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Circuit-Specific Dendritic Development in the Piriform Cortex. eNeuro 2020; 7:ENEURO.0083-20.2020. [PMID: 32457067 PMCID: PMC7307633 DOI: 10.1523/eneuro.0083-20.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/09/2020] [Accepted: 04/20/2020] [Indexed: 11/21/2022] Open
Abstract
Dendritic geometry is largely determined during postnatal development and has a substantial impact on neural function. In sensory processing, postnatal development of the dendritic tree is affected by two dominant circuit motifs, ascending sensory feedforward inputs and descending and local recurrent connections. In the three-layered anterior piriform cortex (aPCx), neurons in the sublayers 2a and 2b display vertical segregation of these two circuit motifs. Here, we combined electrophysiology, detailed morphometry, and Ca2+ imaging in acute mouse brain slices and modeling to study circuit-specific aspects of dendritic development. We observed that determination of branching complexity, dendritic length increases, and pruning occurred in distinct developmental phases. Layer 2a and layer 2b neurons displayed developmental phase-specific differences between their apical and basal dendritic trees related to differences in circuit incorporation. We further identified functional candidate mechanisms for circuit-specific differences in postnatal dendritic growth in sublayers 2a and 2b at the mesoscale and microscale levels. Already in the first postnatal week, functional connectivity of layer 2a and layer 2b neurons during early spontaneous network activity scales with differences in basal dendritic growth. During the early critical period of sensory plasticity in the piriform cortex, our data are consistent with a model that proposes a role for dendritic NMDA-spikes in selecting branches for survival during developmental pruning in apical dendrites. The different stages of the morphologic and functional developmental pattern differences between layer 2a and layer 2b neurons demonstrate the complex interplay between dendritic development and circuit specificity.
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Bazwinsky-Wutschke I, Dehghani F. Impact of cochlear ablation on calretinin and synaptophysin in the gerbil anteroventral cochlear nucleus before the hearing onset. J Chem Neuroanat 2020; 104:101746. [PMID: 31945410 DOI: 10.1016/j.jchemneu.2020.101746] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 01/09/2020] [Accepted: 01/10/2020] [Indexed: 01/31/2023]
Abstract
Mammalian auditory system undergoes many structural and functional modifications during postnatal development, which are dependent on the relationship between auditory nerve fibers and their nuclei. In the present study, the cochlea of Meriones unguiculatus was ablated unilaterally on postnatal day 5 or 9 (P5 or P9), before the onset of hearing. Histochemical analysis of synaptophysin (SYN) and calretinin (CR) in anterior anteroventral cochlear nucleus (AVCN-A) was performed to analyze whether unilateral cochlea ablation induces changes in the auditory terminal endings and somata of spherical bushy cells (SBCs). During the period of postnatal development, CR-labeling was evident in somata of SBCs and in auditory nerve terminals. SYN was most apparent in puncta encircled cell bodies, progressing with age. Cochlear removal at P5 induced a decrease in CR-labeling in SBCs somata 6 h and 48 h post-lesion; whereas, ablation at P9 increased the somatic CR-labeling in the lesioned AVCN-A after 24 and 48 h post-lesion. The SYN-labeled synaptic puncta were remarkably reduced in the AVCN-A of P5- and P9-cochlea-ablated gerbils with stronger effects in P5 animals (a 50% reduction after 48 h). Interestingly, a significant increase in the SYN-immunolabeled puncta was found after 48 h compared to 24 h in the lesioned AVCN-A of P9 gerbils, indicating reactive synaptogenesis. Our study shows, that following the destruction of the cochlea at different postnatal periods, the CR- and SYN-labeling are differentially influenced in the AVCN-A, which in turn coincides with different critical developmental periods before the onset of hearing.
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Affiliation(s)
- Ivonne Bazwinsky-Wutschke
- Department of Biology, University of Leipzig, Talstrasse 33, D-04103 Leipzig, Germany; Department of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Grosse Steinstrasse 52, D-06108 Halle (Saale), Germany.
