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Published on: August 3, 2012
Optogenetic regulation of leg movement in midstage chick embryos through peripheral nerve stimulation
Andrew A Sharp1, Sylvia Fromherz
1Dept. of Anatomy, Southern Illinois Univ. School of Medicine, 1135 Lincoln Dr., Carbondale, IL 62901-6523, USA. asharp@siumed.edu
Insights
Researchers used optogenetics to control embryonic chick leg movement by activating motor axons. This technique offers new insights into how movement and neuronal activity impact sensorimotor development.
Area of Science:
- Developmental Neuroscience
- Neurobiology
- Optogenetics
Background:
- Altered embryonic movement is linked to developmental disorders affecting the nervous system.
- Understanding the generation of embryonic movement and its role in nervous system development is crucial.
- Directly manipulating embryonic movement and neuronal activity for study presents significant challenges.
Purpose of the Study:
- To establish an optogenetics approach for modulating embryonic limb movement in chick embryos.
- To investigate the role of embryonic movement and neuronal activity in sensorimotor development.
Main Methods:
- Utilized electroporation of a transposon-based system to express ChIEF (a channelrhodopsin-2 variant) in the chick embryo lumbosacral spinal cord.
- Enabled stable transgene incorporation for ChIEF protein expression in both central and peripheral nervous system components.
- Visualized ChIEF-expressing motor axons in ovo and used blue light stimulation to elicit or disrupt leg movements.
Main Results:
- ChIEF protein was detected within 24 hours post-electroporation, localized to cell membranes and axonal processes.
- Blue light pulses delivered to the thigh induced stereotyped leg flexures in resting embryos.
- Continuous light illumination interfered with spontaneous leg extension during embryonic development.
Conclusions:
- Successfully demonstrated an optogenetics method to alter peripheral motor axon function in embryonic chicks.
- This approach provides a novel tool to probe the influence of movement and neural activity on sensorimotor development.
- The findings highlight the importance of controlled embryonic movement for normal nervous system development.
Abstract:
Numerous disorders that affect proper development, including the structure and function of the nervous system, are associated with altered embryonic movement. Ongoing challenges are to understand in detail how embryonic movement is generated and to understand better the connection between proper movement and normal nervous system function. Controlled manipulation of embryonic limb movement and neuronal activity to assess short- and long-term outcomes can be difficult. Optogenetics is a powerful new approach to modulate neuronal activity in vivo. In this study, we have used an optogenetics approach to activate peripheral motor axons and thus alter leg motility in the embryonic chick. We used electroporation of a transposon-based expression system to produce ChIEF, a channelrhodopsin-2 variant, in the lumbosacral spinal cord of chick embryos. The transposon-based system allows for stable incorporation of transgenes into the genomic DNA of recipient cells. ChIEF protein is detectable within 24 h of electroporation, largely membrane-localized, and found throughout embryonic development in both central and peripheral processes. The optical clarity of thin embryonic tissue allows detailed innervation patterns of ChIEF-containing motor axons to be visualized in the living embryo in ovo, and pulses of blue light delivered to the thigh can elicit stereotyped flexures of the leg when the embryo is at rest. Continuous illumination can disrupt full extension of the leg during spontaneous movements. Therefore, our results establish an optogenetics approach to alter normal peripheral axon function and to probe the role of movement and neuronal activity in sensorimotor development throughout embryogenesis.
