scholarly journals Conditional Knock-Out of Vesicular GABA Transporter Gene from Starburst Amacrine Cells Reveals the Contributions of Multiple Synaptic Mechanisms Underlying Direction Selectivity in the Retina

2015 ◽  
Vol 35 (38) ◽  
pp. 13219-13232 ◽  
Author(s):  
Z. Pei ◽  
Q. Chen ◽  
D. Koren ◽  
B. Giammarinaro ◽  
H. Acaron Ledesma ◽  
...  
Keyword(s):  
Amacrine Cells ◽  
Direction Selectivity ◽  
Transporter Gene ◽  
Gaba Transporter ◽  
Knock Out ◽  
Starburst Amacrine Cells ◽  
Synaptic Mechanisms

scholarly journals GABA release selectively regulates synapse development at distinct inputs on direction-selective retinal ganglion cells

2018 ◽  
Vol 115 (51) ◽  
pp. E12083-E12090 ◽  
Author(s):  
Adam Bleckert ◽  
Chi Zhang ◽  
Maxwell H. Turner ◽  
David Koren ◽  
David M. Berson ◽  
...  
Keyword(s):  
Ganglion Cells ◽  
Selective Reduction ◽  
Amacrine Cells ◽  
Gaba Release ◽  
Direction Selectivity ◽  
Inhibitory Synapses ◽  
Retinal Ganglion ◽  
Gabaergic Transmission ◽  
Starburst Amacrine Cells ◽  
Receptor Clusters

Synaptic inhibition controls a neuron’s output via functionally distinct inputs at two subcellular compartments, the cell body and the dendrites. It is unclear whether the assembly of these distinct inhibitory inputs can be regulated independently by neurotransmission. In the mammalian retina, γ-aminobutyric acid (GABA) release from starburst amacrine cells (SACs) onto the dendrites of on–off direction-selective ganglion cells (ooDSGCs) is essential for directionally selective responses. We found that ooDSGCs also receive GABAergic input on their somata from other amacrine cells (ACs), including ACs containing the vasoactive intestinal peptide (VIP). When net GABAergic transmission is reduced, somatic, but not dendritic, GABAA receptor clusters on the ooDSGC increased in number and size. Correlative fluorescence imaging and serial electron microscopy revealed that these enlarged somatic receptor clusters are localized to synapses. By contrast, selectively blocking vesicular GABA release from either SACs or VIP ACs did not alter dendritic or somatic receptor distributions on the ooDSGCs, showing that neither SAC nor VIP AC GABA release alone is required for the development of inhibitory synapses in ooDSGCs. Furthermore, a reduction in net GABAergic transmission, but not a selective reduction from SACs, increased excitatory drive onto ooDSGCs. This increased excitation may drive a homeostatic increase in ooDSGC somatic GABAA receptors. Differential regulation of GABAA receptors on the ooDSGC’s soma and dendrites could facilitate homeostatic control of the ooDSGC’s output while enabling the assembly of the GABAergic connectivity underlying direction selectivity to be indifferent to altered transmission.

scholarly journals Formation of retinal direction-selective circuitry initiated by starburst amacrine cell homotypic contact

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Thomas A Ray ◽  
Suva Roy ◽  
Christopher Kozlowski ◽  
Jingjing Wang ◽  
Jon Cafaro ◽  
...  
Keyword(s):  
Synapse Formation ◽  
Ganglion Cells ◽  
Plexiform Layer ◽  
Surface Protein ◽  
Amacrine Cells ◽  
Direction Selectivity ◽  
Mouse Retina ◽  
Inner Plexiform Layer ◽  
Starburst Amacrine Cells ◽  
Developing Neurons

