Novel Features of Cryptochrome-Mediated Photoreception in the Brain Circadian Clock ofDrosophila

Cry protein is expressed in most neuronal groups in Drosophila but is absent in larval dorsal neurons (DN2s), leading to unique antiphase PER cycling.

• Light affects circadian rhythms in Drosophila through distinct mechanisms involving phototransduction and the photopigment cryptochrome (cry).
• Larval DN2s exhibit antiphase PER cycling due to the absence of cry expression, which can be corrected by forcing cry expression in these neurons.
• CRY protein shows instability in light but accumulates in the dark within the nucleus, cytoplasm, and neuritic projections of the neurons.
• Adult DN1 neurons coexpress CRY and the photoreceptor differentiation factor GLASS, linking them to light sensitivity in the circadian clock.
• CRY-independent light inputs to the central behavioral clock require the visual system for proper function.
• DN1 neurons do not function as autonomous oscillators, as their PER oscillations decrease in constant darkness without signaling from ventral lateral neurons.

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