title: EML1 (CNG-modulin) controls light sensitivity in darkness and under continuous illumination in zebrafish retinal cone photoreceptors.
abstract: The ligand sensitivity of cGMP-gated (CNG) ion channels in cone photoreceptors is modulated by CNG-modulin, a Ca(2+)-binding protein. We investigated the functional role of CNG-modulin in phototransduction in vivo in morpholino-mediated gene knockdown zebrafish. Through comparative genomic analysis, we identified the orthologue gene of CNG-modulin in zebrafish, eml1, an ancient gene present in the genome of all vertebrates sequenced to date. We compare the photoresponses of wild-type cones with those of cones that do not express the EML1 protein. In the absence of EML1, dark-adapted cones are ∼5.3-fold more light sensitive than wild-type cones. Previous qualitative studies in several nonmammalian species have shown that immediately after the onset of continuous illumination, cones are less light sensitive than in darkness, but sensitivity then recovers over the following 15-20 s. We characterize light sensitivity recovery in continuously illuminated wild-type zebrafish cones and demonstrate that sensitivity recovery does not occur in the absence of EML1.
authors.affiliation: Departments of Ophthalmology and Physiology, School of Medicine, University of California, San Francisco, San Francisco, California 94143, Albert Eye Research Institute, Duke University Medical Center, Durham, North Carolina 27710, and Department of Biology, University of Oregon, Eugene, Oregon 97403.
authors.forename: Juan I
authors.initials: JI
authors.lastname: Korenbrot
authors.forename: Milap
authors.initials: M
authors.lastname: Mehta
authors.forename: Nomingerel
authors.initials: N
authors.lastname: Tserentsoodol
authors.forename: John H
authors.initials: JH
authors.lastname: Postlethwait
authors.forename: Tatiana I
authors.initials: TI
authors.lastname: Rebrik
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D003624:Darkness; D004596:Electroretinography; D008027:Light; D008029:Lighting; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D010775:Photic Stimulation; D020795:Photophobia / Q000235:genetics / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D015027:Zebrafish
chemical_list: D008869:Microtubule-Associated Proteins