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Sechrest ER, Chmelik K, Tan WD, Deng WT. Blue cone monochromacy and gene therapy. Vision Res 2023; 208:108221. [PMID: 37001420 PMCID: PMC10182257 DOI: 10.1016/j.visres.2023.108221] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 03/30/2023]
Abstract
Blue cone monochromacy (BCM) is a congenital vision disorder characterized by complete loss or severely reduced long- and middle-wavelength cone function, caused by mutations in the OPN1LW/OPN1MW gene cluster on the X-chromosome. BCM patients typically suffer from poor visual acuity, severely impaired color discrimination, myopia, and nystagmus. In this review, we cover the genetic causes of BCM, clinical features of BCM patients, genetic testing, and clinical outcome measurements for future BCM clinical trials. However, our emphasis is on detailing the animal models for BCM and gene therapy using adeno-associated vectors (AAV). We describe two mouse models resembling the two most common causes of BCM, current progress in proof-of-concept studies to treat BCM with deletion mutations, the challenges we face, and future directions.
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Affiliation(s)
- Emily R Sechrest
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26505, United States
| | - Kathryn Chmelik
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26505, United States; Department of Biochemistry, West Virginia University, Morgantown, WV 26505, United States
| | - Wendy D Tan
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26505, United States
| | - Wen-Tao Deng
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26505, United States; Department of Biochemistry, West Virginia University, Morgantown, WV 26505, United States.
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Iarossi G, Coppè AM, Passarelli C, Maltese PE, Sinibaldi L, Cappelli A, Cetola S, Novelli A, Buzzonetti L. Blue Cone Monochromatism with Foveal Hypoplasia Caused by the Concomitant Effect of Variants in OPN1LW/OPN1MW and GPR143 Genes. Int J Mol Sci 2021; 22:ijms22168617. [PMID: 34445325 PMCID: PMC8395340 DOI: 10.3390/ijms22168617] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 08/04/2021] [Accepted: 08/04/2021] [Indexed: 12/11/2022] Open
Abstract
Blue cone monochromatism (BCM) is an X-linked recessive cone dysfunction disorder caused by mutations in the OPN1LW/OPN1MW gene cluster, encoding long (L)- and middle (M)-wavelength-sensitive cone opsins. Here, we report on the unusual clinical presentation of BCM caused by a novel mutation in the OPN1LW gene in a young man. We describe in detail the phenotype of the proband, and the subclinical morpho-functional anomalies shown by his carrier mother. At a clinical level, the extensive functional evaluation demonstrated in the proband the M/L cone affection and the sparing of S-cone function, distinctive findings of BCM. Interestingly, spectral-domain optical coherence tomography showed the presence of foveal hypoplasia with focal irregularities of the ellipsoid layer in the foveal area, reported to be associated with some cases of cone-rod dystrophy and achromatopsia. At a molecular level, we identified the novel mutation c.427T > C p.(Ser143Pro) in the OPN1LW gene and the common missense mutation c.607T > C (p.Cys203Arg) in the OPN1MW gene. In addition, we discovered the c.768-2_769delAGTT splicing variant in the GPR143 gene. To our knowledge, this is the first case of foveal hypoplasia in a BCM patient and of mild clinical affection in a female carrier caused by the concomitant effect of variants in OPN1LW/OPN1MW and GPR143 genes, thus as the result of the simultaneous action of two independent genetic defects.
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Affiliation(s)
- Giancarlo Iarossi
- Department of Ophthalmology, Bambino Gesù Children’s Hospital, 00165 Rome, Italy; (A.M.C.); (A.C.); (L.B.)
- Correspondence: (G.I.); (P.E.M.); Tel.: +39-06-6859-3362 (G.I.); +39-04-6442-0795 (P.E.M.)
| | - Andrea Maria Coppè
- Department of Ophthalmology, Bambino Gesù Children’s Hospital, 00165 Rome, Italy; (A.M.C.); (A.C.); (L.B.)
| | - Chiara Passarelli
- Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy; (C.P.); (L.S.); (S.C.); (A.N.)
| | - Paolo Enrico Maltese
- MAGI’S Lab s.r.l., 38068 Rovereto, Italy
- Correspondence: (G.I.); (P.E.M.); Tel.: +39-06-6859-3362 (G.I.); +39-04-6442-0795 (P.E.M.)
| | - Lorenzo Sinibaldi
- Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy; (C.P.); (L.S.); (S.C.); (A.N.)
- Rare Disease and Medical Genetics, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy
| | - Alessandro Cappelli
- Department of Ophthalmology, Bambino Gesù Children’s Hospital, 00165 Rome, Italy; (A.M.C.); (A.C.); (L.B.)
| | - Sarah Cetola
- Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy; (C.P.); (L.S.); (S.C.); (A.N.)
| | - Antonio Novelli
- Translational Cytogenomics Research Unit, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy; (C.P.); (L.S.); (S.C.); (A.N.)
| | - Luca Buzzonetti
- Department of Ophthalmology, Bambino Gesù Children’s Hospital, 00165 Rome, Italy; (A.M.C.); (A.C.); (L.B.)
