Fluorescent Genetically Encoded Calcium Indicators and Their In Vivo Application

Since the 1970s, the emergence and expansion of novel methods for calcium ion (Ca2+) detection have found diverse applications in vitro and in vivo across a series of model animal systems. Matched with advances in fluorescence imaging techniques, the improvements in the functional range and stability of various calcium indicators have significantly enhanced more accurate study of intracellular Ca2+ dynamics and its effects on cell signaling, growth, differentiation, and regulation. Nonetheless, the current limitations broadly presented by organic calcium dyes, genetically encoded calcium indicators, and calcium-responsive nanoparticles suggest a potential path toward more rapid optimization by taking advantage of a synthetic biology approach. This engineering-oriented discipline applies principles of modularity and standardization to redesign and interrogate endogenous biological systems. This review will elucidate how novel synthetic biology technologies constructed for eukaryotic systems can offer a promising toolkit for interfacing with calcium signaling and overcoming barriers in order to accelerate the process of Ca2+ detection optimization.

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Sensitive red protein calcium indicators for imaging neural activity

10.1101/041780 ◽

2016 ◽

Author(s):

Hod Dana ◽

Boaz Mohar ◽

Yi Sun ◽

Sujatha Narayan ◽

Andrew Gordus ◽

...

Keyword(s):

Neural Activity ◽

Emission Spectra ◽

Tissue Imaging ◽

C Elegans ◽

Calcium Indicators ◽

Large Populations ◽

Consequent Reduction ◽

Deep Tissue Imaging ◽

Genetically Encoded Calcium Indicators

Genetically encoded calcium indicators (GECIs) allow measurement of activity in large populations of neurons and in small neuronal compartments, over times of milliseconds to months. Although GFP-based GECIs are widely used for in vivo neurophysiology, GECIs with red-shifted excitation and emission spectra have advantages for in vivo imaging because of reduced scattering and absorption in tissue, and a consequent reduction in phototoxicity. However, current red GECIs are inferior to the state-of-the-art GFP-based GCaMP6 indicators for detecting and quantifying neural activity. Here we present improved red GECIs based on mRuby (jRCaMP1a, b) and mApple (jRGECO1a), with sensitivity comparable to GCaMP6. We characterized the performance of the new red GECIs in cultured neurons and in mouse, Drosophila, zebrafish and C. elegans in vivo. Red GECIs facilitate deep-tissue imaging, dual-color imaging together with GFP-based reporters, and the use of optogenetics in combination with calcium imaging.

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Imaging of the corneal nerves ex vivo and in vivo using genetically-encoded calcium indicators

Ophthalmic Technologies XXXI ◽

10.1117/12.2578018 ◽

2021 ◽

Author(s):

Matthew T. McPheeters ◽

Brecken J. Blackburn ◽

William J. Dupps ◽

Andrew M. Rollins ◽

Michael W. Jenkins

Keyword(s):

Ex Vivo ◽

Calcium Indicators ◽

Corneal Nerves ◽

Genetically Encoded Calcium Indicators

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Sensitive red protein calcium indicators for imaging neural activity

eLife ◽

10.7554/elife.12727 ◽

2016 ◽

Vol 5 ◽

Cited By ~ 368

Author(s):

Hod Dana ◽

Boaz Mohar ◽

Yi Sun ◽

Sujatha Narayan ◽

Andrew Gordus ◽

...

Keyword(s):

Neural Activity ◽

Emission Spectra ◽

Tissue Imaging ◽

C Elegans ◽

Calcium Indicators ◽

Large Populations ◽

Consequent Reduction ◽

Deep Tissue Imaging ◽

Genetically Encoded Calcium Indicators

Genetically encoded calcium indicators (GECIs) allow measurement of activity in large populations of neurons and in small neuronal compartments, over times of milliseconds to months. Although GFP-based GECIs are widely used for in vivo neurophysiology, GECIs with red-shifted excitation and emission spectra have advantages for in vivo imaging because of reduced scattering and absorption in tissue, and a consequent reduction in phototoxicity. However, current red GECIs are inferior to the state-of-the-art GFP-based GCaMP6 indicators for detecting and quantifying neural activity. Here we present improved red GECIs based on mRuby (jRCaMP1a, b) and mApple (jRGECO1a), with sensitivity comparable to GCaMP6. We characterized the performance of the new red GECIs in cultured neurons and in mouse, Drosophila, zebrafish and C. elegans in vivo. Red GECIs facilitate deep-tissue imaging, dual-color imaging together with GFP-based reporters, and the use of optogenetics in combination with calcium imaging.

