This CRISPR Moment
Editing human DNA the way we edit text — are we ready?
It reads like an all-caps typo from the technical manual that comes taped to the side of a new refrigerator. But CRISPR is going to change your world. It may even — quite literally — change the face of humanity.
Since its discovery four years ago, the gene-editing system known as “clustered regularly interspaced short palindromic repeats” has been used by scientists to make precise alterations in the DNA sequences of living cells. It offers the prospect of treating (and perhaps even eradicating) debilitating genetic conditions, improving fertility treatments, fighting cancer, and allowing the safe transplantation of tissues and organs between species.
Hemophilia, sickle-cell anemia, and muscular dystrophy are just three of the diseases that could eventually become treatable thanks to therapies developed through CRISPR. In late 2015, for instance, three groups of scientists reported that they could infect muscle cells in living Duchenne muscular dystrophic mice with a virus carrying the CRISPR/CAS9 editing cassette. (The latter alphanumeric term refers to a CRISPR system that employs the Cas9 protein.) The researchers then edited the defective dystrophin gene in enough cells to improve muscle function.
On the other hand, CRISPR also raises the spectre of a Gattaca- style bioethical dystopia. The technology, some warn, might open the door to large-scale bioterrorism or monstrous, genetically altered human variants. Using CRISPR/CAS9, scientists can make precise genetic alterations to early-stage embryos that are precursors of all the cells contained in a human body. Crucially, this includes the eggs and sperm. Alterations to these “germ cells” are heritable, meaning they will carry over into succeeding generations. This is commonly referred to as “germ-line gene editing.” So far, lines of genetically altered plants, flies, fish, mice, and even monkeys have been produced using such gene-editing techniques.
The clustered regularly interspaced short palindromic repeats employed by CRISPR are genetic sequences that were first discovered in bacteria some twenty years ago. A clever series of experiments and DNA detective work in the early part of this century led to the discovery that CRISPRS carry bits of viral DNA — and use copies of this sequence to recognize and target any invading virus with an enzyme (typically Cas9) that cuts up and destroys viral invaders.
Interestingly, many of the early advances in this technology took place in the yoghurt industry, where scientists were looking to get rid of viral infections in the