title: Innexin gap junctions in nerve cells coordinate spontaneous contractile behavior in Hydra polyps.
abstract: Nerve cells and spontaneous coordinated behavior first appeared near the base of animal evolution in the common ancestor of cnidarians and bilaterians. Experiments on the cnidarian Hydra have demonstrated that nerve cells are essential for this behavior, although nerve cells in Hydra are organized in a diffuse network and do not form ganglia. Here we show that the gap junction protein innexin-2 is expressed in a small group of nerve cells in the lower body column of Hydra and that an anti-innexin-2 antibody binds to gap junctions in the same region. Treatment of live animals with innexin-2 antibody eliminates gap junction staining and reduces spontaneous body column contractions. We conclude that a small subset of nerve cells, connected by gap junctions and capable of synchronous firing, act as a pacemaker to coordinate the contraction of the body column in the absence of ganglia.
authors.affiliation: 1] Hamamatsu University School of Medicine, Department of Biology, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan [2].
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Takaku
authors.affiliation: 1] Center for Information Biology-DNA Data Bank of Japan, National Institute of Genetics, Mishima 411-8540, Japan [2].
authors.forename: Jung Shan
authors.initials: JS
authors.lastname: Hwang
authors.affiliation: 1] Helmholtz Zentrum München - German Research Center of Environmental Health, Institute of Molecular Toxicology and Pharmacology, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany [2].
authors.forename: Alexander
authors.initials: A
authors.lastname: Wolf
authors.affiliation: Department Biologie II, Ludwig Maximilians University, Munich 80539, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Böttger
authors.affiliation: Department of Developmental Genetics, National Institute of Genetics, Mishima 411-8540, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimizu
authors.affiliation: Department Biologie II, Ludwig Maximilians University, Munich 80539, Germany.
authors.forename: Charles N
authors.initials: CN
authors.lastname: David
authors.affiliation: Biological and Environmental Science and Engineering Division and Computational Bioscience Research Center, KAUST, Thuwal 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Takashi
authors.initials: T
authors.lastname: Gojobori
mesh_terms: D000818:Animals; D017630:Connexins / Q000378:metabolism / Q000502:physiology*; D017629:Gap Junctions / Q000502:physiology*; D006829:Hydra / Q000502:physiology*; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D013569:Synapses / Q000378:metabolism / Q000502:physiology
chemical_list: D017630:Connexins