1
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Tomar M, Beros J, Meloni B, Rodger J. Interactions between Guidance Cues and Neuronal Activity: Therapeutic Insights from Mouse Models. Int J Mol Sci 2023; 24:ijms24086966. [PMID: 37108129 PMCID: PMC10138948 DOI: 10.3390/ijms24086966] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 03/31/2023] [Accepted: 04/03/2023] [Indexed: 04/29/2023] Open
Abstract
Topographic mapping of neural circuits is fundamental in shaping the structural and functional organization of brain regions. This developmentally important process is crucial not only for the representation of different sensory inputs but also for their integration. Disruption of topographic organization has been associated with several neurodevelopmental disorders. The aim of this review is to highlight the mechanisms involved in creating and refining such well-defined maps in the brain with a focus on the Eph and ephrin families of axon guidance cues. We first describe the transgenic models where ephrin-A expression has been manipulated to understand the role of these guidance cues in defining topography in various sensory systems. We further describe the behavioral consequences of lacking ephrin-A guidance cues in these animal models. These studies have given us unexpected insight into how neuronal activity is equally important in refining neural circuits in different brain regions. We conclude the review by discussing studies that have used treatments such as repetitive transcranial magnetic stimulation (rTMS) to manipulate activity in the brain to compensate for the lack of guidance cues in ephrin-knockout animal models. We describe how rTMS could have therapeutic relevance in neurodevelopmental disorders with disrupted brain organization.
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Affiliation(s)
- Maitri Tomar
- School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia
- Perron Institute for Neurological and Translational Science, Nedlands, WA 6009, Australia
| | - Jamie Beros
- School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia
- Perron Institute for Neurological and Translational Science, Nedlands, WA 6009, Australia
| | - Bruno Meloni
- Perron Institute for Neurological and Translational Science, Nedlands, WA 6009, Australia
- Centre for Neuromuscular and Neurological Disorders, The University of Western Australia, Crawley, WA 6009, Australia
- Department of Neurosurgery, Sir Charles Gairdner Hospital, QEII Medical Centre, Nedlands, WA 6009, Australia
| | - Jennifer Rodger
- School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia
- Perron Institute for Neurological and Translational Science, Nedlands, WA 6009, Australia
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2
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Harding P, Toms M, Schiff E, Owen N, Bell S, Lloyd IC, Moosajee M. EPHA2 Segregates with Microphthalmia and Congenital Cataracts in Two Unrelated Families. Int J Mol Sci 2021; 22:2190. [PMID: 33671840 PMCID: PMC7926380 DOI: 10.3390/ijms22042190] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/12/2021] [Accepted: 02/18/2021] [Indexed: 02/07/2023] Open
Abstract
EPHA2 is a transmembrane tyrosine kinase receptor that, when disrupted, causes congenital and age-related cataracts. Cat-Map reports 22 pathogenic EPHA2 variants associated with congenital cataracts, variable microcornea, and lenticonus, but no previous association with microphthalmia (small, underdeveloped eye, ≥2 standard deviations below normal axial length). Microphthalmia arises from ocular maldevelopment with >90 monogenic causes, and can include a complex ocular phenotype. In this paper, we report two pathogenic EPHA2 variants in unrelated families presenting with bilateral microphthalmia and congenital cataracts. Whole genome sequencing through the 100,000 Genomes Project and cataract-related targeted gene panel testing identified autosomal dominant heterozygous mutations segregating with the disease: (i) missense c.1751C>T, p.(Pro584Leu) and (ii) splice site c.2826-9G>A. To functionally validate pathogenicity, morpholino knockdown of epha2a/epha2b in zebrafish resulted in significantly reduced eye size ± cataract formation. Misexpression of N-cadherin and retained fibre cell nuclei were observed in the developing lens of the epha2b knockdown morphant fish by 3 days post-fertilisation, which indicated a putative mechanism for microphthalmia pathogenesis through disruption of cadherin-mediated adherens junctions, preventing lens maturation and the critical signals stimulating eye growth. This study demonstrates a novel association of EPHA2 with microphthalmia, suggesting further analysis of pathogenic variants in unsolved microphthalmia cohorts may increase molecular diagnostic rates.
