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Dai X, Pang S, Wang J, FitzMaurice B, Pang J, Chang B. Photoreceptor degeneration in a new Cacna1f mutant mouse model. Exp Eye Res 2018; 179:106-114. [PMID: 30445045 DOI: 10.1016/j.exer.2018.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/17/2018] [Accepted: 11/12/2018] [Indexed: 02/06/2023]
Abstract
The Cacna1f gene encodes the α1F subunit of an L-type voltage-gated calcium channel, Cav1.4. In photoreceptor synaptic terminals, Cav1.4 channels mediate glutamate release and postsynaptic responses associated with visual signal transmission. We have discovered a new Cacna1f mutation in nob9 mice, which display more severe phenotypes than do nob2 mice. To characterize the nob9 phenotype at different ages, we examined the murine fundus, applied retinal optical coherence tomography, measured flash electroretinograms (ERGs) in vivo, and analyzed the retinal histology in vitro. After identifying the X-linked recessive inheritance trait, we sequenced Cacna1f as the candidate gene. Mutations in this gene were detected by polymerase chain reaction (PCR) and confirmed by restriction fragment length polymorphism. Morphologically, an early-onset of retinal disorder was detected, and the degeneration of the outer plexiform layers progressed rapidly. Moreover, the mutant mice showed drastically reduced scotopic ERGs with increasing age. In 14-month-old nob9 retinas, immunostaining of cone opsins demonstrated a reduction in the number of short-wavelength opsins (S-opsins) to 54% of wild-type levels, and almost no middle-wavelength opsins (M-opsins) were observed. No cone ERGs could be detected from residual cones, in which S-opsins abnormally migrated to inner segments of the photoreceptors. The mutations of the Cacna1f gene in nob9 mice involved both a single nucleotide G to A transition and a 10-nucleotide insertion, the latter resulting in a frame-shift mutation in exon 14.
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Affiliation(s)
- Xufeng Dai
- School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325027, China; Department of Ophthalmology, University of Florida, Gainesville, FL, 32610, USA
| | - Shiyi Pang
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA; College of Medicine, University of Florida, Gainesville, FL, 32610, USA
| | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA
| | | | - Jijing Pang
- School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325027, China; Department of Ophthalmology, University of Florida, Gainesville, FL, 32610, USA; College of Medicine, University of Florida, Gainesville, FL, 32610, USA; Eye Research Institute, Xiamen Eye Center of Xiamen University, Xiamen, 361001, China.
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA.
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52
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Williams B, Haeseleer F, Lee A. Splicing of an automodulatory domain in Ca v1.4 Ca 2+ channels confers distinct regulation by calmodulin. J Gen Physiol 2018; 150:1676-1687. [PMID: 30355583 PMCID: PMC6279360 DOI: 10.1085/jgp.201812140] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 10/03/2018] [Indexed: 12/17/2022] Open
Abstract
Cav1.4 Ca2+ channels provide maintained Ca2+ entry to support sustained neurotransmitter release, but a retinal splice variant exhibits calmodulin-dependent inactivation. Williams et al. show that the N lobe of calmodulin is involved in this process as well as Ca2+-dependent enhancement of channel activation. Ca2+ influx through Cav1.4 L-type Ca2+ channels supports the sustained release of glutamate from photoreceptor synaptic terminals in darkness, a process that is critical for vision. Consistent with this role, Cav1.4 exhibits weak Ca2+-dependent inactivation (CDI)—a negative feedback regulation mediated by Ca2+-bound calmodulin (CaM). CaM binds to a conserved IQ domain in the proximal C-terminal domain of Cav channels, but in Cav1.4, a C-terminal modulatory domain (CTM) disrupts interactions with CaM. Exon 47 encodes a portion of the CTM and is deleted in a Cav1.4 splice variant (Cav1.4Δex47) that is highly expressed in the human retina. Cav1.4Δex47 exhibits CDI and enhanced voltage-dependent activation, similar to that caused by a mutation that is associated with congenital stationary night blindness type 2, in which the CTM is deleted (K1591X). The presence of CDI and very negative activation thresholds in a naturally occurring variant of Cav1.4 are perplexing considering that these properties are expected to be maladaptive for visual signaling and result in night blindness in the case of K1591X. Here we show that Cav1.4Δex47 and K1591X exhibit fundamental differences in their regulation by CaM. In Cav1.4Δex47, CDI requires both the N-terminal (N lobe) and C-terminal (C lobe) lobes of CaM to bind Ca2+, whereas CDI in K1591X is driven mainly by Ca2+ binding to the C lobe. Moreover, the CaM N lobe causes a Ca2+-dependent enhancement of activation of Cav1.4Δex47 but not K1591X. We conclude that the residual CTM in Cav1.4Δex47 enables a form of CaM N lobe regulation of activation and CDI that is absent in K1591X. Interaction with the N lobe of CaM, which is more sensitive to global elevations in cytosolic Ca2+ than the C lobe, may allow Cav1.4Δex47 to be modulated by a wider range of synaptic Ca2+ concentrations than K1591X; this may distinguish the normal physiological function of Cav1.4Δex47 from the pathological consequences of K1591X.
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Affiliation(s)
- Brittany Williams
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA.,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA.,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA
| | - Françoise Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA .,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA.,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA.,Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA.,Department of Neurology, University of Iowa, Iowa City, IA
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53
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Abstract
This review will first describe the importance of Ca2+ entry for function of excitable cells, and the subsequent discovery of voltage-activated calcium conductances in these cells. This finding was rapidly followed by the identification of multiple subtypes of calcium conductance in different tissues. These were initially termed low- and high-voltage activated currents, but were then further subdivided into L-, N-, PQ-, R- and T-type calcium currents on the basis of differing pharmacology, voltage-dependent and kinetic properties, and single channel conductance. Purification of skeletal muscle calcium channels allowed the molecular identification of the pore-forming and auxiliary α2δ, β and ϒ subunits present in these calcium channel complexes. These advances then led to the cloning of the different subunits, which permitted molecular characterisation, to match the cloned channels with physiological function. Studies with knockout and other mutant mice then allowed further investigation of physiological and pathophysiological roles of calcium channels. In terms of pharmacology, cardiovascular L-type channels are targets for the widely used antihypertensive 1,4-dihydropyridines and other calcium channel blockers, N-type channels are a drug target in pain, and α2δ-1 is the therapeutic target of the gabapentinoid drugs, used in neuropathic pain. Recent structural advances have allowed a deeper understanding of Ca2+ permeation through the channel pore and the structure of both the pore-forming and auxiliary subunits. Voltage-gated calcium channels are subject to multiple pathways of modulation by G-protein and second messenger regulation. Furthermore, their trafficking pathways, subcellular localisation and functional specificity are the subjects of active investigation.
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54
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Kerov V, Laird JG, Joiner ML, Knecht S, Soh D, Hagen J, Gardner SH, Gutierrez W, Yoshimatsu T, Bhattarai S, Puthussery T, Artemyev NO, Drack AV, Wong RO, Baker SA, Lee A. α 2δ-4 Is Required for the Molecular and Structural Organization of Rod and Cone Photoreceptor Synapses. J Neurosci 2018; 38:6145-6160. [PMID: 29875267 PMCID: PMC6031576 DOI: 10.1523/jneurosci.3818-16.2018] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 05/10/2018] [Accepted: 05/31/2018] [Indexed: 11/21/2022] Open
Abstract
α2δ-4 is an auxiliary subunit of voltage-gated Cav1.4 L-type channels that regulate the development and mature exocytotic function of the photoreceptor ribbon synapse. In humans, mutations in the CACNA2D4 gene encoding α2δ-4 cause heterogeneous forms of vision impairment in humans, the underlying pathogenic mechanisms of which remain unclear. To investigate the retinal function of α2δ-4, we used genome editing to generate an α2δ-4 knock-out (α2δ-4 KO) mouse. In male and female α2δ-4 KO mice, rod spherules lack ribbons and other synaptic hallmarks early in development. Although the molecular organization of cone synapses is less affected than rod synapses, horizontal and cone bipolar processes extend abnormally in the outer nuclear layer in α2δ-4 KO retina. In reconstructions of α2δ-4 KO cone pedicles by serial block face scanning electron microscopy, ribbons appear normal, except that less than one-third show the expected triadic organization of processes at ribbon sites. The severity of the synaptic defects in α2δ-4 KO mice correlates with a progressive loss of Cav1.4 channels, first in terminals of rods and later cones. Despite the absence of b-waves in electroretinograms, visually guided behavior is evident in α2δ-4 KO mice and better under photopic than scotopic conditions. We conclude that α2δ-4 plays an essential role in maintaining the structural and functional integrity of rod and cone synapses, the disruption of which may contribute to visual impairment in humans with CACNA2D4 mutations.SIGNIFICANCE STATEMENT In the retina, visual information is first communicated by the synapse formed between photoreceptors and second-order neurons. The mechanisms that regulate the structural integrity of this synapse are poorly understood. Here we demonstrate a role for α2δ-4, a subunit of voltage-gated Ca2+ channels, in organizing the structure and function of photoreceptor synapses. We find that presynaptic Ca2+ channels are progressively lost and that rod and cone synapses are disrupted in mice that lack α2δ-4. Our results suggest that alterations in presynaptic Ca2+ signaling and photoreceptor synapse structure may contribute to vision impairment in humans with mutations in the CACNA2D4 gene encoding α2δ-4.
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Affiliation(s)
- Vasily Kerov
- Department of Molecular Physiology and Biophysics
| | | | | | - Sharmon Knecht
- Department of Biological Structure, University of Washington, Seattle, Washington 98195, and
| | - Daniel Soh
- Department of Molecular Physiology and Biophysics
| | | | | | | | - Takeshi Yoshimatsu
- Department of Biological Structure, University of Washington, Seattle, Washington 98195, and
| | - Sajag Bhattarai
- Department of Ophthalmology and Institute for Vision Research
| | - Teresa Puthussery
- Casey Eye Institute, Oregon Health & Science University, Portland, Oregon 97239
| | | | - Arlene V Drack
- Department of Ophthalmology and Institute for Vision Research
| | - Rachel O Wong
- Department of Biological Structure, University of Washington, Seattle, Washington 98195, and
| | - Sheila A Baker
- Department of Biochemistry,
- Department of Ophthalmology and Institute for Vision Research
| | - Amy Lee
- Department of Molecular Physiology and Biophysics,
- Department of Otolaryngology-Head and Neck Surgery
- Department of Neurology, University of Iowa, Iowa City, Iowa 52242
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55
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Waldner DM, Bech-Hansen NT, Stell WK. Channeling Vision: Ca V1.4-A Critical Link in Retinal Signal Transmission. BIOMED RESEARCH INTERNATIONAL 2018; 2018:7272630. [PMID: 29854783 PMCID: PMC5966690 DOI: 10.1155/2018/7272630] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 02/15/2018] [Indexed: 01/09/2023]
Abstract
Voltage-gated calcium channels (VGCC) are key to many biological functions. Entry of Ca2+ into cells is essential for initiating or modulating important processes such as secretion, cell motility, and gene transcription. In the retina and other neural tissues, one of the major roles of Ca2+-entry is to stimulate or regulate exocytosis of synaptic vesicles, without which synaptic transmission is impaired. This review will address the special properties of one L-type VGCC, CaV1.4, with particular emphasis on its role in transmission of visual signals from rod and cone photoreceptors (hereafter called "photoreceptors," to the exclusion of intrinsically photoreceptive retinal ganglion cells) to the second-order retinal neurons, and the pathological effects of mutations in the CACNA1F gene which codes for the pore-forming α1F subunit of CaV1.4.
