Rapid formation and remodeling of postsynaptic densities in developing dendrites

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• The postsynaptic density (PSD) is a critical protein complex at excitatory synapses, crucial for synaptic function and plasticity.
• Understanding the dynamic nature of PSDs is essential for comprehending synapse development and circuit formation in the central nervous system (CNS).

Purpose of the Study:

• To investigate the dynamic formation and remodeling processes of postsynaptic densities (PSDs) in live developing hippocampal tissue.
• To characterize the structural plasticity and turnover rates of PSDs within dendritic shafts, spines, and spine precursors.

Main Methods:

• Utilized time-lapse imaging of live developing hippocampal tissue slices.
• Expressed GFP-tagged PSD95, a key PSD protein, in neurons to visualize PSD dynamics in real-time.
• Quantified the appearance, disappearance, growth, shrinkage, and movement of PSDs.

Main Results:

• Up to 40% of PSDs in developing dendrites exhibit significant structural dynamics.
• PSDs were observed to rapidly appear or disappear within minutes (<15 min).
• PSDs demonstrated dynamic changes in size (growth/shrinkage) and location (movement) within dendritic compartments.
• New spines with PSDs formed via conversion of filopodia-like precursors or direct extension of existing spines/precursors.

Conclusions:

• Postsynaptic densities are highly dynamic structures capable of rapid alteration.
• This dynamic remodeling of PSDs facilitates the rapid formation and modification of synaptic connections during CNS development.
• The observed plasticity of PSDs plays a fundamental role in establishing neural circuits.