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Kamenarova K, Mihova K, Veleva N, Mermeklieva E, Mihaylova B, Dimitrova G, Oscar A, Shandurkov I, Cherninkova S, Kaneva R. Panel-based next-generation sequencing identifies novel mutations in Bulgarian patients with inherited retinal dystrophies. Mol Genet Genomic Med 2022; 10:e1997. [PMID: 35656873 PMCID: PMC9356554 DOI: 10.1002/mgg3.1997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 04/07/2022] [Accepted: 05/13/2022] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND Next-generation sequencing (NGS)-based method is being used broadly for genetic testing especially for clinically and genetically heterogeneous disorders, such as inherited retinal degenerations (IRDs) but still not routinely used for molecular diagnostics in Bulgaria. Consequently, the purpose of this study was to evaluate the effectiveness of a molecular diagnostic approach, based on targeted NGS for the identification of the disease-causing mutations in 16 Bulgarian patients with different IRDs. METHODS We applied a customized NGS panel, including 125 genes associated with retinal and other eye diseases to the patients with hereditary retinopathies. RESULTS Systematic filtering approach coupled with copy number variation analysis and segregation study lead to the identification of 16 pathogenic and likely pathogenic variants in 12/16 (75%) of IRD patients, 2 of which novel (12.5%): ABCA4-c.668delA (p.K223Rfs18) and RР1-c.2015dupA (p.K673Efs*25). Mutations in the ABCA4, PRPH2, USH2A, BEST1, RР1, CDHR1, and RHO genes were detected reaching a diagnostic yield between 42.9% for Retinitis pigmentosa cases and 100% for macular degeneration, Usher syndrome, and cone-rod dystrophy patients. CONCLUSION Our results confirm the usefulness of targeted NGS approach based on frequently mutated genes as a comprehensive and successful genetic diagnostic tool for IRDs with significant impact on patients counseling.
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Affiliation(s)
- Kunka Kamenarova
- Molecular Medicine Center, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Sofia, Bulgaria.,Laboratory of Genomic Diagnostics, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Sofia, Bulgaria
| | - Kalina Mihova
- Molecular Medicine Center, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Sofia, Bulgaria.,Laboratory of Genomic Diagnostics, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Sofia, Bulgaria
| | - Nevyana Veleva
- Department of Ophthalmology, University Hospital "Alexandrovska", Medical University of Sofia, Sofia, Bulgaria
| | - Elena Mermeklieva
- Clinic of Ophthalmology, University Hospital "Lozenetz", Medical Faculty, Sofia University "St. Kliment Ohridski", Sofia, Bulgaria
| | | | - Galina Dimitrova
- Department of Ophthalmology, University Hospital "Alexandrovska", Medical University of Sofia, Sofia, Bulgaria
| | - Alexander Oscar
- Department of Ophthalmology, University Hospital "Alexandrovska", Medical University of Sofia, Sofia, Bulgaria
| | | | - Sylvia Cherninkova
- Department of Neurology, University hospital "Alexandrovska", Medical University of Sofia, Sofia, Bulgaria
| | - Radka Kaneva
- Molecular Medicine Center, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Sofia, Bulgaria.,Laboratory of Genomic Diagnostics, Department of Medical Chemistry and Biochemistry, Medical Faculty, Medical University of Sofia, Sofia, Bulgaria
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Collison FT, Fishman GA, Nagasaki T, Zernant J, McAnany JJ, Park JC, Allikmets R. Characteristic Ocular Features in Cases of Autosomal Recessive PROM1 Cone-Rod Dystrophy. Invest Ophthalmol Vis Sci 2019; 60:2347-2356. [PMID: 31136651 PMCID: PMC6538366 DOI: 10.1167/iovs.19-26993] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Purpose To define characteristic ocular features in a group of patients with autosomal recessive (AR) PROM1 cone-rod dystrophy (CRD). Methods Three males and one female from three unrelated families were first seen at the ages of 15 to 22 years and diagnosed with CRD. Clinical testing available for review included full-field electroretinogram (ERG) in three patients, as well as near-infrared autofluorescence (NIR-AF), spectral-domain optical coherence tomography (SD-OCT), and color fundus photography in all four patients. Whole exome sequencing (WES) was performed on all cases, and whole genome sequencing (WGS) was performed in two families. Results WES found compound heterozygous PROM1 variants in one isolated male, plus heterozygous variants in the remaining patients. WGS uncovered deleterious PROM1 variants in these two families. ERG showed markedly reduced cone-isolated amplitudes and variably reduced rod-isolated amplitudes. The dark-adapted combined rod and cone responses demonstrated notably reduced a-wave amplitudes and moderately reduced b-waves, and the resultant waveform resembled the normal rod-isolated response. On fundus examination, oval-shaped macular lesions were observed, as were several small, circular hypoautofluorescent lesions within the posterior pole on NIR-AF. Three patients showed extramacular circular atrophic lesions. Conclusions The autofluorescence changes, peripheral retinal abnormalities, and ERG findings have not been emphasized in previous reports of AR PROM1, but they became a recognizable phenotype in this cohort of patients. A similar constellation of findings may be observed in CRD due to CDHR1, a functionally related gene. The pattern of abnormalities reported herein may help to focus genetic screening in patients with these findings.
