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Karalis V, Wood D, Teaney NA, Sahin M. The role of TSC1 and TSC2 proteins in neuronal axons. Mol Psychiatry 2024; 29:1165-1178. [PMID: 38212374 DOI: 10.1038/s41380-023-02402-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 12/20/2023] [Accepted: 12/22/2023] [Indexed: 01/13/2024]
Abstract
Tuberous Sclerosis Complex 1 and 2 proteins, TSC1 and TSC2 respectively, participate in a multiprotein complex with a crucial role for the proper development and function of the nervous system. This complex primarily acts as an inhibitor of the mechanistic target of rapamycin (mTOR) kinase, and mutations in either TSC1 or TSC2 cause a neurodevelopmental disorder called Tuberous Sclerosis Complex (TSC). Neurological manifestations of TSC include brain lesions, epilepsy, autism, and intellectual disability. On the cellular level, the TSC/mTOR signaling axis regulates multiple anabolic and catabolic processes, but it is not clear how these processes contribute to specific neurologic phenotypes. Hence, several studies have aimed to elucidate the role of this signaling pathway in neurons. Of particular interest are axons, as axonal defects are associated with severe neurocognitive impairments. Here, we review findings regarding the role of the TSC1/2 protein complex in axons. Specifically, we will discuss how TSC1/2 canonical and non-canonical functions contribute to the formation and integrity of axonal structure and function.
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Affiliation(s)
- Vasiliki Karalis
- Rosamund Stone Zander Translational Neuroscience Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
- FM Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Delaney Wood
- FM Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
- Human Neuron Core, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Nicole A Teaney
- Rosamund Stone Zander Translational Neuroscience Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
- FM Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Mustafa Sahin
- Rosamund Stone Zander Translational Neuroscience Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA.
- FM Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA.
- Human Neuron Core, Boston Children's Hospital, Boston, MA, 02115, USA.
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Zhou ZX, Xu LJ, Wang HN, Cheng S, Li F, Miao Y, Lei B, Gao F, Wang Z. EphA4/ephrinA3 reverse signaling mediated downregulation of glutamate transporter GLAST in Müller cells in an experimental glaucoma model. Glia 2023; 71:720-741. [PMID: 36416239 DOI: 10.1002/glia.24307] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 11/07/2022] [Accepted: 11/12/2022] [Indexed: 11/24/2022]
Abstract
Deficiency of glutamate transporter GLAST in Müller cells may be culpable for excessive extracellular glutamate, which involves in retinal ganglion cell (RGC) damage in glaucoma. We elucidated how GLAST was regulated in rat chronic ocular hypertension (COH) model. Western blot and whole-cell patch-clamp recordings showed that GLAST proteins and GLAST-mediated current densities in Müller cells were downregulated at the early stages of COH. In normal rats, intravitreal injection of the ephrinA3 activator EphA4-Fc mimicked the changes of GLAST in COH retinas. In purified cultured Müller cells, EphA4-Fc treatment reduced GLAST expression at mRNA and protein levels, which was reversed by the tyrosine kinase inhibitor PP2 or transfection with ephrinA3-siRNA (Si-EFNA3), suggesting that EphA4/ephrinA3 reverse signaling mediated GLAST downregulation. EphA4/ephrinA3 reverse signaling-induced GLAST downregulation was mediated by inhibiting PI3K/Akt/NF-κB pathways since EphA4-Fc treatment of cultured Müller cells reduced the levels of p-Akt/Akt and NF-κB p65, which were reversed by transfecting Si-EFNA3. In Müller cells with ephrinA3 knockdown, the PI3K inhibitor LY294002 still decreased the protein levels of NF-κB p65 in the presence of EphA4-Fc, and the mRNA levels of GLAST were reduced by LY294002 and the NF-κB inhibitor SN50, respectively. Pre-injection of the PI3K/Akt pathway activator 740 Y-P reversed the GLAST downregulation in COH retinas. Western blot and TUNEL staining showed that transfecting of Si-EFNA3 reduced Müller cell gliosis and RGC apoptosis in COH retinas. Our results suggest that activated EphA4/ephrinA3 reverse signaling induces GLAST downregulation in Müller cells via inhibiting PI3K/Akt/NF-κB pathways, thus contributing to RGC damage in glaucoma.
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Affiliation(s)
- Zhi-Xin Zhou
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Lin-Jie Xu
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Hong-Ning Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Shuo Cheng
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Fang Li
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Yanying Miao
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Bo Lei
- Institutes of Neuroscience and Third Affiliated Hospital, Henan Provincial People's Hospital, Henan Eye Institute, Henan Eye Hospital, People's Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
| | - Feng Gao
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, NHC Key Laboratory of Myopia, Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Zhongfeng Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
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Xu LJ, Wang HN, Zhou H, Li SY, Li F, Miao Y, Lei B, Sun XH, Gao F, Wang Z. EphA4/ephrinA3 reverse signaling induced Müller cell gliosis and production of pro-inflammatory cytokines in experimental glaucoma. Brain Res 2023; 1801:148204. [PMID: 36529265 DOI: 10.1016/j.brainres.2022.148204] [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: 10/12/2022] [Revised: 11/18/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022]
Abstract
Previous work showed that ephrinA3/EphA4 forward signaling contributed to retinal ganglion cell (RGC) damage in experimental glaucoma. Since up-regulated patterns of ephrinA3 and EphA4 were observed in Müller cells and RGCs, an EphA4/ephrinA3 reverse signaling may exist in Müller cells of chronic ocular hypertension (COH) retina. We investigated effects of EphA4/ephrinA3 reverse signaling activation on Müller cells in COH retina. Intravitreal injection of the ephrinA3 agonist EphA4-Fc increased glial fibrillary acidic protein (GFAP) levels in normal retinas, suggestive of Müller cell gliosis, which was confirmed in purified cultured Müller cells treated with EphA4-Fc. These effects were mediated by intracellular STAT3 signaling pathway as phosphorylated STAT3 (p-STAT3) levels and ratios of p-STAT3/STAT3 were significantly increased in both COH retinas and EphA4-Fc intravitreally injected retinas, as well as in EphA4-Fc treated purified cultured Müller cells. The increase of GFAP protein levels in EphA4-Fc-injected retinas and EphA4-Fc treated purified cultured Müller cells could be partially eliminated by stattic, a selective STAT3 blocker. Co-immunoprecipitation results testified to the presence of interaction between ephrinA3 and STAT3/p-STAT3. In addition, intravitreal injection of EphA4-Fc or EphA4-Fc treatment of cultured Müller cells significantly up-regulated mRNA and protein contents of pro-inflammatory cytokines. Moreover, intravitreal injection of EphA4-Fc increased the number of apoptotic RGCs, which could be reversed by the tyrosine kinase blocker PP2. Overall, EphA4/ephrinA3 reverse signaling may induce Müller cell gliosis and increases release of pro-inflammatory factors, which could contribute to RGC death in glaucoma. Inhibition of EphA4/ephrinA3 signaling may provide an effective neuroprotection in glaucoma.
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Affiliation(s)
- Lin-Jie Xu
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
| | - Hong-Ning Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
| | - Han Zhou
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
| | - Shu-Ying Li
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
| | - Fang Li
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
| | - Yanying Miao
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
| | - Bo Lei
- Institute of Neuroscience and Third Affiliated Hospital, Henan Provincial People's Hospital, Henan Eye Institute, Henan Eye Hospital, People's Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou 450003, China
| | - Xing-Huai Sun
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, NHC Key Laboratory of Myopia, Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai 200031, China.
| | - Feng Gao
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, NHC Key Laboratory of Myopia, Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai 200031, China.
| | - Zhongfeng Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai 200032, China.
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Jure R. The “Primitive Brain Dysfunction” Theory of Autism: The Superior Colliculus Role. Front Integr Neurosci 2022; 16:797391. [PMID: 35712344 PMCID: PMC9194533 DOI: 10.3389/fnint.2022.797391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 04/19/2022] [Indexed: 11/20/2022] Open
Abstract
A better understanding of the pathogenesis of autism will help clarify our conception of the complexity of normal brain development. The crucial deficit may lie in the postnatal changes that vision produces in the brainstem nuclei during early life. The superior colliculus is the primary brainstem visual center. Although difficult to examine in humans with present techniques, it is known to support behaviors essential for every vertebrate to survive, such as the ability to pay attention to relevant stimuli and to produce automatic motor responses based on sensory input. From birth to death, it acts as a brain sentinel that influences basic aspects of our behavior. It is the main brainstem hub that lies between the environment and the rest of the higher neural system, making continuous, implicit decisions about where to direct our attention. The conserved cortex-like organization of the superior colliculus in all vertebrates allows the early appearance of primitive emotionally-related behaviors essential for survival. It contains first-line specialized neurons enabling the detection and tracking of faces and movements from birth. During development, it also sends the appropriate impulses to help shape brain areas necessary for social-communicative abilities. These abilities require the analysis of numerous variables, such as the simultaneous evaluation of incoming information sustained by separate brain networks (visual, auditory and sensory-motor, social, emotional, etc.), and predictive capabilities which compare present events to previous experiences and possible responses. These critical aspects of decision-making allow us to evaluate the impact that our response or behavior may provoke in others. The purpose of this review is to show that several enigmas about the complexity of autism might be explained by disruptions of collicular and brainstem functions. The results of two separate lines of investigation: 1. the cognitive, etiologic, and pathogenic aspects of autism on one hand, and two. the functional anatomy of the colliculus on the other, are considered in order to bridge the gap between basic brain science and clinical studies and to promote future research in this unexplored area.