| | - Faramarz Dehghani
- Department of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Grosse Steinstrasse 52, D-06108 Halle (Saale), Germany
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Presynaptic Diversity Revealed by Ca 2+-Permeable AMPA Receptors at the Calyx of Held Synapse. J Neurosci 2019; 39:2981-2994. [PMID: 30679394 DOI: 10.1523/jneurosci.2565-18.2019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/14/2018] [Accepted: 01/03/2019] [Indexed: 02/06/2023] Open
Abstract
GluA2-lacking Ca2+-permeable AMPARs (CP-AMPARs) play integral roles in synaptic plasticity and can mediate excitotoxic cellular signaling at glutamatergic synapses. However, the developmental profile of functional CP-AMPARs at the auditory brainstem remains poorly understood. Through a combination of electrophysiological and live-cell Ca2+ imaging from mice of either sex, we show that the synaptic release of glutamate from the calyx of Held nerve terminal activates CP-AMPARs in the principal cells of the medial nucleus of the trapezoid body in the brainstem. This leads to significant Ca2+ influx through these receptors before the onset of hearing at postnatal day 12 (P12). Using a selective open channel blocker of CP-AMPARs, IEM-1460, we estimate that ∼80% of the AMPAR population are permeable to Ca2+ at immature P4-P5 synapses. However, after the onset of hearing, Ca2+ influx through these receptors was greatly reduced. We estimate that CP-AMPARs comprise approximately 40% and 33% of the AMPAR population at P18-P22 and P30-P34, respectively. By quantifying the rate of EPSC block by IEM-1460, we found an increased heterogeneity in glutamate release probability for adult-like calyces (P30-P34). Using tetraethylammonium (TEA), a presynaptic potassium channel blocker, we show that the apparent reduction of CP-AMPARs in more mature synapses is not a consequence of presynaptic action potential (AP) speeding. Finally, through postsynaptic AP recordings, we show that inhibition of CP-AMPARs reduces spike fidelity in juvenile synapses, but not in more mature synapses. We conclude that the expression of functional CP-AMPARs declines over early postnatal development in the calyx of Held synapse.SIGNIFICANCE STATEMENT The calyx of Held synapse is pivotal to the circuitry that computes sound localization. Postsynaptic Ca2+ influx via AMPARs may be critical for signaling the maturation of this brainstem synapse. The GluA4 subunit may dominate the AMPAR complex at mature synapses because of its fast gating kinetics and large unitary conductance. The expectation is that AMPARs dominated by GluA4 subunits should be highly Ca2+ permeable. However, we find that Ca2+-permeable AMPAR expression declines during postnatal development. Using the rate of EPSC block by IEM-1460, an open channel blocker of Ca2+-permeable AMPARs, we propose a novel method to determine glutamate release probability and uncover an increased heterogeneity in release probability for more mature calyces of Held nerve terminals.
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Rodgers HM, Belcastro M, Sokolov M, Mathers PH. Embryonic markers of cone differentiation. Mol Vis 2016; 22:1455-1467. [PMID: 28031694 PMCID: PMC5178185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 12/20/2016] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Photoreceptor cells are born in two distinct phases of vertebrate retinogenesis. In the mouse retina, cones are born primarily during embryogenesis, while rod formation occurs later in embryogenesis and early postnatal ages. Despite this dichotomy in photoreceptor birthdates, the visual pigments and phototransduction machinery are not reactive to visual stimulus in either type of photoreceptor cell until the second postnatal week. Several markers of early cone formation have been identified, including Otx2, Crx, Blimp1, NeuroD, Trβ2, Rorβ, and Rxrγ, and all are thought to be involved in cellular determination. However, little is known about the expression of proteins involved in cone visual transduction during early retinogenesis. Therefore, we sought to characterize visual transduction proteins that are expressed specifically in photoreceptors during mouse embryogenesis. METHODS Eye tissue was collected from control and phosducin-null mice at embryonic and early postnatal ages. Immunohistochemistry and quantitative reverse transcriptase-PCR (qPCR) were used to measure the spatial and temporal expression patterns of phosducin (Pdc) and cone transducin γ (Gngt2) proteins and transcripts in the embryonic and early postnatal mouse retina. RESULTS We identified the embryonic expression of phosducin (Pdc) and cone transducin γ (Gngt2) that coincides temporally and spatially with the earliest stages of cone histogenesis. Using immunohistochemistry, the phosducin protein was first detected in the retina at embryonic day (E)12.5, and cone transducin γ was observed at E13.5. The phosducin and cone transducin γ proteins were seen only in the outer neuroblastic layer, consistent with their expression in photoreceptors. At the embryonic ages, phosducin was coexpressed with Rxrγ, a known cone marker, and with Otx2, a marker of photoreceptors. Pdc and Gngt2 mRNAs were detected as early as E10.5 with qPCR, although at low levels. CONCLUSIONS Visual transduction proteins are expressed at the earliest stages in developing cones, well before the onset of opsin gene expression. Given the delay in opsin expression in rods and cones, we speculate on the embryonic function of these G-protein signaling components beyond their roles in the visual transduction cascade.