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Affiliation(s)
- Frederick T Collison
- The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois, United States
| | - Gerald A Fishman
- The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois, United States.,Department of Ophthalmology and Visual Sciences, The University of Illinois at Chicago, Chicago, Illinois, United States
| | - Takayuki Nagasaki
- Department of Ophthalmology, Columbia University, New York, New York, United States
| | - Jana Zernant
- Department of Ophthalmology, Columbia University, New York, New York, United States
| | - J Jason McAnany
- Department of Ophthalmology and Visual Sciences, The University of Illinois at Chicago, Chicago, Illinois, United States
| | - Jason C Park
- Department of Ophthalmology and Visual Sciences, The University of Illinois at Chicago, Chicago, Illinois, United States
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, New York, United States.,Department of Pathology and Cell Biology, Columbia University, New York, New York, United States
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3
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Martin-Merida I, Aguilera-Garcia D, Fernandez-San JP, Blanco-Kelly F, Zurita O, Almoguera B, Garcia-Sandoval B, Avila-Fernandez A, Arteche A, Minguez P, Carballo M, Corton M, Ayuso C. Toward the Mutational Landscape of Autosomal Dominant Retinitis Pigmentosa: A Comprehensive Analysis of 258 Spanish Families. Invest Ophthalmol Vis Sci 2019; 59:2345-2354. [PMID: 29847639 DOI: 10.1167/iovs.18-23854] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To provide a comprehensive overview of the molecular basis of autosomal dominant retinitis pigmentosa (adRP) in Spanish families. Thus, we established the molecular characterization rate, gene prevalence, and mutational spectrum in the largest European cohort reported to date. Methods A total of 258 unrelated Spanish families with a clinical diagnosis of RP and suspected autosomal dominant inheritance were included. Clinical diagnosis was based on complete ophthalmologic examination and family history. Retrospective and prospective analysis of Spanish adRP families was carried out using a combined strategy consisting of classic genetic techniques and next-generation sequencing (NGS) for single-nucleotide variants and copy number variation (CNV) screening. Results Overall, 60% of our families were genetically solved. Interestingly, 3.1% of the cohort carried pathogenic CNVs. Disease-causing variants were found in an autosomal dominant gene in 55% of the families; however, X-linked and autosomal recessive forms were also identified in 3% and 2%, respectively. Four genes (RHO, PRPF31, RP1, and PRPH2) explained up to 62% of the solved families. Missense changes were most frequently found in adRP-associated genes; however, CNVs represented a relevant disease cause in PRPF31- and CRX-associated forms. Conclusions Implementation of NGS technologies in the adRP study clearly increased the diagnostic yield compared with classic approaches. Our study outcome expands the spectrum of disease-causing variants, provides accurate data on mutation gene prevalence, and highlights the implication of CNVs as important contributors to adRP etiology.
