Polycomb group genes are required for neuronal pruning in Drosophila

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Neuronal wiring requires selective pruning of neurites.
• Drosophila sensory (ddaC) and mushroom body (MB) γ neurons undergo pruning during metamorphosis, initiated by ecdysone.
• The precise downstream mechanisms of ecdysone signaling in neuronal pruning are not fully understood.

Purpose of the Study:

• To investigate the role of Polycomb group (PcG) proteins in regulating neuronal pruning in Drosophila.
• To elucidate the involvement of specific PcG complexes (PRC1 and PRC2) and Hox genes in ecdysone-induced neuronal pruning.

Main Methods:

• Utilized Drosophila melanogaster as a model organism.
• Employed genetic manipulation techniques to deplete or overexpress specific genes, including PcG components (Scm, PRC1, PRC2, Ph) and Hox genes (Abd-B, Ubx, AbdA).
• Assessed neuronal pruning defects and analyzed gene expression patterns (Mical, Hox genes).

Main Results:

• Scm, a PcG protein, is essential for ddaC dendrite pruning.
• PRC1 and PRC2 complexes play significant roles in dendrite pruning.
• Depletion of PRC1 leads to increased expression of Abdominal B (Abd-B) and Sex combs reduced, while PRC2 loss causes mild upregulation of Ultrabithorax and Abdominal A.
• Overexpression of Abd-B results in severe pruning defects.
• Knockdown of Polyhomeotic (Ph) or Abd-B overexpression downregulates Mical, inhibiting ecdysone signaling.
• Ph is also required for MB γ axon pruning and Abd-B silencing, indicating conserved PRC1 function.

Conclusions:

• PcG and Hox genes are critical regulators of ecdysone signaling and neuronal pruning in Drosophila.
• PRC1 plays a non-canonical, PRC2-independent role in Hox gene silencing during neuronal pruning.
• These findings provide new insights into the molecular mechanisms governing nervous system development and wiring.