AAV-compatible optogenetic tools for activating endogenous calcium channels in vivo

Area of Science:

• Neuroscience
• Molecular Biology
• Calcium Signaling

Background:

• Calcium ions (Ca²⁺) are crucial for numerous brain functions, including cognition and memory.
• Ca²⁺-dependent processes like synaptic plasticity and neurotransmitter release are vital for neural activity.
• Previous tool 'monster OptoSTIM1' (monSTIM1) allowed light-controlled Ca²⁺ signaling but was too large for AAV delivery.

Purpose of the Study:

• To engineer smaller, AAV-compatible variants of monSTIM1 for precise control of intracellular Ca²⁺ signaling.
• To establish AAV-based systems for expressing these variants in mouse neurons and glial cells.
• To investigate the utility of these variants in modulating Ca²⁺-mediated cellular activity in the brain.

Main Methods:

• Development of reduced-size monSTIM1 variants.
• Construction of adeno-associated virus (AAV) vectors for expressing monSTIM1 variants.
• In vivo expression in mouse hippocampal CA1 neurons and astrocytes, followed by light-induced activation.

Main Results:

• AAV-mediated expression of monSTIM1 variants successfully targeted neurons and glial cells.
• Non-invasive blue light illumination significantly increased cFos expression in both cell types.
• Demonstrated effective spatiotemporal control over Ca²⁺ signaling in the mouse brain.

Conclusions:

• Engineered monSTIM1 variants overcome AAV packaging limitations, enabling broader application.
• This toolkit provides a powerful method for studying the roles of Ca²⁺ signaling in brain function.
• Potential therapeutic applications for brain disorders linked to abnormal Ca²⁺ signaling.