From opto- to radio-genetics: A switch in the wavelength.

The use of ion channels to control defined events in defined cell types at defined times in the context of living tissue or whole organism represent one of the major advance of the last decade, and optogenetics (i.e the combination of genetic and optical methods) obviously played a key role in this achievement.(1) Although the existence of light-activated ion channels (i.e ospin channels) has been known since 1971,(2) it took about 35 y before the concept of an ion channel used for bioengineering control of cell or tissue activity becomes reality.(3) From that moment forward, rhodopsine channels(4) (,) (5) (i.e blue light-gated non-specific Na(+) channels that depolarize cells thus increasing cell excitability) or halorhodopsin channels(6) (i.e yellow light-gated Cl(-) channels that hyperpolarize cells thus decreasing cell excitability) have been extensively used to turn neurons on and off in response to diverse colors of light, with an extremely high temporal precision (i.e milliseconds range). Although optogenetics has been originally established in neuroscience, it addresses now to non-neuronal systems, including cardiac, smooth and skeletal muscles, glial cells or even embryonic stem cells.(7) (-) (9) However, although light stimulation allows control of cell excitability with a high spatio-temporal specificity, light waves present the disadvantage to not penetrate deep tissue, and implanted devices are required for in vivo light stimulation. In contrast to visible light-waves, radio-waves (i.e longer wavelength and lower frequency) can penetrate deep tissues with minimal energy absorption.