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Ather S, Proudlock FA, Welton T, Morgan PS, Sheth V, Gottlob I, Dineen RA. Aberrant visual pathway development in albinism: From retina to cortex. Hum Brain Mapp 2019; 40:777-788. [PMID: 30511784 PMCID: PMC6865554 DOI: 10.1002/hbm.24411] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 09/08/2018] [Accepted: 09/18/2018] [Indexed: 12/27/2022] Open
Abstract
Albinism refers to a group of genetic abnormalities in melanogenesis that are associated neuronal misrouting through the optic chiasm. We perform quantitative assessment of visual pathway structure and function in 23 persons with albinism (PWA) and 20 matched controls using optical coherence tomography (OCT), volumetric magnetic resonance imaging (MRI), diffusion tensor imaging and visual evoked potentials (VEP). PWA had a higher streamline decussation index (percentage of total tractography streamlines decussating at the chiasm) compared with controls (Z = -2.24, p = .025), and streamline decussation index correlated weakly with inter-hemispheric asymmetry measured using VEP (r = .484, p = .042). For PWA, a significant correlation was found between foveal development index and total number of streamlines (r = .662, p < .001). Significant positive correlations were found between peri-papillary retinal nerve fibre layer thickness and optic nerve (r = .642, p < .001) and tract (r = .663, p < .001) width. Occipital pole cortical thickness was 6.88% higher (Z = -4.10, p < .001) in PWA and was related to anterior visual pathway structures including foveal retinal pigment epithelium complex thickness (r = -.579, p = .005), optic disc (r = .478, p = .021) and rim areas (r = .597, p = .003). We were unable to demonstrate a significant relationship between OCT-derived foveal or optic nerve measures and MRI-derived chiasm size or streamline decussation index. Our novel tractographic demonstration of altered chiasmatic decussation in PWA corresponds to VEP measured cortical asymmetry and is consistent with chiasmatic misrouting in albinism. We also demonstrate a significant relationship between retinal pigment epithelium and visual cortex thickness indicating that retinal pigmentation defects in albinism lead to downstream structural reorganisation of the visual cortex.
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Affiliation(s)
- Sarim Ather
- Nuffield Department of Surgical SciencesUniversity of OxfordOxfordUnited Kingdom
| | - Frank Anthony Proudlock
- University of Leicester Ulverscroft Eye UnitRobert Kilpatrick Clinical Sciences BuildingLeicesterUnited Kingdom
| | - Thomas Welton
- Radiological Sciences, Division of Clinical NeuroscienceUniversity of Nottingham, Queen's Medical CentreNottinghamUnited Kingdom
- Sir Peter Mansfield Imaging Centre, University of NottinghamQueen's Medical CentreNottinghamUnited Kingdom
| | - Paul S. Morgan
- Sir Peter Mansfield Imaging Centre, University of NottinghamQueen's Medical CentreNottinghamUnited Kingdom
- Medical Physics and Clinical Engineering, Nottingham University Hospitals NHS TrustQueen's Medical CentreNottinghamUnited Kingdom
| | - Viral Sheth
- University of Leicester Ulverscroft Eye UnitRobert Kilpatrick Clinical Sciences BuildingLeicesterUnited Kingdom
| | - Irene Gottlob
- University of Leicester Ulverscroft Eye UnitRobert Kilpatrick Clinical Sciences BuildingLeicesterUnited Kingdom
| | - Rob A. Dineen
- Radiological Sciences, Division of Clinical NeuroscienceUniversity of Nottingham, Queen's Medical CentreNottinghamUnited Kingdom
- Sir Peter Mansfield Imaging Centre, University of NottinghamQueen's Medical CentreNottinghamUnited Kingdom
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Bhansali P, Rayport I, Rebsam A, Mason C. Delayed neurogenesis leads to altered specification of ventrotemporal retinal ganglion cells in albino mice. Neural Dev 2014; 9:11. [PMID: 24885435 PMCID: PMC4072486 DOI: 10.1186/1749-8104-9-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2014] [Accepted: 04/29/2014] [Indexed: 11/13/2022] Open
Abstract
