Rhythmic control of rest-activity cycles in Drosophila

M. FERNANDA CERIANI

Huerta Grande, Cordoba

Taller; X Taller Argentino de Neurociencias; 2008

Clock output pathways are central to convey timing information from the circadian clock to a diversity of output systems, ranging from cell-autonomous processes to physiology and behavior. While the molecular mechanisms that generate and sustain rhythmicity at the cellular level are well understood, how this information is further structured to control specific behavioral outputs remains an open question. Rhythmic release of pigment dispersing factor (PDF) has been proposed to propagate the ¨time of day¨ information from core pacemaker cells to downstream targets underlying rhythmic locomotor activity. Indeed, such circadian changes in PDF intensity represent the only known mechanism through which the PDF circuit could communicate with its output. Our lab is interested in understanding the cellular basis of this rhythmic behavior; towards this goal we are characterizing the effect on locomotor behavior of mutations in genes key to determine the fine structure (such as the axon guidance receptor roundabout) or functional properties (such as the Ca2+ dependent, voltage-gated potassium channel slowpoke) of the circadian network. While characterizing the PDF circuit in more detail we noticed that it displayed a higher complexity during the day and significantly lower at nighttime.  Thus we defined a novel circadian phenomenon involving extensive remodeling in the axonal terminals of the PDF circuit both under daily cycles and constant conditions. Further supporting its circadian nature cycling is lost in bonafide clock-less mutants. We propose this clock-controlled structural plasticity as a candidate mechanism contributing to the transmission of the information downstream of pacemaker cells.