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Affiliation(s)
- Inmaculada Martin-Merida
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Domingo Aguilera-Garcia
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Jose P Fernandez-San
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Fiona Blanco-Kelly
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Olga Zurita
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Berta Almoguera
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States
| | - Blanca Garcia-Sandoval
- Department of Ophthalmology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Almudena Avila-Fernandez
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Ana Arteche
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Pablo Minguez
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Miguel Carballo
- Molecular Genetics Unit, Hospital de Terrassa, Terrassa, Barcelona, Spain
| | - Marta Corton
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Carmen Ayuso
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital-Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
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Jones KD, Wheaton DK, Bowne SJ, Sullivan LS, Birch DG, Chen R, Daiger SP. Next-generation sequencing to solve complex inherited retinal dystrophy: A case series of multiple genes contributing to disease in extended families. Mol Vis 2017; 23:470-481. [PMID: 28761320 PMCID: PMC5524430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 07/18/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE With recent availability of next-generation sequencing (NGS), it is becoming more common to pursue disease-targeted panel testing rather than traditional sequential gene-by-gene dideoxy sequencing. In this report, we describe using NGS to identify multiple disease-causing mutations that contribute concurrently or independently to retinal dystrophy in three relatively small families. METHODS Family members underwent comprehensive visual function evaluations, and genetic counseling including a detailed family history. A preliminary genetic inheritance pattern was assigned and updated as additional family members were tested. Family 1 (FAM1) and Family 2 (FAM2) were clinically diagnosed with retinitis pigmentosa (RP) and had a suspected autosomal dominant pedigree with non-penetrance (n.p.). Family 3 (FAM3) consisted of a large family with a diagnosis of RP and an overall dominant pedigree, but the proband had phenotypically cone-rod dystrophy. Initial genetic analysis was performed on one family member with traditional Sanger single gene sequencing and/or panel-based testing, and ultimately, retinal gene-targeted NGS was required to identify the underlying cause of disease for individuals within the three families. Results obtained in these families necessitated further genetic and clinical testing of additional family members to determine the complex genetic and phenotypic etiology of each family. RESULTS Genetic testing of FAM1 (n = 4 affected; 1 n.p.) identified a dominant mutation in RP1 (p.Arg677Ter) that was present for two of the four affected individuals but absent in the proband and the presumed non-penetrant individual. Retinal gene-targeted NGS in the fourth affected family member revealed compound heterozygous mutations in USH2A (p. Cys419Phe, p.Glu767Serfs*21). Genetic testing of FAM2 (n = 3 affected; 1 n.p.) identified three retinal dystrophy genes (PRPH2, PRPF8, and USH2A) with disease-causing mutations in varying combinations among the affected family members. Genetic testing of FAM3 (n = 7 affected) identified a mutation in PRPH2 (p.Pro216Leu) tracking with disease in six of the seven affected individuals. Additional retinal gene-targeted NGS testing determined that the proband also harbored a multiple exon deletion in the CRX gene likely accounting for her cone-rod phenotype; her son harbored only the mutation in CRX, not the familial mutation in PRPH2. CONCLUSIONS Multiple genes contributing to the retinal dystrophy genotypes within a family were discovered using retinal gene-targeted NGS. Families with noted examples of phenotypic variation or apparent non-penetrant individuals may offer a clue to suspect complex inheritance. Furthermore, this finding underscores that caution should be taken when attributing a single gene disease-causing mutation (or inheritance pattern) to a family as a whole. Identification of a disease-causing mutation in a proband, even with a clear inheritance pattern in hand, may not be sufficient for targeted, known mutation analysis in other family members.
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Affiliation(s)
| | - Dianna K. Wheaton
- Retina Foundation of the Southwest, Dallas, TX,Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Sara J. Bowne
- Human Genetics Center, School of Public Health, The University of Texas Health Science Center (UTHealth), Houston, TX
| | - Lori S. Sullivan
- Human Genetics Center, School of Public Health, The University of Texas Health Science Center (UTHealth), Houston, TX
| | - David G. Birch
- Retina Foundation of the Southwest, Dallas, TX,Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Rui Chen
- Baylor College of Medicine, Houston, TX
| | - Stephen P. Daiger
- Human Genetics Center, School of Public Health, The University of Texas Health Science Center (UTHealth), Houston, TX,Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center Houston (UTHealth), Houston, TX
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5
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Van Cauwenbergh C, Coppieters F, Roels D, De Jaegere S, Flipts H, De Zaeytijd J, Walraedt S, Claes C, Fransen E, Van Camp G, Depasse F, Casteels I, de Ravel T, Leroy BP, De Baere E. Mutations in Splicing Factor Genes Are a Major Cause of Autosomal Dominant Retinitis Pigmentosa in Belgian Families. PLoS One 2017; 12:e0170038. [PMID: 28076437 PMCID: PMC5226823 DOI: 10.1371/journal.pone.0170038] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 12/27/2016] [Indexed: 12/14/2022] Open
Abstract
Purpose Autosomal dominant retinitis pigmentosa (adRP) is characterized by an extensive genetic heterogeneity, implicating 27 genes, which account for 50 to 70% of cases. Here 86 Belgian probands with possible adRP underwent genetic testing to unravel the molecular basis and to assess the contribution of the genes underlying their condition. Methods Mutation detection methods evolved over the past ten years, including mutation specific methods (APEX chip analysis), linkage analysis, gene panel analysis (Sanger sequencing, targeted next-generation sequencing or whole exome sequencing), high-resolution copy number screening (customized microarray-based comparative genomic hybridization). Identified variants were classified following American College of Medical Genetics and Genomics (ACMG) recommendations. Results Molecular genetic screening revealed mutations in 48/86 cases (56%). In total, 17 novel pathogenic mutations were identified: four missense mutations in RHO, five frameshift mutations in RP1, six mutations in genes encoding spliceosome components (SNRNP200, PRPF8, and PRPF31), one frameshift mutation in PRPH2, and one frameshift mutation in TOPORS. The proportion of RHO mutations in our cohort (14%) is higher than reported in a French adRP population (10.3%), but lower than reported elsewhere (16.5–30%). The prevalence of RP1 mutations (10.5%) is comparable to other populations (3.5%-10%). The mutation frequency in genes encoding splicing factors is unexpectedly high (altogether 19.8%), with PRPF31 the second most prevalent mutated gene (10.5%). PRPH2 mutations were found in 4.7% of the Belgian cohort. Two families (2.3%) have the recurrent NR2E3 mutation p.(Gly56Arg). The prevalence of the recurrent PROM1 mutation p.(Arg373Cys) was higher than anticipated (3.5%). Conclusions Overall, we identified mutations in 48 of 86 Belgian adRP cases (56%), with the highest prevalence in RHO (14%), RP1 (10.5%) and PRPF31 (10.5%). Finally, we expanded the molecular spectrum of PRPH2, PRPF8, RHO, RP1, SNRNP200, and TOPORS-associated adRP by the identification of 17 novel mutations.
