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Schlagwörter:
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Zusammenfassung:
Migratory birds can use a magnetic compass for orientation during
their migratory journeys covering thousands of kilometers. But
how do they sense the reference direction provided by the Earth’s
magnetic field? Behavioral evidence and theoretical considerations
have suggested that radical-pair processes in differently oriented,
light-sensitive molecules of the retina could enable migratory birds
to perceive the magnetic field as visual patterns. The cryptochromes
(CRYs) have been suggested as the most likely candidate
class of molecules, but do CRYs exist in the retina of migratory
birds? Here, we show that at least one CRY1 and one CRY2 exist in
the retina of migratory garden warblers and that garden-warbler
CRY1 (gwCRY1) is cytosolic. We also show that gwCRY1 is concentrated
in specific cells, particularly in ganglion cells and in large
displaced ganglion cells, which also showed high levels of neuronal
activity at night, when our garden warblers performed magnetic
orientation. In addition, there seem to be striking differences in
CRY1 expression between migratory and nonmigratory songbirds
at night. The difference in CRY1 expression between migrants and
nonmigrants is particularly pronounced in the large displaced
ganglion cells known to project exclusively to a brain area where
magnetically sensitive neurons have been reported. Consequently,
cytosolic gwCRY1 is well placed to possibly be the primary
magnetic-sensory molecule required for light-mediated magnetoreception.
