Optogenetic Heart Pacing and Heart Arrest in Drosophila melanogaster Using Integrated OCM Imaging and Light Stimulation System
Date of Award
Master of Science (MS)
Optogenetics has been widely applied to cardiovascular research using different models. Among them, Drosophila melanogaster (fruit fly) outstands for its similarity of human genes for disease modeling and short life cycle for rapid screening to analyze genetic mechanisms of heart disease. However, most of the current models only allow either activation or inhibition of the heartbeat, which is not sufficient to model complex arrhythmia. Our lab developed a novel Drosophila transgenic model based on a double transgenic line containing two light-sensitive genes, Channelrhodopsin-2 (ChR2) and Halorhodopsin2.0 (NpHR2.0), that enable dual-directional control of the heartbeat rhythm. Real-time optical control of the heart function was monitored by non-invasive Optical Coherence Microscopy (OCM), synchronized with optical stimulations by 470nm blue and 617nm red light pulses. ChR2 is a light-gated cation channel that causes cell depolarization upon blue light illumination, resulting in action potential and tissue activation. NpHR2.0 is an engineered light-gated chloride ion pump, sensitive to red light; NpHR2.0 activation causes cells hyperpolarization and functional repression. The heart-specific opsins expression was achieved by crossing the ChR2 and NpHR2.0 carrying line with the Hand-GAL4 driver, which enables the heart-specific expression of the opsins in Drosophila. Here we demonstrated the feasibility of increasing the heart rate of live Drosophila animals following 470nm blue light pulses and inducing restorable heart arrest caused by 617nm red light illumination in the same specimen. Irradiance and illumination schedule were optimized to achieve successful pacing of Drosophila models at different developmental stages. This optogenetic system allows non-invasive modeling of different heart arrhythmia disorders in Drosophila.
Jianmin Cui, Hong Chen