Modifying the genetic makeup of an organism is the stuff of science fiction. It’s also what genome engineering is all about. And scientists are using it to study the effects of human mutations introduced in other species to develop new drugs.

There’s only one problem: the diseases don’t necessarily replicate.

This is what researchers at Duke University School of Medicine and Brigham and Women’s Hospital, Harvard Medical School are learning.

In a study published June 29 in the journal Nature, researchers compared thousands of human disease-causing mutations with the analogous sequences of some 100 animal species.

“We found many examples in which an entire species should have a serious genetic ailment, but instead were healthy,” said Nicholas Katsanis, PhD, director of the Center for Human Disease Modeling and professor cell biology and pediatrics at Duke.

“So, if we can understand how animals escape illness from such severe genetic mutations, we might have a way to make humans better.”

The researchers considered two possible explanations: Disease suppression might be the result of one or two additional substitutions on the same gene that buffer the harmful effect of the mutation; or suppression may be caused by numerous small substitutions throughout the genome that form an aggregate “shield.”

“Evolutionary theory told us that such a shield must exist, we just did not know how if would work,” Katsanis said. “Now we know at least part of the answer.”

The team tracked changes in protein sequence that travelled with the disease-causing mutation and were candidates for offering protection. If a species lost the “traveler,” it would also have to eliminate the mutation or become extinct. 

The researchers tested this notion using molecular tools to identify these sites. They first engineered mutant proteins that were defective, then added secondary sites and were able to completely restore protein function.

“In the end, it looks like you can shield mutations with a single change elsewhere in the same gene, creating a single champion,” Katsanis added.