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Neurospheres obtained from the ciliary margin of the chicken eye possess positional values and retinal ganglion cells differentiated from them respond to EphA/ephrin-A system. Exp Eye Res 2022; 217:108965. [DOI: 10.1016/j.exer.2022.108965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 12/14/2021] [Accepted: 01/25/2022] [Indexed: 11/23/2022]
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Trigila AP, Pisciottano F, Franchini LF. Hearing loss genes reveal patterns of adaptive evolution at the coding and non-coding levels in mammals. BMC Biol 2021; 19:244. [PMID: 34784928 PMCID: PMC8594068 DOI: 10.1186/s12915-021-01170-6] [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: 11/20/2020] [Accepted: 10/21/2021] [Indexed: 11/26/2022] Open
Abstract
Background Mammals possess unique hearing capacities that differ significantly from those of the rest of the amniotes. In order to gain insights into the evolution of the mammalian inner ear, we aim to identify the set of genetic changes and the evolutionary forces that underlie this process. We hypothesize that genes that impair hearing when mutated in humans or in mice (hearing loss (HL) genes) must play important roles in the development and physiology of the inner ear and may have been targets of selective forces across the evolution of mammals. Additionally, we investigated if these HL genes underwent a human-specific evolutionary process that could underlie the evolution of phenotypic traits that characterize human hearing. Results We compiled a dataset of HL genes including non-syndromic deafness genes identified by genetic screenings in humans and mice. We found that many genes including those required for the normal function of the inner ear such as LOXHD1, TMC1, OTOF, CDH23, and PCDH15 show strong signatures of positive selection. We also found numerous noncoding accelerated regions in HL genes, and among them, we identified active transcriptional enhancers through functional enhancer assays in transgenic zebrafish. Conclusions Our results indicate that the key inner ear genes and regulatory regions underwent adaptive evolution in the basal branch of mammals and along the human-specific branch, suggesting that they could have played an important role in the functional remodeling of the cochlea. Altogether, our data suggest that morphological and functional evolution could be attained through molecular changes affecting both coding and noncoding regulatory regions. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01170-6.
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Affiliation(s)
- Anabella P Trigila
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1428, Buenos Aires, Argentina
| | - Francisco Pisciottano
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1428, Buenos Aires, Argentina.,Current address: Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1428, Buenos Aires, Argentina
| | - Lucía F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1428, Buenos Aires, Argentina.
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Levin B, Simonov E, Gabrielyan BK, Mayden RL, Rastorguev SM, Roubenyan HR, Sharko FS, Nedoluzhko AV. Caucasian treasure: Genomics sheds light on the evolution of half-extinct Sevan trout, Salmo ischchan, species flock. Mol Phylogenet Evol 2021; 167:107346. [PMID: 34763069 DOI: 10.1016/j.ympev.2021.107346] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 11/01/2021] [Accepted: 11/03/2021] [Indexed: 12/14/2022]
Abstract
Five ecologically and phenotypically divergent ecomorphs of the genus Salmo are known from a landlocked alpine lake in the Caucasus, Lake Sevan. It is an example of sympatric diversification within a species-rich lineage with predominate mode of speciation being allopatric. The diversification of Sevan trouts was accompanied by spawning resource partitioning. Four lacustrine ecomorphs with different temporal-spatial spawning strategies and divergent morphology and coloration evolved along with a fifth ecomorph, brook trout, inhabiting the tributaries. Unfortunately, the Sevan trout diversity was almost destroyed by human activity, with two ecomorphs becoming extinct in the 1980s. We performed reconstruction of the evolutionary history of Sevan trouts based on high-throughput sequencing of both contemporary and historical DNA (∼ 50 y.o.) of all Sevan trout ecomorphs. Our study of complete mitogenomes along with genome-wide SNP data revealed the monophyly of four lacustrine ecomorphs and local brook trout, all derived from the anadromous form Caspian salmon, S. caspius. The species tree suggests a scenario of stepwise evolution from riverine to lacustrine spawning. Three genomic clusters were revealed, of which two refer to the riverine and lacustrine spawners within the flock of Sevan trouts (with FST value = 0.069). A few SNP outliers under selection were discovered that could be responsible for assortative mating based on visual recognition. The Holocene climatic oscillations and the desiccation of tributaries could have played an important role in the origin of lacustrine spawning. The relationships between lacustrine ecomorphs were not yet fully resolved. This radiation warrants further investigation.
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Affiliation(s)
- Boris Levin
- Zoological Institute of Russian Academy of Sciences, St. Petersburg, Russia; Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences - Borok, Russia; Cherepovets State University, Cherepovets, Russia.
| | | | - Bardukh K Gabrielyan
- Scientific Center of Zoology and Hydroecology, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia
| | - Richard L Mayden
- Department of Biology, Saint Louis University, St. Louis, MO USA
| | | | - Haikaz R Roubenyan
- Scientific Center of Zoology and Hydroecology, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia
| | - Fedor S Sharko
- National Research Centre "Kurchatov Institute", Moscow, Russia
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Wu J, Lu B, Yang R, Chen Y, Chen X, Li Y. EphB2 knockdown decreases the formation of astroglial-fibrotic scars to promote nerve regeneration after spinal cord injury in rats. CNS Neurosci Ther 2021; 27:714-724. [PMID: 33794069 PMCID: PMC8111500 DOI: 10.1111/cns.13641] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 02/17/2021] [Accepted: 03/17/2021] [Indexed: 01/13/2023] Open
Abstract
Aims At the beginning of spinal cord injury (SCI), the expression of EphB2 on fibroblasts and ephrin‐B2 on astrocytes increased simultaneously and their binding triggers the formation of astroglial‐fibrotic scars, which represent a barrier to axonal regeneration. In the present study, we sought to suppress scar formation and to promote recovery from SCI by targeting EphB2 in vivo. Methods The female rats SCI models were used in vivo experiments by subsequently injecting with EphB2 shRNA lentiviruses. The effect on EphB2 knockdown was evaluated at 14 days after injury. The repair outcomes were evaluated at 3 months by electrophysiological and morphological assessments to regenerated nerve tissue. The EphB2 expression and TGF‐β1 secretion were detected in vitro using a lipopolysaccharides (LPS)‐induced astrocyte injury model. Results RNAi decreased the expression of EphB2 after SCI, which effectively inhibited fibroblasts and astrocytes from aggregating at 14 days. The expression of EphB2 in activated astrocytes, in addition to fibroblasts, was significantly increased after SCI in vivo, in line with upregulated expression of EphB2 and increased secretion of TGF‐β1 in astrocyte culture treated with LPS. Compared to the scramble control, RNAi targeting with EphB2 could promote more nerve regeneration and better myelination. Conclusions EphB2 knockdown may effectively inhibit the formation of astroglial‐fibrotic scars at the beginning of SCI. It is beneficial to eliminate the barrier of nerve regeneration.
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Affiliation(s)
- Jian Wu
- Department of Histology and Embryology, Medical School, Nantong University, Nantong, China
| | - Bing Lu
- Department of Histology and Embryology, Medical School, Nantong University, Nantong, China
| | - Riyun Yang
- Department of Histology and Embryology, Medical School, Nantong University, Nantong, China
| | - Ying Chen
- Department of Histology and Embryology, Medical School, Nantong University, Nantong, China
| | - Xue Chen
- Wuxi Medical School, Jiangnan University, Wuxi, China
| | - Yi Li
- Department of Histology and Embryology, Medical School, Nantong University, Nantong, China
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Xu LJ, Gao F, Cheng S, Zhou ZX, Li F, Miao Y, Niu WR, Yuan F, Sun XH, Wang Z. Activated ephrinA3/EphA4 forward signaling induces retinal ganglion cell apoptosis in experimental glaucoma. Neuropharmacology 2020; 178:108228. [PMID: 32745487 DOI: 10.1016/j.neuropharm.2020.108228] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 06/16/2020] [Accepted: 07/01/2020] [Indexed: 12/12/2022]
Abstract
Previous studies have demonstrated that EphA4 participates in neuronal injury, and there is a strong interaction between ephrinA3 and EphA4. In this study, we showed that in a rat chronic ocular hypertension (COH) experimental glaucoma model, expression of EphA4 and ephrinA3 proteins was increased in retinal cells, including retinal ganglion cells (RGCs) and Müller cells, which may result in ephrinA3/EphA4 forward signaling activation on RGCs, as evidenced by increased p-EphA4/EphA4 ratio. Intravitreal injection of ephrinA3-Fc, an activator of EphA4, mimicked the effect of COH on p-EphA4/EphA4 and induced an increase in TUNEL-positive signals in normal retinas, which was accompanied by dendritic spine retraction and thinner dendrites in RGCs. Furthermore, Intravitreal injection of ephrinA3-Fc increased the levels of phosphorylated src and GluA2 (p-src and p-GluA2). Co-immunoprecipitation assay demonstrated interactions between EphA4, p-src and GluA2. Intravitreal injection of ephrinA3-Fc reduced the expression of GluA2 proteins on the surface of normal retinal cells, which was prevented by intravitreal injection of PP2, an inhibitor of src-family tyrosine kinases. Pre-injection of PP2 or the Ca2+-permeable GluA2-lacking AMPA receptor inhibitor Naspm significantly and partially reduced the number of TUNEL-positive RGCs in the ephrinA3-Fc-injected and COH retinas. Our results suggest that activated ephrinA3/EphA4 forward signaling promoted GluA2 endocytosis, then resulted in dendritic spine retraction of RGCs, thus contributing to RGC apoptosis in COH rats. Attenuation of the strength of ephrinA/EphA signaling in an appropriate manner may be an effective way for preventing the loss of RGCs in glaucoma.
