A genetically encoded near-infrared fluorescent calcium ion indicator

Area of Science:

• Biophysics
• Neuroscience
• Molecular Biology

Background:

• Genetically encoded calcium ion (Ca2+) indicators (GECIs) are crucial for monitoring cellular activity.
• Existing GECIs primarily operate in the visible light spectrum, limiting multicolor imaging and deep tissue penetration.
• There is a need for GECIs that function in the near-infrared (NIR) spectrum.

Purpose of the Study:

• To report a novel intensiometric, NIR fluorescent GECI, designated NIR-GECO1.
• To characterize the excitation and emission properties of NIR-GECO1.
• To evaluate the performance of NIR-GECO1 for Ca2+ imaging in biological samples.

Main Methods:

• Development of a genetically encoded indicator with NIR fluorescence.
• Spectroscopic characterization of excitation and emission maxima (678 nm and 704 nm).
• Intensiometric imaging of Ca2+ transients in cultured mammalian cells and ex vivo brain tissue.

Main Results:

• NIR-GECO1 exhibits excitation and emission maxima at 678 nm and 704 nm, respectively.
• The GECI demonstrates sensitivity for Ca2+ transient imaging comparable to visible-wavelength GECIs.
• Successful imaging of Ca2+ dynamics in cultured cells and brain tissue was achieved.

Conclusions:

• NIR-GECO1 is a functional NIR fluorescent GECI for Ca2+ imaging.
• Its performance is comparable to existing visible-wavelength GECIs.
• NIR-GECO1 facilitates advanced multicolor imaging and opens new possibilities in neuroscience and cell biology.