title: Knockdown of cone-specific kinase GRK7 in larval zebrafish leads to impaired cone response recovery and delayed dark adaptation.
abstract: Phosphorylation of rhodopsin by rhodopsin kinase GRK1 is an important desensitization mechanism in scotopic vision. For cone vision GRK1 is not essential. However, cone opsin is phosphorylated following light stimulation. In cone-dominant animals as well as in humans, but not in rodents, GRK7, a cone-specific homolog of GRK1, has been identified in cone outer segments. To investigate the function of GRK7 in vivo, we cloned two orthologs of grk7 in zebrafish and knocked down gene expression of grk7a in zebrafish larvae by morpholino antisense nucleotides. Photoresponse recovery in Grk7a-deficient larvae was delayed in electroretinographic measurements, and temporal contrast sensitivity was reduced, particularly under bright-light conditions. These results show that function of a cone-specific kinase is essential for cone vision in the zebrafish retina and argue that pigment bleaching and spontaneous decay alone are not sufficient for light adaptation and rapid cone response inactivation.
authors.affiliation: Brain Research Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; Institute for Molecular Systems Biology, Swiss Federal Institute of Technology (ETH), CH-8093 Zurich, Switzerland.
authors.forename: Oliver
authors.initials: O
authors.lastname: Rinner
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Makhankov
authors.forename: Oliver
authors.initials: O
authors.lastname: Biehlmaier
authors.forename: Stephan C F
authors.initials: SC
authors.lastname: Neuhauss
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019393:Arrestin / Q000378:metabolism; D015153:Blotting, Western; D003001:Cloning, Molecular / Q000379:methods; D015350:Contrast Sensitivity / Q000235:genetics / Q000502:physiology; D003623:Dark Adaptation / Q000235:genetics*; D004596:Electroretinography / Q000379:methods; D005071:Evoked Potentials / Q000235:genetics / Q000528:radiation effects; D005123:Eye / Q000378:metabolism / Q000473:pathology; D054768:G-Protein-Coupled Receptor Kinases; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D007814:Larva / Q000235:genetics* / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D010870:Pineal Gland / Q000196:embryology / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000502:physiology*; D011601:Psychophysics; D017949:Retinal Cone Photoreceptor Cells / Q000196:embryology / Q000378:metabolism / Q000502:physiology*; D012243:Rhodopsin / Q000378:metabolism; D013997:Time Factors; D015027:Zebrafish / Q000235:genetics / Q000502:physiology*; D029961:Zebrafish Proteins
chemical_list: D019393:Arrestin; D029961:Zebrafish Proteins; D012243:Rhodopsin; D017346:Protein Serine-Threonine Kinases; C111571:GRK7 protein, human; C504360:grk7b protein, zebrafish; D054768:G-Protein-Coupled Receptor Kinases