DPP signaling contributes to set basic properties of the Drosophila circadian network

EJ BECKWITH; J BERNI; MF CERIANI

Casa Serrana, Huerta Grande, Córdoba

Congreso; I Reunión Conjunta de Neurociencias; 2009

TAN, SAN

Living organisms use circadian rhythms to maintain internal temporal order and anticipate daily environmental changes. Clocks employ self-sustained biochemical oscillators and manifest at molecular, physiological and behavioral levels. In Drosophila, a group of neurons expressing the Pigment Dispersing Factor (PDF) represent the so- called “central oscillator” of the fly brain. As a result of a missexpression screen using the GAL4/UAS system we identified a fly strain that causes period lengthening of the daily activity rhythms. The transposon landed within schnurri (shn), a nuclear component of the decapentaplegic (dpp) signal transduction pathway. shn overexpression in the PDF+ circuit is necessary and sufficient to generate a 25.5h period of locomotor behavior while downregulation of shn levels cause a deconsolidation of the behavioral rhythms. A detailed analysis of PER subcelular localization throughout the day indicated a delayed PER nuclear entry in the mutant compared to that of wild type flies, pointing to a specific effect of shn deregulation on the core clock mechanism. Interestingly, constitutive overexpression of activated receptors that initiate the DPP signalling cascade also gave rise to long period phenotypes, in agreement with those observed upon shn overexpression. In contrast, downregulation of the endogenous receptors also impacted circadian rhythmicity. A recent report points to the dpp pathway as a retrograde signal that set synaptic properties and, in combination with other cellular clues, establish the peptidergic fate of a specific circuit in the fly brain. In this context it is tempting to speculate that period lengthening could derive from a deregulated DPP signalling during development and/or maintenance of the PDF circuit.