Astrocytes play a key role in Drosophila mushroom body axon pruning.
Axon pruning is an evolutionarily conserved strategy used to remodel neuronal connections during development. The Drosophila mushroom body (MB) undergoes neuronal remodeling in a highly stereotypical and tightly regulated manner, however many open questions remain. Although it has been previously shown that glia instruct pruning by secreting a TGF-β ligand, myoglianin, which primes MB neurons for fragmentation and also later engulf the axonal debris once fragmentation has been completed, which glia subtypes participate in these processes as well as the molecular details are unknown. Here we show that, unexpectedly, astrocytes are the major glial subtype that is responsible for the clearance of MB axon debris following fragmentation, even though they represent only a minority of glia in the MB area during remodeling. Furthermore, we show that astrocytes both promote fragmentation of MB axons as well as clear axonal debris and that this process is mediated by ecdysone signaling in the astrocytes themselves. In addition, we found that blocking the expression of the cell engulfment receptor Draper in astrocytes only affects axonal debris clearance. Thereby we uncoupled the function of astrocytes in promoting axon fragmentation to that of clearing axonal debris after fragmentation has been completed. Our study finds a novel role for astrocytes in the MB and suggests two separate pathways in which they affect developmental axon pruning.
Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel.
Yaniv
Y
Hakim
Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel.
Shiri P
SP
Yaniv
Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel.
Oren
O
Schuldiner
D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D001369:Axons / Q000378:metabolism*; D002452:Cell Count; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000378:metabolism*; D004705:Endocytosis; D055785:Gene Knockdown Techniques; D008565:Membrane Proteins / Q000378:metabolism; D024521:Mushroom Bodies / Q000166:cytology* / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism
D029721:Drosophila Proteins; D008565:Membrane Proteins; D011987:Receptors, Steroid; C495322:drpr protein, Drosophila; C055469:ecdysone receptor