ABSTRACT
BACKGROUND: Circadian rhythms regulate physiology and behavior through transcriptional feedback loops of clock genes running within specific pacemaker cells. In Drosophila, molecular oscillations in the small ventral lateral neurons (sLNvs) command rhythmic behavior under free-running conditions releasing the neuropeptide PIGMENT DISPERSING FACTOR (PDF) in a circadian fashion. Electrical activity in the sLNvs is also required for behavioral rhythmicity. Yet, how temporal information is transduced into behavior remains unclear. RESULTS: Here we developed a new tool for temporal control of gene expression to obtain adult-restricted electrical silencing of the PDF circuit, which led to reversible behavioral arrhythmicity. Remarkably, PERIOD (PER) oscillations during the silenced phase remained unaltered, indicating that arrhythmicity is a direct consequence of the silenced activity. Accordingly, circadian axonal remodeling and PDF accumulation were severely affected during the silenced phase. CONCLUSIONS: Although electrical activity of the sLNvs is not a clock component, it coordinates circuit outputs leading to rhythmic behavior.
Subject(s)
Drosophila Proteins/physiology , Drosophila melanogaster/physiology , Drosophila/physiology , Neuropeptides/physiology , Period Circadian Proteins/physiology , Potassium Channels, Inwardly Rectifying/physiology , Animals , Animals, Genetically Modified/genetics , Animals, Genetically Modified/physiology , Biological Clocks , Brain/embryology , Brain/physiology , Circadian Rhythm , Drosophila/genetics , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Gene Silencing , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Male , Membrane Potentials , Motor Activity , Neurons/metabolism , Neuropeptides/genetics , Period Circadian Proteins/genetics , Potassium Channels, Inwardly Rectifying/geneticsABSTRACT
Drosophila is a well-established model to study the molecular basis of neurodegenerative diseases. We carried out a misexpression screen to identify genes involved in neurodegeneration examining locomotor behavior in young and aged flies. We hypothesized that a progressive loss of rhythmic activity could reveal novel genes involved in neurodegenerative mechanisms. One of the interesting candidates showing progressive arrhythmicity has reduced enabled (ena) levels. ena down-regulation gave rise to progressive vacuolization in specific regions of the adult brain. Abnormal staining of pre-synaptic markers such as cystein string protein (CSP) suggest that axonal transport could underlie the neurodegeneration observed in the mutant. Reduced ena levels correlated with increased apoptosis, which could be rescued in the presence of p35, a general Caspase inhibitor. Thus, this mutant recapitulates two important features of human neurodegenerative diseases, i.e., vulnerability of certain neuronal populations and progressive degeneration, offering a unique scenario in which to unravel the specific mechanisms in an easily tractable organism.
