Rhythmic structural plasticity in the circuit controlling rest-activity cycles in Drosophila.

MP FERNÁNDEZ, J BERNI AND MF CERIANI

Atlanta, Georgia, USA

Congreso; 36th annual meeting Society for Neuroscience,; 2006

Society for Neuroscience

Although the molecular processes underlying circadian clocks in Drosophila have been described in great detail in recent years, little is known about the mechanisms that allow pacemaker cells to transmit this information to their downstream targets. It is widely accepted that rhythmic locomotor behavior depends on an intact molecular oscillator operating within the circadian circuitry, which is comprised of 3 major clusters, out of which the small ventral lateral neurons (LNv) are at the top of the hierarchy. These neurons send their projections towards the dorsal protocerebrum, and release pigment dispersing factor (PDF) at these terminals, presumably in a circadian manner. Supporting its link to clock-controlled locomotor behavior, PDF levels are affected in arrhythmic clock mutants. However, recent data suggests that PDF cycling in dorsal protocerebrum is not necessary for the maintenance of rhythmic behavior under constant conditions, prompting a more thorough analysis of the PDF function at this level. This highly organized circadian network depends on the proper establishment of the synaptic connections among the different neuronal clusters involved, and since modulating different aspects of neural architecture would provide the flexibility to respond to changing developmental or environmental cues, we speculated that changes observed in PDF intensity at the pacemakers axonal terminals could derive from circadian regulation of axonal plasticity, most likely through cytoskeletal regulatory mechanisms.  We are currently investigating the role of synaptic activity and other factors potentially affecting the structure of this relevant circuit and its connection to rhythmic behavior employing a combination of transgenic markers and mutant backgrounds to follow the PDF circuit under different developmental and temporal conditions.