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

NARA I. MURARO; FLORENCIA FERNÁNDEZ; LIA FRENKEL; M. FERNANDA CERIANI; CARINA C. COLQUE; BRYAN HAHM

Palm Harbor, Florida

Congreso; 15th Biennial Meeting, Society for Research on Biological Rythms; 2016

Society for Research on Biological Rythms

Ion channels that regulate neuronal physiology and circadian behavior in Drosophila melanogasterNara I. Muraro 1,2 , Carina C. Colque 2,3 , Lia Frenkel 2 , Florencia Fernández 1 , Bryan Hahm 1 and M.Fernanda Ceriani 21 Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute ofthe Max Planck Society, Buenos Aires, Argentina.2 Fundación Instituto Leloir-IIB- BA-CONICET, Buenos Aires, Argentina.3 Present address, CRILAR-CONICET, La Rioja, Argentina.Circadian rhythms have been extensively studied in the fruit fly where many clock genes that interlock through negative feedback loops and generate daily oscillations have been described. Clock genes are expressed in approximately 150 clock neurons 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 allow them to change their firing rate on a daily basis. We have performed a behavioral genetic screen through the downregulation of candidate voltage-gated ion channels using RNA-interference specifically in LNvs. Among the positive hits we focused our attention on the hyperpolarisation-activated cation current I h . In mammalian neurons, this channelis involved in complex neuronal behaviors such as bursting, the same firing pattern that LNvs display. Here, we show that I h expression is important for the behaviors that LNvs command.Moreover, using genetics and pharmacology coupled to whole-cell patch clamp electrophysiology in ex vivo Drosophila brains, we show that I h is necessary to achieve the high frequency bursting firing pattern of LNvs. Since bursting firing has been associated to neuropeptide release, we hypothesized that I h would be important for PDF-mediated communication. This is indeed the case; we found that constitutive downregulation of I h affects sLNvs development and adult-specific downregulation of I h affects PDF levels and structural plasticity of sLNvs dorsal projections.