--- res: bibo_abstract: - Cortical networks are characterized by sparse connectivity, with synapses found at only a subset of axo-dendritic contacts. Yet within these networks, neurons can exhibit high connection probabilities, suggesting that cell-intrinsic factors, not proximity, determine connectivity. Here, we identify ephrin-B3 (eB3) as a factor that determines synapse density by mediating a cell-cell competition that requires ephrin-B-EphB signaling. In a microisland culture system designed to isolate cell-cell competition, we find that eB3 determines winning and losing neurons in a contest for synapses. In a Mosaic Analysis with Double Markers (MADM) genetic mouse model system in vivo the relative levels of eB3 control spine density in layer 5 and 6 neurons. MADM cortical neurons in vitro reveal that eB3 controls synapse density independently of action potential-driven activity. Our findings illustrate a new class of competitive mechanism mediated by trans-synaptic organizing proteins which control the number of synapses neurons receive relative to neighboring neurons.@eng bibo_authorlist: - foaf_Person: foaf_givenName: Nathan T. foaf_name: Henderson, Nathan T. foaf_surname: Henderson - foaf_Person: foaf_givenName: Sylvain J. foaf_name: Le Marchand, Sylvain J. foaf_surname: Le Marchand - foaf_Person: foaf_givenName: Martin foaf_name: Hruska, Martin foaf_surname: Hruska - foaf_Person: foaf_givenName: Simon foaf_name: Hippenmeyer, Simon foaf_surname: Hippenmeyer foaf_workInfoHomepage: http://www.librecat.org/personId=37B36620-F248-11E8-B48F-1D18A9856A87 orcid: 0000-0003-2279-1061 - foaf_Person: foaf_givenName: Liqun foaf_name: Luo, Liqun foaf_surname: Luo - foaf_Person: foaf_givenName: Matthew B. foaf_name: Dalva, Matthew B. foaf_surname: Dalva bibo_doi: 10.7554/eLife.41563 bibo_volume: 8 dct_date: 2019^xs_gYear dct_identifier: - UT:000459380600001 dct_language: eng dct_publisher: eLife Sciences Publications@ dct_title: Ephrin-B3 controls excitatory synapse density through cell-cell competition for EphBs@ fabio_hasPubmedId: '30789343' ...