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Semenov EP, Sheplock R, Roman AJ, McGuigan DB, Swider M, Cideciyan AV, Jacobson SG. Reading Performance in Blue Cone Monochromacy: Defining an Outcome Measure for a Clinical Trial. Transl Vis Sci Technol 2020; 9:13. [PMID: 33344057 PMCID: PMC7726588 DOI: 10.1167/tvst.9.13.13] [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: 07/20/2020] [Accepted: 10/12/2020] [Indexed: 11/24/2022] Open
Abstract
Purpose Blue cone monochromacy (BCM), a congenital X-linked retinal disease caused by mutations in the OPN1LW/OPN1MW gene cluster, is under consideration for intravitreal gene therapy. Difficulties with near vision tasks experienced by these patients prompted this study of reading performance as a potential outcome measure for a future clinical trial. Methods Clinically and molecularly diagnosed patients with BCM (n = 17; ages 15–63 years) and subjects with normal vision (n = 22; ages 18–72 years) were examined with the MNREAD acuity chart for both uniocular and binocular conditions. Parameters derived from the measurements in patients were compared with normal data and also within the group of patients. Intersession, interocular and between-subject variabilities were determined. The frequent complaint of light sensitivity in BCM was examined by comparing results from black text on a white background (regular polarity) versus white on black (reverse polarity) conditions. Results MNREAD curves of print size versus reading speed were right-shifted compared with normal in all patients with BCM. All parameters in patients with BCM indicated abnormal reading performance. Intersession variability was slightly higher in BCM than in normal, but comparable with results previously reported for other patients with maculopathies. There was a high degree of disease symmetry in reading performance in this BCM cohort. Reverse polarity showed better reading parameters than regular polarity in 82% of the patients. Conclusions MNREAD measures of reading performance in patients with BCM would be a worthy and robust secondary outcome in a clinical trial protocol, given its dual purpose of quantifying macular vision and addressing an important quality of life issue. Translational Relevance Assessment of an outcome for a clinical trial.
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Affiliation(s)
- Evelyn P Semenov
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
| | - Rebecca Sheplock
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
| | - Alejandro J Roman
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
| | - David B McGuigan
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
| | - Malgorzata Swider
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
| | - Artur V Cideciyan
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
| | - Samuel G Jacobson
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, USA
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Vinberg F, Chen J, Kefalov VJ. Regulation of calcium homeostasis in the outer segments of rod and cone photoreceptors. Prog Retin Eye Res 2018; 67:87-101. [PMID: 29883715 DOI: 10.1016/j.preteyeres.2018.06.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 05/30/2018] [Accepted: 06/04/2018] [Indexed: 12/11/2022]
Abstract
Calcium plays important roles in the function and survival of rod and cone photoreceptor cells. Rapid regulation of calcium in the outer segments of photoreceptors is required for the modulation of phototransduction that drives the termination of the flash response as well as light adaptation in rods and cones. On a slower time scale, maintaining proper calcium homeostasis is critical for the health and survival of photoreceptors. Decades of work have established that the level of calcium in the outer segments of rods and cones is regulated by a dynamic equilibrium between influx via the transduction cGMP-gated channels and extrusion via rod- and cone-specific Na+/Ca2+, K+ exchangers (NCKXs). It had been widely accepted that the only mechanism for extrusion of calcium from rod outer segments is via the rod-specific NCKX1, while extrusion from cone outer segments is driven exclusively by the cone-specific NCKX2. However, recent evidence from mice lacking NCKX1 and NCKX2 have challenged that notion and have revealed a more complex picture, including a NCKX-independent mechanism in rods and two separate NCKX-dependent mechanisms in cones. This review will focus on recent findings on the molecular mechanisms of extrusion of calcium from the outer segments of rod and cone photoreceptors, and the functional and structural changes in photoreceptors when normal extrusion is disrupted.
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Affiliation(s)
- Frans Vinberg
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA; John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA
| | - Jeannie Chen
- Zilkha Neurogenetic Institute, Department of Physiology and Neuroscience, University of Southern California Keck School of Medicine, Los Angeles, CA, USA
| | - Vladimir J Kefalov
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA.
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Deng WT, Li J, Zhu P, Chiodo VA, Smith WC, Freedman B, Baehr W, Pang J, Hauswirth WW. Human L- and M-opsins restore M-cone function in a mouse model for human blue cone monochromacy. Mol Vis 2018; 24:17-28. [PMID: 29386880 PMCID: PMC5757852] [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] [Received: 09/26/2017] [Accepted: 01/05/2018] [Indexed: 11/03/2022] Open
Abstract
Purpose Blue cone monochromacy (BCM) is an X-linked congenital vision disorder characterized by complete loss or severely reduced L- and M-cone function. Patients with BCM display poor visual acuity, severely impaired color discrimination, myopia, nystagmus, and minimally detectable cone-mediated electroretinogram. Recent studies of patients with BCM with adaptive optics scanning laser ophthalmoscopy (AOSLO) showed that they have a disrupted cone mosaic with reduced numbers of cones in the fovea that is normally dominated by L- and M-cones. The remaining cones in the fovea have significantly shortened outer segments but retain sufficient structural integrity to serve as potential gene therapy targets. In this study, we tested whether exogenously expressed human L- and M-opsins can rescue M-cone function in an M-opsin knockout (Opn1mw-/- ) mouse model for BCM. Methods Adeno-associated virus type 5 (AAV5) vectors expressing OPN1LW, OPN1MW, or C-terminal tagged OPN1LW-Myc, or OPN1MW-HA driven by a cone-specific promoter were injected subretinally into one eye of Opn1mw-/- mice, while the contralateral eye served as the uninjected control. Expression of cone pigments was determined with western blotting and their cellular localization identified with immunohistochemistry. M-cone function was analyzed with electroretinogram (ERG). Antibodies against cone phototransduction proteins were used to study cone outer segment (OS) morphology in untreated and treated Opn1mw-/- eyes. Results We showed that cones in the dorsal retina of the Opn1mw-/- mouse do not form outer segments, resembling cones that lack outer segments in the human BCM fovea. We further showed that AAV5-mediated expression of either human M- or L-opsin individually or combined promotes regrowth of cone outer segments and rescues M-cone function in the treated Opn1mw-/- dorsal retina. Conclusions Exogenously expressed human opsins can regenerate cone outer segments and rescue M-cone function in Opn1mw-/- mice, thus providing a proof-of-concept gene therapy in an animal model of BCM.
