Assesing the usefulness of an optogenetics setup to study the circadian clock of Drosophila melanogaster

GUSTAVO EZEQUIEL PEREZ; FACUNDO CABRERA; D. LORENA FRANCO; SEBASTIAN RISAU GUSMAN

Congreso; SAN 2021 XXXVI Annual meeting; 2021

Light-triggeredneural activation, or optogenetics allows the manipulation of neuralactivity with millisecond precision. Thesimplest protocol is to express,light-gatedion channel inneurons of interest.Webuiltan optogenetic setupto study neuralcircuits thatcontrolthecircadian clocks in flies. AsDrosophila,is supposed to be blind to red-shifted wavelengths,inthis work we employedChrimson,ared-shift ChR2variant,toinvivoactivate neurons without disturbing the circadian rhythms.ByexpressingChrimsonin fruitlessneurons wewere able toactivate courtship movementsin males, provingthe functionality of this system in our hands.Next,we quantified neuronal activation atdifferent wavelengths, intensities and stimulation times,employing the courtshipbehavioras a readout. Wefound that high light intensities were needed to evoke behavioralchanges.Then,asDN1p neurons control sleep and circadian rhythms, wedrove the expression of Chrimsononto these neurons.Surprisingly,we observed a clear increase in locomotor activity of control fliesduring light pulses, suggesting that these flies can see red light.This increase of activity is much less pronounced in flies expressingChrimson,which suggests that the opening of the channels partially suppressesthe activity increase. Thus,even though our results may support earlier findings, they also castsome doubts on the usefulness of Chrimsonas an optogenetic tool to study the neural control of sleep.