The First Circadian Rhythm

 The First Circadian Rhythm

The talk by Dan Cavanaugh dealt with circadian rhythms in an invertebrate, in this case Drosophila. The study tried to determine how the clock cells control behavior. They found that DH44, which is expressed by Pars Intercerebralis, is required for a proper rhythm. Further, they found the pathway was roughly S-LNVS to Dn1 to PI cell to DH44.
     How the circadian rhythm studied above may have evolved is explored in 'The Evolution of Sleep: 700 Million Years of Melatonin”. The European Molecular Biology Lab in Germany examined a worm called Platynereis Dumerilii to explore how this could have happened. In particular, they looked at melatonin production, and how if affected sleep rhythms, and its evolution in humans and other vertebrates. In the worm, it was found that cells that produced light sensitive proteins are also the cells that induce genes to synthesize melatonin. In these worms, it was also found that they only produce melatonin at night. The worms beat their tails to rise to the surface of the ocean during the day. They eventually reach the top, at which point is it nighttime, causing melatonin to be released. Melatonin then freezes the hairs, which causes the worm to descend. At the break of dawn, the melatonin dissipates, thus beginning the cycle anew. It was speculated that this system gave rise to activity rhythms in other organisms. However, it is not identical to other systems: in the worm the cells which catch light and produce melatonin are the same, while other organism have more specialization in this regard. Nevertheless, it might give some insight into how the first circadian rhythms may have been like. Perhaps by studying how the circadian rhythm arose, researchers can learn more about how it works.

Works Cited.
Zimmer, Carl “The Evolution of Sleep: 700 Million Years of Melatonin" The New York Times. 2 Oct 2014. Web. 13. Oct 2015.

http://www.nytimes.com/2014/10/02/science/the-evolution-of-sleep-700-million-years-of-melatonin.html

 Cavanaugh D., Geratowksi J., Wooltorton J., Spaethling J., Hector C., Zheng X., Johnson E., Eberwine J., Sehgal A. Identification of a Circadian Output Circuit for Rest:Activity Rhythms in Drosophila. 24 February 2014. 689-701. Web. 13. Oct 2015.

https://luc.app.box.com/neuroscienceseminar/1/4409565042/37277142342/1