| | Category | ZO | L30 | Role of Drosophila Glial Cells in Circadian Regulation of Locomotor |
| | Activity |
| | Abstract | The brain of the fruit fly Drosophila consists of approximately 100,000 |
| | neurons, around 150 of which regulate the circadian clock. Within those |
| | 150 neurons, two major proteins, PERIOD (PER)and TIMELESS (TIM), both |
| | transcribed by the CYCLE/CLOCK (CYC/CLK) heterodimer, help maintain a |
| | circadian rhythm by oscillating in concentration. These proteins help |
| | maintain a daily rhythm of 24 hours even in the absence of environmental |
| | cues. While the neuronal circuitry regulating the circadian cycle of |
| | Drosophila have been widely researched, little is known about the role of |
| | glial cells in circadian timekeeping. Previous studies have revealed that glia |
| | express PER and TIM in an oscillating manner, suggesting that glia may be |
| | play a role in circadian timekeeping. This study seeks to determine the role |
| | of glia in circadian timekeeping. In this study, the oscillation of PER and TIM |
| | in glia was eliminated by preventing the formation of the CYC/CLK |
| | heterodimer, which initiates the transcription of the genes per and tim. This |
| | elimination of the oscillation was achieved using a GAL4/UAS system in |
| | which flies containing the gene uas-ΔCYC are crossed with flies |
| | containing the Repo-GAL4 gene. Repo-Gal4 is a gene that expresses the |
| | yeast transcription activator protein Gal4 exclusively in glia. uas- |
| | ΔCYC is a gene containing the promoter UAS that uses Gal4 to |
| | express ΔCYC, a dominate-negative mutation of the CYC gene. In |
| | addition, a cross between Repo-GAL4 flies and flies containing the gene |
| | uas-DBTS was tested. Double-timeS (dbtS) is one of the alleles of the |
| | gene double-time(dbt). dbtS expresses a kinase that increases the rate of |
| | degradation of PER and TIM concentrations, leading to a shorter circadian |
| | period. Lastly, Repo-GAL4 flies were crossed with per01;;uas-PER flies in |
| | an attempt to rescue rhythmicity in per01 flies, flies that express no |
| | circadian rhythm. To monitor and analyze behavior, Drosophila Activity |
| | Monitoring (DAM) systems were used. Flies were individually loaded into |
| | the DAM systems and entrained for 7 days under a light/dark cycle of 12 |
| | hours of light and 12 hours of darkness. Afterwards, the flies kept in |
| | constant darkness at the same temperature for 9 full days. Analysis of the |
| | activity under constant darkness indicates that the w;uas- |
| | CYCΔ/+;repo-Gal4/+ flies continued to display a rhythm, even without |
| | PER/TIM cycling in the glia. Also, w;uas-DBTS/+;repo-Gal4/+ flies also did |
| | not display any reduced circadian period time. Furthermore, the |
| | per01;;Repo-Gal4/uas-PER flies did not display any rhythm, suggesting that |
| | the circadian cycle was not rescued. |
| | Bibliography | Helfrich-Förster C. 2005. Neurobiology of the fruit fly's circadian clock. |
| | Genes Brain Behav 4: 65–76. |