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Affiliation(s)
- Philippa Harding
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK; (P.H.); (M.T.); (N.O.)
| | - Maria Toms
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK; (P.H.); (M.T.); (N.O.)
- The Francis Crick Institute, London NW1 1AT, UK
| | - Elena Schiff
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (E.S.); (S.B.)
| | - Nicholas Owen
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK; (P.H.); (M.T.); (N.O.)
| | - Suzannah Bell
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (E.S.); (S.B.)
| | - Ian Christopher Lloyd
- Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK;
- Manchester Academic Health Sciences Centre, University of Manchester, Manchester, M13 9PT, UK
- Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
| | - Mariya Moosajee
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK; (P.H.); (M.T.); (N.O.)
- The Francis Crick Institute, London NW1 1AT, UK
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (E.S.); (S.B.)
- Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
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3
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Li M, Nishio SY, Naruse C, Riddell M, Sapski S, Katsuno T, Hikita T, Mizapourshafiyi F, Smith FM, Cooper LT, Lee MG, Asano M, Boettger T, Krueger M, Wietelmann A, Graumann J, Day BW, Boyd AW, Offermanns S, Kitajiri SI, Usami SI, Nakayama M. Digenic inheritance of mutations in EPHA2 and SLC26A4 in Pendred syndrome. Nat Commun 2020; 11:1343. [PMID: 32165640 PMCID: PMC7067772 DOI: 10.1038/s41467-020-15198-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/17/2020] [Indexed: 01/03/2023] Open
Abstract
Enlarged vestibular aqueduct (EVA) is one of the most commonly identified inner ear malformations in hearing loss patients including Pendred syndrome. While biallelic mutations of the SLC26A4 gene, encoding pendrin, causes non-syndromic hearing loss with EVA or Pendred syndrome, a considerable number of patients appear to carry mono-allelic mutation. This suggests faulty pendrin regulatory machinery results in hearing loss. Here we identify EPHA2 as another causative gene of Pendred syndrome with SLC26A4. EphA2 forms a protein complex with pendrin controlling pendrin localization, which is disrupted in some pathogenic forms of pendrin. Moreover, point mutations leading to amino acid substitution in the EPHA2 gene are identified from patients bearing mono-allelic mutation of SLC26A4. Ephrin-B2 binds to EphA2 triggering internalization with pendrin inducing EphA2 autophosphorylation weakly. The identified EphA2 mutants attenuate ephrin-B2- but not ephrin-A1-induced EphA2 internalization with pendrin. Our results uncover an unexpected role of the Eph/ephrin system in epithelial function. While biallelic mutations of the SLC26A4 gene cause non-syndromic hearing loss with enlarged vestibular aqueducts or Pendred syndrome, a considerable number of patients carry mono-allelic mutations. Here the authors identify EPHA2 as another causative gene of Pendred syndrome with SLC26A4.
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Affiliation(s)
- Mengnan Li
- Laboratory for Cell Polarity and Organogenesis, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.,DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
| | - Shin-Ya Nishio
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Chie Naruse
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Meghan Riddell
- Laboratory for Cell Polarity and Organogenesis, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Sabrina Sapski
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Tatsuya Katsuno
- Department of Otolaryngology - Head and Neck Surgery Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Takao Hikita
- Laboratory for Cell Polarity and Organogenesis, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Fatemeh Mizapourshafiyi
- Laboratory for Cell Polarity and Organogenesis, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.,DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
| | - Fiona M Smith
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Leanne T Cooper
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
| | - Masahide Asano
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Thomas Boettger
- Department of Cardiac Development and Remodelling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Marcus Krueger
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Astrid Wietelmann
- MRI and µCT Service Group, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Johannes Graumann
- Scientific Service Group Biomolecular Mass Spectrometry Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.,German Centre for Cardiovascular Research (DZHK), Partner Site - Rhine-Main, Berlin, Germany
| | - Bryan W Day
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Andrew W Boyd
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Stefan Offermanns
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Shin-Ichiro Kitajiri
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Shin-Ichi Usami
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Masanori Nakayama
- Laboratory for Cell Polarity and Organogenesis, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany. .,DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany. .,Kumamoto University International Research Center for Medical Scinece, Kumamoto, Japan.