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Affiliation(s)
- Helen M. Rodgers
- Sensory Neuroscience Research Center, West Virginia University School of Medicine, Morgantown, WV,Neuroscience Graduate Program, West Virginia University School of Medicine, Morgantown, WV,Department of Otolaryngology, West Virginia University School of Medicine, Morgantown, WV
| | - Marycharmain Belcastro
- Sensory Neuroscience Research Center, West Virginia University School of Medicine, Morgantown, WV,Department of Ophthalmology, West Virginia University School of Medicine, Morgantown, WV
| | - Maxim Sokolov
- Sensory Neuroscience Research Center, West Virginia University School of Medicine, Morgantown, WV,Department of Ophthalmology, West Virginia University School of Medicine, Morgantown, WV,Department of Biochemistry, West Virginia University School of Medicine, Morgantown, WV
| | - Peter H. Mathers
- Sensory Neuroscience Research Center, West Virginia University School of Medicine, Morgantown, WV,Department of Otolaryngology, West Virginia University School of Medicine, Morgantown, WV,Department of Ophthalmology, West Virginia University School of Medicine, Morgantown, WV,Department of Biochemistry, West Virginia University School of Medicine, Morgantown, WV
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Dondzillo A, Thompson JA, Klug A. Recurrent Inhibition to the Medial Nucleus of the Trapezoid Body in the Mongolian Gerbil (Meriones Unguiculatus). PLoS One 2016; 11:e0160241. [PMID: 27489949 PMCID: PMC4973988 DOI: 10.1371/journal.pone.0160241] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 07/15/2016] [Indexed: 12/13/2022] Open
Abstract
Principal neurons in the medial nucleus of the trapezoid body (MNTB) receive strong and temporally precise excitatory input from globular bushy cells in the cochlear nucleus through the calyx of Held. The extremely large synaptic currents produced by the calyx have sometimes led to the view of the MNTB as a simple relay synapse which converts incoming excitation to outgoing inhibition. However, electrophysiological and anatomical studies have shown the additional presence of inhibitory glycinergic currents that are large enough to suppress action potentials in MNTB neurons at least in some cases. The source(s) of glycinergic inhibition to MNTB are not fully understood. One major extrinsic source of glycinergic inhibitory input to MNTB is the ventral nucleus of the trapezoid body. However, it has been suggested that MNTB neurons receive additional inhibitory inputs via intrinsic connections (collaterals of glycinergic projections of MNTB neurons). While several authors have postulated their presence, these collaterals have never been examined in detail. Here we test the hypothesis that collaterals of MNTB principal cells provide glycinergic inhibition to the MNTB. We injected dye into single principal neurons in the MNTB, traced their projections, and immunohistochemically identified their synapses. We found that collaterals terminate within the MNTB and provide an additional source of inhibition to other principal cells, creating an inhibitory microcircuit within the MNTB. Only about a quarter to a third of MNTB neurons receive such collateral inputs. This microcircuit could produce side band inhibition and enhance frequency tuning of MNTB neurons, consistent with physiological observations.
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Affiliation(s)
- Anna Dondzillo
- Department of Physiology & Biophysics, University of Colorado, School of Medicine, Aurora, CO, 80045, United States of America
- * E-mail:
| | - John A. Thompson
- Department of Neurosurgery, School of Medicine, University of Colorado, Aurora, CO, 80045, United States of America
| | - Achim Klug
- Department of Physiology & Biophysics, University of Colorado, School of Medicine, Aurora, CO, 80045, United States of America
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Palladino G, Loizzo S, Fortuna A, Canterini S, Palombi F, Erickson RP, Mangia F, Fiorenza MT. Visual evoked potentials of Niemann-Pick type C1 mice reveal an impairment of the visual pathway that is rescued by 2-hydroxypropyl-ß-cyclodextrin. Orphanet J Rare Dis 2015; 10:133. [PMID: 26458950 PMCID: PMC4603821 DOI: 10.1186/s13023-015-0348-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/27/2015] [Indexed: 12/21/2022] Open
Abstract
