Abstract
Optogenetics controls neural activity and behavior in living organisms through genetically targetable actuators and light. This method has revolutionized biology and medicine as it allows controlling cells with high temporal and spatial precision. Optogenetics is typically applied only at short time scales, for instance to study specific behaviors. Optogenetically manipulating behavior also gives insights into physiology, as behavior controls systemic physiological processes. For example, arousal and sleep affect aging and health span. To study how behavior controls key physiological processes, behavioral manipulations need to occur at extended time scales. However, methods for long-term optogenetics are scarce and typically require expensive compound microscope setups. Optogenetic experiments can be conducted in many species. Small model animals such as the nematode C. elegans have been instrumental in solving the mechanistic basis of medically important biological processes. We developed the OptoGenBox, an affordable stand-alone and simple-to-use device for long-term optogenetic manipulation of C. elegans. The OptoGenBox provides a controlled environment and is programmable to allow the execution of complex optogenetic manipulations over long experimental times of many days to weeks. To test our device, we investigated how optogenetically increased arousal and optogenetic sleep deprivation affect survival of arrested first larval stage C. elegans. We optogenetically activated the nociceptive ASH sensory neurons using ReaChR, thus triggering an escape response and increase in arousal. In addition, we optogenetically inhibited the sleep neuron RIS using ArchT, a condition known to impair sleep. Both optogenetic manipulations reduced survival. Thus, the OptoGenBox presents an affordable system to study the long-term consequences of optogenetic manipulations of key biological processes in C. elegans and perhaps other small animals.
Highlights
Optogenetics can control many physiological processes by actively influencing biochemical reactions and manipulating neuronal activity (Fenno, Yizhar, & Deisseroth, 2011)
We investigated how optogenetically increased arousal and optogenetic sleep deprivation affect survival of arrested first larval stage C. elegans
Many physiological processes are conserved across species and can be studied in less complex organisms such as the 1mm long nematode C. elegans. 83% of its genes have human homologs, allowing molecular studies that are of relevance to human biology (Lai, Chou, Ch’ang, Liu, & Lin, 2000)
Summary
Optogenetics can control many physiological processes by actively influencing biochemical reactions and manipulating neuronal activity (Fenno, Yizhar, & Deisseroth, 2011). Some of the most-used tools are channel rhodopsins, which have first been discovered in algae (Nagel et al, 2002, 2003), and ion pumps, which were found in halobacteria (Han et al, 2011), both can be genetically expressed in other organisms to depolarize or hyperpolarize cells upon light stimulation. Optogenetics has become widely established in different model organisms, e.g. small nematodes and flies and mammals such as mice and monkeys (Fenno et al, 2011). Many physiological processes are conserved across species and can be studied in less complex organisms such as the 1mm long nematode C. elegans. C. elegans was the first animal in which optogenetics was established (Husson et al, 2013; Nagel et al, 2003)
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