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Affiliation(s)
- Lin-Jie Xu
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Feng Gao
- Department of Ophthalmology and Visual Science, Eye & ENT Hospital, Shanghai Key Laboratory of Visual Impairment and Restoration, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200031, China
| | - Shuo Cheng
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Zhi-Xin Zhou
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Fang Li
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Yanying Miao
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Wei-Ran Niu
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Fei Yuan
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Xing-Huai Sun
- Department of Ophthalmology and Visual Science, Eye & ENT Hospital, Shanghai Key Laboratory of Visual Impairment and Restoration, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 200031, China.
| | - Zhongfeng Wang
- Department of Ophthalmology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, 200032, China.
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Ning XJ, Lu XH, Luo JC, Chen C, Gao Q, Li ZY, Wang H. Molecular mechanism of microRNA-21 promoting Schwann cell proliferation and axon regeneration during injured nerve repair. RNA Biol 2020; 17:1508-1519. [PMID: 32507001 DOI: 10.1080/15476286.2020.1777767] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
At present, the functional recovery after nerve injury is not satisfactory in clinical practice. The aim of this study was to explore the molecular mechanism of miR-21 promoting Schwann cells (SC) proliferation and axon regeneration after peripheral nerve injury, providing a theoretical basis for injured nerve repair. Nerve injury models were constructed to determine the expression of miR-21 in the injured nerve by Quantitative Real-Time PCR (qRT-PCR). After miR-21 over-expression SC (mimic-miR-21) group, control SC (control-miR-21) group and blank SC (RSC96) group were constructed, SC proliferation was determined by CCK-8, cell cycle was analysed by flow cytometry, dorsal root ganglion neuron (DRGn) axon regeneration was observed after DRGn was cultured with SCs for 7 days, the expressions of TGFβI, TIMP3, EPHA4 as well as apoptosis-related proteins caspase-3 and caspase-9 were detected by qRT-PCR and Western blot in the three groups, respectively. Target genes were confirmed by dual-luciferase reporter gene assay. The expressions of TGFβI, TIMP3 and EPHA4 were assessed by immunofluorescence in vivo. qRT-PCR indicated that miR-21 expression was significantly higher in the model group than in the sham operation and blank groups. SC proliferation index (PI) was significantly higher, the apoptosis rate was significantly lower, the axon was significantly longer, and mRNA and protein expressions of TGFβI, TIMP3, EPHA4 as well as apoptosis-related proteins caspase-3 and caspase-9 were significantly lower in the mimic-miR-21 group than in the control-miR-21 and RSC96 groups. The double luciferase assay confirmed that TGFβI, TIMP3 and EPHA4 were potential target genes of miR-21. In vivo immunofluorescence also indicated that expressions of TGFβI, TIMP3, EPHA4 were lower in the mimic-miR-21 group than in the control-miR-21 and RSC96 groups. We conclude that during injured peripheral nerve repair, miRNA-21 plays an important role in promoting SC proliferation and axon regeneration by regulating TGFβI, TIMP3 and EPHA4 target genes.
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Affiliation(s)
- Xin-Jie Ning
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
| | - Xin-Hua Lu
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
| | - Jun-Cheng Luo
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
| | - Chuan Chen
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
| | - Qun Gao
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
| | - Zhang-Yu Li
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
| | - Hui Wang
- Department of Neurosurgery, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou, China
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Medori M, Spelzini G, Scicolone G. Molecular complexity of visual mapping: a challenge for regenerating therapy. Neural Regen Res 2020; 15:382-389. [PMID: 31571645 PMCID: PMC6921353 DOI: 10.4103/1673-5374.266044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Investigating the cellular and molecular mechanisms involved in the development of topographically ordered connections in the central nervous system constitutes an important issue in neurobiology because these connections are the base of the central nervous system normal function. The dominant model to study the development of topographic maps is the projection from the retinal ganglion cells to the optic tectum/colliculus. The expression pattern of Eph/ephrin system in opposing gradients both in the retina and the tectum, labels the local addresses on the target and gives specific sensitivities to growth cones according to their topographic origin in the retina. The rigid precision of normal retinotopic mapping has prompted the chemoaffinity hypothesis, positing axonal targeting to be based on fixed biochemical affinities between fibers and targets. However, several lines of evidence have shown that the mapping can adjust to experimentally modified targets with flexibility, demonstrating the robustness of the guidance process. Here we discuss the complex ways the Ephs and ephrins interact allowing to understand how the retinotectal mapping is a precise but also a flexible process.
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Affiliation(s)
- Mara Medori
- CONICET - Universidad de Buenos Aires, Instituto de Biología Celular y Neurociencias "Prof. E. De Robertis" (IBCN); Universidad de Buenos Aires, Facultad de Medicina, Departamento de Biología Celular, Histología, Embriología y Genética, Ciudad Autónoma de Buenos Aires, Argentina
| | - Gonzalo Spelzini
- CONICET - Universidad de Buenos Aires, Instituto de Biología Celular y Neurociencias "Prof. E. De Robertis" (IBCN); Universidad de Buenos Aires, Facultad de Medicina, Departamento de Biología Celular, Histología, Embriología y Genética, Ciudad Autónoma de Buenos Aires, Argentina
| | - Gabriel Scicolone
- CONICET - Universidad de Buenos Aires, Instituto de Biología Celular y Neurociencias "Prof. E. De Robertis" (IBCN); Universidad de Buenos Aires, Facultad de Medicina, Departamento de Biología Celular, Histología, Embriología y Genética, Ciudad Autónoma de Buenos Aires, Argentina
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12
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Regulation of axonal EphA4 forward signaling is involved in the effect of EphA3 on chicken retinal ganglion cell axon growth during retinotectal mapping. Exp Eye Res 2019; 178:46-60. [DOI: 10.1016/j.exer.2018.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 09/06/2018] [Accepted: 09/16/2018] [Indexed: 12/22/2022]
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14
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Savier E, Reber M. Visual Maps Development: Reconsidering the Role of Retinal Efnas and Basic Principle of Map Alignment. Front Cell Neurosci 2018; 12:77. [PMID: 29618973 PMCID: PMC5871686 DOI: 10.3389/fncel.2018.00077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/06/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- Elise Savier
- Centre National de la Recherche Scientifique, UPR3212 - Institute of Cellular and Integrative Neurosciences, University of Strasbourg, Strasbourg, France.,Neuroscience, Department of Biology, University of Virginia, Charlottesville, VA, United States
| | - Michael Reber
- Centre National de la Recherche Scientifique, UPR3212 - Institute of Cellular and Integrative Neurosciences, University of Strasbourg, Strasbourg, France.,Donald K. Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, ON, Canada
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15
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Reinhard J, Joachim SC, Faissner A. Extracellular matrix remodeling during retinal development. Exp Eye Res 2015; 133:132-40. [DOI: 10.1016/j.exer.2014.07.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/30/2014] [Accepted: 07/01/2014] [Indexed: 10/25/2022]
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16
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Reingruber J, Holcman D. Computational and mathematical methods for morphogenetic gradient analysis, boundary formation and axonal targeting. Semin Cell Dev Biol 2014; 35:189-202. [PMID: 25194659 DOI: 10.1016/j.semcdb.2014.08.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 08/21/2014] [Accepted: 08/26/2014] [Indexed: 10/24/2022]
Abstract
Morphogenesis and axonal targeting are key processes during development that depend on complex interactions at molecular, cellular and tissue level. Mathematical modeling is essential to bridge this multi-scale gap in order to understand how the emergence of large structures is controlled at molecular level by interactions between various signaling pathways. We summarize mathematical modeling and computational methods for time evolution and precision of morphogenetic gradient formation. We discuss tissue patterning and the formation of borders between regions labeled by different morphogens. Finally, we review models and algorithms that reveal the interplay between morphogenetic gradients and patterned activity for axonal pathfinding and the generation of the retinotopic map in the visual system.
