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Pawar PR, Booth J, Neely A, McIlwaine G, Lueck CJ. Nerve fibre organisation in the human optic nerve and chiasm: what do we really know? Eye (Lond) 2024; 38:2457-2471. [PMID: 38849598 PMCID: PMC11306597 DOI: 10.1038/s41433-024-03137-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 04/30/2024] [Accepted: 05/07/2024] [Indexed: 06/09/2024] Open
Abstract
A recent anatomical study of the human optic chiasm cast doubt on the widespread assumption that nerve fibres travelling in the human optic nerve and chiasm are arranged retinotopically. Accordingly, a scoping literature review was performed to determine what is known about the nerve fibre arrangement in these structures. Meta-analysis suggested that the average number of fibres in each optic nerve was 1.023 million with an inter-individual range of approximately 50% of the mean. Loss of nerve fibres with age (approximately 3,400 fibres/year) could not account for this variability. The review suggested that there might be a retinotopic arrangement of nerve fibres in the orbital portion of the optic nerve but that this arrangement is most likely to be lost posteriorly with a more random distribution of nerve fibres at the chiasm. Limited studies have looked at nerve fibre arrangement in the chiasm. In summary, the chiasm is more 'H-shaped' than 'X-shaped': nerve fibre crossings occur paracentrally with nerves in the centre of the chiasm travelling coronally and in parallel. There is interaction between crossed and uncrossed fibres which are widely distributed. The review supports the non-existence of Wilbrand's knee. Considerable further work is required to provide more precise anatomical information, but this review suggests that the assumed preservation of retinotopy in the human optic nerve and chiasm is probably not correct.
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Affiliation(s)
- Pratap R Pawar
- School of Engineering and Technology, University of New South Wales, Canberra, NSW, Australia
| | - Joshua Booth
- School of Medicine and Psychology, Australian National University, Canberra, NSW, Australia
| | - Andrew Neely
- School of Engineering and Technology, University of New South Wales, Canberra, NSW, Australia
| | - Gawn McIlwaine
- Department of Ophthalmology, Mater Hospital, Belfast, Northern, Ireland
| | - Christian J Lueck
- School of Medicine and Psychology, Australian National University, Canberra, NSW, Australia.
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2
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Rajendran R, Arunachalam JP, Chidambaram S, Krishnagopal S, Krishnamurthy B, Vinayagam S, Veeravarmal V, Prasad H, Verma K, U R A. Protein Drug Delivery Using a Novel Maxillofacial Technique Targeting the Visual Pathway in the Brain, the Optic Nerve, and the Retina. ACS Chem Neurosci 2023; 14:3368-3384. [PMID: 37665674 DOI: 10.1021/acschemneuro.3c00184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2023] Open
Abstract
Protein drugs are used for treating many diseases of the eye and the brain. The formidable blood neural barriers prevent the delivery of these drugs into the eye and the brain. Hence, there is a need for a protein drug delivery system to deliver large proteins across blood-neural barriers. Low half-life, poor penetration of epithelial barriers, low stability, and immunogenicity limit the use of non-invasive systemic routes for delivering proteins. In this pre-clinical study, the efficacy of a new maxillofacial route for administering protein drugs using a novel drug delivery system is compared with systemic administration through intra-peritoneal injection and ocular administration through topical eye drops and subconjunctival and intravitreal injections. Bevacizumab and retinoschisin proteins were administered using the maxillofacial technique along with systemic and ocular routes in wild-type male C57BL/6J mice. Liquid chromatography with tandem mass spectrometry and western blot was used to detect bevacizumab in tissue samples. Furthermore, immunohistochemistry was performed to detect the presence and localization of bevacizumab and retinoschisin in the retina and brain. The maxillofacial route of delivery could target the brain including regions involved in the visual pathway and optic nerve. The maxillofacial technique and intravitreal injection were effective in delivering the drugs into the retina. A new concept based on the glymphatic pathway, cerebrospinal fluid drug distribution, and the crossover of ipsilateral optic nerve fibers at optic chiasma is proposed to explain the presence of the drug in contralateral eye following maxillofacial administration and intravitreal injection.