Background The lysosomal storage disorder, Niemann Pick type C1 (NPC1), presents a variable phenotype including neurovisceral and neurological symptoms. 2-Hydroxypropyl-ß-cyclodextrin (HPßCD)-based therapies are presently the most promising route of intervention. While severe cerebellar dysfunction remains the main disabling feature of NPC1, sensory functions including auditory and olfactory ones are also affected. Morphological and functional anomalies of Npc1−/− mouse retina have also been observed, although the functional integrity of the visual pathway from retina to visual cortex is still unsettled. We have addressed this issue by characterizing the visual evoked potential (VEP) response of Npc1−/− mice and determining if/how HPßCD administration influences the VEPs of both Npc1−/− and Npc1+/+ mice. Methods VEP elicited by a brief visual stimulus were recorded from the scalp overlying the visual cortex of adult (PN, postnatal days 60, 75, 85 and 100) Npc1+/+ and Npc1−/− mice that had received repeated injections of either HPßCD or plain vehicle. The first injection was given at PN4 and was followed by a second one at PN7 and thereafter by weekly injections up to PN49. Cholesterol accumulation and myelin loss were finally assessed by filipin staining and myelin basic protein immunohistochemistry, respectively. Results and discussion We have found that the transmission of visual signals from retina to visual cortex is negatively influenced by the loss of Npc1 function. In fact, the VEP response of Npc1−/− mice displayed a highly significant increase in the latency compared to that of Npc1+/+ mice. HPßCD administration fully rescued this defect and counteracted the cholesterol accumulation in retinal ganglion cells and dorsal lateral geniculate nucleus neurons, as well as the myelin loss in optic nerve fibers and axons projecting to the visual cortex observed in of Npc1−/− mice. By contrast, HPßCD administration had no effect on the VEP response of Npc1+/+ mice, further strengthening the treatment efficacy. Conclusions This study pinpoints the analysis of VEP response as a potentially accurate and non-invasive approach to assess neural activity and visual information processing in NPC1 patients, as well as for monitoring the progression of the disease and assessing the efficacy of potential therapies. Electronic supplementary material The online version of this article (doi:10.1186/s13023-015-0348-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Giampiero Palladino
- Department of Psychology, Section of Neuroscience and "Daniel Bovet" Neurobiology Research Center, Sapienza University of Rome, 00185, Rome, Italy
| | - Stefano Loizzo
- Department of Therapeutic Research and Medicines Evaluation, Istituto Superiore di Sanità, via Regina Elena 299, 00161, Rome, Italy
| | - Andrea Fortuna
- Department of Therapeutic Research and Medicines Evaluation, Istituto Superiore di Sanità, via Regina Elena 299, 00161, Rome, Italy
| | - Sonia Canterini
- Department of Psychology, Section of Neuroscience and "Daniel Bovet" Neurobiology Research Center, Sapienza University of Rome, 00185, Rome, Italy
| | - Fioretta Palombi
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161, Rome, Italy
| | - Robert P Erickson
- Department of Pediatrics, University of Arizona, Tucson, AZ, 85724-5073, USA
| | - Franco Mangia
- Department of Psychology, Section of Neuroscience and "Daniel Bovet" Neurobiology Research Center, Sapienza University of Rome, 00185, Rome, Italy
| | - Maria Teresa Fiorenza
- Department of Psychology, Section of Neuroscience and "Daniel Bovet" Neurobiology Research Center, Sapienza University of Rome, 00185, Rome, Italy.
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Ebbers L, Satheesh SV, Janz K, Rüttiger L, Blosa M, Hofmann F, Morawski M, Griesemer D, Knipper M, Friauf E, Nothwang HG. L-type Calcium Channel Cav1.2 Is Required for Maintenance of Auditory Brainstem Nuclei. J Biol Chem 2015; 290:23692-710. [PMID: 26242732 DOI: 10.1074/jbc.m115.672675] [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: 06/15/2015] [Indexed: 12/13/2022] Open
Abstract
Cav1.2 and Cav1.3 are the major L-type voltage-gated Ca(2+) channels in the CNS. Yet, their individual in vivo functions are largely unknown. Both channel subunits are expressed in the auditory brainstem, where Cav1.3 is essential for proper maturation. Here, we investigated the role of Cav1.2 by targeted deletion in the mouse embryonic auditory brainstem. Similar to Cav1.3, loss of Cav1.2 resulted in a significant decrease in the volume and cell number of auditory nuclei. Contrary to the deletion of Cav1.3, the action potentials of lateral superior olive (LSO) neurons were narrower compared with controls, whereas the firing behavior and neurotransmission appeared unchanged. Furthermore, auditory brainstem responses were nearly normal in mice lacking Cav1.2. Perineuronal nets were also unaffected. The medial nucleus of the trapezoid body underwent a rapid cell loss between postnatal days P0 and P4, shortly after circuit formation. Phosphorylated cAMP response element-binding protein (CREB), nuclear NFATc4, and the expression levels of p75NTR, Fas, and FasL did not correlate with cell death. These data demonstrate for the first time that both Cav1.2 and Cav1.3 are necessary for neuronal survival but are differentially required for the biophysical properties of neurons. Thus, they perform common as well as distinct functions in the same tissue.
