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Neurophotonics for Peripheral Nerves
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
Ashfaq Ahmed, Yuqiang Bai, Jessica C. Ramella-Roman, Ranu Jung
So far, optogenetics has been used to great effect in the brain (Yizhar et al., 2011). Its application in the PNS has been limited to a few studies (Wang and Zylka, 2009; Llewellyn et al., 2010; Sharp and Fromherz, 2011; Ji et al., 2012; Liske et al., 2013). It has been used to both activate (Llewellyn et al., 2010) and inhibit (Liske et al., 2013) motor neuron axons in anesthetized transgenic mice. Channelrhodopsin-2 has been used to excite neurons by depolarization. Halorhodopsin, which responds to light near 580 nm is used to inhibit excitation of neurons by hyperpolarization (Zhang et al., 2007b; Gradinaru et al., 2010). Optogenetic approaches have also been utilized to further our understanding of neural disorders (Tye and Deisseroth, 2012), neural systems, and encoding (Monesson-Olson et al., 2014). Recently optogenetic approaches have been proposed for the cure of blindness and Parkinson’s disease (Gradinaru et al., 2009; Kramer et al., 2009; Carter and de Lecea, 2011).
Untangling Appetite Circuits with Optogenetics and Chemogenetics
Published in Ruth B.S. Harris, Appetite and Food Intake, 2017
The most widely used opsin to stimulate neural activity is channelrhodopsin2 (ChR2), a nonselective cation channel isolated from algae, which leads to action potential firing upon blue light photostimulation (Figure 5.1F) (Boyden et al. 2005). For cell silencing, common opsins are the chloride pump halorhodopsin (eNpHR) (Gradinaru, Thompson, and Deisseroth 2008, Zhang et al. 2007) and the hydrogen pump archaerhodopsin-3 (Arch) (Chow et al. 2010) that enables hyperpolarization of membranes to eliminate the production of action potentials upon yellow light photoinhibition (Figure 5.1G). Recently, structure guided protein engineering was utilized to convert ChR2 (originally cation-conducting) into chloride-conducting anion channels, resulting in more physiological, efficient, and sensitive optogenetic inhibition (Figure 5.1H) (Berndt et al. 2014, Wietek et al. 2014).
Genetic and epigenetic studies of opioid abuse disorder – the potential for future diagnostics
Published in Expert Review of Molecular Diagnostics, 2023
Sarah Abdulmalek, Gary Hardiman
From the VTA, the DRN receives mainly GABAergic stimulations, which have different reward-related behavioral outcomes. A study by Y. Li. et al. showed that rostral VTA (rVTA) projections led to disinhibition of DRN serotonergic neurons by inhibiting local GABAergic neurons, whereas caudal VTA (cVTA) inputs directly inhibited serotonergic neurons. The study used Gad2-IRES-Cre mice expressing channelrhodopsin 2 (ChR2) or N. pharaonis halorhodopsin (NpHR) in the rostral and caudal VTA GABAergic neurons. To allow light-mediated inhibition or activation of the r-cVTA inputs to the DRN, they implanted optical fibers above the DRN. Photoactivation of rVTA – DRN signaling pathway produced place aversion while photoactivation of the cVTA – DRN pathway produced real-time place preference in mice. Activation of VTA MOR depressed the rVTA – DRN signaling pathway and subsequently blocked place aversion in mice [49].
Beta-cell hubs maintain Ca2+ oscillations in human and mouse islet simulations
Published in Islets, 2018
Chon-Lok Lei, Joely A. Kellard, Manami Hara, James D. Johnson, Blanca Rodriguez, Linford J.B. Briant
The findings of Johnston et al.33 are impressive and convincing, but, like all studies, their work was not without limitations. Their imaging methodology consisted of recording Ca2+ oscillations in all β-cells in a 20 µm confocal plane. In a spherical islet, this would typically be the first two layers of cells on the surface of the islet, amounting to ~50-100 cells, or ~5-15% of all β-cells in the entire islet36; hence, the conclusions of the study are limited to the ‘imaged plane’, and do not extend to the whole islet. In particular, it is not clear if hub inhibition influences Ca2+ activity in the entire islet, or just Ca2+ activity in the imaged network. Secondly, to allow selective inhibition of identified hubs, Johnston et al.33 used a transgenic mouse line that expressed halorhodopsin in β-cells - an approach that would be difficult to implement in human islets. How, then, do these findings in mice translate to human islets? It is important to carefully consider this question, because mouse and human islets display different β-cell Ca2+ dynamics; mouse β-cells display islet-wide synchrony in response to glucose, whereas synchrony in human β-cells is constrained to localized subpopulations.37 These differences likely stem from the differences in human and mouse islet architectures: mouse islets have a highly connected β-cell core, whereas β-cells in human islets occur in distinct clusters.38-40
CRISPR Cas9 based genome editing in inherited retinal dystrophies
Published in Ophthalmic Genetics, 2021
Mayank Bansal, Sundaram Acharya, Saumya Sharma, Rhythm Phutela, Riya Rauthan, Souvik Maiti, Debojyoti Chakraborty
In the optogenetics strategy for retinal dystrophies, the broad principle has been to introduce light sensitive proteins to the surviving inner retinal cells such as the bipolar cells or retinal ganglion cells. The light sensitive proteins used for optogenetics include opsins derived from microbes, e.g. halorhodopsin and channelrhodopsin, or those derived from mammals, e.g. rhodopsin, medium wave cone opsin, and melanopsin (13). Further, optical control of CRISPR has been designed and studied, by using light activated proteins. In this method, caged amino acids are incorporated into the Cas9 protein. On light exposure, the amino acids become surface exposed, with activation of the Cas9 enzyme (14).