A common strategy by which developing neurons locate their synaptic partners is through projections to circuit-specific neuropil sublayers. Once established, sublayers serve as a substrate for selective synapse formation, but how sublayers arise during neurodevelopment remains unknown. Here, we identify the earliest events that initiate formation of the direction-selective circuit in the inner plexiform layer of mouse retina. We demonstrate that radially migrating newborn starburst amacrine cells establish homotypic contacts on arrival at the inner retina. These contacts, mediated by the cell-surface protein MEGF10, trigger neuropil innervation resulting in generation of two sublayers comprising starburst-cell dendrites. This dendritic scaffold then recruits projections from circuit partners. Abolishing MEGF10-mediated contacts profoundly delays and ultimately disrupts sublayer formation, leading to broader direction tuning and weaker direction-selectivity in retinal ganglion cells. Our findings reveal a mechanism by which differentiating neurons transition from migratory to mature morphology, and highlight this mechanism’s importance in forming circuit-specific sublayers.

scholarly journals Antagonistic center-surround mechanisms for direction selectivity in the retina

2019 ◽  
Author(s):  
Lea Ankri ◽  
Elishai Ezra-Tsur ◽  
Shir R. Maimon ◽  
Nathali Kaushansky ◽  
Michal Rivlin-Etzion
Keyword(s):  
Receptive Field ◽  
Sensory Processing ◽  
Ganglion Cells ◽  
Amacrine Cells ◽  
Direction Selectivity ◽  
Repetitive Stimulation ◽  
Spatiotemporal Model ◽  
Starburst Amacrine Cells ◽  
Modeling Data

SummaryA key feature in sensory processing is center-surround receptive field antagonism. Retinal direction-selectivity (DS) relies on asymmetric inhibition from starburst amacrine cells (SAC) to direction selective ganglion cells (DSGC). SAC exhibit antagonistic center-surround, depolarizing to light increments and decrements in their center and surround, respectively, but the role of this property in DS remains elusive. We found that a repetitive stimulation exhausts SAC center and enhances its surround and used it to distinguish center-from surround-mediated responses. Center, but not surround stimulation, induced direction-selective responses in SAC, as predicted by an elementary spatiotemporal model. Nevertheless, both SAC center and surround elicited direction-selective responses in DSGCs, but to opposite directions. Physiological and morphology-based modeling data show that the opposed responses resulted from inverted DSGC’s excitatory-inhibitory temporal balance, indicating that SAC response time rules DS. Our findings reveal antagonistic center-surround mechanisms for DS, and demonstrate how context-dependent center-surround reorganization enables flexible computations.

scholarly journals Receptoral Mechanisms for Fast Cholinergic Transmission in Direction-Selective Retinal Circuitry

2020 ◽  
Vol 14 ◽  
Author(s):  
Joseph Pottackal ◽  
Joshua H. Singer ◽  
Jonathan B. Demb
Keyword(s):  
Synaptic Transmission ◽  
Amacrine Cells ◽  
Direction Selectivity ◽  
Gabaergic Inhibition ◽  
Temporal Difference ◽  
Cholinergic Transmission ◽  
Null Direction ◽  
Gabaergic Transmission ◽  
Temporal Properties ◽  
Synaptic Mechanisms

