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PinkyCaMP: an mScarlet-based calcium sensor with enhanced brightness, photostability and multiplexing capabilities.

Nature methods

Authors: Ryan Fink, Shosei Imai, Nala Gockel, German Lauer, Kim Renken, Jonas Wietek, Paul J Lamothe-Molina, Falko Fuhrmann, Manuel Mittag, Tim Ziebarth, Annika Canziani, Martin Kubitschke, Vivien Kistmacher, Anny Kretschmer, Eva Sebastian, Jana Ottens, Dietmar Schmitz, Takuya Terai, Jan Gründemann, Sami I Hassan, Tommaso Patriarchi, Andreas Reiner, Martin Fuhrmann, Robert E Campbell, Olivia Andrea Masseck

Genetically encoded calcium (Ca) indicators (GECIs) are essential tools for monitoring neuronal activity, but the performance of red fluorescent GECIs has remained limited. In particular, many red indicators are relatively dim, produce low signal-to-noise ratios and can undergo unwanted photoswitching when exposed to blue light, restricting their use in all-optical experiments that combine imaging with optogenetics or multicolor imaging. Here we show the development of PinkyCaMP, a Ca sensor based on the bright red fluorescent protein mScarlet. PinkyCaMP exhibits markedly improved brightness, photostability and signal-to-noise ratio compared to existing red GECIs, while remaining fully compatible with blue-light-based optogenetic and dual-color imaging approaches. PinkyCaMP is well-tolerated by neurons, showing no detectable toxicity or aggregation, both in vitro and in vivo. PinkyCaMP enables a broad spectrum of imaging modalities, including single-photon methods, such as fiber photometry, widefield imaging and miniature microscopy imaging, as well as two-photon imaging in awake mice.

© 2026. The Author(s).

PMID: 42032066

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