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Affiliation(s)
- Wen-Tao Deng
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - Jie Li
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - Ping Zhu
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - Vince A. Chiodo
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - W. Clay Smith
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - Beau Freedman
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - Wolfgang Baehr
- Department of Ophthalmology and Visual Science, Salt Lake City, UT
- Department of Neurobiology and Anatomy, Salt Lake City, UT
- Department of Biology, University of Utah, Salt Lake City, UT
| | - Jijing Pang
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
| | - William W. Hauswirth
- Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, FL
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Luo X, Cideciyan AV, Iannaccone A, Roman AJ, Ditta LC, Jennings BJ, Yatsenko SA, Sheplock R, Sumaroka A, Swider M, Schwartz SB, Wissinger B, Kohl S, Jacobson SG. Blue cone monochromacy: visual function and efficacy outcome measures for clinical trials. PLoS One 2015; 10:e0125700. [PMID: 25909963 PMCID: PMC4409040 DOI: 10.1371/journal.pone.0125700] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 03/21/2015] [Indexed: 12/22/2022] Open
Abstract
Background Blue Cone Monochromacy (BCM) is an X-linked retinopathy caused by mutations in the OPN1LW / OPN1MW gene cluster, encoding long (L)- and middle (M)-wavelength sensitive cone opsins. Recent evidence shows sufficient structural integrity of cone photoreceptors in BCM to warrant consideration of a gene therapy approach to the disease. In the present study, the vision in BCM is examined, specifically seeking clinically-feasible outcomes for a future clinical trial. Methods BCM patients (n = 25, ages 5–72) were studied with kinetic and static chromatic perimetry, full-field sensitivity testing, and eye movement recordings. Vision at the fovea and parafovea was probed with chromatic microperimetry. Results Kinetic fields with a Goldmann size V target were generally full. Short-wavelength (S-) sensitive cone function was normal or near normal in most patients. Light-adapted perimetry results on conventional background lights were abnormally reduced; 600-nm stimuli were seen by rods whereas white stimuli were seen by both rods and S-cones. Under dark-adapted conditions, 500-nm stimuli were seen by rods in both BCM and normals. Spectral sensitivity functions in the superior retina showed retained rod and S-cone functions in BCM under dark-adapted and light-adapted conditions. In the fovea, normal subjects showed L/M-cone mediation using a 650-nm stimulus under dark-adapted conditions, whereas BCM patients had reduced sensitivity driven by rod vision. Full-field red stimuli on bright blue backgrounds were seen by L/M-cones in normal subjects whereas BCM patients had abnormally reduced and rod-mediated sensitivities. Fixation location could vary from fovea to parafovea. Chromatic microperimetry demonstrated a large loss of sensitivity to red stimuli presented on a cyan adapting background at the anatomical fovea and surrounding parafovea. Conclusions BCM rods continue to signal vision under conditions normally associated with daylight vision. Localized and retina-wide outcome measures were examined to evaluate possible improvement of L/M-cone-based vision in a clinical trial.
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Affiliation(s)
- Xunda Luo
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Artur V. Cideciyan
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (SGJ); (AVC)
| | - Alessandro Iannaccone
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Alejandro J. Roman
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Lauren C. Ditta
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Barbara J. Jennings
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Svetlana A. Yatsenko
- Pittsburgh Cytogenetics Laboratory, Center for Medical Genetics and Genomics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Rebecca Sheplock
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alexander Sumaroka
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Malgorzata Swider
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Sharon B. Schwartz
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Bernd Wissinger
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Susanne Kohl
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Samuel G. Jacobson
- Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (SGJ); (AVC)
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Aboshiha J, Luong V, Cowing J, Dubis AM, Bainbridge JW, Ali RR, Webster AR, Moore AT, Fitzke FW, Michaelides M. Dark-adaptation functions in molecularly confirmed achromatopsia and the implications for assessment in retinal therapy trials. Invest Ophthalmol Vis Sci 2014; 55:6340-9. [PMID: 25168900 DOI: 10.1167/iovs.14-14910] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
PURPOSE To describe the dark-adaptation (DA) functions in subjects with molecularly proven achromatopsia (ACHM) using refined testing conditions with a view to guiding assessment in forthcoming gene therapy trials. METHODS The DA functions of nine subjects with ACHM were measured and compared with those of normal observers. The size and retinal location of the stimuli used to measure DA sensitivities were varied in four distinct testing condition sets, and the effect of altering these parameters assessed. RESULTS In three of the four testing condition sets, achromats had significantly higher mean final thresholds than normal observers, whereas in the fourth condition set they did not. A larger, more central stimulus revealed the greatest difference between the final DA thresholds of achromat and normal subjects, and also demonstrated the slowest rate of recovery among the achromat group. CONCLUSIONS In this, the largest study of DA functions in molecularly proven ACHM to date, we have identified optimal testing conditions that accentuate the relative difference between achromats and normal observers. These findings can help optimize DA testing in future trials, as well as help resolve the dichotomy in the literature regarding the normality or otherwise of DA functions in ACHM. Furthermore, the shorter testing time and less intense adaptation light used in these experiments may prove advantageous for more readily and reliably probing scotopic function in retinal disease, and be particularly valuable in the frequent post therapeutic assessments required in the context of the marked photophobia in ACHM.
