Controlling Gene Editing With Light

The gene editing platform CRISPR can be modified to be activated with light, enabling more precise study and action

Developing ways to improve accuracy and control in gene editing techniques is essential for both safe therapies and research. Research at MIT is now building on previous work on controlling RNA interference with light; tweaking CRISPR to be ultraviolet light responsive. 

How was CRISPR altered?

CRISPR-Cas9 in its classical form consists of an RNA guiding strand that matches with a section of DNA, attached to Cas9 which is a nuclease (meaning it snips DNA). Other teams have modified the Cas9 enzyme in the past, so that it only cuts when it's exposed to certain wavelengths of light. This time the team made the initial RNA binding light sensitive - meaning the guiding strand could only lock on under certain UV wavelengths. 

“The advantage of adding switches of any kind is to give precise control over activation in space or time, You really don’t have to do anything different with the cargo you were planning to deliver except to add the light-activated protector. It’s an attempt to make the system much more modular”

Blocking initial binding

To do this, the scientists attached a sequence of DNA to the guiding RNA strand like a cover; a sequence that would break in response to UV light and release the RNA guiding strand. Once this protective sequence was dispersed the strand is free to bind and 'edit' the genome. The method was tested on a gene for green fluorescent protein (GFP) and two other proteins with success. 

“If this is really a generalizable scheme, then you should be able to design protector sequences against different target sequences. We designed protectors against different genes and showed that they all could be light-activated in this way. And in a multiplexed experiment, when a mixed population of protectors was used, the only targets that were cleaved after light exposure were those being photo-protected”

This method enables more finesse and control when it comes to experiments, and could assist researchers in studying gene expression in a more controlled manner. It also has medical applications however, with the potential to target cancerous genes in the skin - an organ frequently exposed to UV light. 

Read more at MIT News