451. GluD2- and Cbln1-mediated Competitive Synaptogenesis Shapes the Dendritic Arbors of Cerebellar Purkinje Cells
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David J. Luginbuhl, S. Andrew Shuster, Ximena Contreras, Mark J. Wagner, Thomas Rülicke, Liqun Luo, Yukari H. Takeo, Surya Ganguli, Linnie Jiang, Simon Hippenmeyer, and Miley Hu
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0303 health sciences ,050208 finance ,05 social sciences ,Purkinje cell ,Synaptogenesis ,GLUD2 ,Biology ,Phenotype ,Dendrite morphogenesis ,03 medical and health sciences ,Dendrite (crystal) ,0302 clinical medicine ,medicine.anatomical_structure ,Neurotransmitter receptor ,Cerebellar cortex ,0502 economics and business ,medicine ,050207 economics ,Neuroscience ,030217 neurology & neurosurgery ,030304 developmental biology - Abstract
SUMMARYThe synaptotrophic hypothesis posits that synapse formation stabilizes dendritic branches, yet this hypothesis has not been causally tested in vivo in the mammalian brain. Presynaptic ligand cerebellin-1 (Cbln1) and postsynaptic receptor GluD2 mediate synaptogenesis between granule cells and Purkinje cells in the molecular layer of the cerebellar cortex. Here we show that sparse but not global knockout of GluD2 causes under-elaboration of Purkinje cell dendrites in the deep molecular layer and overelaboration in the superficial molecular layer. Developmental, overexpression, structure-function, and genetic epistasis analyses indicate that dendrite morphogenesis defects result from competitive synaptogenesis in a Cbln1/GluD2-dependent manner. A generative model of dendritic growth based on competitive synaptogenesis largely recapitulates GluD2 sparse and global knockout phenotypes. Our results support the synaptotrophic hypothesis at initial stages of dendrite development, suggest a second mode in which cumulative synapse formation inhibits further dendrite growth, and highlight the importance of competition in dendrite morphogenesis.
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