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Cloning, Chromosomal Localization and Functional Expression of the Gene Encoding the α-Subunit of the cG-MP-Gated Channel in Human Cone Photoreceptors

Authors

  • Bernd Wissinger,

    Corresponding author
    1. Molekulargenetisches Labor, Universitäts-Augenklinik Abteilung II, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
    • Bernd Wissinger, Molekulargenetisches Labor, Universitats-Augenklinik Abt. II, Auf der Morgenstelle 15, D-72076 Tübingen, Germany

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  • Frank Müller,

    1. lnstitut für Biologische lnformationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany
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  • Ingo Weyand,

    1. lnstitut für Biologische lnformationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany
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  • Simone Schuffenhauer,

    1. Abteilung für pädiatrische Genetik der Kinderpoliklinik, Ludwig-Maxirnilians-Universität, Goethestr. 29, D-80336 München, Germany
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  • Solon Thanos,

    1. Forschungslaboratoriurn, Abteilung I der Universitäts-Augenklinik, Auf der Morgenstelle 15, 0–72076 Tübingen, Germany
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  • U. Benjamin Kaupp,

    1. lnstitut für Biologische lnformationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany
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  • Eberhart Zrenner

    1. Molekulargenetisches Labor, Universitäts-Augenklinik Abteilung II, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
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Abstract

Cyclic nucleotide-gated (CNG) ion channels serve as final targets of signal transduction in vertebrate photoreceptors. While the basic mechanisms of phototransduction are similar in rod and cone photoreceptors, both cell types express distinct sets of components of the transduction pathway. We report here the cloning of the cDNA encoding the α-subunit of the cGMP-gated channel of human cone photoreceptors. The open reading frame predicts a polypeptide of 694 amino acid residues with conserved functional parts and amino acid positions typical for the α-subunit of CNG-channels. Heterologous expression of the cDNA in Xenopus oocytes gave rise to cGMP-gated channel activity. Antiserum directed against the C-terminus of the bovine cone CNG channel α-subunit crossreacted specifically with the heterologously expressed polypeptide and stained cone photoreceptors and weakly also the outer plexiform layer in human retinal sections. Northern blot analysis detected a prominent mRNA species of ∼3.8 kb in human retina. The entire gene spans ∼30 kb of genomic sequence and is located on the pericentric band q11.2 of human chromosome 2. The gene is composed of seven exons, with introns located at positions which are preserved with respect to the human rod gene, indicating a common ancestral gene structure. RT-PCR analysis gave no evidence for alternatively spliced transcripts.

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