Researcher Aims to Update Gene Editing System for Brain Studies

A UT Dallas researcher is taking a new trend in gene editing, called CRISPR/Cas9, and developing ways to make it more flexible and precise for potential use in psychiatric and brain disorders.

Dr. Jonathan Ploski, assistant professor in the School of Behavioral and Brain Sciences, and his research team recently demonstrated that they could activate time-dependent gene editing in mice brain cells — a function that is triggered by feeding the animals a chemical called doxycycline.

“We are developing a method to make CRISPR/Cas9 inducible — in essence, creating a simplistic way to turn the genome editing function on at the appropriate time, similar to turning on a light switch,” Ploski said. “In our strategy, the CRISPR/Cas9 system is activated only after we add another drug to an animal’s food or through an injection.”

The CRISPR/Cas9 system is a molecular process that some bacteria use to fight off invading viruses. The bacteria use the defense mechanism as a sort of immune system, to snip out pieces of an invader’s DNA and keep it on hand to help them recognize the virus if it attacks again.

In recent years, scientists discovered that the CRISPR/Cas9 system can be exploited to make precise changes to the DNA of humans, as well as animals and plants. The hope is that the system might be used to correct errant genes that cause disease.

“CRISPR is a very quick and easy way to destroy a gene within cells,” Ploski said. “Essentially it's an enzyme or protein that binds the DNA and is designed to cut it.”

Ploski’s group recently published findings on its inducible CRISPR/Cas9 system online in the journal Frontiers in Molecular Neuroscience. The work was funded by the National Institutes of Health (NIH), the Texas Biomedical Device Center and UT Dallas. In addition to Ploski, authors of the paper included cognition and neuroscience doctoral student Christopher de Solis, recent graduate Dr. Roopashri Holehonnur PhD’16 and research assistant Anthony Ho.

Ploski also recently received an additional $420,750 grant from the NIH to further support his preclinical studies aimed at more precisely targeting gene editing in brain cells. The research will explore methods to localize the tool to specific subsets of cells within the brain.

“The idea is that we could deliver this toolkit via virus to a mouse’s brain, but it would only become activated in specific cell types using a process called CRE recombination, which is a widely used technique for manipulating genes,” Ploski said. “This delivery system increases the spatial specificity of this system which, due to the complexity of the brain, allows us to improve the precision by which we can target very specific cell types, which is always desirable.”

Ploski also wants to examine the fidelity of the genome editing functions, including whether the system will change the DNA at only the intended target site or whether it will impact DNA at other spots.

“There haven't been enough adequate studies looking at the fidelity of the CRISPR/Cas9 system over long-term use within the animal brain,” he said.

Dr. Tae Hoon Kim, associate professor in the Department of Biological Sciences, is working with Ploski to study the fidelity issue.

One of the major challenges in neuroscience is that the brain is incredibly complex, made up of many different cell types that function in different ways.

“Any tool that can increase our precision, targeting these cells accurately — either with respect to specific cell types or increased precision in terms of when these changes can be made to those cells — is huge,” he said. “We believe the tools that we have developed, and continue to develop, will increase the overall productivity of studying the molecular basis of brain function.”

As more is learned about the underlying biochemistry of the brain, research on various neuroscientific phenomena and pathologies will advance quickly, Ploski said.

“Learning and memory, PTSD, autism, and essentially all psychiatric disorders can be studied a little bit faster, a little easier because this tool enables genes to be manipulated faster than other techniques,” he said.