UMMS scientists develop multicolored labeling system to track genomic locations in live cells
“Most people are using CRISPR for editing genomes. We are using it to label DNA and track the movement of DNA in live cells,” said research specialist Hanhui Ma, PhD, who coauthored the study with Thoru Pederson, PhD, the Vitold Arnett professor of cell biology and professor of biochemistry and molecular pharmacology.
Knowing the precise location of genomic elements in live cells is critical to understanding chromosome dynamics because the genes that control our biology and health do so according to their location in 3-dimensional space, said Drs. Pederson and Ma. For a gene to be transcribed and expressed, it must be accessible on the chromosome. Where DNA is positioned in the crowded nucleus plays an important role in everything from embryonic development to cancer.
Current technologies, however, are only capable of following, at most, three genomic locations at a time in live cells. Labeling more sites requires that cells be fixed by bathing them in formaldehyde, thus killing them and making it impossible to observe how the chromosome’s structure changes over time or in response to stimuli.
To overcome this technological hurdle, Pederson and Ma turned to CRISPR/Cas9. To tag specific locations along the genome using the CRISPR/Cas9 complex, they created a Cas9 mutation that makes the nuclease inactive so it only binds to the DNA and doesn’t cut the genome. Once deactivated, the CRISPR/Cas9 element is ferried to a specific location on the genome by a guide RNA that can be programmed by the researchers.