Genetically encoded green fluorescent Ca2+ indicators with improved detectability for neuronal Ca2+ signals

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Genetically encoded calcium indicators (GECIs) are crucial for understanding neuronal network function.
• Existing GECIs have limitations in detecting subtle and fast neuronal activities.

Purpose of the Study:

• To develop and characterize novel GECIs with enhanced neuronal calcium signal detectability.
• To evaluate the performance of new GECIs in imaging neuronal activity and dendritic spine calcium transients.

Main Methods:

• Development of G-CaMP6 and G-CaMP8, novel GECIs with improved signal-to-noise ratio and kinetics.
• Electrophysiological recordings and calcium imaging in cultured hippocampal and acute cortical slices.
• Expression of G-CaMP6-actin fusion protein in hippocampal CA3 pyramidal neurons for dendritic spine imaging.

Main Results:

• G-CaMP6 and G-CaMP8 demonstrated superior performance in detecting individual neuronal spikes compared to existing GECIs.
• G-CaMP6 exhibited higher sensitivity and brighter baseline fluorescence, making it suitable for dendritic spine imaging.
• Sub-threshold stimulation elicited localized Ca(2+) responses in dendritic spines, while supra-threshold stimulation induced widespread spine activity.

Conclusions:

• G-CaMP6 and G-CaMP8 represent significant advancements in GECI technology for neuroscience research.
• These novel indicators facilitate high-resolution imaging of neuronal activity at both the single-neuron and dendritic spine levels.
• The findings provide new tools for investigating the relationship between neuronal activity and synaptic plasticity.