Analysis of period mRNA cycling in Drosophila head and body tissues indicates that body oscillators behave differently from head oscillators.

Abstract

The period (per) gene is thought to be part of the Drosophila circadian pacemaker. The circadian fluctuations in per RNA and protein that constitute theper feedback loop appear to be required for pacemaker function, and have been measured in head neuronal tissues that are necessary for locomotor activity and eclosion rhythms. The per gene is also expressed in a number of neuronal and nonneuronal body tissues for which no known circadian phenomena have been described. To determine whether per might affect some circadian function in these body tissues, per RNA cycling was examined. These studies show that per RNA cycles in the same phase and amplitude in head and body tissues during light-dark cycles. One exception to this is the lack ofper RNA cycling in the ovary, which also appears to be the only tissue in which PER protein is primarily cytoplasmic.In constant darkness, however, the amplitude ofper RNA cycling dampens much more quickly in bodies than in heads. Taken together, these results indicate that circadian oscillators are present in head and body tissues in which PER protein is nuclear and that these oscillators behave differently.Circadian rhythms influence many biochemical, physiological, and behavioral processes in plant, animal, and microbial systems (10). In any organism, different rhythms must be coordinated with respect to each other and to the time of day. This coordination results from the action of an endogenous, genetically driven circadian clock that persists under constant environmental conditions, is reset by environmental parameters such as light and temperature, and is relatively temperature independent.To understand the molecular circuitry underlying circadianclock function, genetic screens have been performed to isolate mutants having altered circadian rhythms. Mutations in the period (per) gene of the fruit fly Drosophila melanogaster can shorten (perS), lengthen (perL), or abolish (perel) circadian rhythms in eclosion and locomotor activity (17). As per function also appears to be necessary for entrainment (to light-dark cycles) of the circadian clock (7), it is likely that per expression is required for flies to either measure or tell time. An important aspect of per expression is that its mRNA and protein products undergo daily fluctuations in abundance (12, 36). These fluctuations constitute a feedback loop in which per mRNA is the template for per protein (PER) synthesis and PER is necessary for the circadian synthesis of its own mRNA (12,36). Since PER is nuclear in most tissues (22) and is able to repress its own RNA's synthesis (35), it is thought to function by directly repressing its own gene's activity (13). The regulatory features of the per feedback loop parallel formal theoretical models of self-sustaining circadian oscillators and might also accommodate the effects of PER on circadian behavior (13). Thus, the per feedback loop is thought to be a critical component of the Drosophila circadian clock.The per feedback loop was initially shown to function in many neuronal ti...

Circadian genes in a blind subterranean mammal II: Conservation and uniqueness of the threePeriodhomologs in the blind subterranean mole rat,Spalax ehrenbergisuperspecies

“…All three Spalax Per genes are expressed in a wide variety of nonneural tissues as previously shown in Drosophila (53,54) and mice (39,41). In three of these tissues (liver, eye, and harderian gland) we found that the RNA levels for the three sPer genes oscillate.…”

Circadian control by the reduction/oxidation pathway: Catalase represses light-dependent clock gene expression in the zebrafish

“…6D). Studies in a variety of species have reported that each single cell contains a cellautonomous and self-sustained oscillator whose phases are not synchronized to each other in the absence of external time cues (34)(35)(36)(37)(38)(39). zCRY1a and zPER2 interact with each other, forming a heterodimer that functions as a repressor of CLOCK:BMALmediated transcription (40,41).…”

Novel Gq alpha isoform is a candidate transducer of rhodopsin signaling in a Drosophila testes-autonomous pacemaker.

“…Per, a key pacemaker component (reviewed in ref. 31), has been shown to be expressed in both male and female gonads; however, male abdomens show a circadian oscillation of transcript levels that is absent in female abdomens (32). DGqC is an ideal transducer in this putative clock-input pathway, as it has the divergent Rh-binding exon and the nonvisual PLC-binding exon.…”