title: Expression of Pannexin1 in the outer plexiform layer of the mouse retina and physiological impact of its knockout.
abstract: Pannexin1 (Panx1) belongs to a class of vertebrate proteins that exhibits sequence homology to innexins, the invertebrate gap junction proteins, and which also shares topological similarities with vertebrate gap junction proteins, the connexins. Unlike gap junctional channels, Panx1 forms single-membrane channels, whose functional role in neuronal circuits is still unsettled. We therefore investigated the subcellular distribution of Panx1 in the mouse retina of wildtype and Panx1-null mice by reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and electron microscopy. Use of Panx1-deficient mice served as a model to assess the physiological role of Panx1 by electroretinographic recordings and also to ensure the specificity of the anti-Panx1 antibody labeling. Expression of Panx1 was found in type 3a OFF bipolar cells and in dendrites and axonal processes of horizontal cells. Panx1 was also found in horizontal cell dendrites representing the lateral elements of the triad synapse at cone and rod terminals. In vivo electroretinography of Panx1 knockout mice indicated an increased a- and b-wave compared to Panx1 wildtype mice under scotopic conditions. The effect on the b-wave was confirmed by in vitro electroretinograms from the inner retina. These results suggest that Panx1 channels serve as sinks for extracellular current flow making them possible candidates for the mediation of feedback from horizontal cells to photoreceptors.
authors.affiliation: Department of Neurobiology, University of Oldenburg, D-26111 Oldenburg, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Kranz
authors.forename: Birthe
authors.initials: B
authors.lastname: Dorgau
authors.forename: Mark
authors.initials: M
authors.lastname: Pottek
authors.forename: Regina
authors.initials: R
authors.lastname: Herrling
authors.forename: Konrad
authors.initials: K
authors.lastname: Schultz
authors.forename: Petra
authors.initials: P
authors.lastname: Bolte
authors.forename: Hannah
authors.initials: H
authors.lastname: Monyer
authors.forename: Silvia
authors.initials: S
authors.lastname: Penuela
authors.forename: Dale W
authors.initials: DW
authors.lastname: Laird
authors.forename: Karin
authors.initials: K
authors.lastname: Dedek
authors.forename: Reto
authors.initials: R
authors.lastname: Weiler
authors.forename: Ulrike
authors.initials: U
authors.lastname: Janssen-Bienhold
mesh_terms: D000818:Animals; D017630:Connexins / Q000172:deficiency* / Q000235:genetics; D004596:Electroretinography; D005074:Evoked Potentials, Visual / Q000235:genetics; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D006026:Glycoside Hydrolases / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000145:classification / Q000502:physiology* / Q000648:ultrastructure; D012160:Retina / Q000033:anatomy & histology*; D051245:Retinal Bipolar Cells / Q000378:metabolism; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D014795:Visual Pathways / Q000502:physiology*
chemical_list: D017630:Connexins; D005136:Eye Proteins; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; D014446:Tyrosine 3-Monooxygenase; D006026:Glycoside Hydrolases; C089138:beta-galactanase