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Affiliation(s)
- Jonathan Aboshiha
- UCL Institute of Ophthalmology, University College London, London, United Kingdom Moorfields Eye Hospital, London, United Kingdom
| | - Vy Luong
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Jill Cowing
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Adam M Dubis
- UCL Institute of Ophthalmology, University College London, London, United Kingdom Moorfields Eye Hospital, London, United Kingdom
| | - James W Bainbridge
- UCL Institute of Ophthalmology, University College London, London, United Kingdom Moorfields Eye Hospital, London, United Kingdom
| | - Robin R Ali
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Andrew R Webster
- UCL Institute of Ophthalmology, University College London, London, United Kingdom Moorfields Eye Hospital, London, United Kingdom
| | - Anthony T Moore
- UCL Institute of Ophthalmology, University College London, London, United Kingdom Moorfields Eye Hospital, London, United Kingdom
| | - Frederick W Fitzke
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London, London, United Kingdom Moorfields Eye Hospital, London, United Kingdom
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Meso AI, Hess RF. Evidence for multiple extra-striate mechanisms behind perception of visual motion gradients. Vision Res 2012; 64:42-8. [PMID: 22659589 DOI: 10.1016/j.visres.2012.05.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 03/23/2012] [Accepted: 05/19/2012] [Indexed: 11/30/2022]
Abstract
Perceiving motion patterns in visual scenes in which speed or motion direction varies over space while average luminance remains constant presents a processing task that requires at least two separate stages of neural spatio-temporal filtering. We have previously probed the transfer of information between these stages of filtering identifying a largely scale invariant process in which narrowband initial motion sensitive filters are coupled with a broad range of spatial frequencies of secondary filters, with an optimal coupling - in terms of optimal observer visual sensitivity - at a frequency ratio of around twelve. In the current work, we used the same stimulus to investigate the possible presence of multiple secondary filtering mechanisms and their associated bandwidths. Using a forced choice psychophysical task with both a detection and an identification component, we presented experimental blocks containing stimuli with one of two different modulator frequencies in each trial to measure the frequency difference at which the detection performance matched the identification of the frequency. We found that at a frequency differences of about 2.2 octaves, performance of both tasks was similar, and the processing could therefore be inferred to occur in independent frequency channels. The same observation was confirmed for stimuli presented at a longer viewing distance. We conclude that for the motion gradient stimuli, there are secondary filtering mechanisms with a moderately broad bandwidth of over 2 octaves that underlie our sensitivity for detecting motion gradients of different modulation frequency. These are likely to be implemented at least in part within the dorsal stream of extra-striate cortex.
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Affiliation(s)
- Andrew Isaac Meso
- McGill Vision Research, Department of Ophthalmology, McGill University, 687 Pine Avenue West Rm. H4-14, Montreal, QC, Canada H3A 1A1.
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Bijveld MMC, Riemslag FCC, Kappers AML, Hoeben FP, van Genderen MM. An extended 15 Hz ERG protocol (2): data of normal subjects and patients with achromatopsia, CSNB1, and CSNB2. Doc Ophthalmol 2011; 123:161-72. [PMID: 21947599 DOI: 10.1007/s10633-011-9293-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 09/12/2011] [Indexed: 10/17/2022]
Abstract
The amplitude versus flash strength curve of 15 Hz electroretinograms (ERGs) shows two minima. The minima are caused by interactions between the primary and the secondary rod pathways (first minimum), and the secondary rod pathway and the cone-driven pathway (second minimum). Furthermore, cone pathway contributions cause higher-order harmonics to occur in the responses. We measured 15 Hz ERGs in 20 healthy subjects to determine normal ranges and in patients to verify our hypotheses on the contributions of the different pathways and to investigate the clinical application. We analyzed the amplitudes and phases of the 15, 30, and 45 Hz components in the ERGs. The overall shape of the 15 Hz amplitude curves was similar in all normal subjects and showed two minima. The 30 and 45 Hz amplitude curves increased for stimuli of high flash strengths indicating cone pathway contributions. The 15 Hz amplitude curve of the responses of an achromat was similar to that of the normal subjects for low flash strengths and showed a minimum, indicating normal primary and secondary rod pathway function. There was no second minimum, and there were no higher-order harmonics, consistent with absent cone pathway function. The 15 Hz ERGs in CSNB1 and CSNB2 patients were similar and of low amplitude for flash strengths just above where the first minimum normally occurs. We could determine that in the CSNB1 patients, the responses originate from the cone pathway, while in the CSNB2 patients, the responses originate from the secondary rod pathway.
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Affiliation(s)
- Mieke M C Bijveld
- Bartiméus, Institute for the Visually Impaired, PO Box 1300, 3700 BA, Zeist, The Netherlands.