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Affiliation(s)
- Rahini Rajendran
- Central Inter-Disciplinary Research Facility, Sri Balaji Vidyapeeth [Deemed to be University], SBV-Mahatma Gandhi Medical College & Research Institute Campus, Puducherry 607402, India
| | - Jayamuruga Pandian Arunachalam
- Central Inter-Disciplinary Research Facility, Sri Balaji Vidyapeeth [Deemed to be University], SBV-Mahatma Gandhi Medical College & Research Institute Campus, Puducherry 607402, India
| | - Subbulakshmi Chidambaram
- Sensory Neural Engineering and Cell Therapeutics Lab, Department of Biochemistry and Molecular Biology, Pondicherry University, Puducherry 605014, India
| | - Srikanth Krishnagopal
- Department of Ophthalmology, Sri Balaji Vidyapeeth [Deemed to be University], Mahatma Gandhi Medical College & Research Institute, Puducherry 607402, India
| | - Bhavani Krishnamurthy
- Department of Pathology, Sri Balaji Vidyapeeth [Deemed to be University], Mahatma Gandhi Medical College & Research Institute, Puducherry 607402, India
| | - Subha Vinayagam
- Department of Pharmacology, Sri Balaji Vidyapeeth [Deemed to be University], Mahatma Gandhi Medical College & Research Institute, Puducherry 607402, India
| | - Veeran Veeravarmal
- Department of Oral & Maxillofacial Pathology and Oral Microbiology, Government Dental College, Cuddalore, Annamalai Nagar, Chidambaram 608002, Tamil Nadu, India
| | - Harikrishnan Prasad
- Department of Oral Pathology and Microbiology, KSR Institute of Dental Science and Research, Tiruchengode 637215, Tamil Nadu, India
| | - Kavita Verma
- UR Anoop Research Group, Puducherry 605008, India
| | - Anoop U R
- UR Anoop Research Group, Puducherry 605008, India
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3
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Hu T, Meng S, Zhang Q, Song S, Tan C, Huang J, Chen D. Astrocyte derived TSP2 contributes to synaptic alteration and visual dysfunction in retinal ischemia/reperfusion injury. Cell Biosci 2022; 12:196. [PMID: 36471420 PMCID: PMC9720934 DOI: 10.1186/s13578-022-00932-1] [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: 08/31/2022] [Accepted: 11/21/2022] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Despite current intervention measures/therapies are able to ameliorate neuronal death following retinal injuries/diseases, the recovery of visual function remains unsatisfactory. Previous studies revealed that the retinal synapse and neurite changed during the early stage after retinopathy, which was considered to be detrimental to visual signal transmission. However, the specific profiles and the mechanisms underlying retinal neurite and synaptic alteration after retinal pathologies remain poorly understood. METHODS Here, we revealed the spatiotemporal pattern of neurite and synaptic alteration following retinal pathologies using a rat model of acute RI/R induced by high intraocular pressure (HIOP) with Western blotting, Immunofluorescence, and electron microscopy. We further explored the potential role of activated astrocytes and their derived thrombospondin 2 (TSP2) in RI/R induced retinal neurite and synaptic alteration and visual dysfunction through viral transduction and drug injection. RESULTS We found a defasciculation of RGC axons, a compensatory increase of presynaptic proteins (synaptophysin and synapsin 1) and synaptic vesicles between bipolar cells and ganglion cells in the inner plexiform layer (IPL), and the degenerated visual function preceded the neuronal death in rat retinae. These events were accompanied by the activation of astrocytes. Furthermore, we showed that suppressing the activation of astrocytes (intravitreal injection of fluorocitric acid, FC), TSP2 knockdown (TSP2 shRNA-AAV transduction), and competitively inhibiting the binding of TSP2 and α2δ1 (intraperitoneal injection of gabapentin, GBP) effectively alleviated the retinal synaptic and neurite alteration and the visual dysfunction following RI/R injury. CONCLUSIONS (1) At the early stage following RI/R injury, the rat retinae develop a degeneration of ganglion cell axons and the resulting compensatory synaptic remodeling between bipolar cells and ganglion cells in IPL. These changes occur earlier than the massive loss of neurons in the ganglion cell layer (GCL). (2) Activated astrocytes may secret TSP2, which bind to α2δ1, to mediate the degeneration of rat retinal ganglion cell axons, compensatory synaptic remodeling in IPL, and visual dysfunction following RI/R injury.
