An inexpensive programmable optogenetic platform for controlled neuronal activation regimens in C. elegans

Abstract

In Caenorhabditis elegans, optogenetic stimulation has been widely used to assess neuronal function, control animal movement, or assay circuit responses to controlled stimuli. Most studies are performed on single animals and require high-end components such as lasers and shutters. We present an accessible platform that enables controlled optogenetic stimulation of C. elegans in two modes: single animal stimulation with locomotion tracking and entire population stimulation for neuronal exercise regimens. The system consists of accessible electronic components: a high-power light-emitting diode, Arduino board, and relay are integrated with MATLAB to enable programmable optogenetic stimulation regimens. This system provides flexibility in optogenetic stimulation in freely moving animals while providing quantitative information of optogenetic-driven locomotion responses. We show the applicability of this platform in single animals by stimulation of cholinergic motor neurons in C. elegans and quantitative assessment of contractile responses. In addition, we tested synaptic plasticity by coupling the entire-population stimulation mode with measurements of synaptic strength using an aldicarb assay, where clear changes in synaptic strength were observed after regimens of neuronal exercise. This platform is composed of inexpensive components, while providing the illumination strength of high-end systems, which require expensive lasers, shutters, or automated stages. This platform requires no moving parts but provides flexibility in stimulation regimens.

Optogenetic manipulation of individual or whole populationCaenorhabditis elegansworms with an under hundred-dollar tool: the OptoArm

“…Clearly, this labor-intensive scoring method is vulnerable to inconsistency and experimenter bias and becomes impractical when scoring many worms and conditions. There are Matlab codes available to automate and streamline these measurements (Liewald et al, 2008; Crawford et al, 2020), but these codes also require a basic understanding of programming languages and access to Matlab. Based on the idea that the OptoArm should be a simple system that is accessible to the whole community, we aimed to simplify the accompanying analysis for ‘Δ body length’, i.e.…”

“…Moreover, it is practically impossible to generate the short-pulses or even high frequency trains required for certain experiments through manual operation (Liewald et al, 2008;Crawford et al, 2020). Therefore, we explored the use of a microcontroller to circumvent the use of a computer and to provide a low-cost solution to the aforementioned problems.…”

“…Several researchers have tried to make optogenetical experiments more accessible to a wide audience by successfully developing inexpensive (<1500 dollars) optogenetic systems (Pulver et al, 2011; Kawazoe et al, 2013; Rabinowitch et al, 2016b; Pokala et al, 2018; Crawford et al, 2020). Some of these low-cost systems even allow multiple worms to be illuminated at the same time (Kawazoe et al, 2013; Crawford et al, 2020).…”

“…Several researchers have tried to make optogenetical experiments more accessible to a wide audience by successfully developing inexpensive (<1500 dollars) optogenetic systems (Pulver et al, 2011; Kawazoe et al, 2013; Rabinowitch et al, 2016b; Pokala et al, 2018; Crawford et al, 2020). Some of these low-cost systems even allow multiple worms to be illuminated at the same time (Kawazoe et al, 2013; Crawford et al, 2020). When considering the current developments of automated worm trackers (Tsibidis et al, 2007; Ramot et al, 2008b; Swierczek et al, 2011; Stirman et al, 2011; Leifer et al, 2011; Wang et al, 2013; Kwon et al, 2013; Restif et al, 2014; Javer et al, 2018; Perni et al, 2018; Koopman et al, 2020), the ability to illuminate multiple worms at the same time during tracking offers a clear benefit for studying both population and single-worm characteristics.…”

“…In fact, most of the systems require manual adaptations (e.g., aluminum foil, closed boxes) to ensure a light intensity that is high enough (e.g. 1.6 mW/mm 2 , or at least 1.0 mW/mm 2 ) for optogenetic purposes in C. elegans (Rabinowitch et al, 2016b; Crawford et al, 2020). These adaptations make the simultaneous tracking of illuminated worms challenging and highly reduce the adaptability of the system to other experimental set-ups.…”