Biology subjects

Nikonov, S.

Publications and source records attributed to Nikonov, S..

4 recordsLinked to original sources

bioRxiv2024

Fluorescent identification of axons, dendrites and soma of neuronal retinal ganglion cells with a genetic marker as a tool for facilitating the study of neurodegeneration

This study characterizes a fluorescent Slc17a6-tdTomato neuronal reporter mouse line offering strong labeling in axons throughout the optic nerve, dendrites and soma in 99% of retinal ganglion cells (RGCs). The model facilitates neuronal assessment ex vivo with wholemounts quantified to show neurodegeneration following optic nerve crush or elevated IOP as related to glaucoma, in vitro with robust Ca2+ responses to P2X7 receptor stimulation in neuronal cultures, and in vivo using a confocal scanning laser ophthalmoscope (cSLO). While the tdTomato signal showed strong overlap with RGC markers, BRN3A and RBPMS, there was no cross-labeling of displaced amacrine cells in the ganglion cell layer. Controls indicated no impact of Slc17a6-tdTomato expression on light-dependent neuronal function, as determined with a microelectrode array (MEA), or on structure, as measured with optical coherence tomography (OCT). In summary, this novel neuronal reporter mouse model offers an effective means to increase the efficiency for real-time, specific visualization of retinal ganglion cells. It holds substantial promise for enhancing our understanding of RGC pathology in glaucoma and other diseases of the optic nerve, and could facilitate the screening of targeted therapeutic interventions for neurodegeneration. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/599589v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@13db8dforg.highwire.dtl.DTLVardef@1345f10org.highwire.dtl.DTLVardef@14d34e1org.highwire.dtl.DTLVardef@1cacb87_HPS_FORMAT_FIGEXP M_FIG Graphical abstract. Fluorescent identification of axons, dendrites and soma of neuronal retinal ganglion cells with a genetic marker as a tool for facilitating the study of neurodegeneration. Puttipong Sripinun, Wennan Lu, Sergei Nikonov, Suhani Patel, Sarah Hennessy, Claire H. Mitchell*. This study delves into a new mouse model, featuring a fluorescent Slc17a6-tdTomato neuronal reporter. This model effectively labels axons in the optic nerve, as well as dendrites and soma in 99% of retinal ganglion cells (RGCs). This allows for both in vitro and in vivo assessment of neurodegeneration, offering a practical tool for real-time, precise visualization of RGCs, with potential applications in various fields of neuroscience and neurology. Created by Biorender.com. C_FIG

neuroscience↗

bioRxiv2024

Piezo1 and Piezo2 channels in retinal ganglion cells and the impact of Piezo1 stimulation on light-dependent neural activity

