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	4×	87	Yes
JF669	Far-red	7×	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