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Affiliation(s)
- D. M. Waldner
- Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - N. T. Bech-Hansen
- Department of Medical Genetics and Department of Surgery, Alberta Children's Hospital Research Institute, and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - W. K. Stell
- Department of Cell Biology and Anatomy and Department of Surgery, Hotchkiss Brain Institute, and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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56
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Waldner DM, Giraldo Sierra NC, Bonfield S, Nguyen L, Dimopoulos IS, Sauvé Y, Stell WK, Bech-Hansen NT. Cone dystrophy and ectopic synaptogenesis in a Cacna1f loss of function model of congenital stationary night blindness (CSNB2A). Channels (Austin) 2018; 12:17-33. [PMID: 29179637 PMCID: PMC5972796 DOI: 10.1080/19336950.2017.1401688] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/22/2017] [Accepted: 10/31/2017] [Indexed: 01/05/2023] Open
Abstract
Congenital stationary night blindness 2A (CSNB2A) is an X-linked retinal disorder, characterized by phenotypically variable signs and symptoms of impaired vision. CSNB2A is due to mutations in CACNA1F, which codes for the pore-forming α1F subunit of a L-type voltage-gated calcium channel, Cav1.4. Mouse models of CSNB2A, used for characterizing the effects of various Cacna1f mutations, have revealed greater severity of defects than in human CSNB2A. Specifically, Cacna1f-knockout mice show an apparent lack of visual function, gradual retinal degeneration, and disruption of photoreceptor synaptic terminals. Several reports have also noted cone-specific disruptions, including axonal abnormalities, dystrophy, and cell death. We have explored further the involvement of cones in our 'G305X' mouse model of CSNB2A, which has a premature truncation, loss-of-function mutation in Cacna1f. We show that the expression of genes for several phototransduction-related cone markers is down-regulated, while that of several cellular stress- and damage-related markers is up-regulated; and that cone photoreceptor structure and photopic visual function - measured by immunohistochemistry, optokinetic response and electroretinography - deteriorate progressively with age. We also find that dystrophic cone axons establish synapse-like contacts with rod bipolar cell dendrites, which they normally do not contact in wild-type retinas - ectopically, among rod cell bodies in the outer nuclear layer. These data support a role for Cav1.4 in cone synaptic development, cell viability, and synaptic transmission of cone-dependent visual signals. Although our novel finding of cone-to-rod-bipolar cell contacts in this mouse model of a retinal channelopathy may challenge current views of the role of Cav1.4 in photopic vision, it also suggests a potential new target for restorative therapy.
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Affiliation(s)
- D. M. Waldner
- Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - N. C. Giraldo Sierra
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - S. Bonfield
- Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - L. Nguyen
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - I. S. Dimopoulos
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Y. Sauvé
- Department of Ophthalmology and Visual Sciences, University of Alberta, Edmonton, Alberta, Canada
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - W. K. Stell
- Department of Cell Biology and Anatomy and Department of Surgery, Hotchkiss Brain Institute, and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - N. T. Bech-Hansen
- Department of Medical Genetics, and Department of Surgery, Alberta Children's Hospital Research Institute, and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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57
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Abstract
Synaptic communication requires alignment of transmitter release sites with transmitter receptors. In this issue of Neuron, Wang et al. (2017) show that α2δ4 subunits link calcium channels to a trans-synaptic complex with glutamate receptors at the visual system's first synapse.
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58
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Shi L, Ko ML, Ko GYP. Retinoschisin Facilitates the Function of L-Type Voltage-Gated Calcium Channels. Front Cell Neurosci 2017; 11:232. [PMID: 28848397 PMCID: PMC5550728 DOI: 10.3389/fncel.2017.00232] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/25/2017] [Indexed: 11/18/2022] Open
Abstract
Modulation of ion channels by extracellular proteins plays critical roles in shaping synaptic plasticity. Retinoschisin (RS1) is an extracellular adhesive protein secreted from photoreceptors and bipolar cells, and it plays an important role during retinal development, as well as in maintaining the stability of retinal layers. RS1 is known to form homologous octamers and interact with molecules on the plasma membrane including phosphatidylserine, sodium-potassium exchanger complex, and L-type voltage-gated calcium channels (LTCCs). However, how this physical interaction between RS1 and ion channels might affect the channel gating properties is unclear. In retinal photoreceptors, two major LTCCs are Cav1.3 (α1D) and Cav1.4 (α1F) with distinct biophysical properties, functions and distributions. Cav1.3 is distributed from the inner segment (IS) to the synaptic terminal and is responsible for calcium influx to the photoreceptors and overall calcium homeostasis. Cav1.4 is only expressed at the synaptic terminal and is responsible for neurotransmitter release. Mutations of the gene encoding Cav1.4 cause X-linked incomplete congenital stationary night blindness type 2 (CSNB2), while null mutations of Cav1.3 cause a mild decrease of retinal light responses in mice. Even though RS1 is known to maintain retinal architecture, in this study, we present that RS1 interacts with both Cav1.3 and Cav1.4 and regulates their activations. RS1 was able to co-immunoprecipitate with Cav1.3 and Cav1.4 from porcine retinas, and it increased the LTCC currents and facilitated voltage-dependent activation in HEK cells co-transfected with RS1 and Cav1.3 or Cav1.4, thus providing evidence of a functional interaction between RS1 and LTCCs. The interaction between RS1 and Cav1.3 did not change the calcium-dependent inactivation of Cav1.3. In mice lacking RS1, the expression of Cav1.3 and Cav1.4 in the retina decreased, while in mice with Cav1.4 deletion, the retinal level of RS1 decreased. These results provide important evidence that RS1 is not only an adhesive protein promoting cell-cell adhesion, it is essential for anchoring other membrane proteins including ion channels and enhancing their function in the retina.
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Affiliation(s)
- Liheng Shi
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M UniversityCollege Station, TX, United States
| | - Michael L Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M UniversityCollege Station, TX, United States
| | - Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M UniversityCollege Station, TX, United States.,Texas A&M Institute for Neuroscience, Texas A&M UniversityCollege Station, TX, United States
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59
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Martemyanov KA, Sampath AP. The Transduction Cascade in Retinal ON-Bipolar Cells: Signal Processing and Disease. Annu Rev Vis Sci 2017; 3:25-51. [PMID: 28715957 DOI: 10.1146/annurev-vision-102016-061338] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Our robust visual experience is based on the reliable transfer of information from our photoreceptor cells, the rods and cones, to higher brain centers. At the very first synapse of the visual system, information is split into two separate pathways, ON and OFF, which encode increments and decrements in light intensity, respectively. The importance of this segregation is borne out in the fact that receptive fields in higher visual centers maintain a separation between ON and OFF regions. In the past decade, the molecular mechanisms underlying the generation of ON signals have been identified, which are unique in their use of a G-protein signaling cascade. In this review, we consider advances in our understanding of G-protein signaling in ON-bipolar cell (BC) dendrites and how insights about signaling have emerged from visual deficits, mostly night blindness. Studies of G-protein signaling in ON-BCs reveal an intricate mechanism that permits the regulation of visual sensitivity over a wide dynamic range.
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Affiliation(s)
| | - Alapakkam P Sampath
- Jules Stein Eye Institute, University of California, Los Angeles, California 90095;
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60
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Grassmeyer JJ, Thoreson WB. Synaptic Ribbon Active Zones in Cone Photoreceptors Operate Independently from One Another. Front Cell Neurosci 2017; 11:198. [PMID: 28744203 PMCID: PMC5504102 DOI: 10.3389/fncel.2017.00198] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 06/26/2017] [Indexed: 12/04/2022] Open
Abstract
Cone photoreceptors depolarize in darkness to release glutamate-laden synaptic vesicles. Essential to release is the synaptic ribbon, a structure that helps organize active zones by clustering vesicles near proteins that mediate exocytosis, including voltage-gated Ca2+ channels. Cone terminals have many ribbon-style active zones at which second-order neurons receive input. We asked whether there are functionally significant differences in local Ca2+ influx among ribbons in individual cones. We combined confocal Ca2+ imaging to measure Ca2+ influx at individual ribbons and patch clamp recordings to record whole-cell ICa in salamander cones. We found that the voltage for half-maximal activation (V50) of whole cell ICa in cones averaged −38.1 mV ± 3.05 mV (standard deviation [SD]), close to the cone membrane potential in darkness of ca. −40 mV. Ca2+ signals at individual ribbons varied in amplitude from one another and showed greater variability in V50 values than whole-cell ICa, suggesting that Ca2+ signals can differ significantly among ribbons within cones. After accounting for potential sources of technical variability in measurements of Ca2+ signals and for contributions from cone-to-cone differences in ICa, we found that the variability in V50 values for ribbon Ca2+ signals within individual cones showed a SD of 2.5 mV. Simulating local differences in Ca2+ channel activity at two ribbons by shifting the V50 value of ICa by ±2.5 mV (1 SD) about the mean suggests that when the membrane depolarizes to −40 mV, two ribbons could experience differences in Ca2+ influx of >45%. Further evidence that local Ca2+ changes at ribbons can be regulated independently was obtained in experiments showing that activation of inhibitory feedback from horizontal cells (HCs) to cones in paired recordings changed both amplitude and V50 of Ca2+ signals at individual ribbons. By varying the strength of synaptic output, differences in voltage dependence and amplitude of Ca2+ signals at individual ribbons shape the information transmitted from cones to downstream neurons in vision.
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Affiliation(s)
- Justin J Grassmeyer
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical CenterOmaha, NE, United States.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical CenterOmaha, NE, United States
| | - Wallace B Thoreson
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical CenterOmaha, NE, United States.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical CenterOmaha, NE, United States
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61
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Seitter H, Koschak A. Relevance of tissue specific subunit expression in channelopathies. Neuropharmacology 2017; 132:58-70. [PMID: 28669898 DOI: 10.1016/j.neuropharm.2017.06.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 06/22/2017] [Accepted: 06/28/2017] [Indexed: 12/27/2022]
Abstract
Channelopathies are a diverse group of human disorders that are caused by mutations in genes coding for ion channels or channel-regulating proteins. Several dozen channelopathies have been identified that involve both non-excitable cells as well as electrically active tissues like brain, skeletal and smooth muscle or the heart. In this review, we start out from the general question which ion channel genes are expressed tissue-selectively. We mined the human gene expression database Human Protein Atlas (HPA) for tissue-enriched ion channel genes and found 85 genes belonging to the ion channel families. Most of these genes were enriched in brain, testis and muscle and a complete list of the enriched ion channel genes is provided. We further focused on the tissue distribution of voltage-gated calcium channel (VGCC) genes including different brain areas and the retina based on the human gene expression from the FANTOM5 dataset. The expression data is complemented by an overview of the tissue-dependent aspects of L-type calcium channel (LTCC) function, dysfunction and pharmacology, as well as of their splice variants. Finally, we focus on the pathology of tissue-restricted LTCC channelopathies and their treatment options. This article is part of the Special Issue entitled 'Channelopathies.'
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Affiliation(s)
- Hartwig Seitter
- University of Innsbruck, Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, Innrain 80-82/III, 6020 Innsbruck, Austria
| | - Alexandra Koschak
- University of Innsbruck, Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, Innrain 80-82/III, 6020 Innsbruck, Austria.
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62
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Hove MN, Kilic-Biyik KZ, Trotter A, Grønskov K, Sander B, Larsen M, Carroll J, Bech-Hansen T, Rosenberg T. Clinical Characteristics, Mutation Spectrum, and Prevalence of Åland Eye Disease/Incomplete Congenital Stationary Night Blindness in Denmark. Invest Ophthalmol Vis Sci 2017; 57:6861-6869. [PMID: 28002560 PMCID: PMC5215230 DOI: 10.1167/iovs.16-19445] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To assess clinical characteristics, foveal structure, mutation spectrum, and prevalence rate of Åland eye disease (AED)/incomplete congenital stationary night blindness (iCSNB). Methods A retrospective survey included individuals diagnosed with AED at a national low-vision center from 1980 to 2014. A subset of affected males underwent ophthalmologic examinations including psychophysical tests, full-field electroretinography, and spectral-domain optical coherence tomography. Results Over the 34-year period, 74 individuals from 35 families were diagnosed with AED. Sixty individuals from 29 families participated in a follow-up study of whom 59 harbored a CACNA1F mutation and 1 harbored a CABP4 mutation. Among the subjects with a CACNA1F mutation, subnormal visual acuity was present in all, nystagmus was present in 63%, and foveal hypoplasia was observed in 25/43 subjects. Foveal pit volume was significantly reduced as compared to normal (P < 0.0001). Additionally, outer segment length at the fovea was measured in 46 subjects and found to be significantly reduced as compared to normal (P < 0.001). Twenty-nine CACNA1F variations were detected among 34 families in the total cohort, and a novel CABP4 variation was identified in one family. The estimated mean birth prevalence rate was 1 per 22,000 live-born males. Conclusions Our data support the viewpoint that AED, iCSNB, and X-linked cone–rod dystrophy 3 are designations that refer to a broad, continuous spectrum of clinical appearances caused in the majority by a variety of mutations in CACNA1F. We argue that the original designation AED should be used for this entity.
