Non-invasive red-light optogenetic control ofDrosophilacardiac function

Abstract

Drosophila is a powerful genetic model system for cardiovascular studies. Recently, optogenetic pacing tools have been developed to control Drosophila heart rhythm noninvasively with blue light, which has a limited penetration depth. Here we developed both a red-light sensitive opsin expressing Drosophila system and an integrated red-light stimulation and optical coherence microscopy (OCM) imaging system. We demonstrated noninvasive control of Drosophila cardiac rhythms, including simulated tachycardia in ReaChR-expressing flies and bradycardia and cardiac arrest in halorhodopsin (NpHR)-expressing flies at multiple developmental stages. By using red excitation light, we were able to pace flies at higher efficiency and with lower power than with equivalent blue light excitation systems. The recovery dynamics after red-light stimulation of NpHR flies were observed and quantified. The combination of red-light stimulation, OCM imaging, and transgenic Drosophila systems provides a promising and easily manipulated research platform for noninvasive cardiac optogenetic studies.

FlyNet 2.0: drosophila heart 3D (2D + time) segmentation in optical coherence microscopy images using a convolutional long short-term memory neural network

“…Besides testing flies at different development stages, two different heartbeat situations were selected to test with FlyNet 2.0. The first situation was a steady heartbeat throughout the whole OCM video, and the second was a heartbeat frequency that changed during the whole OCM video due to optogenetic pacing [40]. For each situation, a 4000 or 6000 frames fly heartbeat video was segmented with FlyNet 2.0.…”

“…The heart rate is around 100 beats per minute for the fly heartbeat video. The second example involves the alteration of the heartbeat frequency over the course of the OCM video of a larva, driven by optogenetic pacing [40]. The OCM video includes 4000 frames recorded over 35 seconds.…”

“…After each tachypacing, the heart rate slows down below the resting heart rate then gradually recovers. Immediately after the repeated pacing challenge, the heartbeat further slows down and takes a longer time to recover [40]. Tachypacing challenges the heartbeat by forcing the fly heart to follow the pacing frequencies, which induces stress on the heart.…”

<p>Optogenetic Pacing: Current Insights and Future Potential</p>

“…Optogenetic fly models are sensitive to the fact that red light is absorbed less strongly than blue light to increase the excitability of the heart tissue and flies expressing ReaChR were able to be tachypaced under red light stimulation ( Figure 3). 40,41 Optogenetic…”

“…2020;3:336. Creative Commons license and disclaimer available from: http://creativecommons.org/licenses/by/4.0/ legalcode 40. Methods was used from reference41 to create this image.…”