Rational design of a high-affinity, fast, red calcium indicator R-CaMP2

Masatoshi Inoue, Atsuya Takeuchi, Shin Ichiro Horigane, Masamichi Ohkura, Keiko Gengyo-Ando, Hajime Fujii, Satoshi Kamijo, Sayaka Takemoto-Kimura, Masanobu Kano, Junichi Nakai, Kazuo Kitamura, Haruhiko Bito

Research output: Contribution to journalArticlepeer-review

191 Citations (Scopus)


Fluorescent Ca 2+ reporters are widely used as readouts of neuronal activities. Here we designed R-CaMP2, a high-affinity red genetically encoded calcium indicator (GECI) with a Hill coefficient near 1. Use of the calmodulin-binding sequence of CaMKK- and CaMKK-2 in lieu of an M13 sequence resulted in threefold faster rise and decay times of Ca 2+ transients than R-CaMP1.07. These features allowed resolving single action potentials (APs) and recording fast AP trains up to 20-40 Hz in cortical slices. Somatic and synaptic activities of a cortical neuronal ensemble in vivo were imaged with similar efficacy as with previously reported sensitive green GECIs. Combining green and red GECIs, we successfully achieved dual-color monitoring of neuronal activities of distinct cell types, both in the mouse cortex and in freely moving Caenorhabditis elegans. Dual imaging using R-CaMP2 and green GECIs provides a powerful means to interrogate orthogonal and hierarchical neuronal ensembles in vivo.

Original languageEnglish
Pages (from-to)64-70
Number of pages7
JournalNature Methods
Issue number1
Publication statusPublished - 2014 Jan 1


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