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Affiliation(s)
- Tu Hu
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, No. 87 Xiangya Road, Changsha, 410008 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan People’s Republic of China
| | - Shuhan Meng
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, No. 87 Xiangya Road, Changsha, 410008 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan People’s Republic of China
| | - Qianyue Zhang
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, No. 87 Xiangya Road, Changsha, 410008 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan People’s Republic of China ,grid.216417.70000 0001 0379 7164Xiangya School of Medicine, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China
| | - Shuang Song
- grid.216417.70000 0001 0379 7164XiangYa School of Public Health, Central South University, No.238 Xiangya Road, Changsha, 410078 Hunan People’s Republic of China
| | - Cheng Tan
- grid.216417.70000 0001 0379 7164Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China
| | - Jufang Huang
- grid.216417.70000 0001 0379 7164Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China
| | - Dan Chen
- grid.216417.70000 0001 0379 7164Department of Anatomy and Neurobiology, School of Basic Medical Science, Central South University, No. 172 Tongzipo Road, Changsha, 410013 Hunan People’s Republic of China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan People’s Republic of China
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The retinal pigmentation pathway in human albinism: Not so black and white. Prog Retin Eye Res 2022; 91:101091. [PMID: 35729001 DOI: 10.1016/j.preteyeres.2022.101091] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 05/24/2022] [Accepted: 05/26/2022] [Indexed: 12/16/2022]
Abstract
Albinism is a pigment disorder affecting eye, skin and/or hair. Patients usually have decreased melanin in affected tissues and suffer from severe visual abnormalities, including foveal hypoplasia and chiasmal misrouting. Combining our data with those of the literature, we propose a single functional genetic retinal signalling pathway that includes all 22 currently known human albinism disease genes. We hypothesise that defects affecting the genesis or function of different intra-cellular organelles, including melanosomes, cause syndromic forms of albinism (Hermansky-Pudlak (HPS) and Chediak-Higashi syndrome (CHS)). We put forward that specific melanosome impairments cause different forms of oculocutaneous albinism (OCA1-8). Further, we incorporate GPR143 that has been implicated in ocular albinism (OA1), characterised by a phenotype limited to the eye. Finally, we include the SLC38A8-associated disorder FHONDA that causes an even more restricted "albinism-related" ocular phenotype with foveal hypoplasia and chiasmal misrouting but without pigmentation defects. We propose the following retinal pigmentation pathway, with increasingly specific genetic and cellular defects causing an increasingly specific ocular phenotype: (HPS1-11/CHS: syndromic forms of albinism)-(OCA1-8: OCA)-(GPR143: OA1)-(SLC38A8: FHONDA). Beyond disease genes involvement, we also evaluate a range of (candidate) regulatory and signalling mechanisms affecting the activity of the pathway in retinal development, retinal pigmentation and albinism. We further suggest that the proposed pigmentation pathway is also involved in other retinal disorders, such as age-related macular degeneration. The hypotheses put forward in this report provide a framework for further systematic studies in albinism and melanin pigmentation disorders.
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5
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Maier A, Cox MA, Westerberg JA, Dougherty K. Binocular Integration in the Primate Primary Visual Cortex. Annu Rev Vis Sci 2022; 8:345-360. [PMID: 35676095 DOI: 10.1146/annurev-vision-100720-112922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
binocular vision, binocular fusion, binocular combination, LGN, V1.
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Affiliation(s)
- A Maier
- Department of Psychological Sciences, Vanderbilt University, Nashville, Tennessee 37240;
| | - M A Cox
- Center for Visual Science, Rochester University, Rochester, New York 14642
| | - J A Westerberg
- Department of Psychological Sciences, Vanderbilt University, Nashville, Tennessee 37240;
| | - K Dougherty
- Neuroscience Institute, Princeton University, Princeton, New Jersey 08544
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6
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Neveu MM, Padhy SK, Ramamurthy S, Takkar B, Jalali S, CP D, Padhi TR, Robson AG. Ophthalmological Manifestations of Oculocutaneous and Ocular Albinism: Current Perspectives. Clin Ophthalmol 2022; 16:1569-1587. [PMID: 35637898 PMCID: PMC9148211 DOI: 10.2147/opth.s329282] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/14/2022] [Indexed: 11/23/2022] Open
Abstract
Albinism describes a heterogeneous group of genetically determined disorders characterized by disrupted synthesis of melanin and a range of developmental ocular abnormalities. The main ocular features common to both oculocutaneous albinism (OCA), and ocular albinism (OA) include reduced visual acuity, refractive errors, foveal hypoplasia, congenital nystagmus, iris and fundus hypopigmentation and visual pathway misrouting, but clinical signs vary and there is phenotypic overlap with other pathologies. This study reviews the prevalence, genetics and ocular manifestations of OCA and OA, including abnormal development of the optic chiasm. The role of visual electrophysiology in the detection of chiasmal dysfunction and visual pathway misrouting is emphasized, highlighting how age-associated changes in visual evoked potential (VEP) test results must be considered to enable accurate diagnosis, and illustrated further by the inclusion of novel VEP data in genetically confirmed cases. Differential diagnosis is considered in the context of suspected retinal and other disorders, including rare syndromes that may masquerade as albinism.
