In a world’s first, researchers at the University of Bonn in Germany made a skeletal muscle of a mouse contract in response to light. The team introduced a gene into a mouse that codes for a protein normally produced by light sensing blue-green algae. The protein controls algae motion when light strikes it, but by producing it within the mouse’s own cells, it has the same effect of contracting muscle cells when illuminated by light. The researchers specifically focused on the larynx that they removed from the mouse so that light can be delivered correctly.
The hope is that this new application of optogenetics to voluntary muscles will help in medical research, particularly for new therapies to combat motor neuron disease.
From the study abstract in Nature Communications:
Here we show direct optogenetic stimulation of skeletal muscle from transgenic mice expressing the light-sensitive channel Channelrhodopsin-2 (ChR2). Largest tetanic contractions are observed with 5-ms light pulses at 30 Hz, resulting in 84% of the maximal force induced by electrical stimulation. We demonstrate the utility of this approach by selectively stimulating with a light guide individual intralaryngeal muscles in explanted larynges from ChR2-transgenic mice, which enables selective opening and closing of the vocal cords. Furthermore, systemic injection of adeno-associated virus into wild-type mice provides sufficient ChR2 expression for optogenetic opening of the vocal cords. Thus, direct optogenetic stimulation of skeletal muscle generates large force and provides the distinct advantage of localized and cell-type-specific activation.
Here’s a video of a mouse larynx being opened and closed in response to light:
Study in Nature Communications: Optogenetic control of contractile function in skeletal muscle…
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