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4
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Sculpting the labyrinth: Morphogenesis of the developing inner ear. Semin Cell Dev Biol 2017; 65:47-59. [DOI: 10.1016/j.semcdb.2016.09.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/26/2016] [Accepted: 09/25/2016] [Indexed: 01/23/2023]
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5
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Kim YJ, Ibrahim LA, Wang SZ, Yuan W, Evgrafov OV, Knowles JA, Wang K, Tao HW, Zhang LI. EphA7 regulates spiral ganglion innervation of cochlear hair cells. Dev Neurobiol 2015; 76:452-69. [PMID: 26178595 DOI: 10.1002/dneu.22326] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 06/10/2015] [Accepted: 07/14/2015] [Indexed: 01/11/2023]
Abstract
During the development of periphery auditory circuitry, spiral ganglion neurons (SGNs) form a spatially precise pattern of innervation of cochlear hair cells (HCs), which is an essential structural foundation for central auditory processing. However, molecular mechanisms underlying the developmental formation of this precise innervation pattern remain not well understood. Here, we specifically examined the involvement of Eph family members in cochlear development. By performing RNA-sequencing for different types of cochlear cell, in situ hybridization, and immunohistochemistry, we found that EphA7 was strongly expressed in a large subset of SGNs. In EphA7 deletion mice, there was a reduction in the number of inner radial bundles originating from SGNs and projecting to HCs as well as in the number of ribbon synapses on inner hair cells (IHCs), as compared with wild-type or heterozygous mutant mice, attributable to fewer type I afferent fibers. The overall activity of the auditory nerve in EphA7 deletion mice was also reduced, although there was no significant change in the hearing intensity threshold. In vitro analysis further suggested that the reduced innervation of HCs by SGNs could be attributed to a role of EphA7 in regulating outgrowth of SGN neurites as knocking down EphA7 in SGNs resulted in diminished SGN fibers. In addition, suppressing the activity of ERK1/2, a potential downstream target of EphA7 signaling, either with specific inhibitors in cultured explants or by knocking out Prkg1, also resulted in reduced SGN fibers. Together, our results suggest that EphA7 plays an important role in the developmental formation of cochlear innervation pattern through controlling SGN fiber ontogeny. Such regulation may contribute to the salience level of auditory signals presented to the central auditory system.
