title: Pathway-specific genetic attenuation of glutamate release alters select features of competition-based visual circuit refinement.
abstract: A hallmark of mammalian neural circuit development is the refinement of initially imprecise connections by competitive activity-dependent processes. In the developing visual system retinal ganglion cell (RGC) axons from the two eyes undergo activity-dependent competition for territory in the dorsal lateral geniculate nucleus (dLGN). The direct contributions of synaptic transmission to this process, however, remain unclear. We used a genetic approach to reduce glutamate release selectively from ipsilateral-projecting RGCs and found that their release-deficient axons failed to exclude competing axons from the ipsilateral eye territory in the dLGN. Nevertheless, the release-deficient axons consolidated and maintained their normal amount of dLGN territory, even in the face of fully active competing axons. These results show that during visual circuit refinement glutamatergic transmission plays a direct role in excluding competing axons from inappropriate target regions, but they argue that consolidation and maintenance of axonal territory are largely insensitive to alterations in synaptic activity levels.
authors.affiliation: Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: Selina M
authors.initials: SM
authors.lastname: Koch
authors.forename: Cassandra G
authors.initials: CG
authors.lastname: Dela Cruz
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hnasko
authors.forename: Robert H
authors.initials: RH
authors.lastname: Edwards
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Huberman
authors.forename: Erik M
authors.initials: EM
authors.lastname: Ullian
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D000831:Animals, Newborn; D001703:Biophysics / Q000379:methods; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D007839:Functional Laterality; D005829:Geniculate Bodies / Q000502:physiology; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D051379:Mice; D008817:Mice, Mutant Strains; D012160:Retina / Q000166:cytology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D018709:Statistics, Nonparametric; D009435:Synaptic Transmission / Q000235:genetics; D050599:Vesicular Glutamate Transport Protein 2 / Q000172:deficiency / Q000235:genetics; D014795:Visual Pathways / Q000033:anatomy & histology / Q000254:growth & development*
chemical_list: C493477:Slc17a6 protein, mouse; D050599:Vesicular Glutamate Transport Protein 2; D049452:Green Fluorescent Proteins; D018698:Glutamic Acid; D002772:Cholera Toxin