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Affiliation(s)
- Jürgen Reingruber
- Group of Computational Biology and Applied Mathematics, Institute of Biology (IBENS), CNRS INSERM 1024, Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France.
| | - David Holcman
- Group of Computational Biology and Applied Mathematics, Institute of Biology (IBENS), CNRS INSERM 1024, Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France.
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17
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Sharma A, LeVaillant CJ, Plant GW, Harvey AR. Changes in expression of Class 3 Semaphorins and their receptors during development of the rat retina and superior colliculus. BMC DEVELOPMENTAL BIOLOGY 2014; 14:34. [PMID: 25062604 PMCID: PMC4121511 DOI: 10.1186/s12861-014-0034-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/15/2014] [Indexed: 12/28/2022]
Abstract
Background Members of the Semaphorin 3 family (Sema3s) influence the development of the central nervous system, and some are implicated in regulating aspects of visual system development. However, we lack information about the timing of expression of the Sema3s with respect to different developmental epochs in the mammalian visual system. In this time-course study in the rat, we document for the first time changes in the expression of RNAs for the majority of Class 3 Semaphorins (Sema3s) and their receptor components during the development of the rat retina and superior colliculus (SC). Results During retinal development, transcript levels changed for all of the Sema3s examined, as well as Nrp2, Plxna2, Plxna3, and Plxna4a. In the SC there were also changes in transcript levels for all Sema3s tested, as well as Nrp1, Nrp2, Plxna1, Plxna2, Plxna3, and Plxna4a. These changes correlate with well-established epochs, and our data suggest that the Sema3s could influence retinal ganglion cell (RGC) apoptosis, patterning and connectivity in the maturing retina and SC, and perhaps guidance of RGC and cortical axons in the SC. Functionally we found that SEMA3A, SEMA3C, SEMA3E, and SEMA3F proteins collapsed purified postnatal day 1 RGC growth cones in vitro. Significantly this is a developmental stage when RGCs are growing into and within the SC and are exposed to Sema3 ligands. Conclusion These new data describing the overall temporal regulation of Sema3 expression in the rat retina and SC provide a platform for further work characterising the functional impact of these proteins on the development and maturation of mammalian visual pathways.
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Affiliation(s)
- Anil Sharma
- School of Anatomy, Physiology and Human Biology, The University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
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18
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Stettler O, Moya KL. Distinct roles of homeoproteins in brain topographic mapping and in neural circuit formation. Semin Cell Dev Biol 2014; 35:165-72. [PMID: 25042849 DOI: 10.1016/j.semcdb.2014.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 07/07/2014] [Indexed: 01/02/2023]
Abstract
The construction of the brain is a highly regulated process, requiring coordination of various cellular and molecular mechanisms that together ensure the stability of the cerebrum architecture and functions. The mature brain is an organ that performs complex computational operations using specific sensory information from the outside world and this requires precise organization within sensory networks and a separation of sensory modalities during development. We review here the role of homeoproteins in the arealization of the brain according to sensorimotor functions, the micropartition of its cytoarchitecture, and the maturation of its sensory circuitry. One of the most interesting observation about homeoproteins in recent years concerns their ability to act both in a cell-autonomous and non-cell-autonomous manner. The highlights in the present review collectively show how these two modes of action of homeoproteins confer various functions in shaping cortical maps.
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Affiliation(s)
- Olivier Stettler
- Laboratoire CRRET EAC 7149, Université Paris-Est Créteil, 61, Av. du Général de Gaulle, 94010 Créteil Cedex, France.
| | - Kenneth L Moya
- Collège de France, Center for Interdisciplinary Research in Biology, UMR CNRS 7241/INSERM U1050, 11 place Marcelin Berthelot, 75005 Paris, France; Labex Memolife, PSL Research University, France
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Joly S, Jordi N, Schwab ME, Pernet V. The Ephrin receptor EphA4 restricts axonal sprouting and enhances branching in the injured mouse optic nerve. Eur J Neurosci 2014; 40:3021-31. [DOI: 10.1111/ejn.12677] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 06/10/2014] [Accepted: 06/16/2014] [Indexed: 02/02/2023]
Affiliation(s)
- Sandrine Joly
- Brain Research Institute; University of Zurich; Winterthurerstrasse 190 Zurich CH-8057 Switzerland
- Department of Health Sciences and Technology; ETH Zurich; Zurich Switzerland
| | - Noémie Jordi
- Brain Research Institute; University of Zurich; Winterthurerstrasse 190 Zurich CH-8057 Switzerland
- Department of Health Sciences and Technology; ETH Zurich; Zurich Switzerland
| | - Martin E. Schwab
- Brain Research Institute; University of Zurich; Winterthurerstrasse 190 Zurich CH-8057 Switzerland
- Department of Health Sciences and Technology; ETH Zurich; Zurich Switzerland
| | - Vincent Pernet
- Brain Research Institute; University of Zurich; Winterthurerstrasse 190 Zurich CH-8057 Switzerland
- Department of Health Sciences and Technology; ETH Zurich; Zurich Switzerland
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20
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Carri NG, Bermúdez SN, Fiore L, Napoli JD, Scicolone G. Anaglyph of Retinal Stem Cells And Developing Axons: Selective Volume Enhancement In Microscopy Images. Anat Rec (Hoboken) 2014; 297:770-80. [DOI: 10.1002/ar.22889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 12/07/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Néstor Gabriel Carri
- Laboratorio de Biología Molecular del Desarrollo, lnstituto Multidisciplinario de Biología Celular; IMBICE La Plata Argentina
| | - Sebastián Noo Bermúdez
- Laboratorio de Biología Molecular del Desarrollo, lnstituto Multidisciplinario de Biología Celular; IMBICE La Plata Argentina
| | - Luciano Fiore
- Laboratorio de Neurobiologia del Desarrollo Instituto de Biología Celular y Neurosciencia “Prof. Eduardo De Robertis” (UBA-CONICET); Facultad de Medicina, Universidad de Buenos Aires; Ciudad Buenos Aires Argentina
| | - Jennifer Di Napoli
- Laboratorio de Neurobiologia del Desarrollo Instituto de Biología Celular y Neurosciencia “Prof. Eduardo De Robertis” (UBA-CONICET); Facultad de Medicina, Universidad de Buenos Aires; Ciudad Buenos Aires Argentina
| | - Gabriel Scicolone
- Laboratorio de Neurobiologia del Desarrollo Instituto de Biología Celular y Neurosciencia “Prof. Eduardo De Robertis” (UBA-CONICET); Facultad de Medicina, Universidad de Buenos Aires; Ciudad Buenos Aires Argentina
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Sfrp1a and Sfrp5 function as positive regulators of Wnt and BMP signaling during early retinal development. Dev Biol 2014; 388:192-204. [PMID: 24457098 DOI: 10.1016/j.ydbio.2014.01.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 12/16/2013] [Accepted: 01/13/2014] [Indexed: 01/08/2023]
Abstract
Axial patterning of the developing eye is critically important for proper axonal pathfinding as well as for key morphogenetic events, such as closure of the optic fissure. The dorsal retina is initially specified by the actions of Bone Morphogenetic Protein (BMP) signaling, with such identity subsequently maintained by the Wnt-β catenin pathway. Using zebrafish as a model system, we demonstrate that Secreted frizzled-related protein 1a (Sfrp1a) and Sfrp5 work cooperatively to pattern the retina along the dorso-ventral axis. Sfrp1a/5 depleted embryos display a reduction in dorsal marker gene expression that is consistent with defects in BMP- and Wnt-dependent dorsal retina identity. In accord with this finding, we observe a marked reduction in transgenic reporters of BMP and Wnt signaling within the dorsal retina of Sfrp1a/5 depleted embryos. In contrast to studies in which canonical Wnt signaling is blocked, we note an increase in BMP ligand expression in Sfrp1a/5 depleted embryos, a phenotype similar to that seen in embryos with inhibited BMP signaling. Overexpression of a low dose of sfrp5 mRNA causes an increase in dorsal retina marker gene expression. We propose a model in which Sfrp proteins function as facilitators of both BMP and Wnt signaling within the dorsal retina.