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Affiliation(s)
- Caroline Van Cauwenbergh
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Frauke Coppieters
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Dimitri Roels
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Sarah De Jaegere
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Helena Flipts
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
- Center for Human Genetics, University Hospitals Leuven, Louvain, Belgium
| | - Julie De Zaeytijd
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Sophie Walraedt
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Charlotte Claes
- Center for Medical Genetics Antwerp, Antwerp University, Antwerp, Belgium
| | - Erik Fransen
- Center for Medical Genetics Antwerp, Antwerp University, Antwerp, Belgium
| | - Guy Van Camp
- Center for Medical Genetics Antwerp, Antwerp University, Antwerp, Belgium
| | - Fanny Depasse
- Department of Ophthalmology, Hôpital Erasme-ULB, Brussels, Belgium
| | - Ingele Casteels
- Department of Ophthalmology, University Hospitals Leuven, Louvain, Belgium
| | - Thomy de Ravel
- Center for Human Genetics, University Hospitals Leuven, Louvain, Belgium
| | - Bart P. Leroy
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
- Division of Ophthalmology & Center for Cellular & Molecular Therapy, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Elfride De Baere
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
- * E-mail:
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Kabir F, Ullah I, Ali S, Gottsch AD, Naeem MA, Assir MZ, Khan SN, Akram J, Riazuddin S, Ayyagari R, Hejtmancik JF, Riazuddin SA. Loss of function mutations in RP1 are responsible for retinitis pigmentosa in consanguineous familial cases. Mol Vis 2016; 22:610-25. [PMID: 27307693 PMCID: PMC4901054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 06/08/2016] [Indexed: 10/31/2022] Open
Abstract
PURPOSE This study was undertaken to identify causal mutations responsible for autosomal recessive retinitis pigmentosa (arRP) in consanguineous families. METHODS Large consanguineous families were ascertained from the Punjab province of Pakistan. An ophthalmic examination consisting of a fundus evaluation and electroretinography (ERG) was completed, and small aliquots of blood were collected from all participating individuals. Genomic DNA was extracted from white blood cells, and a genome-wide linkage or a locus-specific exclusion analysis was completed with polymorphic short tandem repeats (STRs). Two-point logarithm of odds (LOD) scores were calculated, and all coding exons and exon-intron boundaries of RP1 were sequenced to identify the causal mutation. RESULTS The ophthalmic examination showed that affected individuals in all families manifest cardinal symptoms of RP. Genome-wide scans localized the disease phenotype to chromosome 8q, a region harboring RP1, a gene previously implicated in the pathogenesis of RP. Sanger sequencing identified a homozygous single base deletion in exon 4: c.3697delT (p.S1233Pfs22*), a single base substitution in intron 3: c.787+1G>A (p.I263Nfs8*), a 2 bp duplication in exon 2: c.551_552dupTA (p.Q185Yfs4*) and an 11,117 bp deletion that removes all three coding exons of RP1. These variations segregated with the disease phenotype within the respective families and were not present in ethnically matched control samples. CONCLUSIONS These results strongly suggest that these mutations in RP1 are responsible for the retinal phenotype in affected individuals of all four consanguineous families.
