CRISPR-Cas9 and Nanoclew
CRISPR technology was first derived from a bacterial immune response that uses RNA to protect itself against plasmids and viruses by breaking specific DNA sequences in the pathogen's genome. With the CRISPR technology, researchers have co-opted that system to edit any gene, allowing them to make precise genetic changes for a desired effect.
The gene drive mechanism may allow scientists to control malarial mosquitoes or pesticide-resistant pests, for example, by using CRISPR to introduce a mutation (allele) into a few individuals in a population and have that mutation quickly spread through the entire population. But researchers fear such gene drives could have unintended consequences, such as spreading into an unintended species.
The nanoclews are made of a single, tightly-wound strand of DNA. The DNA is engineered to partially complement the relevant CRISPR RNA it will carry, allowing the CRISPR-Cas9 complex - a CRISPR RNA bound to a Cas9 protein—to loosely attach itself to the nanoclew. "Multiple CRISPR-Cas complexes can be attached to a single nanoclew," says Wujin Sun, lead author of the study and Ph.D. student in Gu's lab.
When the nanoclew comes into contact with a cell, the cell absorbs the nanoclew completely - swallowing it and wrapping it in a protective sheath called an endosome. But the nanoclews are coated with a positively-charged polymer that breaks down the endosome, setting the nanoclew free inside the cell. The CRISPR-Cas9 complexes can then free themselves from the nanoclew to make their way to the nucleus. And once a CRISPR-Cas9 complex reaches the nucleus, gene editing begins.