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Affiliation(s)
- Young J Kim
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Neuroscience Graduate Program, University Of Southern California, Los Angeles, California
| | - Leena A Ibrahim
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Neuroscience Graduate Program, University Of Southern California, Los Angeles, California
| | - Sheng-Zhi Wang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033
| | - Wei Yuan
- Department of Otolaryngology of Southwest Hospital, Third Military Medical University, Chongqing, 400038, China
| | - Oleg V Evgrafov
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Department of Psychiatry, Keck School Of Medicine, University Of Southern California, Los Angeles, California
| | - James A Knowles
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Department of Psychiatry, Keck School Of Medicine, University Of Southern California, Los Angeles, California
| | - Kai Wang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Department of Psychiatry, Keck School Of Medicine, University Of Southern California, Los Angeles, California
| | - Huizhong W Tao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Department of Cell And Neurobiology, Keck School Of Medicine, University Of Southern California, Los Angeles, California
| | - Li I Zhang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University Of Southern California, Los Angeles, California, 90033.,Department of Physiology and Biophysics, Keck School Of Medicine, University Of Southern California, Los Angeles, California
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6
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Brown AS, Rakowiecki SM, Li JYH, Epstein DJ. The cochlear sensory epithelium derives from Wnt responsive cells in the dorsomedial otic cup. Dev Biol 2015; 399:177-187. [PMID: 25592224 DOI: 10.1016/j.ydbio.2015.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 12/11/2014] [Accepted: 01/02/2015] [Indexed: 02/07/2023]
Abstract
Wnt1 and Wnt3a secreted from the dorsal neural tube were previously shown to regulate a gene expression program in the dorsal otic vesicle that is necessary for vestibular morphogenesis (Riccomagno et al., 2005. Genes Dev. 19, 1612-1623). Unexpectedly, Wnt1(-/-); Wnt3a(-/-) embryos also displayed a pronounced defect in the outgrowth of the ventrally derived cochlear duct. To determine how Wnt signaling in the dorsal otocyst contributes to cochlear development we performed a series of genetic fate mapping experiments using two independent Wnt responsive driver strains (TopCreER and Gbx2(CreER)) that when crossed to inducible responder lines (Rosa(lacZ) or Rosa(zsGreen)) permanently labeled dorsomedial otic progenitors and their derivatives. Tamoxifen time course experiments revealed that most vestibular structures showed some degree of labeling when recombination was induced between E7.75 and E12.5, consistent with continuous Wnt signaling activity in this tissue. Remarkably, a population of Wnt responsive cells in the dorsal otocyst was also found to contribute to the sensory epithelium of the cochlear duct, including auditory hair and support cells. Similar results were observed with both TopCreER and Gbx2(CreER) strains. The ventral displacement of Wnt responsive cells followed a spatiotemporal sequence that initiated in the anterior otic cup at, or immediately prior to, the 17-somite stage (E9) and then spread progressively to the posterior pole of the otic vesicle by the 25-somite stage (E9.5). These lineage-tracing experiments identify the earliest known origin of auditory sensory progenitors within a population of Wnt responsive cells in the dorsomedial otic cup.
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Affiliation(s)
- Alexander S Brown
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, 415 Curie Blvd, Philadelphia, PA 19104, USA
| | - Staci M Rakowiecki
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, 415 Curie Blvd, Philadelphia, PA 19104, USA
| | - James Y H Li
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06030-6403, USA
| | - Douglas J Epstein
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, 415 Curie Blvd, Philadelphia, PA 19104, USA.
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7
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Yates N, Robertson D, Martin-Iverson M, Rodger J. Auditory brainstem responses of ephrin-A2, ephrin-A5(-/-) and ephrin-A2A5(-/-) mice. Audiol Neurootol 2014; 19:115-26. [PMID: 24457350 DOI: 10.1159/000357029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 10/30/2013] [Indexed: 01/04/2023] Open
Abstract
Eph receptors and ephrin ligands are large families of cell surface proteins which have established roles in axonal growth and guidance. These are well characterized in the visual and somatosensory systems but are less well documented in the auditory pathway. We examined the possible functional role of two ephrin genes (ephrin-A2 and ephrin-A5) in the auditory system by measuring auditory brainstem responses (ABR) to tone bursts from 6 to 30 kHz in ephrin-A2(-/-), ephrin-A5(-/-) and ephrin-A2A5(-/-) (knockout) mice. At high frequencies, the ephrin-A2A5(-/-) mice exhibited thresholds that were significantly lower than in wild-type mice by approximately 20 dB, suggesting ephrin-A2 and ephrin-A5 may have frequency-specific effects on the auditory system. There were also alterations in ABR wave peak amplitudes that were specific to each mouse strain which suggested both peripheral and central involvement of EphA-ephrin-A signalling in auditory function.