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Affiliation(s)
- Firoz Kabir
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Inayat Ullah
- National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Shahbaz Ali
- National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | | | - Muhammad Asif Naeem
- National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Zaman Assir
- Allama Iqbal Medical College, University of Health Sciences, Lahore, Pakistan,National Centre for Genetic Diseases, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan
| | - Shaheen N. Khan
- National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Javed Akram
- Allama Iqbal Medical College, University of Health Sciences, Lahore, Pakistan,National Centre for Genetic Diseases, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan
| | - Sheikh Riazuddin
- National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan,Allama Iqbal Medical College, University of Health Sciences, Lahore, Pakistan,National Centre for Genetic Diseases, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan
| | - Radha Ayyagari
- Shiley Eye Institute, University of California, San Diego, CA
| | - J. Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD
| | - S. Amer Riazuddin
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD
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7
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Panel-based NGS Reveals Novel Pathogenic Mutations in Autosomal Recessive Retinitis Pigmentosa. Sci Rep 2016; 6:19531. [PMID: 26806561 PMCID: PMC4726392 DOI: 10.1038/srep19531] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/14/2015] [Indexed: 12/22/2022] Open
Abstract
Retinitis pigmentosa (RP) is a group of inherited progressive retinal dystrophies (RD) characterized by photoreceptor degeneration. RP is highly heterogeneous both clinically and genetically, which complicates the identification of causative genes and mutations. Targeted next-generation sequencing (NGS) has been demonstrated to be an effective strategy for the detection of mutations in RP. In our study, an in-house gene panel comprising 75 known RP genes was used to analyze a cohort of 47 unrelated Spanish families pre-classified as autosomal recessive or isolated RP. Disease-causing mutations were found in 27 out of 47 cases achieving a mutation detection rate of 57.4%. In total, 33 pathogenic mutations were identified, 20 of which were novel mutations (60.6%). Furthermore, not only single nucleotide variations but also copy-number variations, including three large deletions in the USH2A and EYS genes, were identified. Finally seven out of 27 families, displaying mutations in the ABCA4, RP1, RP2 and USH2A genes, could be genetically or clinically reclassified. These results demonstrate the potential of our panel-based NGS strategy in RP diagnosis.
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8
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Méndez-Vidal C, Bravo-Gil N, González-Del Pozo M, Vela-Boza A, Dopazo J, Borrego S, Antiñolo G. Novel RP1 mutations and a recurrent BBS1 variant explain the co-existence of two distinct retinal phenotypes in the same pedigree. BMC Genet 2014; 15:143. [PMID: 25494902 PMCID: PMC4271491 DOI: 10.1186/s12863-014-0143-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 12/03/2014] [Indexed: 12/30/2022] Open
Abstract
Background Molecular diagnosis of Inherited Retinal Dystrophies (IRD) has long been challenging due to the extensive clinical and genetic heterogeneity present in this group of disorders. Here, we describe the clinical application of an integrated next-generation sequencing approach to determine the underlying genetic defects in a Spanish family with a provisional clinical diagnosis of autosomal recessive Retinitis Pigmentosa (arRP). Results Exome sequencing of the index patient resulted in the identification of the homozygous BBS1 p.M390R mutation. Sanger sequencing of additional members of the family showed lack of co-segregation of the p.M390R variant in some individuals. Clinical reanalysis indicated co-ocurrence of two different phenotypes in the same family: Bardet-Biedl syndrome in the individual harboring the BBS1 mutation and non-syndromic arRP in extended family members. To identify possible causative mutations underlying arRP, we conducted disease-targeted gene sequencing using a panel of 26 IRD genes. The in-house custom panel was validated using 18 DNA samples known to harbor mutations in relevant genes. All variants were redetected, indicating a high mutation detection rate. This approach allowed the identification of two novel heterozygous null mutations in RP1 (c.4582_4585delATCA; p.I1528Vfs*10 and c.5962dupA; p.I1988Nfs*3) which co-segregated with the disease in arRP patients. Additionally, a mutational screening in 96 patients of our cohort with genetically unresolved IRD revealed the presence of the c.5962dupA mutation in one unrelated family. Conclusions The combination of molecular findings for RP1 and BBS1 genes through exome and gene panel sequencing enabled us to explain the co-existence of two different retinal phenotypes in a family. The identification of two novel variants in RP1 suggests that the use of panels containing the prevalent genes of a particular population, together with an optimized data analysis pipeline, is an efficient and cost-effective approach that can be reliably implemented into the routine diagnostic process of diverse inherited retinal disorders. Moreover, the identification of these novel variants in two unrelated families supports the relatively high prevalence of RP1 mutations in Spanish population and the role of private mutations for commonly mutated genes, while extending the mutational spectrum of RP1. Electronic supplementary material The online version of this article (doi:10.1186/s12863-014-0143-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Cristina Méndez-Vidal
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain.
| | - Nereida Bravo-Gil
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain.
| | - María González-Del Pozo
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain.
| | - Alicia Vela-Boza
- Genomics and Bioinformatics Platform of Andalusia (GBPA), Seville, Spain.
| | - Joaquín Dopazo
- Genomics and Bioinformatics Platform of Andalusia (GBPA), Seville, Spain. .,Computational Genomics Department, Centro de Investigación Príncipe Felipe (CIPF), Valencia, Spain.
| | - Salud Borrego
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain.
| | - Guillermo Antiñolo
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain. .,Genomics and Bioinformatics Platform of Andalusia (GBPA), Seville, Spain.
