Emergence of complex rhytms by desynchronization of Drosophila circadian clusters

ESTEBAN J. BECKWITH; MARÍA FERNANDA CERIANI

Cancun

Congreso; FALAN meeting; 2012

The set of adaptations that lead to the adjustment to the 24h environmental changes are the result of the action of the circadian clock, which is present in all forms of life. In Drosophila, the underlying molecular mechanism has extensively been studied, and is composed of two interlocked transcriptional–translational negative feedback loops along with post-translational modifications of proteins. The identification of the molecular components has enabled the localization of the neuronal substrate of the clock in the fly brain. About 150 neurons comprise the circadian network and can be divided into the small and large ventral lateral neurons (sLNv and lLNv, respectively), and the sLNvs are considered the central pacemaker, the dorsal lateral neurons (LNd), three groups of dorsal neurons (DN1, DN2, and DN3) and the lateral posterior neurons (LPN). Defining the rules that govern the communication between these different clusters will shed light onto how molecular oscillations translate into coherent behavior. Slowing down the pace of the molecular clock within the LNvs by reduction of the critical kinase SHAGGY (SGG) and the activation of the BMP pathway concomitantly, separates the endogenous period of this neuronal cluster from that of the rest of the network. This condition led to complex circadian behavior when flies were kept in free running conditions. Flies exhibited two or three stable locomotor activity rhythms simultaneously: an extremely long component, likely driven by the LNvs; a second one around 24h probably reflecting the endogenous period of the rest of the network, and a third shorter component, that is not always present, could be accounted for the endogenous period previously reported for the LNd clusters. These results clearly demonstrate that although there is a hierarchy among clusters, the proper functioning of the circadian system and the emergence of a wild type locomotor activity pattern is indeed a network property.