Fruit Flies Reveal Circadian Clock Comparable to Human Clock
New research reveals that fruit flies and mammals may share a surprising evolutionary link in how they control body temperature through circadian rhythm, unlocking new ways to study the insects as models of human development and disease
The study posted online Sept. 13 by Current Biology reports that similar to people, Drosophila fruit flies a common research tool in life sciences have a genetically driven internal clock.
This circadian clock prompts the insects to seek
out warmer or cooler external temperatures
according to the time of the day.
Cold-blooded creatures change behavior
to alter body temperature, usually by
seeking out different external temperatures.
But fruit flies are the first cold-blooded species to
demonstrate their modification of temperature preference
behavior is controlled by a circadian clock.
"We show that Drosophila fruit flies exhibit a daily temperature preference rhythm that is low in the morning, high in the evening and that follows a similar pattern as body temperature rhythms in humans," said Fumika N. Hamada, PhD, principal investigator and a researcher in the Division of Pediatric Ophthalmology at Cincinnati Children's Hospital Medical Center.
Hamada: "This study also reports the first systematic analysis of the molecular and neural mechanisms underlying temperature preference rhythm in fruit flies."
The research is important to understanding how regulation of daily body temperature is linked to homeostasis the body's ability to maintain a stable internal environment while exposed to changes in the external environment.
Failure to manage related stress and maintain homeostasis can lead to abnormal function and disease, Hamada said.
The circadian clock's internal control of body temperature
rhythm in warm-blooded mammals, including humans,
allows them to maintain homeostasis by regulating
sleep and metabolic energy use.
The study by Hamada and colleagues is the first to
demonstrate that fruit flies have a similar circadian clock
system for temperature control, although one more
influenced by external temperatures than for mammals.
It also is the first to show that Drosophila's behavior modification to adjust body temperature is not controlled by a subset of pacemaker neurons in the brain responsible for locomotor activity.
By subjecting a variety of genetically altered flies
to different degrees of light and darkness and
then analyzing the insect's brains,
the scientists identified a pacemaker neuron
in the dorsal region of the fruit fly brain.
Called DN2, it controls the bug's temperature
preference rhythm. The function of this neural
circuit had previously been unknown,
according to researchers.
Hamada said continued study of the newly discovered circadian clock for Drosophila temperature preference rhythm may help explain mechanisms that underlie body temperature control in animals. It also could provide a better understanding of circadian rhythm's changeability from external influences.
Funding support for the study came from the National Institutes of Health (RO1grants GM079182 and NS052854), the March of Dimes, funding from the Precursor Research for Embryonic Science and Technology (PRESTO) program at the Japan Science Technology Agency, and a Trustee Grant from Cincinnati Children's Hospital Medical Center. The first author of the study was Haruna Kaneko, PhD., a member of Hamada's laboratory team. Also collaborating were Paul Hardin, Department of Biology and Center for Biological Clocks Research at Texas A&M University, and Patrick Emery, Department of Neurobiology and Program in Neuroscience, at the University of Massachusetts Medical School.
About Cincinnati Children's:
Cincinnati Children's Hospital Medical Center ranks third in the nation among all Honor Roll hospitals in U.S. News and World Report's 2012 Best Children's Hospitals ranking. It is ranked #1 for neonatology and in the top 10 for all pediatric specialties. Cincinnati Children's is one of the top two recipients of pediatric research grants from the National Institutes of Health. It is internationally recognized for improving child health and transforming delivery of care through fully integrated, globally recognized research, education and innovation. Additional information can be found at www.cincinnatichildrens.org.
Original article: http://www.eurekalert.org/pub_releases/2012-09/cchm-ffr091012.php