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Affiliation(s)
- Marianne N Hove
- Department of Ophthalmology, National Eye Clinic for the Visually Impaired and Kennedy Center, Rigshospitalet, Glostrup, Denmark 2Department of Ophthalmology, Rigshospitalet, Glostrup, Denmark
| | - Kevser Z Kilic-Biyik
- Department of Ophthalmology, Rigshospitalet, Glostrup, Denmark 3Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alana Trotter
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Karen Grønskov
- Clinical Genetic Clinic, Kennedy Center, Rigshospitalet, Copenhagen, Denmark
| | - Birgit Sander
- Department of Ophthalmology, Rigshospitalet, Glostrup, Denmark 3Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Michael Larsen
- Department of Ophthalmology, National Eye Clinic for the Visually Impaired and Kennedy Center, Rigshospitalet, Glostrup, Denmark 2Department of Ophthalmology, Rigshospitalet, Glostrup, Denmark 3Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Joseph Carroll
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Torben Bech-Hansen
- Department of Medical Genetics, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Thomas Rosenberg
- Department of Ophthalmology, National Eye Clinic for the Visually Impaired and Kennedy Center, Rigshospitalet, Glostrup, Denmark 3Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Peachey NS, Hasan N, FitzMaurice B, Burrill S, Pangeni G, Karst SY, Reinholdt L, Berry ML, Strobel M, Gregg RG, McCall MA, Chang B. A missense mutation in Grm6 reduces but does not eliminate mGluR6 expression or rod depolarizing bipolar cell function. J Neurophysiol 2017; 118:845-854. [PMID: 28490646 DOI: 10.1152/jn.00888.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 05/03/2017] [Accepted: 05/03/2017] [Indexed: 01/01/2023] Open
Abstract
GRM6 encodes the metabotropic glutamate receptor 6 (mGluR6) used by retinal depolarizing bipolar cells (DBCs). Mutations in GRM6 lead to DBC dysfunction and underlie the human condition autosomal recessive complete congenital stationary night blindness. Mouse mutants for Grm6 are important models for this condition. Here we report a new Grm6 mutant, identified in an electroretinogram (ERG) screen of mice maintained at The Jackson Laboratory. The Grm6nob8 mouse has a reduced-amplitude b-wave component of the ERG, which reflects light-evoked DBC activity. Sequencing identified a missense mutation that converts a highly conserved methionine within the ligand binding domain to leucine (p.Met66Leu). Consistent with prior studies of Grm6 mutant mice, the laminar size and structure in the Grm6nob8 retina were comparable to control. The Grm6nob8 phenotype is distinguished from other Grm6 mutants that carry a null allele by a reduced but not absent ERG b-wave, decreased but present expression of mGluR6 at DBC dendritic tips, and mislocalization of mGluR6 to DBC somas. Consistent with a reduced but not absent b-wave, there were a subset of retinal ganglion cells whose responses to light onset have times to peak within the range of those in control retinas. These data indicate that the p.Met66Leu mutant mGluR6 is trafficked less than control. However, the mGluR6 that is localized to the DBC dendritic tips is able to initiate DBC signal transduction. The Grm6nob8 mouse extends the Grm6 allelic series and will be useful for elucidating the role of mGluR6 in DBC signal transduction and in human disease.NEW & NOTEWORTHY This article describes a mouse model of the human disease complete congenital stationary night blindness in which the mutation reduces but does not eliminate GRM6 expression and bipolar cell function, a distinct phenotype from that seen in other Grm6 mouse models.
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Affiliation(s)
- Neal S Peachey
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio.,Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio.,Department of Ophthalmology, Cleveland Clinic College of Medicine of Case Western Reserve University, Cleveland, Ohio
| | - Nazarul Hasan
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, Kentucky
| | | | | | - Gobinda Pangeni
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky; and
| | | | | | | | | | - Ronald G Gregg
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, Kentucky.,Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky; and
| | - Maureen A McCall
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky; and.,Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, Maine;
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Broadgate S, Yu J, Downes SM, Halford S. Unravelling the genetics of inherited retinal dystrophies: Past, present and future. Prog Retin Eye Res 2017; 59:53-96. [PMID: 28363849 DOI: 10.1016/j.preteyeres.2017.03.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 03/21/2017] [Accepted: 03/23/2017] [Indexed: 02/07/2023]
Abstract
The identification of the genes underlying monogenic diseases has been of interest to clinicians and scientists for many years. Using inherited retinal dystrophies as an example of monogenic disease we describe the history of molecular genetic techniques that have been pivotal in the discovery of disease causing genes. The methods that were developed in the 1970's and 80's are still in use today but have been refined and improved. These techniques enabled the concept of the Human Genome Project to be envisaged and ultimately realised. When the successful conclusion of the project was announced in 2003 many new tools and, as importantly, many collaborations had been developed that facilitated a rapid identification of disease genes. In the post-human genome project era advances in computing power and the clever use of the properties of DNA replication has allowed the development of next-generation sequencing technologies. These methods have revolutionised the identification of disease genes because for the first time there is no need to define the position of the gene in the genome. The use of next generation sequencing in a diagnostic setting has allowed many more patients with an inherited retinal dystrophy to obtain a molecular diagnosis for their disease. The identification of novel genes that have a role in the development or maintenance of retinal function is opening up avenues of research which will lead to the development of new pharmacological and gene therapy approaches. Neither of which can be used unless the defective gene and protein is known. The continued development of sequencing technologies also holds great promise for the advent of truly personalised medicine.
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Affiliation(s)
- Suzanne Broadgate
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Levels 5 and 6 West Wing, John Radcliffe Hospital, Headley Way, Oxford, OX3 9DU, UK
| | - Jing Yu
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Levels 5 and 6 West Wing, John Radcliffe Hospital, Headley Way, Oxford, OX3 9DU, UK
| | - Susan M Downes
- Oxford Eye Hospital, Oxford University Hospitals NHS Trust, Oxford, OX3 9DU, UK
| | - Stephanie Halford
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Levels 5 and 6 West Wing, John Radcliffe Hospital, Headley Way, Oxford, OX3 9DU, UK.
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Wang Y, Fehlhaber KE, Sarria I, Cao Y, Ingram NT, Guerrero-Given D, Throesch B, Baldwin K, Kamasawa N, Ohtsuka T, Sampath AP, Martemyanov KA. The Auxiliary Calcium Channel Subunit α2δ4 Is Required for Axonal Elaboration, Synaptic Transmission, and Wiring of Rod Photoreceptors. Neuron 2017; 93:1359-1374.e6. [PMID: 28262416 PMCID: PMC5364038 DOI: 10.1016/j.neuron.2017.02.021] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 12/31/2016] [Accepted: 02/08/2017] [Indexed: 11/24/2022]
Abstract
Neural circuit wiring relies on selective synapse formation whereby a presynaptic release apparatus is matched with its cognate postsynaptic machinery. At metabotropic synapses, the molecular mechanisms underlying this process are poorly understood. In the mammalian retina, rod photoreceptors form selective contacts with rod ON-bipolar cells by aligning the presynaptic voltage-gated Ca2+ channel directing glutamate release (CaV1.4) with postsynaptic mGluR6 receptors. We show this coordination requires an extracellular protein, α2δ4, which complexes with CaV1.4 and the rod synaptogenic mediator, ELFN1, for trans-synaptic alignment with mGluR6. Eliminating α2δ4 in mice abolishes rod synaptogenesis and synaptic transmission to rod ON-bipolar cells, and disrupts postsynaptic mGluR6 clustering. We further find that in rods, α2δ4 is crucial for organizing synaptic ribbons and setting CaV1.4 voltage sensitivity. In cones, α2δ4 is essential for CaV1.4 function, but is not required for ribbon organization, synaptogenesis, or synaptic transmission. These findings offer insights into retinal pathologies associated with α2δ4 dysfunction.
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Affiliation(s)
- Yuchen Wang
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Katherine E Fehlhaber
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ignacio Sarria
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Yan Cao
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Norianne T Ingram
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Debbie Guerrero-Given
- Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Ben Throesch
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92121, USA
| | - Kristin Baldwin
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92121, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Toshihisa Ohtsuka
- Department of Biochemistry, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Alapakkam P Sampath
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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Lack of CaBP1/Caldendrin or CaBP2 Leads to Altered Ganglion Cell Responses. eNeuro 2016; 3:eN-NWR-0099-16. [PMID: 27822497 PMCID: PMC5083949 DOI: 10.1523/eneuro.0099-16.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 09/24/2016] [Accepted: 10/08/2016] [Indexed: 12/01/2022] Open
Abstract
Calcium-binding proteins (CaBPs) form a subfamily of calmodulin-like proteins that were cloned from the retina. CaBP4 and CaBP5 have been shown to be important for normal visual function. Although CaBP1/caldendrin and CaBP2 have been shown to modulate various targets in vitro, it is not known whether they contribute to the transmission of light responses through the retina. Therefore, we generated mice that lack CaBP2 or CaBP1/caldendrin (Cabp2–/– and Cabp1–/–) to test whether these CaBPs are essential for normal retinal function. By immunohistochemistry, the overall morphology of Cabp1–/– and Cabp2–/– retinas and the number of synaptic ribbons appear normal; transmission electron microscopy shows normal tethered ribbon synapses and synaptic vesicles as in wild-type retinas. However, whole-cell patch clamp recordings showed that light responses of retinal ganglion cells of Cabp2–/– and Cabp1–/– mice differ in amplitude and kinetics from those of wild-type mice. We conclude that CaBP1/caldendrin and CaBP2 are not required for normal gross retinal and synapse morphology but are necessary for the proper transmission of light responses through the retina; like other CaBPs, CaBP1/caldendrin and CaBP2 likely act by modulating presynaptic Ca2+-dependent signaling mechanisms.
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Kinetics of Inhibitory Feedback from Horizontal Cells to Photoreceptors: Implications for an Ephaptic Mechanism. J Neurosci 2016; 36:10075-88. [PMID: 27683904 DOI: 10.1523/jneurosci.1090-16.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 08/12/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Inhibitory feedback from horizontal cells (HCs) to cones generates center-surround receptive fields and color opponency in the retina. Mechanisms of HC feedback remain unsettled, but one hypothesis proposes that an ephaptic mechanism may alter the extracellular electrical field surrounding photoreceptor synaptic terminals, thereby altering Ca(2+) channel activity and photoreceptor output. An ephaptic voltage change produced by current flowing through open channels in the HC membrane should occur with no delay. To test for this mechanism, we measured kinetics of inhibitory feedback currents in Ambystoma tigrinum cones and rods evoked by hyperpolarizing steps applied to synaptically coupled HCs. Hyperpolarizing HCs stimulated inward feedback currents in cones that averaged 8-9 pA and exhibited a biexponential time course with time constants averaging 14-17 ms and 120-220 ms. Measurement of feedback-current kinetics was limited by three factors: (1) HC voltage-clamp speed, (2) cone voltage-clamp speed, and (3) kinetics of Ca(2+) channel activation or deactivation in the photoreceptor terminal. These factors totaled ∼4-5 ms in cones meaning that the true fast time constants for HC-to-cone feedback currents were 9-13 ms, slower than expected for ephaptic voltage changes. We also compared speed of feedback to feedforward glutamate release measured at the same cone/HC synapses and found a latency for feedback of 11-14 ms. Inhibitory feedback from HCs to rods was also significantly slower than either measurement kinetics or feedforward release. The finding that inhibitory feedback from HCs to photoreceptors involves a significant delay indicates that it is not due to previously proposed ephaptic mechanisms. SIGNIFICANCE STATEMENT Lateral inhibitory feedback from horizontal cells (HCs) to photoreceptors creates center-surround receptive fields and color-opponent interactions. Although underlying mechanisms remain unsettled, a longstanding hypothesis proposes that feedback is due to ephaptic voltage changes that regulate photoreceptor synaptic output by altering Ca(2+) channel activity. Ephaptic processes should occur with no delay. We measured kinetics of inhibitory feedback currents evoked in photoreceptors with voltage steps applied to synaptically coupled HCs and found that feedback is too slow to be explained by ephaptic voltage changes generated by current flowing through continuously open channels in HC membranes. By eliminating the proposed ephaptic mechanism for HC feedback regulation of photoreceptor Ca(2+) channels, our data support earlier proposals that synaptic cleft pH changes are more likely responsible.