Background Proper binocular vision depends on the routing at the optic chiasm of the correct proportion of retinal ganglion cell (RGC) axons that project to the same (ipsilateral) and opposite (contralateral) side of the brain. The ipsilateral RGC projection is reduced in mammals with albinism, a congenital disorder characterized by deficient pigmentation in the skin, hair, and eyes. Compared to the pigmented embryonic mouse retina, the albino embryonic mouse retina has fewer RGCs that express the zinc-finger transcription factor, Zic2, which is transiently expressed by RGCs fated to project ipsilaterally. Here, using Zic2 as a marker of ipsilateral RGCs, Islet2 as a marker of contralateral RGCs, and birthdating, we investigate spatiotemporal dynamics of RGC production as they relate to the phenotype of diminished ipsilateral RGC number in the albino retina. Results At embryonic day (E)15.5, fewer Zic2-positive (Zic2+) RGCs are found in the albino ventrotemporal (VT) retina compared with the pigmented VT retina, as we previously reported. However, the reduction in Zic2+ RGCs in the albino is not accompanied by a compensatory increase in Zic2-negative (Zic2−) RGCs, resulting in fewer RGCs in the VT retina at this time point. At E17.5, however, the number of RGCs in the VT region is similar in pigmented and albino retinae, implicating a shift in the timing of RGC production in the albino. Short-term birthdating assays reveal a delay in RGC production in the albino VT retina between E13 and E15. Specifically, fewer Zic2+ RGCs are born at E13 and more Zic2− RGCs are born at E15. Consistent with an increase in the production of Zic2− RGCs born at later ages, more RGCs at E17.5 express the contralateral marker, Islet2, in the albino VT retina compared with the pigmented retina. Conclusions A delay in neurogenesis in the albino retina is linked to the alteration of RGC subtype specification and consequently leads to the reduced ipsilateral projection that characterizes albinism.
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Affiliation(s)
| | | | | | - Carol Mason
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, USA.
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Yeritsyan N, Lehmann K, Puk O, Graw J, Löwel S. Visual capabilities and cortical maps in BALB/c mice. Eur J Neurosci 2012; 36:2801-11. [DOI: 10.1111/j.1460-9568.2012.08195.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Wong Y, Chen S, Seo J, Morley J, Lovell N, Suaning G. Focal activation of the feline retina via a suprachoroidal electrode array. Vision Res 2009; 49:825-33. [DOI: 10.1016/j.visres.2009.02.018] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 02/17/2009] [Accepted: 02/26/2009] [Indexed: 11/25/2022]
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Heiduschka P, Schraermeyer U. Comparison of visual function in pigmented and albino rats by electroretinography and visual evoked potentials. Graefes Arch Clin Exp Ophthalmol 2008; 246:1559-73. [DOI: 10.1007/s00417-008-0895-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 06/10/2008] [Accepted: 06/16/2008] [Indexed: 11/25/2022] Open
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van Genderen MM, Riemslag FCC, Schuil J, Hoeben FP, Stilma JS, Meire FM. Chiasmal misrouting and foveal hypoplasia without albinism. Br J Ophthalmol 2006; 90:1098-102. [PMID: 16707527 PMCID: PMC1857410 DOI: 10.1136/bjo.2006.091702] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND/AIMS To present the ophthalmological and electrophysiological characteristics of three darkly pigmented, female patients with misrouting and foveal hypoplasia. One of the patients had primary ciliary dyskinesia and situs inversus totalis (Kartagener syndrome). METHODS Fundus photographs were taken and the angles at which the main temporal arterial branches leave the optic nerve head (ONH) were analysed. Optical coherence tomography (OCT) was performed through the presumed foveal region. Pattern onset visually evoked potentials (VEPs) (check sizes 60', 40/400 ms) were recorded and the chiasmal coefficient was calculated to detect misrouting. RESULTS Fundus photography showed normally pigmented fundi with absence of the usual foveal hyperpigmentation, foveal avascular zone, and macular and foveal reflexes. On OCT no foveal pit was found. The VEP recordings showed the largest positive CI component over the right hemisphere for the left eye, and over the left hemisphere for the right eye, with the CI almost absent over the ipsilateral hemispheres. The differential derivations showed opposite polarity for the recordings of the two eyes. The chiasmal coefficients of all three patients were significantly indicative of misrouting (-0.99, -0.91, and -0.99, respectively). CONCLUSION Based on the investigations in these patients the authors propose the hypothesis that foveal hypoplasia and misrouting exist as a distinct entity, and do not comprise the exclusive hallmark of albinism. The findings suggest that misrouting may exert a retrograde influence on foveal development.