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Siemiatkowska AM, Astuti GD, Arimadyo K, den Hollander AI, Faradz SM, Cremers FP, Collin RW. Identification of a novel nonsense mutation in RP1 that causes autosomal recessive retinitis pigmentosa in an Indonesian family. Mol Vis 2012; 18:2411-9. [PMID: 23077400 PMCID: PMC3472925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 10/01/2012] [Indexed: 11/04/2022] Open
Abstract
PURPOSE The purpose of this study was to identify the underlying molecular genetic defect in an Indonesian family with three affected individuals who had received a diagnosis of retinitis pigmentosa (RP). METHODS Clinical evaluation of the family members included measuring visual acuity and fundoscopy, and assessing visual field and color vision. Genomic DNA of the three affected individuals was analyzed with Illumina 700k single nucleotide polymorphism (SNP) arrays, and homozygous regions were identified using PLINK software. Mutation analysis was performed with sequence analysis of the retinitis pigmentosa 1 (RP1) gene that resided in one of the homozygous regions. The frequency of the identified mutation in the Indonesian population was determined with TaqI restriction fragment length polymorphism analysis. RESULTS A novel homozygous nonsense mutation in exon 4 of the RP1 gene, c.1012C>T (p.R338*), was identified in the proband and her two affected sisters. Unaffected family members either carried two wild-type alleles or were heterozygous carriers of the mutation. The mutation was not present in 184 Indonesian control samples. CONCLUSIONS Most of the previously reported RP1 mutations are inherited in an autosomal dominant mode, and appear to cluster in exon 4. Here, we identified a novel homozygous p.R338* mutation in exon 4 of RP1, and speculate on the mutational mechanisms of different RP1 mutations underlying dominant and recessive RP.
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Affiliation(s)
- Anna M. Siemiatkowska
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Galuh D.N. Astuti
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Division of Human Genetics, Center for Biomedical Research, Faculty of Medicine, Diponegoro University, Semarang, Indonesia
| | - Kentar Arimadyo
- Division of Human Genetics, Center for Biomedical Research, Faculty of Medicine, Diponegoro University, Semarang, Indonesia,Department of Ophthalmology, Faculty of Medicine, Diponegoro University/Dr. Kariadi Hospital, Semarang, Indonesia
| | - Anneke I. den Hollander
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Department of Ophthalmology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Sultana M.H. Faradz
- Division of Human Genetics, Center for Biomedical Research, Faculty of Medicine, Diponegoro University, Semarang, Indonesia
| | - Frans P.M. Cremers
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Rob W.J. Collin
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands,Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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10
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Chizzolini M, Galan A, Milan E, Sebastiani A, Costagliola C, Parmeggiani F. Good epidemiologic practice in retinitis pigmentosa: from phenotyping to biobanking. Curr Genomics 2012; 12:260-6. [PMID: 22131871 PMCID: PMC3131733 DOI: 10.2174/138920211795860071] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 04/12/2011] [Accepted: 04/30/2011] [Indexed: 01/07/2023] Open
Abstract
Inherited retinal dystrophies, such as retinitis pigmentosa (RP), include a group of relatively rare hereditary diseases caused by mutations in genes that code for proteins involved in the maintenance and function of the photoreceptor cells (cones and rods). The different forms of RP consist of progressive neurodegenerative disorders which are generally related to various and severe limitations of visual performances. In the course of typical RP (rod-cone dystrophy), the affected individuals first experience night-blindness and/or visual field constriction (secondary to rod dysfunctions), followed by variable alterations of the central vision (due to cone damages). On the other hand, during the atypical form of RP (cone-rod dystrophy), the cone’s functionalities are prevalently disrupted in comparison with the rod’s ones. The basic diagnosis of RP relies upon the documentation of unremitting loss in photoreceptor activity by electroretinogram and/or visual field testing. The prevalence of all RP typologies is variably reported in about one case for each 3000-5000 individuals, with a total of about two millions of affected persons worldwide. The inherited retinal dystrophies are sometimes the epiphenomenon of a complex framework (syndromic RP), but more often they represent an isolated disorder (about 85-90 % of cases). Although 200 causative RP mutations have been hitherto detected in more than 100 different genes, the molecular defect is identifiable in just about the 50% of the analyzed patients with RP. Not only the RP genotypes are very heterogeneous, but also the patients with the same mutation can be affected by different phenotypic manifestations. RP can be inherited as autosomal dominant, autosomal recessive or X-linked trait, and many sporadic forms are diagnosed in patients with no affected relatives. Dissecting the clinico-genetic complexity of RP has become an attainable objective by means of large-scale research projects, in which the collaboration between ophthalmologists, geneticists, and epidemiologists becomes a crucial aspect. In the present review, the main issues regarding clinical phenotyping and epidemiologic criticisms of RP are focused, especially highlighting the importance of both standardization of the diagnostic protocols and appropriateness of the disease’s registration systems.