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Affiliation(s)
- Lena Ebbers
- From the Neurogenetics Group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Somisetty V Satheesh
- From the Neurogenetics Group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Katrin Janz
- the Animal Physiology Group, Department of Biology, University of Kaiserlautern, P. O. Box 3049, 67663 Kaiserslautern, Germany
| | - Lukas Rüttiger
- the Department of Otolaryngology, Hearing Research Centre Tübingen (THRC), Molecular Physiology of Hearing, University of Tübingen, Elfriede Aulhorn Strasse 5, 72076 Tübingen, Germany
| | - Maren Blosa
- the Paul Flechsig Institute of Brain Research, Faculty of Medicine, University Leipzig, Liebigstrasse 19, 04103 Leipzig, Germany
| | - Franz Hofmann
- the Institut für Pharmakologie und Toxikologie, Technische Universität, Biedersteiner Strasse 29, D-80802 München, and
| | - Markus Morawski
- the Paul Flechsig Institute of Brain Research, Faculty of Medicine, University Leipzig, Liebigstrasse 19, 04103 Leipzig, Germany
| | - Désirée Griesemer
- the Animal Physiology Group, Department of Biology, University of Kaiserlautern, P. O. Box 3049, 67663 Kaiserslautern, Germany
| | - Marlies Knipper
- the Department of Otolaryngology, Hearing Research Centre Tübingen (THRC), Molecular Physiology of Hearing, University of Tübingen, Elfriede Aulhorn Strasse 5, 72076 Tübingen, Germany
| | - Eckhard Friauf
- the Animal Physiology Group, Department of Biology, University of Kaiserlautern, P. O. Box 3049, 67663 Kaiserslautern, Germany
| | - Hans Gerd Nothwang
- From the Neurogenetics Group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany, the Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
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Wang HC, Bergles DE. Spontaneous activity in the developing auditory system. Cell Tissue Res 2015; 361:65-75. [PMID: 25296716 PMCID: PMC7046314 DOI: 10.1007/s00441-014-2007-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022]
Abstract
Spontaneous electrical activity is a common feature of sensory systems during early development. This sensory-independent neuronal activity has been implicated in promoting their survival and maturation, as well as growth and refinement of their projections to yield circuits that can rapidly extract information about the external world. Periodic bursts of action potentials occur in auditory neurons of mammals before hearing onset. This activity is induced by inner hair cells (IHCs) within the developing cochlea, which establish functional connections with spiral ganglion neurons (SGNs) several weeks before they are capable of detecting external sounds. During this pre-hearing period, IHCs fire periodic bursts of Ca(2+) action potentials that excite SGNs, triggering brief but intense periods of activity that pass through auditory centers of the brain. Although spontaneous activity requires input from IHCs, there is ongoing debate about whether IHCs are intrinsically active and their firing periodically interrupted by external inhibitory input (IHC-inhibition model), or are intrinsically silent and their firing periodically promoted by an external excitatory stimulus (IHC-excitation model). There is accumulating evidence that inner supporting cells in Kölliker's organ spontaneously release ATP during this time, which can induce bursts of Ca(2+) spikes in IHCs that recapitulate many features of auditory neuron activity observed in vivo. Nevertheless, the role of supporting cells in this process remains to be established in vivo. A greater understanding of the molecular mechanisms responsible for generating IHC activity in the developing cochlea will help reveal how these events contribute to the maturation of nascent auditory circuits.
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Affiliation(s)
- Han Chin Wang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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The emerging framework of mammalian auditory hindbrain development. Cell Tissue Res 2015; 361:33-48. [DOI: 10.1007/s00441-014-2110-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 12/22/2014] [Indexed: 02/06/2023]
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10
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Willaredt MA, Ebbers L, Nothwang HG. Central auditory function of deafness genes. Hear Res 2014; 312:9-20. [DOI: 10.1016/j.heares.2014.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 01/31/2014] [Accepted: 02/10/2014] [Indexed: 01/11/2023]
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11
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Alexander M, Garbus H, Smith AL, Fitch RH. Cell size anomalies in the auditory thalamus of rats with hypoxic-ischemic injury on postnatal day 3 or 7. Int J Dev Neurosci 2014; 33:1-7. [PMID: 24184287 PMCID: PMC3945053 DOI: 10.1016/j.ijdevneu.2013.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 10/17/2013] [Accepted: 10/18/2013] [Indexed: 11/28/2022] Open
Abstract
Children born prematurely (<37 weeks gestational age) or at very low birth weight (VLBW; <1500g) are at increased risk for hypoxic ischemic (HI) brain injuries. Term infants can also suffer HI from birth complications. In both groups, blood/oxygen delivery to the brain is compromised, often resulting in brain damage and later cognitive delays (e.g., language deficits). Literature suggests that language delays in a variety of developmentally impaired populations (including specific language impairment (SLI), dyslexia, and early HI-injury) may be associated with underlying deficits in rapid auditory processing (RAP; the ability to process and discriminate brief acoustic cues). Data supporting a relationship between RAP deficits and poor language outcomes is consistent with the "magnocellular theory," which purports that damage to or loss of large (magnocellular) cells in thalamic nuclei could underlie disruptions in temporal processing of sensory input, possibly including auditory (medial geniculate nucleus; MGN) information This theory could be applied to neonatal HI populations that show subsequent RAP deficits. In animal models of neonatal HI, persistent RAP deficits are seen in postnatal (P)7 HI injured rats (who exhibit neuropathology comparable to term birth injury), but not in P1-3 HI injured rodents (who exhibit neuropathology comparable to human pre-term injury). The current study sought to investigate the mean cell size, cell number, and cumulative probability of cell size in the MGN of P3 HI and P7 HI injured male rats that had previously demonstrated behavioral RAP deficits. Pilot data from our lab (Alexander, 2011) previously revealed cell size abnormalities (a shift toward smaller cells) in P7 but not P1 HI injured animals when compared to shams. Our current finding support this result, with evidence of a significant shift to smaller cells in the experimental MGN of P7 HI but not P3 HI subjects. P7 HI animals also showed significantly fewer cells in the affected (right) MGN as compared P3 HI and shams animals. Moreover, cell number in the right hemisphere was found to correlate with gap detection (fewer cells=worse performance) in P7 HI injured subjects. These findings could be applied to clinical populations, providing an anatomic marker that may index potential long-term language disabilities in HI injured infants and possibly other at-risk populations.