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Affiliation(s)
- Nathanael Yates
- School of Animal Biology, University of Western Australia, Crawley, W.A., Australia
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8
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Lassiter RNT, Stark MR, Zhao T, Zhou CJ. Signaling mechanisms controlling cranial placode neurogenesis and delamination. Dev Biol 2013; 389:39-49. [PMID: 24315854 DOI: 10.1016/j.ydbio.2013.11.025] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 11/22/2013] [Accepted: 11/23/2013] [Indexed: 01/17/2023]
Abstract
The neurogenic cranial placodes are a unique transient epithelial niche of neural progenitor cells that give rise to multiple derivatives of the peripheral nervous system, particularly, the sensory neurons. Placode neurogenesis occurs throughout an extended period of time with epithelial cells continually recruited as neural progenitor cells. Sensory neuron development in the trigeminal, epibranchial, otic, and olfactory placodes coincides with detachment of these neuroblasts from the encompassing epithelial sheet, leading to delamination and ingression into the mesenchyme where they continue to differentiate as neurons. Multiple signaling pathways are known to direct placodal development. This review defines the signaling pathways working at the finite spatiotemporal period when neuronal selection within the placodes occurs, and neuroblasts concomitantly delaminate from the epithelium. Examining neurogenesis and delamination after initial placodal patterning and specification has revealed a common trend throughout the neurogenic placodes, which suggests that both activated FGF and attenuated Notch signaling activities are required for neurogenesis and changes in epithelial cell adhesion leading to delamination. We also address the varying roles of other pathways such as the Wnt and BMP signaling families during sensory neurogenesis and neuroblast delamination in the differing placodes.
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Affiliation(s)
- Rhonda N T Lassiter
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children-Northern California, CA 95817, USA; Department of Cell Biology and Human Anatomy, University of California Davis, School of Medicine, Sacramento, CA 95817, USA.
| | - Michael R Stark
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA.
| | - Tianyu Zhao
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children-Northern California, CA 95817, USA; Department of Cell Biology and Human Anatomy, University of California Davis, School of Medicine, Sacramento, CA 95817, USA
| | - Chengji J Zhou
- Institute for Pediatric Regenerative Medicine at Shriners Hospitals for Children-Northern California, CA 95817, USA; Department of Cell Biology and Human Anatomy, University of California Davis, School of Medicine, Sacramento, CA 95817, USA; Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Sacramento, CA 95817, USA.
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9
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Allen-Sharpley MR, Tjia M, Cramer KS. Differential roles for EphA and EphB signaling in segregation and patterning of central vestibulocochlear nerve projections. PLoS One 2013; 8:e78658. [PMID: 24130906 PMCID: PMC3795076 DOI: 10.1371/journal.pone.0078658] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 09/13/2013] [Indexed: 11/18/2022] Open
Abstract
Auditory and vestibular afferents enter the brainstem through the VIIIth cranial nerve and find targets in distinct brain regions. We previously reported that the axon guidance molecules EphA4 and EphB2 have largely complementary expression patterns in the developing avian VIIIth nerve. Here, we tested whether inhibition of Eph signaling alters central targeting of VIIIth nerve axons. We first identified the central compartments through which auditory and vestibular axons travel. We then manipulated Eph-ephrin signaling using pharmacological inhibition of Eph receptors and in ovo electroporation to misexpress EphA4 and EphB2. Anterograde labeling of auditory afferents showed that inhibition of Eph signaling did not misroute axons to non-auditory target regions. Similarly, we did not find vestibular axons within auditory projection regions. However, we found that pharmacologic inhibition of Eph receptors reduced the volume of the vestibular projection compartment. Inhibition of EphB signaling alone did not affect auditory or vestibular central projection volumes, but it significantly increased the area of the auditory sensory epithelium. Misexpression of EphA4 and EphB2 in VIIIth nerve axons resulted in a significant shift of dorsoventral spacing between the axon tracts, suggesting a cell-autonomous role for the partitioning of projection areas along this axis. Cochlear ganglion volumes did not differ among treatment groups, indicating the changes seen were not due to a gain or loss of cochlear ganglion cells. These results suggest that Eph-ephrin signaling does not specify auditory versus vestibular targets but rather contributes to formation of boundaries for patterning of inner ear projections in the hindbrain.
