@article {69846, title = {Far-red fluorescent genetically encoded calcium ion indicators.}, journal = {Nat Commun}, volume = {16}, year = {2025}, month = {2025 Apr 07}, pages = {3318}, abstract = {

Genetically encoded calcium ion (Ca) indicators (GECIs) are widely-used molecular tools for functional imaging of Ca dynamics and neuronal activities with single-cell resolution. Here we report the design and development of two far-red fluorescent GECIs, FR-GECO1a and FR-GECO1c, based on the monomeric far-red fluorescent proteins mKelly1 and mKelly2. FR-GECOs have excitation and emission maxima at ~596 nm and ~644 nm, respectively, display large responses to Ca in vitro (ΔF/F = 6 for FR-GECO1a, 18 for FR-GECO1c), are bright under both one-photon and two-photon illumination, and have high affinities (apparent K = 29 nM for FR-GECO1a, 83 nM for FR-GECO1c) for Ca. FR-GECOs offer sensitive and fast detection of single action potentials in neurons, and enable in vivo all-optical manipulation and measurement of cellular activities in combination with optogenetic actuators.

Preprint:\ https://doi.org/10.1101/2020.11.12.380089

}, keywords = {Action Potentials, Animals, Calcium, Fluorescent Dyes, HEK293 Cells, Humans, Luminescent Proteins, Mice, Neurons, Optogenetics, Red Fluorescent Protein}, issn = {2041-1723}, doi = {10.1038/s41467-025-58485-z}, url = {https://doi.org/10.1038/s41467-025-58485-z}, author = {Dalangin, Rochelin and Jia, Bill Z and Qi, Yitong and Aggarwal, Abhi and Sakoi, Kenryo and Drobizhev, Mikhail and Molina, Rosana S and Patel, Ronak and Abdelfattah, Ahmed S and Zheng, Jihong and Reep, Daniel and Hasseman, Jeremy P and Zhao, Yufeng and Wu, Jiahui and Podgorski, Kaspar and Tebo, Alison G and Schreiter, Eric R and Hughes, Thomas E and Terai, Takuya and Paquet, Marie-Eve and Megason, Sean G and Cohen, Adam E and Shen, Yi and Campbell, Robert E} } @article {69993, title = {RubyACRs Enable Red-Shifted Optogenetic Inhibition in Freely Behaving Drosophila}, journal = {bioRxiv}, year = {2025}, month = {2025 jun 15}, abstract = {

Optogenetic activators with red-shifted excitation spectra, such as Chrimson, have significantly advanced Drosophila neuroscience. However, until recently, available optogenetic inhibitors required shorter activation wavelengths, which don{\textquoteright}t penetrate tissue as effectively and are stronger visual stimuli to the animal, potentially confounding behavioral results. Here, we assess the efficacy of two newly identified anion-conducting channelrhodopsins with spectral sensitivities similar to Chrimson: A1ACR and HfACR (RubyACRs). Electrophysiology and functional imaging confirmed that RubyACRs effectively hyperpolarize neurons, with stronger and faster effects than the widely used inhibitor GtACR1. Activation of RubyACRs led to circuit-specific behavioral changes in three different neuronal groups. In glutamatergic motor neurons, activating RubyACRs suppressed adult locomotor activity. In PPL1-γ1pedc dopaminergic neurons, pairing odors with RubyACR activation during learning produced odor responses consistent with synaptic silencing. Finally, activation of RubyACRs in the pIP10 neuron suppressed pulse song during courtship. Together, these results demonstrate that RubyACRs are effective and reliable tools for neuronal inhibition in Drosophila, expanding the optogenetic toolkit for circuit dissection in freely behaving animals.

Preprint: https://www.biorxiv.org/content/early/2025/06/15/2025.06.13.659144

}, doi = {10.1101/2025.06.13.659144}, url = {https://www.biorxiv.org/content/early/2025/06/15/2025.06.13.659144}, author = {Bushey, Daniel and Shiozaki, Hiroshi and Shuai, Yichun and Zheng, Jihong and Jayaraman, Vivek and Hasseman, Jeremy P. and Kolb, Ilya and GENIE Project Team and Turner, Glenn C.} } @article {68772, title = {Glutamate indicators with improved activation kinetics and localization for imaging synaptic transmission.}, journal = {Nature Methods}, volume = {20}, year = {2023}, month = {2023 Jun 01}, abstract = {

The fluorescent glutamate indicator iGluSnFR enables imaging of neurotransmission with genetic and molecular specificity. However, existing iGluSnFR variants exhibit low in vivo signal-to-noise ratios, saturating activation kinetics and exclusion from postsynaptic densities. Using a multiassay screen in bacteria, soluble protein and cultured neurons, we generated variants with improved signal-to-noise ratios and kinetics. We developed surface display constructs that improve iGluSnFR{\textquoteright}s nanoscopic localization to postsynapses. The resulting indicator iGluSnFR3 exhibits rapid nonsaturating activation kinetics and reports synaptic glutamate release with decreased saturation and increased specificity versus extrasynaptic signals in cultured neurons. Simultaneous imaging and electrophysiology at individual boutons in mouse visual cortex showed that iGluSnFR3 transients report single action potentials with high specificity. In vibrissal sensory cortex layer 4, we used iGluSnFR3 to characterize distinct patterns of touch-evoked feedforward input from thalamocortical boutons and both feedforward and recurrent input onto L4 cortical neuron dendritic spines.

}, issn = {1548-7105}, doi = {10.1038/s41592-023-01863-6}, author = {Aggarwal, Abhi and Liu, Rui and Chen, Yang and Ralowicz, Amelia J and Bergerson, Samuel J and Tomaska, Filip and Mohar, Boaz and Hanson, Timothy L and Hasseman, Jeremy P and Reep, Daniel and Tsegaye, Getahun and Yao, Pantong and Ji, Xiang and Kloos, Marinus and Walpita, Deepika and Patel, Ronak and Mohr, Manuel A and Tillberg, Paul W and Looger, Loren L and Marvin, Jonathan S and Hoppa, Michael B and Konnerth, Arthur and Kleinfeld, David and Schreiter, Eric R and Podgorski, Kaspar} }