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Gerhardt MJ, Petersen-Jones SM, Michalakis S. CNG channel-related retinitis pigmentosa. Vision Res 2023; 208:108232. [PMID: 37054604 PMCID: PMC10373105 DOI: 10.1016/j.visres.2023.108232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/27/2023] [Accepted: 03/27/2023] [Indexed: 04/15/2023]
Abstract
The genes CNGA1 and CNGB1 encode the alpha and beta subunits of the rod CNG channel, a ligand-gated cation channel whose activity is controlled by cyclic guanosine monophosphate (cGMP). Autosomal inherited mutations in either of the genes lead to a progressive rod-cone retinopathy known as retinitis pigmentosa (RP). The rod CNG channel is expressed in the plasma membrane of the outer segment and functions as a molecular switch that converts light-mediated changes in cGMP into a voltage and Ca2+ signal. Here, we will first review the molecular properties and physiological role of the rod CNG channel and then discuss the characteristics of CNG-related RP. Finally, we will summarize recent activities in the field of gene therapy aimed at developing therapies for CNG-related RP.
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Affiliation(s)
- Maximilian J Gerhardt
- Department of Ophthalmology, University Hospital, LMU Munich, Mathildenstraße 8, 80336 München, Germany
| | - Simon M Petersen-Jones
- College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, United States
| | - Stylianos Michalakis
- Department of Ophthalmology, University Hospital, LMU Munich, Mathildenstraße 8, 80336 München, Germany.
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2
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Biology, Pathobiology and Gene Therapy of CNG Channel-Related Retinopathies. Biomedicines 2023; 11:biomedicines11020269. [PMID: 36830806 PMCID: PMC9953513 DOI: 10.3390/biomedicines11020269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 01/16/2023] [Accepted: 01/17/2023] [Indexed: 01/21/2023] Open
Abstract
The visual process begins with the absorption of photons by photopigments of cone and rod photoreceptors in the retina. In this process, the signal is first amplified by a cyclic guanosine monophosphate (cGMP)-based signaling cascade and then converted into an electrical signal by cyclic nucleotide-gated (CNG) channels. CNG channels are purely ligand-gated channels whose activity can be controlled by cGMP, which induces a depolarizing Na+/Ca2+ current upon binding to the channel. Structurally, CNG channels belong to the superfamily of pore-loop cation channels and share structural similarities with hyperpolarization-activated cyclic nucleotide (HCN) and voltage-gated potassium (KCN) channels. Cone and rod photoreceptors express distinct CNG channels encoded by homologous genes. Mutations in the genes encoding the rod CNG channel (CNGA1 and CNGB1) result in retinitis-pigmentosa-type blindness. Mutations in the genes encoding the cone CNG channel (CNGA3 and CNGB3) lead to achromatopsia. Here, we review the molecular properties of CNG channels and describe their physiological and pathophysiological roles in the retina. Moreover, we summarize recent activities in the field of gene therapy aimed at developing the first gene therapies for CNG channelopathies.
