Nevada-based molecular biologist Monika Gulia-Nuss is using her expertise on how ticks reproduce to figure out how to prevent the creatures from harming cattle herds.
A Fulbright U.S. Scholar Award is backing her research, which involves challenges, such as trying to figure out how to get wax off tick eggs.
“I have been working on black-legged ticks or deer ticks, which transmit the bacteria that causes Lyme disease, for several years now. One of the roadblocks for doing genetic research in ticks was that we were not able to inject tick embryos, which is really the basis of any genetic work in any animal,” she said.
Around two years ago, Gulia-Nuss, her research team and her husband Andrew Nuss were “able to show that the tick embryos can be injected. That opened up a lot of work that we could do in genetic research,” she said.
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“It really made the basis for my Fulbright application as well. So we have been working on the black-legged tick for several years.”
She said she wants to transfer these same embryo injection tricks over to cattle ticks, as cattle ticks cause major losses to the industry.
It’s the genes
“About last year, some of the folks from INIA Institute, which is the National Institute for Agricultural Research in Uruguay, reached out to me, as the government wanted to start a new program for genetic control of ticks. We talked about some of the work we could do to help the cattle tick research. So, I applied for the Fulbright Award to start that work in Uruguay and I was funded,” she said.
“As I said, the ability to inject embryos is really the basis for any genome editing technologies that we have for other animals like mice, mosquitoes and fruit flies. So when we were able to inject the embryos, our next question was, ‘can we modify the genome?’”
There are.
“There are several ways people modify genomes,” Gulia-Nuss noted. “One of the technologies, which is really taking over the previous technologies, is called CRISPR-Cas9. Also, you might have heard a common term called ‘molecular scissors.’ This provides the ability to make a break in DNA wherever we want, and then the cell tries to fix that break and this usually leads to mutations. And mutations allow us to understand how this gene functions because once the gene is mutated, it doesn’t function the same way as a normal gene.
“What we’ve been trying to do with ticks is understand gene functions, so we can identify genes that are really important for tick survival, ticks feeding on the host or ticks passing those pathogens from one host to another host,” she said. “If we can identify some of these target genes, then we can use them to develop either acaricides to kill ticks or we can make vaccines for cattle.”
The vaccines make ticks unable to successfully feed on the cattle, controlling their population as a result, she said.
“The third method that we are also trying to develop is called gene drives, which is a method that has been developed in mosquitoes where we can propagate a gene that is harmful for the ticks and the population. That way, the ticks that are carrying that gene will die off. We can suppress the population. It opens up the opportunity for many different research areas to understand the biology of ticks way better than they were able to,” Gulia-Nuss explained.
Trip to Uruguay
In June, Gulia-Nuss and research scientist Michael Pham will visit Uruguay, with funding from INIA Institute. “They wanted us to come and set up a laboratory so that when I go back next year for my Fulbright Fellowship, they will have everything in place. During this trip, we will be accomplishing two main goals. One is to set up all the equipment that we need for embryo injections,” she said.
“These eggs are very little, so we need microscopes and microinjectors to be able to inject them,” Gulia-Nuss explained. In addition to the injection equipment, she said she is also looking forward to setting up a cattle tick colony. She said she hopes to show the researchers “how to maintain a colony in the lab, so they can have a couple of different generations before I go back in February,” for her three-month tenure supported by the Fulbright award.
The cattle ticks used for the research are endemic to Uruguay, Gulia-Nuss said. Thus, the experimentation will not spread any invasive species from out of the country.
“The cattle industry as a whole is one of the most important industries for Uruguay, since they have more cattle than humans in that country,” Gulia-Nuss said. “The cattle tick is a huge pest that leads to millions of dollars of loss every year. So the government is really committed to developing tools for controlling the population of the ticks so that the cattle industry can flourish better. It was actually through support of the government that my collaborators reached out to us to develop these tools for cattle ticks.”
Decades of intense study and research brought Gulia-Nuss to this point. Her understanding of tick biology took time and commitment to build. A trained mosquito researcher, she has been researching the insects since her 1999 master’s program at Maharshi Dayanand University in India.
