Source: University Of Auckland
“It controls everything from behaviour to physiology. The primary implication in this study is that death, at least in flies, can be reliably predicted in clock gene expression.”
“We used the flies as a model because we can monitor the circadian clock rhythms in the living flies right down to cycling of individual clock genes.”
Jia says the study looked specifically at two circadian clock genes, PERIOD and TIMELESS (which have similar counterparts in humans) and how they change in the days immediately preceding death and the clock stops cycling. The significance of the finding is the linking of the breakdown in the circadian clock with death.
The fruit fly was chosen for the study as it has a short life cycle and shares a similar circadian clock to humans. While breakdown of the clock in behaviour has been observed before, no-one has tested clock gene expression.
“We can tell when the fruit fly is going to die by studying markers in the TIMELESS gene. When that gene starts to increase and loses rhythmicity in the fruit fly you know that particular fly is going to die in four days.
“We hypothesise that it’s the break-down in communication between the peripheral clock cells which causes this,” she says.
“The flies don’t have to be old to show this pattern, it’s a marker in young flies as well as old. If there is a loss of this pattern in the PERIOD and TIMELESS genes then they die as well.”
The team sourced thousands of fruit flies and kept them in regular light/dark cycles with constant temperature or with temperature cycles to test the influence of entrainment. The health of the insects was monitored dailyand they were transferred into a plate reader to monitor the bioluminescence (glowing) signal of the genes every hour for at least 10 days.
This fly provides a model for the aging of clocks more generally and has implications for other animals and humans.
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