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Wagner JE, Zobel L, Gerhardt MJ, O'Riordan CR, Frederick A, Petersen-Jones SM, Biel M, Michalakis S. In vivo potency testing of subretinal rAAV5.hCNGB1 gene therapy in the Cngb1 knockout mouse model of retinitis pigmentosa. Hum Gene Ther 2021; 32:1158-1170. [PMID: 34376057 DOI: 10.1089/hum.2021.121] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Retinitis pigmentosa type 45 (RP45) is an autosomal-recessively inherited blinding disease caused by mutations in the cyclic nucleotide gated channel subunit beta 1 (CNGB1) gene. In this study, we developed and tested a novel gene supplementation therapy suitable for clinical translation. To this end, we designed a recombinant adeno-associated virus (rAAV) vector carrying a genome that features a novel human rhodopsin promoter (hRHO194) driving rod-specific expression of full-length human CNGB1 (rAAV5.hCNGB1). rAAV5.hCNGB1 was evaluated for efficacy in the Cngb1 knockout (Cngb1-/-) mouse model of RP45. In particular, increasing doses of rAAV5.hCNGB1 were delivered via single subretinal injection in 4-week-old Cngb1-/- mice and the treatment effect was assessed over a follow-up period of 9 months at the level of (i) retinal morphology, (ii) retinal function, (iii) vision-guided behavior, and (iv) transgene expression. We found that subretinal treatment with rAAV5.hCNGB1 resulted in efficient expression of the human CNGB1 protein in mouse rods and was able to normalize the expression of the endogenous mouse CNGA1 subunit, which together with CNGB1 forms the native heterotetrameric cGMP-gated cation channel in rod photoreceptors. The treatment led to a dose-dependent recovery of rod photoreceptor-driven function and preservation of retinal morphology in Cngb1-/- mice. In summary, these results demonstrate the efficacy of hCNGB1 gene supplementation therapy in the Cngb1-/- mouse model of RP45 and support the translation of this approach towards future clinical application.
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Affiliation(s)
- Johanna E Wagner
- Ludwig-Maximilians-Universität München, 9183, Department of Pharmacy - Center for Drug Research, Munich, Bayern, Germany;
| | - Lena Zobel
- Ludwig-Maximilians-Universität München, 9183, Department of Pharmacy - Center for Drug Research, Munich, Bayern, Germany.,Ludwig-Maximilians-Universität München, 9183, University Hospital - Department of Ophthalmology, Munich, Bayern, Germany;
| | - Maximilian Joachim Gerhardt
- Ludwig-Maximilians-Universität München, 9183, University Hospital - Department of Ophthalmology, Munich, Bayern, Germany;
| | - Catherine R O'Riordan
- Sanofi Genzyme, 2194, Gene Therapy, Rare Diseases, Framingham, Massachusetts, United States; Catherine.O'
| | - Amy Frederick
- Sanofi Genzyme, 2194, Gene Therapy, Rare Diseases, Framingham, Massachusetts, United States;
| | - Simon M Petersen-Jones
- Michigan State University, Veterinary Medical Center, East Lansing, Michigan, United States;
| | - Martin Biel
- Ludwig-Maximilians-Universität München, 9183, Department of Pharmacy - Center for Drug Research, Munich, Bayern, Germany;
| | - Stylianos Michalakis
- Ludwig-Maximilians-Universität München, 9183, Department of Pharmacy - Center for Drug Research, Munich, Bayern, Germany.,Ludwig-Maximilians-Universität München, 9183, University Hospital - Department of Ophthalmology, Munich, Bayern, Germany;
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Nassisi M, Smirnov VM, Solis Hernandez C, Mohand‐Saïd S, Condroyer C, Antonio A, Kühlewein L, Kempf M, Kohl S, Wissinger B, Nasser F, Ragi SD, Wang N, Sparrow JR, Greenstein VC, Michalakis S, Mahroo OA, Ba‐Abbad R, Michaelides M, Webster AR, Degli Esposti S, Saffren B, Capasso J, Levin A, Hauswirth WW, Dhaenens C, Defoort‐Dhellemmes S, Tsang SH, Zrenner E, Sahel J, Petersen‐Jones SM, Zeitz C, Audo I. CNGB1-related rod-cone dystrophy: A mutation review and update. Hum Mutat 2021; 42:641-666. [PMID: 33847019 PMCID: PMC8218941 DOI: 10.1002/humu.24205] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 03/26/2021] [Accepted: 04/08/2021] [Indexed: 12/29/2022]
Abstract
Cyclic nucleotide-gated channel β1 (CNGB1) encodes the 240-kDa β subunit of the rod photoreceptor cyclic nucleotide-gated ion channel. Disease-causing sequence variants in CNGB1 lead to autosomal recessive rod-cone dystrophy/retinitis pigmentosa (RP). We herein present a comprehensive review and analysis of all previously reported CNGB1 sequence variants, and add 22 novel variants, thereby enlarging the spectrum to 84 variants in total, including 24 missense variants (two of which may also affect splicing), 21 nonsense, 19 splicing defects (7 at noncanonical positions), 10 small deletions, 1 small insertion, 1 small insertion-deletion, 7 small duplications, and 1 gross deletion. According to the American College of Medical Genetics and Genomics classification criteria, 59 variants were considered pathogenic or likely pathogenic and 25 were variants of uncertain significance. In addition, we provide further phenotypic data from 34 CNGB1-related RP cases, which, overall, are in line with previous findings suggesting that this form of RP has long-term retention of useful central vision despite the early onset of night blindness, which is valuable for patient counseling, but also has implications for it being considered a priority target for gene therapy trials.