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Affiliation(s)
- Marzio Chizzolini
- Center for Retinitis Pigmentosa of Veneto Region, Camposampiero Hospital, ULSS 15 Alta Padovana, Camposampiero, Italy
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11
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Expression of wild-type Rp1 protein in Rp1 knock-in mice rescues the retinal degeneration phenotype. PLoS One 2012; 7:e43251. [PMID: 22927954 PMCID: PMC3424119 DOI: 10.1371/journal.pone.0043251] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 07/18/2012] [Indexed: 01/31/2023] Open
Abstract
Mutations in the retinitis pigmentosa 1 (RP1) gene are a common cause of autosomal dominant retinitis pigmentosa (adRP), and have also been found to cause autosomal recessive RP (arRP) in a few families. The 33 dominant mutations and 6 recessive RP1 mutations identified to date are all nonsense or frameshift mutations, and almost exclusively (38 out of 39) are located in the 4th and final exon of RP1. To better understand the underlying disease mechanisms of and help develop therapeutic strategies for RP1 disease, we performed a series of human genetic and animal studies using gene targeted and transgenic mice. Here we report that a frameshift mutation in the 3rd exon of RP1 (c.686delC; p.P229QfsX35) found in a patient with recessive RP1 disease causes RP in the homozygous state, whereas the heterozygous carriers are unaffected, confirming that haploinsufficiency is not the causative mechanism for RP1 disease. We then generated Rp1 knock-in mice with a nonsense Q662X mutation in exon 4, as well as Rp1 transgenic mice carrying a wild-type BAC Rp1 transgene. The Rp1-Q662X allele produces a truncated Rp1 protein, and homozygous Rp1-Q662X mice experience a progressive photoreceptor degeneration characterized disorganization of photoreceptor outer segments. This phenotype could be prevented by expression of a normal amount of Rp1 protein from the BAC transgene without removal of the mutant Rp1-Q662X protein. Over-expression of Rp1 protein in additional BAC Rp1 transgenic lines resulted in retinal degeneration. These findings suggest that the truncated Rp1-Q662X protein does not exert a toxic gain-of-function effect. These results also imply that in principle gene augmentation therapy could be beneficial for both recessive and dominant RP1 patients, but the levels of RP1 protein delivered for therapy will have to be carefully controlled.
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12
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Avila-Fernandez A, Corton M, Nishiguchi KM, Muñoz-Sanz N, Benavides-Mori B, Blanco-Kelly F, Riveiro-Alvarez R, Garcia-Sandoval B, Rivolta C, Ayuso C. Identification of an RP1 prevalent founder mutation and related phenotype in Spanish patients with early-onset autosomal recessive retinitis. Ophthalmology 2012; 119:2616-21. [PMID: 22917891 DOI: 10.1016/j.ophtha.2012.06.033] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Revised: 06/19/2012] [Accepted: 06/21/2012] [Indexed: 10/28/2022] Open
Abstract
OBJECTIVE To identify the genetic causes underlying early-onset autosomal recessive retinitis pigmentosa (arRP) in the Spanish population and describe the associated phenotype. DESIGN Case series. PARTICIPANTS A total of 244 unrelated families affected by early-onset arRP. METHODS Homozygosity mapping or exome sequencing analysis was performed in 3 families segregating arRP. A mutational screening was performed in 241 additional unrelated families for the p.Ser452Stop mutation. Haplotype analysis also was conducted. Individuals who were homozygotes, double heterozygotes, or carriers of mutations in RP1 underwent an ophthalmic evaluation to establish a genotype-phenotype correlation. MAIN OUTCOME MEASURES DNA sequence variants, homozygous regions, haplotypes, best-corrected visual acuity, visual field assessments, electroretinogram responses, and optical coherence tomography images. RESULTS Four novel mutations in RP1 were identified. The new mutation p.Ser542Stop was present in 11 of 244 (4.5%) of the studied families. All chromosomes harboring this mutation shared the same haplotype. All patients presented a common phenotype with an early age of onset and a prompt macular degeneration, whereas the heterozygote carriers did not show any signs of retinitis pigmentosa (RP). CONCLUSIONS p.Ser542Stop is a single founder mutation and the most prevalent described mutation in the Spanish population. It causes early-onset RP with a rapid macular degeneration and is responsible for 4.5% of all cases. Our data suggest that the implication of RP1 in arRP may be underestimated. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Audo I, Mohand-Saïd S, Dhaenens CM, Germain A, Orhan E, Antonio A, Hamel C, Sahel JA, Bhattacharya SS, Zeitz C. RP1 and autosomal dominant rod-cone dystrophy: Novel mutations, a review of published variants, and genotype-phenotype correlation. Hum Mutat 2011; 33:73-80. [DOI: 10.1002/humu.21640] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 10/06/2011] [Indexed: 01/19/2023]