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68
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Dolphin AC. Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology. J Physiol 2016; 594:5369-90. [PMID: 27273705 PMCID: PMC5043047 DOI: 10.1113/jp272262] [Citation(s) in RCA: 208] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/09/2016] [Indexed: 12/22/2022] Open
Abstract
Voltage‐gated calcium channels are essential players in many physiological processes in excitable cells. There are three main subdivisions of calcium channel, defined by the pore‐forming α1 subunit, the CaV1, CaV2 and CaV3 channels. For all the subtypes of voltage‐gated calcium channel, their gating properties are key for the precise control of neurotransmitter release, muscle contraction and cell excitability, among many other processes. For the CaV1 and CaV2 channels, their ability to reach their required destinations in the cell membrane, their activation and the fine tuning of their biophysical properties are all dramatically influenced by the auxiliary subunits that associate with them. Furthermore, there are many diseases, both genetic and acquired, involving voltage‐gated calcium channels. This review will provide a general introduction and then concentrate particularly on the role of auxiliary α2δ subunits in both physiological and pathological processes involving calcium channels, and as a therapeutic target.
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Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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69
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Haeseleer F, Williams B, Lee A. Characterization of C-terminal Splice Variants of Cav1.4 Ca2+ Channels in Human Retina. J Biol Chem 2016; 291:15663-73. [PMID: 27226626 DOI: 10.1074/jbc.m116.731737] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated Ca(2+) channels (Cav) undergo extensive alternative splicing that greatly enhances their functional diversity in excitable cells. Here, we characterized novel splice variants of the cytoplasmic C-terminal domain of Cav1.4 Ca(2+) channels that regulate neurotransmitter release in photoreceptors in the retina. These variants lack a portion of exon 45 and/or the entire exon 47 (Cav1.4Δex p45, Cav1.4Δex 47, Cav1.4Δex p45,47) and are expressed in the retina of primates but not mice. Although the electrophysiological properties of Cav1.4Δex p45 are similar to those of full-length channels (Cav1.4FL), skipping of exon 47 dramatically alters Cav1.4 function. Deletion of exon 47 removes part of a C-terminal automodulatory domain (CTM) previously shown to suppress Ca(2+)-dependent inactivation (CDI) and to cause a positive shift in the voltage dependence of channel activation. Exon 47 is crucial for these effects of the CTM because variants lacking this exon show intense CDI and activate at more hyperpolarized voltages than Cav1.4FL The robust CDI of Cav1.4Δex 47 is suppressed by CaBP4, a regulator of Cav1.4 channels in photoreceptors. Although CaBP4 enhances activation of Cav1.4FL, Cav1.4Δex 47 shows similar voltage-dependent activation in the presence and absence of CaBP4. We conclude that exon 47 encodes structural determinants that regulate CDI and voltage-dependent activation of Cav1.4, and is necessary for modulation of channel activation by CaBP4.
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Affiliation(s)
- Françoise Haeseleer
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195 and
| | - Brittany Williams
- the Departments of Molecular Physiology and Biophysics, Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa 52242
| | - Amy Lee
- the Departments of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, Neurology, and
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70
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The developmental effects of pentachlorophenol on zebrafish embryos during segmentation: A systematic view. Sci Rep 2016; 6:25929. [PMID: 27181905 PMCID: PMC4867433 DOI: 10.1038/srep25929] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/25/2016] [Indexed: 11/26/2022] Open
Abstract
Pentachlorophenol (PCP) is a typical toxicant and prevailing pollutant whose toxicity has been broadly investigated. However, previous studies did not specifically investigate the underlying mechanisms of its developmental toxicity. Here, we chose zebrafish embryos as the model, exposed them to 2 different concentrations of PCP, and sequenced their entire transcriptomes at 10 and 24 hours post-fertilization (hpf). The sequencing analysis revealed that high concentrations of PCP elicited systematic responses at both time points. By combining the enrichment terms with single genes, the results were further analyzed using three categories: metabolism, transporters, and organogenesis. Hyperactive glycolysis was the most outstanding feature of the transcriptome at 10 hpf. The entire system seemed to be hypoxic, although hypoxia-inducible factor-1α (HIF1α) may have been suppressed by the upregulation of prolyl hydroxylase domain enzymes (PHDs). At 24 hpf, PCP primarily affected somitogenesis and lens formation probably resulting from the disruption of embryonic body plan at earlier stages. The proposed underlying toxicological mechanism of PCP was based on the crosstalk between each clue. Our study attempted to describe the developmental toxicity of environmental pollutants from a systematic view. Meanwhile, some features of gene expression profiling could serve as markers of human health or ecological risk.
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71
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Novel DLK-independent neuronal regeneration in Caenorhabditis elegans shares links with activity-dependent ectopic outgrowth. Proc Natl Acad Sci U S A 2016; 113:E2852-60. [PMID: 27078101 DOI: 10.1073/pnas.1600564113] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
During development, a neuron transitions from a state of rapid growth to a stable morphology, and neurons within the adult mammalian CNS lose their ability to effectively regenerate in response to injury. Here, we identify a novel form of neuronal regeneration, which is remarkably independent of DLK-1/DLK, KGB-1/JNK, and other MAPK signaling factors known to mediate regeneration in Caenorhabditis elegans, Drosophila, and mammals. This DLK-independent regeneration in C. elegans has direct genetic and molecular links to a well-studied form of endogenous activity-dependent ectopic axon outgrowth in the same neuron type. Both neuron outgrowth types are triggered by physical lesion of the sensory dendrite or mutations disrupting sensory activity, calcium signaling, or genes that restrict outgrowth during neuronal maturation, such as SAX-1/NDR kinase or UNC-43/CaMKII. These connections suggest that ectopic outgrowth represents a powerful platform for gene discovery in neuronal regeneration. Moreover, we note numerous similarities between C. elegans DLK-independent regeneration and lesion conditioning, a phenomenon producing robust regeneration in the mammalian CNS. Both regeneration types are triggered by lesion of a sensory neurite via reduction of neuronal activity and enhanced by disrupting L-type calcium channels or elevating cAMP. Taken as a whole, our study unites disparate forms of neuronal outgrowth to uncover fresh molecular insights into activity-dependent control of the adult nervous system's intrinsic regenerative capacity.
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72
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Jones BW, Pfeiffer RL, Ferrell WD, Watt CB, Marmor M, Marc RE. Retinal remodeling in human retinitis pigmentosa. Exp Eye Res 2016; 150:149-65. [PMID: 27020758 DOI: 10.1016/j.exer.2016.03.018] [Citation(s) in RCA: 216] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 02/23/2016] [Accepted: 03/18/2016] [Indexed: 12/11/2022]
Abstract
Retinitis Pigmentosa (RP) in the human is a progressive, currently irreversible neural degenerative disease usually caused by gene defects that disrupt the function or architecture of the photoreceptors. While RP can initially be a disease of photoreceptors, there is increasing evidence that the inner retina becomes progressively disorganized as the outer retina degenerates. These alterations have been extensively described in animal models, but remodeling in humans has not been as well characterized. This study, using computational molecular phenotyping (CMP) seeks to advance our understanding of the retinal remodeling process in humans. We describe cone mediated preservation of overall topology, retinal reprogramming in the earliest stages of the disease in retinal bipolar cells, and alterations in both small molecule and protein signatures of neurons and glia. Furthermore, while Müller glia appear to be some of the last cells left in the degenerate retina, they are also one of the first cell classes in the neural retina to respond to stress which may reveal mechanisms related to remodeling and cell death in other retinal cell classes. Also fundamentally important is the finding that retinal network topologies are altered. Our results suggest interventions that presume substantial preservation of the neural retina will likely fail in late stages of the disease. Even early intervention offers no guarantee that the interventions will be immune to progressive remodeling. Fundamental work in the biology and mechanisms of disease progression are needed to support vision rescue strategies.
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Affiliation(s)
- B W Jones
- Dept. Ophthalmology, Moran Eye Center, University of Utah, USA.
| | - R L Pfeiffer
- Dept. Ophthalmology, Moran Eye Center, University of Utah, USA
| | - W D Ferrell
- Dept. Ophthalmology, Moran Eye Center, University of Utah, USA
| | - C B Watt
- Dept. Ophthalmology, Moran Eye Center, University of Utah, USA
| | - M Marmor
- Dept. Ophthalmology, Stanford University, USA
| | - R E Marc
- Dept. Ophthalmology, Moran Eye Center, University of Utah, USA
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Li S, Mitchell J, Briggs DJ, Young JK, Long SS, Fuerst PG. Morphological Diversity of the Rod Spherule: A Study of Serially Reconstructed Electron Micrographs. PLoS One 2016; 11:e0150024. [PMID: 26930660 PMCID: PMC4773090 DOI: 10.1371/journal.pone.0150024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 02/08/2016] [Indexed: 11/25/2022] Open
Abstract
Purpose Rod spherules are the site of the first synaptic contact in the retina’s rod pathway, linking rods to horizontal and bipolar cells. Rod spherules have been described and characterized through electron micrograph (EM) and other studies, but their morphological diversity related to retinal circuitry and their intracellular structures have not been quantified. Most rod spherules are connected to their soma by an axon, but spherules of rods on the surface of the Mus musculus outer plexiform layer often lack an axon and have a spherule structure that is morphologically distinct from rod spherules connected to their soma by an axon. Retraction of the rod axon and spherule is often observed in disease processes and aging, and the retracted rod spherule superficially resembles rod spherules lacking an axon. We hypothesized that retracted spherules take on an axonless spherule morphology, which may be easier to maintain in a diseased state. To test our hypothesis, we quantified the spatial organization and subcellular structures of rod spherules with and without axons. We then compared them to the retracted spherules in a disease model, mice that overexpress Dscam (Down syndrome cell adhesion molecule), to gain a better understanding of the rod synapse in health and disease. Methods We reconstructed serial EM images of wild type and DscamGoF (gain of function) rod spherules at a resolution of 7 nm in the X-Y axis and 60 nm in the Z axis. Rod spherules with and without axons, and retracted spherules in the DscamGoF retina, were reconstructed. The rod spherule intracellular organelles, the invaginating dendrites of rod bipolar cells and horizontal cell axon tips were also reconstructed for statistical analysis. Results Stereotypical rod (R1) spherules occupy the outer two-thirds of the outer plexiform layer (OPL), where they present as spherical terminals with large mitochondria. This spherule group is highly uniform and composed more than 90% of the rod spherule population. Rod spherules lacking an axon (R2) were also described and characterized. This rod spherule group consists of a specific spatial organization that is strictly located at the apical OPL-facing layer of the Outer Nuclear Layer (ONL). The R2 spherule displays a large bowl-shaped synaptic terminal that hugs the rod soma. Retracted spherules in the DscamGoF retina were also reconstructed to test if they are structurally similar to R2 spherules. The misplaced rod spherules in DscamGoF have a gross morphology that is similar to R2 spherules but have significant disruption in internal synapse organization. Conclusion We described a morphological diversity within Mus musculus rod spherules. This diversity is correlated with rod location in the ONL and contributes to the intracellular differences within spherules. Analysis of the DscamGoF retina indicated that their R2 spherules are not significantly different than wild type R2 spherules, but that their retracted rod spherules have abnormal synaptic organization.
