Early auto‐immune targeting of photoreceptor ribbon synapses in mouse models of multiple sclerosis

Dembla, Mayur; Kesharwani, Ajay; Natarajan, Sivaraman; Fecher‐Trost, Claudia; Fairless, Richard; Williams, Sarah K.; Flockerzi, Veit; Diem, Ricarda; Schwarz, Karin; Schmitz, Frank

doi:10.15252/emmm.201808926

Cited by 25 publications

(93 citation statements)

References 68 publications

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“…Super-Resolution Structured-Illumination-Microscopy (SR-SIM) was performed as previously described 36,37,44 . For SR-SIM, the ELYRA PS1 setup was used from Carl Zeiss Microscopy GmbH.…”

Section: Super-resolution Structured-illumination-microscopy (Sr-sim)mentioning

confidence: 99%

“…Immunolabeling of resin sections. For confocal imaging, immunolabeling was performed using 0.5 μm thin ("semi-thin") resin sections that were placed on glass coverslips, as previously described 36,37,44,47 . For Super-Resolution Structured Illumination Microscopy (SR-SIM) imaging, 1.5 μm thin resin sections were used to cover the entire synaptic terminal of a rod synapse.…”

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confidence: 99%

“…For Super-Resolution Structured Illumination Microscopy (SR-SIM) imaging, 1.5 μm thin resin sections were used to cover the entire synaptic terminal of a rod synapse. Processing of the resin sections was carried out similarly as previously described 36,37,44 . To remove the resin, resin sections were incubated with sodium methanolate (30% solution in methanol; Merck) for 12 min; 1:1 mixture of xylol/methanol for 12 min; acetone (2x) for 12 min; water for 2-3 min and PBS for 5 min.…”

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confidence: 99%

“…After several washes with PBS, binding of the primary antibodies was detected by incubation with corresponding secondary antibodies conjugated to the indicated fluorophores (1:1,000 dilutions; 3 hr, room temperature). Immunolabelled sections were embedded in antifade, as described before 36,37,44,47 . Negative controls were done by omitting primary antibodies and by using incubations of knockout sections, as indicated.…”

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confidence: 99%

“…oil objective was used for image acquisition with the 488 nm and 561 nm laser excitation lines. For quantitative analyses of experimental and control retinas, confocal images were acquired under identical conditions by using the ''re-use'' settings option of the NIS elements software, as previously described 37,44,47 . Quantitative analyses were performed in a blinded manner with the experimenter not knowing the identity of the samples.…”

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Synaptic ribbons foster active zone stability and illumination-dependent active zone enrichment of RIM2 and Cav1.4 in photoreceptor synapses

Dembla

Maxeiner

et al. 2020

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Rod photoreceptor synapses use large, ribbon-type active zones for continuous synaptic transmission during light and dark. Since ribbons are physically connected to the active zones, we asked whether illumination-dependent changes of ribbons influence Cav1.4/RIM2 protein clusters at the active zone and whether these illumination-dependent effects at the active zone require the presence of the synaptic ribbon. We found that synaptic ribbon length and the length of presynaptic Cav1.4/RIM2 clusters are tightly correlated. Dark-adaptation did not change the number of ribbons and active zone puncta. However, mean ribbon length and length of presynaptic Cav1.4/RIM2 clusters increased significantly during dark-adaptation when tonic exocytosis is highest. In the present study, we identified by the analyses of synaptic ribbon-deficient RIBEYE knockout mice that synaptic ribbons are (1) needed to stabilize Cav1.4/RIM2 at rod photoreceptor active zones and (2) are required for the darkness-induced active zone enrichment of Cav1.4/RIM2. These data propose a role of the ribbon in active zone stabilization and suggest a homeostatic function of the ribbon in illumination-dependent active zone remodeling. The active zone of the presynaptic terminal controls central aspects of presynaptic communication 1,2. It is a protein-rich, electron-dense specialization of the plasma membrane at which synaptic vesicle fusion preferentially occurs. The active zone is strongly enriched in voltage-gated Cav-channels and active zone proteins, e.g. RIM-proteins, that attach the vesicle fusion machinery in close proximity to the Cav-channels for tight coupling creating rapidly reacting nanodomains 1,3-9. Ribbon synapses are continuously active chemical synapses with specialized active zones that are considered to promote both fast, transient and slow, continuous synaptic vesicle exocytosis 10,11. The active zone of ribbon synapses is extended by large electron-dense structures, synaptic ribbons, that recruit additional vesicles to the active zone. The basal row of ribbon-associated vesicles is positioned close to the Cav-channels and represents the fastest releasable vesicle pool 12 ideally suited to signal the onset of a stimulus. Synaptic vesicles tethered to the ribbon body, i.e. in some distance from the active zone, are considered to replenish empty release sites at the active zone with slower release kinetics providing information predominantly about the length of the stimulus 12,13. The main structural component of ribbons is the ribbon-specific protein RIBEYE 14,15. Photoreceptor ribbon synapses are the first synapses in the visual system at which light signals are transmitted to the inner retina. Light induces hyperpolarization of photoreceptors and a decrease of exocytosis at the synapse 16. Rod synapses represent the majority of photoreceptor synapses in the mouse retina and are built in a morphologically fairly uniform manner. They use a single large active zone with a single large ribbon. In EM cross-sections, rod ribbons typically ap...

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“…Super-Resolution Structured-Illumination-Microscopy (SR-SIM) was performed as previously described 36,37,44 . For SR-SIM, the ELYRA PS1 setup was used from Carl Zeiss Microscopy GmbH.…”

Section: Super-resolution Structured-illumination-microscopy (Sr-sim)mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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