CRISPR Cas9: Genome editing system controlled by light read more at here www.spinonews.com/index.php/item/695-crispr-cas9-genome-editing-system-controlled-by-light

Genome editing system known as CRISPR is a type of genetic engineering in which DNA is inserted, deleted or replaced in the genome of any living cell.

Now, MIT Researchers have added an extra layer of control over when and where this gene editing occurs, by making the system responsive to light. With the new system, gene editing takes place only when researchers shine ultraviolet light on the target cells.

CRISPR relies a gene-editing tool composed of a DNA-cutting enzyme called CRISPR-Cas9, and a short RNA guides the enzyme to a specific area of the genome, directing Cas9 where to make its cut.

When Cas9 and the guide RNA are delivered into cells, a specific cut is made in the genome. The cell’s DNA repair processes glue the cut back together but permanently delete a small portion of the gene, making it unusable.

Sangeeta Bhatia professor of Health Sciences and Electrical Engineering and Computer Science at MIT says, previously researchers have altered the Cas9 enzyme for cutting when exposed to certain wavelengths of light.

MIT team take a different approach to make the binding of the RNA guide strand light-sensitive. For possible future applications in humans, it could be easier to deliver these modified RNA guide strands than to program the target cells to produce light-sensitive Cas9.

To make the RNA guide strands light-sensitive, MIT team created protectors consisting of DNA sequences with light-cleavable bonds along their backbones. These DNA strands can be tailored to bind to different RNA guide sequences, forming a complex that prevents the guide strand from attaching to its target in the genome.

When researchers expose the target cells to light with a wavelength of 365 nanometers in the ultraviolet range, the protector DNA breaks into several smaller segments and falls off the RNA, allowing the RNA to bind to its target gene and recruit Cas9 to cut it.

In this study, researchers demonstrated using light, to control editing of the gene for green fluorescent protein (GFP) and two genes for proteins normally found on cell surfaces and expressed in some cancers.

CRISPR-Cas9 is a powerful gene editing technology that scientists can use to study how genes affect cell behavior. This important advance will enable precise control over those genetic changes. As a result, this work gives the scientific community a very useful tool to advance many gene editing studies.