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Affiliation(s)
- Marco Nassisi
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
- Centre Hospitalier National d'Ophtalmologie des Quinze‐Vingts, INSERM‐DGOS CIC1423ParisFrance
- Department of Clinical Sciences and Community HealthUniversity of MilanMilanItaly
- Ophthalmological Unit, Fondazione IRCCS Ca' GrandaOspedale Maggiore PoliclinicoMilanItaly
| | - Vasily M. Smirnov
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
- Exploration de la vision et Neuro‐Ophthalmologie, CHU de LilleLilleFrance
- Faculté de MédecineUniversité de LilleLilleFrance
| | - Cyntia Solis Hernandez
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
| | - Saddek Mohand‐Saïd
- Centre Hospitalier National d'Ophtalmologie des Quinze‐Vingts, INSERM‐DGOS CIC1423ParisFrance
| | - Christel Condroyer
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
| | - Aline Antonio
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
| | - Laura Kühlewein
- University Eye Hospital, Centre for OphthalmologyUniversity of TübingenTübingenGermany
- Institute for Ophthalmic Research, Centre for OphthalmologyUniversity of TübingenTübingenGermany
| | - Melanie Kempf
- University Eye Hospital, Centre for OphthalmologyUniversity of TübingenTübingenGermany
| | - Susanne Kohl
- Institute for Ophthalmic Research, Centre for OphthalmologyUniversity of TübingenTübingenGermany
| | - Bernd Wissinger
- Institute for Ophthalmic Research, Centre for OphthalmologyUniversity of TübingenTübingenGermany
| | - Fadi Nasser
- University Eye Hospital, Centre for OphthalmologyUniversity of TübingenTübingenGermany
| | - Sara D. Ragi
- Department of OphthalmologyColumbia University, New YorkNew YorkUSA
| | - Nan‐Kai Wang
- Department of OphthalmologyColumbia University, New YorkNew YorkUSA
- College of MedicineChang Gung UniversityTaoyuanTaiwan
- Department of Ophthalmology, Chang Gung Memorial HospitalLinkou Medical CenterTaoyuanTaiwan
| | - Janet R. Sparrow
- Department of OphthalmologyColumbia University, New YorkNew YorkUSA
| | | | | | - Omar A. Mahroo
- Moorfields Eye HospitalLondonUK
- UCL Institute of Ophthalmology, University College LondonLondonUK
| | - Rola Ba‐Abbad
- Moorfields Eye HospitalLondonUK
- UCL Institute of Ophthalmology, University College LondonLondonUK
| | - Michel Michaelides
- Moorfields Eye HospitalLondonUK
- UCL Institute of Ophthalmology, University College LondonLondonUK
| | - Andrew R. Webster
- Moorfields Eye HospitalLondonUK
- UCL Institute of Ophthalmology, University College LondonLondonUK
| | - Simona Degli Esposti
- Moorfields Eye HospitalLondonUK
- UCL Institute of Ophthalmology, University College LondonLondonUK
| | - Brooke Saffren
- Philadelphia College of Osteopathic MedicinePhiladelphiaPennsylvaniaUSA
| | | | - Alex Levin
- Pediatric Ophthalmology and Ocular Genetics, Flaum Eye Institute, Pediatric Genetics, Golisano Children's HospitalUniversity of RochesterRochesterNew YorkUSA
| | | | - Claire‐Marie Dhaenens
- Univ. Lille, Inserm, CHU Lille, U1172‐LilNCog‐Lille Neuroscience & CognitionLilleFrance
| | | | - Stephen H. Tsang
- Department of OphthalmologyColumbia University, New YorkNew YorkUSA
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma LaboratoryNew YorkNew YorkUSA
- Department of Pathology and Cell BiologyColumbia UniversityNew YorkNew YorkUSA
- Stem Cell Initiative (CSCI), Institute of Human Nutrition, Vagelos College of Physicians and SurgeonsNew YorkNew YorkUSA
| | - Eberhart Zrenner
- University Eye Hospital, Centre for OphthalmologyUniversity of TübingenTübingenGermany
| | - Jose‐Alain Sahel
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
- Department of OphthalmologyThe University of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
- Fondation Ophtalmologique Adolphe de RothschildParisFrance
