Making sense of astrocytic calcium signals — from acquisition to interpretation

Semyanov, Alexey; Henneberger, Christian; Agarwal, Amit

doi:10.1038/s41583-020-0361-8

Cited by 157 publications

(160 citation statements)

References 138 publications

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“…Through Monte Carlo simulations, we found that the accuracy in identifying a pixel above a specific Ca 2+ threshold can be far below 95% confidence and varies with F 0 (see Supplementary Figure 3). We selected a set of six thresholds (0.2, 0.5, 1, 2, 5, 10) expressed in terms of ΔF/F 0 , where a Ca 2+ event reaching a threshold of 0.2 or 1 does not necessarily reflect a 20% or double increase in basal Ca 2+ concentration, respectively (see Semyanov et al 2020 8 ). In conjunction with proximity relationships of neighboring pixels (xyt), MTED identifies groups of Ca 2+ -positive pixels for a set of Ca 2+ thresholds, thereby allowing for dynamic region changes.…”

Section: Resultsmentioning

confidence: 99%

“…In our study, we used a common measure of fluorescence intensity and its changes (ΔF/F 0 ). While this quantification has its drawbacks, see for instance Semyanov et al 2020 8 , it is straight-forward and abundantly used throughout biomedical research and therefore suitable for testing the analytical approach and its versatility. Since the MTED algorithm is oblivious to the type of data it is working on and does not make specific assumption about it, it can be fed with more quantitative data (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…In return, the release of a variety of neurotransmitters has been shown to modulate the cytosolic Ca 2+ concentration ([Ca 2+ ]) in astrocytes 6 . Variations in astrocyte [Ca 2+ ] have been proposed to represent a unique manner of cellular signaling, but the exact functions and regulatory mechanisms are only slowly emerging 7,8 . Ca 2+ signals in astrocytes are not solely stimulus-dependent, but also occur spontaneously 9 .…”

Section: Introductionmentioning

confidence: 99%

“…A standard approach to analyzing Ca 2+ activity is fluorescence microscopy using Ca 2+ -sensitive fluorescent dyes 11 . They generally come in two flavors: organic dyes, such as Oregon Green 488 BAPTA-1 (OGB-1), and genetically encoded Ca 2+ indicators (GECIs), such as GCaMPs, which both have their specific advantages and disadvantages 8 . Both are easy to use in single channel recordings, which simplifies the readout and subsequent…”

Section: Introductionmentioning

confidence: 99%

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Deciphering spatio-temporal fluorescence changes using multi-threshold event detection (MTED)

Mueller

Cherkas

Stopper

et al. 2020

Preprint

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Recent achievements in indicator optimization and imaging techniques promote the exploration of Ca2+ activity patterns as a main second messenger in many organs. Astrocytes are important regulators of brain activity and well known for their Ca2+-dependent modulation of neurons. However, standardized methods to analyze and interpret Ca2+ activity recordings are missing and hindering global comparisons. Here, we present a biophysics-based concept to analyze Ca2+signals, which includes multiple thresholds and provides the experimenter with a comprehensive toolbox for a differentiated and in-depth characterization of Ca2+ signals. We analyzed various ex vivo and in vivo imaging datasets and verify the validity of our multi-threshold event detection (MTED) algorithm across Ca2+ indicators, imaging setups, and model systems from primary cell culture to awake, head-fixed mice. Applying our MTED concept enables standardized analysis and advances research using optical readouts of cellular activity to decrypt brain function. It allowed us to obtain new insights into the complex dependence of Ca2+activity patterns on temperature and neuronal activity.Highlights→We present a robust pixel-based algorithm to analyze multidimensional fluorescence data.→Automated multiple-threshold analysis accurately quantifies changes in fluorescence across magnitudes.→It characterizes the complexity of dynamic and overlapping activity patterns of Ca2+ activity of astrocytes in vitro, in situ, and in vivo.→Its application provides quantitative parameters how temperature and neuronal activity determine astrocytic Ca2+ activity.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Deciphering spatio-temporal fluorescence changes using multi-threshold event detection (MTED)

Mueller

Cherkas

Stopper

et al. 2020

Preprint

Self Cite

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“…At the core of the astroglial black box, intracellular Ca 2+signals remain loosely defined. Even though a variety of Ca 2+ signals have been mapped according to their spatiotemporal properties, still analysis and interpretation remain a major challenge (Nimmerjahn et al, 2009;Khakh and Sofroniew, 2015;Rusakov, 2015;Bazargani and Attwell, 2016;Bindocci et al, 2017;Stobart et al, 2018;Semyanov et al, 2020). So far, distinct Ca 2+ -signals have not been associated to specific intracellular signaling cascades or the nature of synaptic plasticity.…”

Section: Astroglial Ca 2+ Bottleneck: Upstream and Downstream Signal mentioning

confidence: 99%

The Paradox of Astroglial Ca2 + Signals at the Interface of Excitation and Inhibition

Caudal

Gobbo

Scheller

et al. 2020

Front. Cell. Neurosci.