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Affiliation(s)
- Michelle Alexander
- University of Connecticut, Department of Psychology, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, United States.
| | - Haley Garbus
- University of Connecticut, Department of Psychology, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, United States
| | - Amanda L Smith
- University of Connecticut, Department of Psychology, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, United States
| | - R Holly Fitch
- University of Connecticut, Department of Psychology, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, United States
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Fitch RH, Alexander ML, Threlkeld SW. Early neural disruption and auditory processing outcomes in rodent models: implications for developmental language disability. Front Syst Neurosci 2013; 7:58. [PMID: 24155699 PMCID: PMC3800847 DOI: 10.3389/fnsys.2013.00058] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 09/11/2013] [Indexed: 02/03/2023] Open
Abstract
Most researchers in the field of neural plasticity are familiar with the "Kennard Principle," which purports a positive relationship between age at brain injury and severity of subsequent deficits (plateauing in adulthood). As an example, a child with left hemispherectomy can recover seemingly normal language, while an adult with focal injury to sub-regions of left temporal and/or frontal cortex can suffer dramatic and permanent language loss. Here we present data regarding the impact of early brain injury in rat models as a function of type and timing, measuring long-term behavioral outcomes via auditory discrimination tasks varying in temporal demand. These tasks were created to model (in rodents) aspects of human sensory processing that may correlate-both developmentally and functionally-with typical and atypical language. We found that bilateral focal lesions to the cortical plate in rats during active neuronal migration led to worse auditory outcomes than comparable lesions induced after cortical migration was complete. Conversely, unilateral hypoxic-ischemic (HI) injuries (similar to those seen in premature infants and term infants with birth complications) led to permanent auditory processing deficits when induced at a neurodevelopmental point comparable to human "term," but only transient deficits (undetectable in adulthood) when induced in a "preterm" window. Convergent evidence suggests that regardless of when or how disruption of early neural development occurs, the consequences may be particularly deleterious to rapid auditory processing (RAP) outcomes when they trigger developmental alterations that extend into subcortical structures (i.e., lower sensory processing stations). Collective findings hold implications for the study of behavioral outcomes following early brain injury as well as genetic/environmental disruption, and are relevant to our understanding of the neurologic risk factors underlying developmental language disability in human populations.
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Affiliation(s)
- R Holy Fitch
- 1Department of Psychology/Behavioral Neuroscience, University of Connecticut Storrs, CT, USA
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Felix RA, Vonderschen K, Berrebi AS, Magnusson AK. Development of on-off spiking in superior paraolivary nucleus neurons of the mouse. J Neurophysiol 2013; 109:2691-704. [PMID: 23515791 DOI: 10.1152/jn.01041.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The superior paraolivary nucleus (SPON) is a prominent cell group in the auditory brain stem that has been increasingly implicated in representing temporal sound structure. Although SPON neurons selectively respond to acoustic signals important for sound periodicity, the underlying physiological specializations enabling these responses are poorly understood. We used in vitro and in vivo recordings to investigate how SPON neurons develop intrinsic cellular properties that make them well suited for encoding temporal sound features. In addition to their hallmark rebound spiking at the stimulus offset, SPON neurons were characterized by spiking patterns termed onset, adapting, and burst in response to depolarizing stimuli in vitro. Cells with burst spiking had some morphological differences compared with other SPON neurons and were localized to the dorsolateral region of the nucleus. Both membrane and spiking properties underwent strong developmental regulation, becoming more temporally precise with age for both onset and offset spiking. Single-unit recordings obtained in young mice demonstrated that SPON neurons respond with temporally precise onset spiking upon tone stimulation in vivo, in addition to the typical offset spiking. Taken together, the results of the present study demonstrate that SPON neurons develop sharp on-off spiking, which may confer sensitivity to sound amplitude modulations or abrupt sound transients. These findings are consistent with the proposed involvement of the SPON in the processing of temporal sound structure, relevant for encoding communication cues.