| | - Simon M. Petersen‐Jones
- Department of Small Animal Clinical SciencesMichigan State UniversityEast LansingMichiganUSA
| | - Christina Zeitz
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
| | - Isabelle Audo
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche ScientifiqueInstitut de la VisionParisFrance
- Centre Hospitalier National d'Ophtalmologie des Quinze‐Vingts, INSERM‐DGOS CIC1423ParisFrance
- University College London Institute of OphthalmologyLondonUK
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Identification of a CNGB1 Frameshift Mutation in a Han Chinese Family with Retinitis Pigmentosa. Optom Vis Sci 2019; 95:1155-1161. [PMID: 30451805 DOI: 10.1097/opx.0000000000001305] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
SIGNIFICANCE Retinitis pigmentosa (RP) is a severe hereditary retinal disorder characterized by progressive degeneration of rod and cone photoreceptors. This study identified a novel frameshift mutation, c.385delC, p.(L129WfsTer148), in the cyclic nucleotide-gated channel beta 1 (CNGB1) gene of a consanguineous Han Chinese family with autosomal recessive RP (arRP). This expands the spectrum of CNGB1 gene variants in RP cases and possibly refines future genetic counseling. PURPOSE The present study sought to identify potential pathogenetic gene mutations in a five-generation consanguineous Han Chinese family with RP. METHODS Two members of a five-generation consanguineous Han Chinese pedigree with arRP and 100 normal individuals were enrolled in this study. Exome sequencing was performed on the 70-year-old male proband from a consanguineous family to screen potential pathogenic mutations according to the American College of Medical Genetics and Genomics for the interpretation of sequence variants. Sanger sequencing was performed on the proband, the proband's unaffected son, and 100 normal individuals to verify the disease-causing mutation. RESULTS A novel frameshift mutation, c.385delC, p.(L129WfsTer148), with homozygous status in the CNGB1 gene was identified in the proband of the family with arRP, and the mutation with heterozygous status was carried by the asymptomatic son. CONCLUSIONS The c.385delC (p.(L129WfsTer148)) mutation in the CNGB1 gene screened by exome sequencing is probably responsible for the RP phenotype in this family. The result expands the spectrum of CNGB1 gene variants in RP cases and possibly refines future genetic counseling.
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Abstract
The first step in vision is the absorption of photons by the photopigments in cone and rod photoreceptors. After initial amplification within the phototransduction cascade the signal is translated into an electrical signal by the action of cyclic nucleotide-gated (CNG) channels. CNG channels are ligand-gated ion channels that are activated by the binding of cyclic guanosine monophosphate (cGMP) or cyclic adenosine monophosphate (cAMP). Retinal CNG channels transduce changes in intracellular concentrations of cGMP into changes of the membrane potential and the Ca2+ concentration. Structurally, the CNG channels belong to the superfamily of pore-loop cation channels and share a common gross structure with hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and voltage-gated potassium channels (KCN). In this review, we provide an overview on the molecular properties of CNG channels and describe their physiological role in the phototransduction pathways. We also discuss insights into the pathophysiological role of CNG channel proteins that have emerged from the analysis of CNG channel-deficient animal models and human CNG channelopathies. Finally, we summarize recent gene therapy activities and provide an outlook for future clinical application.
