Ion channels that regulate neuronal physiology and circadian behavior in Drosophila melanogaster

NARA I MURARO

Providence, Rhode Island

Seminario; Brown University Neuroscience Seminar Series; 2016

Universidad de Brown

Circadianrhythms have been extensively studied in the fruit fly where many clock genesthat interlock through negative feedback loops and generate daily oscillationshave been described. Clock genes are expressed in approximately 150 clockneurons in the Drosophila brain.Among them, the pigment dispersing factor (PDF)-expressing lateral neurons (LNvs)have been found to play central roles as pacemaker (the small-LNvs) and arousal(the large-LNvs) neurons.Still,little is known on how the electrical properties of Drosophila clock neurons are specified, and what mechanisms allowthem to change their firing rate on a daily basis. We have performed a behavioralgenetic screen through the downregulation of candidate voltage-gated ionchannels using RNA-interference specifically in LNvs. Among the positive hitswe focused our attention on the hyperpolarisation-activatedcation current Ih. In mammalian neurons, this channel is involved incomplex neuronal behaviors such as bursting, the same firing pattern that LNvs display.I will be showing that Ih expression is important for the behaviorsthat LNvs command. Moreover, using genetics and pharmacology coupled towhole-cell patch clamp electrophysiology in exvivo Drosophila brains, we showthat Ih is necessary to achieve the high frequency bursting firingpattern of LNvs. Since bursting firing has been associated to neuropeptiderelease, we hypothesized that Ih would be important for PDF-mediatedcommunication. This is indeed the case; we found that constitutivedownregulation of Ih affects sLNvs development and adult-specificdownregulation of Ih affects PDF levels and structural plasticity ofsLNvs dorsal projections.