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Affiliation(s)
- Shuai Li
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, 83844, United States of America
| | - Joe Mitchell
- North Idaho College, Natural Sciences Division, Coeur d’Alene, Idaho, 83814, United States of America
| | - Deidrie J. Briggs
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, 83844, United States of America
| | - Jaime K. Young
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, 83844, United States of America
| | - Samuel S. Long
- Lewis-Clark State College, Department of Computer Sciences, Lewiston, Idaho, 83501, United States of America
| | - Peter G. Fuerst
- University of Idaho, Department of Biological Sciences, Moscow, Idaho, 83844, United States of America
- WWAMI Medical Education Program, Moscow, Idaho, 83844, United States of America
- * E-mail:
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74
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Giblin JP, Comes N, Strauss O, Gasull X. Ion Channels in the Eye: Involvement in Ocular Pathologies. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2015; 104:157-231. [PMID: 27038375 DOI: 10.1016/bs.apcsb.2015.11.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The eye is the sensory organ of vision. There, the retina transforms photons into electrical signals that are sent to higher brain areas to produce visual sensations. In the light path to the retina, different types of cells and tissues are involved in maintaining the transparency of avascular structures like the cornea or lens, while others, like the retinal pigment epithelium, have a critical role in the maintenance of photoreceptor function by regenerating the visual pigment. Here, we have reviewed the roles of different ion channels expressed in ocular tissues (cornea, conjunctiva and neurons innervating the ocular surface, lens, retina, retinal pigment epithelium, and the inflow and outflow systems of the aqueous humor) that are involved in ocular disease pathophysiologies and those whose deletion or pharmacological modulation leads to specific diseases of the eye. These include pathologies such as retinitis pigmentosa, macular degeneration, achromatopsia, glaucoma, cataracts, dry eye, or keratoconjunctivitis among others. Several disease-associated ion channels are potential targets for pharmacological intervention or other therapeutic approaches, thus highlighting the importance of these channels in ocular physiology and pathophysiology.
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Affiliation(s)
- Jonathan P Giblin
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Nuria Comes
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | | | - Xavier Gasull
- Universitat de Barcelona, Barcelona, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
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RIM1/2-Mediated Facilitation of Cav1.4 Channel Opening Is Required for Ca2+-Stimulated Release in Mouse Rod Photoreceptors. J Neurosci 2015; 35:13133-47. [PMID: 26400943 DOI: 10.1523/jneurosci.0658-15.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Night blindness can result from impaired photoreceptor function and a subset of cases have been linked to dysfunction of Cav1.4 calcium channels and in turn compromised synaptic transmission. Here, we show that active zone proteins RIM1/2 are important regulators of Cav1.4 channel function in mouse rod photoreceptors and thus synaptic activity. The conditional double knock-out (cdko) of RIM1 and RIM2 from rods starting a few weeks after birth did not change Cav1.4 protein expression at rod ribbon synapses nor was the morphology of the ribbon altered. Heterologous overexpression of RIM2 with Cav1.4 had no significant influence on current density when examined with BaCl2 as the charge carrier. Nonetheless, whole-cell voltage-clamp recordings from cdko rods revealed a profound reduction in Ca(2+) currents. Concomitantly, we observed a 4-fold reduction in spontaneous miniature release events from the cdko rod terminals and an almost complete absence of evoked responses when monitoring changes in membrane incorporation after strong step depolarizations. Under control conditions, 49 and 83 vesicles were released with 0.2 and 1 s depolarizations, respectively, which is close to the maximal number of vesicles estimated to be docked at the base of the ribbon active zone, but without RIM1/2, only a few vesicles were stimulated for release after a 1 s stimulation. In conclusion, our study shows that RIM1/2 potently enhance the influx of Ca(2+) into rod terminals through Cav1.4 channels, which is vitally important for the release of vesicles from the rod ribbon. Significance statement: Active zone scaffolding proteins are thought to bring multiple components involved in Ca(2+)-dependent exocytosis into functional interactions. We show that removal of scaffolding proteins RIM1/2 from rod photoreceptor ribbon synapses causes a dramatic loss of Ca(2+) influx through Cav1.4 channels and a correlated reduction in evoked release, yet the channels remain localized to synaptic ribbons in a normal fashion. Our findings strongly argue that RIM1/2 facilitate Ca(2+) entry and in turn Ca(2+) evoked release by modulating Cav1.4 channel openings; however, RIM1/2 are not needed for the retention of Cav1.4 at the synapse. In summary, a key function of RIM1/2 at rod ribbons is to enhance Cav1.4 channel activity, possibly through direct or indirect modulation of the channel.
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Caputo A, Piano I, Demontis GC, Bacchi N, Casarosa S, Della Santina L, Gargini C. TMEM16A is associated with voltage-gated calcium channels in mouse retina and its function is disrupted upon mutation of the auxiliary α2δ4 subunit. Front Cell Neurosci 2015; 9:422. [PMID: 26557056 PMCID: PMC4617175 DOI: 10.3389/fncel.2015.00422] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 10/04/2015] [Indexed: 02/02/2023] Open
Abstract
Photoreceptors rely upon highly specialized synapses to efficiently transmit signals to multiple postsynaptic targets. Calcium influx in the presynaptic terminal is mediated by voltage-gated calcium channels (VGCC). This event triggers neurotransmitter release, but also gates calcium-activated chloride channels (TMEM), which in turn regulate VGCC activity. In order to investigate the relationship between VGCC and TMEM channels, we analyzed the retina of wild type (WT) and Cacna2d4 mutant mice, in which the VGCC auxiliary α2δ4 subunit carries a nonsense mutation, disrupting the normal channel function. Synaptic terminals of mutant photoreceptors are disarranged and synaptic proteins as well as TMEM16A channels lose their characteristic localization. In parallel, calcium-activated chloride currents are impaired in rods, despite unaltered TMEM16A protein levels. Co-immunoprecipitation revealed the interaction between VGCC and TMEM16A channels in the retina. Heterologous expression of these channels in tsA-201 cells showed that TMEM16A associates with the CaV1.4 subunit, and the association persists upon expression of the mutant α2δ4 subunit. Collectively, our experiments show association between TMEM16A and the α1 subunit of VGCC. Close proximity of these channels allows optimal function of the photoreceptor synaptic terminal under physiological conditions, but also makes TMEM16A channels susceptible to changes occurring to calcium channels.
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Affiliation(s)
| | - Ilaria Piano
- Department of Pharmacy, University of Pisa Pisa, Italy
| | | | - Niccolò Bacchi
- Centre for Integrative Biology, University of Trento Trento, Italy
| | - Simona Casarosa
- Centre for Integrative Biology, University of Trento Trento, Italy
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77
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Berkowitz BA, Murphy GG, Craft CM, Surmeier DJ, Roberts R. Genetic dissection of horizontal cell inhibitory signaling in mice in complete darkness in vivo. Invest Ophthalmol Vis Sci 2015; 56:3132-9. [PMID: 26024096 DOI: 10.1167/iovs.15-16581] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
PURPOSE To test the hypothesis that horizontal cell (HC) inhibitory signaling controls the degree to which rod cell membranes are depolarized as measured by the extent to which L-type calcium channels (LTCCs) are open in complete darkness in the mouse retina in vivo. METHODS Dark-adapted wild-type (wt), CACNA1F (Ca(v)1.4(-/-)), arrestin-1 (Arr1(-/-)), and CACNA1D (Ca(v)1.3(-/-)) C57Bl/6 mice were studied. Manganese-enhanced MRI (MEMRI) evaluated the extent that rod LTCCs are open as an index of loss of HC inhibitory signaling. Subgroups were pretreated with D-cis-diltiazem (DIL) at a dose that specifically antagonizes Ca(v)1.2 channels in vivo. RESULTS Knockout mice predicted to have impaired HC inhibitory signaling (Ca(v)1.4(-/-) or Arr1(-/-)) exhibited greater than normal rod manganese uptake; inner retinal uptake was also supernormal. Genetically knocking out a closely associated gene not expected to impact HC inhibitory signaling (CACNA1D) did not generate this phenotype. The Arr1(-/-) mice exhibited the largest rod uptake of manganese. Manganese-enhanced MRI of DIL-treated Arr1(-/-) mice suggested a greater number of operant LTCC subtypes (i.e., Ca(v)1.2, 1.3, and 1.4) in rods and inner retina than that in DIL-treated Ca(v)1.4(-/-) mice (i.e., Ca(v)1.3). The Ca(v)1.3(-/-) + DIL-treated mice exhibited evidence for a compensatory contribution from Ca(v)1.2 LTCCs. CONCLUSIONS The data suggest that loss of HC inhibitory signaling is the proximate cause leading to maximally open LTCCs in rods, and possibly inner retinal cells, in mice in total darkness in vivo, regardless of compensatory changes in LTCC subtype manifested in the mutant mice.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States 2Department of Ophthalmology, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Geoffrey G Murphy
- University of Michigan Medical School, Molecular Behavioral Neuroscience Institute, Molecular and Integrative Physiology, Ann Arbor, Michigan, United States
| | - Cheryl Mae Craft
- Mary D. Allen Laboratory for Vision Research, USC Eye Institute, and Department of Ophthalmology and Department of Cell and Neurobiology, Keck School of Medicine of the University of Southern California, Los Angeles, California, United States
| | - D James Surmeier
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Robin Roberts
- Department of Anatomy and Cell Biology Wayne State University School of Medicine, Detroit, Michigan, United States
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78
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Veleri S, Lazar CH, Chang B, Sieving PA, Banin E, Swaroop A. Biology and therapy of inherited retinal degenerative disease: insights from mouse models. Dis Model Mech 2015; 8:109-29. [PMID: 25650393 PMCID: PMC4314777 DOI: 10.1242/dmm.017913] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Retinal neurodegeneration associated with the dysfunction or death of photoreceptors is a major cause of incurable vision loss. Tremendous progress has been made over the last two decades in discovering genes and genetic defects that lead to retinal diseases. The primary focus has now shifted to uncovering disease mechanisms and designing treatment strategies, especially inspired by the successful application of gene therapy in some forms of congenital blindness in humans. Both spontaneous and laboratory-generated mouse mutants have been valuable for providing fundamental insights into normal retinal development and for deciphering disease pathology. Here, we provide a review of mouse models of human retinal degeneration, with a primary focus on diseases affecting photoreceptor function. We also describe models associated with retinal pigment epithelium dysfunction or synaptic abnormalities. Furthermore, we highlight the crucial role of mouse models in elucidating retinal and photoreceptor biology in health and disease, and in the assessment of novel therapeutic modalities, including gene- and stem-cell-based therapies, for retinal degenerative diseases.
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Affiliation(s)
- Shobi Veleri
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Csilla H Lazar
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA. Molecular Biology Center, Interdisciplinary Research Institute on Bio-Nano Sciences, Babes-Bolyai-University, Cluj-Napoca, 400271, Romania
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Paul A Sieving
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Eyal Banin
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA. Center for Retinal and Macular Degenerations, Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Anand Swaroop
- Neurobiology-Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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Cao Y, Sarria I, Fehlhaber KE, Kamasawa N, Orlandi C, James KN, Hazen JL, Gardner MR, Farzan M, Lee A, Baker S, Baldwin K, Sampath AP, Martemyanov KA. Mechanism for Selective Synaptic Wiring of Rod Photoreceptors into the Retinal Circuitry and Its Role in Vision. Neuron 2015; 87:1248-1260. [PMID: 26402607 PMCID: PMC4583715 DOI: 10.1016/j.neuron.2015.09.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/11/2015] [Accepted: 08/31/2015] [Indexed: 01/06/2023]
Abstract
In the retina, rod and cone photoreceptors form distinct connections with different classes of downstream bipolar cells. However, the molecular mechanisms responsible for their selective connectivity are unknown. Here we identify a cell-adhesion protein, ELFN1, to be essential for the formation of synapses between rods and rod ON-bipolar cells in the primary rod pathway. ELFN1 is expressed selectively in rods where it is targeted to the axonal terminals by the synaptic release machinery. At the synapse, ELFN1 binds in trans to mGluR6, the postsynaptic receptor on rod ON-bipolar cells. Elimination of ELFN1 in mice prevents the formation of synaptic contacts involving rods, but not cones, allowing a dissection of the contributions of primary and secondary rod pathways to retinal circuit function and vision. We conclude that ELFN1 is necessary for the selective wiring of rods into the primary rod pathway and is required for high sensitivity of vision.