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Affiliation(s)
- Stylianos Michalakis
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr, 5-13, 81377 Munich, Germany.
| | - Elvir Becirovic
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr, 5-13, 81377 Munich, Germany.
| | - Martin Biel
- Center for Integrated Protein Science Munich (CIPSM), Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr, 5-13, 81377 Munich, Germany.
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Chakraborty D, Conley SM, Pittler SJ, Naash MI. Role of RDS and Rhodopsin in Cngb1-Related Retinal Degeneration. Invest Ophthalmol Vis Sci 2016; 57:787-97. [PMID: 26934134 PMCID: PMC4777275 DOI: 10.1167/iovs.15-18516] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Rod photoreceptor outer segment (OS) morphogenesis, structural integrity, and proper signal transduction rely on critical proteins found in the different OS membrane domains (e.g., plasma, disc, and disc rim membrane). Among these key elements are retinal degeneration slow (RDS, also known as peripherin-2), rhodopsin, and the beta subunit of the cyclic nucleotide gated channel (CNGB1a), which have been found to interact in a complex. The purpose of this study was to evaluate the potential interplay between these three proteins by examining retinal disease phenotypes in animal models expressing varying amounts of CNGB1a, rhodopsin, and RDS. Methods Outer segment trafficking, retinal function, and photoreceptor structure were evaluated using knockout mouse lines. Results Eliminating Cngb1 and reducing RDS leads to additive defects in RDS expression levels and rod electroretinogram (ERG) function, (e.g., Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−) but not to additive defects in rod ultrastructure. These additive effects also manifested in cone function: Photopic ERG responses were significantly lower in the Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−, suggesting that eliminating Cngb1 can accelerate the cone degeneration that usually presents later in the rds+/−. This was not the case with rhodopsin; reducing rhodopsin levels in concert with eliminating CNGB1a did not lead to phenotypes more severe than those observed in the Cngb1 knockout alone. Conclusions These data support a role for RDS as the core component of a multiprotein plasma membrane-rim-disc complex that has both a structural role in photoreceptor OS formation and maintenance and a functional role in orienting proteins for optimal signal transduction.
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Affiliation(s)
- Dibyendu Chakraborty
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Steven J Pittler
- Department of Vision Sciences, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
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Metzler-Guillemain C, Victorero G, Lepoivre C, Bergon A, Yammine M, Perrin J, Sari-Minodier I, Boulanger N, Rihet P, Nguyen C. Sperm mRNAs and microRNAs as candidate markers for the impact of toxicants on human spermatogenesis: an application to tobacco smoking. Syst Biol Reprod Med 2015; 61:139-49. [PMID: 25821920 DOI: 10.3109/19396368.2015.1022835] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Spermatozoa contain a complex population of RNAs including messenger RNAs (mRNAs) and small RNAs such as microRNAs (miRNA). It has been reported that these RNAs can be used to understand the mechanisms by which toxicological exposure affects spermatogenesis. The aim of our study was to compare mRNA and miRNA profiles in spermatozoa from eight smokers and eight non-smokers, and search for potential relationships between mRNA and miRNA variation. All men were selected based on their answers to a standard toxic exposure questionnaire, and sperm parameters. Using mRNA and miRNA microarrays, we showed that mRNAs from 15 genes were differentially represented between smokers and non-smokers (p<0.01): five had higher levels and 10 lower levels in the smokers. For the microRNAs, 23 were differentially represented: 16 were higher and seven lower in the smokers (0.004≤p<0.01). Quantitative RT-PCR confirmed the lower levels in smokers compared to non-smokers for hsa-miR-296-5p, hsa-miR-3940, and hsa-miR-520d-3p. Moreover, we observed an inverse relationship between the levels of microRNAs and six potential target mRNAs (B3GAT3, HNRNPL, OASL, ODZ3, CNGB1, and PKD2). Our results indicate that alterations in the level of a small number of microRNAs in response to smoking may contribute to changes in mRNA expression in smokers. We conclude that large-scale analysis of spermatozoa RNAs can be used to help understand the mechanisms by which human spermatogenesis responds to toxic substances including those in tobacco smoke.
