Stereotyped axon pruning via plexin signaling is associated with synaptic complex elimination in the hippocampus.
Plexin signaling is required for stereotyped pruning of long axon collaterals in the vertebrate CNS; however, a cellular basis for plexins on stereotyped pruning has not been determined. Using quantitative electron microscopy and immunocytochemistry, we found that infrapyramidal mossy fiber axon collaterals form transient synaptic complexes with basal dendrites of CA3 pyramidal cells in the early postnatal mouse hippocampus. At later postnatal ages, these synaptic complexes stop maturing and are removed before stereotyped pruning by a mechanism that does not involve axon degeneration and glial cell engulfment. In knock-out mice that lack plexin-A3 signaling, the synaptic complexes continue to mature, and, as a result, the collaterals are not pruned. Thus, our results suggest that intact plexin-A3 signaling contributes to synaptic complex elimination, which is associated with stereotyped axon pruning.
Liu
Xiao-Bo
XB
Center for Neuroscience, University of California, Davis, California 95616, USA.
Low
Lawrence K
LK
Jones
Edward G
EG
Cheng
Hwai-Jong
HJ
D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D064026:Calbindins; D015815:Cell Adhesion Molecules / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D021621:Imaging, Three-Dimensional / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D051379:Mice; D018345:Mice, Knockout; D016253:Microscopy, Immunoelectron / Q000379:methods; D019599:Mossy Fibers, Hippocampal / Q000254:growth & development / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D039943:Neuropilin-2 / Q000172:deficiency / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000172:deficiency / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism
D064026:Calbindins; D015815:Cell Adhesion Molecules; D009419:Nerve Tissue Proteins; D039943:Neuropilin-2; C492112:Plxna3 protein, mouse; D011956:Receptors, Cell Surface; D064030:S100 Calcium Binding Protein G; C493477:Slc17a6 protein, mouse; C493465:Slc17a7 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; C091529:plexin