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Affiliation(s)
- Michelle R. Allen-Sharpley
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, California, United States of America
| | - Michelle Tjia
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, California, United States of America
| | - Karina S. Cramer
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, California, United States of America
- * E-mail:
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10
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Park JE, Son AI, Zhou R. Roles of EphA2 in Development and Disease. Genes (Basel) 2013; 4:334-57. [PMID: 24705208 PMCID: PMC3924825 DOI: 10.3390/genes4030334] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 05/22/2013] [Accepted: 05/23/2013] [Indexed: 01/12/2023] Open
Abstract
The Eph family of receptor tyrosine kinases (RTKs) has been implicated in the regulation of many aspects of mammalian development. Recent analyses have revealed that the EphA2 receptor is a key modulator for a wide variety of cellular functions. This review focuses on the roles of EphA2 in both development and disease.
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Affiliation(s)
- Jeong Eun Park
- Susan Lehman-Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA.
| | - Alexander I Son
- Susan Lehman-Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA.
| | - Renping Zhou
- Susan Lehman-Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA.
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11
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Rodger J, Salvatore L, Migani P. Should I stay or should I go? Ephs and ephrins in neuronal migration. Neurosignals 2012; 20:190-201. [PMID: 22456188 DOI: 10.1159/000333784] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In neuroscience, Ephs and ephrins are perhaps best known for their role in axon guidance. It was first shown in the visual system that graded expression of these proteins is instrumental in providing molecular coordinates that define topographic maps, particularly in the visual system, but also in the auditory, vomeronasal and somatosensory systems as well as in the hippocampus, cerebellum and other structures. Perhaps unsurprisingly, the role of these proteins in regulating cell-cell interactions also has an impact on cell mobility, with evidence that Eph-ephrin interactions segregate cell populations based on contact-mediated attraction or repulsion. Consistent with these studies, evidence has accumulated that Ephs and ephrins play important roles in the migration of specific cell populations in the developing and adult brain. This review focusses on two examples of neuronal migration that require Eph/ephrin signalling - radial and tangential migration of neurons in cortical development and the migration of newly generated neurons along the rostral migratory stream to the olfactory bulb in the adult brain. We discuss the challenge involved in understanding how cells determine whether they respond to signals by migration or axon guidance.
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Affiliation(s)
- Jennifer Rodger
- Experimental and Regenerative Neurosciences, School of Animal Biology M317, University of Western Australia, Crawley, WA, Australia
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12
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Noberini R, Rubio de la Torre E, Pasquale EB. Profiling Eph receptor expression in cells and tissues: a targeted mass spectrometry approach. Cell Adh Migr 2012; 6:102-12. [PMID: 22568954 DOI: 10.4161/cam.19620] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The Eph receptor tyrosine kinase family includes many members, which are often expressed together in various combinations and can promiscuously interact with multiple ephrin ligands, generating intricate networks of intracellular signals that control physiological and pathological processes. Knowing the entire repertoire of Eph receptors and ephrins expressed in a biological sample is important when studying their biological roles. Moreover, given the correlation between Eph receptor/ephrin expression and cancer pathogenesis, their expression patterns could serve important diagnostic and prognostic purposes. However, profiling Eph receptor and ephrin expression has been challenging. Here we describe a novel and straightforward approach to catalog the Eph receptors present in cultured cells and tissues. By measuring the binding of ephrin Fc fusion proteins to Eph receptors in ELISA and pull-down assays, we determined that a mixture of four ephrins is suitable for isolating both EphA and EphB receptors in a single pull-down. We then used mass spectrometry to identify the Eph receptors present in the pull-downs and estimate their relative levels. This approach was validated in cultured human cancer cell lines, human tumor xenograft tissue grown in mice, and mouse brain tissue. The new mass spectrometry approach we have developed represents a useful tool for the identification of the spectrum of Eph receptors present in a biological sample and could also be extended to profiling ephrin expression.
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