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Astroglial networks constitute a non-neuronal communication system in the brain and are acknowledged modulators of synaptic plasticity. A sophisticated set of transmitter receptors in combination with distinct secretion mechanisms enables astrocytes to sense and modulate synaptic transmission. This integrative function evolved around intracellular Ca2+ signals, by and large considered as the main indicator of astrocyte activity. Regular brain physiology meticulously relies on the constant reciprocity of excitation and inhibition (E/I). Astrocytes are metabolically, physically, and functionally associated to the E/I convergence. Metabolically, astrocytes provide glutamine, the precursor of both major neurotransmitters governing E/I in the central nervous system (CNS): glutamate and γ-aminobutyric acid (GABA). Perisynaptic astroglial processes are structurally and functionally associated with the respective circuits throughout the CNS. Astonishingly, in astrocytes, glutamatergic as well as GABAergic inputs elicit similar rises in intracellular Ca2+ that in turn can trigger the release of glutamate and GABA as well. Paradoxically, as gliotransmitters, these two molecules can thus strengthen, weaken or even reverse the input signal. Therefore, the net impact on neuronal network function is often convoluted and cannot be simply predicted by the nature of the stimulus itself. In this review, we highlight the ambiguity of astrocytes on discriminating and affecting synaptic activity in physiological and pathological state. Indeed, aberrant astroglial Ca2+ signaling is a key aspect of pathological conditions exhibiting compromised network excitability, such as epilepsy. Here, we gather recent evidence on the complexity of astroglial Ca2+ signals in health and disease, challenging the traditional, neuro-centric concept of segregating E/I, in favor of a non-binary, mutually dependent perspective on glutamatergic and GABAergic transmission.

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Sensing Intra‐ and Extra‐Cellular Ca²⁺ in the Islet of Langerhans

Huang

Xie

et al. 2021

Adv Funct Materials

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Calcium ions (Ca2+) take part in intra‐ and inter‐cellular signaling to mediate cellular functions. Sensing this ubiquitous messenger is instrumental in disentangling the specific functions of cellular sub‐compartments and/or intercellular communications. In this review, the authors first describe intra‐ and inter‐cellular Ca2+ signaling in relation to insulin secretion from the pancreatic islets, and then outline the development of diverse sensors, for example, chemically synthesized indicators, genetically encoded proteins, and ion‐selective microelectrodes, for intra‐ and extra‐cellular sensing of Ca2+. Particular emphasis is placed on emerging approaches in this field, such as low‐affinity Ca2+ indicators and unique Ca2+‐responsive composite materials. The authors conclude by remarking on the challenges and opportunities for further developments in this field, which may facilitate a more comprehensive understanding of Ca2+ signaling within and outside the islets, and its relevance in health and disease.

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Making sense of astrocytic calcium signals — from acquisition to interpretation

Cited by 157 publications

References 138 publications

Deciphering spatio-temporal fluorescence changes using multi-threshold event detection (MTED)

Deciphering spatio-temporal fluorescence changes using multi-threshold event detection (MTED)

The Paradox of Astroglial Ca2 + Signals at the Interface of Excitation and Inhibition

Sensing Intra‐ and Extra‐Cellular Ca²⁺ in the Islet of Langerhans

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Making sense of astrocytic calcium signals — from acquisition to interpretation

Cited by 157 publications

References 138 publications

Deciphering spatio-temporal fluorescence changes using multi-threshold event detection (MTED)

Deciphering spatio-temporal fluorescence changes using multi-threshold event detection (MTED)

The Paradox of Astroglial Ca2 + Signals at the Interface of Excitation and Inhibition

Sensing Intra‐ and Extra‐Cellular Ca2+ in the Islet of Langerhans

Contact Info

Product

Resources

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Sensing Intra‐ and Extra‐Cellular Ca²⁺ in the Islet of Langerhans