Expression is strongly enriched in the ventral midline at embryonic stage 16.

Expressed cyclically in the adult fat body.

Expression of cry is detected in up to six DN1p neurons, and sometimes in one or two DN3 neurons. Between one and three LNd neurons label positively for cry.

A doublet of ~2 kb is seen in adult head RNA preparations. The amount of cry RNA in the head oscillates during the circadian cycle, and cry is 6-11 fold more abundant at the daytime peak than at the nighttime trough. RNAse protection experiments indicate that cry is expresed in the adult brain. Expression is present in eyeless (eya) mutants, and is also detected at low levels in the adult body. No expression is detected in 0-24 hr embryos, whole third instar larvae or third instar larval brains. In situ hybridization studies indicate that cry is expressed in the adult central nervous system. Highest levels are detected in the lateral CNS, near or coincident with the position of the ventral group of Drosophila clock neurons. Expression is also detected in the gut.

cry is detected in adult heads and bodies and in pupae on Northern blots, and in larvae by RT-PCR. cry expression in the adult head shows circadian cycling. The cycling is gradually diminished in conditions of constant darkness. cry oscillations are not detected in per or tim mutant flies.

RT-PCR and Northern blot analyses indicate that cry transcript is more abundant in adult heads than in bodies. Fivefold higher expression is detected in antennae compared to mouth appendages and wings, and expression is also detected in legs.

cry mRNA from adult heads shows 5-fold amplitude cycling under standard light/dark (LD) conditions, with a peak at Zeitgeber time (ZT) 1-7, and a trough at ZT17-ZT19. Cycling persists in constant darkness (DD), but with a lower, approximately 2-fold amplitude. Cycling is also detected in the adult body, but with only a 2.5-fold amplitude. Transcriptional cycling detected under LD and DD conditions using nuclear run-on assays indicates that the mRNA oscillations are regulated largely at the transcriptional level. cry transcript levels are low in tim and per mutants, but are high in Clk and cyc mutants.

cry protein is expressed in s-LNv neurons, l-LNv neurons, and a subset of LNd neurons and DN1 neurons, but not in DN2 and DN3 neurons. It is also detected in the pars intercerebralis and the medial protocerebrum.

Expression of cry is found in three of the six LNd neurons and in six cells of the DN1p cluster when the flies are kept in constant dark (DD) conditions. In some samples, a fourth LNd also faintly labels. Expression is detected in several cells in the anterior central brain, dorsolateral to the antennal lobes which project to the ellipsoid body. Expression of cry is detected in putative glial cells of brains from flies kept in DD conditions for 4.5 days prior to dissection. Photoreceptors R7 and R8 show a faint accumulation of cry in their distal medulla termini when flies are kept in DD for 4.5 days, but is more extensive along axons in flies maintained in constant dark conditions for 8 days. Following 35 hours of DD conditions, cry is observed in both the nucleus and cytoplasm of the s-LNv, l-LNv, DN1 and LNd neurons, but staining in the cytoplasm is stronger than in the nucleus. Expression of cry increases in the cry-expressing cells with increased time spent in dark conditions, compared to samples raised in light-dark conditions. Expression of cry shows a cycling behaviour, with levels being increasing during the dark-periods and decreasing during the light-periods, though cry was still detectable in clock neurons 1hr after lights on.

cry protein expression in light/dark entrained y w;Scer\GAL4^tim.PE lines shows an 8-fold amplitude cycling, with low levels during the day and a peak at ZT23. By contrast, mRNA levels are high during the day. A far lower amplitude cycling of cry protein is seen in wild type flies, possibly due to light shielding by eye pigment in wild type flies. Unlike per, tim, and Clk proteins, the DD and LD patterns of cry protein expression differ greatly. In conditions of constant darkness (DD), cry protein levels increase continuously.