A Crack In Creation: A Nobel Prize Winner's Insight into the Future of Genetic Engineering

by Jennifer A. Doudna

When animal geneticists began using CRISPR, they sought to create gene knockouts that would manifest themselves in obvious ways. One of the favorite targets was a gene called TYR. Having arisen more than half a billion years ago, the TYR gene is widely distributed among animals, plants, and fungi; it produces a protein called tyrosinase that is involved in synthesizing melanin, an important pigment. TYR mutations in humans lead to a deficiency in tyrosinase and cause type I albinism, a genetic condition associated with vision defects, pale skin lacking pigmentation, and red eyes. If CRISPR was programmed to edit the mouse version of the TYR gene, would it cause the mice to have an albino disorder? In 2014, a research team at the University of Texas designed CRISPR to target a twenty-letter DNA sequence in the TYR gene and injected it into fertilized eggs. The resulting births were striking; although all of the mouse pups had normal dark-haired parents, many of the pups were perfectly white-haired and red-eyed. Such a result could only be explained by DNA mutations that had scrambled decryption of the TYR gene. Changing the skin, hair, and eye color of a mouse was about as clear and profound an effect as you could ask for.