Optogenetics

is a technique whereby excitable cells,

such as neurons,

can be controlled at will

by light.

To do this,

cells are genetically engineered

to produce ion channels

called opsins

that sit in the cells'

membranes

and open

in response

to a certain wavelength of light.

In classic optogenetics, scientists implant optical fibers near opsin-dotted neurons to deliver the light stimulation. Computer-programmed light pulses can then target these newly light-sensitive neurons in a particular region of the brain and control their activity like puppets on a string.

Despite efforts to visualize the spatio–temporal dynamics of single messenger RNAs, the ability to precisely control their function has lagged. This study presents an optogenetic approach for manipulating the localization and translation of specific mRNAs by trapping them in clusters.

This clustering greatly amplified reporter signals, enabling endogenous RNA–protein interactions to be clearly visualized in single cells.

Functionally, this sequestration reduced the ability of mRNAs to access ribosomes, markedly attenuating protein synthesis. A spatio–temporally resolved analysis indicated that sequestration of endogenous β-actin mRNA attenuated cell motility through the regulation of focal-adhesion dynamics.

These results suggest a mechanism highlighting the indispensable role of newly synthesized β-actin protein for efficient cell migration. This platform may be broadly applicable for use in investigating the spatio–temporal activities of specific mRNAs in various biological processes.

https://www.biorxiv.org/co...

There has been an extensive body of research aimed at developing optogenetic tools to regulate gene expression. In a common strategy, a light-sensitive protecting group (‘photo-cage’) is chemically installed on a biologically relevant target (e.g. metabolites, oligonucleotides, or proteins) rendering the substrate inactive. Subsequently, light irradiation triggers the release of the ‘photo-cage’ from the target biological molecule, restoring its cellular activity.

8-10] For instance, optogenetic approaches often involve the installation of light-responsive protein domains or amino acids to achieve photo-chemical manipulation of proteins such as nucleases, proteases and transcription factors. [11-16] Caged oligonucleotides have also been used to control gene expression at the level of transcription or translation.

[17-24] By conjugating ‘photo-cages’ onto nucleotide bases, hybridization between the antisense oligonucleotide and the target DNA/RNA can be controlled precisely using light. While most studies have focused on optogenetic control of transcription, there are advantages to methods that optically control gene expression at the level of translation.

[25-29, 41] Since mRNA can be processed by cellular translation machinery immediately upon cytoplasm entry, controlling gene expression through direct manipulation of mRNA provides more rapid changes in cellular protein concentration compared to the regulation of transcription. [30] Moreover, in-vitro transcribed mRNA (IVT-mRNA) is only transiently active in cytosol and is completely degraded via cellular metabolism, typically within 24 hours.

Thus, unlike the use of plasmid DNA or viral vectors which may be integrated into the cellular genome, mRNA-based gene expression regulation systems do not pose the risk of insertional mutagenesis. [31] Thus, a technique that enables optogenetic manipulation of translation would benefit from the high spatial-temporal resolution inherent to optical control as well as fast dynamics of mRNA processing.