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Affiliation(s)
- M M van Genderen
- Bartiméus Institute for the Visually Impaired, PO Box 1003, 3700 BA Zeist, Netherlands.
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Neveu MM, Holder GE, Sloper JJ, Jeffery G. Optic chiasm formation in humans is independent of foveal development. Eur J Neurosci 2006; 22:1825-9. [PMID: 16197526 DOI: 10.1111/j.1460-9568.2005.04364.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A failure of human foveal development only occurs in two genetically determined conditions; aniridia (Pax6 mutation) and albinism (tyrosinase mutation). The chiasmatic pathways from this region are disrupted in albinism and central retinal blood vessel patterns are abnormal. It is assumed that these three abnormalities have a common mechanism. Here we investigate whether similar abnormalities are present in subjects with aniridia. Using fundus photographs it is shown that abnormal blood vessel patterns are present in aniridia, but these significantly differ from those in albinos. Using electrophysiological techniques, abnormal hemispheric projections through the chiasm are demonstrated in albinos, but aniridics do not differ from normal subjects. These results demonstrate that although mutations in Pax6 and tyrosinase both affect central retinal development, they have a fundamentally different impact on the formation of the retinal vasculature and the projections from this region. This strongly suggests that separate mechanisms regulate the development of the central retina and decussation patterns at the optic chiasm.
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Affiliation(s)
- Magella M Neveu
- Institute of Ophthalmology, University College London, Bath Street, London EC1V 9EL, UK
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Baker GE, Dovey M, Davda P, Guibal C, Jeffery G. Protein kinase C immunoreactivity in the pigmented and albino rat retina. Eur J Neurosci 2006; 22:2481-8. [PMID: 16307591 DOI: 10.1111/j.1460-9568.2005.04453.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The albino retina is abnormal. The central region is under-developed and some cell populations are reduced or increased in number. Not least of these anomalies is the deficit in the rod population in hypopigmented rodents and carnivores. Given this abnormality we have examined the distribution of rod bipolar cells in albino rats to determine whether this subsequent stage in the rod pathway is similarly disrupted. A monoclonal antibody to protein kinase C was used to determine the distribution of rod bipolar cells in juvenile and adult pigmented and albino rats. Immunoreactive rod bipolar cells and their processes were counted in transverse sections passing through both the central and peripheral retina. The mean densities of immunoreactive cells were significantly reduced in albino retinas at both juvenile (postnatal day 15) and adult stages, in the former by 14% and the latter by 9%. This was evident across the entire central-to-peripheral extent of the retina. The reduced rod photoreceptor population found in albinos appears therefore to be consequential for the magnitude of their major target population, rod bipolar cells. The decrease in the rod bipolar population indicates a change in retinal cytoarchitecture and implies a disruption of functional organization of the albino retina, especially that underlying the scotopic channel. This, coupled with observations that some other retinal interneuronal populations may be disrupted, implies disordered retinal processing in albinos and emphasizes the likelihood that abnormal visual function in albinos may be as much a result of anomalous retinal circuitry as of the known photoreceptor deficit or chiasmatic misrouting.
