By Jonny Lupsha, Wondrium Staff Writer
A medical technology called CRISPR is revolutionizing disease treatment. It can edit genes to treat everything from Tay-Sachs disease to sickle-cell anemia, and more. How does CRISPR work?
The gene-editing tool CRISPR has made big headlines in recent years. CRISPR, which stands for clustered regularly interspaced short palindromic repeats, is a newly developed technology that extracts cells from a patient’s body, genetically edits them to fix whatever’s wrong with the patient, then reinserts the cells into the body. CRISPR is also being researched to treat genetic disorders, make foods more resistant to drought and pests, check children for genetic diseases, and change the coding in cells to alter the human body’s insulin production.
How does CRISPR edit genes? In his video series Synthetic Biology: Life’s Extraordinary New Worlds, Dr. Milton Muldrow Jr., Director of Natural Sciences at Wilmington University, provides background and context to this groundbreaking technology.
What Are Cas Genes?
“Scientists found that in some bacterial cells, there were clusters of repeated sequences of DNA,” Dr. Muldrow said. “The repeated sequences were palindromic, meaning the letters of the genetic code within these segments read the same in both directions of complementary strands. These clusters of repeated palindromic sequences were interrupted by sequences of unknown DNA, so here you had repeated palindromes interspaced with novel DNA.”
These repeats were also bordered by CRISPR-associated genes known as Cas genes for short. Cas genes code for two things: nucleases and helicases. Nucleases are proteins that cut DNA while helicases are proteins that unwind DNA. Scientists soon learned that bacterial cells used the CRISPR system to deploy RNA and its nucleases to recognize viral strains that had infected the bacterial cell and cut them, thereby, inactivating the virus.
“Scientists were not just observing a bacterial immune system, but an immune system that had an adaptive immunity—more sophisticated than scientists had known existed for bacterial cells,” Dr. Muldrow said. “Adaptive immunity involves the detection, identification, and memorization of foreign invaders, or pathogens.”
Subsequent infections by the same agent can cause a system to mount a more effective attack against the pathogen, which is how vaccines work.
What Are the Basics of CRISPR?
According to Dr. Muldrow, CRISPR is based on three distinct features: Cas genes (such as Cas9), which code for proteins that cut DNA; programmable RNA that targets specific genes or gene sequences; and DNA molecules added to the system that implant a beneficial or desired gene into the host cell.
“The Cas9 system normally cuts the DNA of foreign viruses, but scientists hijacked this system to target cells of their own choosing,” he said. “Cas9 is the first protein associated with the CRISPR-Cas system that could be domesticated, so to speak, to do the cutting of DNA on our behalf. Scientists created a technology out of the understanding of basic biology of the CRISPR system in order to cut whatever DNA segments we want.”
CRISPR is still in its infancy, with perils and possibilities science has yet to fully understand. As the scientific community grows into this advancement, legal and ethical questions are bound to arise.
Synthetic Biology: Life’s Extraordinary New Worlds is now available to stream on Wondrium.