title: Melanosomes in pigmented epithelia maintain eye lens transparency during zebrafish embryonic development.
abstract: Altered levels of trace elements are associated with increased oxidative stress that is eventually responsible for pathologic conditions. Oxidative stress has been proposed to be involved in eye diseases, including cataract formation. We visualized the distribution of metals and other trace elements in the eye of zebrafish embryos by micro X-ray fluorescence (μ-XRF) imaging. Many elements showed highest accumulation in the retinal pigment epithelium (RPE) of the zebrafish embryo. Knockdown of the zebrafish brown locus homologues tyrp1a/b eliminated accumulation of these elements in the RPE, indicating that they are bound by mature melanosomes. Furthermore, albino (slc45a2) mutants, which completely lack melanosomes, developed abnormal lens reflections similar to the congenital cataract caused by mutation of the myosin chaperon Unc45b, and an in situ spin trapping assay revealed increased oxidative stress in the lens of albino mutants. Finally transplanting a wildtype lens into an albino mutant background resulted in cataract formation. These data suggest that melanosomes in pigment epithelial cells protect the lens from oxidative stress during embryonic development, likely by buffering trace elements.
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Masanari
authors.initials: M
authors.lastname: Takamiya
authors.affiliation: Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany.
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.affiliation: European Synchrotron Radiation Facility, 38043 Grenoble, France.|University of Helsinki, Department of Physics, 00560 Helsinki, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Suhonen
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Victor
authors.initials: V
authors.lastname: Gourain
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.|Department of Environmental Pollution and Health, State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Yang
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Nga Yu
authors.initials: NY
authors.lastname: Ho
authors.affiliation: Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany.|European Synchrotron Radiation Facility, 38043 Grenoble, France.
authors.forename: Lukas
authors.initials: L
authors.lastname: Helfen
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Schröck
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Christelle
authors.initials: C
authors.lastname: Etard
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Grabher
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Sepand
authors.initials: S
authors.lastname: Rastegar
authors.affiliation: Eye Center, Freiburg University Medical Center, Killianstr. 5, 79106 Freiburg, Germany.
authors.forename: Günther
authors.initials: G
authors.lastname: Schlunck
authors.affiliation: Eye Center, Freiburg University Medical Center, Killianstr. 5, 79106 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinhard
authors.affiliation: Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany.
authors.forename: Tilo
authors.initials: T
authors.lastname: Baumbach
authors.affiliation: Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Strähle
mesh_terms: D000818:Animals; D002386:Cataract / Q000517:prevention & control; D047108:Embryonic Development; D007908:Lens, Crystalline / Q000737:chemistry / Q000196:embryology* / Q000502:physiology*; D020460:Melanosomes / Q000378:metabolism*; D018384:Oxidative Stress; D010860:Pigments, Biological / Q000378:metabolism; D013052:Spectrometry, X-Ray Emission; D014131:Trace Elements / Q000032:analysis; D015027:Zebrafish / Q000196:embryology*
chemical_list: D010860:Pigments, Biological; D014131:Trace Elements