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Affiliation(s)
- Yan Cao
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Ignacio Sarria
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Katherine E Fehlhaber
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Cesare Orlandi
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Kiely N James
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92121, USA
| | - Jennifer L Hazen
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92121, USA
| | - Matthew R Gardner
- Department of Infectious Disease, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Michael Farzan
- Department of Infectious Disease, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, 51 Newton Road, Iowa City, IA 52242, USA
| | - Sheila Baker
- Department of Biochemistry, University of Iowa, 51 Newton Road, Iowa City, IA 52242, USA
| | - Kristin Baldwin
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92121, USA
| | - Alapakkam P Sampath
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA.
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Heyes S, Pratt WS, Rees E, Dahimene S, Ferron L, Owen MJ, Dolphin AC. Genetic disruption of voltage-gated calcium channels in psychiatric and neurological disorders. Prog Neurobiol 2015; 134:36-54. [PMID: 26386135 PMCID: PMC4658333 DOI: 10.1016/j.pneurobio.2015.09.002] [Citation(s) in RCA: 164] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/08/2015] [Accepted: 09/08/2015] [Indexed: 12/15/2022]
Abstract
Voltage-gated calcium channel classification—genes and proteins. Genetic analysis of neuropsychiatric syndromes. Calcium channel genes identified from GWA studies of psychiatric disorders. Rare mutations in calcium channel genes in psychiatric disorders. Pathophysiological sequelae of CACNA1C mutations and polymorphisms. Monogenic disorders resulting from harmful mutations in other voltage-gated calcium channel genes. Changes in calcium channel gene expression in disease. Involvement of voltage-gated calcium channels in early brain development.
This review summarises genetic studies in which calcium channel genes have been connected to the spectrum of neuropsychiatric syndromes, from bipolar disorder and schizophrenia to autism spectrum disorders and intellectual impairment. Among many other genes, striking numbers of the calcium channel gene superfamily have been implicated in the aetiology of these diseases by various DNA analysis techniques. We will discuss how these relate to the known monogenic disorders associated with point mutations in calcium channels. We will then examine the functional evidence for a causative link between these mutations or single nucleotide polymorphisms and the disease processes. A major challenge for the future will be to translate the expanding psychiatric genetic findings into altered physiological function, involvement in the wider pathology of the diseases, and what potential that provides for personalised and stratified treatment options for patients.
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Affiliation(s)
- Samuel Heyes
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Elliott Rees
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Michael J Owen
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
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Berkowitz BA, Bissig D, Roberts R. MRI of rod cell compartment-specific function in disease and treatment in vivo. Prog Retin Eye Res 2015; 51:90-106. [PMID: 26344734 DOI: 10.1016/j.preteyeres.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/26/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
Abstract
Rod cell oxidative stress is a major pathogenic factor in retinal disease, such as diabetic retinopathy (DR) and retinitis pigmentosa (RP). Personalized, non-destructive, and targeted treatment for these diseases remains elusive since current imaging methods cannot analytically measure treatment efficacy against rod cell compartment-specific oxidative stress in vivo. Over the last decade, novel MRI-based approaches that address this technology gap have been developed. This review summarizes progress in the development of MRI since 2006 that enables earlier evaluation of the impact of disease on rod cell compartment-specific function and the efficacy of anti-oxidant treatment than is currently possible with other methods. Most of the new assays of rod cell compartment-specific function are based on endogenous contrast mechanisms, and this is expected to facilitate their translation into patients with DR and RP, and other oxidative stress-based retinal diseases.
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Affiliation(s)
- Bruce A Berkowitz
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA; Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA.
| | - David Bissig
- Dept. of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Robin Roberts
- Dept. Of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA
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82
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Maddox DM, Collin GB, Ikeda A, Pratt CH, Ikeda S, Johnson BA, Hurd RE, Shopland LS, Naggert JK, Chang B, Krebs MP, Nishina PM. A Mutation in Syne2 Causes Early Retinal Defects in Photoreceptors, Secondary Neurons, and Müller Glia. Invest Ophthalmol Vis Sci 2015; 56:3776-87. [PMID: 26066746 DOI: 10.1167/iovs.14-16047] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
PURPOSE The purpose of this study was to identify the molecular basis and characterize the pathological consequences of a spontaneous mutation named cone photoreceptor function loss 8 (cpfl8) in a mouse model with a significantly reduced cone electroretinography (ERG) response. METHODS The chromosomal position for the recessive cpfl8 mutation was determined by DNA pooling and by subsequent genotyping with simple sequence length polymorphic markers in an F2 intercross phenotyped by ERG. Genes within the candidate region of both mutants and controls were directly sequenced and compared. The effects of the mutation were examined in longitudinal studies by light microscopy, marker analysis, transmission electron microscopy, and ERG. RESULTS The cpfl8 mutation was mapped to Chromosome 12, and a premature stop codon was identified in the spectrin repeat containing nuclear envelope 2 (Syne2) gene. The reduced cone ERG response was due to a significant reduction in cone photoreceptors. Longitudinal studies of the early postnatal retina indicated that the cone photoreceptors fail to develop properly, rod photoreceptors mislocalize to the inner nuclear layer, and both rods and cones undergo apoptosis prematurely. Moreover, we observed migration defects of secondary neurons and ectopic Müller cell bodies in the outer nuclear layer in early postnatal development. CONCLUSIONS SYNE2 is important for normal retinal development. We have determined that not only is photoreceptor nuclear migration affected, but also the positions of Müller glia and secondary neurons are disturbed early in retinal development. The cpfl8 mouse model will serve as an important resource for further examining the role of nuclear scaffolding and migration in the developing retina.
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Affiliation(s)
| | | | - Akihiro Ikeda
- University of Wisconsin-Madison, Department of Medical Genetics, Madison, Wisconsin, United States
| | | | - Sakae Ikeda
- University of Wisconsin-Madison, Department of Medical Genetics, Madison, Wisconsin, United States
| | - Britt A Johnson
- University of Wisconsin-Madison, Department of Medical Genetics, Madison, Wisconsin, United States 3University of Miami, Miller School of Medicine, Miami, Florida, United States
| | - Ron E Hurd
- The Jackson Laboratory Bar Harbor, Maine, United States
| | | | | | - Bo Chang
- The Jackson Laboratory Bar Harbor, Maine, United States
| | - Mark P Krebs
- The Jackson Laboratory Bar Harbor, Maine, United States
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Johnson V, Xiang M, Chen Z, Junge HJ. Neurite Mistargeting and Inverse Order of Intraretinal Vascular Plexus Formation Precede Subretinal Vascularization in Vldlr Mutant Mice. PLoS One 2015; 10:e0132013. [PMID: 26177550 PMCID: PMC4503745 DOI: 10.1371/journal.pone.0132013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 06/09/2015] [Indexed: 02/07/2023] Open
Abstract
In the retina blood vessels are required to support a high metabolic rate, however, uncontrolled vascular growth can lead to impaired vision and blindness. Subretinal vascularization (SRV), one type of pathological vessel growth, occurs in retinal angiomatous proliferation and proliferative macular telangiectasia. In these diseases SRV originates from blood vessels within the retina. We use mice with a targeted disruption in the Vldl-receptor (Vldlr) gene as a model to study SRV with retinal origin. We find that Vldlr mRNA is strongly expressed in the neuroretina, and we observe both vascular and neuronal phenotypes in Vldlr-/- mice. Unexpectedly, horizontal cell (HC) neurites are mistargeted prior to SRV in this model, and the majority of vascular lesions are associated with mistargeted neurites. In Foxn4-/- mice, which lack HCs and display reduced amacrine cell (AC) numbers, we find severe defects in intraretinal capillary development. However, SRV is not suppressed in Foxn4-/-;Vldlr-/- mice, which reveals that mistargeted HC neurites are not required for vascular lesion formation. In the absence of VLDLR, the intraretinal capillary plexuses form in an inverse order compared to normal development, and subsequent to this early defect, vascular proliferation is increased. We conclude that SRV in the Vldlr-/- model is associated with mistargeted neurites and that SRV is preceded by altered retinal vascular development.
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Affiliation(s)
- Verity Johnson
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, 80309, United States of America
| | - Mengqing Xiang
- Center for Advanced Biotechnology and Medicine and Department of Pediatrics, Rutgers University-Robert Wood Johnson Medical School, Piscataway, New Jersey, 08901, United States of America
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 54 South Xianlie Road, Guangzhou, 510060, China
| | - Zhe Chen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, 80309, United States of America
| | - Harald J. Junge
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, 80309, United States of America
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Abstract
Ca2+-dependent inactivation (CDI) is a negative feedback regulation of voltage-gated Cav1 and Cav2 channels that is mediated by the Ca2+ sensing protein, calmodulin (CaM), binding to the pore-forming Cav α1 subunit. David Yue and his colleagues made seminal contributions to our understanding of this process, as well as factors that regulate CDI. Important in this regard are members of a family of Ca2+ binding proteins (CaBPs) that are related to calmodulin. CaBPs are expressed mainly in neural tissues and can antagonize CaM-dependent CDI for Cav1 L-type channels. This review will focus on the roles of CaBPs as Cav1-interacting proteins, and the significance of these interactions for vision, hearing, and neuronal Ca2+ signaling events.
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Affiliation(s)
- Jason Hardie
- a Departments of Molecular Physiology and Biophysics ; Otolaryngology-Head and Neck Surgery and Neurology; University of Iowa ; Iowa City , IA USA
| | - Amy Lee
- a Departments of Molecular Physiology and Biophysics ; Otolaryngology-Head and Neck Surgery and Neurology; University of Iowa ; Iowa City , IA USA
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Nohara LL, Stanwood SR, Omilusik KD, Jefferies WA. Tweeters, Woofers and Horns: The Complex Orchestration of Calcium Currents in T Lymphocytes. Front Immunol 2015; 6:234. [PMID: 26052328 PMCID: PMC4440397 DOI: 10.3389/fimmu.2015.00234] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 04/30/2015] [Indexed: 11/28/2022] Open
Abstract
Elevation of intracellular calcium ion (Ca2+) levels is a vital event that regulates T lymphocyte homeostasis, activation, proliferation, differentiation, and apoptosis. The mechanisms that regulate intracellular Ca2+ signaling in lymphocytes involve tightly controlled concinnity of multiple ion channels, membrane receptors, and signaling molecules. T cell receptor (TCR) engagement results in depletion of endoplasmic reticulum (ER) Ca2+ stores and subsequent sustained influx of extracellular Ca2+ through Ca2+ release-activated Ca2+ (CRAC) channels in the plasma membrane. This process termed store-operated Ca2+ entry (SOCE) involves the ER Ca2+ sensing molecule, STIM1, and a pore-forming plasma membrane protein, ORAI1. However, several other important Ca2+ channels that are instrumental in T cell function also exist. In this review, we discuss the role of additional Ca2+ channel families expressed on the plasma membrane of T cells that likely contribute to Ca2+ influx following TCR engagement, which include the TRP channels, the NMDA receptors, the P2X receptors, and the IP3 receptors, with a focus on the voltage-dependent Ca2+ (CaV) channels.
