliation(s)
- Liping Yang
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
| | - Xiaobei Yin
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, P. R. China
| | - Lina Feng
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
| | - Debo You
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
| | - Lemeng Wu
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
| | - Ningning Chen
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
| | - Aijun Li
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
| | - Genlin Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, P. R. China
- * E-mail: (GL); (ZM)
| | - Zhizhong Ma
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, P. R. China
- * E-mail: (GL); (ZM)
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Corton M, Avila-Fernandez A, Vallespín E, López-Molina MI, Almoguera B, Martín-Garrido E, Tatu SD, Khan MI, Blanco-Kelly F, Riveiro-Alvarez R, Brión M, García-Sandoval B, Cremers FPM, Carracedo A, Ayuso C. Involvement of LCA5 in Leber congenital amaurosis and retinitis pigmentosa in the Spanish population. Ophthalmology 2013; 121:399-407. [PMID: 24144451 DOI: 10.1016/j.ophtha.2013.08.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/29/2013] [Accepted: 08/21/2013] [Indexed: 10/26/2022] Open
Abstract
OBJECTIVE We aimed to identify novel genetic defects in the LCA5 gene underlying Leber congenital amaurosis (LCA) in the Spanish population and to describe the associated phenotype. DESIGN Case series. PARTICIPANTS A cohort of 217 unrelated Spanish families affected by autosomal recessive or isolated retinal dystrophy, that is, 79 families with LCA and 138 families with early-onset retinitis pigmentosa (EORP). A total of 100 healthy, unrelated Spanish individuals were screened as controls. METHODS High-resolution homozygosity mapping was performed in 44 patients with LCA using genome-wide single nucleotide polymorphism (SNP) microarrays. Direct sequencing of the LCA5 gene was performed in 5 patients who showed homozygous regions at chromosome 6 and in 173 unrelated individuals with LCA or EORP. The ophthalmic history of 8 patients carrying LCA5 mutations was reviewed and additional examinations were performed, including electroretinography (ERG), optical coherence tomography (OCT), and fundus photography. MAIN OUTCOME MEASURES Single nucleotide polymorphism genotyping, identity-by-descent (IBD) regions, LCA5 mutations, best-corrected visual acuity, visual field assessments, fundus appearance, ERG, and OCT findings. RESULTS Four novel and 2 previously reported LCA5 mutations have been identified in 6 unrelated families with LCA by homozygosity mapping or Sanger sequencing. Thus, LCA5 mutations have a frequency of 7.6% in the Spanish population. However, no LCA5 mutations were found in 138 patients with EORP. Although most of the identified LCA5 mutations led to a truncated protein, a likely pathogenic missense variant was identified for the first time as a cause of LCA, segregating in 2 families. We also have characterized a novel splicing site mutation at the RNA level, demonstrating that the mutant LCA5 transcript was absent in a patient. All patients carrying LCA5 mutations presented nystagmus, night blindness, and progressive loss of visual acuity and visual field leading to blindness toward the third decade of life. Fundoscopy showed fundus features of pigmentary retinopathy with atrophic macular lesions. CONCLUSIONS This work reveals a higher frequency of LCA5 mutations in a Spanish LCA cohort than in other populations. This study established gene-specific frequencies and the underlying phenotype of LCA5 mutations in the Spanish population.
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Affiliation(s)
- Marta Corton
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Almudena Avila-Fernandez
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Elena Vallespín
- Instituto de Genética Médica y Molecular, IdiPaz, Hospital Universitario La Paz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - María Isabel López-Molina
- Department of Ophthalmology, Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Berta Almoguera
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Esther Martín-Garrido
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Sorina D Tatu
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - M Imran Khan
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Fiona Blanco-Kelly
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Rosa Riveiro-Alvarez
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - María Brión
- Genetics of Cardiovascular and Ophthalmologic Diseases, Instituto de Investigación Sanitaria de Santiago de Compostela, RIC, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Blanca García-Sandoval
- Department of Ophthalmology, Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Angel Carracedo
- Genomic Medicine Group-USC, Fundación Publica Galega de Medicina Xenómica, Santiago de Compostela, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain
| | - Carmen Ayuso
- Department of Genetics, IIS - Fundación Jiménez Díaz, Madrid, Spain; Centre for Biomedical Network Research on Rare Diseases, ISCIII, Valencia, Spain.
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Estrada-Cuzcano A, Roepman R, Cremers FPM, den Hollander AI, Mans DA. Non-syndromic retinal ciliopathies: translating gene discovery into therapy. Hum Mol Genet 2012; 21:R111-24. [PMID: 22843501 DOI: 10.1093/hmg/dds298] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Homozygosity mapping and exome sequencing have accelerated the discovery of gene mutations and modifier alleles implicated in inherited retinal degeneration in humans. To date, 158 genes have been found to be mutated in individuals with retinal dystrophies. Approximately one-third of the gene defects underlying retinal degeneration affect the structure and/or function of the 'connecting cilium' in photoreceptors. This structure corresponds to the transition zone of a prototypic cilium, a region with increasing relevance for ciliary homeostasis. The connecting cilium connects the inner and outer segments of the photoreceptor, mediating bi-directional transport of phototransducing proteins required for vision. In fact, the outer segment, connecting cilium and associated basal body, forms a highly specialized sensory cilium, fully dedicated to photoreception and subsequent signal transduction to the brain. At least 21 genes that encode ciliary proteins are implicated in non-syndromic retinal dystrophies such as cone dystrophy, cone-rod dystrophy, Leber congenital amaurosis (LCA), macular degeneration or retinitis pigmentosa (RP). The generation and characterization of vertebrate retinal ciliopathy animal models have revealed insights into the molecular disease mechanism which are indispensable for the development and evaluation of therapeutic strategies. Gene augmentation therapy has proven to be safe and successful in restoring long-term sight in mice, dogs and humans suffering from LCA or RP. Here, we present a comprehensive overview of the genes, mutations and modifier alleles involved in non-syndromic retinal ciliopathies, review the progress in dissecting the associated retinal disease mechanisms and evaluate gene augmentation approaches to antagonize retinal degeneration in these ciliopathies.
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