Direction selectivity represents an elementary sensory computation that can be related to underlying synaptic mechanisms. In mammalian retina, direction-selective ganglion cells (DSGCs) respond strongly to visual motion in a “preferred” direction and weakly to motion in the opposite, “null” direction. The DS mechanism depends on starburst amacrine cells (SACs), which provide null direction-tuned GABAergic inhibition and untuned cholinergic excitation to DSGCs. GABAergic inhibition depends on conventional synaptic transmission, whereas cholinergic excitation apparently depends on paracrine (i.e., non-synaptic) transmission. Despite its paracrine mode of transmission, cholinergic excitation is more transient than GABAergic inhibition, yielding a temporal difference that contributes essentially to the DS computation. To isolate synaptic mechanisms that generate the distinct temporal properties of cholinergic and GABAergic transmission from SACs to DSGCs, we optogenetically stimulated SACs while recording postsynaptic currents (PSCs) from DSGCs in mouse retina. Direct recordings from channelrhodopsin-2-expressing (ChR2+) SACs during quasi-white noise (WN) (0-30 Hz) photostimulation demonstrated precise, graded optogenetic control of SAC membrane current and potential. Linear systems analysis of ChR2-evoked PSCs recorded in DSGCs revealed cholinergic transmission to be faster than GABAergic transmission. A deconvolution-based analysis showed that distinct postsynaptic receptor kinetics fully account for the temporal difference between cholinergic and GABAergic transmission. Furthermore, GABAA receptor blockade prolonged cholinergic transmission, identifying a new functional role for GABAergic inhibition of SACs. Thus, fast cholinergic transmission from SACs to DSGCs arises from at least two distinct mechanisms, yielding temporal properties consistent with conventional synapses despite its paracrine nature.

scholarly journals Characterization of the Frmd7 Knock-Out Mice Generated by the EUCOMM/COMP Repository as a Model for Idiopathic Infantile Nystagmus (IIN)

Genes ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1157
Author(s):  
Ahmed Salman ◽  
Samuel B. Hutton ◽  
Tutte Newall ◽  
Jennifer A. Scott ◽  
Helen L. Griffiths ◽  
...  
Keyword(s):  
Eye Tracking ◽  
High Speed ◽  
Mrna Level ◽  
Amacrine Cells ◽  
Knock Out ◽  
Optokinetic Reflex ◽  
Antibody Staining ◽  
Infantile Nystagmus ◽  
Robust Model ◽  
Starburst Amacrine Cells

In this study, we seek to exclude other pathophysiological mechanisms by which Frmd7 knock-down may cause Idiopathic Infantile Nystagmus (IIN) using the Frmd7.tm1a and Frmd7.tm1b murine models. We used a combination of genetic, histological and visual function techniques to characterize the role of Frmd7 gene in IIN using a novel murine model for the disease. We demonstrate that the Frmd7.tm1b allele represents a more robust model of Frmd7 knock-out at the mRNA level. The expression of Frmd7 was investigated using both antibody staining and X-gal staining confirming previous reports that Frmd7 expression in the retina is restricted to starburst amacrine cells and demonstrating that X-gal staining recapitulates the expression pattern in this model. Thus, it offers a useful tool for further expression studies. We also show that gross retinal morphology and electrophysiology are unchanged in these Frmd7 mutant models when compared with wild-type mice. High-speed eye-tracking recordings of Frmd7 mutant mice confirm a specific horizontal optokinetic reflex defect. In summary, our study confirms the likely role for Frmd7 in the optokinetic reflex in mice mediated by starburst amacrine cells. We show that the Frmd7.tm1b model provides a more robust knock-out than the Frmd7.tm1a model at the mRNA level, although the functional consequence is unchanged. Finally, we establish a robust eye-tracking technique in mice that can be used in a variety of future studies using this model and others. Although our data highlight a deficit in the optiokinetic reflex as a result of the starburst amacrine cells in the retina, this does not rule out the involvement of other cells, in the brain or the retina where Frmd7 is expressed, in the pathophysiology of IIN.

scholarly journals Receptive field properties of bipolar cell axon terminals in direction-selective sublaminas of the mouse retina

2014 ◽  
Vol 112 (8) ◽  
pp. 1950-1962 ◽  
Author(s):  
Minggang Chen ◽  
Seunghoon Lee ◽  
Silvia J. H. Park ◽  
Loren L. Looger ◽  
Z. Jimmy Zhou
Keyword(s):  
Receptive Field ◽  
Ganglion Cells ◽  
Amacrine Cells ◽  
Direction Selectivity ◽  
Bipolar Cells ◽  
Visual Signals ◽  
Mouse Retina ◽  
Patch Clamp Recording ◽  
Axon Terminals ◽  
Starburst Amacrine Cells