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Affiliation(s)
- Lilian L Nohara
- Michael Smith Laboratories, University of British Columbia , Vancouver, BC , Canada ; Department of Microbiology and Immunology, University of British Columbia , Vancouver, BC , Canada
| | - Shawna R Stanwood
- Michael Smith Laboratories, University of British Columbia , Vancouver, BC , Canada ; Department of Microbiology and Immunology, University of British Columbia , Vancouver, BC , Canada
| | - Kyla D Omilusik
- Michael Smith Laboratories, University of British Columbia , Vancouver, BC , Canada ; Department of Microbiology and Immunology, University of British Columbia , Vancouver, BC , Canada
| | - Wilfred A Jefferies
- Michael Smith Laboratories, University of British Columbia , Vancouver, BC , Canada ; Department of Microbiology and Immunology, University of British Columbia , Vancouver, BC , Canada ; Centre for Blood Research, University of British Columbia , Vancouver, BC , Canada ; The Djavad Mowafaghian Centre for Brain Health, University of British Columbia , Vancouver, BC , Canada ; Department of Medical Genetics, University of British Columbia , Vancouver, BC , Canada ; Department of Zoology, University of British Columbia , Vancouver, BC , Canada
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Identification of a novel heterozygous missense mutation in the CACNA1F gene in a chinese family with retinitis pigmentosa by next generation sequencing. BIOMED RESEARCH INTERNATIONAL 2015; 2015:907827. [PMID: 26075273 PMCID: PMC4449926 DOI: 10.1155/2015/907827] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 09/14/2014] [Indexed: 12/18/2022]
Abstract
Background. Retinitis pigmentosa (RP) is an inherited retinal degenerative disease, which is clinically and genetically heterogeneous, and the inheritance pattern is complex. In this study, we have intended to study the possible association of certain genes with X-linked RP (XLRP) in a Chinese family. Methods. A Chinese family with RP was recruited, and a total of seven individuals were enrolled in this genetic study. Genomic DNA was isolated from peripheral leukocytes, and used for the next generation sequencing (NGS). Results. The affected individual presented the clinical signs of XLRP. A heterozygous missense mutation (c.1555C>T, p.R519W) was identified by NGS in exon 13 of the CACNA1F gene on X chromosome, and was confirmed by Sanger sequencing. It showed perfect cosegregation with the disease in the family. The mutation at this position in the CACNA1F gene of RP was found novel by database searching. Conclusion. By using NGS, we have found a novel heterozygous missense mutation (c.1555C>T, p.R519W) in CACNA1F gene, which is probably associated with XLRP. The findings might provide new insights into the cause and diagnosis of RP, and have implications for genetic counseling and clinical management in this family.
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Nash BM, Wright DC, Grigg JR, Bennetts B, Jamieson RV. Retinal dystrophies, genomic applications in diagnosis and prospects for therapy. Transl Pediatr 2015; 4:139-63. [PMID: 26835369 PMCID: PMC4729094 DOI: 10.3978/j.issn.2224-4336.2015.04.03] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Retinal dystrophies (RDs) are degenerative diseases of the retina which have marked clinical and genetic heterogeneity. Common presentations among these disorders include night or colour blindness, tunnel vision and subsequent progression to complete blindness. The known causative disease genes have a variety of developmental and functional roles with mutations in more than 120 genes shown to be responsible for the phenotypes. In addition, mutations within the same gene have been shown to cause different disease phenotypes, even amongst affected individuals within the same family highlighting further levels of complexity. The known disease genes encode proteins involved in retinal cellular structures, phototransduction, the visual cycle, and photoreceptor structure or gene regulation. This review aims to demonstrate the high degree of genetic complexity in both the causative disease genes and their associated phenotypes, highlighting the more common clinical manifestation of retinitis pigmentosa (RP). The review also provides insight to recent advances in genomic molecular diagnosis and gene and cell-based therapies for the RDs.
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Affiliation(s)
- Benjamin M Nash
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - Dale C Wright
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - John R Grigg
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - Bruce Bennetts
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
| | - Robyn V Jamieson
- 1 Eye Genetics Research Group, Children's Medical Research Institute, University of Sydney, The Children's Hospital at Westmead and Save Sight Institute, Sydney, NSW, Australia ; 2 Sydney Genome Diagnostics, The Children's Hospital at Westmead, Sydney, NSW, Australia ; 3 Discipline of Paediatrics and Child Health, Sydney Medical School, University of Sydney, NSW, Australia
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88
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Congenital stationary night blindness: An analysis and update of genotype–phenotype correlations and pathogenic mechanisms. Prog Retin Eye Res 2015; 45:58-110. [DOI: 10.1016/j.preteyeres.2014.09.001] [Citation(s) in RCA: 207] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/25/2014] [Accepted: 09/30/2014] [Indexed: 01/18/2023]
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89
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Abstract
Voltage- and ligand-gated ion channels form the molecular basis of cellular excitability. With >400 members and accounting for ∼1.5% of the human genome, ion channels are some of the most well studied of all proteins in heterologous expression systems. Yet, ion channels often exhibit unexpected properties in vivo because of their interaction with a variety of signaling/scaffolding proteins. Such interactions can influence the function and localization of ion channels, as well as their coupling to intracellular second messengers and pathways, thus increasing the signaling potential of these ion channels in neurons. Moreover, functions have been ascribed to ion channels that are largely independent of their ion-conducting roles. Molecular and functional dissection of the ion channel proteome/interactome has yielded new insights into the composition of ion channel complexes and how their dysregulation leads to human disease.
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90
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Abstract
Across the nervous system, neurons form highly stereotypic patterns of synaptic connections that are designed to serve specific functions. Mature wiring patterns are often attained upon the refinement of early, less precise connectivity. Much work has led to the prevailing view that many developing circuits are sculpted by activity-dependent competition among converging afferents, which results in the elimination of unwanted synapses and the maintenance and strengthening of desired connections. Studies of the vertebrate retina, however, have recently revealed that activity can play a role in shaping developing circuits without engaging competition among converging inputs that differ in their activity levels. Such neurotransmission-mediated processes can produce stereotypic wiring patterns by promoting selective synapse formation rather than elimination. We discuss how the influence of transmission may also be limited by circuit design and further highlight the importance of transmission beyond development in maintaining wiring specificity and synaptic organization of neural circuits.
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91
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Knoflach D, Schicker K, Glösmann M, Koschak A. Gain-of-function nature of Cav1.4 L-type calcium channels alters firing properties of mouse retinal ganglion cells. Channels (Austin) 2015; 9:298-306. [PMID: 26274509 PMCID: PMC4826138 DOI: 10.1080/19336950.2015.1078040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/22/2015] [Accepted: 07/22/2015] [Indexed: 10/25/2022] Open
Abstract
Proper function of Cav1.4 L-type calcium channels is crucial for neurotransmitter release in the retina. Our understanding about how different levels of Cav1.4 channel activity affect retinal function is still limited. In the gain-of-function mouse model Cav1.4-IT we expected a reduction in the photoreceptor dynamic range but still transmission toward retinal ganglion cells. A fraction of Cav1.4-IT ganglion cells responded to light stimulation in multielectrode array recordings from whole-mounted retinas, but showed a significantly delayed response onset. Another significant number of cells showed higher activity in darkness. In addition to structural remodeling observed at the first retinal synapse of Cav1.4-IT mice the functional data suggested a loss of contrast enhancement, a fundamental feature of our visual system. In fact, Cav1.4-IT mouse retinas showed a decline in spatial response and changes in their contrast sensitivity profile. Photoreceptor degeneration was obvious from the nodular structure of cone axons and enlarged pedicles which partly moved toward the outer nuclear layer. Loss of photoreceptors was also expressed as reduced expression of proteins involved in chemical and electrical transmission, as such metabotropic glutamate receptor mGluR6 and the gap junction protein Connexin 36. Such gross changes in retinal structure and function could also explain the diminished visual performance of CSNB2 patients. The expression pattern of the plasma-membrane calcium ATPase 1 which participates in the maintenance of the intracellular calcium homeostasis in photoreceptors was changed in Cav1.4-IT mice. This might be part of a protection mechanism against increased calcium influx, as this is suggested for Cav1.4-IT channels.
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Affiliation(s)
- Dagmar Knoflach
- Medical University Vienna, Center for Physiology and Pharmacology; Department of Neurophysiology and -pharmacology; Vienna, Austria
| | - Klaus Schicker
- Medical University Vienna, Center for Physiology and Pharmacology; Department of Neurophysiology and -pharmacology; Vienna, Austria
| | | | - Alexandra Koschak
- Medical University Vienna, Center for Physiology and Pharmacology; Department of Neurophysiology and -pharmacology; Vienna, Austria
- University of Innsbruck, Institute of Pharmacy, Pharmacology and Toxicology; Innsbruck, Austria
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92
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Lee A, Wang S, Williams B, Hagen J, Scheetz TE, Haeseleer F. Characterization of Cav1.4 complexes (α11.4, β2, and α2δ4) in HEK293T cells and in the retina. J Biol Chem 2014; 290:1505-21. [PMID: 25468907 DOI: 10.1074/jbc.m114.607465] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In photoreceptor synaptic terminals, voltage-gated Cav1.4 channels mediate Ca(2+) signals required for transmission of visual stimuli. Like other high voltage-activated Cav channels, Cav1.4 channels are composed of a main pore-forming Cav1.4 α1 subunit and auxiliary β and α2δ subunits. Of the four distinct classes of β and α2δ, β2 and α2δ4 are thought to co-assemble with Cav1.4 α1 subunits in photoreceptors. However, an understanding of the functional properties of this combination of Cav subunits is lacking. Here, we provide evidence that Cav1.4 α1, β2, and α2δ4 contribute to Cav1.4 channel complexes in the retina and describe their properties in electrophysiological recordings. In addition, we identified a variant of β2, named here β2X13, which, along with β2a, is present in photoreceptor terminals. Cav1.4 α1, β2, and α2δ4 were coimmunoprecipitated from lysates of transfected HEK293 cells and mouse retina and were found to interact in the outer plexiform layer of the retina containing the photoreceptor synaptic terminals, by proximity ligation assays. In whole-cell patch clamp recordings of transfected HEK293T cells, channels (Cav1.4 α1 + β2X13) containing α2δ4 exhibited weaker voltage-dependent activation than those with α2δ1. Moreover, compared with channels (Cav1.4 α1 + α2δ4) with β2a, β2X13-containing channels exhibited greater voltage-dependent inactivation. The latter effect was specific to Cav1.4 because it was not seen for Cav1.2 channels. Our results provide the first detailed functional analysis of the Cav1.4 subunits that form native photoreceptor Cav1.4 channels and indicate potential heterogeneity in these channels conferred by β2a and β2X13 variants.
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Affiliation(s)
- Amy Lee
- From the Departments of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, and Neurology, University of Iowa, Iowa City, Iowa 52242
| | - Shiyi Wang
- From the Departments of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, and Neurology, University of Iowa, Iowa City, Iowa 52242
| | - Brittany Williams
- From the Departments of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, and Neurology, University of Iowa, Iowa City, Iowa 52242
| | - Jussara Hagen
- From the Departments of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, and Neurology, University of Iowa, Iowa City, Iowa 52242
| | - Todd E Scheetz
- the Departments of Ophthalmology and Visual Sciences and Biomedical Engineering, University of Iowa, Iowa City, Iowa 52242, and
| | - Françoise Haeseleer
- the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
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93
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Park S, Li C, Ames JB. ¹H, ¹⁵N, and ¹³C chemical shift assignments of murine calcium-binding protein 4. BIOMOLECULAR NMR ASSIGNMENTS 2014; 8:361-364. [PMID: 23925854 PMCID: PMC3877709 DOI: 10.1007/s12104-013-9517-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 08/01/2013] [Indexed: 06/02/2023]
Abstract
Calcium-binding protein 4 (CaBP4) regulates voltage-gated Ca(2+) channels in retinal rod cells and specific mutations within CaBP4 are associated with congenital stationary night blindness type 2. We report complete NMR chemical shift assignments of the Ca(2+)-saturated form of CaBP4 with Ca(2+) bound at EF1, EF3 and EF4 (BMRB no. 18877).
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94
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Park S, Li C, Haeseleer F, Palczewski K, Ames JB. Structural insights into activation of the retinal L-type Ca²⁺ channel (Cav1.4) by Ca²⁺-binding protein 4 (CaBP4). J Biol Chem 2014; 289:31262-73. [PMID: 25258313 DOI: 10.1074/jbc.m114.604439] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
CaBP4 modulates Ca(2+)-dependent activity of L-type voltage-gated Ca(2+) channels (Cav1.4) in retinal photoreceptor cells. Mg(2+) binds to the first and third EF-hands (EF1 and EF3), and Ca(2+) binds to EF1, EF3, and EF4 of CaBP4. Here we present NMR structures of CaBP4 in both Mg(2+)-bound and Ca(2+)-bound states and model the CaBP4 structural interaction with Cav1.4. CaBP4 contains an unstructured N-terminal region (residues 1-99) and four EF-hands in two separate lobes. The N-lobe consists of EF1 and EF2 in a closed conformation with either Mg(2+) or Ca(2+) bound at EF1. The C-lobe binds Ca(2+) at EF3 and EF4 and exhibits a Ca(2+)-induced closed-to-open transition like that of calmodulin. Exposed residues in Ca(2+)-bound CaBP4 (Phe(137), Glu(168), Leu(207), Phe(214), Met(251), Phe(264), and Leu(268)) make contacts with the IQ motif in Cav1.4, and the Cav1.4 mutant Y1595E strongly impairs binding to CaBP4. We conclude that CaBP4 forms a collapsed structure around the IQ motif in Cav1.4 that we suggest may promote channel activation by disrupting an interaction between IQ and the inhibitor of Ca(2+)-dependent inactivation domain.
