Kavli Affiliate: Timothy Brown
| Authors: Abhi Aggarwal, Heather A. Baker, Celine D. Durst, I-Wen Chen, Pablo de Chambrier, Julia Marie Gonzales, Jonathan S. Marvin, Milene Vandal, Torgny Lundberg, Kenryo Sakoi, Ronak H Patel, Ching-Yao Wang, Frank Visser, Yannick Fouad, Smrithi Sunil, Matthew Wiens, Takuya Terai, Kei Takahashi-Yamashiro, Roger J. Thompson, Timothy A. Brown, Yusuke Nasu, Minh Dang Nguyen, Grant R.J. Gordon, Sarah McFarlane, Kaspar Podgorski, Antonius Holtmaat, Robert E. Campbell and Alexander W. Lohman
| Summary:
Genetically encoded calcium indicators (GECIs) are vital tools for fluorescence-based visualization of neuronal activity with high spatial and temporal resolution. However, current highest-performance GECIs are predominantly green or red fluorescent, limiting multiplexing options and efficient excitation with fixed-wavelength femtosecond lasers operating at 1030 nm. Here, we introduce OCaMP (also known as O-GECO2), an orange fluorescent GECI engineered from O-GECO1 through targeted substitutions to improve calcium affinity while retaining the favorable photophysical properties of mOrange2. OCaMP exhibits improved two-photon cross-section, responsiveness, photostability, and calcium affinity relative to O-GECO1. In cultured neurons, zebrafish, and mouse cortex, OCaMP outperforms the red GECIs jRCaMP1a and jRGECO1a in sensitivity, kinetics, and signal-to-noise ratio. These properties establish OCaMP as a robust tool for high-fidelity neural imaging optimized for 1030 nm excitation and a compromise-free option within the spectral gap between existing green and red GECIs.