title: Specific connectivity between photoreceptors and horizontal cells in the zebrafish retina.
abstract: The functional and morphological connectivity between various horizontal cell (HC) types (H1, H2, H3, and H4) and photoreceptors was studied in zebrafish retina. Since HCs are strongly coupled by gap junctions and feedback from HCs to photoreceptors depends strongly on connexin (Cx) hemichannels, we characterized the various HC Cxs (Cx52.6, Cx52.7, Cx52.9, and Cx55.5) in Xenopus oocytes. All Cxs formed hemichannels that were conducting at physiological membrane potentials. The Cx hemichannels differed in kinetic properties and voltage dependence, allowing for specific tuning of the coupling of HCs and the feedback signal from HCs to cones. The morphological connectivity between HC layers and cones was determined next. We used zebrafish expressing green fluorescent protein under the control of Cx promoters. We found that all HCs showed Cx55.5 promoter activity. Cx52.7 promoter activity was exclusively present in H4 cells, while Cx52.9 promoter activity occurred only in H1 cells. Cx52.6 promoter activity was present in H4 cells and in the ventral quadrant of the retina also in H1 cells. Finally, we determined the spectral sensitivities of the HC layers. Three response types were found. Monophasic responses were generated by HCs that contacted all cones (H1 cells), biphasic responses were generated by HCs that contacted M, S, and UV cones (H2 cells), and triphasic responses were generated by HCs that contacted either S and UV cones (H3 cells) or rods and UV cones (H4 cells). Electron microscopy confirms that H4 cells innervate cones. This indicates that rod-driven HCs process spectral information during photopic and luminance information during scotopic conditions.
authors.affiliation: Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and.
authors.forename: Lauw J
authors.initials: LJ
authors.lastname: Klaassen
authors.affiliation: Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and.
authors.forename: Wim
authors.initials: W
authors.lastname: de Graaff
authors.affiliation: Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and.
authors.forename: Jorrit B
authors.initials: JB
authors.lastname: van Asselt
authors.affiliation: Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and.
authors.forename: Jan
authors.initials: J
authors.lastname: Klooster
authors.affiliation: Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands; and m.kamermans@nin.knaw.nl.|Department of Genome Analysis, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Maarten
authors.initials: M
authors.lastname: Kamermans
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D001703:Biophysics; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D004558:Electric Stimulation; D025461:Feedback, Physiological / Q000502:physiology; D017629:Gap Junctions / Q000502:physiology* / Q000648:ultrastructure; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology*; D008845:Microinjections; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009865:Oocytes; D018408:Patch-Clamp Techniques; D020419:Photoreceptor Cells, Vertebrate / Q000145:classification / Q000502:physiology* / Q000648:ultrastructure; D012160:Retina / Q000166:cytology*; D051248:Retinal Horizontal Cells / Q000145:classification / Q000502:physiology* / Q000648:ultrastructure; D014161:Transduction, Genetic; D014982:Xenopus laevis; D015027:Zebrafish
chemical_list: D017630:Connexins; C070614:neurobiotin; D049452:Green Fluorescent Proteins; D001710:Biotin
keywords: connexins; horizontal cell; photoreceptors; retina; zebrafish