title: Activin increases the number of synaptic contacts and the length of dendritic spine necks by modulating spinal actin dynamics.
abstract: Long-lasting modifications in synaptic transmission depend on de novo gene expression in neurons. The expression of activin, a member of the transforming growth factor beta (TGF-beta) superfamily, is upregulated during hippocampal long-term potentiation (LTP). Here, we show that activin increased the average number of presynaptic contacts on dendritic spines by increasing the population of spines that were contacted by multiple presynaptic terminals in cultured neurons. Activin also induced spine lengthening, primarily by elongating the neck, resulting in longer mushroom-shaped spines. The number of spines and spine head size were not significantly affected by activin treatment. The effects of activin on spinal filamentous actin (F-actin) morphology were independent of protein and RNA synthesis. Inhibition of cytoskeletal actin dynamics or of the mitogen-activated protein (MAP) kinase pathway blocked not only the activin-induced increase in the number of terminals contacting a spine but also the activin-induced lengthening of spines. These results strongly suggest that activin increases the number of synaptic contacts by modulating actin dynamics in spines, a process that might contribute to the establishment of late-phase LTP.
authors.affiliation: Mitsubishi Kagaku Institute of Life Sciences, MITILS, 11 Minamiooya, Machida, Tokyo 194-8511, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Shoji-Kasai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ageta
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Tsuchida
authors.forename: Hiromu
authors.initials: H
authors.lastname: Sugino
authors.forename: Kaoru
authors.initials: K
authors.lastname: Inokuchi
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D028341:Activins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D006624:Hippocampus / Q000166:cytology; D017774:Long-Term Potentiation / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D051381:Rats; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D000199:Actins; D028341:Activins; D020928:Mitogen-Activated Protein Kinases