Retinal bipolar cells (BCs) transmit visual signals in parallel channels from the outer to the inner retina, where they provide glutamatergic inputs to specific networks of amacrine and ganglion cells. Intricate network computation at BC axon terminals has been proposed as a mechanism for complex network computation, such as direction selectivity, but direct knowledge of the receptive field property and the synaptic connectivity of the axon terminals of various BC types is required in order to understand the role of axonal computation by BCs. The present study tested the essential assumptions of the presynaptic model of direction selectivity at axon terminals of three functionally distinct BC types that ramify in the direction-selective strata of the mouse retina. Results from two-photon Ca2+ imaging, optogenetic stimulation, and dual patch-clamp recording demonstrated that 1) CB5 cells do not receive fast GABAergic synaptic feedback from starburst amacrine cells (SACs); 2) light-evoked and spontaneous Ca2+ responses are well coordinated among various local regions of CB5 axon terminals; 3) CB5 axon terminals are not directionally selective; 4) CB5 cells consist of two novel functional subtypes with distinct receptive field structures; 5) CB7 cells provide direct excitatory synaptic inputs to, but receive no direct GABAergic synaptic feedback from, SACs; and 6) CB7 axon terminals are not directionally selective, either. These findings help to simplify models of direction selectivity by ruling out complex computation at BC terminals. They also show that CB5 comprises two functional subclasses of BCs.

Retinal direction selectivity after targeted laser ablation of starburst amacrine cells

Nature ◽  
10.1038/38723 ◽  
1997 ◽  
Vol 389 (6649) ◽  
pp. 378-382 ◽  
Author(s):  
Shigang He ◽  
Richard H. Masland
Keyword(s):  
Laser Ablation ◽  
Amacrine Cells ◽  
Direction Selectivity ◽  
Starburst Amacrine Cells

scholarly journals Retinal direction selectivity in the absence of asymmetric starburst amacrine cell responses

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Laura Hanson ◽  
Santhosh Sethuramanujam ◽  
Geoff deRosenroll ◽  
Varsha Jain ◽  
Gautam B Awatramani
Keyword(s):  
Ganglion Cells ◽  
Amacrine Cells ◽  
Direction Selectivity ◽  
Cell Responses ◽  
Receptor Knockout Mouse ◽  
Starburst Amacrine Cells ◽  
Gabaergic Synapses ◽  
Novel Strategy ◽  
Starburst Amacrine Cell ◽  
Differential Connectivity

In the mammalian retina, direction-selectivity is thought to originate in the dendrites of GABAergic/cholinergic starburst amacrine cells, where it is first observed. However, here we demonstrate that direction selectivity in downstream ganglion cells remains remarkably unaffected when starburst dendrites are rendered non-directional, using a novel strategy combining a conditional GABAA α2 receptor knockout mouse with optogenetics. We show that temporal asymmetries between excitation/inhibition, arising from the differential connectivity patterns of starburst cholinergic and GABAergic synapses to ganglion cells, form the basis for a parallel mechanism generating direction selectivity. We further demonstrate that these distinct mechanisms work in a coordinated way to refine direction selectivity as the stimulus crosses the ganglion cell’s receptive field. Thus, precise spatiotemporal patterns of inhibition and excitation that determine directional responses in ganglion cells are shaped by two ‘core’ mechanisms, both arising from distinct specializations of the starburst network.

scholarly journals A Dendrite-Autonomous Mechanism for Direction Selectivity in Retinal Starburst Amacrine Cells

PLoS Biology ◽  
2007 ◽  
Vol 5 (7) ◽  
pp. e185 ◽  
Author(s):  
Susanne E Hausselt ◽  
Thomas Euler ◽  
Peter B Detwiler ◽  
Winfried Denk
Keyword(s):  
Amacrine Cells ◽  
Direction Selectivity ◽  
Starburst Amacrine Cells
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