Calsequestrin Deletion Facilitates Hippocampal Synaptic Plasticity and Spatial Learning in Post-Natal Development

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Endoplasmic reticulum (ER)-mediated Ca2+ signals are crucial for synaptic plasticity and spatial memory.
• Inositol 1,4,5-trisphosphate receptors (InsP3Rs) and ryanodine receptors (RyRs) mediate Ca2+ release from the ER.
• Calsequestrin (CASQ) and calreticulin (CR) are key Ca2+ storage proteins in the ER, with CASQ's role in hippocampal neurons being understudied.

Purpose of the Study:

• To investigate the role of CASQ in hippocampal CA1 neuron electrophysiology, synaptic plasticity, and spatial learning.
• To analyze Ca2+ handling in CA1 pyramidal cells of CASQ-deficient mice.

Main Methods:

• Utilized double CASQ-null (dCASQ-null) mice lacking both CASQ type-1 and type-2 isoforms.
• Performed electrophysiological recordings in the hippocampal CA1 field.
• Assessed spatial learning using the Morris Water Maze task.
• Analyzed Ca2+ handling in CA1 pyramidal neurons.

Main Results:

• Ablation of CASQ increased CA1 neuron excitability and enhanced long-term potentiation (LTP) maintenance.
• (d)CASQ-null mice demonstrated superior performance in the Morris Water Maze task, learning faster.
• CASQ deletion led to a reduced Ca2+ transient amplitude in CA1 pyramidal neurons, correlating with decreased afterhyperpolarization and improved LTP.

Conclusions:

• CASQ deletion impacts activity-dependent ER Ca2+ release.
• The absence of CASQ facilitates synaptic plasticity and spatial learning in the hippocampus.
• Findings suggest CASQ as a potential target for modulating cognitive functions related to spatial memory.