title: The class 4 semaphorin Sema4D promotes the rapid assembly of GABAergic synapses in rodent hippocampus.
abstract: Proper circuit function in the mammalian nervous system depends on the precise assembly and development of excitatory and inhibitory synaptic connections between neurons. Through a loss-of-function genetic screen in cultured hippocampal neurons, we previously identified the class 4 Semaphorin Sema4D as being required for proper GABAergic synapse development. Here we demonstrate that Sema4D is sufficient to promote GABAergic synapse formation in rodent hippocampus and investigate the kinetics of this activity. We find that Sema4D treatment of rat hippocampal neurons increases the density of GABAergic synapses as detected by immunocytochemistry within 30 min, much more rapidly than has been previously described for a prosynaptogenic molecule, and show that this effect is dependent on the Sema4D receptor PlexinB1 using PlxnB1(-/-) mice. Live imaging studies reveal that Sema4D elicits a rapid enhancement (within 10 min) in the rate of addition of synaptic proteins. Therefore, we demonstrate that Sema4D, via PlexinB1, acts to initiate synapse formation by recruiting molecules to both the presynaptic and the postsynaptic terminals; these nascent synapses subsequently become fully functional by 2 h after Sema4D treatment. In addition, acute treatment of an organotypic hippocampal slice epilepsy model with Sema4D reveals that Sema4D rapidly and dramatically alters epileptiform activity, which is consistent with a Sema4D-mediated shift in the balance of excitation and inhibition within the circuit. These data demonstrate an ability to quickly assemble GABAergic synapses in response to an appropriate signal and suggest a potential area of exploration for the development of novel antiepileptic drugs.
authors.affiliation: Department of Biology, National Center for Behavioral Genomics, and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454, USA.
authors.forename: Marissa S
authors.initials: MS
authors.lastname: Kuzirian
authors.forename: Anna R
authors.initials: AR
authors.lastname: Moore
authors.forename: Emily K
authors.initials: EK
authors.lastname: Staudenmaier
authors.forename: Roland H
authors.initials: RH
authors.lastname: Friedel
authors.forename: Suzanne
authors.initials: S
authors.lastname: Paradis
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D015703:Antigens, CD / Q000737:chemistry / Q000494:pharmacology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D004622:Embryo, Mammalian; D005260:Female; D059330:GABAergic Neurons / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005968:Glutamate Decarboxylase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects; D006624:Hippocampus / Q000166:cytology*; D007141:Immunoglobulin Fc Fragments / Q000494:pharmacology; D008297:Male; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism; D039961:Semaphorins / Q000737:chemistry / Q000494:pharmacology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013569:Synapses / Q000502:physiology*; D055366:Synaptic Potentials / Q000187:drug effects / Q000235:genetics; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D015703:Antigens, CD; C093224:CD100 antigen; D007141:Immunoglobulin Fc Fragments; D009419:Nerve Tissue Proteins; D011963:Receptors, GABA-A; D039961:Semaphorins; D026941:Sodium Channel Blockers; D049452:Green Fluorescent Proteins; D013779:Tetrodotoxin; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2