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22
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Prokosch V, Chiwitt C, Rose K, Thanos S. Deciphering proteins and their functions in the regenerating retina. Expert Rev Proteomics 2014; 7:775-95. [DOI: 10.1586/epr.10.47] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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23
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Teo L, Homman-Ludiye J, Rodger J, Bourne JA. Discrete ephrin-B1 expression by specific layers of the primate retinogeniculostriate system continues throughout postnatal and adult life. J Comp Neurol 2012; 520:2941-56. [PMID: 22778007 DOI: 10.1002/cne.23077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The molecular guidance cue ephrin-B1 has traditionally been associated with the early development of the visual system, encompassing retinocollicular mapping as well as development and maturation of synapses. Although little is known about its role in the visual system during the postnatal period and in adulthood, recent studies have demonstrated the expression of ephrin-B1 in the adult mouse brain, indicating a sustained role beyond early development. Therefore, we explored the spatiotemporal expression of ephrin-B1 in the postnatal and adult nonhuman primate visual system and demonstrated that a modulated expression continued following birth into adulthood in the lateral geniculate nucleus (LGN) and primary visual cortex (V1, striate cortex). This occurred in the layers involved in bidirectional geniculostriate communication: layers 3Bβ, 4, and 6 of V1 and the parvocellular (P) and magnocellular (M) layers of the LGN. Furthermore, discrete gradients between the ipsi- and contralateral inputs of the P and M layers of the LGN evolved between 1 month following birth and the start of the critical period (3 months), and continued into adulthood. We also detected the postsynaptic expression of ephrin-B1 by excitatory cells in adult LGN and V1 and a subset of interneurons in adult V1, suggestive of a more global rather than subtype-specific role. Together these results suggest a possible role for ephrin-B1 in the maturation of the primate retinogeniculostriate pathway throughout postnatal life, extending into adulthood.
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Affiliation(s)
- Leon Teo
- Australian Regenerative Medicine Institute, Monash University Clayton, Victoria, 3800, Australia
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Gregory-Evans CY, Wallace VA, Gregory-Evans K. Gene networks: dissecting pathways in retinal development and disease. Prog Retin Eye Res 2012; 33:40-66. [PMID: 23128416 DOI: 10.1016/j.preteyeres.2012.10.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 10/18/2012] [Accepted: 10/19/2012] [Indexed: 01/21/2023]
Abstract
During retinal neurogenesis, diverse cellular subtypes originate from multipotent neural progenitors in a spatiotemporal order leading to a highly specialized laminar structure combined with a distinct mosaic architecture. This is driven by the combinatorial action of transcription factors and signaling molecules which specify cell fate and differentiation. The emerging approach of gene network analysis has allowed a better understanding of the functional relationships between genes expressed in the developing retina. For instance, these gene networks have identified transcriptional hubs that have revealed potential targets and pathways for the development of therapeutic options for retinal diseases. Much of the current knowledge has been informed by targeted gene deletion experiments and gain-of-functional analysis. In this review we will provide an update on retinal development gene networks and address the wider implications for future disease therapeutics.
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Affiliation(s)
- Cheryl Y Gregory-Evans
- Department of Ophthalmology, University of British Columbia, Vancouver, BC V5Z 3N9, Canada.
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Coulthard MG, Morgan M, Woodruff TM, Arumugam TV, Taylor SM, Carpenter TC, Lackmann M, Boyd AW. Eph/Ephrin signaling in injury and inflammation. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 181:1493-503. [PMID: 23021982 DOI: 10.1016/j.ajpath.2012.06.043] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 06/28/2012] [Indexed: 12/20/2022]
Abstract
The Eph/ephrin receptor-ligand system plays an important role in embryogenesis and adult life, principally by influencing cell behavior through signaling pathways, resulting in modification of the cell cytoskeleton and cell adhesion. There are 10 EphA receptors, and six EphB receptors, distinguished on sequence difference and binding preferences, that interact with the six glycosylphosphatidylinositol-linked ephrin-A ligands and the three transmembrane ephrin-B ligands, respectively. The Eph/ephrin proteins, originally described as developmental regulators that are expressed at low levels postembryonically, are re-expressed after injury to the optic nerve, spinal cord, and brain in fish, amphibians, rodents, and humans. In rodent spinal cord injury, the up-regulation of EphA4 prevents recovery by inhibiting axons from crossing the injury site. Eph/ephrin proteins may be partly responsible for the phenotypic changes to the vascular endothelium in inflammation, which allows fluid and inflammatory cells to pass from the vascular space into the interstitial tissues. Specifically, EphA2/ephrin-A1 signaling in the lung may be responsible for pulmonary inflammation in acute lung injury. A role in T-cell maturation and chronic inflammation (heart failure, inflammatory bowel disease, and rheumatoid arthritis) is also reported. Although there remains much to learn about Eph/ephrin signaling in human disease, and specifically in injury and inflammation, this area of research raises the exciting prospect that novel therapies will be developed that precisely target these pathways.
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Affiliation(s)
- Mark G Coulthard
- Academic Discipline of Paediatrics and Child Health, University of Queensland, Royal Children's Hospital, Herston, Australia.
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26
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Ortalli AL, Fiore L, Di Napoli J, Rapacioli M, Salierno M, Etchenique R, Flores V, Sanchez V, Carri NG, Scicolone G. EphA3 expressed in the chicken tectum stimulates nasal retinal ganglion cell axon growth and is required for retinotectal topographic map formation. PLoS One 2012; 7:e38566. [PMID: 22685584 PMCID: PMC3369860 DOI: 10.1371/journal.pone.0038566] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 05/07/2012] [Indexed: 11/29/2022] Open
Abstract
Background Retinotopic projection onto the tectum/colliculus constitutes the most studied model of topographic mapping and Eph receptors and their ligands, the ephrins, are the best characterized molecular system involved in this process. Ephrin-As, expressed in an increasing rostro-caudal gradient in the tectum/colliculus, repel temporal retinal ganglion cell (RGC) axons from the caudal tectum and inhibit their branching posterior to their termination zones. However, there are conflicting data regarding the nature of the second force that guides nasal axons to invade and branch only in the caudal tectum/colliculus. The predominant model postulates that this second force is produced by a decreasing rostro-caudal gradient of EphA7 which repels nasal optic fibers and prevents their branching in the rostral tectum/colliculus. However, as optic fibers invade the tectum/colliculus growing throughout this gradient, this model cannot explain how the axons grow throughout this repellent molecule. Methodology/Principal Findings By using chicken retinal cultures we showed that EphA3 ectodomain stimulates nasal RGC axon growth in a concentration dependent way. Moreover, we showed that nasal axons choose growing on EphA3-expressing cells and that EphA3 diminishes the density of interstitial filopodia in nasal RGC axons. Accordingly, in vivo EphA3 ectodomain misexpression directs nasal optic fibers toward the caudal tectum preventing their branching in the rostral tectum. Conclusions We demonstrated in vitro and in vivo that EphA3 ectodomain (which is expressed in a decreasing rostro-caudal gradient in the tectum) is necessary for topographic mapping by stimulating the nasal axon growth toward the caudal tectum and inhibiting their branching in the rostral tectum. Furthermore, the ability of EphA3 of stimulating axon growth allows understanding how optic fibers invade the tectum growing throughout this molecular gradient. Therefore, opposing tectal gradients of repellent ephrin-As and of axon growth stimulating EphA3 complement each other to map optic fibers along the rostro-caudal tectal axis.
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Affiliation(s)
- Ana Laura Ortalli
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Luciano Fiore
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Jennifer Di Napoli
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Melina Rapacioli
- Interdisciplinary Group in Theoretical Biology, Department of Bioestructural Sciences, Favaloro University, Buenos Aires, Argentina
| | - Marcelo Salierno
- Department of Inorganic, Analytical and Physical Chemistry (INQUIMAE), Faculty of Exact and Natural Sciences, University of Buenos Aires, Buenos Aires, Argentina
| | - Roberto Etchenique
- Department of Inorganic, Analytical and Physical Chemistry (INQUIMAE), Faculty of Exact and Natural Sciences, University of Buenos Aires, Buenos Aires, Argentina
| | - Vladimir Flores
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
- Interdisciplinary Group in Theoretical Biology, Department of Bioestructural Sciences, Favaloro University, Buenos Aires, Argentina
| | - Viviana Sanchez
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | | | - Gabriel Scicolone
- Laboratory of Developmental Neurobiology, Institute of Cell Biology and Neurosciences “Prof. E. De Robertis” (UBA-CONICET), School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
- * E-mail:
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27
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Eyes on DNA methylation: current evidence for DNA methylation in ocular development and disease. J Ocul Biol Dis Infor 2012; 4:95-103. [PMID: 23538551 DOI: 10.1007/s12177-012-9078-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 03/05/2012] [Indexed: 12/20/2022] Open
Abstract
Epigenetic modulation of chromatin states constitutes a vital component of the cellular repertoire of transcriptional regulatory mechanisms. The development of new technologies capable of generating genome-wide maps of chromatin modifications has re-energized the field. We are now poised to determine how species- and tissue-specific patterns of DNA methylation, in concert with other chromatin modifications, function to establish and maintain cell- and tissue-specific patterns of gene expression during normal development, cellular differentiation, and disease. This review addresses our current understanding of the major mechanisms and function of DNA methylation in vertebrates with a historical perspective and an emphasis on what is known about DNA methylation in eye development and disease.