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Affiliation(s)
- Magella M Neveu
- Department Electrophysiology, Moorfields Eye Hospital, London, EC1V 2PD, UK
- Institute of Ophthalmology, University College London, London, UK
| | | | | | - Brijesh Takkar
- Anant Bajaj Retina Institute, LV Prasad Eye Institute, Hyderabad, India
| | - Subhadra Jalali
- Anant Bajaj Retina Institute, LV Prasad Eye Institute, Hyderabad, India
| | - Deepika CP
- Anant Bajaj Retina Institute, LV Prasad Eye Institute, Hyderabad, India
| | - Tapas Ranjan Padhi
- Anant Bajaj Retina Institute, LV Prasad Eye Institute, Bhubaneswar, India
| | - Anthony G Robson
- Department Electrophysiology, Moorfields Eye Hospital, London, EC1V 2PD, UK
- Institute of Ophthalmology, University College London, London, UK
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7
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Age-related reduction of hemispheric asymmetry by pigeons: A behavioral and FDG-PET imaging investigation of visual discrimination. Learn Behav 2022; 50:125-139. [DOI: 10.3758/s13420-021-00507-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2021] [Indexed: 11/08/2022]
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8
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Zeiss CJ. Comparative Milestones in Rodent and Human Postnatal Central Nervous System Development. Toxicol Pathol 2021; 49:1368-1373. [PMID: 34569375 DOI: 10.1177/01926233211046933] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Within the substantially different time scales characterizing human and rodent brain development, key developmental processes are remarkably preserved. Shared processes include neurogenesis, myelination, synaptogenesis, and neuronal and synaptic pruning. In general, altricial rodents experience greater central nervous system (CNS) immaturity at birth and accelerated postnatal development compared to humans, in which protracted development of certain processes such as neocortical myelination and synaptic maturation extend into adulthood. Within this generalization, differences in developmental rates of various structures must be understood to accurately model human neurodevelopmental toxicity in rodents. Examples include greater postnatal neurogenesis in rodents, particularly within the dentate gyrus of rats, ongoing generation of neurons in the rodent olfactory bulb, differing time lines of neurotransmitter maturation, and differing time lines of cerebellar development. Comparisons are made to the precocial guinea pig and the long-lived naked mole rat, which, like primates, experiences more advanced CNS development at birth, with more protracted postnatal development. Methods to study various developmental processes are summarized using examples of comparative postnatal injury in humans and rodents.
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Affiliation(s)
- Caroline J Zeiss
- Department of Comparative Medicine, 12228Yale University School of Medicine, New Haven, CT, USA
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9
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Cwerman-Thibault H, Lechauve C, Malko-Baverel V, Augustin S, Le Guilloux G, Reboussin É, Degardin-Chicaud J, Simonutti M, Debeir T, Corral-Debrinski M. Neuroglobin effectively halts vision loss in Harlequin mice at an advanced stage of optic nerve degeneration. Neurobiol Dis 2021; 159:105483. [PMID: 34400304 DOI: 10.1016/j.nbd.2021.105483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 08/06/2021] [Accepted: 08/11/2021] [Indexed: 10/20/2022] Open
Abstract
Mitochondrial diseases are among the most prevalent groups of inherited neurological disorders, affecting up to 1 in 5000 adults. Despite the progress achieved on the identification of gene mutations causing mitochondrial pathologies, they cannot be cured so far. Harlequin mice, a relevant model of mitochondrial pathology due to apoptosis inducing factor depletion, suffer from progressive disappearance of retinal ganglion cells leading to optic neuropathy. In our previous work, we showed that administering adeno-associated virus encompassing the coding sequences for neuroglobin, (a neuroprotective molecule belonging to the globin family) or apoptosis-inducing factor, before neurodegeneration onset, prevented retinal ganglion cell loss and preserved visual function. One of the challenges to develop an effective treatment for optic neuropathies is to consider that by the time patients become aware of their handicap, a large amount of nerve fibers has already disappeared. Gene therapy was performed in Harlequin mice aged between 4 and 5 months with either a neuroglobin or an apoptosis-inducing factor vector to determine whether the increased abundance of either one of these proteins in retinas could preserve visual function at this advanced stage of the disease. We demonstrated that gene therapy, by preserving the connectivity of transduced retinal ganglion cells and optic nerve bioenergetics, results in the enhancement of visual cortex activity, ultimately rescuing visual impairment. This study demonstrates that: (a) An increased abundance of neuroglobin functionally overcomes apoptosis-inducing factor absence in Harlequin mouse retinas at a late stage of neuronal degeneration; (b) The beneficial effect for visual function could be mediated by neuroglobin localization to the mitochondria, thus contributing to the maintenance of the organelle homeostasis.
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Affiliation(s)
| | - Christophe Lechauve
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, F-75012 Paris, France
| | | | - Sébastien Augustin
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, F-75012 Paris, France
| | | | - Élodie Reboussin
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, F-75012 Paris, France
| | | | - Manuel Simonutti
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, F-75012 Paris, France
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10
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Case report: Unilateral optic nerve aplasia and developmental hemi-chiasmal dysplasia with VEP misrouting. Doc Ophthalmol 2020; 142:247-255. [PMID: 32852652 PMCID: PMC7943516 DOI: 10.1007/s10633-020-09788-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 08/07/2020] [Indexed: 12/02/2022]
Abstract
Purpose To describe the trans-occipital asymmetries of pattern and flash visual evoked potentials (VEPs), in an infant with MRI findings of unilateral optic nerve aplasia and hemi-chiasm dysplasia. Methods A child with suspected left cystic microphthalmia, left microcornea, left unilateral optic nerve aplasia, and hemi-chiasm underwent a multi-channel VEP assessment with pattern reversal, pattern onset, and flash stimulation at the age of 16 weeks. Results There was no VEP evidence of any post-retinal visual pathway activation from left eye with optic nerve aplasia. The VEP trans-occipital distribution from the functional right eye was skewed markedly across the midline, in keeping with significant misrouting of optic nerve fibres at the chiasm. This was supported by the anatomical trajectory of the optic chiasm and tracts seen on MRI. Conclusion This infant has chiasmal misrouting in association with unilateral optic nerve aplasia and unilateral microphthalmos. Chiasmal misrouting has not been found in patients with microphthalmos or anophthalmos, but has been reported after early eye loss in animal models. Our findings contribute to our understanding of the discrepancy between the visual pathway physiology of human unilateral microphthalmia and animal models.
