title: Seasonally Changing Cryptochrome 1b Expression in the Retinal Ganglion Cells of a Migrating Passerine Bird.
abstract: Cryptochromes, blue-light absorbing proteins involved in the circadian clock, have been proposed to be the receptor molecules of the avian magnetic compass. In birds, several cryptochromes occur: Cryptochrome 2, Cryptochrome 4 and two splice products of Cryptochrome 1, Cry1a and Cry1b. With an antibody not distinguishing between the two splice products, Cryptochrome 1 had been detected in the retinal ganglion cells of garden warblers during migration. A recent study located Cry1a in the outer segments of UV/V-cones in the retina of domestic chickens and European robins, another migratory species. Here we report the presence of cryptochrome 1b (eCry1b) in retinal ganglion cells and displaced ganglion cells of European Robins, Erithacus rubecula. Immuno-histochemistry at the light microscopic and electron microscopic level showed eCry1b in the cell plasma, free in the cytosol as well as bound to membranes. This is supported by immuno-blotting. However, this applies only to robins in the migratory state. After the end of the migratory phase, the amount of eCry1b was markedly reduced and hardly detectable. In robins, the amount of eCry1b in the retinal ganglion cells varies with season: it appears to be strongly expressed only during the migratory period when the birds show nocturnal migratory restlessness. Since the avian magnetic compass does not seem to be restricted to the migratory phase, this seasonal variation makes a role of eCry1b in magnetoreception rather unlikely. Rather, it could be involved in physiological processes controlling migratory restlessness and thus enabling birds to perform their nocturnal flights.
authors.affiliation: Fachbereich Biowissenschaften der Goethe-Universität Frankfurt, Max-von-Laue-Str. 13, D-60438, Frankfurt am Main, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Nießner
authors.affiliation: Fachbereich Biowissenschaften der Goethe-Universität Frankfurt, Max-von-Laue-Str. 13, D-60438, Frankfurt am Main, Germany.|Haematology and Oncology and Developmental Biochemistry, University Medicine Göttingen, Justus-von-Liebig Weg 11, 37077, Göttingen, Germany.
authors.forename: Julia Christina
authors.initials: JC
authors.lastname: Gross
authors.affiliation: Fachbereich Biowissenschaften der Goethe-Universität Frankfurt, Max-von-Laue-Str. 13, D-60438, Frankfurt am Main, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Denzau
authors.affiliation: Max Planck Institute for Brain Research, Max-von-Laue-Str. 4, D-60438, Frankfurt am Main, Germany.
authors.forename: Leo
authors.initials: L
authors.lastname: Peichl
authors.affiliation: Fachbereich Biowissenschaften der Goethe-Universität Frankfurt, Max-von-Laue-Str. 13, D-60438, Frankfurt am Main, Germany.
authors.forename: Gerta
authors.initials: G
authors.lastname: Fleissner
authors.affiliation: Fachbereich Biowissenschaften der Goethe-Universität Frankfurt, Max-von-Laue-Str. 13, D-60438, Frankfurt am Main, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wiltschko
authors.affiliation: Fachbereich Biowissenschaften der Goethe-Universität Frankfurt, Max-von-Laue-Str. 13, D-60438, Frankfurt am Main, Germany.
authors.forename: Roswitha
authors.initials: R
authors.lastname: Wiltschko
mesh_terms: D025041:Animal Migration; D000818:Animals; D056931:Cryptochromes / Q000235:genetics*; D005786:Gene Expression Regulation; D046109:Passeriformes / Q000235:genetics*; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D012621:Seasons
chemical_list: D056931:Cryptochromes