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Dark light, rod saturation, and the absolute and incremental sensitivity of mouse cone vision. J Neurosci 2010; 30:12495-507. [PMID: 20844144 DOI: 10.1523/jneurosci.2186-10.2010] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Visual thresholds of mice for the detection of small, brief targets were measured with a novel behavioral methodology in the dark and in the presence of adapting lights spanning ∼8 log(10) units of intensity. To help dissect the contributions of rod and cone pathways, both wild-type mice and mice lacking rod (Gnat1(-/-)) or cone (Gnat2(cpfl3)) function were studied. Overall, the visual sensitivity of mice was found to be remarkably similar to that of the human peripheral retina. Rod absolute threshold corresponded to 12-15 isomerized pigment molecules (R*) in image fields of 800 to 3000 rods. Rod "dark light" (intrinsic retinal noise in darkness) corresponded to that estimated previously from single-cell recordings, 0.012 R* s(-1) rod(-1), indicating that spontaneous thermal isomerizations are responsible. Psychophysical rod saturation was measured for the first time in a nonhuman species and found to be very similar to that of the human rod monochromat. Cone threshold corresponded to ∼5 R* cone(-1) in an image field of 280 cones. Cone dark light was equivalent to ∼5000 R* s(-1) cone(-1), consistent with primate single-cell data but 100-fold higher than predicted by recent measurements of the rate of thermal isomerization of mouse cone opsins, indicating that nonopsin sources of noise determine cone threshold. The new, fully automated behavioral method is based on the ability of mice to learn to interrupt spontaneous wheel running on the presentation of a visual cue and provides an efficient and highly reliable means of examining visual function in naturally behaving normal and mutant mice.
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11
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Michaelides M, Johnson S, Simunovic MP, Bradshaw K, Holder G, Mollon JD, Moore AT, Hunt DM. Blue cone monochromatism: a phenotype and genotype assessment with evidence of progressive loss of cone function in older individuals. Eye (Lond) 2005; 19:2-10. [PMID: 15094734 DOI: 10.1038/sj.eye.6701391] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
AIM To perform a detailed clinical and psychophysical assessment of the members of three British families affected with blue cone monochromatism (BCM), and to determine the molecular basis of disease in these families. METHODS Affected and unaffected members of three families with BCM were examined clinically and underwent electrophysiological and detailed psychophysical testing. Blood samples were taken for DNA extraction. The strategy for molecular analysis was to amplify the coding regions of the long wavelength-sensitive (L) and middle wavelength-sensitive (M) cone opsin genes and the upstream locus control region by polymerase chain reaction, and to examine these fragments for mutations by direct sequencing. RESULTS We have confirmed the reported finding of protan-like D-15 arrangements of patients with BCM. In addition, we have demonstrated that the Mollon-Reffin (MR) Minimal test is a useful colour-discrimination test to aid in the diagnosis of BCM. Affected males were shown to fail the protan and deutan axes, but retained good discrimination on the tritan axis of the MR test, a compelling evidence for residual colour vision in BCM. This residual tritan discrimination was also readily detected with HRR plates. In two families, psychophysical testing demonstrated evidence for progression of disease. In two pedigrees, BCM could be linked to unequal crossovers within the opsin gene array that resulted in a single 5'-L/M-3' hybrid gene, with an inactivating Cys203Arg mutation. The causative mutations were not identified in the third family. CONCLUSIONS The MR test is a useful method of detecting BCM across a wide range of age groups; residual tritan colour discrimination is clearly demonstrated and allows BCM to be distinguished from rod monochromatism. BCM is usually classified as a stationary cone dysfunction syndrome; however, two of our families show evidence of progression. This is the first report of progression associated with a genotype consisting of a single 5'-L/M-3' hybrid gene carrying an inactivating mutation. We have confirmed that the Cys203Arg inactivating mutation is a common sequence change in blue cone monochromats.
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Affiliation(s)
- M Michaelides
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
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12
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Abstract
The normal X-chromosome-linked color-vision gene array is composed of a single long-wave-sensitive (L-) pigment gene followed by one or more middle-wave-sensitive (M-) pigment genes. The expression of these genes to form L- or M-cones is controlled by the proximal promoter and by the locus control region. The high degree of homology between the L- and M-pigment genes predisposed them to unequal recombination, leading to gene deletion or the formation of L/M hybrid genes that explain the majority of the common red-green color-vision deficiencies. Hybrid genes encode a variety of L-like or M-like pigments. Analysis of the gene order in arrays of normal and deutan subjects indicates that only the two most proximal genes of the array contribute to the color-vision phenotype. This is supported by the observation that only the first two genes of the array are expressed in the human retina. The severity of the color-vision defect is roughly related to the difference in absorption maxima (lambda(max)) between the photopigments encoded by the first two genes of the array. A single amino acid polymorphism (Ser180Ala) in the L pigment accounts for the subtle difference in normal color vision and influences the severity of red-green color-vision deficiency. Blue-cone monochromacy is a rare disorder that involves absence of L- and M-cone function. It is caused either by deletion of a critical region that regulates expression of the L/M gene array, or by mutations that inactivate the L- and M-pigment genes. Total color blindness is another rare disease that involves complete absence of all cone function. A number of mutants in the genes encoding the cone-specific alpha- and beta-subunits of the cGMP-gated cation channel as well as in the alpha-subunit of transducin have been implicated in this disorder.
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Affiliation(s)
- Samir S Deeb
- Department of Medicine, University of Washington, Seattle, USA.