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Hruska M, Dalva MB. Ephrin regulation of synapse formation, function and plasticity. Mol Cell Neurosci 2012; 50:35-44. [PMID: 22449939 DOI: 10.1016/j.mcn.2012.03.004] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 03/08/2012] [Indexed: 10/28/2022] Open
Abstract
Synapses enable the transmission of information within neural circuits and allow the brain to change in response to experience. During the last decade numerous proteins that can induce synapse formation have been identified. Many of these synaptic inducers rely on trans-synaptic cell-cell interactions to generate functional contacts. Moreover, evidence now suggests that the same proteins that function early in development to regulate synapse formation may help to maintain and/or regulate the function and plasticity of mature synapses. One set of receptors and ligands that appear to impact both the development and the mature function of synapses are Eph receptors (erythropoietin-producing human hepatocellular carcinoma cell line) and their surface associated ligands, ephrins (Eph family receptor interacting proteins). Ephs can initiate new synaptic contacts, recruit and stabilize glutamate receptors at nascent synapses and regulate dendritic spine morphology. Recent evidence demonstrates that ephrin ligands also play major roles at synapses. Activation of ephrins by Eph receptors can induce synapse formation and spine morphogenesis, whereas in the mature nervous system ephrin signaling modulates synaptic function and long-term changes in synaptic strength. In this review we will summarize the recent progress in understanding the role of ephrins in presynaptic and postsynaptic differentiation, and synapse development, function and plasticity.
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Affiliation(s)
- Martin Hruska
- Department of Neuroscience and the Farber Institute, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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29
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Garrett AM, Burgess RW. Candidate molecular mechanisms for establishing cell identity in the developing retina. Dev Neurobiol 2012; 71:1258-72. [PMID: 21630473 DOI: 10.1002/dneu.20926] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the developing nervous system, individual neurons must occupy appropriate positions within circuits. This requires that these neurons recognize and form connections with specific pre- and postsynaptic partners. Cellular recognition is also required for the spacing of cell bodies and the arborization of dendrites, factors that determine the inputs onto a given neuron. These issues are particularly evident in the retina, where different types of neurons are evenly spaced relative to other cells of the same type. This establishes a reiterated columnar circuitry resembling the insect retina. Establishing these mosaic patterns requires that cells of a given type (homotypic cells) be able to sense their neighbors. Therefore, both synaptic specificity and mosaic spacing require cellular identifiers. In synaptic specificity, recognition often occurs between different types of cells in a pre- and postsynaptic pairing. In mosaic spacing, recognition is often occurring between different cells of the same type, orhomotypic self-recognition. Dendritic arborization can require recognition of different neurites of the same cell, or isoneuronal self-recognition. The retina is an extremely amenable system for studying the molecular identifiers that drive these various forms of recognition. The different neuronal types in the retina are well defined, and the genetic tools for marking cell types are increasingly available. In this review we will summarize retinal anatomy and describe cell types in the retina and how they are defined. We will then describe the requirements of a recognition code and discuss newly emerging candidate molecular mechanisms for recognition that may meet these requirements.
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Stettler O, Joshi RL, Wizenmann A, Reingruber J, Holcman D, Bouillot C, Castagner F, Prochiantz A, Moya KL. Engrailed homeoprotein recruits the adenosine A1 receptor to potentiate ephrin A5 function in retinal growth cones. Development 2012; 139:215-24. [PMID: 22147955 DOI: 10.1242/dev.063875] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Engrailed 1 and engrailed 2 homeoprotein transcription factors (collectively Engrailed) display graded expression in the chick optic tectum where they participate in retino-tectal patterning. In vitro, extracellular Engrailed guides retinal ganglion cell (RGC) axons and synergises with ephrin A5 to provoke the collapse of temporal growth cones. In vivo disruption of endogenous extracellular Engrailed leads to misrouting of RGC axons. Here we characterise the signalling pathway of extracellular Engrailed. Our results show that Engrailed/ephrin A5 synergy in growth cone collapse involves adenosine A1 receptor activation after Engrailed-dependent ATP synthesis, followed by ATP secretion and hydrolysis to adenosine. This is, to our knowledge, the first evidence for a role of the adenosine A1 receptor in axon guidance. Based on these results, together with higher expression of the adenosine A1 receptor in temporal than nasal growth cones, we propose a computational model that illustrates how the interaction between Engrailed, ephrin A5 and adenosine could increase the precision of the retinal projection map.
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Affiliation(s)
- Olivier Stettler
- CNRS Unité mixte de Recherche 7241/INSERM U1050, Equipe FRM, Center for Interdisciplinary Research in Biology, Collège de France, 11, place Marcelin Berthelot, 75005 Paris, France
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Sloniowski S, Ethell IM. Looking forward to EphB signaling in synapses. Semin Cell Dev Biol 2011; 23:75-82. [PMID: 22040917 DOI: 10.1016/j.semcdb.2011.10.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 10/17/2011] [Indexed: 11/24/2022]
Abstract
Eph receptors and their ligands ephrins comprise a complex signaling system with diverse functions that span a wide range of tissues and developmental stages. The variety of Eph receptor functions stems from their ability to mediate bidirectional signaling through trans-cellular Eph/ephrin interactions. Initially thought to act by directing repulsion between cells, Ephs have also been demonstrated to induce and maintain cell adhesive responses at excitatory synapses in the central nervous system. EphB receptors are essential to the development and maintenance of dendritic spines, which accommodate the postsynaptic sites of most glutamatergic excitatory synapses in the brain. Functions of EphB receptors are not limited to control of the actin cytoskeleton in dendritic spines, as EphB receptors are also involved in the formation of functional synaptic specializations through the regulation of glutamate receptor trafficking and functions. In addition, EphB receptors have recently been linked to the pathophysiology of Alzheimer's disease and neuropathic pain, thus becoming promising targets for therapeutic interventions. In this review, we discuss recent findings on EphB receptor functions in synapses, as well as the mechanisms of bidirectional trans-synaptic ephrin-B/EphB receptor signaling that shape dendritic spines and influence post-synaptic differentiation.
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Affiliation(s)
- Slawomir Sloniowski
- Division of Biomedical Sciences and Graduate Program in Neuroscience, University of California Riverside, 900 University Ave., Riverside, CA 92521, USA
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Chan KC, Cheng JS, Fan S, Zhou IY, Yang J, Wu EX. In vivo evaluation of retinal and callosal projections in early postnatal development and plasticity using manganese-enhanced MRI and diffusion tensor imaging. Neuroimage 2011; 59:2274-83. [PMID: 21985904 DOI: 10.1016/j.neuroimage.2011.09.055] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 08/22/2011] [Accepted: 09/22/2011] [Indexed: 12/14/2022] Open
Abstract
The rodents are an excellent model for understanding the development and plasticity of the visual system. In this study, we explored the feasibility of Mn-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) at 7 T for in vivo and longitudinal assessments of the retinal and callosal pathways in normal neonatal rodent brains and after early postnatal visual impairments. Along the retinal pathways, unilateral intravitreal Mn2+ injection resulted in Mn2+ uptake and transport in normal neonatal visual brains at postnatal days (P) 1, 5 and 10 with faster Mn2+ clearance than the adult brains at P60. The reorganization of retinocollicular projections was also detected by significant Mn2+ enhancement by 2%-10% in the ipsilateral superior colliculus (SC) of normal neonatal rats, normal adult mice and adult rats after neonatal monocular enucleation (ME) but not in normal adult rats or adult rats after monocular deprivation (MD). DTI showed a significantly higher fractional anisotropy (FA) by 21% in the optic nerve projected from the remaining eye of ME rats compared to normal rats at 6 weeks old, likely as a result of the retention of axons from the ipsilaterally uncrossed retinal ganglion cells, whereas the anterior and posterior retinal pathways projected from the enucleated or deprived eyes possessed lower FA after neonatal binocular enucleation (BE), ME and MD by 22%-56%, 18%-46% and 11%-15% respectively compared to normal rats, indicative of neurodegeneration or immaturity of white matter tracts. Along the visual callosal pathways, intracortical Mn2+ injection to the visual cortex of BE rats enhanced a larger projection volume by about 74% in the V1/V2 transition zone of the contralateral hemisphere compared to normal rats, without apparent DTI parametric changes in the splenium of corpus callosum. This suggested an adaptive change in interhemispheric connections and spatial specificity in the visual cortex upon early blindness. The results of this study may help determine the mechanisms of axonal uptake and transport, microstructural reorganization and functional activities in the living visual brains during development, diseases, plasticity and early interventions in a global and longitudinal setting.