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Affiliation(s)
- Gary E Baker
- Department of Optometry & Visual Science, City University, Northampton Square, London EC1V 0HB, UK.
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Giménez E, Lavado A, Jeffery G, Montoliu L. Regional abnormalities in retinal development are associated with local ocular hypopigmentation. J Comp Neurol 2005; 485:338-47. [PMID: 15803509 DOI: 10.1002/cne.20495] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The retinal pigment epithelium (RPE) plays a key role in regulating retinal development. The critical enzyme in pigment production is tyrosinase. Transgenic mice with a tyrosinase construct where the locus control region was deleted (YRT4) display a variegated phenotype of tyrosinase expression. Their central retina is largely pigment free, whereas more peripheral regions are heavily pigmented. We have used this model to ask whether the influence of pigmented RPE over the retina during development is fundamentally governed by local interactions or is global. Our data show that YRT4 eyes have intermediate melanin content and relatively low tyrosinase activity compared with wild-type and albino animals. Rod counts are comparable to those in pigmented mice in peripheral regions but similar to those in albinos centrally. Anterograde labelling of retinal pathways demonstrates the presence of relatively normal ipsilateral chiasmatic projection in YRT4 mice, comparable with that in pigmented animals and consistent with the peripheral pigmented origin of this pathway. Examination of cellular proliferation levels during retinal development reveals that YRT4 mice display an extended period of mitosis, similar to that found in albinos. Hence, our results show that the regulatory influence of the RPE over the developing retina depends on localized interactions between these tissues.
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Affiliation(s)
- Estela Giménez
- Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología, Campus de Cantoblanco, C/Darwin 3, 28049 Madrid, Spain
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Barmashenko G, Schmidt M, Hoffmann KP. Differences between cation-chloride co-transporter functions in the visual cortex of pigmented and albino rats. Eur J Neurosci 2005; 21:1189-95. [PMID: 15813928 DOI: 10.1111/j.1460-9568.2005.03948.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Albinism in mammals is accompanied by specific morphological and functional alterations of the visual system. To understand their cellular basis we studied the physiological characteristics and transmembrane currents of pyramidal neurons in 350-microm-thick slices of visual cortex from pigmented and albino rats using whole-cell and gramicidin perforated patch-clamp recordings. The resting membrane potential was significantly more positive and the rheobase was significantly lower in neurons of layers II/III and V in albinos as compared with pigmented rats. No significant differences were found in the input resistance, time constant and chronaxy. Whereas the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated currents were not significantly different, the maximum gamma-aminobutyric acid (GABA)(A) receptor (GABA(A)R)-mediated currents and miniature inhibitory postsynaptic currents showed significantly lower amplitudes in neurons of layer V in visual cortex of albinos as compared with pigmented rats. The reversal potential of the GABA(A)R-mediated currents (E(GABA)) was significantly shifted to more positive values in albinos. Pharmacological experiments showed that this shift could be caused by an increased action of the inward chloride co-transporter NKCC1 and reduced action of the outward chloride co-transporter KCC2 in albino rats. This difference seems to be restricted to the visual cortex because in pyramidal neurons from frontal cortex E(GABA) was not significantly different in albinos as compared with pigmented rats. These results are discussed in relation to functional alterations in the albino visual system.
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Affiliation(s)
- Gleb Barmashenko
- General Zoology & Neurobiology, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany.