Piezo channels are associated with neuropathology in diseases like traumatic brain injury and glaucoma, but pathways linking tissue stretch to aberrant neural signaling remain unclear. The present study demonstrates that Piezo1 activation increases action potential frequency in response to light and the spontaneous dark signal from mouse retinal explants. Piezo1 stimulation was sufficient to increase cytoplasmic Ca2+ in soma and neurites, while stretch increased spiking activity in current clamp recordings from of isolated retinal ganglion cells (RGCs). Axon-marker beta-tubulin III colocalized with both Piezo1 and Piezo2 protein in the mouse optic nerve head, while RGC nuclear marker BRN3A colocalized with Piezo channels in the soma. Piezo1 was also present on GFAP-positive regions in the optic nerve head and colocalized with glutamine synthetase in the nerve fiber layer, suggesting expression in optic nerve head astrocytes and Muller glia end feet, respectively. Human RGCs from induced pluripotent stem cells also expressed Piezo1 and Piezo2 in soma and axons, while staining patterns in rats resembled those in mice. mRNA message for Piezo1 was greatest in the RPE/choroid tissue, while Piezo2 levels were highest in the optic nerve, with both channels also expressed in the retina. Increased expression of Piezo1 and Piezo2 occurred both 1 and 10 days after a single stretch in vivo; this increase suggests a potential role in rising sensitivity to repeated nerve stretch. In summary, Piezo1 and Piezo2 were detected in the soma and axons of RGCs, and stimulation affected the light-dependent output of RGCs. The rise in RGCs excitability induced by Piezo stimulation may have parallels to the early disease progression in models of glaucoma and other retinal degenerations. HighlightsO_LIActivation of Piezo1 excites retinal ganglion cells, paralleling the early neurodegenerative progression in glaucoma mouse models and retinal degeneration. C_LIO_LIPiezo1 and Piezo2 were expressed in axons and soma of retinal ganglion cells in mice, rats, and human iPSC-RGCs. C_LIO_LIFunctional assays confirmed Piezo1 in soma and neurites of neurons. C_LIO_LISustained elevation of Piezo1 and Piezo2 occurred after a single transient stretch may enhance damage from repeated traumatic nerve injury. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/599602v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@7bb1a0org.highwire.dtl.DTLVardef@cab0dcorg.highwire.dtl.DTLVardef@121690eorg.highwire.dtl.DTLVardef@7848fa_HPS_FORMAT_FIGEXP M_FIG Graphical abstract Piezo1 and Piezo2 channels in retinal ganglion cells and the impact of Piezo1 stimulation on light-dependent neural activity. Puttipong Sripinun, Lily P. See, Sergei Nikonov, Venkata Ramana Murthy Chavali, Vrathasha Vrathasha, Jie He, Joan M. OBrien, Jingsheng Xia, Wennan Lu, Claire H. Mitchell*. Activation of Piezo channels through mechanical or pharmacological stimulation leads to an influx of Ca2+ and other cations into RGCs, depolarizing the membrane and increasing the action potential frequency to modulate the visual signal. Created with Biorender.com C_FIG

neuroscience↗

bioRxiv2024

Enhancements in squid retinal responses to change of polarizations in a caustic shallow water

Marine animals with polarization vision are able to effectively detect moving objects in shallow waters, which are illuminated by dynamic fluctuations of downwelling light known as caustics. While behavioral studies across different animal species have demonstrated the support of polarization vision in moving object detection within this noisy environment, little is known about how their retinal photoreceptors, absorbing polarized photons, respond to moving objects, or how each photoreceptor contributes to the collective retinal reaction to changes in polarization. In this study, we employed multi-electrode array recordings to examine the retinal neural response of squid to polarized light stimuli that were designed to simulate caustics environment. Extracellular retinal recordings not only exhibit neural activities selective to the direction of polarization but also demonstrate a significant enhancement in response to stimuli with changing polarization compared to constant polarization. This enhancement is robust in almost all recording channels, but absent in a random permutation of the recordings from different trial types. These results suggest that the retinal photoreceptors directly encode the change of polarization stimuli, thereby contributing to signal detections with polarization vision. Together, our research represents a novel neural exploration of cephalopod polarization vision in a caustic environment, and advances our understanding of how nature parses scenes with salient, dynamic polarization in animal vision.

zoology↗

bioRxiv2019

Dual SMAD inhibition and Wnt inhibition enhances the differentiation of induced pluripotent stem cells into Retinal Ganglion cells (iPSC-RGCs)

Glaucoma is a group of progressive optic neuropathies that share common biological and clinical characteristics including irreversible changes to the optic nerve and visual field loss caused by death of retinal ganglion cells (RGCs). The loss of RGCs manifests as characteristic cupping or optic nerve degeneration, resulting in visual field loss in patients with Glaucoma. Published studies on in vitro RGC differentiation from stem cells utilized classical RGC signaling pathways mimicking retinal development in vivo. Although many strategies allowed for the generation of RGCs, increased variability between experiments and lower yield hampered the cross comparison between individual lines and between experiments. To address this critical need, we developed a reproducible chemically defined in vitro methodology for generating retinal progenitor cell (RPC) populations from iPSCs, that are efficiently directed towards RGC lineage. Using this method, we reproducibly differentiated iPSCs into RGCs with greater than 80% purity, without any genetic modifications. We used small molecules and peptide modulators to inhibit BMP, TGF-{beta} (SMAD), and canonical Wnt pathways that reduced variability between iPSC lines and yielded functional and mature iPSC-RGCs. Using CD90.2 antibody and Magnetic Activated Cell Sorter (MACS) technique, we successfully purified Thy-1 positive RGCs with nearly 95% purity.

neuroscience↗