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Affiliation(s)
- Kevin C Chan
- Laboratory of Biomedical Imaging and Signal Processing, Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Pathway-specific engagement of ephrinA5-EphA4/EphA5 system of the substantia nigra pars reticulata in cocaine-induced responses. Proc Natl Acad Sci U S A 2011; 108:9981-6. [PMID: 21628570 DOI: 10.1073/pnas.1107592108] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The nucleus accumbens (NAc) serves as a key neural substrate that controls acute and adaptive behavioral responses to cocaine administration. In this circuit, inputs from the NAc are transmitted through two parallel pathways, named the direct and indirect pathways, and converge at the substantia nigra pars reticulata (SNr). Our previous study using reversible neurotransmission blocking (RNB) of each pathway revealed that the dual stimulation of the SNr by both pathways is necessary for the acute response, but that the direct pathway predominantly controls the adaptive response to repeated cocaine administration. This study aimed at exploring the pathway-specific mechanism of cocaine actions at the convergent SNr. We examined a genome-wide expression profile of the SNr of three types of experimental mice: the direct pathway-blocked D-RNB mice, the indirect pathway-blocked I-RNB mice, and wild-type mice. We identified the up-regulation of ephrinA5, EphA4, and EphA5 specific to D-RNB mice during both acute and adaptive responses to cocaine administration. The activation by EphA4 and EphA5 in the SNr of wild-type mice by use of the immunoadhesin technique suppressed the adaptive response to repeated cocaine administration. Furthermore, cocaine exposure stimulated the phosphorylation of Erk1/2 in ephrinA5-expressing SNr cells in a direct pathway-dependent manner. The results have demonstrated that the ephrinA5-EphA4/EphA5 system plays an important role in the direct pathway-dependent regulation of the SNr in both acute and adaptive cocaine responses and would provide valuable therapeutic targets of cocaine addiction.
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San Miguel S, Serrano MJ, Sachar A, Henkemeyer M, Svoboda KKH, Benson MD. Ephrin reverse signaling controls palate fusion via a PI3 kinase-dependent mechanism. Dev Dyn 2011; 240:357-64. [PMID: 21246652 DOI: 10.1002/dvdy.22546] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Secondary palate fusion requires adhesion and epithelial-to-mesenchymal transition (EMT) of the epithelial layers on opposing palatal shelves. This EMT requires transforming growth factor β3 (TGFβ3), and its failure results in cleft palate. Ephrins, and their receptors, the Ephs, are responsible for migration, adhesion, and midline closure events throughout development. Ephrins can also act as signal-transducing receptors in these processes, with the Ephs serving as ligands (termed "reverse" signaling). We found that activation of ephrin reverse signaling in chicken palates induced fusion in the absence of TGFβ3, and that PI3K inhibition abrogated this effect. Further, blockage of reverse signaling inhibited TGFβ3-induced fusion in the chicken and natural fusion in the mouse. Thus, ephrin reverse signaling is necessary and sufficient to induce palate fusion independent of TGFβ3. These data describe both a novel role for ephrins in palate morphogenesis, and a previously unknown mechanism of ephrin signaling.
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Affiliation(s)
- Symone San Miguel
- Department of Biomedical Sciences, Texas A&M Health Science Center Baylor College of Dentistry, Dallas, Texas, USA
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35
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Simpson HD, Goodhill GJ. A simple model can unify a broad range of phenomena in retinotectal map development. BIOLOGICAL CYBERNETICS 2011; 104:9-29. [PMID: 21340602 DOI: 10.1007/s00422-011-0417-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Accepted: 11/24/2010] [Indexed: 05/30/2023]
Abstract
A paradigm model system for studying the development of patterned connections in the nervous system is the topographic map formed by retinal axons in the optic tectum/superior colliculus. Starting in the 1970s, a series of computational models have been proposed to explain map development in both normal conditions, and perturbed conditions where the retina and/or tectum/superior colliculus are altered. This stands in contrast to more recent models that have often been simpler than older ones, and tend to address more limited data sets, but include more recent genetic manipulations. The original exploration of many of the early models was one-dimensional and limited by the computational resources of the time. This leaves open the ability of these early models to explain both map development in two dimensions, and the genetic manipulation data that have only appeared more recently. In this article, we show that a two-dimensional and updated version of the XBAM model (eXtended Branch Arrow Model), first proposed in 1982, reproduces a range of surgical map manipulations not yet demonstrated by more modern models. A systematic exploration of the parameter space of this model in two dimensions also reveals richer behavior than that apparent from the original one-dimensional versions. Furthermore, we show that including a specific type of axon-axon interaction can account for the map collapse recently observed when particular receptor levels are genetically manipulated in a subset of retinal ganglion cells. Together these results demonstrate that balancing multiple influences on map development seems to be necessary to explain many biological phenomena in retinotectal map formation, and suggest important constraints on the underlying biological variables.
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Affiliation(s)
- Hugh D Simpson
- Queensland Brain Institute, The University of Queensland, Brisbane, Australia.
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36
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Tsigankov D, Koulakov AA. Sperry versus Hebb: topographic mapping in Isl2/EphA3 mutant mice. BMC Neurosci 2010; 11:155. [PMID: 21190559 PMCID: PMC3019204 DOI: 10.1186/1471-2202-11-155] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 12/29/2010] [Indexed: 11/19/2022] Open
Abstract
Background In wild-type mice, axons of retinal ganglion cells establish topographically precise projection to the superior colliculus of the midbrain. This means that axons of neighboring retinal ganglion cells project to the proximal locations in the target. The precision of topographic projection is a result of combined effects of molecular labels, such as Eph receptors and ephrins, and correlated neural activity. In the Isl2/EphA3 mutant mice the expression levels of molecular labels are changed. As a result the topographic projection is rewired so that the neighborhood relationships between retinal cell axons are disrupted. Results Here we study the computational model for retinocollicular connectivity formation that combines the effects of molecular labels and correlated neural activity. We argue that the effects of correlated activity presenting themselves in the form of Hebbian learning rules can facilitate the restoration of the topographic connectivity even when the molecular labels carry conflicting instructions. This occurs because the correlations in electric activity carry information about retinal cells' origin that is independent on molecular labels. We argue therefore that partial restoration of the topographic property of the retinocollicular projection observed in Isl2/EphA3 heterozygous knockin mice may be explained by the effects of correlated neural activity. We address the maps observed in Isl2/EphA3 knockin/EphA4 knockout mice in which the levels of retinal labels are uniformly reduced. These maps can be explained by either the saturation of EphA receptor mapping leading to the relative signaling model or by the reverse signaling conveyed by ephrin-As expressed by retinal axons. Conclusion According to our model, experiments in Isl2/EphA3 knock-in mice test the interactions between effects of molecular labels and correlated activity during the development of neural connectivity. Correlated activity can partially restore topographic order even when molecular labels carry conflicting information.
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Affiliation(s)
- Dmitry Tsigankov
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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CHAN KEVINC, CHEUNG MATTHEWM, WU EDX. IN VIVOMULTIPARAMETRIC MAGNETIC RESONANCE IMAGING AND SPECTROSCOPY OF RODENT VISUAL SYSTEM. J Integr Neurosci 2010; 9:477-508. [DOI: 10.1142/s0219635210002524] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 11/04/2010] [Indexed: 01/27/2023] Open
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Petkova TD, Seigel GM, Otteson DC. A role for DNA methylation in regulation of EphA5 receptor expression in the mouse retina. Vision Res 2010; 51:260-8. [PMID: 20875442 DOI: 10.1016/j.visres.2010.09.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 09/16/2010] [Accepted: 09/17/2010] [Indexed: 01/15/2023]
Abstract
Understanding the mechanisms regulating expression of retinal ganglion cell (RGC) specific and axon-guidance genes during development and in retinal stem cells will be critical for successful optic nerve regeneration. Müller glia have some characteristics of retinal stem cells but in mammals have demonstrated limited potential to differentiate into RGCs. Chromatin remodeling through histone deacetylation and DNA methylation are a potential mechanism for silencing genes necessary for neuronal differentiation of glial cells. We investigated DNA methylation as a mechanism for regulating expression of mouse EphA5, one member of a large family of ephrin receptor genes that regulate patterning of the topographic connections of RGCs during visual system development. We analyzed spatial and age-related patterns of EphA5 promoter methylation by bisulfite sequencing and mRNA expression by quantitative RT-PCR in the mouse retina. The CpG island in the EphA5 promoter was hypomethylated in the retina and showed no change in overall methylation with age, despite a decline in EphA5 mRNA expression levels in the adult retina. In the nasal retina of post-natal day 0 mice, there was a modest, but statistically significant increase in methylation. Increased methylation corresponded with lower levels of receptor mRNA expression in the nasal retina. We cloned the EphA5 promoter and found that site-specific differences in methylation could preferentially activate or repress promoter activity in transient transfections of rat retinal progenitor cells (R28) using luciferase assays. In sphere cultures generated by EGF/FGF2 stimulation of conditionally immortalized mouse Müller glia (ImM10), EphA5 promoter was hypermethylated and EphA5 mRNA was not detected. Demethylation using 5-azadeoxycytidine (AzadC) resulted in a significant decrease of methylation of the EphA5 promoter and re-expression of the EphA5 mRNA. The inverse relationship between EphA5 promoter methylation and mRNA expression is consistent with a role for DNA methylation in modulating the spatial patterns of EphA5 gene expression in the retina and in silencing EphA5 expression in ImM10 cells. The robust up-regulation of EphA5 in ImM10 cells following demethylation suggests that modulation of chromatin structure may be a useful approach for promoting expression of silenced developmental genes and increasing the neurogenic potential of Müller glia.
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Affiliation(s)
- Tihomira D Petkova
- Department of Vision Science, College of Optometry, Houston, TX 77204-2020, USA.