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Abstract
Occulocutaneous albinism is caused by mutations in the gene encoding the enzyme tyrosinase. Individuals with this disorder are predisposed to visual system deficits. We determined the critical period during development when tyrosinase expression is essential for the appropriate pathfinding of ganglion cell axons from the retina to the dorsal lateral geniculate nucleus. We used a line of mice with a Tyrosinase transgene, the expression of which is regulatable with the lac operator-repressor system, to restrict tyrosinase activity to discrete periods of embryogenesis. When tyrosinase was expressed throughout the period of neuroblast divisions that produce the ipsilaterally projecting ganglion cells, axonal projections innervated the same volume of the ipsilateral dorsal lateral geniculate nucleus of the thalamus as in normal mice. If tyrosinase expression ceased before the end of neuroblast divisions, or was not initiated until after they had begun, the degree of ipsilateral innervation was smaller, as in albino mice. Tyrosinase expression was not required during the entire period of pathfinding itself or during final maturation of the retinogeniculate pathway. Thus, tyrosinase appears to set up a signal early in visual system development that determines the pathway taken later by ganglion cell axons.
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Grant S, Binns KE. Reduced influence of the ipsilateral ear on spatial tuning of auditory neurons in the albino superior colliculus: a knock-on effect of anomalies of the acoustic chiasm? Exp Brain Res 2003; 151:478-88. [PMID: 12830342 DOI: 10.1007/s00221-003-1495-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2002] [Accepted: 04/10/2003] [Indexed: 10/26/2022]
Abstract
Auditory brainstem abnormalities affecting decussation patterns and nuclei involved in the acoustic chiasm exist in a variety of albino mammals, suggesting that binaural processes underlying spatial hearing may be disrupted in these mutants. To evaluate this we have compared the contribution of the two ears in albino and normally pigmented guinea pigs to the spatial tuning of auditory neurons in the deep layers of the superior colliculus (SC). Broadband noise stimuli at threshold and at suprathreshold intensities were presented from different azimuthal loudspeaker locations under free-field anechoic conditions, and auditory receptive fields were plotted before, during and after occluding the ipsilateral ear. We show that the deep layers of the albino SC contain a map of contralateral auditory azimuth along its anteroposterior axis, which is aligned with the visual map in the superficial layers above, just as in normal animals. We also show that threshold spatial responses are elicited only via the contralateral ear and at similar stimulus intensities (mean approximately 30 dB SPL) in the two pigmentation phenotypes. The mechanisms that maintain spatial tuning at sound intensities of 10-40 dB above threshold, however, differ markedly in these animals. Plugging the ipsilateral ear in normal guinea pigs caused significant expansions of their auditory receptive fields and loss of directional tuning, but in the albinos occlusion had little effect on these spatial properties. The results suggest that while spatial selectivity for relatively loud sounds among SC neurons is normally maintained via the binaural combination of contralateral excitatory drive and ipsilateral inhibition, it is achieved in albinos almost exclusively by monaural input from the contralateral ear. This finding is consistent with an excessive contralateral ear dominance of higher levels of the albino auditory system caused by anomalies of their acoustic chiasm, analogous to the monocular dominance of the visual system that results from excessive axon crossing at the optic chiasm in these animals.
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Affiliation(s)
- Simon Grant
- Division of Neurophysiology, National Institute for Medical Research, Mill Hill, NW7 1AA, London, UK.
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Abstract
The extent of the horizontal visual field was determined behaviourally in 4 pigmented and 5 albino ferrets (Mustela putorius furo, Carnivora, Mammalia) using perimetry. During binocular vision, all pigmented and three albino ferrets responded equally well to stimuli presented anywhere along the horizontal perimeter in the central 180 degrees of the visual field. The remaining two albinos had a visual field defect in the right hemifield (>30 degrees eccentricity). During monocular vision, a significant difference between the visual fields of pigmented and albino ferrets became apparent. In pigmented ferrets, the visual field of each eye included the ipsilateral (temporal) and a substantial portion of the contralateral (nasal) hemifield. In albinos, the visual field of each eye was limited to the ipsilateral hemifield and reactions to visual stimuli abruptly declined directly beyond the vertical meridian.
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Affiliation(s)
- N Garipis
- Allgemeine Zoologie and Neurobiologie, Ruhr-Universität Bochum, Postfach 102148, D-44780, Bochum, Germany
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