Glia control experience-dependent plasticity in an olfactory critical period

Area of Science:

• Neuroscience
• Developmental Biology
• Olfactory System

Background:

• Early sensory experiences shape neural circuits with lasting effects.
• The molecular mechanisms of experience-dependent plasticity during critical periods are not fully understood.
• Drosophila antennal lobe olfactory sensory neuron (OSN)-projection neuron (PN) synapses undergo structural plasticity.

Purpose of the Study:

• To investigate the role of glia in experience-dependent plasticity of the Drosophila olfactory system during a critical period.
• To define the critical period for olfactory circuit plasticity in response to odor exposure.
• To elucidate the molecular mechanisms underlying experience-driven synaptic pruning.

Main Methods:

• Ethyl butyrate (EB) exposure during the first two days post-eclosion in Drosophila.
• Quantification of glomerular volume, presynapse number, and postsynaptic activity.
• Analysis of the role of the engulfment receptor Draper in glia-mediated pruning.
• Assessment of long-term structural and functional consequences of early-life odor exposure.

Main Results:

• Early EB exposure induced significant reductions in VM7 glomerular volume, presynapse number, and postsynaptic activity.
• These structural and functional changes persisted long-term, affecting OSN-PN synapse number and PN spontaneous activity.
• Ensheathing glia upregulated Draper, invaded the VM7 glomerulus, and phagocytosed OSN presynaptic terminals.
• Loss of Draper function abolished the effects of critical period odor exposure, indicating glia-mediated synaptic pruning.

Conclusions:

• A critical period exists for structural and functional plasticity in the Drosophila olfactory circuit.
• Phagocytic glia, utilizing the Draper receptor, actively prune olfactory synapses during this critical period.
• Drosophila olfactory circuitry provides a model for understanding glia's role in experience-dependent critical period plasticity.