In hands-on lab, undergrads learn basics of CRISPR gene-editing technique

BUFFALO, N.Y. — A lab course at the University at Buffalo is giving undergraduate biology students hands-on experience with CRISPR, a revolutionary gene-editing technique.

CRISPR allows scientists to disable or alter specific sections of DNA in cells of living organisms. The tool has been around for several years, but has recently gained prominence as technological advancements have shown how powerful it can be.

Experts say CRISPR could be used to genetically engineer crops, help identify genes that may contribute to disease, and improve antibiotics.

“It’s a really valuable tool to be able to edit specific genes,” says James O. Berry, PhD, professor of biological sciences in the UB College of Arts and Sciences, whose research focuses on plant genetics. “Students come in knowing about CRISPR. They’ve heard of it, they’re excited to learn about it. But they don’t actually know much about how it works, so we decided to come up with an introduction to CRISPR laboratory exercise.”

Berry designed the CRISPR lab with colleagues and taught it for the first time in 2017 as part of a broader, semester-long course on genetics for juniors and seniors.

The CRISPR unit is running again this fall. Students who take it use CRISPR to deactivate genes in baker’s yeast, causing colonies of the single-celled organism to turn pink or take on an abnormal shape. The lab is described in an October paper that UB biologists published in the journal Biochemistry and Molecular Biology Education.

“CRISPR is such a major gene-editing technique these days,” says Nitasha Sehgal, PhD, a lecturer in biological sciences who helps to teach the course. “It’s a cutting-edge technique, and we wanted our students to know how it works before they graduate. It will be helpful for them for their future careers, especially if they choose to do research in biology or medicine.”

“I personally learn better when I get to do things hands-on,” says Erin Hong, a senior in the class who is studying biological sciences and biomedical sciences at UB. “By doing all the steps, I get to know why each step is so important.”

New this year, students in the class are also being asked to consider societal implications of the technology.

CRISPR systems use a search-and-destroy technique to disable genes.

Scientists carry out the method by attaching a DNA-snipping protein called Cas9 to a molecule known as a guide RNA. The guide RNA acts as a homing system: It locates a precise section of DNA in a gene and leads the Cas9 protein there. Then, Cas9 slices the gene, breaking it.

To finish the job, a fragment of DNA that scientists synthesize in the lab pastes itself into the incision made by Cas9. This seals the cut in a way that ensures the damaged gene can’t be activated later on.

The same series of steps can be used not only to knock out targeted genes, but also to repair unwanted genetic mutations and edit DNA in other ways.

At UB, the CRISPR lab focuses on disabling genes in baker’s yeast, Saccharomyces cerevisiae.

Before the unit begins, M. Eileen Sylves, an instructional support technician, preps materials. She creates many copies of a plasmid — a circular strand of DNA — that programs cells to produce the Cas9 protein and guide RNA as a single complex. She also makes large amounts of the DNA fragment used to repair the Cas9 cuts.

Then, in a series of classes, students carefully mix the plasmid and DNA fragment with yeast cells; transfer the cells onto petri dishes; and observe the cells after they grow into colonies.

Students know if they’ve employed CRISPR successfully because they can literally see the results: Classmates who used CRISPR to break a gene called ADE2 see yeast colonies turn a bubblegum pink within days, while those who used CRISPR to deactivate a gene called STE12 see colonies take on an uncharacteristic shape a few weeks later.

CRISPR has made headlines as researchers have pondered its potential, including its dangers. The gene-editing tool could help scientists discover life-saving drugs or make agriculture more efficient, but it could also be used for controversial purposes, such as genetically engineering human embryos.

To encourage students to think about societal implications, Berry added an assignment to this year’s CRISPR unit. As part of their lab report, students must summarize how the gene-editing technology might affect one sector of society — whether it be medicine, agriculture, business or another field — and give arguments both in favor and against the use of CRISPR in that area.

Hong, who hopes to become a pediatrician, says she was happy to see societal concerns addressed as part of the course. She became interested in gene editing after shadowing a doctor who had a patient with a severe genetic disorder, and sees potential for CRISPR in treating genetic disease. At the same time, she says, society needs to consider the implications of the new technology.

“It’s definitely important to think about ethics, because science has such a huge impact on society,” Hong says. “I am excited to see the advantages that CRISPR can bring us in the medical field. However, I'm sure it will also raise a lot of ethical problems, such as questions about designer babies.”

Ewa Durda, a senior biological sciences major at UB who also hopes to pursue a career as a doctor, says it’s exciting to be able to learn about CRISPR in a hands-on lab as an undergraduate. She believes CRISPR raises ethical questions that society will need to debate, but also sees great promise in the technology.

“With CRISPR being a gene-editing mechanism, it especially holds promise for helping to prevent inheritable diseases from being passed down from generation to generation,” Durda says. Regarding CRISPR, she adds, “It's such an interesting and new mechanism. It’s definitely something that I will follow even past my genetics laboratory course at UB to see how far it will progress.”