“I switched to ticks about 10 years ago … since my husband and I both work on insects. He got a position at Purdue University and I was looking for a relevant position and the opening was in tick research,” Gulia-Nuss said.
“When I started working on ticks, I found them very fascinating organisms, because we had very little understanding of tick biology. There were so many questions that I would ask and that answer would most likely be ‘we don’t know.’ So when I started my lab at UNR, my focus was to develop genetic tools for ticks so we could start understanding the gene functions,” she said.
“The first grant was really difficult to get because most reviewers would just say, ‘You can never inject tick embryos, it’s impossible.’ So we had to really work hard to bring a lot of my expertise from mosquito genetic control work to ticks and show that yes, tick embryos could be injected. Once we were able to develop those tools, our viewers and the research community realized, ‘okay, this is doable, so we must develop more tools.’”
“I’m really excited now that a lot more people are working on tick biology because of the tools that we have developed. People feel comfortable working on this organism. There are many technical hurdles of course, because ticks have about two-year-long life cycles, which makes it really difficult to do many of these modification experiments,” Gulia-Nuss explained.
However, thanks to the temperature- and humidity-controlled environment of a laboratory, Gulia-Nuss and her team were able to bring the ticks’ life cycles down to six months.
Ticks’ biological functions provide their own challenge, she added. “The mother kick puts wax on top of eggs, and in nature that is to avoid desiccation or drying out of the eggs, because these eggs are going to be in the soil for a long time before they hatch out.” The molecular biologists found it difficult to inject wax-covered eggs, Gulia-Nuss explained.
“We had to somehow remove that wax. It took us several months, almost a year, because we tried different things like organic solvents, detergents, etc. to remove the wax. All of these things worked but they also killed the embryo,” she noted. “The breakthrough was when we dissected out a gland that makes wax from the mother tick when she is laying eggs. It allowed us to get the eggs that have very little wax on them. And since we were keeping these eggs in very humid conditions, they would avoid drying out. So that really helped us a lot.
“Once we were able to do all these modifications, and were able to inject the eggs, everything else was less stressful or less complicated at least, because the techniques like CRISPR-Cas9 are relatively standard,” she said.
The research process led to some technological and biological revelations, Gulia-Nuss noted.
“Many times when we think about all bugs in general,” including ticks, “we think about drosophila melanogaster, the fruit fly, which is a model organism,” she said. “Pretty much everything is based on that model organism — where to inject the eggs and how to inject the eggs. For fruit fly research, which is also similar in mosquitoes because they’re both flies, the egg will have an anterior and posterior,” she noted. “If you’re looking at a chicken egg, there is a pointed end and a wider end, right? The wider end is the posterior. That’s where we inject, because that’s where the future gonads, the ovaries and testes, are going to form.”
Unlike chickens and fruit flies, ticks have rounded, sphere-shaped eggs, she said, so “they don’t have the anterior and posterior up until late in the development.”
“Whatever we know about fruit fly research is not directly applicable to ticks. So we had to learn everything from scratch. We had to develop our own embryo development stages for ticks,” she said.
Gulia-Nuss explained why she decided to come to Nevada. “My spouse and I are both medical entomologists and we were looking for positions together,” she said. They came to UNR in 2016, when it was hiring several new faculty members.
“They were able to offer both of us tenure track positions,” she said, with Nuss becoming an associate professor in Agriculture, Veterinary and Rangeland Sciences and Gulia-Nuss becoming an associate professor and graduate program director in the University of Nevada, Reno’s Department of Biochemistry and Molecular Biology.
Gulia-Nuss said she appreciated joining her department because it was the former home of biochemist, endocrinologist and insect researcher David Schooley. “Dave was kind of my science hero because he worked on insect neuropeptides for a long time. We both knew his work and we were very excited to be in the same university where Dave was.”
What would Gulia-Nuss like the public to understand?
“Tick research is very exciting and there’s a lot of push all over the world to study ticks much better,” she said. “At UNR, we have made the genetic work possible in ticks. We pioneered these techniques. But we still struggle with the infrastructure. So I would really emphasize that more infrastructure is needed for doing research.”