A study by researchers at New York University and the University of London offers additional evidence that mammals and fruit flies share a common genetic makeup that determines the function of their internal biological clocks. The study appears in the latest issue of Current Biology. The research team consisted of post-doctoral researcher Ben Collins, Esteban Mazzoni, a graduate student, and Assistant Professor Justin Blau of NYU's Department of Biology and Professor Ralf Stanewsky of the University of London.
Drosophila fruit flies are commonly used for research on biological, or circadian, clocks because of the relative ease of finding mutants with non-24-hour rhythms and then identifying the genes underlying the altered behavior. These studies in fruit flies have allowed the identification of similar "clock genes" in mammals, which function in a similar manner in mammals as they do in a fly's clock. However, prior to this study, biologists had concluded that the role of one protein--Cryptochrome (Cry)--was quite different between flies and mammals. In fruit flies, Cry is a circadian photoreceptor, which helps light reset the biological clock with changing seasons, or in jet lag-style experiments (in which light is manipulated to mimic the experience of traveling over multiple time zones) in the lab. In mammals, however, Cry assists in the 24-hour rhythmic expression of clock genes and has nothing to do with re-setting the clock.
The researchers sought to determine additional roles for Cry in fruit flies by testing the rhythmic expression of clock genes in flies with either a mutant version of Cry, or with Cry produced at artificially high levels. In both cases, they found that the clock had stopped -- with high levels of clock gene expression when Cry was mutated, and low levels when Cry was over-produced. These results indicated that Cry normally inhibits clock gene expression in many clock cells -- just as it does in the mammalian clock.
"In addition to finding a new function for Cryptochrome, the results reinforce that notion that fruit flies provide an excellent model for understanding the human biological clock that drives sleep/wake cycles and many other processes that contribute to our overall health," said Blau.
The research was supported by a grant from the National Institutes of Health.
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