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Affiliation(s)
- Saebomi Park
- From the Department of Chemistry, University of California, Davis, California 95616
| | - Congmin Li
- From the Department of Chemistry, University of California, Davis, California 95616
| | - Françoise Haeseleer
- the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, and
| | - Krzysztof Palczewski
- the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965
| | - James B Ames
- From the Department of Chemistry, University of California, Davis, California 95616,
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95
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Ribic A, Liu X, Crair MC, Biederer T. Structural organization and function of mouse photoreceptor ribbon synapses involve the immunoglobulin protein synaptic cell adhesion molecule 1. J Comp Neurol 2014; 522:900-20. [PMID: 23982969 DOI: 10.1002/cne.23452] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 05/23/2013] [Accepted: 08/14/2013] [Indexed: 11/11/2022]
Abstract
Adhesive interactions in the retina instruct the developmental specification of inner retinal layers. However, potential roles of adhesion in the development and function of photoreceptor synapses remain incompletely understood. This contrasts with our understanding of synapse development in the CNS, which can be guided by select adhesion molecules such as the Synaptic Cell Adhesion Molecule 1 (SynCAM 1/CADM1/nectin-like 2 protein). This immunoglobulin superfamily protein modulates the development and plasticity of classical excitatory synapses. We show here by immunoelectron microscopy and immunoblotting that SynCAM 1 is expressed on mouse rod photoreceptors and their terminals in the outer nuclear and plexiform layers in a developmentally regulated manner. Expression of SynCAM 1 on rods is low in early postnatal stages (P3-P7) but increases after eye opening (P14). In support of functional roles in the photoreceptors, electroretinogram recordings demonstrate impaired responses to light stimulation in SynCAM 1 knockout (KO) mice. In addition, the structural integrity of synapses in the OPL requires SynCAM 1. Quantitative ultrastructural analysis of SynCAM 1 KO retina measured fewer fully assembled, triadic rod ribbon synapses. Furthermore, rod synapse ribbons are shortened in KO mice, and protein levels of Ribeye, a major structural component of ribbons, are reduced in SynCAM 1 KO retina. Together, our results implicate SynCAM 1 in the synaptic organization of the rod visual pathway and provide evidence for novel roles of synaptic adhesion in the structural and functional integrity of ribbon synapses.
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Affiliation(s)
- Adema Ribic
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520-8024
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96
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Samuel MA, Voinescu PE, Lilley BN, de Cabo R, Foretz M, Viollet B, Pawlyk B, Sandberg MA, Vavvas DG, Sanes JR. LKB1 and AMPK regulate synaptic remodeling in old age. Nat Neurosci 2014; 17:1190-7. [PMID: 25086610 PMCID: PMC5369022 DOI: 10.1038/nn.3772] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Accepted: 07/01/2014] [Indexed: 02/07/2023]
Abstract
Age-related decreases in neural function result in part from alterations in synapses. To identify molecular defects that lead to such changes, we focused on the outer retina, in which synapses are markedly altered in old rodents and humans. We found that the serine/threonine kinase LKB1 and one of its substrates, AMPK, regulate this process. In old mice, synaptic remodeling was accompanied by specific decreases in the levels of total LKB1 and active (phosphorylated) AMPK. In the absence of either kinase, young adult mice developed retinal defects similar to those that occurred in old wild-type animals. LKB1 and AMPK function in rod photoreceptors where their loss leads to aberrant axonal retraction, the extension of postsynaptic dendrites and the formation of ectopic synapses. Conversely, increasing AMPK activity genetically or pharmacologically attenuates and may reverse age-related synaptic alterations. Together, these results identify molecular determinants of age-related synaptic remodeling and suggest strategies for attenuating these changes.
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Affiliation(s)
- Melanie A Samuel
- 1] Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA. [2]
| | - P Emanuela Voinescu
- 1] Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA. [2]
| | - Brendan N Lilley
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
| | - Rafa de Cabo
- Laboratory of Experimental Gerontology, Translational Gerontology Branch, Intramural Research Program, National Institute on Aging, Baltimore, Maryland, USA
| | - Marc Foretz
- 1] Inserm, U1016, Institut Cochin, Paris, France. [2] CNRS, UMR8104, Paris, France. [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Benoit Viollet
- 1] Inserm, U1016, Institut Cochin, Paris, France. [2] CNRS, UMR8104, Paris, France. [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Basil Pawlyk
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Michael A Sandberg
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Demetrios G Vavvas
- Retina Service, Angiogenesis Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA
| | - Joshua R Sanes
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA
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97
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Hoon M, Okawa H, Della Santina L, Wong ROL. Functional architecture of the retina: development and disease. Prog Retin Eye Res 2014; 42:44-84. [PMID: 24984227 DOI: 10.1016/j.preteyeres.2014.06.003] [Citation(s) in RCA: 342] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/08/2014] [Accepted: 06/22/2014] [Indexed: 12/22/2022]
Abstract
Structure and function are highly correlated in the vertebrate retina, a sensory tissue that is organized into cell layers with microcircuits working in parallel and together to encode visual information. All vertebrate retinas share a fundamental plan, comprising five major neuronal cell classes with cell body distributions and connectivity arranged in stereotypic patterns. Conserved features in retinal design have enabled detailed analysis and comparisons of structure, connectivity and function across species. Each species, however, can adopt structural and/or functional retinal specializations, implementing variations to the basic design in order to satisfy unique requirements in visual function. Recent advances in molecular tools, imaging and electrophysiological approaches have greatly facilitated identification of the cellular and molecular mechanisms that establish the fundamental organization of the retina and the specializations of its microcircuits during development. Here, we review advances in our understanding of how these mechanisms act to shape structure and function at the single cell level, to coordinate the assembly of cell populations, and to define their specific circuitry. We also highlight how structure is rearranged and function is disrupted in disease, and discuss current approaches to re-establish the intricate functional architecture of the retina.
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Affiliation(s)
- Mrinalini Hoon
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Haruhisa Okawa
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Luca Della Santina
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Rachel O L Wong
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA.
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98
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Roosing S, Thiadens AAHJ, Hoyng CB, Klaver CCW, den Hollander AI, Cremers FPM. Causes and consequences of inherited cone disorders. Prog Retin Eye Res 2014; 42:1-26. [PMID: 24857951 DOI: 10.1016/j.preteyeres.2014.05.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 04/29/2014] [Accepted: 05/06/2014] [Indexed: 11/18/2022]
Abstract
Hereditary cone disorders (CDs) are characterized by defects of the cone photoreceptors or retinal pigment epithelium underlying the macula, and include achromatopsia (ACHM), cone dystrophy (COD), cone-rod dystrophy (CRD), color vision impairment, Stargardt disease (STGD) and other maculopathies. Forty-two genes have been implicated in non-syndromic inherited CDs. Mutations in the 5 genes implicated in ACHM explain ∼93% of the cases. On the contrary, only 21% of CRDs (17 genes) and 25% of CODs (8 genes) have been elucidated. The fact that the large majority of COD and CRD-associated genes are yet to be discovered hints towards the existence of unknown cone-specific or cone-sensitive processes. The ACHM-associated genes encode proteins that fulfill crucial roles in the cone phototransduction cascade, which is the most frequently compromised (10 genes) process in CDs. Another 7 CD-associated proteins are required for transport processes towards or through the connecting cilium. The remaining CD-associated proteins are involved in cell membrane morphogenesis and maintenance, synaptic transduction, and the retinoid cycle. Further novel genes are likely to be identified in the near future by combining large-scale DNA sequencing and transcriptomics technologies. For 31 of 42 CD-associated genes, mammalian models are available, 14 of which have successfully been used for gene augmentation studies. However, gene augmentation for CDs should ideally be developed in large mammalian models with cone-rich areas, which are currently available for only 11 CD genes. Future research will aim to elucidate the remaining causative genes, identify the molecular mechanisms of CD, and develop novel therapies aimed at preventing vision loss in individuals with CD in the future.
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Affiliation(s)
- Susanne Roosing
- Department of Human Genetics, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | | | - Carel B Hoyng
- Department of Ophthalmology, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Caroline C W Klaver
- Department of Ophthalmology Erasmus Medical Centre, 3000 CA, Rotterdam, The Netherlands; Department of Epidemiology, Erasmus Medical Centre, 3000 CA, Rotterdam, The Netherlands
| | - Anneke I den Hollander
- Department of Human Genetics, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands; Department of Ophthalmology, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
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99
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Kim KY, Scholl ES, Liu X, Shepherd A, Haeseleer F, Lee A. Localization and expression of CaBP1/caldendrin in the mouse brain. Neuroscience 2014; 268:33-47. [PMID: 24631676 DOI: 10.1016/j.neuroscience.2014.02.052] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 02/26/2014] [Accepted: 02/27/2014] [Indexed: 12/31/2022]
Abstract
Ca(2+) binding protein 1 (CaBP1) and caldendrin are alternatively spliced variants of a subfamily of CaBPs with high homology to calmodulin. Although CaBP1 and caldendrin regulate effectors including plasma membrane and intracellular Ca(2+) channels in heterologous expression systems, little is known about their functions in vivo. Therefore, we generated mice deficient in CaBP1/caldendrin expression (C-KO) and analyzed the expression and cellular localization of CaBP1 and caldendrin in the mouse brain. Immunoperoxidase labeling with antibodies recognizing both CaBP1 and caldendrin was absent in the brain of C-KO mice, but was intense in multiple brain regions of wild-type mice. By Western blot, the antibodies detected two proteins that were absent in the C-KO mouse and consistent in size with caldendrin variants originating from alternative translation initiation sites. By quantitative PCR, caldendrin transcript levels were far greater than those for CaBP1, particularly in the cerebral cortex and hippocampus. In the frontal cortex but not in the hippocampus, caldendrin expression increased steadily from birth. By double-label immunofluorescence, CaBP1/caldendrin was localized in principal neurons and parvalbumin-positive interneurons. In the cerebellum, CaBP1/caldendrin antibodies labeled interneurons in the molecular layer and in basket cell terminals surrounding the soma and axon initial segment of Purkinje neurons, but immunolabeling was absent in Purkinje neurons. We conclude that CaBP1/caldendrin is localized both pre- and postsynaptically where it may regulate Ca(2+) signaling and excitability in select groups of excitatory and inhibitory neurons.
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Affiliation(s)
- K Y Kim
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - E S Scholl
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - X Liu
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - A Shepherd
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - F Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
| | - A Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA.
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100
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Nguyen-Ba-Charvet KT, Chédotal A. Development of retinal layers. C R Biol 2014; 337:153-9. [PMID: 24702841 DOI: 10.1016/j.crvi.2013.11.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 11/28/2013] [Indexed: 11/26/2022]
Abstract
A noticeable characteristic of nervous systems is the arrangement of synapses into distinct layers. Such laminae are fundamental for the spatial organisation of synaptic connections transmitting different kinds of information. A major example of this is the inner plexiform layer (IPL) of the vertebrate retina, which is subdivided into at least ten sublayers. Another noticeable characteristic of these retina layers is that neurons are displayed in the horizontal plane in a non-random array termed as mosaic patterning. Recent studies of vertebrate and invertebrate systems have identified molecules that mediate these interactions. Here, we review the last mechanisms and molecules mediating retinal layering.
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Affiliation(s)
- Kim Tuyen Nguyen-Ba-Charvet
- Institut national de la santé et de la recherche médicale, UMR S968, CNRS UMR 7210, Université Pierre et Marie Curie (Paris-6), Institut de la vision, 17, rue Moreau, 75012 Paris, France
| | - Alain Chédotal
- Institut national de la santé et de la recherche médicale, UMR S968, CNRS UMR 7210, Université Pierre et Marie Curie (Paris-6), Institut de la vision, 17, rue Moreau, 75012 Paris, France.
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