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11
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Altered visual population receptive fields in human albinism. Cortex 2020; 128:107-123. [PMID: 32334151 DOI: 10.1016/j.cortex.2020.03.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 01/10/2020] [Accepted: 03/07/2020] [Indexed: 02/07/2023]
Abstract
Albinism is a congenital disorder where misrouting of the optic nerves at the chiasm gives rise to abnormal visual field representations in occipital cortex. In typical human development, the left occipital cortex receives retinal input predominantly from the right visual field, and vice-versa. In albinism, there is a more complete decussation of optic nerve fibers at the chiasm, resulting in partial representation of the temporal hemiretina (ipsilateral visual field) in the contralateral hemisphere. In this study, we characterize the receptive field properties for these abnormal representations by conducting detailed fMRI population receptive field mapping in a rare subset of participants with albinism and no ocular nystagmus. We find a nasal bias for receptive field positions in the abnormal temporal hemiretina representation. In addition, by modelling responses to bilateral visual field stimulation in the overlap zone, we found evidence in favor of discrete unilateral receptive fields, suggesting a conservative pattern of spatial selectivity in the presence of abnormal retinal input.
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12
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13
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Friocourt F, Chédotal A. The Robo3 receptor, a key player in the development, evolution, and function of commissural systems. Dev Neurobiol 2017; 77:876-890. [DOI: 10.1002/dneu.22478] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 12/04/2016] [Accepted: 12/06/2016] [Indexed: 12/15/2022]
Affiliation(s)
- François Friocourt
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision; 17 Rue Moreau Paris 75012 France
| | - Alain Chédotal
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision; 17 Rue Moreau Paris 75012 France
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14
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Cwerman-Thibault H, Lechauve C, Augustin S, Roussel D, Reboussin É, Mohammad A, Degardin-Chicaud J, Simonutti M, Liang H, Brignole-Baudouin F, Maron A, Debeir T, Corral-Debrinski M. Neuroglobin Can Prevent or Reverse Glaucomatous Progression in DBA/2J Mice. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2017; 5:200-220. [PMID: 28540323 PMCID: PMC5430497 DOI: 10.1016/j.omtm.2017.04.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 04/21/2017] [Indexed: 01/12/2023]
Abstract
Mitochondrial dysfunction is responsible for hereditary optic neuropathies. We wished to determine whether preserving mitochondrial bioenergetics could prevent optic neuropathy in a reliable model of glaucoma. DBA/2J mice exhibit elevated intraocular pressure, progressive degeneration of their retinal ganglion cells, and optic neuropathy that resembles glaucoma. We established that glaucoma in these mice is directly associated with mitochondrial dysfunction: respiratory chain activity was compromised in optic nerves 5 months before neuronal loss began, and the amounts of some mitochondrial proteins were reduced in retinas of glaucomatous mice. One of these proteins is neuroglobin, which has a neuroprotective function. Therefore, we investigated whether gene therapy aimed at restoring neuroglobin levels in the retina via ocular administration of an adeno-associated viral vector could reduce neuronal degeneration. The approach of treating 2-month-old mice impeded glaucoma development: few neurons died and respiratory chain activity and visual cortex activity were comparable to those in young, asymptomatic mice. When the treatment was performed in 8-month-old mice, the surviving neurons acquired new morphologic and functional properties, leading to the preservation of visual cortex activity and respiratory chain activity. The beneficial effects of neuroglobin in DBA/2J retinas confirm this protein to be a promising candidate for treating glaucoma.
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Affiliation(s)
- Hélène Cwerman-Thibault
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
- PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris Cité, 75019 Paris, France
| | - Christophe Lechauve
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
- Department of Hematology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Sébastien Augustin
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
| | - Delphine Roussel
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
- Institut du Cerveau et de la Moelle Épinière, Hôpital Pitié Salpêtrière, 75013 Paris, France
| | - Élodie Reboussin
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
| | - Ammara Mohammad
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
- Genomic Paris Centre, Institut de Biologie de l’Ecole normale supérieure, 46 rue d’Ulm, 75230 Paris, France
| | - Julie Degardin-Chicaud
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
| | - Manuel Simonutti
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
| | - Hong Liang
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
- CHNO des Quinze-Vingts, DHU Sight Restore, INSERM-DHOS CIC, 28 rue de Charenton, 75012 Paris, France
| | - Françoise Brignole-Baudouin
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
| | - Anne Maron
- Sanofi-Aventis, 94400 Vitry-sur-Seine, France
| | - Thomas Debeir
- Departments of Evaluation and Expertise Strategy, Science Policy and External Innovation, Sanofi, 75008 Paris, France
| | - Marisol Corral-Debrinski
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, 75012 Paris, France
- PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris Cité, 75019 Paris, France
- Corresponding author: Marisol Corral-Debrinski, PROTECT, INSERM (UMR1141), Université Paris Diderot, Sorbonne Paris Cité, 48 Boulevard Sérurier, 75019 Paris, France.