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Erickson T, French CR, Waskiewicz AJ. Meis1 specifies positional information in the retina and tectum to organize the zebrafish visual system. Neural Dev 2010; 5:22. [PMID: 20809932 PMCID: PMC2939508 DOI: 10.1186/1749-8104-5-22] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Accepted: 09/01/2010] [Indexed: 01/17/2023] Open
Abstract
Background During visual system development, multiple signalling pathways cooperate to specify axial polarity within the retina and optic tectum. This information is required for the topographic mapping of retinal ganglion cell axons on the tectum. Meis1 is a TALE-class homeodomain transcription factor known to specify anterior-posterior identity in the hindbrain, but its role in visual system patterning has not been investigated. Results meis1 is expressed in both the presumptive retina and tectum. An analysis of retinal patterning reveals that Meis1 is required to correctly specify both dorsal-ventral and nasal-temporal identity in the zebrafish retina. Meis1-knockdown results in a loss of smad1 expression and an upregulation in follistatin expression, thereby causing lower levels of Bmp signalling and a partial ventralization of the retina. Additionally, Meis1-deficient embryos exhibit ectopic Fgf signalling in the developing retina and a corresponding loss of temporal identity. Meis1 also positively regulates ephrin gene expression in the tectum. Consistent with these patterning phenotypes, a knockdown of Meis1 ultimately results in retinotectal mapping defects. Conclusions In this work we describe a novel role for Meis1 in regulating Bmp signalling and in specifying temporal identity in the retina. By patterning both the retina and tectum, Meis1 plays an important role in establishing the retinotectal map and organizing the visual system.
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Affiliation(s)
- Timothy Erickson
- Department of Biological Sciences, University of Alberta, CW405, Biological Sciences Bldg, Edmonton T6G 2E9, Canada
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40
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Deschamps C, Morel M, Janet T, Page G, Jaber M, Gaillard A, Prestoz L. EphrinA5 protein distribution in the developing mouse brain. BMC Neurosci 2010; 11:105. [PMID: 20738842 PMCID: PMC2941684 DOI: 10.1186/1471-2202-11-105] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 08/25/2010] [Indexed: 12/22/2022] Open
Abstract
Background EphrinA5 is one of the best-studied members of the Eph-ephrin family of guidance molecules, known to be involved in brain developmental processes. Using in situ hybridization, ephrinA5 mRNA expression has been detected in the retinotectal, the thalamocortical, and the olfactory systems; however, no study focused on the distribution of the protein. Considering that this membrane-anchored molecule may act far from the neuron soma expressing the transcript, it is of a crucial interest to localize ephrinA5 protein to better understand its function. Results Using immunohistochemistry, we found that ephrinA5 protein is highly expressed in the developing mouse brain from E12.5 to E16.5. The olfactory bulb, the cortex, the striatum, the thalamus, and the colliculi showed high intensity of labelling, suggesting its implication in topographic mapping of olfactory, retinocollicular, thalamocortical, corticothalamic and mesostriatal systems. In the olfactory nerve, we found an early ephrinA5 protein expression at E12.5 suggesting its implication in the guidance of primary olfactory neurons into the olfactory bulb. In the thalamus, we detected a dynamic graduated protein expression, suggesting its role in the corticothalamic patterning, whereas ephrinA5 protein expression in the target region of mesencephalic dopaminergic neurones indicated its involvement in the mesostriatal topographic mapping. Following E16.5, the signal faded gradually and was barely detectable at P0, suggesting a main role for ephrinA5 in primary molecular events in topographic map formation. Conclusion Our work shows that ephrinA5 protein is expressed in restrictive regions of the developing mouse brain. This expression pattern points out the potential sites of action of this molecule in the olfactory, retinotectal, thalamocortical, corticothalamic and mesostriatal systems, during development. This study is essential to better understand the role of ephrinA5 during developmental topographic mapping of connections and to further characterise the mechanisms involved in pathway restoration following cell transplantation in the damaged brain.
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Affiliation(s)
- Claire Deschamps
- Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, CNRS, France
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Bourne JA. Unravelling the development of the visual cortex: implications for plasticity and repair. J Anat 2010; 217:449-68. [PMID: 20722872 DOI: 10.1111/j.1469-7580.2010.01275.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The visual cortex comprises over 50 areas in the human, each with a specified role and distinct physiology, connectivity and cellular morphology. How these individual areas emerge during development still remains something of a mystery and, although much attention has been paid to the initial stages of the development of the visual cortex, especially its lamination, very little is known about the mechanisms responsible for the arealization and functional organization of this region of the brain. In recent years we have started to discover that it is the interplay of intrinsic (molecular) and extrinsic (afferent connections) cues that are responsible for the maturation of individual areas, and that there is a spatiotemporal sequence in the maturation of the primary visual cortex (striate cortex, V1) and the multiple extrastriate/association areas. Studies in both humans and non-human primates have started to highlight the specific neural underpinnings responsible for the maturation of the visual cortex, and how experience-dependent plasticity and perturbations to the visual system can impact upon its normal development. Furthermore, damage to specific nuclei of the visual cortex, such as the primary visual cortex (V1), is a common occurrence as a result of a stroke, neurotrauma, disease or hypoxia in both neonates and adults alike. However, the consequences of a focal injury differ between the immature and adult brain, with the immature brain demonstrating a higher level of functional resilience. With better techniques for examining specific molecular and connectional changes, we are now starting to uncover the mechanisms responsible for the increased neural plasticity that leads to significant recovery following injury during this early phase of life. Further advances in our understanding of postnatal development/maturation and plasticity observed during early life could offer new strategies to improve outcomes by recapitulating aspects of the developmental program in the adult brain.
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Affiliation(s)
- James A Bourne
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria 3800, Australia.
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42
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Reese BE. Development of the retina and optic pathway. Vision Res 2010; 51:613-32. [PMID: 20647017 DOI: 10.1016/j.visres.2010.07.010] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 07/04/2010] [Accepted: 07/13/2010] [Indexed: 12/30/2022]
Abstract
Our understanding of the development of the retina and visual pathways has seen enormous advances during the past 25years. New imaging technologies, coupled with advances in molecular biology, have permitted a fuller appreciation of the histotypical events associated with proliferation, fate determination, migration, differentiation, pathway navigation, target innervation, synaptogenesis and cell death, and in many instances, in understanding the genetic, molecular, cellular and activity-dependent mechanisms underlying those developmental changes. The present review considers those advances associated with the lineal relationships between retinal nerve cells, the production of retinal nerve cell diversity, the migration, patterning and differentiation of different types of retinal nerve cells, the determinants of the decussation pattern at the optic chiasm, the formation of the retinotopic map, and the establishment of ocular domains within the thalamus.
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Affiliation(s)
- Benjamin E Reese
- Neuroscience Research Institute and Department of Psychology, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA.
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In vivo retinotopic mapping of superior colliculus using manganese-enhanced magnetic resonance imaging. Neuroimage 2010; 54:389-95. [PMID: 20633657 DOI: 10.1016/j.neuroimage.2010.07.015] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 05/27/2010] [Accepted: 07/06/2010] [Indexed: 11/24/2022] Open
Abstract
The superior colliculus (SC) is a dome-shaped subcortical laminar structure in the mammalian midbrain, whose superficial layers receive visual information from the retina in a topological order. Despite the increasing number of studies investigating retinotopic projection in visual brain development and disorders, in vivo, high-resolution 3D mapping of topographic organization in the subcortical visual nuclei has not yet been available. This study explores the capability of 3D manganese-enhanced MRI (MEMRI) at 200 μm isotropic resolution for in vivo retinotopic mapping of the rat SC upon partial transection of the intraorbital optic nerve. One day after intravitreal Mn(2+) injection into both eyes, animals with partial transection at the right superior intraorbital optic nerve in Group 1 (n=8) exhibited a significantly lower T1-weighted signal intensity in the lateral region of the left SC compared to the left medial SC and right control SC. Partial transection toward the temporal or nasal region of the right intraorbital optic nerve in Group 2 (n=7) led to T1-weighted hypointensity in the rostral or caudal region of the left SC, whereas a clear border was observed separating 2 halves of the left SC in all groups. Previous histological and electrophysiological studies showed that the retinal ganglion cell axons emanating from superior, inferior, nasal and temporal retina projected respectively to the contralateral lateral, medial, caudal and rostral SC in rodents. While this topological pattern is preserved in the intraorbital optic nerve, it was shown that partial transection of the superior intraorbital optic nerve led to primary injury predominantly in the superior but not inferior retina and optic nerve. The results of this study demonstrated the sensitivity of submillimeter-resolution MEMRI for in vivo, 3D mapping of the precise retinotopic projections in SC upon reduced anterograde axonal transport of Mn(2+) ions from localized regions of the anterior visual pathways to the subcortical midbrain nuclei. Future MEMRI studies are envisioned that measure the topographic changes in brain development, diseases, plasticity and regeneration therapies in a global and longitudinal setting.
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