Ticks won’t be able to conceal their fiendish tricks much longer. In new research this week, researchers claim to have genetically modified tick embryos in the lab using CRISPR — an apparent first in the field. The achievement should one day allow us to better understand these bugs, especially those responsible for Lyme disease and other tickborne illnesses.
CRISPR is one of the most important scientific advances of recent times. It’s a relatively cheap, straightforward form of genetic manipulation, derived from an ancient defence system used by bacteria to ward off viruses. Humans are starting to use CRISPR to get rid of troublesome mutations or to add new genetic changes in animals and plants, which could have a wide range of applications in both medicine and agriculture. Another valuable application of CRISPR is simple knowledge. By knocking out a gene in a living thing, for instance, you might be able to figure out what that gene actually does and unlock a piece of the biology puzzle.
One common way to edit something’s genes is to carefully introduce the changes while they’re in the embryo stage of life. Scientists have done this on various disease-spreading arachnids and insects, such as mosquitos. But tick embryos are apparently very finicky, according to the researchers behind this new study, published Tuesday in iScience. The insides of their eggs are highly pressurised, and they’re coated by a hard outer shell as well as a thick layer of wax-like material applied by the female tick. This wax layer had made gene-editing an impossible task — until now, it seems.
“We were able to carefully dissect gravid female ticks to surgically remove the organ responsible for coating the eggs with wax, but still allowing the females to lay viable eggs. These wax-free eggs permitted injection of tick embryos with materials necessary for genome modification,” said senior author Monika Gulia-Nuss, a molecular biologist at the University of Nevada, Reno, in a statement.
Gulia-Nuss and her team, which also involved researchers from Pennsylvania State University and the University of Maryland, worked with the black-legged tick (Ixodes scapularis), the primary vector of Lyme disease along with other nasty infections. They had several challenges to figure out, such as the timeline of tick development inside the embryo. But once they did, they were able to produce a surviving batch of CRISPR-injected ticks.
Overall, about 10% of these ticks survived the process, comparable to rates seen in other bug models. Reportedly for the first time in arachnids, they were also able to perform a relatively new method of delivering CRISPR, one that doesn’t require any embryo injections, called the ReMOT Control technique. This method has the changes added to the adults before they conceive, and it proved to be 100% survivable in their ticks.
These firsts, the researchers said, should go a long way toward unravelling the genetic and molecular secrets of ticks and their complex life cycle. And down the road, this research just might lead to new weapons against the diseases they spread. Ticks are the leading cause of vector-borne illness in the U.S., with hundreds of thousands of Americans catching Lyme every year. And thanks largely to climate change, they’re threatening to become an even larger nuisance in the decades to come.
“We expect that the tools we developed here will open new research avenues that will dramatically accelerate our understanding of the molecular biology of this and related tick species,” Gulia-Nuss said. “Targeted disruption of genes in tick vectors of human pathogens is a powerful method to uncover the underlying biology of tick-pathogen-host interactions that can inform the development and application of new approaches to tick-borne disease control.”