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Yohannan DG, George TP, Ramnarayan S. Asymmetric optic tracts in a case of unilateral isolated clinical anophthalmia—A rare case report and review of literature. J ANAT SOC INDIA 2016. [DOI: 10.1016/j.jasi.2017.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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Osanai Y, Shimizu T, Mori T, Yoshimura Y, Hatanaka N, Nambu A, Kimori Y, Koyama S, Kobayashi K, Ikenaka K. Rabies virus-mediated oligodendrocyte labeling reveals a single oligodendrocyte myelinates axons from distinct brain regions. Glia 2016; 65:93-105. [DOI: 10.1002/glia.23076] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 09/09/2016] [Accepted: 09/15/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Yasuyuki Osanai
- Division of Neurobiology and Bioinformatics; National Institute for Physiological Sciences; Okazaki Japan
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
| | - Takeshi Shimizu
- Division of Neurobiology and Bioinformatics; National Institute for Physiological Sciences; Okazaki Japan
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
| | - Takuma Mori
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Division of Visual Information Processing; National Institute for Physiological Sciences; Okazaki Japan
- Department of Molecular and Cellular Physiology; Shinshu University School of Medicine; Matsumoto Japan
| | - Yumiko Yoshimura
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Division of Visual Information Processing; National Institute for Physiological Sciences; Okazaki Japan
| | - Nobuhiko Hatanaka
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Division of System Neurophysiology; National Institute for Physiological Sciences; Okazaki Japan
| | - Atsushi Nambu
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Division of System Neurophysiology; National Institute for Physiological Sciences; Okazaki Japan
| | - Yoshitaka Kimori
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Imaging Science Division; Center for Novel Science Initiatives, National Institutes of Natural Sciences; Okazaki Japan
| | - Shinsuke Koyama
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Department of Statistical Modeling; Institute of Statistical Mathematics; Tokyo Japan
| | - Kenta Kobayashi
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
- Section of Viral Vector Development; National Institute for Physiological Sciences; Okazaki Japan
| | - Kazuhiro Ikenaka
- Division of Neurobiology and Bioinformatics; National Institute for Physiological Sciences; Okazaki Japan
- SOKENDAI (The Graduate University for Advanced Studies); Okazaki Japan
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17
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Human Pluripotent Stem Cell-Derived Retinal Ganglion Cells: Applications for the Study and Treatment of Optic Neuropathies. CURRENT OPHTHALMOLOGY REPORTS 2015; 3:200-206. [PMID: 26618076 DOI: 10.1007/s40135-015-0081-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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18
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Ramírez AI, Salazar JJ, de Hoz R, Rojas B, Gallego BI, Salobrar-García E, Valiente-Soriano FJ, Triviño A, Ramirez JM. Macro- and microglial responses in the fellow eyes contralateral to glaucomatous eyes. PROGRESS IN BRAIN RESEARCH 2015; 220:155-72. [PMID: 26497789 DOI: 10.1016/bs.pbr.2015.05.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Most studies employing experimental models of unilateral glaucoma have used the normotensive contralateral eye as the normal control. However, some studies have recently reported the activation of the retinal macroglia and microglia in the uninjured eye, suggesting that the eye contralateral to experimental glaucoma should not be used as a control. This review analyzes the studies describing the contralateral findings and discusses some of the routes through which the signals can reach the contralateral eye to initiate the glial reactivation.
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Affiliation(s)
- Ana I Ramírez
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Spain.
