A novel roundabout mutation alters the pace of the clock in Drosophila.

JIMENA BERNI, ESTEBAN BECKWITH Y M. FERNANDA CERIANI

San Diego, USA

Congreso; Drosophila meeting; 2005

Society for Genetics

Locomotor activity in Drosophila is controlled by the circadian clock.  period (per) expression in a group of brain neurons defines the pacemaker center.  This center includes the ventral Lateral Neurons (LNvs), which express the Pigment-dispersing factor (PDF) neuropeptide, together with the PDF-negative dorsal lateral neurons (LNds) and Dorsal Neurons (DNs).  The synchronization of this circuitry ensures rhythmicity of the rest-activity cycles.  It is therefore anticipated that any defect in the connectivity of such pacemaker neurons should impact locomotor behavior.  To evaluate this possibility we characterized a novel adult viable hypomorph mutant of roundabout, which we named robohy.  The robohy mutation produced occasional errors in midline guidance and less tight axon fasciculation in the embryonic central nervous system (CNS), which correlated with decreased robo mRNA and protein levels.  To our surprise we could detect ROBO in the adult CNS by immunocytochemistry and western blot.  robohy mutants displayed a shortening of the periodicity of locomotor activity.  Detailed analysis of the PDF positive circuit in the adult brain showed ectopic small LNvs as well as subtle changes in the fibers running along the posterior optic tract.  To determine the effect of robohy in the circadian clock overall levels as well as sub-cellular localization of PER in the LNvs was evaluated.  Consistent with the shorter behavioral rhythms we detected a premature entrance of PER to the nucleus compared to wild type controls.