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In vivo monitoring of neuronal activity with genetically encoded calcium indicators

Proceedings for Annual Meeting of The Japanese Pharmacological Society ◽

10.1254/jpssuppl.92.0_2-ms3 ◽

2019 ◽

Vol 92 (0) ◽

pp. 2-MS3

Author(s):

Natsuko Hitora-Imamura

Keyword(s):

Neuronal Activity ◽

In Vivo Monitoring ◽

Calcium Indicators ◽

Genetically Encoded Calcium Indicators

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Blind sparse deconvolution for inferring spike trains from fluorescence recordings

10.1101/156364 ◽

2017 ◽

Author(s):

Jérôme Tubiana ◽

Sébastien Wolf ◽

Georges Debregeas

Keyword(s):

Action Potentials ◽

Imaging Techniques ◽

Real Data ◽

Computational Framework ◽

Systems Neuroscience ◽

Neuronal Populations ◽

Calcium Indicators ◽

Genetically Encoded Calcium Indicators

The parallel developments of genetically-encoded calcium indicators and fast fluorescence imaging techniques makes it possible to simultaneously record neural activity of extended neuronal populations in vivo, opening a new arena for systems neuroscience. To fully harness the potential of functional imaging, one needs to infer the sequence of action potentials from fluorescence time traces. Here we build on recently proposed computational approaches to develop a blind sparse deconvolution algorithm (BSD), which we motivate by a theoretical analysis. We demonstrate that this method outperforms existing sparse deconvolution algorithms in terms of robustness, speed and/or accuracy on both synthetic and real fluorescence data. Furthermore, we provide solutions for the practical problems of thresholding and determination of the rise and decay time constants. We provide theoretical bounds on the performance of the algorithm in terms of precision-recall and temporal accuracy. Finally, we extend the computational framework to support temporal superresolution whose performance is established on real data.

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A positively tuned voltage indicator reveals electrical correlates of calcium activity in the brain

10.1101/2021.10.21.465345 ◽

2021 ◽

Author(s):

Stephen Wenceslao Evans ◽

Dongqing Shi ◽

Mariya Chavarha ◽

Mark Houston Plitt ◽

Jiannis Taxidis ◽

...

Keyword(s):

Temporal Resolution ◽

Calcium Imaging ◽

Photon Detection ◽

Temporal Precision ◽

Voltage Imaging ◽

Calcium Indicators ◽

Subthreshold Voltage ◽

Relationship Of ◽

Genetically Encoded Calcium Indicators

Neuronal activity is routinely recorded in vivo using genetically encoded calcium indicators (GECIs) and 2-photon microscopy, but calcium imaging is poorly sensitive for single voltage spikes under typical population imaging conditions, lacks temporal precision, and does not report subthreshold voltage changes. Genetically encoded voltage indicators (GEVIs) offer better temporal resolution and subthreshold sensitivity, but 2-photon detection of single spikes in vivo using GEVIs has required specialized imaging equipment. Here, we report ASAP4b and ASAP4e, two GEVIs that brighten in response to membrane depolarization, inverting the fluorescence-voltage relationship of previous ASAP-family GEVIs. ASAP4b and ASAP4e feature 180% and 210% fluorescence increases to 100-mV depolarizations, respectively, as well as modestly prolonged deactivation and high photostability. We demonstrate single-trial detection of spikes and oscillations in vivo with standard 1 and 2-photon imaging systems, and confirm improved temporal resolution in comparison to calcium imaging on the same equipment. Thus, ASAP4b and ASAP4e GEVIs extend the uses of existing imaging equipment to include multi-unit voltage imaging in vivo.

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