| | - Juan J Salazar
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Spain
| | - Rosa de Hoz
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Facultad de Óptica y Optometría, Universidad Complutense de Madrid, Spain
| | - Blanca Rojas
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Departamento de Oftalmología y ORL, Facultad de Medicina, Universidad Complutense de Madrid, Spain
| | - Beatriz I Gallego
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Universidad Complutense de Madrid, Spain
| | - Elena Salobrar-García
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Universidad Complutense de Madrid, Spain
| | - Francisco J Valiente-Soriano
- Laboratorio de Oftalmología Experimental, Departamento de Oftalmología, Facultad de Medicina, Universidad de Murcia, Spain
| | - Alberto Triviño
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Departamento de Oftalmología y ORL, Facultad de Medicina, Universidad Complutense de Madrid, Spain
| | - José M Ramirez
- Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Departamento de Oftalmología y ORL, Facultad de Medicina, Universidad Complutense de Madrid, Spain
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19
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Yang S, He H, Zhu Y, Wan X, Zhou LF, Wang J, Wang WF, Liu L, Li B. Chemical and material communication between the optic nerves in rats. Clin Exp Ophthalmol 2015; 43:742-8. [PMID: 25950380 DOI: 10.1111/ceo.12547] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 04/30/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND To examine interactions between optic nerves. METHODS A total of 24 Sprague-Dawley rats received unilateral intravitreal injections. The rats were equally divided into four groups: group A was administered an adeno-associated virus (AAV) carrying an exogenous gene (ND4; rAAV-ND4); group B, AAV carrying a green fluorescent protein (GFP; rAAV-GFP); group C, fluorogold (FG) nerve tracer dye; and group D, phosphate-buffered saline (PBS) as a control. Two weeks later, GFP expression was evaluated in both retinas and optic nerves of group B rats after frozen sectioning. The presence of FG was also evaluated in group C optic nerves by fluorescent microscopy after frozen sectioning. Four weeks after injection, ND4 expression was evaluated in both eyes of groups A and D using western blotting and immunofluorescence. RESULTS FG was observed in the optic chiasm posterior segment along the optic nerve of injected eyes. Some FG reached the anterior optic nerve of the non-injected eye. GFP fluorescence was observed only in the retina of the injected eye but not in the contralateral retina or either optic nerve. ND4 expression was significantly different between injected and non-injected eyes but not between the non-injected eyes in groups A and D. CONCLUSION Unilaterally injected material can reach the contralateral optic nerve through axoplasmic transport. It is possible that this the only mechanism by which the optic nerves directly communicate.
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Affiliation(s)
- Shuo Yang
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China.,Department of Optometry and Ophthalmology Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Heng He
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Ying Zhu
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Xing Wan
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Long-Fang Zhou
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Juan Wang
- Department of Optometry and Ophthalmology Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Wen-Feng Wang
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Lei Liu
- Department of Optometry and Ophthalmology Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Bin Li
- Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
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20
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Maxwell WL, Bartlett E, Morgan H. Wallerian degeneration in the optic nerve stretch-injury model of traumatic brain injury: a stereological analysis. J Neurotrauma 2015; 32:780-90. [PMID: 25333317 DOI: 10.1089/neu.2014.3369] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Patients with chronic traumatic encephalopathy (CTE) show loss of central white matter, central gray matter, and cortical gray matter with increasing post-traumatic survival. The majority of experimental studies using animals have, however, discussed only the ultrastructural pathophysiology of injured central white matter leading to secondary axotomy and the formation of axonal terminal bulbs. Using the stretch-injured optic nerve model in adult guinea pigs, the present study provides novel quantitative data concerning Wallerian degeneration of disconnected axonal fragments following secondary axotomy out to 12 weeks after injury to an optic nerve. The time course of Wallerian degeneration at the level of an individual nerve fiber is comparable to that reported in earlier studies over 48 h to two weeks after secondary axotomy. But only a relatively small proportion of nerve fibers within the optic tract degenerate via Wallerian degeneration during the first two weeks. Rather, examples of each of the three stages of Wallerian degeneration-acute axonal degeneration, latency of the distal axonal segment, and granular fragmentation-occur within the optic tract across the entire experimental survival of 12 weeks used in the present study. This data suggests that some nerve fibers initiate Wallerian degeneration days and weeks after the initial time of mechanical injury to an optic nerve. The number of intact nerve fibers continues to fall over at least three months after injury in the stretch-injury model of traumatic axonal injury. It is suggested that these novel findings relate to the mechanism(s) whereby central white matter volume decreases over months and years in CTE patients.
