A Screen for Synaptic Growth Mutants Reveals Mechanisms That Stabilize Synaptic Strength

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Molecular Biology

Background:

• Synaptic structure undergoes dynamic changes (growth, pruning, remodeling) throughout life.
• These changes can destabilize neural information transfer, yet neural activity remains stable.
• Aberrant synaptic plasticity is linked to neurological disorders such as Fragile X syndrome and autism.

Purpose of the Study:

• To identify mechanisms stabilizing synaptic strength despite alterations in synaptic growth.
• To characterize novel mutants affecting synaptic growth at the Drosophila neuromuscular junction.
• To understand how synapses maintain physiological neurotransmission ranges.

Main Methods:

• Forward genetic screen of 300 Drosophila mutants.
• Analysis of synaptic growth at the neuromuscular junction.
• Electrophysiological recordings to measure synaptic strength.
• Genetic, anatomical, and electrophysiological analyses of identified mutants.

Main Results:

• Identified 12 mutants with significantly altered synaptic growth (reduction or enhancement).
• Synaptic strength remained largely unchanged in mutants, indicating homeostatic stabilization.
• Discovered three compensatory mechanisms: altered postsynaptic receptor abundance, presynaptic morphology changes, and active zone structure modifications.

Conclusions:

• Drosophila neuromuscular junction exhibits robust homeostatic mechanisms to stabilize synaptic strength.
• Compensatory changes in receptor abundance, presynaptic morphology, and active zone structure allow stable neurotransmission despite variable synaptic growth.
• These findings offer insights into maintaining stable neural function during development, experience, and disease.