World's first genome editing tool for ticks

Black-footed ticks, also known as grass reptiles, (Arthropoda, Arachnida, Ticks, Tick family, about 800 species have been found in the world, 110 species have been recorded in China) to transmit Lyme disease, this disease generally does not The dead were discovered not long ago, but they developed rapidly and became an epidemic in almost every continent of the world
.

Not only can they bite the skin to suck blood, but they are also vectors of spirochete, rickettsial, viral, and bacterial infections

"Despite their ability to acquire and deliver a range of disabling pathogens, ticks have been lagging behind other arthropod vectors such as mosquitoes, largely because of challenges in applying existing genetic and molecular tools
.

" said study co-senior author Monika Gulia-Nuss, a molecular biologist at the University of Nevada, Reno

Now researchers have successfully edited the genome of the black-footed tick using CRISPR-Cas9
.

To accomplish this feat, they developed an embryo injection protocol that overcomes a major hurdle in the field

"Gene editing tools will allow us to unlock some of the secrets of the tick genome and allow us to determine the environment in which these unique animals live, how they interact with pathogens, and how to prevent the spread of disease to humans and livestock," Gulia-Nuss said
.

Ticks are vectors of multiple pathogens in humans, wildlife, and domestic animals, and despite public health relevance, knowledge of tick biology at the molecular level remains limited
.

This is in stark contrast to insects such as mosquitoes, for which an abundance of transgenic and genome editing tools are already available

CRISPR-Cas9 has revolutionized the study of functional genetics in many organisms
.

This gene editing technique has been applied to mosquitoes and other arthropod disease vectors, but no successful gene editing has been reported in ticks

In the iScience study, researchers developed a successful tick embryo injection protocol and targeted gene disruption using CRISPR-Cas9 using two approaches: embryo injection and receptor-mediated ovarian cargo transduction ( ReMOT Control) - a less labor-intensive approach to gene editing in arthropods
.

The researchers removed the organ of Gibbs to prevent wax deposition, and then treated the eggs with chemicals called benzalkonium chloride and sodium chloride to remove the chorion and reduce the pressure inside the eggs

"We were able to carefully dissect pregnant female ticks, surgically removing the organs responsible for waxing the eggs, but still allow the female tick to lay eggs
.

These wax-free eggs allow the tick embryos to be injected with materials needed for genome modification, "Gulia-Nuss said

The survival rate of injected embryos is about 10%, which is comparable to that of mature insect models
.

In ReMOT Control, all injected ticks survived

"Previously, no laboratory has demonstrated that genome modification is possible in ticks
.
Some people thought it was too technically difficult to achieve," Nuss said
.
"This is the first study to show that genetic transformation in ticks may be achieved by one, but two, different approaches
.
"

More research is needed to fully understand the molecular mechanisms underlying efficient gene editing in ticks
.
While these tools will accelerate tick genetic research, improvements in embryo injection protocols are still needed to improve survival, larval hatching, and gene editing efficiency
.

Gulia-Nuss said: "We hope that the tools we have developed here will open new avenues of research and greatly accelerate our understanding of the molecular biology of this tick and its related species
.
Tick vectors for targeted disruption of human pathogens , is a powerful approach to uncover the underlying biology of tick-pathogen-host interactions, which can inform the development and application of new approaches to tick-borne disease control
.
"

Several co-authors have applied for patent protection on the ReMOT Control technology
.

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Cas9-mediated gene editing in the black-legged tick, Ixodes scapularis, by embryo injection and ReMOT Control