Sonogenetic control of mammalian cells using exogenous Transient Receptor Potential A1 channels

Abstract

Our understanding of the nervous system has been fundamentally advanced by light- and small molecule-sensitive proteins that can be used to modify neuronal excitability. However, optogenetics requires invasive instrumentation while chemogenetics lacks temporal control. Here, we identify a candidate channel that confers sensitivity to non-invasive ultrasound on millisecond timescales. Using a functional screen, we find that human Transient Receptor Potential A1 (hsTRPA1) increases ultrasound-evoked intracellular calcium levels and membrane potentials. Ultrasound, but not agonist, -evoked, gating of hsTRPA1, requires the N-terminal tip region, intact actin cytoskeleton, and cholesterol, implicating these features in the sonogenetic mechanism. We then use calcium imaging and electrophysiology to confirm that ultrasound-evoked responses of primary neurons are potentiated by hsTRPA1. We also show that unilateral expression of hsTRPA1 in mouse layer V motor cortical neurons leads to ultrasound-evoked contralateral limb responses to ultrasound delivered through an intact skull. Finally, ultrasound induces c-fos in hsTRPA1-expressing neurons, suggesting that our approach can be used for targeted activation of neural circuits. Together, our results demonstrate that hsTRPA1-based sonogenetics can effectively and non-invasively modulate neurons within the intact mammalian brain, a method that could be extended to other cell types across species.

Ultrasound Mediated Cellular Deflection Results in Cellular Depolarization

“…These data suggest that we are unlikely to cause cavitation and cell viability remains unaffected as shown by prior work with similar stimulus parameters. [ 18 ]…”

“…It is noninvasive and has a high spatiotemporal resolution (<1 mm and <1 ms) in comparison to existing techniques. Improvements in the spatial resolution through transfection of mechanosensitive proteins currently come at the cost of a minimally‐invasive procedure to directly inject the vector into the target tissue, [ 18 ] though there may soon be non‐invasive alternatives. [ 19 ] The spatial resolution of ultrasound is governed by the wavelength of operation and is about 1.5 mm at 1 MHz in tissue.…”

Ultrasound mediated cellular deflection results in cellular depolarization

“…It is non-invasive and has a high spatiotemporal resolution. Improvements in the spatial resolution through transfection currently come at the cost of a minimally-invasive procedure to directly inject the vector into the target tissue [18], though there may soon be non-invasive alternatives [19]. The spatial resolution of ultrasound is governed by the wavelength of operation and is about 1.5 mm at 1 MHz in tissue.…”

Microscale concert hall acoustics to produce uniform ultrasound stimulation for targeted sonogenetics in hsTRPA1-transfected cells

“…Sonogenetics relies on genetically engineering cells to be more sensitive to mechanical stimuli using membrane bound proteins 20,21 . This technique eliminates the need for focused ultrasound by ensuring that targeted neural circuits are the only ones that will respond to an ultrasound stimulus.…”

“…This technique eliminates the need for focused ultrasound by ensuring that targeted neural circuits are the only ones that will respond to an ultrasound stimulus. Recent work has revealed that one protein in particular, human transient receptor potential A1 (hsTRPA1), produces ultrasound-evoked responses in several cell types 21 . One limitation of sonogenetics is that existing transducers producing planar or focused ultrasound are unsuitable .…”