Gap Junctions in A8 Amacrine Cells Are Made of Connexin36 but Are Differently Regulated Than Gap Junctions in AII Amacrine Cells

Yadav, Shubhash Chandra; Tetenborg, Stephan; Dedek, Karin

doi:10.3389/fnmol.2019.00099

Cited by 19 publications

(24 citation statements)

References 56 publications

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“…Recent work indicates that gap junctions are also involved in progressive cell death and aberrant activity seen in various pathological conditions of the retina (Akopian et al, 2014(Akopian et al, , 2017Ivanova et al, 2015;O'Brien and Bloomfield, 2018). Because of the characteristics of high plasticity and relation to activity-dependent synaptic input, gap junctions tune retinal microcircuits for processing of visual information under different conditions (Fischer and Stell, 1999;Bloomfield and Volgyi, 2004;Urschel et al, 2006;O'Brien and Bloomfield, 2018;Yadav et al, 2019).…”

Section: Gap Junction In Aii Acs and Retinal Signalingmentioning

confidence: 99%

Increased Connexin36 Phosphorylation in AII Amacrine Cell Coupling of the Mouse Myopic Retina

Banerjee

Wang

Zhao

et al. 2020

Front. Cell. Neurosci.

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Myopia is a substantial public health problem worldwide. In the myopic retina, distant images are focused in front of the photoreceptors. The cells and mechanisms for retinal signaling that account either for emmetropization (i.e., normal refraction) or for refractive errors have remained elusive. Gap junctions play a key component in enhancement of signal transmission in visual pathways. AII amacrine cells (ACs), coupled by connexin36, segregate signals into ON and OFF pathways. Coupling between AII ACs is actively modulated through phosphorylation at serine 293 via dopamine in the mouse retina. In this study, form deprivation mouse myopia models were used to evaluate the expression patterns of connexin36-positive plaques (structural assay) and the state of connexin36 phosphorylation (functional assay) in AII ACs, which was green fluorescent protein-expressing in the Fam81a mouse line. Single-cell RNA sequencing showed dopaminergic synapse and gap junction pathways of AII ACs were downregulated in the myopic retina, although Gjd2 mRNA expression remained the same. Compared with the normal refractive eye, phosphorylation of connexin36 was increased in the myopic retina, but expression of connexin36 remained unchanged. This increased phosphorylation of Cx36 could indicate increased functional gap junction coupling of AII ACs in the myopic retina, a possible adaptation to adjust to the altered noisy signaling status.

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Section: Gap Junction In Aii Acs and Retinal Signalingmentioning

confidence: 99%

Increased Connexin36 Phosphorylation in AII Amacrine Cell Coupling of the Mouse Myopic Retina

Banerjee

Wang

Zhao

et al. 2020

Front. Cell. Neurosci.

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“…Rather, S3-Gbx2+ ACs are heterotypically coupled with neighboring bipolar cells (BCs). Heterotypic coupling between ACs and bipolar cells is unusual and has only been observed in glycinergic AII and A8 ACs with cone BCs (Vaney, 1991;Yadav et al, 2019). The spatial pattern of the S3-Gbx2+ AC:BC tracer coupling is also unusual, as it never extends beyond the central 80% of the dendritic arbor of the S3-Gbx2+ AC.…”

Section: Modes Of Neurotransmission In S3-gbx2+ Acsmentioning

confidence: 99%

Gbx2 identifies two amacrine cell subtypes with distinct molecular, morphological, and physiological properties

