Increased density and age-related sharing of synapses at the cone to OFF bipolar cell synapse in the mouse retina.
Ontology highlight
ABSTRACT:
SUBMITTER: Simmons AB
PROVIDER: S-EPMC7346645 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:In vertebrates, retinal neural circuitry for visual perception is organized in specific layers. The outer plexiform layer is the first synaptic region in the visual pathway, where photoreceptor synaptic terminals connect with bipolar and horizontal cell processes. However, molecular mechanisms underlying cone synapse formation to mediate OFF pathways remain unknown. This study reveals that Necl-1/CADM3 is localized at S- and S/M-opsin-containing cones and dendrites of type 4 OFF cone bipolar cells (CBCs). In Necl-1-/- mouse retina, synapses between cones and type 4 OFF CBCs were dislocated, horizontal cell distribution became abnormal, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors were dislocated. Necl-1-/- mice exhibited aberrant short-wavelength-light-elicited signal transmission from cones to OFF CBCs, which was rescued by AMPA receptor potentiator. Additionally, Necl-1-/- mice showed impaired optokinetic responses. These findings suggest that Necl-1 regulates cone synapse formation to mediate OFF cone pathways elicited by short-wavelength light in mouse retina.
| S-EPMC11016759 | biostudies-literature
Project description:Specific wiring is essential for sensory systems to precisely relay information to higher brain regions. The retina, an approachable part of the brain, is an ideal model for studying neural circuits due to its well-organized structure. In the retina, S-cone photoreceptors sense and relay short-wavelength (e.g., blue) light signals for encoding color information and other environmental cues. S-cones usually account for less than 10% of cones and are precisely connected to S-cone bipolar cells (SCBCs). This connection is ancient and highly conserved across species, indicating essential functions. How this wiring specificity is formed and maintained, however, is not understood. To unveil the molecular mechanisms underlying this highly specific connection, we sequenced the transcriptomes of thirteen-lined ground squirrel (TLGS) photoreceptors. We chose TLGS for their cone-rich retina and the absence of cones that co-express multiple opsin proteins, as compared to mice. We used a targeted SMART-seq approach to obtain high-resolution transcriptomes from S- and M-cone photoreceptors and identified a cell-adhesion molecule, Nrxn3 , as a potential candidate mediating the S-cone to SCBC connection. Given the limitations of genetic manipulation in TLGS, we utilized mouse models to study the function of Nrxn3 in S-cones. In 'true' S-cones (S-opsin + /M-opsin - ) that lack Nrxn3 expression, the number of connections with SCBCs was drastically reduced, indicating a critical role of Nrxn3 for this synapse. While neurexins are well known for their diverse roles in regulating various synapses, this study is the first to document its crucial role in mediating or maintaining a specific synapse in the central nervous system. In addition, the differentially expressed genes identified here provide a valuable resource for further investigating cone subtype-specific functions.
| S-EPMC10002642 | biostudies-literature
Project description:Transgenic technology, immunocytochemistry, electrophysiology, intracellular injection techniques, and reverse transcription PCR were combined to study the expression of neuronal connexin36 (Cx36) in the outer plexiform layer of the mouse retina. Transgenic animals expressed either a fusion protein of full-length Cx36 with enhanced green fluorescent protein (EGFP) attached at the C terminus or exon 2 of Cx36 was replaced bybeta-galactosidase (beta-gal). In the outer nuclear layer,beta-gal-positive cell bodies, which were confined to the most distal region close to the outer limiting membrane, displayed immunoreactivity against S-cone opsin. Cx36-EGFP puncta colocalized with cone pedicles, which were visualized by intracellular injection. In reverse transcriptase PCR experiments, Cx36 mRNA was never detected in samples of rods harvested from the outer nuclear layer. These results strongly suggest expression of Cx36 in cones but not in rods. In vertical sections, Cx36 expression in the vitreal part of the outer plexiform layer was characterized by a patchy distribution. Immunocytochemistry with antibodies against the neurokinin-3 receptor and the potassium channel HCN4 (hyperpolarization-activated cyclic nucleotide-gated potassium channel) displayed clusters of the Cx36 label on the dendrites of OFF-cone bipolar cells. In horizontal sections, these clusters of Cx36 appeared as round or oval-shaped groups of individual puncta, and they were always aligned with the base of cone pedicles. Double-labeling experiments and single-cell reverse transcriptase PCR ruled out expression of Cx36 in horizontal cells and rod bipolar cells. At light microscopic resolution, we found close association of Cx36-EGFP with the AMPA-type glutamate receptor subunit GluR1 but not with GluR2-GluR4, the kainate receptor subunit GluR5, or the metabotropic glutamate receptor mGluR6.