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13
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Crognale MA, Fry M, Highsmith J, Haegerstrom-Portnoy G, Neitz M, Neitz J, Webster MA. Characterization of a novel form of X-linked incomplete achromatopsia. Vis Neurosci 2005; 21:197-203. [PMID: 15518189 DOI: 10.1017/s0952523804213384] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
X-linked incomplete achromatopsia (XIA), also called blue-cone monochromacy (BCM), is a rare cone disorder that most commonly results either from one of two conditions. The first condition is a deletion of the locus control region (LCR) which is a critical DNA element that lies upstream of the L and M photopigment gene array on the X-chromosome and is necessary for expression of the photopigment genes. The second condition is an inactivating point mutation within the coding sequence of the remaining photopigment gene in an array from which all but one gene has been deleted. Many previous studies have concluded that affected individuals either have only rods and S-cones (Blackwell & Blackwell, 1957, 1961; Daw & Enoch, 1973; Hess et al., 1989) or have rods, S-cones, and another cone type that contains the rod pigment (Pokorny et al., 1970; Alpern et al., 1971). However, Smith et al. (1983) described individuals with XIA who had residual L-cone function. Here we report results for a subject with XIA who appears to have residual M-cone function. Genetic analysis revealed that he had apparently normal genes for M-cone photopigment thus leaving open the possibility that he has a contribution to vision based on expression of these genes at a very low level.
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14
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Morland AB, Baseler HA, Hoffmann MB, Sharpe LT, Wandell BA. Abnormal retinotopic representations in human visual cortex revealed by fMRI. Acta Psychol (Amst) 2001; 107:229-47. [PMID: 11388137 DOI: 10.1016/s0001-6918(01)00025-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The representation of the visual field in early visual areas is retinotopic. The point-to-point relationship on the retina is therefore maintained on the convoluted cortical surface. Functional magnetic resonance imaging (fMRI) has been able to demonstrate the retinotopic representation of the visual field in occipital cortex of normal subjects. Furthermore, visual areas that are retinotopic can be identified on computationally flattened cortical maps on the basis of positions of the vertical and horizontal meridians. Here, we investigate abnormal retinotopic representations in human visual cortex with fMRI. We present three case studies in which patients with visual disorders are investigated. We have tested a subject who only possesses operating rod photoreceptors. We find in this case that the cortex undergoes a remapping whereby regions that would normally represent central field locations now map more peripheral positions in the visual field: In a human albino we also find abnormal visual cortical activity. Monocular stimulation of each hemifield resulted in activations in the hemisphere contralateral to the stimulated eye. This is consistent with abnormal decussation at the optic chiasm in albinism. Finally, we report a case where a lesion to white matter has resulted in a lack of measurable activity in occipital cortex. The activity was absent for a small region of the visual field, which was found to correspond to the subject's field defect. The cases selected have been chosen to demonstrate the power of fMRI in identifying abnormalities in the cortical representations of the visual field in patients with visual dysfunction. Furthermore, the experiments are able to show how the cortex is capable of modifying the visual field representation in response to abnormal input.
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Affiliation(s)
- A B Morland
- Psychology Department, University of London, Royal Holloway, Egham, Surrey TW20 0EX, UK
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15
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Wandell BA, Poirson AB, Newsome WT, Baseler HA, Boynton GM, Huk A, Gandhi S, Sharpe LT. Color signals in human motion-selective cortex. Neuron 1999; 24:901-9. [PMID: 10624953 DOI: 10.1016/s0896-6273(00)81037-5] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The neural basis for the effects of color and contrast on perceived speed was examined using functional magnetic resonance imaging (fMRI). Responses to S cone (blue-yellow) and L + M cone (luminance) patterns were measured in area V1 and in the motion area MT+. The MT+ responses were quantitatively similar to perceptual speed judgments of color patterns but not to color detection measures. We also measured cortical motion responses in individuals lacking L and M cone function (S cone monochromats). The S cone monochromats have clear motion-responsive regions in the conventional MT+ position, and their contrast-response functions there have twice the responsivity of S cone contrast-response functions in normal controls. But, their responsivity is far lower than the normals' responsivity to luminance contrast. Thus, the powerful magnocellular input to MT+ is either weak or silent during photopic vision in S cone monochromats.
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Affiliation(s)
- B A Wandell
- Department of Psychology, Stanford University, California 94305, USA.
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16
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Stockman A, Sharpe LT, Fach C. The spectral sensitivity of the human short-wavelength sensitive cones derived from thresholds and color matches. Vision Res 1999; 39:2901-27. [PMID: 10492818 DOI: 10.1016/s0042-6989(98)00225-9] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used two methods to estimate short-wave (S) cone spectral sensitivity. Firstly, we measured S-cone thresholds centrally and peripherally in five trichromats, and in three blue-cone monochromats, who lack functioning middle-wave (M) and long-wave (L) cones. Secondly, we analyzed standard color-matching data. Both methods yielded equivalent results, on the basis of which we propose new S-cone spectral sensitivity functions. At short and middle-wavelengths, our measurements are consistent with the color matching data of Stiles and Burch (1955, Optica Acta, 2, 168-181; 1959, Optica Acta, 6, 1-26), and other psychophysically measured functions, such as pi 3 (Stiles, 1953, Coloquio sobre problemas opticos de la vision, 1, 65-103). At longer wavelengths, S-cone sensitivity has previously been over-estimated.
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Affiliation(s)
- A Stockman
- Department of Psychology, University of California San Diego, La Jolla 92093-0109, USA.
