Cortical Presynaptic Boutons Progressively Engulf Spinules as They Mature

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• Synaptic spinules are poorly understood finger-like projections from postsynaptic spines.
• Their role in synaptic development, function, and communication remains elusive.
• Potential roles include extrasynaptic communication and enhancing synaptic stability.

Purpose of the Study:

• To investigate the prevalence of spinules in excitatory presynaptic boutons during development.
• To determine the origins of spinules in spinule-bearing boutons (SBBs).
• To explore the relationship between spinule prevalence and cortical development.

Main Methods:

• Utilized 2D and 3D electron microscopy.
• Examined the primary visual cortex (V1) of ferrets at key developmental stages.
• Quantified spinule prevalence in excitatory presynaptic boutons.

Main Results:

• Spinule-bearing boutons (SBBs) prevalence increases with postnatal development in ferret V1.
• Approximately 25% of excitatory boutons in late adolescent ferret V1 contain spinules.
• Most spinules in mature SBBs originate from postsynaptic spines and adjacent boutons/axons.

Conclusions:

• Synaptic spinules are integral to the developing and mature ferret visual cortex.
• Spinules likely contribute to enhanced synaptic stability.
• Spinules may facilitate axo-axonal communication in the sensory cortex.