This technology has potential to create a demand for pathologists to do genetic analysis as a companion diagnostic in support of physicians treating patients with gene-editing proteins

Researchers at Harvard University have demonstrated a new method to deliver gene-editing proteins into cells. This breakthrough could eventually trigger a demand for pathologists to do genetic analysis as the companion diagnostic needed to help clinicians select appropriate gene-editing therapies for their patients.

Of course, it will be several years before such a scenario is feasible. The related example are the companion diagnostic tests that clinical laboratories perform to guide a physician’s decision on an appropriate therapeutic drug. Continued development of gene-editing therapies has the potential to increase the need for pathologists and medical laboratory scientists to do genetic analysis as a companion diagnostic for patients who would benefit from a gene-editing therapy.

The Harvard University researchers used commercially available cationic lipids to deliver genome-editing proteins into cells. The system works on living animals and humans, and the technology enables scientists to precisely and easily change DNA sequences at exact locations. The full study was outlined in an October Nature Biotechnology article.

Addressing the Root Cause of a Disease with Genome-editing Proteins

“Current drugs that treat genetic diseases cannot address the root cause of the disease,” stated study leader, David R. Liu, Ph.D., in a Science Daily news release. Liu is Professor of Chemistry and Chemical Biology at Harvard University. “[I]n the case of diseases that come from mutations in our own genes, one has to go into the cells and do surgery on our genomes to fix the root cause.”

The key to developing new therapeutics for genetic diseases often lies in developing systems to effectively deliver genome-editing proteins to the targeted area of the genome, according to the study authors. “[W]e David R. Liu, Ph.D now have genome-editing proteins that can do the surgery,” noted Liu. “But the challenge is that these proteins, like virtually all proteins, do not enter cells spontaneously.” Liu further stated that the new method very potently delivered genome-editing proteins directly into living cells.

David R. Liu, Ph.D

David R. Liu, Ph.D., Professor of Chemistry and Chemical Biology at Harvard University, has led a team of scientists in the development of a gene-editing protein delivery system that uses cationic lipids and works on animal and human cells. The new delivery method is as effective as protein delivery via DNA, and has significantly higher specificity. If developed, this technology could open the door to routine use of genome analysis, worked up by the clinical laboratory, as one element in therapeutic decision-making. (Photo copyright The Harvard Gazette.)

New Technology Builds on DNA Delivery Approach

Using conventional methods, researchers had already succeeded in intracellular delivery of DNA that encodes genome-editing proteins. But, that delivery system relied on the cells themselves to then actually produce the corresponding genome-editing proteins. What the Harvard team did was to deliver the genome-editing proteins themselves directly into cells.

Using the new system, the Liu team observed efficient genome modification not only in cultured cells, but also in living animals, according to a Harvard Gazette story.

In the new approach, the Harvard team used commercially available cationic lipids to introduce the genome-editing proteins directly into cells. Once in the cells, however, it is difficult to get the proteins released into the cell, Liu observed. “The efficiency with which a protein will spontaneously escape an endosome is very low—maybe as low as one-in-a-million under normal circumstances,” he stated in the Science Daily story.

Another component of the innovative approach taken in Liu’s lab was using super-negatively charged proteins. The Science Daily article noted that conventional methods use super-positively charged proteins. “The potency of delivering proteins that are associated with highly negatively charged molecules using cationic lipids is approximately 1,000 times greater than delivering proteins using positively charged proteins or peptides,” stated Liu.

Efficiency and Specificity Mark Harvard’s Improved Protein-delivery System

The experiment showed that the new direct protein-delivery approach was at least as efficient as the best results observed from the conventional DNA-delivery method, Science Daily reported. The real difference came in the measure of specificity—how accurately the targeted genes were modified versus off-target modifications. The specificity proved much higher with protein delivery than with DNA delivery.

“There has always been a mismatch between DNA delivery and the desired outcome of genome editing,” explained Liu in the Science Daily story. “Following DNA delivery, the encoded proteins can be expressed in difficult-to-regulate amounts for long periods of time.”

The mission in genome editing, however, is to restrict modification to only the one or two target copies of the gene. After that, further modification must be halted. “The only things it can do after [the targeted modifications] are undesired and possibly harmful.” According to Liu, the fact that direct protein delivery means transient and short-lived editing activity may make it a better match than DNA delivery for most genome-editing applications.

Harvard’s New Approach Holds Promise for Treatment of Genetic Diseases

Genome-editing proteins may usher in the next generation of therapies for numerous genetic disorders. That’s what Liu believes, according to Science Daily. The ability to directly modify genes in a living cell could eventually allow scientists to cure debilitating, hard to treat genetic diseases. These span such diseases as sickle-cell anemia, diseases of the liver, muscles, blood, eye and ear, and even deafness.

“We hope this approach to protein delivery will help connect where genome editing is now to where the field needs to be in order to realize the therapeutic potential of these proteins to address genetic diseases,” concluded Liu in the Science Daily story.

However, a number of challenges remain. The application of the new technology in human therapeutics is likely several years off, the Harvard Gazette reported. Even so, the day will likely come when doctors treat genetic disorders by administering drugs designed to alter the patients’ genomes, the article noted.

When this technology eventually moves into general clinical use, it will create the need for a companion diagnostic procedure where pathologists and medical laboratory scientists first analyze the DNA of patients specifically to guide physicians in their selection of the most appropriate gene-editing therapies for individual patients.

–Pamela Scherer McLeod

Related Information:

Toward Genetic Editing

Cationic Lipid-mediated Delivery of Proteins Enables Efficient Protein-based Genome Editing In Vitro and In Vivo

Improved Accuracy in Genome Editing

Genetically Modified Human? How Gene Editing Works

Genome Surgery

Development of Targeted Delivery Systems for Nucleic Acid Drugs

How Cationic Lipid Mediated Transfection Works

Breakthrough DNA Editing Tool May Help Pathologists Develop New Diagnostic Approaches to Identify and Treat the Underlying Causes of Diseases at the Genetic Level