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17
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Abstract
The cone dystrophies are a heterogeneous group of inherited disorders that result in dysfunction of the cone photoreceptors and sometimes their post-receptoral pathways. The major clinical features of cone dystrophy are photophobia, reduced visual acuity and abnormal colour vision. Ganzfeld electroretinography shows reduced or absent cone responses. On the basis of their natural history, the cone dystrophies may be broadly divided into two groups: stationary and progressive cone dystrophies. The stationary cone dystrophies have received more attention, and subsequently our knowledge of their molecular genetic, psychophysical and clinical characteristics is better developed. Various methods of classification have been proposed for the progressive cone dystrophies, but none is entirely satisfactory, largely because the underlying disease mechanisms are poorly understood. Multidisciplinary studies involving clinical assessment, molecular genetics, electrophysiology and psychophysics should lead to an improved understanding of the pathogenesis of these disorders.
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Affiliation(s)
- M P Simunovic
- Department of Experimental Psychology, University of Cambridge, UK
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18
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Starace DM, Knox BE. Activation of transducin by a Xenopus short wavelength visual pigment. J Biol Chem 1997; 272:1095-100. [PMID: 8995408 DOI: 10.1074/jbc.272.2.1095] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Phototransduction in cones differs significantly from that in rods in sensitivity, kinetics, and recovery following exposure to light. The contribution that the visual pigment makes in determining the cone response was investigated biochemically by expressing a Xenopus violet cone opsin (VCOP) cDNA in COS1 cells and assaying the light-dependent activation of transducin. Light-exposed VCOP stimulated [35S]guanosine 5'-(gamma-thio)triphosphate nucleotide exchange on bovine rod transducin in a time-dependent manner with a half-time for activation of 0.75 min, similar to that of bovine rhodopsin. In exhaustive binding assays, VCOP and rhodopsin activity showed similar concentration dependence with half-maximal activation occurring at 0.02 mol of pigment/mol of transducin. Although VCOP was able to activate as many as 12 transducins per photoisomerization, rhodopsin catalyzed significantly more. When assays were performed with lambda > 420 nm illumination, VCOP exhibited rapid regeneration and high affinity for the photoregenerated 11-cis-retinal. Recycling of the chromophore and reactivation of the pigment resulted in multiple activations of transducin, whereas a maximum of 1 transducin per VCOP was activated under brief illumination. The decay of the active species formed following photobleaching was complete in <5 min, approximately 10-fold faster than that of rhodopsin. In vitro, VCOP activated rod transducin with kinetics and affinity similar to those of rhodopsin, but the active conformation decayed more rapidly and the apoprotein regenerated more efficiently with VCOP than with rhodopsin. These properties of the violet pigment may account for much of the difference in response kinetics between rods and cones.
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Affiliation(s)
- D M Starace
- Department of Biochemistry and Molecular Biology, State University of New York Health Science Center, Syracuse 13210, USA
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19
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Rosenfeld PJ, McKusick VA, Amberger JS, Dryja TP. Recent advances in the gene map of inherited eye disorders: primary hereditary diseases of the retina, choroid, and vitreous. J Med Genet 1994; 31:903-15. [PMID: 7891370 PMCID: PMC1016688 DOI: 10.1136/jmg.31.12.903] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- P J Rosenfeld
- Howe Laboratory, Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston 02114
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20
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Nathans J, Maumenee IH, Zrenner E, Sadowski B, Sharpe LT, Lewis RA, Hansen E, Rosenberg T, Schwartz M, Heckenlively JR. Genetic heterogeneity among blue-cone monochromats. Am J Hum Genet 1993; 53:987-1000. [PMID: 8213841 PMCID: PMC1682301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Thirty-three unrelated subjects with blue-cone monochromacy or closely related variants of blue-cone monochromacy were examined for rearrangements in the tandem array of genes encoding the red- and green-cone pigments. In 24 subjects, eight genotypes were found that would be predicted to eliminate the function of all of the genes within the array. As observed in an earlier study, the rearrangements involve either deletion of a locus control region adjacent to the gene array or loss of function via homologous recombination and point mutation. One inactivating mutation, Cys203-to-Arg, was found in 15 probands who carry single genes and in both visual pigment genes in one subject whose array has two genes. This mutation was also found in at least one of the visual pigment genes in 1 subject whose array has multiple genes and in 2 of 321 control subjects, suggesting that preexisting Cys203-to-Arg mutations constitute a reservoir of chromosomes that are predisposed to generate blue-cone-monochromat genotypes by unequal homologous recombination and/or gene conversion. Two other point mutations were identified: (a) Arg247-to-Ter in one subject with a single red-pigment gene and (b) Pro307-to-Leu in one subject with a single 5' red-3' green hybrid gene. The observed heterogeneity of genotypes points to the existence of multiple one- and two-step mutational pathways to blue-cone monochromacy.