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Winkler PA, Ekenstedt KJ, Occelli LM, Frattaroli AV, Bartoe JT, Venta PJ, Petersen-Jones SM. A large animal model for CNGB1 autosomal recessive retinitis pigmentosa. PLoS One 2013; 8:e72229. [PMID: 23977260 PMCID: PMC3747135 DOI: 10.1371/journal.pone.0072229] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 07/08/2013] [Indexed: 11/25/2022] Open
Abstract
Retinal dystrophies in dogs are invaluable models of human disease. Progressive retinal atrophy (PRA) is the canine equivalent of retinitis pigmentosa (RP). Similar to RP, PRA is a genetically heterogenous condition. We investigated PRA in the Papillon breed of dog using homozygosity mapping and haplotype construction of single nucleotide polymorphisms within a small family group to identify potential positional candidate genes. Based on the phenotypic similarities between the PRA-affected Papillons, mouse models and human patients, CNGB1 was selected as the most promising positional candidate gene. CNGB1 was sequenced and a complex mutation consisting of the combination of a one basepair deletion and a 6 basepair insertion was identified in exon 26 (c.2387delA;2389_2390insAGCTAC) leading to a frameshift and premature stop codon. Immunohistochemistry (IHC) of pre-degenerate retinal sections from a young affected dog showed absence of labeling using a C-terminal CNGB1 antibody. Whereas an antibody directed against the N-terminus of the protein, which also recognizes the glutamic acid rich proteins arising from alternative splicing of the CNGB1 transcript (upstream of the premature stop codon), labeled rod outer segments. CNGB1 combines with CNGA1 to form the rod cyclic nucleotide gated channel and previous studies have shown the requirement of CNGB1 for normal targeting of CNGA1 to the rod outer segment. In keeping with these previous observations, IHC showed a lack of detectable CNGA1 protein in the rod outer segments of the affected dog. A population study did not identify the CNGB1 mutation in PRA-affected dogs in other breeds and documented that the CNGB1 mutation accounts for ∼70% of cases of Papillon PRA in our PRA-affected canine DNA bank. CNGB1 mutations are one cause of autosomal recessive RP making the CNGB1 mutant dog a valuable large animal model of the condition.
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Affiliation(s)
- Paige A. Winkler
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America
- Genetics Program, Michigan State University, East Lansing, Michigan, United States of America
| | - Kari J. Ekenstedt
- Department of Animal and Food Sciences, University of Wisconsin-River Falls, River Falls, Wisconsin, United States of America
| | - Laurence M. Occelli
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America
| | - Anton V. Frattaroli
- Health Information Technology, Michigan State University, East Lansing, Michigan, United States of America
| | - Joshua T. Bartoe
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America
| | - Patrick J. Venta
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America
- Genetics Program, Michigan State University, East Lansing, Michigan, United States of America
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
| | - Simon M. Petersen-Jones
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America
- Genetics Program, Michigan State University, East Lansing, Michigan, United States of America
- * E-mail:
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Schön C, Biel M, Michalakis S. Gene replacement therapy for retinal CNG channelopathies. Mol Genet Genomics 2013; 288:459-67. [DOI: 10.1007/s00438-013-0766-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 06/25/2013] [Indexed: 12/20/2022]
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