1. Role of Clock Gene period in Starvation Resistance
Drosophila melanogaster
A Research Project by: Sarah Strawn
Mentored by: Dr. Jaga Giebultowicz

2. Circadian Rhythms 24 hour Cycles that keep you on schedule.
Circa- about/around
Dia- day
Each cycle influences aspects of your body’s function.
-Sleep/wake cycles, heart rate, blood pressure, and hormone secretion.
There are more than 100
Circadian rhythms in the human body.

3. Period Gene and Emergence
Period (per) was the first clock gene discovered based on a mutation
in emergence patterns.
Genetic Basis of
Biological Clock
-Mutants that lack functional period
are arrhythmic.
No. of flies emerged
Period was so named
due to other alleles that produced emergence rhythm with periods either shorter or longer than 24 hours.
days

4. Why Flies? Drosophila is an established model for biomedical research
More than 75% of human disease loci have counterparts in fly.
Per gene is conserved between flies and mammals (including humans)
One per gene in Drosophila (but: Per1, Per2, Per3 in mice)

5. The period gene is the focus of this study
Period is expressed in most cells of the body
Loss of per function produces many phenotypes:
Behavioral arrhythmia
Disruption of courtship song
Decrease in fitness
may be involved in the regulation of metabolism
Starvation Resistance is an indirect measure of metabolism

6. Hypothesis
The period gene is involved in the regulation of starvation resistance in flies.
If the hypothesis is correct, the dosage of period gene should be a factor in determining how well flies respond to starvation.
Prediction: Flies with mutated period gene that produce no period protein will have the shorter survival time than flies with active period gene and normal levels of period protein.
Survival under starvation
w Control Flies
normal level of per
Mutant per- null flies

7. Objectives
Examine possible links between levels of period gene expression and starvation resistance.
Identify mechanism by which period affects survival under starvation.

8. Genotypes of flies used in this studyw
w per+/w per+;; – control flies that carry a white marker and normal period gene
w per0
w per0/w per0;; – containing inactive period gene (per- null) mutants.
Note: all flies were isogenized meaning that their genetic background is similar except for the genes indicated (per, w)

9. Starvation test Flies are placed into vials with filter paper
and water. Deaths are
recorded and water replaced every 12 hours.

10. Results
Resistance to starvation is significantly lower in mutants than in control females
This effect is not evident in virgins but is pronounced in mated females
>>We concentrated on mated females in further studies
Do control flies eat more than mutants?

11. How can we measure the amount of food flies consume?
Blue diet allows us to measure the amount of food flies eat. When a fly ingests food the
alimentary canal is stained blue.
Concentrations of blue dye in the gut were measured using spectrometer

12. Mutant flies eat more than control flies!
Do mutants weigh more than control flies at the onset of starvation?

13. Average Mass of Flies
Results: Both controls and mutants start out on equal footing.
It was determined that average mass was not statistically significant.

14. Summary of Results
Control flies live longer than mutants when subjected to starvation.
Mutants consume more food than control.
Both control and mutants have approximately equal mass before starvation.
These results suggest that mutants have problems with metabolism and storage of nutrients
What metabolic advantage do control flies have over mutants? I
Are they better able to make use of their resources when starved?
Do they have more fat reserves?

15. To survive starvation, cells use autophagy
During autophagy proteins that can be spared are digested in lysosomes and provide “recycled” nutrients
Lysotracker is a pH sensitive probe that can detect autophagy in larval fat body
Lysotracker turns red under acidic pH of active lysosomes
and Hoechst stains nucleus blue.
This dye was used to compare the intensity of autophagy between starved control and mutant flies.

16. Fat Content with Green Probe
Mutant
Control
Fat cells around sperm storage organ
Fat granule
Fat granule
Fat cells near alimentary tract
Preparations stained with: Hoechst DNA stain, Lysotracker and BODIPY neutral fat probe

17. Research in progress
Measure triglyceride levels at the onset and during the course of starvation in control and mutant flies.

18. Special Thanks Howard Hughes Medical Institute URISC Kevin Ahern
Brandy Rush
Channa Newell
Jessica Bruer
Andy Frazer
Jaga Giebultowicz