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Affiliation(s)
- Richard A Felix
- Center for Hearing and Communication Research, Karolinska Institutet and Department of Clinical Science, Intervention and Technology, Karolinska University Hospital, Stockholm, Sweden
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Satheesh SV, Kunert K, Rüttiger L, Zuccotti A, Schönig K, Friauf E, Knipper M, Bartsch D, Nothwang HG. Retrocochlear function of the peripheral deafness gene Cacna1d. Hum Mol Genet 2012; 21:3896-909. [PMID: 22678062 DOI: 10.1093/hmg/dds217] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Hearing impairment represents the most common sensory deficit in humans. Genetic mutations contribute significantly to this disorder. Mostly, only malfunction of the ear is considered. Here, we assessed the role of the peripheral deafness gene Cacna1d, encoding the L-type channel Ca(v)1.3, in downstream processing of acoustic information. To this end, we generated a mouse conditional Cacna1d-eGFP(flex) allele. Upon pairing with Egr2::Cre mice, Ca(v)1.3 was ablated in the auditory brainstem, leaving the inner ear intact. Structural assessment of the superior olivary complex (SOC), an essential auditory brainstem center, revealed a dramatic volume reduction (43-47%) of major nuclei in young adult Egr2::Cre;Cacna1d-eGFP(flex) mice. This volume decline was mainly caused by a reduced cell number (decline by 46-56%). Abnormal formation of the lateral superior olive was already present at P4, demonstrating an essential perinatal role of Ca(v)1.3 in the SOC. Measurements of auditory brainstem responses demonstrated a decreased amplitude in the auditory nerve between 50 and 75 dB stimulation in Egr2::Cre;Cacna1d-eGFP(flex) knockout mice and increased amplitudes in central auditory processing centers. Immunohistochemical studies linked the amplitude changes in the central auditory system to reduced expression of K(v)1.2. No changes were observed for K(v)1.1, KCC2, a determinant of inhibitory neurotransmission, and choline acetyltransferase, a marker of efferent olivocochlear neurons. Together, these analyses identify a crucial retrocochlear role of Ca(v)1.3 and demonstrate that mutations in deafness genes can affect sensory cells and neurons alike. As a corollary, hearing aids have to address central auditory processing deficits as well.
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Affiliation(s)
- Somisetty V Satheesh
- Department of Neurogenetics, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
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Marrs GS, Spirou GA. Embryonic assembly of auditory circuits: spiral ganglion and brainstem. J Physiol 2012; 590:2391-408. [PMID: 22371481 DOI: 10.1113/jphysiol.2011.226886] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
During early development, peripheral sensory systems generate physiological activity prior to exposure to normal environmental stimuli. This activity is thought to facilitate maturation of these neurons and their connections, perhaps even promoting efficacy or modifying downstream circuitry. In the mammalian auditory system, initial connections form at embryonic ages, but the functional characteristics of these early neural connections have not been assayed. We investigated processes of embryonic auditory development using a whole-head slice preparation that preserved connectivity between peripheral and brainstem stations of the auditory pathway. Transgenic mice expressing fluorescent protein provided observation of spiral ganglion and cochlear nucleus neurons to facilitate targeted electrophysiological recording. Here we demonstrate an apparent peripheral-to-central order for circuit maturation. Spiral ganglion cells acquire action potential-generating capacity at embryonic day 14 (E14), the earliest age tested, and action potential waveforms begin to mature in advance of comparable states for neurons of the ventral cochlear nucleus (VCN) and medial nucleus of the trapezoid body (MNTB). In accordance, auditory nerve synapses in the VCN are functional at E15, prior to VCN connectivity with the MNTB, which occurs at least 1 day later. Spiral ganglion neurons exhibit spontaneous activity at least by E14 and are able to drive third-order auditory brainstem neurons by E17. This activity precedes cochlear-generated wave activity by 4 days and ear canal opening by at least 2 weeks. Together, these findings reveal a previously unknown initial developmental phase for auditory maturation, and further implicate the spiral ganglion as a potential controlling centre in this process.
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Affiliation(s)
- Glen S Marrs
- Center for Neuroscience, West Virginia University School of Medicine, Morgantown, WV 26506-9303, USA.
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Xiong Y, Liu X, Han L, Yan J. The ongoing balance of cortical excitation and inhibition during early development. Neurosci Biobehav Rev 2011; 35:2114-6. [PMID: 21334375 DOI: 10.1016/j.neubiorev.2011.02.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 02/08/2011] [Accepted: 02/08/2011] [Indexed: 11/26/2022]
Abstract
Two papers recently published in Nature propose that the balance between excitation and inhibition is important for the maturation of cortical function. Their conclusions however, are contradictory; one study suggests that balance is established before hearing onset, whereas the other proposes that balance is established after hearing onset. We carefully examined the data and found that the differences between the two groups are less dramatic than they first appear. Despite their methodological differences, both studies provide evidence that an ongoing balance between cortical excitation/inhibition accounts for the maturation and refinement of cortical function during early development.