| S-EPMC6730041 | biostudies-literature
Project description:Using constitutive GRF1/2 knockout mice, we showed previously that GRF2 is a key regulator of nuclear migration in retinal cone photoreceptors. To evaluate the functional relevance of that cellular process for two putative targets of the GEF activity of GRF2 (RAC1 and CDC42), here we compared the structural and functional retinal phenotypes resulting from conditional targeting of RAC1 or CDC42 in the cone photoreceptors of constitutive GRF2KO and GRF2WT mice. We observed that single RAC1 disruption did not cause any obvious morphological or physiological changes in the retinas of GRF2WT mice, and did not modify either the phenotypic alterations previously described in the retinal photoreceptor layer of GRF2KO mice. In contrast, the single ablation of CDC42 in the cone photoreceptors of GRF2WT mice resulted in clear alterations of nuclear movement that, unlike those of the GRF2KO retinas, were not accompanied by electrophysiological defects or slow, progressive cone cell degeneration. On the other hand, the concomitant disruption of GRF2 and CDC42 in the cone photoreceptors resulted, somewhat surprisingly, in a normalized pattern of nuclear positioning/movement, similar to that physiologically observed in GRF2WT mice, along with worsened patterns of electrophysiological responses and faster rates of cell death/disappearance than those previously recorded in single GRF2KO cone cells. Interestingly, the increased rates of cone cell apoptosis/death observed in single GRF2KO and double-knockout GRF2KO/CDC42KO retinas correlated with the electron microscopic detection of significant ultrastructural alterations (flattening) of their retinal ribbon synapses that were not otherwise observed at all in single-knockout CDC42KO retinas. Our observations identify GRF2 and CDC42 (but not RAC1) as key regulators of retinal processes controlling cone photoreceptor nuclear positioning and survival, and support the notion of GRF2 loss-of-function mutations as potential drivers of cone retinal dystrophies.
| S-EPMC10650203 | biostudies-literature
Project description:The mammalian retina comprises six major neuronal cell types and one glial type that are further classified into multiple subtypes based on their anatomical and functional differences. Nevertheless, how these subtypes arise remains largely unknown at the molecular level. Here, we demonstrate that the expression of Bhlhb5, a bHLH transcription factor of the Olig family, is tightly associated with the generation of selective GABAergic amacrine and Type 2 OFF-cone bipolar subtypes throughout retinogenesis. Targeted deletion of Bhlhb5 results in a significant reduction in the generation of these selective bipolar and amacrine subtypes. Furthermore, although a Bhlhb5-null mutation has no effect on the expression of bHLH-class retinogenic genes, Bhlhb5 expression overlaps with that of the pan-amacrine factor NeuroD and the expression of Bhlhb5 and NeuroD is negatively regulated by ganglion cell-competence factor Math5. Our results reveal that a bHLH transcription factor cascade is involved in regulating retinal cell differentiation and imply that Bhlhb5 functions downstream of retinogenic factors to specify bipolar and amacrine subtypes.
| S-EPMC2992969 | biostudies-literature
Project description:The effects of aging and light exposure on cone photoreceptor survival were compared between mouse retinas of neural retina leucine zipper knockout (Nrl(-/-)) mice and double-knockout mice lacking G-protein-coupled receptor kinase 1 (Nrl(-/-)Grk1(-/-)).Mice were reared in total darkness, ambient cyclic light, or constant light, and their retinas were evaluated from 1 to 9 months of age using immunohistochemistry, electroretinography, and fluorescein angiography. Retinal gene expression and statistically significant probe sets were categorized using analysis software. Select gene expression changes were confirmed with quantitative RT-PCR.In contrast to retinas from Nrl(-/-), those from Nrl(-/-)Grk1(-/-) exhibit a progressive loss of the outer nuclear layer, retinal physiology deficits, and a higher rate of degeneration with increasing age that is independent of environmental light exposure. Changes in retinal neovascularization occur in the Nrl(-/-)Grk1(-/-) at 1 month, before the onset of significant cone functional deficits. Microarray analyses demonstrate statistically significant changes in transcript levels of more than 400 genes, of which the oncostatin M signaling pathway and the inflammatory disease response network were identified.These data demonstrate that the loss of functional Grk1 on the enhanced S-cone Nrl(-/-) background exacerbates age-related cone dystrophy in a light-independent manner, mediated partly through the inflammatory response pathway and neovascularization. According to these findings, Grk1 helps to maintain a healthy cone environment, and the Nrl(-/-)Grk1(-/-) mouse allows examination of the alternative roles of Grk1 in cone photoreceptor homeostasis.
| S-EPMC3055752 | biostudies-literature
Project description:Sensory neurons downstream of primary receptors are selective for specific stimulus features, and they derive their selectivity both from excitatory and inhibitory synaptic inputs from other neurons and from their own intrinsic properties. Electrical synapses, formed by gap junctions, modulate sensory circuits. Retinal ganglion cells (RGCs) are diverse feature detectors carrying visual information to the brain, and receive excitatory input from bipolar cells and inhibitory input from amacrine cells (ACs). Here we describe a RGC that relies on gap junctions, rather than chemical synapses, to convey its selectivity for the orientation of a visual stimulus. This represents both a new functional role of electrical synapses as the primary drivers of feature selectivity and a new circuit mechanism for orientation selectivity in the retina.