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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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Danciger M, Yang H, Ralston R, Liu Y, Matthes MT, Peirce J, Lavail MM. Quantitative genetics of age-related retinal degeneration: a second F1 intercross between the A/J and C57BL/6 strains. Mol Vis 2007; 13:79-85. [PMID: 17277741 PMCID: PMC2503185] [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 Previously, several quantitative trait loci (QTL) that influence age-related retinal degeneration (ageRD) were demonstrated in a cross between the C57BL/6J-c(2J) and BALB/cByJ strains (B x C). In this study, as a complementary approach to ongoing recombinant progeny testing for the purpose of identifying candidate quantitative trait genes (QTG), a second test cross using the A/J and the pigmented C57BL/6J strains (A x B) was carried out. The albino A/J strain was selected because it had the most amount of ageRD among several inbred strains tested, and the pigmented C57BL/6J strain was selected because along with its coisogenic counterpart C57BL/6J-c(2J) it had the least amount of ageRD. Thus, the effect of pigment on ageRD could be tested at the same time that the C57BL/6 genetic background was kept in common between the crosses from the two studies for the purpose of comparison. METHODS A non-reciprocal F1 intercross between the A/J and C57BL/6J strains produced 170 F2 progeny. At 8 months of age after being maintained in relatively dim light, F2 mice, control mice and mice of other strains were evaluated for retinal degeneration by measurement of the thickness of the outer nuclear layer of the retina. The F2 mice were genotyped with dinucleotide repeat markers spanning the genome. Correlation of genotype with phenotype was made with Map Manager QTX software. RESULTS Comparison of several strains of mice including the pigmented strains 129S1/SvImJ and C57BL/6J and the albino strains A/J, NZW/LacJ, BALB/cByJ and C57BL/6J-c(2J), showed significant differences in ageRD. The greatest difference was between the albino A/J strain and the pigmented C57BL/6J strain. However, there was no significant difference between the pigmented C57BL/6J and its albino coisogenic counterpart C57BL/6J-c(2J). Neither was there significant difference between the pigmented and albino F2 mice from the A x B cross. On the other hand, F2 males had a small but significantly lower amount of ageRD than females. Several QTL were identified in the A x B cross but surprisingly none of the 3 major QTL present in the original B x C cross (Chrs 6, 10, and 16) was present. There were minor QTL on proximal Chr 12 and proximal Chr 14 in common between the two crosses, and the proximal Chr 12 QTL was present in a previous light damage study involving the B and C strains. At least one sex-limited QTL was present on the X chromosome with a peak in a different location from that of a sex-limited QTL in the previous B x C study. In addition, the protective X allele was from the BALB/cByJ strain in the B x C cross and from C57BL/6J in the A x B cross. In both crosses, the C57BL/6J X-chromosome allele was recessive. CONCLUSIONS Significant differences were observed in ageRD among several inbred strains of mice maintained in relatively dim light. AgeRD was not influenced by pigment but was influenced by gender, albeit to a small degree. The presence of the same QTL in one light-induced and two ageRD studies suggests at least partial commonality in retinal degeneration pathways of different primary cause. However, the three main QTL present in the B x C cross were absent from the A x B cross. This suggests that the genetic determinants responsible for the greater sensitivity to ageRD of BALB/cByJ and A/J relative to C57BL/6J are not the same. This is supported by the presence of sex-limited X-chromosome QTL in the two crosses in which the C57BL/6J allele is protective relative to the A allele and sensitive relative to the C allele. The findings in the two studies of differing allelic relationships of QTG, and differing QTL aid the identification of candidate genes mapping to critical QTL. Identifying natural modifying genes that influence retinal degeneration resulting from any causal pathway, especially those QTG that are protective, will open avenues of study that may lead to broad based therapies for people suffering retinal degenerative diseases.
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Affiliation(s)
- M Danciger
- Department of Biology, Loyola Marymount University, Los Angeles, CA 90045-2659, USA.
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