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Affiliation(s)
- Ying Xiong
- Department of Neurobiology, Third Military Medical University, Chongqing, PR China
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Nakamura PA, Cramer KS. Formation and maturation of the calyx of Held. Hear Res 2010; 276:70-8. [PMID: 21093567 DOI: 10.1016/j.heares.2010.11.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2010] [Revised: 11/03/2010] [Accepted: 11/10/2010] [Indexed: 11/24/2022]
Abstract
Sound localization requires precise and specialized neural circuitry. A prominent and well-studied specialization is found in the mammalian auditory brainstem. Globular bushy cells of the ventral cochlear nucleus (VCN) project contralaterally to neurons of the medial nucleus of the trapezoid body (MNTB), where their large axons terminate on cell bodies of MNTB principal neurons, forming the calyces of Held. The VCN-MNTB pathway is necessary for the accurate computation of interaural intensity and time differences; MNTB neurons provide inhibitory input to the lateral superior olive, which compares levels of excitation from the ipsilateral ear to levels of tonotopically matched inhibition from the contralateral ear, and to the medial superior olive, where precise inhibition from MNTB neurons tunes the delays of binaural excitation. Here we review the morphological and physiological aspects of the development of the VCN-MNTB pathway and its calyceal termination, along with potential mechanisms that give rise to its precision. During embryonic development, VCN axons grow towards the midline, cross the midline into the region of the presumptive MNTB and then form collateral branches that will terminate in calyces of Held. In rodents, immature calyces of Held appear in MNTB during the first few days of postnatal life. These calyces mature morphologically and physiologically over the next three postnatal weeks, enabling fast, high fidelity transmission in the VCN-MNTB pathway.
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Affiliation(s)
- Paul A Nakamura
- Department of Neurobiology and Behavior, University of California, Irvine, 2205 McGaugh Hall, Irvine, CA 92697-4550, USA
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Shideler KK, Yan J. M1 muscarinic receptor for the development of auditory cortical function. Mol Brain 2010; 3:29. [PMID: 20964868 PMCID: PMC2972260 DOI: 10.1186/1756-6606-3-29] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Accepted: 10/22/2010] [Indexed: 02/02/2023] Open
Abstract
The sensory cortex is subject to continuous remodelling during early development and throughout adulthood. This process is important for establishing normal brain function and is dependent on cholinergic modulation via muscarinic receptors. Five muscarinic receptor genes encode five unique receptor subtypes (M1-5). The distributions and functions of each subtype vary in central and peripheral systems. In the brain, the M1 receptor is most abundant in the cerebral cortex, where its immunoreactivity peaks transiently during early development. This likely signifies the importance of M1 receptor in the development and maintenance of normal cortical function. Several lines of study have outlined the roles of M1 receptors in the development and plasticity of the auditory cortex. For example, M1-knockout reduces experience-dependent plasticity and disrupts tonotopic mapping in the adult mouse auditory cortex. Further evidence demonstrates a role for M1 in neurite outgrowth and hence determining the structure of cortical neurons. The disruption of tonotopic maps in M1-knockout mice may be linked to alterations in thalamocortical connectivity, because the targets of thalamocortical afferents (layer IV cortical neurons) appear less mature in M1 knockouts. Herein we review the literature to date concerning M1 receptors in the auditory cortex and consider some future directions that will contribute to our understanding.
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Affiliation(s)
- Karalee K Shideler
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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Current Opinion in Otolaryngology & Head and Neck Surgery. Current world literature. Curr Opin Otolaryngol Head Neck Surg 2010; 18:466-74. [PMID: 20827086 DOI: 10.1097/moo.0b013e32833f3865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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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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Ephrin-B reverse signaling is required for formation of strictly contralateral auditory brainstem pathways. J Neurosci 2010; 30:9840-9. [PMID: 20660266 DOI: 10.1523/jneurosci.0386-10.2010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Specificity in the projections from the mammalian ventral cochlear nucleus (VCN) is essential for sound localization. Globular bushy cells project from the VCN to the medial nucleus of the trapezoid body (MNTB) on the contralateral, but not the ipsilateral, side of the brainstem, terminating in large synaptic endings known as calyces of Held. The precision in this pathway is critical for the computation of interaural intensity differences, which are used in sound localization. The mechanisms underlying the development of this projection are not completely understood. In this study, we tested the role of Eph receptor tyrosine kinases and their ephrin ligands in limiting the VCN-MNTB projection to the contralateral side. We found that mice with null mutations in EphB2 and EphB3 had normal contralateral VCN-MNTB projections, yet these projections also had significant numbers of aberrant collateral branches in the ipsilateral MNTB. These aberrant branches ended in calyceal terminations in MNTB. Similar ipsilateral projections were seen in mice with mutations in ephrin-B2. In both of these mouse lines, ipsilateral projections formed concurrently with normal contralateral projections and were not eliminated later in development. However, mice with mutations that affected only the intracellular domain of EphB2 had normal, strictly contralateral VCN-MNTB projections. Expression studies showed that EphB2 is expressed in VCN axons and ephrin-B2 is expressed in MNTB. Together, these data suggest that EphB2-ephrin-B2 reverse signaling is required to prevent the formation of ipsilateral VCN-MNTB projections and that this signaling operates non-cell autonomously.
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