Kerstein

Leffler

Sivyer

et al. 2020

Preprint

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Our understanding of how the nervous sytem works is limited by our ability to identify the neuronal subtypes that comprise functional circuits. Using a genetic approach, we show that the transcription factor Gbx2 labels two amacrine cell (AC) subtypes in the mouse retina that have distinct morphological, physiological, and molecular properties. One subtype of Gbx2+ ACs are likely the previously characterized On-type GABAergic CRH-1 AC. The other Gbx2+ AC population is a previously uncharacterized non-GABAergic, non-Glycinergic (nGnG) AC subtype. Gbx2+ nGnG ACs are On-Off type cells with asymmetric dendritic arbors. Gbx2+ nGnG ACs also exhibit tracer coupling to bipolar cells (BCs) through gap junctions that are modulated by dopamine signaling. This study genetically identifies a previously uncharacterized AC subtype and reveals an unusual AC-BC connectivity through gap junctions that may provide a novel model of synaptic communication and visual circuit function. RESULTS Gbx2 CreERT2-IRES-EGFP marks two distinct amacrine cell subtypes.To begin unraveling the neuronal subtype complexity in the retina, we sought to identify Cre or CreERT2 mouse lines that could be used to selectively label and manipulate single neuronal subtypes in the retina. Using scRNAseq datasets and transgenic mouse databases as a guide (Siegert et al., 2009;Macosko et al., 2015), we identified Gbx2 CreERT2-IRES-EGFP as a mouse line predicted to label a sparse population of neurons in the retina (Chen et al., 2009). Since the CreERT2-IRES-EGFP cassette is knocked into the Gbx2 locus, labeled neurons are expected to faithfully recapitulate its endogenous expression pattern. Crossing the Gbx2 CreERT2-IRES-EGFP line to multiple Credependent reporter lines labeled neurons in the inner nuclear layer (INL, Fig. 1a) and the ganglion cell layer (GCL, Fig. 1b). Low doses of tamoxifen (<0.02mg) labeled neurons in both the INL and GCL with dendrites that selectively stratify in sublamina 3 (S3) of the inner plexiform layer (IPL). When we used a saturating dose of tamoxifen (2.0 mg/day for 2 days, Fig. S1d-i), we observed a second neuronal subtype with dendrites that stratify in sublamina 5 (S5) of the IPL (Fig. 1c, g). Importantly, the same two neuronal populations were labeled whether tamoxifen was administered at embryonic (E16), postnatal (P0-2), or adult (P28) ages ( Fig. 1 -supplement 1a-c), demonstrating that the Gbx2 CreERT2-IRES-EGFP line provides a consistent and stable method for labeling the same neuronal populations from embryonic to adult stages.Both the S3-and S5-stratifying Gbx2+ populations co-localized with pan-amacrine cell markers TFAP2 and Pax6 (Fig. 1d, h, Fig 1-supplement 2a), and lacked expression of the retinal ganglion cell marker RBPMS and bipolar cell marker Chx10 (Fig. 1h, Fig 1supplement 2b, c). GFP expression could be detected in 55.3% of the total Gbx2/tdTomato+ population (Fig. 1e, i). A second marker, calretinin, labeled 53.6% of the total Gbx2+ ACs (Fig. 1f, i) and nearly all (94.9%) of the GFP+ Gbx2+ ACs were colabeled ...

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“…I S. 1934). The experiments in this study were conducted with C57BL/6J, Cx36+/− Cx36-EGFP mice (comparable to Cx36+/+ Cx36-EGFP mice, see Meyer et al, 2014), CaMKII-β +/+ and CaMKII-β −/− mice (Kool et al, 2016), and Ier5-GFP mice (Siegert et al, 2009; Yadav et al, 2019). Mice were deeply anesthetized with CO 2 and killed by cervical dislocation.…”

Section: Methodsmentioning

confidence: 99%

“…Alexa Fluor 568 potassium hydrazide was injected into AII and A8 amacrine cells in C57BL/6J and Ier5-GFP mouse retina, respectively, as described earlier (Meyer et al, 2018; Yadav et al, 2019). Retinal pieces from C57BL/6J mice were incubated in 0.0005% DAPI solution for 45–60 min ahead of dye injections in order to visualize AII cell somata.…”

