Cryptochrome is present in the compound eyes and a subset of Drosophila's clock neurons

Abstract

Cryptochrome (CRY) is intimately associated with the circadian clock of many organisms. In the fruit fly Drosophila melanogaster, CRY seems to be involved in photoreception as well as in the core clockwork. In spite of the critical role of CRY for the clock of Drosophila, it was not quite clear whether CRY is expressed in every clock cell. With the help of a new antibody and a mutant that lacks CRY, we show here that CRY is expressed in specific subsets of Drosophila's pacemaker neurons and in the photoreceptor cells of the compound eyes. In the pacemaker neurons, CRY levels and kinetics under light-dark cycles are quite different from each other. High-amplitude oscillations are observed in only three groups of clock neurons, suggesting that these three groups are strongly receptive to light. The different CRY kinetics may account for phase differences in oscillations of the clock proteins observed in these three groups in earlier studies. The molecular clock of the neurons that contain lower CRY levels or are completely CRY negative can still be synchronized by light, probably via intercellular communication with the CRY-positive neurons as well as via external photoreceptors.

PDF and cAMP enhance PER stability in Drosophila clock neurons

“…Brains were incubated in the AHL with drugs as described above (same concentration used in S2 cell culture) or 10 μM PDF peptide (100 μM stock in AHL) and kept in incubator for 6 h. Then the brains were fixed and processed as the protocol previously described (53). For PER staining, a precleaned polyclonal rabbit anti-PER by per 01 fly head extract was used at a 1:50 dilution (50).…”

Light-arousal and circadian photoreception circuits intersect at the large PDF cells of the Drosophila brain

“…Indeed, pdfGal4:UAS-Cry rescue of cryb phase shifting was most effective in the late night, and CRY levels in the l-LNvs normally reach a peak in the late night (9,25). Although shaggy (SGG) overexpression with timGal4 led to a reduced phase delay at ZT15 as well as a reduced phase advance at ZT21, addition of the pdfGal80 transgene rescued only the ZT21 phase advance (8).…”

Fly cryptochrome and the visual system

“…Motion detection depends mainly on intact vision in photoreceptors R1-6 with minor contribution from R7 and R8 (35,36), whereas phototaxis is mediated by all eight photoreceptors in the compound eyes (37). dCRY is expressed in the entire cytoplasm of the photoreceptor cells and seems to have the highest density close to the rhabdomers, the place of the visual cascade (38). Therefore, dCRY may easily interact with INAD and eventually modulate the transient receptor potential (TRP) and TRP-like (TRPL) channel opening in interplay with the other PDZ proteins of the Signalplex.…”