| S-EPMC5725423 | biostudies-literature
Project description:Like most mammals, mice feature dichromatic color vision based on short (S) and middle (M) wavelength-sensitive cone types. It is thought that mammals share a retinal circuit that in dichromats compares S- and M-cone output to generate blue/green opponent signals, with bipolar cells (BCs) providing separate chromatic channels. Although S-cone-selective ON-BCs (type 9 in mouse) have been anatomically identified, little is known about their counterparts, the M-cone-selective OFF-BCs. Here, we characterized cone connectivity and light responses of selected mouse BC types using immunohistochemistry and electrophysiology. Our anatomical data indicate that four (types 2, 3a/b, and 4) of the five mouse OFF-BCs indiscriminately contact both cone types, whereas type 1 BCs avoid S-cones. Light responses showed that the chromatic tuning of the BCs strongly depended on their position along the dorsoventral axis because of the coexpression gradient of M- and S-opsin found in mice. In dorsal retina, where coexpression is low, most type 2 cells were green biased, with a fraction of cells (? 14%) displaying strongly blue-biased responses, likely reflecting S-cone input. Type 1 cells were also green biased but did not comprise blue-biased "outliers," consistent with type 1 BCs avoiding S-cones. We therefore suggest that type 1 represents the green OFF pathway in mouse. In addition, we confirmed that type 9 BCs display blue-ON responses. In ventral retina, all BC types studied here displayed similar blue-biased responses, suggesting that color vision is hampered in ventral retina. In conclusion, our data support an antagonistically organized blue/green circuit as the common basis for mammalian dichromatic color vision.
| S-EPMC6622657 | biostudies-literature
Project description:We previously reported strikingly normal morphologies and functional connectivities of regenerated retinal bipolar neurons (BPs) in zebrafish retinas sampled 60 days after a ouabain-mediated lesion of inner retinal neurons (60 DPI) (McGinn et al., 2018). Here we report early steps in the birth of BPs and formation of their dendritic trees and axonal arbors during regeneration. Adult zebrafish were subjected to ouabain-mediated lesion that destroys inner retinal neurons but spares photoreceptors and Müller glia, and were sampled at 13, 17, and 21 DPI, a timeframe over which plexiform layers reemerge. We show that this timeframe corresponds to reemergence of two populations of BPs (PKCα+ and nyx::mYFP+). Sequential BrdU, EdU incorporation reveals that similar fractions of PKCα+ BPs and HuC/D+ amacrine/ganglion cells are regenerated concurrently, suggesting that the sequence of neuronal production during retinal regeneration does not strictly match that observed during embryonic development. Further, accumulation of regenerated BPs appears protracted, at least through 21 DPI. The existence of isolated, nyx::mYFP+ BPs allowed examination of cytological detail through confocal microscopy, image tracing, morphometric analyses, identification of cone synaptic contacts, and rendering/visualization. Apically-projecting neurites (=dendrites) of regenerated BPs sampled at 13, 17, and 21 DPI are either truncated, or display smaller dendritic trees when compared to controls. In cases where BP dendrites reach the outer plexiform layer (OPL), numbers of dendritic tips are similar to those of controls at all sampling times. Further, by 13-17 DPI, BPs with dendritic tips reaching the outer nuclear layer (ONL) show patterns of photoreceptor connections that are statistically indistinguishable from controls, while those sampled at 21 DPI slightly favor contacts with double cone synaptic terminals over those of blue-sensitive cones. These findings suggest that once regenerated BP dendrites reach the OPL, normal photoreceptor connectomes are established, albeit with some plasticity. Through 17 DPI, some basally-projecting neurites (=axons) of regenerated nyx::mYFP+ BPs traverse long distances, branch into inappropriate layers, or appear to abruptly terminate. These findings suggest that, after a tissue-disrupting lesion, regeneration of inner retinal neurons is a dynamic process that includes ongoing genesis of new neurons and changes in BP morphology.
| S-EPMC6562337 | biostudies-literature
Project description:The neural retina is organized along central-peripheral, dorsal-ventral, and laminar planes. Cellular density and distributions vary along the central-peripheral and dorsal-ventral axis in species including primates, mice, fish, and birds. Differential distribution of cell types within the retina is associated with sensitivity to different types of damage that underpin major retinal diseases, including macular degeneration and glaucoma. Normal variation in retinal distribution remains unreported for multiple cell types in widely used research models, including mouse. Here we map the distribution of all known OFF bipolar cell (BC) populations and horizontal cells. We report significant variation in the distribution of OFF BC populations and horizontal cells along the dorsal-ventral and central-peripheral axes of the retina. Distribution patterns are much more pronounced for some populations of OFF BC cells than others and may correspond to the cell type's specialized functions.
| S-EPMC8009814 | biostudies-literature