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Affiliation(s)
- William L Maxwell
- Department of Anatomy, University of Glasgow, Glasgow, United Kingdom
| | - Emma Bartlett
- Department of Anatomy, University of Glasgow, Glasgow, United Kingdom
| | - Hanna Morgan
- Department of Anatomy, University of Glasgow, Glasgow, United Kingdom
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21
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22
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Thanos S, Böhm MRR, Schallenberg M, Oellers P. Traumatology of the optic nerve and contribution of crystallins to axonal regeneration. Cell Tissue Res 2012; 349:49-69. [PMID: 22638995 DOI: 10.1007/s00441-012-1442-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 04/26/2012] [Indexed: 11/29/2022]
Abstract
Within a few decades, the repair of long neuronal pathways such as spinal cord tracts, the optic nerve or intracerebral tracts has gone from being strongly contested to being recognized as a potential clinical challenge. Cut axonal stumps within the optic nerve were originally thought to retract and become irreversibly necrotic within the injury zone. Optic nerve astrocytes were assumed to form a gliotic scar and remodelling of the extracellular matrix to result in a forbidden environment for re-growth of axons. Retrograde signals to the ganglion cell bodies were considered to prevent anabolism, thus also initiating apoptotic death and gliotic repair within the retina. However, increasing evidence suggests the reversibility of these regressive processes, as shown by the analysis of molecular events at the site of injury and within ganglion cells. We review optic nerve repair from the perspective of the proximal axon stump being a major player in determining the successful formation of a growth cone. The axonal stump and consequently the prospective growth cone, communicates with astrocytes, microglial cells and the extracellular matrix via a panoply of molecular tools. We initially highlight these aspects on the basis of recent data from numerous laboratories. Then, we examine the mechanisms by which an injury-induced growth cone can sense its surroundings within the area distal to the injury. Based on requirements for successful axonal elongation within the optic nerve, we explore the models employed to instigate successful growth cone formation by ganglion cell stimulation and optic nerve remodelling, which in turn accelerate growth. Ultimately, with regard to the proteomics of regenerating retinal tissue, we discuss the discovery of isoforms of crystallins, with crystallin beta-b2 (crybb2) being clearly upregulated in the regenerating retina. Crystallins are produced and used to promote the elongation of growth cones. In vivo and in vitro, crystallins beta and gamma additionally promote the growth of axons by enhancing the production of ciliary neurotrophic factor (CNTF), indicating that they also act on astrocytes to promote axonal regrowth synergistically. These are the first data showing that axonal regeneration is related to crybb2 movement within neurons and to additional stimulation of CNTF. We demonstrate that neuronal crystallins constitute a novel class of neurite-promoting factors that probably operate through an autocrine and paracrine mechanism and that they can be used in neurodegenerative diseases. Thus, the post-injury fate of neurons cannot be seen merely as inevitable but, instead, must be regarded as a challenge to shape conditions for initiating growth cone formation to repair the damaged optic nerve.
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Affiliation(s)
- Solon Thanos
- Institute of Experimental Ophthalmology, School of Medicine, University of Münster, Albert-Schweitzer-Campus 1, D15, 48149 Münster, Germany.
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Abstract
Both see-saw nystagmus and dissociated vertical divergence are cyclovertical eye movements characterized by vertical disconjugation and torsional conjugation. See-saw nystagmus is known to occur with chiasmal disorders and bitemporal hemianopia. Dissociated vertical divergence is commonly encountered in the infantile strabismus syndrome. A hypothetical model is presented in which both conditions are explained. The basic organization of the oculomotor system is most likely monocular and synchronous eye movements may have developed by neuronal coupling of the symmetrical oculomotor structures. The vertical dissociation of both eye movement disorders is explained by insufficiently developed neuronal coupling between the superior colliculi. A functional differentiation between crossed and uncrossed retinal ganglion cells fibers is assumed to cause this diminished binocular coupling in the case of see-saw nystagmus. The interstitial nucleus of Cajal may well play a pivotal role in explaining the distinct torsional eye movements in both conditions.
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Knabe W, Washausen S, Happel N, Kuhn HJ. Diversity in mammalian chiasmatic architecture: ipsilateral axons are deflected at glial arches in the prechiasmatic optic nerve of the eutherian Tupaia belangeri. J Comp Neurol 2008; 508:437-57. [PMID: 18335540 DOI: 10.1002/cne.21694] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Permanent ipsilaterally projecting axons approach the chiasmatic midline in rodents but are confined to lateral parts of the optic chiasm in marsupials. Hence, principally different mechanisms were thought to underlie axon pathway choice in eutherian (placental) and marsupial mammals. First evidence of diversity in eutherian chiasmatic architecture came from studies in the newborn and adult tree shrew Tupaia belangeri (Jeffery et al. [1998] J. Comp. Neurol. 390:183-193). Here, as in marsupials, ipsilaterally projecting axons do not approach the midline. The present study aims to clarify how the developing tree shrew chiasm is organized, how glial cells are arranged therein, and the extent to which the tree shrew chiasm is similar to that of marsupials or other eutherians. By using routinely stained serial sections as well as immunohistochemistry with antibodies against glial fibrillary acidic protein, vimentin, and medium-molecular-weight neurofilament protein, we investigated chiasm formation from embryonic day 18 (E18) to birth (E43). From E22 onward, ipsilaterally projecting axons diverged from contralaterally projecting axons in prechiasmatic parts of the optic nerve. They made sharp turns when arriving at glial arches found at the transition from the optic nerve to the chiasm. Thus, during the ingrowth period of axons, Tupaia belangeri and marsupials have specialized glial arrays in common, which probably help to deflect ipsilaterally projecting axons to lateral parts of the chiasm. Our observations provide new evidence of diversity in eutherian chiasmatic architecture and identify Tupaia belangeri as an appropriate animal model for studies on the mechanisms underlying axon guidance in the developing chiasm of higher primates.
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Affiliation(s)
- Wolfgang Knabe
- Department of Anatomy and Embryology, Georg August University, D-37075 Göttingen, Germany.
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