CRISPR

The Swiss Army Knife of Genetic Engineering

Clustered Regularly Interspaced Short Palindromic Repeats. Quite a mouthful!  

For decades, researchers have observed a strange sequence of DNA nucleotides at the end of some bacterial genes—which is what the term CRISPR describes. At first they thought this was just junk DNA. However in 2005, it was shown that a part of this odd-looking sequence actually corresponded to a piece of the DNA of certain viruses that can infect these bacteria. Subsequent research showed that this was not junk, but rather an effective defense system of the bacteria against these viruses. The CRISPR part of the genes actually create RNA molecules that in conjunction with a protein called Cas9 cuts up the invading virus DNA and destroys it. (CRISPR is sometimes referred to as CRISPR/Cas9). Cas9 is an enzyme called a nuclease that actually does the cutting. The CRISPR part of the system tells the Cas9 part where to do the cutting.

  Dr. Jennifer Doudna in her lab.    Photo courtesy of the University of California, Berkeley

Dr. Jennifer Doudna in her lab.

Photo courtesy of the University of California, Berkeley

Eureka! It became apparent that if one could change the CRISPR sequence with some DNA editing, one would have a general-purpose tool that could cut any DNA sequence anywhere by using the modified CRISPR to direct the Cas9 enzyme. Jennifer Doudna and Emmanuelle Charpentier demonstrated this in their classic article in Science in 2012.

What followed was a revolution in genetic engineering. Previous to CRISPR, if a researcher wanted to replace a bad gene in an organism, he or she could identify a good gene somewhere, cut it out and splice it into recombinant DNA with a vector and then insert it into cells with the bad gene. The problem was that the scissors used to “cut out” the good gene and splice it into the recombinant DNA was not a simple tool. It was labor intensive, took months to years to make for any given target gene, was expensive, and was subject to error. Other tools included zinc finger nucleases and TALEN (transcription activator-like effector nucleases). 

CRISPR/Cas9 changes all of that. It can be set up cheaply in just a few weeks for virtually any gene. Suddenly, a tool had been found that in less than a year’s time since its discovery was being used in hundreds of different types of organisms for myriads of genetic engineering experiments. Some have called this the Swiss army knife for genetic engineering and gene therapy.

CRISPR/Cas9 is an amazing tool. You can set it up to cut out and splice any gene quickly. You can purchase a kit on-line to do that for $65. Since many genetic disorders are caused by multiple gene mutations, CRISPR/Cas9 can be set up to deal with multiple genes simultaneously. It can be used in somatic cells, stem cells and germline cells. Animal models of human diseases can be created in a matter of weeks rather than months to years required with previous methods. New companies are sprouting up to market commercial uses of CRISPR. Patent wars have already begun over its ownership. The potential uses are limited only by imagination.  CRISPR was named Science Magazine’s 2015 “Breakthrough of the Year."

In February, 2017, the US Patent Office awarded the patent for CRISPR/Cas9 in eukaryotic cells (which includes humans) to the Broad Institute at Harvard and MIT thus, at least temporarily, settling one patent dispute between the Broad Institute and UC Berkeley. The Patent Office ruled that it was the work of Feng Zhang at the Broad Institute that actually demonstrated the ability to adapt CRISPR/Cas9 to plant and animal (including human) cells even though Jennifer Doudna and Emmanuelle Charpentier first published this potential in prokaryotic cells and claimed their discovery applied to any type of cell. The patent fight is not over. In the long run, the importance of resolving this dispute will diminish since a number of alternative similar systems have since been discovered. The race is on to ultimately genetically engineer humans in ways that were unimaginable only a few years ago.

Genetic engineering is one of the four pathways I explore in detail that is relevant to the possible answers.

Click on links to other players in my journey below.