Application Card: Editing Poison Ivy?

Application Card: Editing Poison Ivy?

Why do it• Poison ivy is an irritating plant that causes a painful rash to most people who

make skin contact. According to the American Skin Association, poison ivy and related plants affect as many as 50 million Americans each year. While most people get an irritating rash that subsides within two weeks, the effects can require hospitalization or even be fatal in the 10-15% of the population that is especially sensitive.

• Some scientists are concerned that climate change is making these plants stronger and more widespread. Increased carbon dioxide levels tell the plant to make a stronger version of its irritating chemical and to grow bigger leaves.

Engineering the poison ivy plant• Poison ivy is irritating to people because of a chemical (urushiol, ur-ROO-she-all)

the plant secretes in its sap. The urushiol may help the poison ivy plant to retain water.

• What if scientists could use CRISPR to edit the genome of the poison ivy plant so that the plant no longer made urushiol and would no longer be irritating to the skin?

• The non-irritating poison ivy plant could then be introduced into an area and allowed to interbreed with the wild variety.

Potential concerns• The poison ivy might not thrive enough to change the balance of non-irritating

plants within the population. Other techniques could be used to improve the chances that the engineered genes would persist in the environment, but this could have unintended consequences for biodiversity.

• Although toxic to humans, some animals including deer, bear, rabbits, and many species of birds eat poison ivy, and some bees pollinate the flowers. Organisms that consume or use the poison ivy plant might not use the engineered plant the same way they do the wild variety.

Application Card: Editing the Mosquito?

Application Card: Editing the Mosquito?

Why do it• The Aedes aegypti (AYE‐dees uh‐JIP‐tie) mosquito is the carrier for dengue

(DENG-gay) fever, which the World Health Organization calls the “world’s fastest-growing vector-borne viral disease.” Dengue affects over 50 million people a year, and kills about 25,000. There is no preventative vaccine or specific treatment beyond access to supportive health care to reduce the mortality rate.

• The same mosquito also carries other viruses such as chikungunya and yellow fever.

Engineering the mosquito• In March of 2015, scientists from Rockefeller University published a paper

showing that they were able to use CRISPR to introduce precise, specific changes in the Aedes aegypti mosquito in the laboratory.

• Should we release engineered Aedes aegypti mosquitos to interbreed in the wild? The mosquitos could be engineered so that they didn’t smell human beings as well, or could be less successful at reproduction, or could not carry or transmit dengue. Their offspring would have the same traits, which would eventually reduce the spread of these diseases.

Potential concerns• Many predators eat mosquitos, including bats, birds, and other insects. This

means that the genetic changes could have impacts on other parts of the ecosystem and food web.

• Recent research has shown that engineered mosquitos are less likely to be successful at reproducing in the wild environment than the natural ones are. To maintain a stable population over generations, either more insects need to be released or other genetic techniques may be needed to help ensure that the engineered insect will be successful.

Adapted from “Genome Engineering with CRISPR-Cas9 in the Mosquito Aedes aegypti” (“Kistler et al., 2015, Cell Reports 11, 51–60, April 7, 2015: http://www.cell.com/cell-reports/pdf/S2211-1247(15)00262-4.pdf