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WHaloCaMP: Modular, Bright, and Multiplexable Chemigenetic Calcium Indicators

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WHaloCaMP: Modular, Bright, and Multiplexable Chemigenetic Calcium Indicators

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A modular chemigenetic calcium indicator for multiplexed in vivo functional imaging

Overview

WHaloCaMP sensors integrate the high-performance Janelia Fluor dyes with genetically engineered HaloTag proteins for modular, tunable calcium imaging in living systems. This platform offers multiple dye options, works in live animals, and supports high-speed, multicolor, and fluorescence lifetime imaging. Fluorescence change in WHaloCaMP results from reversible quenching of the bound dye via a strategically placed tryptophan.


Key Advantages

  • Spectral Flexibility
    WHaloCaMP functions with JF dyes across the spectrum:

    • Green (JF494)

    • Orange (JF552)

    • Far-Red (JF669)

    • Near-IR (JF722)

  • Multiplexing Ready
    Combine WHaloCaMP with GFP or red indicators (e.g., jRGECO1b, iGlucoSnFR) for 3-color imaging in zebrafish, flies, and mice.

  • Live-Animal Compatible
    Effective in vivo labeling by retro-orbital injection of dye; functional in cortex, brainstem, retina, and more.

  • Quantitative Imaging
    Enables FLIM (fluorescence lifetime imaging microscopy)-based calcium quantification via lifetime changes up to 2.1 ns.


Performance Snapshot

Dye

Color

ΔF/F₀

Kd (nM)

Bioavailable In Vivo?

JF494

Green

10×

71

Yes

JF552

Orange

87

Yes

JF669

Far-red

37

Yes

JF722

Near-IR

16× (in vitro)

26

No


Applications

  • In vivo Ca²⁺ imaging in flies, zebrafish, and mice

  • Two-photon and light-sheet imaging

  • Astrocyte-neuron co-imaging

  • Signal multiplexing with kinase and metabolite reporters


WHaloCaMP: Switchable color. Superior brightness. Functional depth.
Compatible with your favorite JF dyes and imaging workflows.

Reference: Farrants, H., Shuai, Y., Lemon, W.C. et al. A modular chemigenetic calcium indicator for multiplexed in vivo functional imaging. Nat Methods 21, 1916–1925 (2024). https://doi.org/10.1038/s41592-024-02411-6

IP Coverage: US Patent Application 18/318,997

Tech ID: 2022-012

Available Plasmids from Addgene for non-profits and Janelia for for-profit licensing: 

Plasmid

Purpose

p10xUAS-WHaloCaMP1a-EGFP

Expression of WHaloCaMP1a-EGFP in Drosophila using GAL4 driver

pCAG-WHaloCaMP1a-EGFP

Expression of WHaloCaMP1a-EGFP in mammalian cells from the CAG promoter

pTol2-elavl3-WHaloCaMP1a

Expression of WHaloCaMP1a in zebrafish from the elavl3 promoter (pan-neuronal expression)

pTol2-elavl3-WHaloCaMP1a-EGFP

Expression of WHaloCaMP1a-EGFP in zebrafish from the elavl3 promoter (pan-neuronal expression)

pAAV-CaMKII-WHaloCaMP1a

Production of AAV particles encoding WHaloCaMP1a from the CaMKII promoter

pAAV-CaMKII-WHaloCaMP1a-EGFP

Production of AAV particles encoding WHaloCaMP1a-EGFP from the CaMKII promoter

pAAV-synapsin-WHaloCaMP1a

Production of AAV particles encoding WHaloCaMP1a from the synapsin promoter

pAAV-synapsin-WHaloCaMP1a-EGFP

Production of AAV particles encoding WHaloCaMP1a-EGFP from the synapsin promoter

pRSET-WHaloCaMP-eNOSpep-EGFP

Expression of WHaloCaMP-eNOSpep-EGFP fusion in E. coli

pRSET-WHaloCaMP1b-EGFP

Expression of WHaloCaMP1b-EGFP fusion in E. coli


pTol2-elavl3-WHaloCaMP1a

Expression of WHaloCaMP-eNOSpep-EGFP fusion in E. coli

pTol2-elavl3-WHaloCaMP1a-EGFP

Expression of WHaloCaMP1b-EGFP fusion in E. coli

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In vivo calcium imaging in a mouse expressing WHaloCaMP1b-GFP in the visual cortex, labeled with JF669-HTL after retro orbital injection
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