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Affiliation(s)
- J Nathans
- Howard Hughes Medical Institute, Department of Molecular Biology, Baltimore, MD
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21
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Abstract
1. An oft-cited view, derived principally from the writings of Gordon L. Walls, is that relatively few mammalian species have a capacity for colour vision. This review has evaluated that proposition in the light of recent research on colour vision and its mechanisms in mammals. 2. To yield colour vision a retina must contain two or more spectrally discrete types of photopigment. While this is a necessary condition, it is not a sufficient one. This means, in particular, that inferences about the presence of colour vision drawn from studies of photopigments, the precursors of photopigments, or from nervous system signals must be accepted with due caution. 3. Conjoint signals from rods and cones may be exploited by mammalian nervous systems to yield behavioural discriminations consistent with the formal definition of colour vision. Many mammalian retinas are relatively cone-poor, and thus there are abundant opportunities for such rod/cone interactions. Several instances were cited in which animals having (apparently) only one type of cone photopigment succeed at colour discriminations using such a mechanism. it is suggested that the exploitation of such a mechanism may not be uncommon among mammals. 4. Based on ideas drawn from natural history, Walls (1942) proposed that the receptors and photopigments necessary to support colour vision were lost during the nocturnal phase of mammalian history and then re-acquired during the subsequent mammalian radiations. Contemporary examination of photopigment genes along with the utilization of better techniques for identifying rods and cones suggest a different view, that the earliest mammals had retinas containing some cones and two types of cone photopigment. Thus the baseline mammalian colour vision is argued to be dichromacy. 5. A consideration of the broad range of mammalian niches and activity cycles suggests that many mammals are active during photic periods that would make a colour vision capacity potentially useful. 6. A systematic survey was presented that summarized the evidence for colour vision in mammals. Indications of the presence and nature of colour vision were drawn both from direct studies of colour vision and from studies of those retinal mechanisms that are most closely associated with the possession of colour vision. Information about colour vision can be adduced for species drawn from nine mammalian orders.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- G H Jacobs
- Department of Psychology, University of California, Santa Barbara 93106
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22
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23
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24
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Abstract
1. Incremental thresholds were measured in a retinal region 12 deg temporal from the fovea with a target of 200 ms in duration and 6 deg in diameter superimposed on background fields of various intensities and wavelengths. Measurements were made under rod-isolation conditions in five normal observers and in a typical, complete achromat observer who had no cone function. 2. The rise in threshold with background intensity changes with background wavelength in the normal trichromat observers. On 450, 520 and 560 nm backgrounds the average slope in logarithmic co-ordinates (0.78 +/- 0.04, S.D.) is similar to that found for the achromat--whose slope is independent of background wavelength (0.79 +/- 0.03)--but on a 640 nm background it more nearly approaches Weber's law (0.91 +/- 0.02). This indicates that the sensitivity of the rods to an incremental target is not determined by quantal absorptions in the rods alone but by quantal absorptions in both the rods and the cones. 3. Rod incremental thresholds were also measured in various colour-blind observers lacking one or more of the cone classes: a blue-cone monochromat, four deuteranopes and a protanope. For the blue-cone monochromat, like the achromat, the slope of the increment threshold curve is constant with background wavelength. For the deuteranopes and the protanope, like the normal, the slope increases with wavelength. The protanope, however, shows a smaller increase in slope, consistent with the lower sensitivity of his cones to long-wavelength light. 4. The dependence of the field adaptation of the rods on the cones was confirmed by field-mixture experiments, in which the incremental threshold was measured against bichromatic backgrounds, and in silent substitution experiments, in which backgrounds equated for their effects on either the cones or the rods but not both were instantaneously substituted for one another.
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Affiliation(s)
- L T Sharpe
- Neurologische Universitätsklinik, Freiburg im Breisgau, Germany
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25
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Reitner A, Sharpe LT, Zrenner E. Is colour vision possible with only rods and blue-sensitive cones? Nature 1991; 352:798-800. [PMID: 1881435 DOI: 10.1038/352798a0] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
At night all cats are grey, but with the approach of dawn they take on colour. By starlight, a single class of photoreceptors, the rods, function, whereas by daylight, three classes, the blue-, green- and red-sensitive cones, are active and provide colour vision. Only by comparing the rates of quantal absorption in more than one photoreceptor class is colour vision possible. Although the comparisons generally take place between the cones, they can involve the rods as well. Here we investigate the wavelength discrimination of an extremely rare group of individuals, blue-cone monochromats, who have only rods and one class of cones. We find that these individuals can distinguish wavelengths (440 to 500 nm) in the twilight region where the rods and blue-sensitive cones are simultaneously active.
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Affiliation(s)
- A Reitner
- Zweite Universitäts-Augenklinik, Vienna, Austria
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26
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Hess RF, Mullen KT, Zrenner E. Human photopic vision with only short wavelength cones: post-receptoral properties. J Physiol 1989; 417:151-72. [PMID: 2621590 PMCID: PMC1189260 DOI: 10.1113/jphysiol.1989.sp017795] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
1. Spatial and temporal contrast sensitivities were investigated in two subjects whose photopic vision has been previously shown to be subserved by only short wavelength cones. 2. Spatial contrast sensitivity was uniformly reduced compared with that of the normal trichromatic observer. Peak contrast sensitivity reached 40 which is a factor of 2-3 better than previous estimates and extrapolated acuity was around 15 cycles deg-1. Central, non-aliased grating acuity was between 6-9 cycles deg-1. This declined with eccentricity such that at 20 deg it was around 1 cycle deg-1. 3. The variation in contrast sensitivity across the visual field was measured for a range of different spatial frequencies. It was found to be of the same form as that for the normal trichromat but reduced in overall sensitivity. 4. Temporal contrast sensitivity was measured for two different spatial frequencies and found to exhibit the spatio-temporal covariation which is typical of normal trichromatic vision. Temporal acuity exhibited a strong dependence on illuminance and reached asymptotic values of around 40-45 Hz. While this is more than a factor of two above most previous estimates for the short wavelength receptors of normal vision it agrees with some more recent estimates obtained using a different technique. Temporal resolution was found to be evenly distributed across the visual field. 5. Similarities were found between the post-receptoral properties of these achromats and the properties of the isolated blue mechanism of normal vision and also the properties of normal luminance contrast processing in general. The present results provide an upper bound on the contribution of the short wavelength mechanism to normal vision and also provide a suitable model of its possible contribution to the processing of luminance contrast in the normal visual system.
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Affiliation(s)
- R F Hess
- Physiological Laboratory, University of Cambridge
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