Glia-to-glia serotonin signaling directs MMP-dependent infiltration for experience-dependent synapse pruning

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• Synapse connectivity is refined during critical periods through experience-dependent pruning by glial cells.
• Glial intercellular signaling, particularly serotonergic communication, is crucial for this precise synaptic elimination process.

Purpose of the Study:

• To investigate the role of glia-to-glia communication in experience-dependent synaptic pruning during critical periods.
• To identify the specific glial cell types and molecular mechanisms involved in serotonin-mediated synapse elimination.

Main Methods:

• Utilized Drosophila melanogaster as a model organism.
• Employed cell-targeted RNA interference (RNAi) for tryptophan hydroxylase (Trhn) and 5-HT2A receptor (5-HT2AR).
• Performed genetic rescue experiments and analyzed matrix metalloproteinase-1 (MMP-1) induction.

Main Results:

• Discovered essential glia-to-glia communication for experience-dependent synaptic pruning in Drosophila.
• Identified ensheathing glia and astrocyte-like glia (ALG) as key players, with 5-HT2AR signaling specifically in ALGs.
• Demonstrated that astrocytic 5-HT2AR signaling can restore critical period-like synapse pruning in adult brains.
• Showed that astrocytic MMP-1, induced by odorant experience, is required downstream of 5-HT2AR activation for pruning.

Conclusions:

• Glia-to-glia serotonergic 5-HT2AR signaling drives MMP-1-mediated synaptic pruning.
• This signaling pathway is necessary and sufficient for experience-dependent synapse elimination.
• Astrocytic 5-HT2AR signaling can reactivate critical period synaptic remodeling capabilities in mature adults.