Section: Methodsmentioning

confidence: 99%

“…The vast majority of retinal Cx36 is expressed in AII amacrine cells (Feigenspan et al, 2001; Meyer et al, 2014), which integrate rod-generated signals and transmit them via gap junctions into the cone pathway to enable scotopic vision (Güldenagel et al, 2001; Deans et al, 2002). Apart from the AII amacrine cell, Cx36 was also identified in photoreceptors (Feigenspan et al, 2004; Bolte et al, 2016), bipolar cells (Feigenspan et al, 2004; Han and Massey, 2005), ganglion cells (Schubert et al, 2005; Pan et al, 2010), and other amacrine cells (Brüggen et al, 2015; Yadav et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Localization of Retinal Ca2+/Calmodulin-Dependent Kinase II-β (CaMKII-β) at Bipolar Cell Gap Junctions and Cross-Reactivity of a Monoclonal Anti-CaMKII-β Antibody With Connexin36

Tetenborg

Yadav

Brüggen

et al. 2019

Front. Mol. Neurosci.

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Neuronal gap junctions formed by connexin36 (Cx36) and chemical synapses share striking similarities in terms of plasticity. Ca 2+ /calmodulin-dependent protein kinase II (CaMKII), an enzyme known to induce memory formation at chemical synapses, has recently been described to potentiate electrical coupling in the retina and several other brain areas via phosphorylation of Cx36. The contribution of individual CaMKII isoforms to this process, however, remains unknown. We recently identified CaMKII-β at electrical synapses in the mouse retina. Now, we set out to identify cell types containing Cx36 gap junctions that also express CaMKII-β. To ensure precise description, we first tested the specificity of two commercially available antibodies on CaMKII-β-deficient retinas. We found that a polyclonal antibody was highly specific for CaMKII-β. However, a monoclonal antibody (CB-β-1) recognized CaMKII-β but also cross-reacted with the C-terminal tail of Cx36, making localization analyses with this antibody inaccurate. Using the polyclonal antibody, we identified strong CaMKII-β expression in bipolar cell terminals that were secretagogin- and HCN1-positive and thus represent terminals of type 5 bipolar cells. In these terminals, a small fraction of CaMKII-β also colocalized with Cx36. A similar pattern was observed in putative type 6 bipolar cells although there, CaMKII expression seemed less pronounced. Next, we tested whether CaMKII-β influenced the Cx36 expression in bipolar cell terminals by quantifying the number and size of Cx36-immunoreactive puncta in CaMKII-β-deficient retinas. However, we found no significant differences between the genotypes, indicating that CaMKII-β is not necessary for the formation and maintenance of Cx36-containing gap junctions in the retina. In addition, in wild-type retinas, we observed frequent association of Cx36 and CaMKII-β with synaptic ribbons, i.e., chemical synapses, in bipolar cell terminals. This arrangement resembled the composition of mixed synapses found for example in Mauthner cells, in which electrical coupling is regulated by glutamatergic activity. Taken together, our data imply that CaMKII-β may fulfill several functions in bipolar cell terminals, regulating both Cx36-containing gap junctions and ribbon synapses and potentially also mediating cross-talk between these two types of bipolar cell outputs.

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Gap Junctions in A8 Amacrine Cells Are Made of Connexin36 but Are Differently Regulated Than Gap Junctions in AII Amacrine Cells

Cited by 19 publications

References 56 publications

Increased Connexin36 Phosphorylation in AII Amacrine Cell Coupling of the Mouse Myopic Retina

Increased Connexin36 Phosphorylation in AII Amacrine Cell Coupling of the Mouse Myopic Retina

Gbx2 identifies two amacrine cell subtypes with distinct molecular, morphological, and physiological properties

Localization of Retinal Ca2+/Calmodulin-Dependent Kinase II-β (CaMKII-β) at Bipolar Cell Gap Junctions and Cross-Reactivity of a Monoclonal Anti-CaMKII-β Antibody With Connexin36

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